US3500482A

US3500482A - Production of carbon fibres

Info

Publication number: US3500482A
Application number: US648917A
Authority: US
Inventors: Thomas Lloyd; Patrick Mcmullen
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-08-18
Filing date: 1967-06-26
Publication date: 1970-03-17
Anticipated expiration: 1987-03-17

Description

March 17, 1970 T. LLOYD ETAL rnonucwlon or CARBON FIBRES Filed June 26. 1967 INVENTORS THOMAS LLOYD ATTORNEYS PATRICK MC MULLEN United States Patent US. Cl. 8151.2 10 Claims ABSTRACT OF THE DISCLOSURE A device for feeding fibres of organic polymer material to an oxidizing oven in the process of manufacture of carbon fibres from the fibres. The device includes tensioned fibre supply means and a pair of rollers adjacent the oven for supporting successive separated turns of fibres from the supply means. At least one of the rollers is driven at a rate such that the fibre is held taut in passing from the rollers to driven means within the oven so that the fibre can undergo at most a controlled and limited change in length compared with its original length. Brake means are operable to apply a braking force to the fibres supplied to the rollers to maintain same at a tension suflicient to prevent slippage of the fibres on the rollers.

This invention relates to apparatus for feeding fibres of organic polymer material to an oxidising oven in a process for the manufacture of carbon fibres from said material. A tow of fibres passes from a braked supply spool in successive turns over a pair of driven rollers outside the oven. The fibres are drawn into the oven at a predetermined rate and the rollers are driven at such a rate to feed the fibres to the oven so that the tension in the fibres extending from the rollers into the oven is accurately controlled.

This invention relates to apparatus for feeding fibres of organic polymer material to an oxidising oven in a process for the manufacture of carbon fibres from fibre tow of organic polymer material.

In co-pending US. patent application Ser. No. 648,916 processes are disclosed for the continuous production of high strength carbon fibres from fibres of anorganic polymer of a type in which the linear molecules can be cross-linked, for example by oxidation by heating at below their melting point in an oxidising atmosphere, or, if the polymer fibre is of a type having no melting point, heating in an oxidising atmosphere at a temperature which allows oxidation to proceed in a controlled manner, and which upon subsequent carbonising in a nonoxidising atmosphere yield carbon fibres which are highly crystalline with the C axis of the crystallites preferentially aligned normal to the fibre longitudinal axis, which include an oxidising step in which a continuous length of fibre passing from an external source into an oxidising atmosphere in an oven wherein it is heated to a temperature of 200-250 C. (or not appreciably above 250 C.) travels therein between supporting and driving means which support and drive the fibre so as to maintain the portion of the fibre travelling between the supporting and driving means under sufficient tension to reduce or prevent shrinkage of the fibre or to elongate it and whereby each unit length of fibre remains in the oven for the required period.

As disclosed in the above referred to US. patent application Ser. No. 648,916 the fibre is fed under very accurately controlled tension to the supporting means within the oxidising oven.

3,500,482 Patented Mar. 17, 1970 ice It has been found in practice to be desirable that the fibre entering the oven and on its way to but not yet acted on by the supporting and driving means should be prevented from any undesirable shrinking or stretching due to its temperature on entry being raised from the ambient temperature outside the oven towards the 200"- 250 C. range within the oven.

The present invention is concerned with the provision of apparatus for feeding the fibre to be treated to the oven in which oxidation takes place as referred to above under controlled tension whereby any tendency to shrinkage or stretch of the fibre may be controlled.

In apparatus for feeding fibres of an organic polymer material of the type referred to, to an oxidising oven through which they are drawn at a predetermined rate for oxidation as disclosed in co-pending US. patent application Ser. No. 648,916, according to the present invention, a pair of equal diameter supporting rollers at least one of which is driven are located immediately outside the oven adjacent the inlet to the oven through which the fibre passes and the fibre passes over both of these ex ternal supporting rollers from one to the other several times before passing to the oven from the external supply.

