JPH01282310A - Pitch yarn - Google Patents

Abstract

PURPOSE:To obtain a pitch yarn, consisting of a high polymer capable of forming liquid crystals oriented in the fiber axis direction and pitch component and capable of improving poor yarn-making properties, handleability and melt sticking in infusibilization. CONSTITUTION:A pitch yarn, obtained by blend or conjugate spinning of (A) a high polymer, such as wholly aromatic polyesters or polyester amides, capable of forming liquid crystals oriented in the fiber axis direction and (B) a pitch component, such as optically anisotropic pitch, and suitable as flame-resistant fibers, carbon fibers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pitch yarn suitable for producing flame-resistant fibers and carbon fibers.

[Prior art] The technology for producing 1 q of carbon fiber from pitch is known, for example, from the
It is well known from publications such as No. 3-4550 and Japanese Unexamined Patent Publication No. 19127-1983.

However, since the viscosity of pitch has extremely high temperature dependence, it is necessary to spin it in a low viscosity state with a melt viscosity of 100 to 30 Qpoise 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.

Generally speaking, since pitch yarn cannot be drawn like polymers, it is necessary to spin it to a low fineness of 5 to 15 microns. Furthermore, the strength and elongation characteristics of carbon fibers are dependent on the fiber diameter, and as long as the surface quality does not have an adverse effect, lower fineness results in higher strength.

However, it is generally difficult to make the pitch finer.
There has been a problem in that it is usually extremely difficult to spin fibers with a diameter of 10 μm or less, particularly 8 μm or less.

Furthermore, when melt-spinning optically anisotropic pitch, it is necessary to adopt a spinning temperature, a spinneret, and a flow path shape that enable industrially stable spinning. In that case, the spinning temperature should usually be lowered. In order to avoid foaming and achieve stable yarn spinning as described in No. 85031, it is preferable to make the diameter of the spinneret hole smaller and the hole length longer. There is a problem in that cracks occur and the physical properties deteriorate.

As a means of avoiding radial structures, increasing the spinning temperature results in the aforementioned foaming problem.

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, the oxidation reaction that makes pitch infusible is an exothermic reaction, so when yarn is made infusible in a bundled state such as a normal multifilament, sheet, or bobbin, local heat accumulation occurs. There is a problem in that adhesion and fusion of adjacent fibers are extremely likely to occur even if the temperature of the infusibility treatment is controlled. This adhesion and fusing of fibers causes surface defects and significantly reduces the physical properties of the yarn.

In other words, pitch yarn has disadvantages such as poor handling and easy adhesion/fusion during infusibility treatment, so the processing time is limited due to the upper limit on the yarn speed, yarn handling method, and heating rate during infusibility treatment. It is necessary to adopt the mildest possible conditions for all such matters. In other words, these problems have a major drawback in that they reduce productivity, flowability, carbon fiber physical properties, etc.

In addition, when producing 1 q of high-strength, high-modulus carbon fiber using an optically anisotropic pitch, the defects that occur during handling and infusibility are a major factor in the deterioration of physical properties, as well as deterioration during firing. The problem with the separation component is that the internal strain caused by contraction accompanying the formation of a structure due to the development of the carbon network surface tends to become a starting point for fracture, especially near 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. Since it does not have any properties or orientation during spinning, it has not been able to sufficiently improve the above-mentioned problems.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the problems that arise when producing flame-resistant fibers, carbon fibers, etc. by firing the pitch described above, such as poor spinning properties, poor handling properties, and infusibility. It is an object of the present invention to provide a pitch yarn which has improved problems such as fusion during heating and deterioration of the physical properties of the resulting fired yarn.

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

(1) A pitch yarn characterized by being composed of a liquid crystal-forming polymer compound oriented in the fiber axis direction and a pitch component.

In the present invention, the polymer compound that forms a liquid crystal refers to one that forms a liquid crystal alone or in a mixed system with a solvent, etc., and specifically includes wholly aromatic polyester, polyester amide, polyamide, polyimide, and There are cellulose-based polymer compounds.

When the polymer compound is spun together with pitch, it must exhibit a liquid crystal state and have orientation in the fiber axis direction, and it must be stable without causing any chemical changes at the spinning temperature. Further, those that form liquid crystal in a molten state are preferred in terms of handling properties, and liquid crystal polyesters and polyester amides are preferred, with fully aromatic polyesters and non-aromatic polyester amides being particularly preferred.

Regarding the compatibility between the polymer compound forming the liquid crystal and the pitch component, it is possible to use a range of compounds ranging from those with good compatibility to those with no compatibility depending on the purpose. Those with good compatibility are dispersed in the pitch component in a molecular state or in a state close to it, and when oriented in the 1 l axial direction in the pitch, they have a reinforcing effect on pitch yarns and infusible yarns, and also have a reinforcing effect with carbon fibers. When using an optically anisotropic pitch, it has a combined effect with the pitch component, and when an optically anisotropic pitch is used, it has an effect of preventing fiber cracking due to the radial structure.

