JPS6285031A - Melt-spinning of pitch - Google Patents

Abstract

PURPOSE:Pitch is melted, degassed and extruded, as the heat history which the pitch undergoes is being controlled, at specific conditions, to obtain carbon fiber stably without yarn breakage and void formation. CONSTITUTION:At first pitch is melted and degassed usually by treating it with reduced pressure. Then, the pitch is extruded out of the nozzles as the heat history the pitch undergoes is being controlled so that the amount of gas formed by pyrolysis becomes less than 0.2ml per 1g of pitch. The spinning of the pitch is preferably effected using a vented extruder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a pitch melt spinning method. More specifically, the present invention relates to a pitch melt-spinning method in which yarn breakage and void generation due to foaming are improved.

[Prior Art] As a method for obtaining carbon fibers by melt spinning pitch, for example, the method described in JP-A-59-157309 is well known.

However, the pitch used in melt spinning causes reactions such as thermal decomposition and polycondensation when heated, so it foams during spinning. Mesophase pitch, which is used to obtain particularly high-strength and high-modulus carbon fibers, is usually spun at a spinning temperature of 300°C.
Since the temperature exceeds 'C, foaming due to the above reaction is likely to occur at the spinning temperature, which tends to cause problems during spinning.

Furthermore, pitch for spinning foams when melted during spinning due to organic gas components adsorbed and dissolved during pitch adjustment and inorganic gases such as carbon dioxide caused by water and surface oxides adsorbed during handling.

Bubbles generated for the above reasons may cause voids in the system or cause yarn breakage during spinning.

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to provide a pitch melt-spinning method that is free from problems caused by foaming.

[Means for Solving the Problems] The present invention is designed to reduce the heat that the pitch receives after it is degassed and before it is discharged, when the pitch is degassed after being melted and then the treated pitch is discharged from the die. This is Bituji's melt-spinning method, which is characterized in that the pyrolysis gas generation φ is 0.2 m+5 or more per 10 piddays.

Bubbles caused by gases, water, carbon dioxide, etc. (2) generated when melting pitch are removed by degassing the molten pitch. Degassing is usually done by treating the molten pitch under reduced pressure. For example,
It is possible to degas the molten bits by turning the storage tank into soil and degassing them, or by using a vent extruder, but it is important to keep the specific surface area as large as possible during the degassing process. is preferred.

However, as described above, pitch generates organic gases such as methane, methane, and chlorine due to reactions such as thermal decomposition and polycondensation as described above.After defoaming treatment, the pitch is removed from the spinning hole. The thermal history up to discharge is important. Reactions such as thermal decomposition and polycondensation are carried out as shown in Figure 1.
This becomes noticeable at temperatures above 370 DEG C., and as shown in FIG. 1, the temperature dependence of the amount of gas generated differs slightly depending on the type of pitch.

On the other hand, when performing melt spinning, thread cutting 1'1 due to foaming. ,
In order to avoid problems such as voids, 142 is
The amount of gas generated per 1g of pitch is 062m1.
After the degassing treatment, it is necessary to control the thermal history of the clay discharged from the discharge hole so that the yarn can be spun.

The amount of gas generated per gram of pitch is 1. After holding for 10 minutes, the atmosphere was replaced with nitrogen again, and the gases generated during melting were degassed, and then held at a specified temperature for a specified period of time, C1 to C3Q generated at that time.6 Measure the machine gas using gask L1 and find it using the total overlapping method.

As shown in Figure 1, the relationship between the gas-generating potato and the heat pump differs depending on the pitch, so the thermal history after degassing during spinning until the pitch starts to be discharged has a limit depending on the pitch used. need to be determined.

In the case of a so-called pot-type spinning machine, the molten pitch is stored and degassed by depressurizing the pitch surface, and then discharged from the spinneret while being discharged by a pump, etc., and spun. It is difficult to maintain the pressure balance when processing and discharging pitch at the same time, and if the depressurization treatment and discharging are carried out at the same time, the retention time of the pitch will not be constant, resulting in these problems. It is preferable to use vent type Ex 1 to Ruda.

Although the present invention can be used for any optically isotropic l-anisotropic pitch, the so-called meso-to-isotropic pitch of the optically anisotropic i-pitch can be used.
In the case of spun pitch, the spinning temperature is as high as 300° C. or higher, which can lead to foaming problems, so the present invention is highly effective.

The present invention will be explained in more detail by referring to examples.

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

After embedding the optically anisotropic sample in epoxy resin, it was polished by a conventional method. Polished surface with l-e'itz 0RTHOPLA
N: Observation was made using a reflective polarization method using a microscope. The presence structure of the optically anisotropic component was determined by calculating the area of the isotropic part and the anisotropic part when observed under polarized light as described above. .

The quinoline solution was carried out by a method that was a combination of the centrifugation method specified in JIS-2425 and the filtration method.

Place one piece of crushed gotsuji in a bowl and use a soft brush to remove the pitch powder from the aluminum bowl and place it at the point where it started melting. Determine the softening point from the temperature.

[Example] Coal tar d3 and Lutar pip were hydrogenated under the conditions shown in Table 1. Hydrogenated pitch was obtained by distilling at 350°C. Next, three types of mesonoaze pitches were obtained by heat treatment under the conditions shown in Table 1. The characteristics of the obtained pitches are shown in Table 2. After degassing treatment at a reduced pressure of 60 mmHg through a ruder, 0.2 doors, 100 tons (discharged from the nozzle, 450 m while giving various thermal histories shown in Table 4)
1 green pipe with a diameter of 14μ is picked up at a rate of 1
It's 1. The results are shown in Table 4. Further, the amount of pyrolysis gas generated was measured using the method described in the specification using the thermal history shown in Table 4 for the same pitch, and the results are also shown in Table 4. In both experiments N and 1.3.5, the pyrolysis gas generation port was 0. The pitch was 2 ml/g or less, indicating good spinnability. On the other hand, experiments N, 2.4, and 6°7 all had large thermal histories, and the amount of pyrolysis gas generated was 0.
Since the pitch exceeds 2 ml/g, there were problems such as yarn breakage due to bubbles during spinning and voids in the system.

Table 2 [Effects of the invention] The melt spinning method of the present invention can prevent yarn breakage and yarn voids due to foaming during pitch spinning, and can stably produce carbon fibers without causing carbon fiber strength formula (■). Obtainable.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the treatment temperature and the amount of pyrolysis gas generated when various pitches in Examples were heat-treated for 10 minutes. 2Eo '1lo5 12o 3
4t) h & 039° place hit i! IJI(℃
1 iI'11 Figure

Claims (1)

[Claims] After melting the pitch, degassing treatment is performed, and then when the treated pitch is discharged from the die, the thermal history that the pitch undergoes after degassing and before being discharged is determined by the amount of pyrolysis gas generated per 1 g of pitch. A method for melt spinning pitch, characterized in that the pitch is 2 ml or less.