JP2000160435A - Continuous thermal treatment of acrylic fiber bundle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously thermally treating acrylic fiber bundles, capable of efficiently producing flame-resistant yarns having a high quality. SOLUTION: This method for continuously thermally treating acrylic fiber bundles comprises introducing a fiber bundle sheet-like article comprising many paralleled acrylic fiber bundles into a flame resistance-imparting oven in a surface occupation degree of 36-65% on the bottom surface of the flame resistance-imparting oven, passing a gas in a direction vertical to the fiber bundle sheet-like article in the flame resistance-imparting oven at a gas flow rate of 0.3-1.5 m/see or in a direction parallel to the fiber bundle sheet-like article in the flame resistance-imparting oven at a gas flow rate of 1.5-5 m/sec, and controlling the process tension of the acrylic fiber bundles travelling in the flame resistance-imparting oven to 0.5-2.5 g/tex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously heat-treating an acrylic fiber bundle capable of efficiently producing high-quality flame-resistant fibers.

[0002]

2. Description of the Related Art Carbon fibers have excellent specific strength and specific elastic modulus as compared with other fibers, and also have excellent specific resistance and high chemical resistance as compared with metals. Due to these excellent various properties, it is used as a reinforcing fiber for a composite material with a resin, and is widely used in industrial applications, sports applications, aerospace applications, and the like.

[0003] In general, carbon fibers are converted into oxidized fibers by an oxidizing atmosphere in which an organic fiber such as polyacrylonitrile, rayon or pitch is heat-treated at 200 ° C or more in an oxidizing atmosphere. Is obtained by performing a carbonization step of heat-treating the oxidized fiber in an inert atmosphere at a temperature of 300 ° C. or higher. Therefore, the oxidation treatment is usually performed under operating conditions on the heat removal side.

[0004] In order to improve the productivity of carbon fibers, it is necessary to improve the productivity of the flame-proofing step which requires the longest processing time during the manufacturing process. As a means to improve the productivity of
20 vol. Japanese Patent Laid-Open No. 2-154013 discloses a method of performing a flame-proofing step in an oxidizing atmosphere containing at least
This is described in the official gazette.

[0005] However, the above-mentioned Japanese Patent Application Laid-Open No. 2-1540 is disclosed.
No. 13 discloses that in order to improve the productivity of high-quality carbon fiber, while improving the productivity in the oxidization-resistant step of converting the oxidized fiber into a non-oxidized fiber, the single-filament treatment fiber bundle has a small spot. Parameters required in the oxidization process required to enable the oxidization fiber to be supplied to the carbonization process, that is, the density of the fiber bundle to be heat-treated in the oxidization furnace, the wind speed in the oxidization furnace, the oxidization process No attempt is made to optimize the process tension of the fiber bundle to be heat-treated.

[0006] As a method for improving the productivity of the oxidizing step, the amount of the fiber bundle to be heat-treated into the oxidizing furnace is increased, the oxidizing furnace is made to have a high volume density, and the fiber bundle to be heat-treated is increased. Heat-treating, that is, reducing the distance between adjacent fiber bundles in a plane parallel to the bottom surface of the stabilization furnace to perform the stabilization process, or supplying a thick fiber bundle to be heat-treated to perform the stabilization process And the like.

[0007] However, when the distance between adjacent fiber bundles is reduced, not only the temperature control in the furnace becomes difficult due to an increase in the amount of heat generated by the oxidation reaction in the oxidizing furnace, but also the heat removal becomes poor. In addition, smoke, which leads to generation of harmful gas, also easily occurs. In addition, since adjacent fiber bundles are mutually affected by heat generation, the heat treatment temperature cannot be increased, and as a result, productivity cannot be improved. Furthermore, single yarn breakage occurs due to contact between adjacent fiber bundles on a surface parallel to the bottom surface of the oxidation furnace,
This leads to a decrease in the quality of the carbon fiber.

