JPH01282312A - Pitch fiber and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having improved reeling and handling properties by conjugately spinning a macromolecular compound with a constant carbonization yield or a mixture of a pitch and another macromolecular compound and a pitch or a mixture of a macromolecular compound and a pitch. CONSTITUTION:(A) (i) A macromolecular compound with >=5% carbonization yield such as polyacrylonitrile or polyphenylene sulfide or (ii) a mixture of a pitch such as coal-based or petroleum-based pitch and another macromolecular compound and (B) (iii) a pitch or (iV) a mixture of a macromolecular compound and a pitch are conjugately spun to provide the objective pitch fiber having a seath and core conjugate structure. In addition, the above mentioned conjugate spinning is preferably carried out using a static kneader.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pitch fiber and a method for producing the same.

[Prior art] The technology for obtaining carbon fiber from pitch is, for example, disclosed in Japanese Patent Publication No. 1973-
It is well known from publications such as No. 4550 and Japanese Unexamined Patent Publication No. 49-19127.

However, since the viscosity of pitch has extremely high temperature dependence, it is necessary to spin the pitch in a low viscosity state with a melt viscosity of 100 to 300 poise during spinning, unlike ordinary polymer compounds. Therefore, after being discharged from the nozzle,
Since the yarn is rapidly thinned, even if the temperature of the spinning atmosphere is sufficiently controlled, it is greatly affected by viscosity fluctuations of pitch, which is the spinning raw material, and yarn breakage is extremely likely to occur.

Furthermore, since the pitch yarn has the low viscosity mentioned above and is fragile, it must be spun at a relatively low speed, and pitch yarn cannot be drawn like polymers, so it is necessary to spin it to a low fineness of 5 to 15μ. For this reason, the discharge amount is small, and the spinneret back pressure is extremely low compared to normal polymer spinning. Therefore, if there is a highly viscous foreign substance, the nozzle will easily become clogged.

Conventionally, in order to prevent the above-mentioned viscosity unevenness and nozzle clogging, solid content and high viscosity content in petroleum-based and coal-based heavy oils, which are crude raw materials, have been removed.

However, pitch used as a spinning raw material has a higher viscosity than pitch for spinning, which is produced due to heat treatments such as distillation and mesophase formation after the solid content is removed, and changes over time such as oxidation. It was always accompanied by the formation of foreign substances with a certain sexiness.

Therefore, it has not been possible to avoid yarn breakage and nozzle clogging due to the foreign matter during melting.

Roughly speaking, the strength and elongation characteristics of carbon fibers depend on the fiber diameter, and as long as surface defects do not adversely affect the strength, the lower the 24 degrees, the higher the strength. The problem is that it is extremely difficult to spin fibers with a diameter of usually 10 μm or less, especially 8 μm or less.

In addition, when melt-spinning optically anisotropic pitch, it is necessary to adopt a spinning temperature, spinneret, and flow path shape that enable industrially stable spinning. In that case, it is usually preferable to keep the spinning temperature as low as possible to avoid the foaming described in JP-A No. 62-85031, and to make the diameter of the spinneret hole smaller and the hole length longer to ensure stable yarn production. In that case, since the shear applied to the pitch becomes large, there is a problem that the carbon fiber has a radial structure and cranks occur, resulting in poor physical properties.

If the spinning temperature is increased as a means to avoid the radial structure, the above-mentioned foaming problem will occur.

Furthermore, pitch yarn has extremely low strength and elongation, and is brittle, so it has poor handling properties and is prone to surface defects during handling, resulting in decreased productivity.
This is a factor that reduces the strength and elongation properties of carbon fibers after firing.

Furthermore, pitch yarn needs to be infusible before firing;
Like the pitch yarn, the infusible yarn is extremely fragile and has poor handling properties. Furthermore, when heating with an oxidizing gas to make it infusible, the rate of the infusibility reaction at low temperatures is extremely slow, so a method is usually used in which the reaction is carried out while increasing the temperature as the infusibility progresses. . At this time, it is necessary to raise the temperature within a range that does not exceed the increase in the softening point accompanying the progress of the infusibility reaction.

The oxidation reaction that occurs during the infusibility reaction of pitch is an exothermic reaction, so when yarn is infusible in a bundled state such as a normal multifilament, sheet, or bobbin, local heat accumulation occurs and the infusibility treatment is delayed. Even if temperature control is performed, adhesion and fusion of adjacent fibers is extremely likely to occur.

This adhesion and fusing of fibers causes surface defects and significantly reduces the physical properties of the yarn.

In addition, on the surface of the pitch yarn, there are light components, tar, dust, etc. that adhered during spinning, and especially when a sizing agent is used, the chemical and physical effects of these substances may cause the adhesion and fusion. This problem can easily occur.