The pitch yarn of the present invention is composed of a pitch component and a polymer compound that forms the above-mentioned liquid crystal oriented in the $l fiber axis direction.

The polymer compound can take various states, from existing in a molecular state in the pitch component in the cross section of the pitch yarn to a state in which the polymer component and the pitch component are combined while maintaining independent regions.

When the polymer compound maintains an independent region, the length of the polymer compound portion in the fiber axis direction is preferably 10 times or more the diameter of a circle equal to the cross-sectional area perpendicular to the fiber axis;
More preferably 0 times or more.

It is preferable that the polymer compound forming the liquid crystal has a tensile modulus higher than that of the pitch component, since this increases the reinforcing effect of the fragile pitch yarn.

In addition, when melt spinning is performed using optically anisotropic pitch as the pitch component, the spinning temperature is usually as high as 300°C or higher.
It is preferable to use a polymer compound with good heat resistance.

In the present invention, the pitch component refers to coal-based, petroleum-based, synthetic pitch based on naphthalene or polyvinyl chloride, including isotropic pitch, optically anisotropic pitch, mixtures thereof, and additives such as polymer compounds. Means added pitch.

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.

As a method for producing the pitch yarn of the present invention, a method of mixed spinning or composite spinning of the pitch component and a polymer compound that forms liquid crystal is employed.

Mixed spinning refers to a method in which the pitch component and the polymer compound are mixed in advance in a molten state or solution state, and then the mixture is spun, or a method in which each component is supplied separately for spinning and is mixed in a spinning machine while being spun. In the latter case, a method of actively kneading the two is adopted, and it is particularly preferable to use a static kneading device. In this case, it is preferable that the polymer compound component forming the liquid crystal be dispersed in a stripe shape in the m-off axis direction.If the ratio of the length to the diameter is too small, the reinforcing effect will be small. The diameter/diameter ratio is preferably 10 or more, more preferably 100 or more. In order to prevent the length of the streaks from becoming too small, the number of stages in the kneading equipment, the flow rate,
The viscosity etc. may be selected appropriately.

Further, the residence time from the time of dispersion in the static kneading device to the time of discharge from the nozzle and the shape of the flow path need to be within a range in which the dispersed streaks do not come together again.

In addition, in composite spinning, a method can be adopted in which the polymer compound component and the pitch component are supplied independently and the two are combined into a seabird type, parallel type, core-sheath type, etc. It is preferable to cover the pitch yarn or arrange it in a striped manner on the surface because it has a reinforcing effect on the pitch yarn. Further, it is preferable that the polymer compound is arranged in a striped manner inside the pitch yarn, since it is possible to strengthen the pitch yarn in terms of its tensile properties. It is also possible to supply a system in which a pitch component and a polymer compound are mixed during composite spinning.

Pitch yarn obtained by mixed spinning and/or composite spinning of the above-mentioned polymer compounds can improve process passability such as spinning properties, handling properties, and fusion during infusibility, as compared to cases in which pitch is spun alone. This has effects such as improving the physical properties of carbon fibers and preventing cracking when using an optical anisotropic pinch.

Although it is not clear why the polymer compound forming the liquid crystal of the present invention is oriented in the fiber axis direction to improve the physical properties of pitch yarn, infusible yarn made by firing the same, carbon fiber, etc.
The rigid and linear chains of the liquid crystal polymer are oriented in the fiber axis direction, which has the effect of reinforcing fibers against weak pitch yarns, and the fact that the center symmetry of the internal structure of carbon fibers after firing is disrupted. However, since it has the effect of alleviating internal stress and strain, it is thought that the influence of deterioration of physical properties due to internal defects can be reduced.

When melt-spinning the pitch component, the melt viscosity at the spinning temperature is 100 to 2000 poise, and the melt viscosity of the liquid crystal polymer is preferably 0.5 to 2 times the melt viscosity of the pitch component, preferably 0.75 It is more preferable to set it to 1°5 times.

After obtaining the pitch yarn of the present invention, it is made infusible, pre-carbonized if necessary, then carbonized, and further graphitized if necessary to obtain a pitch-based carbon fiber.

As a pitch spinning method, melt spinning is usually used, with the above-mentioned mixed spinning or composite spinning as essential, but dry spinning, wet spinning, dry-wetting spinning methods, etc. can also be used depending on the purpose. The pitch can be melt-spun using conventional pressure extrusion, centrifugal spinning, flash spinning, or the like.

In addition, the method of taking the pitch and collecting the yarn may include taking it with a roller, air zaraker, etc., winding it, stacking it on a tray or net, etc., as long as it does not apply a load that may cause yarn breakage to the fragile yarn. The usual method can be adopted.

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, for example, heating to 800 to 1700°C in an inert gas atmosphere or vacuum, and graphitization treatment includes heating at 170°C in an inert gas atmosphere, for example.
There is a method of heat treatment at 0°C or higher.