[0008] Even in the case where a thick fiber bundle to be heat-treated is supplied and the oxidation treatment step is performed, simply increasing the thickness of the fiber bundle to be heat-treated makes the heat removal failure in the oxidation furnace more remarkable and causes harmful gas. This not only causes smoke to be generated, but also lowers the heat treatment temperature, so that productivity cannot be improved as a result.

If an attempt is made to increase the thickness of the fiber bundle to be heat-treated and to shorten the heat-treatment time, the operation at a temperature near the smoke generation temperature is inevitable. This results in deterioration of the quality of the carbon fiber because the fiber becomes a flame-resistant fiber having a large unevenness in the fiber treatment.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method of continuously heat-treating an acrylic fiber bundle which leads to high production of high-quality carbon fibers, that is, to provide a high-quality flame-resistant fiber. An object of the present invention is to provide a continuous heat treatment method for an acrylic fiber bundle that can be efficiently produced.

[0011] In order to improve the productivity of high quality carbon fibers, it is necessary to achieve an improvement in the productivity in the oxidization-resistant step of converting the oxidized fibers into oxidized fibers, and to improve the oxidization resistance of the treated fiber bundles having a small single fiber treatment spot. The problem to be solved by the present invention is to supply the fibers to the carbonization step, and the problem to be solved by the present invention is the density of the fiber bundle to be heat-treated in the oxidation furnace, An object of the present invention is to provide a method for continuously heat-treating an acrylic fiber bundle in which the wind speed and the process tension of the fiber bundle to be heat-treated in the flame-proofing step are optimized.

[0012]

The above-mentioned object is achieved by a method for continuously heat-treating an acrylic fiber bundle according to the present invention having the structure described below. That is, the first invention is
Continuous heat treatment of acrylic fiber bundles into oxidized fiber by heat-treating a fiber bundle sheet made up of many acrylic fiber bundles into an oxidizing furnace consisting of a hot air circulation type convection heating furnace In the method, the surface occupancy of the fiber bundle sheet introduced into the oxidation furnace with respect to the bottom surface of the oxidation furnace is set to 36 to 65%, and the wind direction in the oxidation furnace is perpendicular to the fiber bundle sheet. And the wind speed is set to 0.3 to 1.5 m / sec, and the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is set to 0.5 to 2.
It consists of a continuous heat treatment method of an acrylic fiber bundle at 5 g / tex.

In the method for continuously heat-treating an acrylic fiber bundle according to the first aspect of the present invention having the above structure, it is preferable that the running path of the fiber bundle to be heat-treated is regulated by a groove roller.

[0014] The second invention also provides a flame-retardant material by heat-treating a fiber bundle sheet in which a large number of acrylic fiber bundles are aligned in a flame stabilization furnace comprising a hot air circulation type convection heating furnace. In the method for continuously heat-treating an acrylic fiber bundle to be oxidized fiber, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is set to 36 to 65.
% And the direction of the wind in the oxidation furnace is parallel to the fiber bundle sheet, and the wind speed is 1.5 to 5 m / s.
ec and a continuous heat treatment method of the acrylic fiber bundle in which the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is set to 0.5 to 2.5 g / tex.

In the continuous heat treatment method for an acrylic fiber bundle according to the second aspect of the present invention having the above-described structure, it is preferable that the running path of the fiber bundle to be heat-treated is regulated by a groove roller.

In the continuous heat treatment method of the present invention, the surface occupancy of the fiber bundle sheet introduced into the oxidizing furnace with respect to the bottom of the oxidizing furnace depends on the oxidizing furnace used. Product of effective furnace length and effective furnace width (=
This is the ratio of the flat area of the fiber bundle sheet to be introduced into the oxidation furnace to the effective area of the bottom surface of the oxidation furnace.

