JPH01282317A - Spinning of mesophase pitch - Google Patents

Abstract

PURPOSE:To prevent occurrence of crack and simultaneously obtain a carbon fiber without reducing the elastic modulus by melt spinning a mesophase pitch while controlling the apparent viscosity and the draft thereof within a specified range. CONSTITUTION:A mesophase pitch consisting of a coal-based, petroleum-based pitch, etc., is melt spun while controlling the apparent viscosity eta and the draft d within a range of 50<=eta<=500 and 370<=d<=1200 at a nozzle discharging part. The melt-spun yarn is then subjected to infusibilization, carbonization and graphitization treatment to prevent occurrence of crack.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for spinning mesophase pitch.

[Prior Art] When mesophase pitch is melt-spun and liquid crystal is oriented in the fiber axis direction, the orientation structure changes depending on the viscosity of the pitch in the spinneret hole, the shearing force applied to the pitch, etc.
For example, JP-A-59-53717, JP-A-59-168
No. 124, JP-A-59-168125, JP-A-59-
It is publicly known from, for example, No. 168127. It is also known from JP-A-62-104926 to control the internal structure by controlling the relationship between the apparent viscosity and the pitch domain diameter.

However, although both methods can control the occurrence of cracks through structural control, they cannot simultaneously control the elastic modulus of carbon fibers. Roughly speaking, the domain diameter of menphase pitch becomes finer when subjected to shearing, and becomes larger when relaxed. The domain diameter during passage has no correlation with the domain diameter of the raw material pitch input into the spinning machine.

[Problem to be Solved by the Invention 1] The purpose of the present invention is to solve the problems of the prior art described above, to prevent the occurrence of cracks in the melt spinning of Metsney's pitch, and to prevent the decrease in the elastic modulus of the obtained carbon fiber. Another object of the present invention is to provide a method for melt-spinning mesophase pitch that also prevents the occurrence of oxidation.

[Means for Solving the Problems] The present invention provides a method for spinning mesophase pitch, characterized in that mesophase pitch is melt-spun in a nozzle discharge hole while satisfying the following conditions.

Melt viscosity η (poise) 50≦η≦500 Draft d370≦d≦1200.

The apparent viscosity in melt spinning is η (pOiSe), and the draft d is determined as follows.

η-9,8X105πD4 P/128QLd-πVD
2/240Q D double hole diameter (mm) L: Mouth hole length (mm) P: Discharge pressure (k (1/Cm2)) Q: Discharge ffi (cc/sec) V: Take-up speed (m/min > apparent The factors that change the viscosity include pitch type, spinning temperature, spinneret hole diameter, spinneret hole length, discharge amount, and discharge pressure.The factors that change the draft include the spinneret hole diameter,
There is a discharge amount and take-up speed.

When the draft and apparent viscosity of the resulting carbon fibers were investigated for various pitches such as coal-based and petroleum-based pitches, the elastic modulus with respect to the apparent viscosity was investigated, and the relationships shown in FIGS. 1 and 2 were obtained.

As a result, when the apparent viscosity η exceeds 500 poise, the elastic modulus suddenly decreases, and the elastic modulus of the graphitized system becomes 40 poise.
It is not preferable because it becomes less than ton/ml12. Desirably, 300t) oise or less is more preferable.

Moreover, if the apparent viscosity is less than 5Qpoise, yarn spinning becomes unstable and yarn breakage occurs frequently. Preferably 60 go
r se or more is more preferable.

On the other hand, if the draft d is low and less than 370, cracks will occur in the graphitized system and the strength will be low. Desirably, 400 or more is more preferable.

Furthermore, if the draft is too high and exceeds 1200, the modulus of elasticity will be less than 40 ton/mm2, which is not preferable. Desirably, it is more preferably 1000 or less.

The pitch component used in the present invention is an optically anisotropic coal-based, petroleum-based, synthetic pitch made from naphthalene or polyvinyl chloride, and mixtures of these or pitches containing additives such as polymer compounds are also included. means.

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.

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

In addition, the pitch collection method and collection method should be such that the fragile yarn is not subjected to any load that may cause yarn breakage, such as taking it up with rollers, air suckers, etc., winding it, i-lay, or putting it on the net. Ordinary methods such as lamination can be used.

For example, a method of oxidizing the pitch yarn in the presence of oxygen at 250 to 420°C in normal air 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. Depending on the case, physical means such as electron beam crosslinking may also be used.

Carbonization treatment of the infusible yarn includes heating to 800 to 1700°C in an inert gas atmosphere or vacuum, and graphitization treatment includes, for example, heating treatment at 1700°C or higher in an inert gas atmosphere. There is a way to do it.

[Examples] Example 1 Hydrogen gas was blown into coal tar and left unreacted at 450'C for 120 minutes. The obtained hydrogenated tar was filtered through a 1μ filter to remove solid matter, and then heated at 350°C to obtain hydrogenated pitch. Then 7 at 505°C and 17mmHg.
A heat treatment was performed for a minute to obtain mesophase pitch. The obtained mesophase pitch had a softening point of 265°C, a QI of 22%, and a BI of 9.
2%, and the anisotropy was 90%.

Using the 1q mesophase pitch, various pitch yarns were obtained by changing the spinning temperature, spinneret hole diameter, and spinning speed.

Then, O95° from 50°C to 300°C in air.
The humidity was increased at a rate of C/min, and the mixture was infusible by being held at 300'C for 15 minutes to obtain an infusible thread.

The obtained infusible yarn was fired at 2500'C in nitrogen to obtain a graphitized yarn.

Table 1 shows the physical properties of the graphitized yarn obtained.

In Experiments Nos. 1, 8, '9.11 to 13, the viscosity was apparently too high or the draft was too large, so the elastic modulus of the graphitized yarn was low at less than 40 ton/mm2.

In experiments No. 2, 7, and 10, graphitized yarns with high elastic modulus were obtained.

Example 2 Petroleum-based mesophase pitch, softening point 250'C1013
7%, Tl 79%, anisotropy '100%, pore diameter Q, 3 mm
The pitch yarns obtained by changing the temperature and spinning speed were made infusible and graphitized in the same manner as in Example 1 using a spinneret with hole length Q of 3 mm. The results are shown in Table 2. Actual profit No. 15-17, 21.
22 has an apparent viscosity and a large trough I~, so the elastic modulus is 4
Low Q ton/mm2 or less.

Experiment No. 9, 20. In 24 to 26, 1 q of high elastic modulus graphitized yarn was used.

In Experiment No. 14, 18.23, cracks occurred due to the low draft.

[Effect of the invention 1] By controlling the apparent viscosity and draft during melt spinning of mesophase pitch, no cracks occur,
1q of carbon fibers with no reduction in elastic modulus can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between draft and elastic modulus, and FIG. 2 is a diagram showing the relationship between apparent viscosity and elastic modulus. Patent applicant Toshi Co., Ltd. Construction drawing 2

Claims (1)

[Claims] (1) A method for spinning mesophase pitch, which comprises melt-spinning mesophase pitch in a nozzle discharge hole while satisfying the following conditions. Apparent melt viscosity η (poise) 50≦η≦500 Draft d370≦d≦1200