The present invention will be explained in detail below with reference to Examples.

In addition, the measurement method in the examples is based on the method shown below.

[Optical Anisotropy] After embedding the sample in epoxy resin, it was polished by a conventional method. Polished surface with Leitz 110RTtlOPLAN
Observations were made by reflection polarization using a microscope. The abundance of the optically anisotropic component was determined from the area ratio of the isotropic part and the anisotropic part when observed under the polarized light described above. Measurements were performed 10 times and expressed as an average value.

[Quinoline solution] This was carried out using a method combining the centrifugation method and r-filtration method specified in JIS-24 and 25.

[Measurement of strength and elongation] The method specified in J15-R-7601 was followed. The fiber diameter was measured using a scanning electron microscope at a portion adjacent to the strength/elongation measuring section. In addition, the area of the cleaved fiber was determined from a microscopic photograph of its cross section.

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 solid matter, and then distilled at 350°C to obtain hydrogenated pitch. Then, it was heat-treated at 520° C. and 17 mmHg for 7 minutes to obtain 1 q of mesophase pitch.

The obtained menphase pitch has a softening point of 235°C1QI
33%, BI 39%, and anisotropy 85%.

The polymer compound that forms liquid crystal is disclosed in Japanese Patent Application Laid-open No. 54-77691.
According to the publication No. 13485 and Japanese Patent Publication No. 61-13485,
Polymers shown in Table 1 were polymerized and used. The melt viscosity at 350'C is 3Qpoise for Polymer A and 9Qpoise for Polymer B.
It is 0pOiSe. As a comparative example, polyolefin oxide (P), which does not form liquid crystals, was used as a polymer compound.
PO) was used.

The mesophase pitch and the polymer compound were melt-mixed in a Nigu machine at 350'C to obtain a spinning raw material.

The mixing ratio was 7 for pitch and 3 for polymer.

The obtained mixed pitch was melted at 305°C, 160mC, and 16O using a vent extruder.
i After drilling, diameter is 0.2 mm at 340'C, hole length Q, 3 m
The yarn was discharged from a 100H nozzle of m and was taken up at a rate of 450 m/min to obtain a pitch yarn with a diameter of 10 μm. Just before paying,
A static crosstalk device was installed in the flow path.

The polymer compound was stable throughout melt mixing and spinning, and problems such as foaming due to decomposition did not occur. Furthermore, the spinning properties were more stable and good than when pitch was spun alone.

When the obtained pitch yarn was embedded in epoxy resin, polished, and observed under a reflective polarizing microscope, it was found that the polymer compound in the pitch yarn was oriented in the fiber axis direction in the form of fine stripes. Admitted.

Then, the obtained pitch yarn was heated at 50'C to 34°C in air.
The temperature was raised to 0''C at a rate of 0.5°C/min and held at 34.0°C for 15 minutes to infusible, yielding 1 q of infusible yarn.

Pitch yarn is easy to handle during spinning and infusibility processes.
It was better than pitch yarn obtained from pitch alone.

1 q of infusible yarn was fired in nitrogen at 1'500°C and 2500°C to obtain carbonized yarn and graphitized yarn.

Table 2 shows the physical properties of the obtained carbon fiber.

Experiments No. 2 and 3 in the inventive example are Experiment N in the comparative example.
Compared to o1.4, the strength of both pitch yarn and carbon fiber is improved.

Example 2 The mesophase pitch used in Example 1 was used as the sea component, and the polyarylate A was used as the island component. 20
A Takashima type pitch yarn was obtained by spinning at 0 m/min. The diameter of the pitch yarn was 12μ, and the diameter of the island component was 3μ.

The yarn spinning property was good, and the handling property of the obtained pitch yarn was also good. Pitch yarn strength is 61<g/m...2,
The infusible yarn strength was 6 k(]/mm2, which was better than Experiment No. 1 of Example 1 in which no polymer compound was used.

Furthermore, as a result of infusibility and firing in the same manner as in Example 1, the carbonized yarn strength was 2"l Okc+/mm2, and the elastic modulus was 15tO.
n/mm2, graphitized yarn strength 300 kg/mm2.5
Similarly, better results than Experiment No. 1 were obtained at 5 ton/mm2.

Note that when PPO was used as the island component, stable yarn spinning could not be performed.

[Effects of the Invention] The pitch yarn of the present invention is composed of a pitch component and a polymer compound that forms liquid crystals oriented in the fiber axis direction, so this pitch yarn can be fired to produce flame-resistant fibers, carbon fibers, etc. It is possible to improve problems such as poor spinning properties, poor handling properties, fusion during infusibility, and deterioration of physical properties of fired threads during production.

Claims (1)

[Claims] (1) A pitch yarn characterized in that it is composed of a polymer compound forming a liquid crystal oriented in the fiber axis direction and a pitch component.