The plane area of the fiber bundle sheet to be introduced into the oxidizing furnace is the width of a single fiber bundle measured on a roller when the fiber bundle sheet is introduced into the oxidizing furnace. The effective furnace length of the furnace × the number of acrylic fiber bundles, and the surface occupancy (%) of the fiber bundle sheet-like material introduced into the oxidizing furnace with respect to the bottom surface of the oxidizing furnace = (the single acrylic fiber bundle Width x number of acrylic fiber bundles x 100 / effective furnace width of flameproofing furnace)
It is. The wind speed in the flame-proof furnace is a measured value at normal temperature.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the continuous heat treatment method for an acrylic fiber bundle of the present invention, an acrylic fiber bundle to be used as a fiber bundle to be heat-treated is an acrylic fiber containing 100% acrylonitrile or an acrylic fiber containing 90% by mole or more of acrylonitrile. Polymeric fibers are preferred. Acrylic acid, methacrylic acid, itaconic acid, and alkali metal salts, ammonium metal salts, acrylamide, methyl acrylate, and the like thereof are preferable as the copolymer component in the acrylic copolymer fiber. The chemical properties, physical properties, dimensions, and the like of the bundle are not particularly limited.

The inside of the hot air circulation type convection heating furnace for performing the flameproofing treatment of the acrylic fiber bundle is maintained in an oxidizing atmosphere at 200 ° C. to 360 ° C., and a large number of acrylic fiber bundles are placed in the hot air circulation type convection heating furnace. A fiber bundle sheet material in which books are aligned is introduced, and the sheet material is subjected to a heat treatment while being run in parallel over a plurality of stages via a plurality of rollers to be made into an oxidized fiber.

The number of stages of the fiber bundle sheet in a single chamber depends on the properties of the acrylic fiber bundle as the fiber bundle to be heat-treated, the heat history to be given to the acrylic fiber bundle, the wind direction in the heating furnace, and the air volume ( Wind speed), hot air temperature, etc. It is to be noted that a partition can be provided for each stage from the viewpoint of rectifying effect and ensuring safety.

The most important parameter in controlling the oxidizing reaction of the fiber bundle to be heat-treated is to remove the heat storage in the fiber bundle generated by the exothermic reaction. Problems such as breakage of bundles and fusion between single yarns occur.

That is, by giving uniform wind speed and temperature to all of a large number of fiber bundles forming a fiber bundle sheet, the above-mentioned problem can be avoided and the process stability can be improved. it can. For this purpose, it is only necessary to reduce the amount of the fiber bundle to be heat-treated into the oxidizing furnace, to eliminate the heat storage in the fiber bundle caused by the exothermic reaction, and to eliminate the mutual interference due to the fluttering of the fiber bundle to be heat-treated. However, this comes at the cost of process productivity.

[0023] However, the oxidization-resistant fiber bundle sheet in which a large number of acrylic fiber bundles are aligned is subjected to a continuous heat treatment while running in an oxidization furnace of a hot air circulation type convection heating furnace. The surface occupancy of the fiber bundle sheet introduced into the oxidizing furnace with respect to the bottom surface is set to 36 to 65%, the wind direction in the oxidizing furnace is perpendicular to the fiber bundle sheet, and the wind speed is set to 0. By setting the tension of the acrylic fiber bundle traveling in the flameproofing furnace to 0.5 to 2.5 g / tex, the quality of the flameproofed fiber of high quality can be increased to 3 to 1.5 m / sec. It can be obtained while maintaining productivity.

In addition, the surface occupancy of the fiber bundle sheet introduced into the oxidation furnace with respect to the bottom surface of the oxidation furnace is set to 36 to 65%, and the wind direction in the oxidation furnace is adjusted with respect to the fiber bundle sheet. And make the wind speed 1.5 to 5 m / sec.
In addition, by carrying out the process tension of the acrylic fiber bundle traveling in the oxidizing furnace at a process tension of 0.5 to 2.5 g / tex, high-quality oxidizing fibers can be obtained while maintaining high process productivity. be able to.

When the surface occupancy of the fiber bundle sheet running in the oxidizing furnace is less than 36%, the process stability is further improved. However, a decrease in the amount of the fiber bundle to be heat-treated consisting of an acrylic fiber bundle into the oxidizing furnace, and an increase in the utility cost significantly reduce the process productivity, thereby increasing the manufacturing cost of the oxidizing fiber, As a result, the production cost of the carbon fiber is increased.

