DE2151532A1 - Process for the production of carbon fiber tapes - Google Patents

Description

Patent attorneys

Dipl. Ing. C. Wallach? 5? 25 ^β 55 _β ^α · ^η λ t ηι / τ

Dipl. Ing. G. Koch ¹ ^ ^{63 H / Bu} 1 5. LOCATION.

D-. T. haiöach
8 Munich 2
Kaufingerstr. 8, Tel. 240275

THS SSCRBTARY OF STATS FOR DBFEMCE, London, UK Process for the production of carbon fiber ribbons

Coals «toffaserη are used for various purposes as Reinforcement used for a synthetic resin matrix body. As far as these fibers are laid in a winding process, is it is expedient to essentially consist of them in the form of a volume Manufacture longitudinally aligned fibers * by the present The invention is intended to provide a relatively cheap and simple method of making such tapes will.

The inventive method for making carbon fiber tapes provides that »by spreading out several tow strings from one raw material, several narrow bands are formed, that one arranges these tapes next to one another to form a web or film, that one heat treatment for this web Subjecting the production of a carbon fiber web, and that one the carbon fiber sheet thus obtained at the boundary lines between at least several pairs of the initial narrow ones Ribbons divided in such a way that wide ribbons are obtained, the width of which is an integral multiple of the width of the corresponds to initial narrow bands "

Preferably, the web is used to hold the constituent parts together

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Ribbons with a cross-stitch stitching

According to a preferred embodiment it is provided that the Carbon fiber web before splitting into the final Ribbons by resin transfer from a coated release paper is impregnated with synthetic resin.

Two-way can split the orbits into the final Bands like this are done »da * the bands alternately follow each other run up or down, which means that more winding roughness is gained.

The tow strings used as starting material can be spread out on a mooring or distribution bar or similar Devices take place.

According to a preferred embodiment, polyacrylonitrile serves as the pre-fiber, it being possible for the heat treatment to include pre-oxidation, in which the fibers are kept under tension for up to 7 hours in an oxygen-containing atmosphere at a temperature of approx. 200 ° C, and subsequent pyrolysis comprises, in which the fibers are heated to a temperature in the range from 700 to 1500 ^{0 C in an inert atmosphere.}

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In the following, exemplary embodiments of the invention are described with reference to the drawing; in this show

Fig. 1 is a flow diagram of an apparatus for implementation of the method according to the invention

Fig. 2 in a schematic representation of a device for Formation and cross-stitch stitching of a web or film made of fiber primary material

Fig. 3 in a schematic representation of a device for Separation of the carbon fiber web into ribbons

In Fig. 1, 10 denotes a bobbin assembly made up of several bobbins, each of which is made of polyacrylonitrile fibers of 1 1/2 denier. The individual coils are each placed on the device described below with reference to FIG. 2 wound to form and cross stitch a web. the Coils are wound with fiber webs, each of which comprises about 50 adjacent narrow strips, which in turn are each made from a single strand of tow; the tapes are inserted through one in the stapler Weft stitching thread held together. The eight lanes will be spaced about 3 inches apart held and fed to a roller assembly designated as Qanzes with 12. The drive roller assembly 12 has eight separate ones Sets of four orphans each; a Sats is denoted by 13. These sets of rollers are arranged in parallel so that each set of rollers is fed a web, which then by four The relevant set-forming driven rollers runs and on the output side in horizontal alignment with the inlet emerges from the drive unit.

After exiting the drive unit 12, the eight tracks are brought closer to one another at 14 and enter at 15 through tightly fitting openings in a pre-oxidation oven 16

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Furnace is maintained a heated to a temperature of about 22O ⁰ C air atmosphere by a blower system and (not shown) heaters. At 17 a Qebläsesystem is indicated which generates a controllable air flow in the oven.

Several sets of rollers 18 are arranged in the furnace 16. The eight tracks run over these rollers and are thereby in the oven along a meandering path, in such a way that they are within a relatively compact furnace cover a long path (40 FuA) i the arrangement is such that the Lanes need about 7 hours to pass through the oven.

During their stay in the furnace 16, the fibers are therefore pre-oxidized, ie a certain modification takes place between the individual molecules in order to stabilize their structure and their structure.