Due to the above-mentioned properties, the infusibility reaction of pitch starts extremely slowly, even though the reaction rate is faster at higher temperatures, and it is necessary to complete the infusibility through a temperature raising process.

In other words, pitch yarn has the drawbacks of poor handling and easy adhesion/fusion during infusibility treatment, so there is an upper limit to the yarn speed, yarn handling method, and heating rate during infusibility treatment. It is necessary to adopt conditions as mild as possible for all of the above, and in other words, these problems have a major drawback in that they reduce productivity, economic efficiency, carbon fiber physical properties, etc.

In addition, when obtaining carbon fibers with high strength and high elastic modulus using optically anisotropic pitch, defects occurring during handling and infusibility are a major factor in deteriorating physical properties, and
The handling of eliminated components during firing has the problem that internal strain caused by shrinkage accompanying the formation of a structure due to the development of a carbon network surface tends to become a starting point for fracture, especially in the vicinity of the surface.

In addition, in order to improve the above-mentioned problems, a method of blending a polymer compound into the pitch and spinning it into yarn is being considered, but in the conventional method, the polymer compound exists randomly in the fiber, so it is not enough. No effect has been obtained.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a pitch yarn with improved spinning properties, handling properties, infusibility productivity, and physical properties of the resulting carbon fibers.

[Means to solve the problem] The present invention has the following configuration.

(1) A polymer compound with a carbonization yield of 5% or more,
A pitch fiber characterized in that a pitch component constitutes a core-sheath composite structure.

(2) The pitch-based pA fiber according to claim 1, wherein the core-sheath composite structure has a sea-island shape.

(3) A polymer compound with a carbonization yield of 5% or more (a
) or a method for producing pitch fibers, which comprises performing composite spinning using a mixture of pitch and a polymer compound (b) as component A and pitch (c) or a mixture of a polymer compound and pitch (d) as component B. .

(4) The method for producing pitch-based fibers according to claim 3, wherein the composite spinning is performed using a static kneading device.

The present invention will be explained in detail below.

In the pitch fiber of the present invention, one A component is a polymer compound or a pitch component that is necessary for the carbonization yield to be 5% or more,
It is obtained by composite spinning into a core-sheath shape using the pitch component as a different B component.

The composite state referred to in the present invention includes, for example, various core-sheath forms shown in FIGS. 1 to 3, and sea-island forms consisting of multiple island components shown in FIGS. 4 to 5. A radial shape as shown in FIG. 6, a modified core-sheath shape as shown in FIG. 7, etc. may be adopted.

Note that the core or island is completely continuous in the fiber axis direction,
Alternatively, it includes those dispersed in a substantially continuous stripe shape, although not completely continuous.

The pitch component used in the present invention is a coal-based, petroleum-based, synthetic pitch based on naphthalene or polyvinyl chloride,
This refers to isotropic pitch, optically anisotropic pitch, mixtures thereof, and pitch to which additives such as polymer compounds are added.

The optically anisotropic pitch can be within a range that provides orientation of the liquid crystal component during spinning. The amount of the optically anisotropic component is preferably 60% or more, more preferably 80% or more, from the viewpoint of the physical properties and spinning properties of the carbon fiber obtained.

The carbonization yield of the above-mentioned pitch component must also be 5% or more, but from an economic standpoint, a higher carbonization yield is preferable;
It is preferable to use a pitch component with a carbonization yield of 0% or more, more preferably 60% or more.

A carbonization yield of 5% or more means that 5% or more of carbonized products remain after normal carbonization treatment. In addition, polymer compounds with a carbonization yield of 5% or more can be obtained by various methods such as directly carbonizing the polymer compound, or carbonizing it after undergoing infusibility treatment such as oxidation treatment or crosslinking treatment, or flameproofing treatment. It means a polymer compound with a carbonization yield of 5% or more when carbonized. Examples of the polymer compound include polyacrylonitrile, phenol resin, polyphenylene sulfide, furan resin, and the like.

On the other hand, when it is desired to form a thin layer of carbon on the surface, it is difficult to form a thin layer by spinning, so it is preferable to use a polymer compound or pitch component with a low carbonization yield. This method is particularly effective when it is desired to obtain carbon fibers in which the ratio of the surface layer portion is 5% or less, especially 3% or less of the resulting carbon fibers.

The ratio of core-sheath sea-islands can be designed depending on the purpose, but it needs to be designed in consideration of the yield after carbonization.

Cross-linking, different from pitch, makes the polymer compound component infusible.
By performing heat curing or other means, the infusible polymer component has a reinforcing effect, a surface protection effect, etc. Also,
It is also possible to shorten the infusibility time.

A method has also been proposed in which an amorphous carbon layer is formed in a core-sheath shape on the surface after producing carbon fibers, but the process is complicated and costs increase compared to the method of the present invention in which the amorphous carbon layer is formed during spinning. It is inferior to the present invention in that the surface layer formed is not uniform and easily peels off.