When the surface occupancy of the fiber bundle sheet running in the oxidizing furnace is higher than 65%, the process stability is sharply reduced, and the generation of smoke due to excessive heat storage, yarn breakage, and singularity occur. Since the fusion occurs between the yarns, it is difficult to obtain a high-quality flame-resistant fiber, which makes it impossible to obtain a high-quality carbon fiber, and lowers the yield to lower the process productivity.

Further, in the continuous heat treatment method for the acrylic fiber bundle of the present invention, a hot air circulation type convection heating furnace is used as a flame-proofing furnace, and the fiber bundle to be heat-treated is heated by a convection heating method. By heating the acrylic fiber bundle which is the fiber bundle to be heat-treated, the oxidation reaction and the cyclization reaction are promoted, and at the same time, the heat storage of the fiber bundle to be heat-treated can be effectively removed.

In the continuous heat treatment method for an acrylic fiber bundle according to the present invention, when the wind speed in an oxidation-resistant furnace comprising a hot air circulation type convection heating furnace is set such that the wind direction is perpendicular to the fiber bundle sheet, When it is in the range of 0.3 m / sec to 1.5 m / sec, and when the wind direction is parallel to the fiber bundle sheet, it should be in the range of 1.5 m / sec to 5 m / sec. is necessary.

That is, when the wind direction is perpendicular to a fiber bundle sheet in which a large number of acrylic fiber bundles as heat treatment fiber bundles are aligned, the wind speed is 0.3 m / sec.
When the direction is set to be less than or the direction of the wind is made parallel to a fiber bundle sheet in which a large number of acrylic fiber bundles as heat treatment fiber bundles are aligned, the wind speed is 1.5 m / sec.
When it is less than c, the heat storage effect of the heat storage of the fiber bundle to be heat-treated by the wind in the oxidizing furnace cannot be obtained, and smoke due to poor heat removal is likely to occur.

When the wind direction is perpendicular to a fiber bundle sheet in which a large number of acrylic fiber bundles to be heat-treated are aligned, the wind speed exceeds 1.5 m / sec, or When the wind direction is parallel to a fiber bundle sheet in which a large number of acrylic fiber bundles as heat-treated fiber bundles are aligned, if the wind speed exceeds 5 m / sec, the wind in the oxidizing furnace The flutter of the fiber bundle due to the above becomes large, and a single yarn breakage occurs due to the contact between adjacent fiber bundles on a plane parallel to the bottom surface of the oxidizing furnace, so that the oxidizing fiber with many fluffs is easily obtained.

Further, the process tension of the acrylic fiber bundle traveling in the flame stabilization furnace comprising the hot air circulation type convection heating furnace is set to 0.5.
If the ratio is less than g / tex, single yarn breakage due to flapping of the fiber bundle to be heat-treated or fusion between single yarns due to contact between adjacent fiber bundles in a plane parallel to the bottom surface of the oxidizing furnace. And the fiber bundle shape regulated by the roller may not be maintained. 2.5g / tex
If it is higher than this, not only the process tension tends to be reduced, but also the durability of the fiber bundle to be heat-treated against physical contact at the entrance and exit of the oxidation furnace becomes weak.

In the method of the present invention, in which the fiber bundle to be heat-treated consisting of the acrylic fiber bundle is subjected to continuous heat treatment to obtain oxidized fiber, the means for regulating the running path of the fiber bundle to be heat-treated and the tow width include: For example, a guide can be used and is not subject to any restrictions, but it is most preferred to use a grooved roller. The cross-sectional shape of the groove of this groove roller may be any of a flat bottom type as shown in FIG. 1, a round bottom type as shown in FIG. 2, and a wave bottom type as shown in FIG.
The groove shape and the groove pitch are appropriately determined in consideration of the total fineness of the fiber bundle to be heat-treated and the problems in manufacturing the roller.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The concrete constitution of the continuous heat treatment method for an acrylic fiber bundle of the present invention will be described below based on examples. In addition, the fiber bundle to be heat-treated and the stabilization furnace used in each of Examples and Comparative Examples are as follows. Fiber bundle to be heat treated: Acrylic fiber bundle with single yarn tex 0.13 made of acrylic copolymer fiber containing acrylonitrile 96 mol% Flame-proofing furnace: Hot air circulation type convection heating furnace