When exiting the furnace, pass through narrow-fitting openings 19 the fibers still in web form in a second drive roller unit 20 of the same type as the unit By arranging drive units 12 and 20 on both At the ends of the furnace 16, the fiber material can be kept under tension during its pre-oxidation. This creates a Avoid shrinkage that would otherwise occur during this procedural stage would take place.

When exiting the drive unit 20, the webs are combined to form a single bundle and over a Dying roller assembly 22 in a carbonation furnace 21 introduced. The sealing unit can consist of a pair of sealing rollers in the patent (patent application

P 18 05 901.3) exist and prevent a

significant leakage from the furnace 21 or into it.

The fiber webs are combined at this stage of the process »

to reduce the required power and simplify the system; at this stage of the procedure need not how in the previous stages, a distance between the tracks

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for the removal of reaction products and heat dissipation maintained Become KU.

A nitrogen atmosphere is maintained in the furnace 21; a line 23 is used to supply nitrogen, a line 24 is used to exit the nitrogen and exhaust gases. The arrangement is such that in the furnace, the temperature rises continuously from room temperature in the region of the sealing unit 22 to about 1000 ⁰ C in the funct 25th The furnace dimensions are chosen so that the main part of the pyrolysis of the fibers has taken place at point 25; therefore no further discharge of reaction products need be provided in the subsequent treatment.

Then the bundled fibers open through one a higher temperature lying part 26 of the furnace. It should be emphasized that in this part the furnace cross-section is reduced by wall devices 27 which contain heating devices is; This reduction in cross-section reduces the power required for heating to a higher temperature. In this section 26 the fiber is further heated to a temperature in the range of 1600 ° C.

The bundled fibers eventually pass out of the oven 21 a second sealing unit 28, again consisting of a roller seal.

After emerging from the sealing unit 28, the Fibers in a further furnace 29. In the drawing, this furnace is shown, for the sake of simplicity, as being separated from the furnace 21; in reality, however, it is directly connected to the seal 28 and the entire device forms a linear arrangement. The seal 28 thus actually separates the atmosphere inside the furnace 21 from the atmosphere in the furnace 29 · An argon atmosphere is maintained in the furnace 29 Inlet line 30 serves to supply argon, while argon and any reaction products can exit at an outlet line 31.

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In the oven 29, the fiber material is heated in its bundled nech mold to a temperature which iaa exemplary case described is ⁰ 250o C, but may have a value in the range of above 1500 ⁰ C. In this process the carbon fiber takes on a more pseudographic structure. This stage of the process may optionally be omitted completely and you can useful carbon f © ff-Fa ⁶ j © ra obtained with a carbonization in which the Fa3 s @ saa $;? @ Rial only to a temperature of IQOO ⁰ C to 1200 ⁰ C © rhitst will.

After a stay of about half an hour in the ) Oven 29, the fiber material enters via a® sealing device 32, which in turn is similar to the turning device 28 can be formed and a greater escape of oases from the oven 29 prevented. Immediately after leaving of the sealing device 32 run the bundled fibers between two drive orphans 33; after passing through these orphans, the bundled fibers are back into their 8 discrete ones Lanes separated and designated as a Ganges with 34 Harness impregnation device introduced. The resin impregnation device 34 can be of the type described in patent (patent application P 20 00 126.6); it is based on the use of coated paper as a transfer medium for an epoxy novolac synthetic resin. For the sake of simplicity, will the following describes the further course of a single path; the other tracks follow exactly the same course.

If you first look at the upper track, it comes after the entry into the device 34 between two coils 35 and 36 with synthetic resin soaked release paper. The release paper is in turn impregnated with a release agent in order to prevent permanent adhesion of the synthetic resin to the paper. To the simpler Handling of the coated paper, the coils 35 and 36 are arranged in a cooled chamber 37, so that the

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Resin is kept non-sticky.

The paper coming off the spools 35 and 36 is fed by both Pages fed to the fiber web, in such a way that the coated side of the paper comes to lie against the fiber web. The "sandwich layer" formed in this way runs out of the chamber 37 in a quarreling chamber 38 between two Heiswalien 39 · leg The passage wipe these w & lien is thru the combined Effect of Wflrae and pressure the resin from the release paper onto the paserbane and so on the fibrous sheet with the synthetic resin impregnated.

The individual fiber webs then run through a device to produce a band; the banding devices for the single tracks are alike and it only becomes the banding device for the Paserbahn 40 described.