The fibre is driven by the external rollers at a speed in relation to the speed of drawing the fibres through the oxidising oven such that the length of fibre extending from the external rollers to take up means within the oven is maintained under controlled tension.

To avoid damage to the fibres during their passage over the external supporting rollers the rollers are supported with their axes of rotation in parallel planes blit skewed with respect to each other,'on the well known thread advancing principle, so that succeeding turns of fibre on the rollers do not contact each other.

A controlled tension is applied to the fibre between an external source and the up-strearn supporting roller by tensioning means which conveniently comprise a variabletorque coupling such as a fluid coupling associated with the external supply source or a magnetic clutch. This tension is set so that there is substantially no slippage of fibre in its passage over the external supporting rollers and so that undue tension is not applied to the fibre.

One preferred arrangement of apparatus for feeding fibres according to the invention is illustrated by the accompanying diagrammatic drawing which is a sectional,

side elevation.

Part of the wall of an oxidising oven of the type disclosed in co-pending US. patent application Ser. No. 648,916 is shown at 11 and, within the oven, the first supporting and driving roller 12 of the first of two pairs of such rollers. An inlet for air to the oven is provided at 13. A pair of

rollers

14, 15, of the same diameter as the roller 12, are supported on shafts 16, 17, for rotation in a frame shown generally at 18 with their rotation axis in parallel planes but skewed as shown.

The shaft 17 carries a bevel gear wheel 19 for engagement with a corresponding bevel wheel (not shown) driven by a common driving shaft 23 which also drives the roller 12. A supply spool 20 is supported for rotation on a shaft 21 and is controlled through a variable torque coupling 22 as will later be described.

In operation a tow of fibre is wound onto the rollers which comprise the supporting and driving means for the fibres within the oven 11.as described in the above referred to co-pending application, only one such roller being shown at 12. One end of the fibre tow is then passed out through the air inlet 13 and wound five times over the

rollers

14, 15 from one to the other in elongated loops with succeeding loops separated from each other. The end of the tow is then joined to an end of the tow of fibre on the supply spool 20. The oven is now closed and the

rollers

15, 12 and the corresponding roller (not shown) to the roller 12 'within the oven are driven at the same speed. The take up spool down-stream of the oven and referred to in the co-pending application No. 28,879/69 is also driven. The fibre tow is thus drawn onto the take up spool and any slack in the tow of fibre passing over the

rollers

14 and 15 and the rollers in the oven is taken up. The release of fibre from the supply spool 20 is controlled 'by the torque coupling 22 to prevent slippage of the fibre on the rollers and the skewing of the

rollers

14, 15 advances the tow of fibre with succeeding loops separated. The oven is now brought'up to temperature.

Using fibres of Courtelle (registered trademark), a polyacrylonitrile fibre containing minor proportions of other constituents, in the form of. a tow comprising a bundle of 10,000 fibres of 1% denier the torque coupling was set to apply a tension within the range of 8 ozs. to 1 lb. The temperature in the oxidising oven was maintained at 220 C.

It will be seen that with this arrangement in which the fibre tow is prevented from slipping on the internal and external rollers and the rollers are driven at the same speed and are of the same diameter, the length of fibre tow which extends between the external roller 15 and the first internal roller 12 at any time ,is kept constant and neither shrinkage nor stretch occurs during this period.

If limited shrinkage or stretch of the length of fibre extending between the roller 15 and the roller 12 is required this can be achieved by making the

drums

14 and 15 of different diameter and/ or by driving them at a different speed to those inside the oxidising oven for example, by means of a gearbox 24. The rates of drive of the

rollers

14, 15 and the roller 12 may be such that the fiber therebetween is tensioned within the range of percent shrinkage to 20 percent stretch.

I It is to .be noted that the term polyacrylonitrile fibres is used by those skilled in this art to include co-polymers or terpolymers of acrylonitrile with other monomers e.g. methyl methacrylate or vinyl acetate, either alone or to which have been added polymers compatible with them for example phenolic resins or Friedl-Crafts condensates. It is in this sense that the term polyacrylonitrile fibres is usedthroughout the specification.

