DE2115153A1 - Process for producing carbon threads - Google Patents

Description

DA-4256

Description of the patent application

of the company

COURTAULDS LIMITED 18, Hanover Square, London, W. 1, United Kingdom

concerning

Process for producing carbon threads

Priority: March 31, 1970, No. 15134/70, Great Britain

The invention relates to the production of carbon threads, which because of their high strength and high modulus as a reinforcement material for composite Structures are suitable.

A well-known process for making carbon

109847/1816

ORlGiNAL IHSPECTED

threads consists in using threads made of polymeric material, z. B. polyacrylonitrile, successive heat treatments at different temperatures and in different atmospheres suspends. For example, in a first stage, the threads can be heated to a temperature of about 200 to 300 ° C., preferably under tension and preferably also in an oxidizing atmosphere, e.g. B. an atmosphere of air or exposed to oxygen-enriched air. "Then the threads can be at a temperature above are carbonized at 1,000 ° C in an inert atmosphere, and, if desired, they can then be used at higher temperatures, e.g. B. in the range from 2,000 to 3,000 ° C in an inert Atmosphere so that a more pronounced graphite structure develops in the threads.

Polyacrylonitrile threads are defined here as threads which have been spun from homopolymers of acrylonitrile or from mixed polymers thereof and which contain not less than 80% by weight of polyacrylonitrile.

According to the invention there is a method for producing Carbon threads in that one polyacrylonitrile threads of the above Definition of a temperature of 160 to 199 ° C in one heated first heating zone, heated the threads under tension in a second heating zone to 200 to 300 ° C, then the threads in an inert atmosphere at a

ORiGlNAL INSPECTSD

Carbonized at a temperature of at least 1,000 ° C. If if desired, the carbon threads can then be stored in an inert atmosphere at a temperature of 2,000 graphitized up to 3,000 ° C.

The filaments produced according to the invention have better properties than those produced according to the known above processes mentioned. This own. Shafts are assigned to the additional, upstream heating stage. According to the invention, carbon threads with a higher tensile strength and without loss of modulus than carbon filaments produced according to known processes are accessible if the conditions for the corresponding heating stages are the same.

The filaments can remain in the first heating zone for 1/4 to 4 1/2 hours and the temperature of this zone is preferably in the range of 175 to 190 ° C. The zone can be an inert atmosphere, e.g. B. have a vacuum, but it preferably contains an oxidizing atmosphere. Likewise , the second heating zone can have an inert atmosphere, but it preferably also contains an oxidizing atmosphere.

The process according to the invention can easily be carried out on a continuous basis Threads, preferably on a continuous basis, through

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be led. ' The threads are preferably during looking forward to the whole process. This can be achieved in the stages at which the threads tend to shrink, by withdrawing them from this stage at the same rate as they are being fed in.

The following example illustrates the invention. In the example, reference is made to FIGS. 1 and 2.

Figure 1 is a schematic sectional side view of a furnace which can be used for the purposes of the invention and
Figure 2 is a section along the line II-II of the figure

example

As can be seen from Figures 1 and 2, in a rectangular furnace 1 are two driven, inclined rollers 2 and 3 attached. Outside the furnace 1 there is a driven inlet roller 4 and a driven outlet roller The inlet roller 4 is arranged next to a cable inlet channel 6 in a wall 7 of the furnace 1 and the outlet roller 5 is located next to a cable outlet in the wall 7 of the furnace, means (not shown) for introducing hot air are in the furnace 1 is provided.

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A continuous cable 9 made of polyacrylonitrile thread was over the inlet roller 4, around the outlet roller 5 and back to the inlet roller 4 and then through the cable inlet passage 6 out into the furnace 1, as indicated by the arrows a. The atmosphere of the oven was kept at a temperature of 182 ° C.

In the oven the cable was wound in a number of turns placed around the inclined rollers 2 and 3 as shown before it leaves the furnace through the outlet duct 8. The cable was then passed over the outlet roller 5, around the inlet roller 4 and then back passed around the outlet roller 5 before it was fed to the next process stage. The rollers 2, 3, 4 and 5 are all driven at the same peripheral speed, so that the cable as a result of its inclination to Shrinking under tension. The speeds of rollers 2, 3, 4 and 5 were such that the dwell time of the cable in the oven was about 4 1/2 hours.

The cable was then subjected to a second heat treatment in a second furnace (not shown), which is the furnace 1 was similar. The second furnace had an atmosphere of air and was heated to 220 ° C; the dwell time of the cable was 6 hours. The cable was again held under tension and withdrawn at the same speed as it was

1 O 9 8 4 7/1 '8 1 6

inserted into the oven. Eventually the cable was carbonized by standing it for several hours through a carbonization furnace (not shown) with an inert atmosphere and a temperature greater than that than 1 100 ° C sent.

The resulting carbon threads were tested, whereby their ultimate tensile strength and modulus have been measured by the single thread method specified by "Design Engineering "in the series" Carbon fibers "on page 63» 1970 by The Books Division of Morgan-Grampian Ltd. have been published in connection with "Design Engineering". The results, which are the means of Tests on 20 threads with a length of 5 cm were: A tensile strength of 23,900 kp / cm and a modulus of

/ r ρ

2.6 10 kgf / cm. In comparison, the tensile strength was 20,500 kgf / cm ² and the modulus was 2.59 x 10 ⁶ kgf / cm ² for carbon threads which were produced by the same process, but with the difference that the first heating stage at 182 ° C. was omitted became.

Claims

109847/1 "8 16

Claims (1)

Claims 1. Process for the production of carbon threads or fibers, polyacrylonitrile filaments being placed under tension in a heating zone at a temperature of 200 heated to 300 ° C, the threads then in an inert atmosphere at a temperature of at least 1,000 ° C carbonized, characterized in that the threads are initially under tension in a first heating zone at a temperature of 160 to 199 ° C, after which it is heated to 200 to 300 ° C in a second heating stage. 2. The method according to claim 1, characterized ^ that the temperature at which the Polyacrylonitrile threads are heated in the first heating stage, set to 175 to 190 ° C. 3. The method according to claim 1 or 2, characterized in that the polyacrylonitrile threads heated in the first heating stage for 1/4 to 4 1/2 hours. Process according to Claims 1 to 3, characterized in that the polyacrylonitrile threads 109847/1 ^ 16 continuous threads used. 5. The method according to claim 4, characterized in that the continuous threads passes continuously through the first heating zone and withdraws from that zone at the same rate at which they were fed. 6. The method according to claim 1 to 5, characterized in that the polyacrylonitrile threads in the first heating zone in an oxidizing Atmosphere heated. 7. The method according to claim 1 to 6, characterized in that the polyacrylonitrile threads heated in a second heating zone in an oxidizing atmosphere. 8. The method according to claim 6 or 7, characterized in that - indicates that an oxidizing atmosphere containing air is used. 9. The method according to claim 1 to 8, characterized in that g e - · indicates that the carbon threads' then graphitized in an inert atmosphere at a temperature of 2,000 to 3,000 ° C. 7/1016