At the entrance of the tape suction device are two wind-up whales 41 to remove the release paper from the? impregnated with d @ m Kunsthart Fiber web provided. Pie exposed fiber web then runs through a further pair of rollers 42 and is here in several Divided ribbons that alternate up and down on take-up spools 43 and 44 are running. From a supply roll 45 is Interleaving paper in the manner shown on the take-up reel suggests.

In Fig. 3 is a simplified embodiment of the d @ L * banding device shown, it being arrived at that the fiber web is divided into two bands; As can be seen, the tape running onto the reel 43 runs after the rollers 42 down, while the tape running on the reel 44 runs upwards from the rollers. That way you get more space between the take-up spools. In the embodiment shown in Fig. 3, the supply rolls with the interleaving paper are below of the associated take-up reels shown horizontally. the Supply rolls with the interleaving paper could also each

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«Be arranged between adjacent take-up reels. In this case they were alternately above and below their associated Aufwiokelspulen lie and all the coils could be arranged on two axes.

In Fig. 2, the formation of the web from the tow strands is shown schematically. The tow strands are fed from a plurality of reels 46 and guided over a distributor rod 47. The distance between the tow strands is chosen so that the individual tow strands come against the neighboring tow strand when they are fully extended . Since the bands formed by neighboring tow strands do not overlap, there is a clear demarcation between the bands; this is indicated by the dashed lines on track 48.

Cross-stitch stitching is used to hold the web together during its heat treatment. This is done using the

device indicated at 49, which is derived from that in patent

(Patent application P 18 05 901.3) described type can be. The stitching is preferably carried out with a material which is substantially weakened by the heat treatment so that it does not hinder the subsequent splitting of the web into the individual bands. The thus obtained held together by cross-stitch stapling w web is then wound on a spool, which in turn can be then used in the apparatus in FIG. 1.

The method according to the invention allows a number of alternatives Refinements. While in the described embodiment Polyacrylonitrile is used as the fiber VormateriaX, the inventive method is obviously suitable for Used with a wide variety of raw materials, including polyamide and cellulose fibers.

The procedure itself can also be modified in detail

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BATH ORIGINAL

2) 51532

will. Thus, the release paper may not necessarily before the separation of the sheets in the one a ligament removed from the webs are provided below ₉ that the gap devices may divide the release paper webs; of course, other methods of resin impregnation can also be considered.

Normally, with the arrangement according to the invention, the tow strands will be separated at the beginning by knotting the ends of the tow strands before they are introduced into the apparatus; then the individual narrow strips can be easily separated as they exit the furnace and divided into the required strip width. As can be seen, the invention provides a simple method of producing ribbons whose width is a multiple of the initial sshmalan bandwidth; the width of these initial bands depends on the number of fibers in the pre-material strand, as well as on the direction of expansion.

Claims;

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Claims (6)

Patent claims 1. A process Eur production of carbon fiber strips, characterized _s that forms a plurality of tows from one material by spreading a plurality of narrow bands, that these ribbons side by side to form a sheet or film .. (48, Fig. 2} arranges that this web is subjected to a heat treatment to produce a carbon fiber web, and the carbon fiber web thus obtained is subdivided at the boundary lines between at least several pairs of the initial narrow ribbons so that wide ribbons are obtained, the width of which is an integral multiple of the width corresponds to the initial narrow bands. 2. The method according to claim 1, characterized in that that the web (48, Fig. 2) formed from the initial ribbons is cross-stitched prior to heat treatment is provided for cohesion. 3. The method according to claim 1 or 2, characterized in that the carbon fiber web before Splitting into the final ribbons by resin transfer from a coated release paper impregnated with resin. 4. Procedure according to one or more of that. " preceding claims, characterized in that the separation of the web into the final ribbons takes place in such a way that the individual ribbons alternate upwards or run down. 5. The method according to one or more of the preceding claims, characterized in that the raw material tow strands used as the starting material be spread on a distribution rod (47, Fig. 2). 209830/0511 6. The method according to one or more of the preceding claims, characterized in that polyacrylonitrile is used as a preliminary material. 7 «A method according to claim 6, characterized in that the heat treatment a pre-oxidation, wherein the fibers are maintained at a temperature of about 200 ⁰ C for up to 7 hours under stress in an atmosphere containing oxygen and a subsequent pyrolysis comprising, wherein the fibers are heated to a temperature in the range from 700 to 1500 ^{° C. in an inert atmosphere.} 209830/051 1