Fiber bundle with pieced part, process for producing same, and process for producing carbon fiber

Abstract

A fiber bundle which has a pieced part formed by jetting a pressurized fluid against a fiber-bundle overlap is formed either by directly superposing the ending part of a fiber bundle composed of many fibers on the beginning part of another fiber bundle composed of many fibers or by superposing the end part and the beginning part on a jointing fiber bundle composed of many fibers, whereby the many fibers of the fiber bundles are interlaced with one another to thereby piece up the fiber bundles. The pieced part comprises an opened-fiber part in which the fibers have been opened and interlaced-fiber parts respectively located on both sides thereof, each interlaced-fiber part being composed of a plurality of constituent interlaced parts located apart in the width direction for the fiber bundle.

Description

FIELD OF THE INVENTION[0001]The invention relates to a fiber bundle having a fiber joint portion, a production method thereof, and a carbon fiber production method. When carbon fiber is produced from precursor fiber bundles designed for carbon fiber produce, it is sometimes necessary to continue supplying such precursor fiber bundles to a carbon fiber production process for a long period of time. In such cases, it is necessary to join the tail end portion of a precursor fiber bundle for carbon fiber production with the front end portion of another precursor fiber bundle for carbon fiber production to produce a continuous precursor fiber bundle. A fiber-joint-portion-containing fiber bundle according to the invention can be used effectively for such production of a continuous precursor fiber bundle.BACKGROUND OF THE INVENTION[0002]In general, precursor fiber bundles specially designed for carbon fiber production are used in carbon fiber production processes. These precursor fiber bun...

AI Technical Summary

Benefits of technology

[0015]The invention aims to provide a fiber bundle having a fiber joint portion that serves to solve the problems in the prior art, and a production method thereof. The invention also aims to provide a method to produce carbon fiber from a fiber-joint-portion-containing fiber bundle according to the invention, wherein the fiber joint portion does not suffer significant heat accumulation, and the fiber joint portion does not suffer burnout due to heat accumulation during a calcination step, and that the fiber bundle can pass the production process smoothly.

[0034]When subjected to continuous calcination in a calcination step, the fiber-joint-portion-containing fiber bundle according to an embodiment of the invention does not suffer breakage of fiber bundles or slippage of fibers of the fiber bundles out of the fiber bundles during the calcination step, serving to prevent heat accumulation in the fiber joint portion and efficiently achieve heat removal from the fiber joint portion.

[0035]Consequently, the fiber-joint-portion-containing fiber bundle according to an embodiment of the invention can be passed continuously through the calcination step at a temperature that is not significantly lower than the furnace temperatures of calcination steps commonly used for fiber bundles free from a fiber joint portion or for a portion other than the fiber joint portion of a fiber-joint-portion-containing fiber bundle, allowing calcined fibers, such as carbon fiber, to be produced continuously through prolonged implementation of a calcination step with high operating efficiency. As a result, the productivity for calcined fibers, such as carbon fiber, can be improved largely.

Problems solved by technology

However, though it is actually possible to join the end portions of precursor fiber bundles by this method, the fiber density will be too high in the fiber joint portion formed, giving rise to the problem of runaway of the oxidization reaction caused during the oxidizing step by the heat generated from the precursor fiber bundles themselves.

Accordingly, there have been accidents involving thermal destruction and burnout of the fiber joint portion.

If the temperature of the oxidizing step is lowered significantly, however, a longer time will be required for carrying out the oxidizing step, leading to a considerable decrease in the productivity for the desired carbon fibers.

In addition, sufficient interlacement will not be achieved in the fiber joint portion, leading to a smaller binding strength between the precursor fiber bundles.

As a result, the fiber bundles will become unable to resist the tension caused during the process, leading to rupture or slippage of the bundles in the fiber joint portion.

Though this method can reduce the quantity of heat accumulation, however, the heat in the joint portion cannot be removed sufficiently, and breakage of the yarn may still occur easily in the joint portion where the fiber density has increased.

In addition, the oxidized fibers that constitute the joint fiber bundle and the fibers that constitute the polyacrylonitrile-based precursor fiber bundle are different in the way they are unraveled in their respective bundles, and accordingly, the fibers that constitute the polyacrylonitrile-based precursor fiber bundle and the oxidized fibers that constitute the joint fiber bundle are not commingled sufficiently and fail to be interlaced uniformly.

This can cause slippage of these fiber bundles, leading to forced shutdown of the oxidizing furnace for fire prevention purposes.

In this case, the joined bundles form nodes, which are tightened to increase the fiber density in the joint portion, leading to heat accumulation that causes breakage of the yarn.

Furthermore, there will be a large variation in the binding strength among the sub-bundles in the joint portion, and a stress is concentrated on those sub-bundles with a smaller binding strength, causing breakage of the sub-bundles starting with those with a smaller binding strength.

In this case, though breakage of the yarn due to heat accumulation in the joint portion tends to be reduced, a special apparatus is required to make the end portions of the precursor fiber bundles to oxidized fibers, leading to a lower productivity.

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