Alternatively, the core-sheath-like seabird-shaped island component or the stripe-like dispersed stripe component can be made into fine carbon fibers with a fineness of 10 μm or less, which is difficult to achieve by ordinary spinning, so the obtained carbon fibers become fiber-reinforced carbon fibers. In particular, the effect is remarkable when anisotropic pitch is used for the island component or streak component.

When expecting the above-mentioned surface protection and reinforcing effects from the polymer component and isotropic carbon, the carbonization yield of the polymer component is generally low and isotropic carbon is produced, but the ratio of isotropic carbon is The lower the ratio, the more advantageous it is to obtain high-strength, high-modulus carbon fibers, and the composite ratio of polymer compounds and isotropic pitch is 50%.
It is preferably at most 30%, more preferably at most 30%. Further, if the composite ratio of the above components is too low, spinning becomes difficult, so it is preferably 1% or more, more preferably 5% or more, and most preferably 10% or more.

Furthermore, if the ratio of the length to the diameter of the component dispersed in a stripe shape is too small, no reinforcing effect will be obtained, so the length/diameter ratio is preferably 100 or more, more preferably 300 or more. In order to prevent the length of the streaks from being too short, the number of stages, quantity, viscosity, etc. of the kneading device may be appropriately selected.

As a pitch spinning method, melt spinning is usually used, but depending on the purpose, dry spinning, wet spinning, dry-wetting spinning, and other spinning methods can also be used.

As for the base, a conventional concentric composite type or an eccentric composite type can be used, and a multilayer composite type can also be used depending on the purpose.

In addition, for dispersing in the form of streaks, a conventional static kneading device is most preferable in terms of uniformity of dispersion, ease of handling, and productivity. In addition, the residence time after dispersion until discharge from the nozzle and the shape of the flow path need to be within a range where the dispersed streaks do not come together again.

For melt spinning the pitch, ordinary pressure extrusion, centrifugal spinning, flash spinning, etc. can be employed.

In addition, the method of taking the pitch and gathering the yarn is to take it with rollers, air suckers, etc., wind it up, and stack it on a tray or net, as long as it does not apply a load that may cause breakage to the fragile yarn. Ordinary methods such as

The infusibility treatment is carried out, for example, in the presence of oxygen, usually in air.
A method of oxidizing at 50 to 420'C can be applied. It is also possible to use oxidizing gases such as ozone, nitrogen oxide, and sulfur oxide as oxygen, or to use oxidizing liquids such as nitric acid, hydrogen peroxide, and potassium permanganate. Physical means such as electron beam crosslinking may also be used.

Carbonization treatment includes heating to 800 to 1700'C in an inert gas atmosphere or vacuum, and graphitization treatment includes, for example, heating at 800 to 1700'C in an inert gas atmosphere.
There is a method of heat treatment above 00'C.

[Example Example 1 Hydrogen gas was blown into coal tar in the presence of a nickel-molybdenum catalyst, and the mixture was reacted at 400°C for 120 minutes. The obtained hydrogenated tar was filtered through a 1μ filter to remove solids, and then distilled at 350°C to yield 1q of hydrogenated pitch. Then, it was heat treated at 520'C117mmh for 7 minutes to obtain mesophase pitch. The obtained mesophase pitch had a softening point of 235° C., 0.133%, BI of 39%, and anisotropy of 85%.

The obtained pitch was used as the core component, polyphenylene sulfide was used as the sheath component, and the core was 80% and the sheath 20%.
n Te composite spinning.

When spinning with an IOH spindle using only pitch, the pitch yarn was fragile and easily broke, so it could hardly be handled as a continuous yarn, but the pitch yarn of this example
Handling was possible, and the reinforcing effect of the polymer was observed.

The obtained pitch yarn was treated in a 5.3% aqueous solution of sodium hypozincate at 90° C. for 5.5 hours to infusible the polyphenylene sulfide.

Then, 5°C/5°C in air from 50'C to 340'C.
The temperature was raised to 340'C for 15 minutes to infusible the pitch, and an infusible yarn was obtained.

The obtained infusible thread was heated at 1500'C and 25°C in nitrogen.
It was fired at 00'C to obtain carbonized yarn and graphitized yarn.

The obtained carbonized yarn has a strength of 250 kmMmm2 and an elastic modulus of 1
5 ton/min, graphitized yarn has a strength of 330 kmm
m2 and elastic modulus of 55 ton/min, showing good physical properties.

In addition, no cracks occurred during infusibility or firing.

Example 2 The mesophase pitch obtained in Example 1 was used as the island component of 6 islands, the sea component was made of phenolic resin, and the IO
Composite spinning was carried out at 330'C and 20Qm/min using a H nozzle. The obtained conjugate fiber had a diameter of 14 μm, and the diameter of the island component was 5 μm.