Example 1 In FIGS. 4 and 5, the effective furnace length L ₁ : 10 m, the effective furnace width L ₂ : 1 m, the wind direction in the furnace: perpendicular to the fiber bundle sheet, the furnace temperature: 230 ° C. , Wind speed in the furnace: 0.6m /
The number of filaments is 36,000 in the oxidation furnace 1 for 2 sec.
The heat-treated fiber bundle S formed by 120 fiber bundles S to be heat-treated was subjected to a continuous heat treatment in which the fiber bundle sheet material 2 was run for three reciprocating halves to obtain the oxidized fiber 3. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is 43%.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle S to be heat-treated per fiber introduced into the oxidizing furnace 1 is adjusted to 3.6 m by the groove roller 4.
m, the pitch between the fiber bundles S, that is, the heat treatment adjacent to the center of the fiber bundle S to be introduced into the oxidization furnace 1 in parallel with a plane parallel to the bottom surface of the oxidization furnace. The distance to the center of the fiber bundle S was regulated to 8.0 mm.
Further, the process tension of the acrylic fiber bundle traveling in the oxidizing furnace was set to 1.4 g / tex (6 kg per fiber).

During the continuous heat treatment step of the acrylic fiber bundle, stable continuous operation was possible without generation of smoke due to runaway reaction. Further, there is no breakage of single yarn due to contact between adjacent fiber bundles in the oxidizing furnace, no fusion between single yarns, no contamination of the fiber surface, etc. And a flame-resistant fiber having a low level of resistance was obtained. The degree of increase in the oxidized density of the acrylic fiber by this continuous heat treatment is 0.06 g.
/ Cm ³ / 17min. Met.

Example 2 Effective furnace length: 14 m, effective furnace width: 1 m, wind direction in furnace: perpendicular to fiber bundle sheet, furnace temperature: 240 ° C., wind speed in furnace: 1.0 m / sec The acryl-based fiber bundle was subjected to continuous heat treatment through a fiber bundle sheet made of 200 fiber bundles to be heat-treated having a number of filaments of 12,000 in the flame-resistant furnace. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidizing furnace with respect to the bottom surface of the oxidizing furnace is 40%.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat-treated per fiber is 2.0 mm and the pitch between the fiber bundles is 5.
0 mm, and the process tension of the acrylic fiber bundle running in the oxidizing furnace is 0.8 g / tex (1.2 per fiber).
kg).

During the continuous heat treatment step of the acrylic fiber bundle, stable continuous operation was possible without generation of smoke due to runaway reaction. Also, there is no single yarn breakage due to contact between adjacent fiber bundles, fusion between single yarns, contamination of the fiber surface, etc.
Oxidized fibers with less processing unevenness in the width direction of the fiber bundle sheet and processing unevenness of the single yarn were obtained. Oxidization density increase of the acrylic fiber according to the continuous heat treatment is 0.06g / cm ^3/1
5 min. Met.

Example 3 Effective furnace length: 10 m, effective furnace width: 1 m, wind direction in the furnace: perpendicular to the fiber bundle sheet, furnace temperature: 220 ° C., wind speed in the furnace: 0.5 m / sec The acryl-based fiber bundle was subjected to continuous heat treatment by passing a fiber bundle sheet made of 60 fiber bundles to be heat-treated with 72,000 filaments into the flame-resistant furnace of No. 1 to obtain flame-resistant fiber. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidizing furnace with respect to the bottom surface of the oxidizing furnace is 48%.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat-treated is 8.0 mm and the pitch between the fiber bundles is 1 by a groove roller.
6.0 mm, and the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is 1.4 g / tex (1 per fiber).
2 kg).