We claim:

1. Apparatus for feeding fibres of organic polymer material to an oxidising oven in a process for the manufacture of carbon fibres from said material comprising:

supporting means for carrying a supply of fibres,

tensioning means associated with said supporting means,

a pair of rollers adjacent said oven for supporting successive separated turns of fibres'from said supporting means in continuous form,

means supporting said rollers for rotation with their axes of rotation in parallel planes,

drive means for driving at least one of said rollers to advance said supported fibres towards said oxidising oven, and, driven means within said oven for drawing said fibres into saidoven at a predetermined rate, said drive means driving said roller at a rate such that the fibres are held taut in passing from said rollers to said driven means within the oven and can only undergo at .most a controlled and limited change in length compared with its original untreated length and said tensioning means being operative'to apply a braking force to said "supporting means whereby the length of fibres extending from said supporting means to said rollers is maintaified under tension sufiicient to prevent slippage of said fibres on said rollers;

2. Apparatus as claimed in claim l'for the production of'carbon'fibre from polyacrylonitrile fibre in which the ra 9? dr e i d ql e s an s i r n means a e such that the fibres extending therebetween are tensioned to a length within the range of from 10 percent shrinkage to 20 percent stretch with respect to their free length.

3. Apparatus as claimed in claim 1 wherein the axes of rotation of said rollers are skewed with respect to each other in the parallel planes whereby successive turns of fibres are advanced along said rollers and their separation maintained. 7

' 4. Apparatus as claimed in claim 3 wherein the rate of drive of said rollers and said driven means are such that the fibres extending therebetween are held to a length within the range of from 10 percent shrinkage to 20 percent stretch with respect to their free length.

5. Apparatus as claimed in claim 1 for the production of carbon fibres from polyacrylonitrile fibres in which said drive means are common to said rollers and to said driven means, which latter comprises a driven roller withm sard OXldlSlHg oven, and all said rollers are of the same 3 diameter and the driven rollers are driven at the same speed.

6. Apparatus as claimed in claim 5 wherein the axes of rotation of said rollers are skewed with respect to each other 1n the parallel planes whereby successive turns of T fibres are advanced along said rollers and their separation maintained.

7. Apparatus as claimed in claim 1 and comprising a gear box for transmitting drive to said at least one roller to drive said roller such that its peripheral speed is 5 different from the predetermined rate of drawing said fibres into said oxidising oven.

8. Apparatus as claimed in claim 1 in which said drive means are common to said rollers and to said driven means, which latter 'comprises a driven roller within said oxldlsmg oven, and said roller within the'oven is of a carbon fibres of high strength and Youngs modulus wherein a continuous organic polymer fibre is drawn through an oxidising oven maintained at a temperature of about 2Q0 -2 C. and subsequently carbonized in a non-carbonrzmg atmosphere, and wherein the fibre travels bet-ween take-up means comprising supportingmeans and driving means within the oven, the improvement which comprises the step of passing the fibre several times around a pair of rollers disposed adjacent said oven withtheir axis in a single plane and skewed to advance said fibre such that succeeding turns thereof are maintained out of contact with one another, at least one of said rollers being driven to feed said fibre to the supporting means and driving means in said oven at a rate such that the length of fibre extending between the rollers and the take-up .means in the oven is maintained under a controlled tension.

10. A- process according to claim 9 wherein said tension is such that said length fibre is tensioned to a length within the range 10 percent shrinkage to 20 percent stretch.

References Cited UNITED STATES PATENTS 2,673,385 3/1954 Williamson et a1. 28-59.5 2,692,875 .1o/19s4 Weinstock et al 28-71.3 2,807,863 10/1957 Schenker 2859.5X

WILLLAM I. PRICE, Primary Examiner US. 01. X.R. 8-140; 28 72; 68-2, 5; 24245