When spinning with a 10H spindle using only pitch, the pitch yarn was fragile and easily broke, and could hardly be handled as a continuous yarn. However, the pitch yarn of this example
Handling was possible, and the reinforcing effect of the N polymer was observed.

The obtained pitch yarn was treated in formalin at 25°C for 30 hours to infusible the phenolic resin.

Then, 5°C/mi from 50'C to 340°C in air.
The pitch component was infusible by raising the humidity at 340° C. for 15 minutes to obtain an infusible yarn.

The obtained infusible yarn was heated at 1500°C and 250°C in nitrogen.
It was fired at 0'C to obtain carbonized yarn and graphitized yarn.

The obtained carbonized yarn has a strength of 260 kmMmm2 and an elastic modulus of 1
7 ton/mm2, graphitized yarn has a strength of 350ka/
mm2 and elastic modulus of 60 ton/mm2, showing good physical properties.

In addition, no cracks occurred during infusibility or firing.

Example 3 Instead of the polyphenylene sulfide of Example 1, a mixture of 92% ultra-high molecular weight polyethylene with a large molecular weight and 8% of the pitch of Example 1 was used to obtain a composite fiber in the same manner as in Example 1. The obtained pitch yarn was irradiated with an electron beam of 10 megarads to crosslink and infusible the polyethylene.

Then in air from 50'C to 340'C 10'C/
The temperature was raised at 340'C for 15 minutes to oxidize the pitch component and make it infusible, and then fired and carbonized in the same manner as in Example 1 to obtain a graphitized yarn. Each strength: 250 kcI/mm2, elastic modulus: 15 ton/mm2, strength: 330 kc+/m
m2 and elastic modulus of 55 ton/mm2, showing good physical properties.

In addition, the electron beam treatment was able to make the yarn infusible in a short period of time with good productivity, and the pitch yarn had good handling properties.

Example 4 The pitch obtained in Example 1 was pulverized and mixed at a ratio of 95% and polyphenylene sulfide at a ratio of 5%, and the mixture was supplied to a 10-stage static kneading device (manufactured by Toshii Engineering Co., Ltd.), and polyphenylene sulfide was mixed in the pitch. was dispersed in a uniform stripe shape.A hole with a diameter of 0.2 mm and a hole length of Q was provided downstream of the kneading device.
, 330℃, 600m/m from 3mm 100H base
111 TE was spun to obtain a pitch yarn with a diameter of 11 μm.

Table 1 shows the results of comparing the strength of the obtained pitch yarn, a single pitch yarn, and a yarn prepared by grinding and mixing pitch and polymer and spinning without using a static kneading device.

In addition, the strength of yarns that did not use a static kneading device varied greatly, and a uniform reinforcing effect could not be obtained.

Then, 0°5°C from 50'C to 340°C in air.
The temperature was raised at 340'C/min for 15 minutes to infusible, and an infusible thread was obtained.

The obtained infusible thread was heated at 1500'C and 25°C in nitrogen.
It was fired at 00°C to obtain carbonized thread and graphitized thread.

The results of strength and elastic modulus are shown in Table 1.

Table 1 Effect of the Invention 1 The surface of the pitch fiber of the present invention is covered with a polymer compound, thereby protecting the fragile pitch and improving handling properties during spinning, infusibility, and firing.

Furthermore, by adding a polymer compound to the core, pitch fibers with extremely low elongation can be reinforced, and the above-mentioned handling properties can be expected to be improved.

When the pitch fiber of the present invention is carbonized to obtain carbon fiber, cracks do not occur because of the composite structure of a core-sheath and sea-island structure. When an isotropic substance such as isotropic pitch or a polymer compound component is used for the sheath component and an anisotropic pitch component is used for the island component, the surface becomes isotropic carbon and is less susceptible to surface defects. , high strength,
Carbon fibers with high elastic modulus are obtained.

[Brief explanation of the drawing]

1 to 7 are model cross-sectional views showing one example of the pitch fiber according to the invention. Patent applicant Toshi Co., Ltd. No. 112
2nd I2I 3rd I2I
4I121 Figure 5
Figure 6 Figure 7

Claims (4)

[Claims] (1) A pitch fiber characterized in that a polymer compound having a carbonization yield of 5% or more and a pitch component constitute a core-sheath composite structure. (2) The pitch-based fiber according to claim 1, wherein the core-sheath composite structure has a sea-island shape. (3) The polymer compound (a) or the mixture of pitch and polymer compound (b) having a carbonization yield of 5% or more is used as the component A, and the pitch (c) or the mixture of polymer compound and pitch (d ) as component B and performs composite spinning. (4) The method for producing pitch fibers according to claim 3, wherein the composite spinning is performed using a static kneading device.