During the continuous heat treatment step of the acrylic fiber bundle, stable continuous operation was possible without generation of smoke due to runaway reaction. Also, there is no single yarn breakage due to contact between adjacent fiber bundles, fusion between single yarns, contamination of the fiber surface, etc.
Oxidized fibers with less processing unevenness in the width direction of the fiber bundle sheet and processing unevenness of the single yarn were obtained. Oxidization density increase of the acrylic fiber according to the continuous heat treatment is 0.06g / cm ^3/2
4 min. Met.

Example 4 Effective furnace length: 14 m, effective furnace width: 1.5 m, wind direction in the furnace: parallel to the fiber bundle sheet, furnace temperature: 220
A continuous heat treatment of an acrylic fiber bundle is carried out by passing a fiber bundle sheet made of 90 pieces of a fiber bundle to be heat treated having 72,000 filaments into an oxidizing furnace having an air temperature of 2.8 m / sec. Thus, an oxidized fiber was obtained. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidizing furnace with respect to the bottom surface of the oxidizing furnace is 48%.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat-treated is 8.0 mm and the pitch between the fiber bundles is 1 by a groove roller.
6.0 mm, and the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is 1.0 g / tex (9 per fiber).
kg).

During the continuous heat treatment step of the acrylic fiber bundle, stable continuous operation was possible without generation of smoke due to runaway reaction. In addition, oxidized fibers without breakage of single yarn due to contact between adjacent fiber bundles, fusion between single yarns, and contamination of the fiber surface were obtained. Although some single yarn processing unevenness was confirmed, the processing unevenness in the width direction of the fiber bundle sheet was small,
A fully satisfactory flame resistant fiber was obtained. The degree of increase in the oxidized density of the acrylic fiber by this continuous heat treatment is 0.06 g.
/ Cm ³ / 20min. Met.

Example 5 Effective furnace length: 14 m, effective furnace width: 1.5 m, wind direction in the furnace: parallel to the fiber bundle sheet, furnace temperature: 215
A continuous heat treatment of an acrylic fiber bundle is carried out by passing a fiber bundle sheet made of 90 pieces of a fiber bundle to be heat treated having 72,000 filaments into an oxidizing furnace having a furnace temperature of 2.8 m / sec and a wind speed of 2.8 m / sec. As a result, an oxidized fiber was obtained. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is 56%.

In the above-described continuous heat treatment of the acrylic fiber bundle, one flat roller and a comb guide are used.
The width of the fiber bundle to be heat-treated is regulated to 10.5 mm, the pitch between the fiber bundles is regulated to 17.0 mm, and the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is 1.4 g / te.
x (2 kg per line).

During the continuous heat treatment step of the acrylic fiber bundle, stable continuous operation was possible without generation of smoke due to runaway reaction. In addition, oxidized fibers without breakage of single yarn due to contact between adjacent fiber bundles, fusion between single yarns, and contamination of the fiber surface were obtained. Although some single yarn processing unevenness was confirmed, the processing unevenness in the width direction of the fiber bundle sheet was small,
A fully satisfactory flame resistant fiber was obtained. The degree of increase in the oxidized density of the acrylic fiber by this continuous heat treatment is 0.06 g.
/ Cm ³ / 27min. Met.

Comparative Example 1 Effective furnace length: 10 m, effective furnace width: 1 m, wind direction in the furnace: perpendicular to the fiber bundle sheet, furnace temperature: 230 ° C., wind speed in the furnace: 0.6 m / sec The acryl-based fiber bundle was subjected to continuous heat treatment through a fiber bundle sheet made of fifty fiber bundles to be heat-treated having 36,000 filaments in the oxidizing furnace. At this time, the area occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is 30%.
It is.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat-treated per fiber is 6.0 mm and the pitch between the fiber bundles is 1 by a groove roller.
It is regulated to 4.0 mm, and the process tension of the acrylic fiber bundle traveling in the oxidation furnace is 1.4 g / tex (6 per fiber).
kg).

