DE2124636B2 - Process for the production of carbon fibers - Google Patents

Description

,- Example 1

A high-temperature coal tar pitch with the following characteristics was used:

JU

The present invention relates to a method for producing carbon fibers from coal tar pitch or other strongly aromatic distillation residues.

Carbon fibers with excellent mechanical properties due to oxidation are already available and thermal conversion of filaments of organic polymers such as polyacrylonitrile and Rayon, preserved. Due to the cost of the raw materials and the low carbon yield however, the fibers obtained in this way have a high cost price. One also has fibers out Coal tar pitch obtained by subjecting the tar pitch to a thermal treatment at moderate Temperature and, if necessary, subjected to other treatments or conditioning and then the tar pitch treated in this way is spun into threads at a temperature of the order of 300 ° C Has. The threads thus obtained were subjected to oxidation to render them infusible and then charred in the air (see e.g. FR-PS 1465 030). However, these processes produce fibers of a quality that of the fibers obtained from textile thread is very inferior.

The present invention now includes a method that allows the qualities of a Coal tar pitch or a strongly aromatic substance similar to coal tar pitch Improve fibers.

According to the process of the invention, these highly aromatic tar pitches are used during or before the thermal treatment phase preceding the spinning, a polymeric hydrocarbon to. Among the polymers that have shown good results can be natural or synthetic Hydrocarbon polymers such as polyethylene, polypropylene, polystyrene, polybicyclo [2.2.1] hepten-2, name the types of rubber, etc. sen:

Kraemer-Sarnow point 80 ° C density 1.32 g / cm ' volatile components (according to the ATIC-02-60 standard) 64.3% Elemental analysis in% by weight carbon 93.02 hydrogen 4.45 oxygen 1.5 nitrogen 0.7 sulfur 0.3

This tar pitch was previously at 190 ° C through a bronze filter with an average pore opening of 2 μ has been filtered to separate the naturally contained solid and pseudo-solid particles.

After adding 10% by weight of high-density polyethylene with a melt index of 4, this mixture became brought to 420 ° C. with constant stirring at a heating rate of 3 ° C. per minute; the Volatiles released were removed with a stream of nitrogen discharged with a throughput of 3 l / min.

The product obtained was at 204 ° C with a Pulling speed of 450 m / min drawn into a thread.

The whole thing was in an oven and was subjected to the following working conditions:

from room temperature to 250 ° C in

Presence of air at 0.5 ° C / min 7.5 h

from 250 ° to 700 ° C in the presence

of nitrogen without oxygen

0.5 ° C / min 15 h

from 700 ° to 1000 ° C at 2 ° C / min 2.5 h

a total of 25 h

The oven is then allowed to cool naturally.

The mechanical properties of the obtained carbon fibers were measured using an Instrom tester measured under the following conditions

Length of the specimen
Pull speed

50 mm
0.05 cm / min

Example 3

An average tensile strength of 55 kg / mm ² and an average Young's modulus of 4200 kg / mm ^{2 were} measured for an average diameter of 30 μ.

These values are mean values from seven measurements on different threads. The overall yield of the including filtration, devolatilization, spinning, oxidation and char Operations was 65%.

Example 2

The working conditions were identical to those from Example 1, only the polyethylene was replaced by PcIybicyclo [2.2.1] -hepten-2 replaced (F. W. Michelotti and W. P. Keaveney, J. Polymer Sci., A, 3, [1965], 895).

The carbon fibers thus produced had a tensile strength of 150 kg / mm ² and a Young's modulus of 11960 kg / mm ² for a diameter of 30 μ.

The overall yield from the operations mentioned in Example 1 was 66%.

The working conditions were identical to those in Example 1, only the polyethylene was replaced by polystyrene replaced.

The carbon fibers thus produced had a tensile strength of 60 kg / mm ² and a Young's modulus of 4600 kg / mm ² for a diameter of 30 μ.

ίο The overall yield of that described in Example 1 Operations was 64%.

Example 4

The working conditions were identical to those in Example 1, but here the tar pitch did not contain any Additive.

The carbon fibers thus produced had a tensile strength of 24 kg / mm ² and a Young's modulus of 3300 kg / mm ² for a diameter of 30 μ.

The overall yield as described in Example 1 operations performed was 61%.

The comparison of the above properties with those of the invention, as in Examples 1 to 3 obtained fibers shows clear advantages of the invention.

Claims (3)

Patent claims: 1. Process for the production of carbon fibers from a strongly aromatic distillation residue, such as coal tar pitch, whereby the distillation residue is a thermal treatment subdivided at a moderate temperature, then spun the product treated in this way and the The threads obtained are subjected to oxidation and then to charring, characterized in that that before or during the thermal treatment phase preceding the spinning, a hydrocarbon polymer is added to the starting material clogs. 2. The method according to claim 1, characterized in that the hydrocarbon polymers are Polyethylene, polypropylene, polystyrene, polybicyclo [2.2.1] hepten-2 or a natural one or artificial rubber is used. 3. The method according to claim 1 or 2, characterized in that the thermal treatment, which precedes the spinning, before the occurrence of the anisotropic phase or at the beginning the occurrence of the anisotropic phase stops. According to a variant of the process, the strongly aromatic tar pitch, which has only been filtered, is heated under such temperature, time and stirring conditions that the material obtained has little or no does not contain anisotropic material. The presence of this anisotropic material can be easily identified by testing can be detected in the optical microscope in polarized light (M. Ihnatowicz, P. Chiche, J. Deduit; S. Pregermain and R. Tournant, Carbon, 4, 41, [1966]). This thermal treatment can be carried out in one with an agitator and gas purging equipped reactor. The mixture can be heated to a much lower temperature, but not so much Extensive liberation of the material thus obtained from volatile components makes the Preservation of the infusibility of the fibers prior to charring, necessary oxidation treatments more difficult. 2ü The product obtained by this treatment is then spun by some means, then oxidized and charred in a manner known per se. The following examples illustrate the invention.