During the continuous heat treatment step of the acrylic fiber bundle, stable continuous operation was possible without generation of smoke due to runaway reaction. Also, there is no single yarn breakage due to contact between adjacent fiber bundles, fusion between single yarns, contamination of the fiber surface, etc.
Oxidized fibers with less processing unevenness in the width direction of the fiber bundle sheet and processing unevenness of the single yarn were obtained. Oxidization density increase of the acrylic fiber according to the continuous heat treatment is 0.06g / cm ^3/1
7 min. Thus, the decrease in the surface occupancy of the fiber bundle sheet introduced into the oxidizing furnace relative to the bottom surface of the oxidizing furnace could not be covered by the increase in the oxidizing resistance of the acrylic fibers.

Comparative Example 2 Effective furnace length: 10 m, effective furnace width: 1 m, wind direction in the furnace: perpendicular to the fiber bundle sheet, furnace temperature: 230 ° C., wind speed in the furnace: 0.6 m / sec Acrylic fiber bundles were subjected to continuous heat treatment through a fiber bundle sheet made of 120 fiber bundles to be heat-treated having 36,000 filaments in the oxidizing furnace. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is 72.
%.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat-treated per groove is 6.0 mm and the pitch between the fiber bundles is 8.
0 mm, and the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is 1.4 g / tex (6 k / tube).
g).

During the continuous heat treatment of the acrylic fiber bundle, single yarn breakage occurs frequently due to contact between adjacent fiber bundles on a plane parallel to the bottom surface of the oxidizing furnace, An oxidized fiber with many yarn treatment spots was obtained. Oxidization density increase of the acrylic fiber according to the continuous heat treatment is 0.06g / cm ³ / 17min. And the process stability was very poor.

Comparative Example 3 Effective furnace length: 14 m, effective furnace width: 1 m, wind direction in the furnace: perpendicular to the fiber bundle sheet, furnace temperature: 240 ° C., wind speed in the furnace: 1.0 m / sec Acrylic fiber bundles were subjected to continuous heat treatment through a fiber bundle sheet consisting of 200 fiber bundles to be heat-treated having 12,000 filaments in the oxidizing furnace. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidizing furnace with respect to the bottom surface of the oxidizing furnace is 40.
%.

In the above-described continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat-treated per fiber is 2.0 mm and the pitch between the fiber bundles is 5.
0 mm, and the process tension of the acrylic fiber bundle running in the oxidizing furnace is 0.3 g / tex (0.5 g / tex).
kg).

During the above-mentioned continuous heat treatment of the acrylic fiber bundle, the bundle was broken due to the contact between adjacent fiber bundles on a plane parallel to the bottom surface of the oxidizing furnace. The degree of increase in the oxidized density of the acrylic fiber by this continuous heat treatment is 0.06 g.
/ Cm ³ / 15min. And the process stability was very poor.

Comparative Example 4 Effective furnace length: 14 m, effective furnace width: 1 m, wind direction in the furnace: perpendicular to the fiber bundle sheet, furnace temperature: 240 ° C., wind speed in the furnace: 2.0 m / sec Acrylic fiber bundles were subjected to continuous heat treatment through a fiber bundle sheet consisting of 200 fiber bundles to be heat-treated having 12,000 filaments in the oxidizing furnace. At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidizing furnace with respect to the bottom surface of the oxidizing furnace is 40.
%.

In the above-mentioned continuous heat treatment of the acrylic fiber bundle, the width of the fiber bundle to be heat treated per fiber is 2.0 mm and the pitch between the fiber bundles is 5.
0 mm, and the process tension of the acrylic fiber bundle running in the oxidizing furnace is 0.3 g / tex (0.5 g / tex).
kg).

During the continuous heat treatment step of the acrylic fiber bundle, no smoke was generated due to the runaway reaction.
The flapping of the fiber bundle composed of the wind in the oxidizing furnace is large, and the single fiber break occurs due to the contact between adjacent fiber bundles on the surface parallel to the bottom surface of the oxidizing furnace, and the oxidizing fiber with many fluff is obtained. Was. Oxidization density increase of the acrylic fiber according to the continuous heat treatment is 0.06g / cm ³ / 15min. Met.

Comparative Example 5 Effective furnace length: 14 m, effective furnace width: 1.5 m, wind direction in the furnace: parallel to the fiber bundle sheet, furnace temperature: 215
A continuous heat treatment of an acrylic fiber bundle was performed by passing a fiber bundle sheet made of 90 pieces of a fiber bundle to be heat treated having 72,000 filaments into an oxidation-resistant furnace having a furnace temperature of 1.0 ° C. and a wind speed of 1.0 m / sec. . At this time, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is 56%.

In the above-described continuous heat treatment of the acrylic fiber bundle, one flat roller and a comb guide are used.
The width of the fiber bundle to be heat-treated is regulated to 10.5 mm, the pitch between the fiber bundles is regulated to 17.0 mm, and the process tension of the acrylic fiber bundle traveling in the oxidizing furnace is 1.4 g / te.
x (2.0 kg per line).

During the continuous heat treatment step of the acrylic fiber bundle, smoke was generated due to poor heat removal.
Further, oxidization density increase of the acrylic fiber by the heat treatment is 0.06g / cm ³ / 27min. Met.

In the above Examples and Comparative Examples, the surface occupancy, the process productivity, and the visual properties of the obtained fiber oxidized fibers with respect to the bottom surface of the gas oxidized furnace with respect to the bottom surface of the gas oxidized furnace were measured. The results are shown in Table 1.

[0065]

[Table 1]

[0066]

According to the method for continuously heat-treating acrylic fiber bundles of the present invention, it is possible to efficiently produce high-quality oxidized fibers, which makes it possible to produce high-quality carbon fibers. In addition, the cost for producing carbon fibers can be reduced.

[Brief description of the drawings]

FIG. 1 is a cut end view showing a schematic shape of a groove of a flat bottom type groove roll.

FIG. 2 is a cut end view showing a schematic shape of a groove of a round bottom type groove roll.

FIG. 3 is a cut end view showing a schematic shape of a groove of a corrugated bottom groove roll.

FIG. 4 is a schematic vertical sectional view of the oxidizing furnace showing a state of a fiber bundle sheet running in the oxidizing furnace.

FIG. 5 is a schematic cross-sectional view of the oxidizing furnace of FIG. 4 taken along line XY.

[Explanation of symbols]

1 ··· Oxidation furnace 2 ··· Fiber bundle sheet 3 ··· Oxidation resistant fiber 4 ··· Groove roller S ··· Heat treated fiber bundle L ₁ · Effective furnace length L ₂ ··· effective furnace width

Claims (3)

[Claims] 1. An acrylic fiber fiber sheet made by heat-treating a fiber bundle sheet in which a large number of acrylic fiber bundles are aligned in a flame stabilization furnace comprising a hot air circulation type convection heating furnace. In the continuous heat treatment method for a fiber bundle, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is set to 36 to 65%,
The wind direction in the oxidizing furnace is perpendicular to the fiber bundle sheet, the wind speed is 0.3 to 1.5 m / sec, and the process tension of the acrylic fiber bundle running in the oxidizing furnace is 0. A method for continuously heat-treating an acrylic fiber bundle, wherein the heat treatment is performed at 0.5 to 2.5 g / tex. 2. An acrylic fiber fiber sheet obtained by heat-treating a fiber bundle sheet obtained by aligning a large number of acrylic fiber bundles in a flame stabilization furnace comprising a hot air circulation type convection heating furnace. In the continuous heat treatment method for a fiber bundle, the surface occupancy of the fiber bundle sheet-like material introduced into the oxidization furnace with respect to the bottom surface of the oxidization furnace is set to 36 to 65%,
The wind direction in the oxidizing furnace is parallel to the fiber bundle sheet, the wind speed is 1.5 to 5 m / sec, and the process tension of the acrylic fiber bundle running in the oxidizing furnace is 0.5. A method for continuously heat-treating an acrylic fiber bundle, wherein the heat treatment is performed at 2.5 g / tex. 3. The continuous heat treatment method for an acrylic fiber bundle according to claim 1, wherein the running path of the fiber bundle to be heat treated is regulated by a groove roller.