JPS61174423A - Production of flameproofed fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a method for producing a flame-resistant fiber bundle.

<Prior Art> The flame-resistant fiber in the present invention refers to a fiber that does not catch fire or melt even when exposed to a pine flame in an air atmosphere.

Such flame-resistant fibers, which are obtained by heating organic polymer fibers such as polyacrylonitrile fibers, cellulose fibers, pitch-based fibers, and lignin-based fibers, in an oxidizing atmosphere are currently known for their flame resistance and heat resistance. Due to its unique properties, it is being used in a wide range of applications, including firefighting uniforms, fire prevention products, and insulation materials.

To obtain flame-resistant fibers from organic polymer fibers, such as polyacrylonitrile fibers, the fibers are heated in an oxidizing atmosphere for 2 hours.
This is achieved by heating and firing at a temperature of 00 to 400°C.

Examples of the oxidizing atmosphere used at this time include air, nitrogen oxide, sulfur dioxide gas, halides, water vapor, etc., but air is generally used the most due to its economical efficiency.

Conventionally, flame-resistant fibers have been known as intermediate products for carbon products, and various proposals have been made regarding methods for producing them. For example, there is a method using an oxidizing atmosphere furnace, as shown in the method of German Publication No. 2.026,019. A schematic diagram of the apparatus is shown in FIG. In Fig. 1, organic polymer fiber bundle 1
is guided by guide rollers 4 in an oxidizing atmosphere furnace 2, passes through a large number of concave holes 2, and is heat-treated.

However, when polyacrylonitrile fibers are oxidized in air, an exothermic reaction occurs, so when the fiber bundle is treated in an oxidizing atmosphere furnace, the heat generated is released to the outside of the fiber bundle as the thickness of the fiber bundle increases. The fibers become difficult to absorb and accumulate inside, resulting in a runaway reaction and breakage of the fiber bundle. Therefore, in order to prevent a runaway reaction, the fiber bundle with a so or ooo denier should be
There is a method of making intermittent contact with the surface of a heating element, as shown in No. 53-21, 396. This utilizes the natural principle that heat transfer between solids and solids is much larger than that between gases and solids, making it easier to suppress runaway reactions that are difficult in oxidizing atmosphere furnaces, and also improve the oxidation reaction rate. This is the method we are trying to achieve. Using this method, it appears possible to produce flame-resistant fibers using thick fiber bundles. However, a drawback of this method is that when the thickness of the fiber bundle increases, reaction spots occur in the thickness direction. This is because the oxidation reaction rapidly progresses on the surface of the fiber bundle that contacts the surface of the heating element, but the rate of oxidation reaction inside the fiber bundle that does not contact the surface of the heating element is lower than that on the surface. In our study,
In the case of polyacrylonitrile fiber bundles, the width of the fiber bundle without causing reaction spots in the thickness direction was required to be 45 mm or more in so and ooo deniers, and 0.2 mm or less in terms of thickness. In addition, as another method for eliminating this reaction spot, for example, using a plurality of heating roller groups 3 as shown in FIG. Although it is possible to do this, it requires a long time to produce a product with no quality problems, which is disadvantageous from an industrial perspective.

<Problems to be Solved by the Invention> As mentioned above, when organic polymer fiber bundles are oxidized using conventional techniques, there is a limit to the thickness of the fiber bundles, and therefore the productivity of flame-resistant fiber bundles is limited. It is impossible to improve ♂. Furthermore, in the conventional technology, when oxidizing thick organic polymer fiber bundles, it is impossible to prevent runaway reactions and produce flame-resistant fibers in a short time without causing oxidation reaction spots. There are problems.

The present invention solves the problems of the prior art described above, and
Even if a thick organic polymer fiber bundle is directly fed to the oxidation reaction without expanding its width, a runaway reaction will not occur, oxidation reaction spots will not occur, and the fiber bundle will be flame-resistant in a short time. The purpose of the present invention is to provide a highly productive method for producing flame-resistant fibers that can be converted into flame-resistant fibers.

<Means for Solving the Problems> An object of the present invention is to oxidize an organic polymer fiber bundle to obtain a flame-resistant fiber, by oxidizing the fiber bundle for 20 minutes in an oxidizing atmosphere.
After heat treatment by contacting with a heating element at 0 to 350°C, 2
A method for producing flame-resistant fibers characterized by heat treatment in an oxidizing atmosphere at 00 to 350°C (hereinafter referred to as the first production method)
achieved by.

The above-mentioned object of the present invention is characterized in that, following the heat treatment in an oxidizing atmosphere at 200-350°C, the organic polymer fiber bundle is further heat-treated by contacting with a heating element at 250-400°C in an oxidizing atmosphere. This is achieved by the method for producing flame-resistant fibers (hereinafter referred to as the second production method). In this second production method, in addition to the first production method, heat treatment by contact with a heating body is performed, so that flame-resistant fibers can be produced in a shorter time.

In the present invention, the organic polymer fiber bundle refers to a fiber bundle made of an organic polymer such as polyacrylonitrile, cellulose, pitch, or lignin.

The torque denier and width of the fiber bundle are not particularly limited. Preferably, for example, in the case of polyacrylonitrile fibers, the size and width are comparable to commercially available fiber bundles, and the denier is 100,000 to 1,000,000.
A width of 10 to 50 cm is good. More preferably 300.0
00~600.000 denier and width 15~30cm are good.

The oxidizing atmosphere in the present invention refers to oxygen, nitrogen oxides,
A gaseous atmosphere containing sulfur oxides, halides, water vapor, etc. Generally, air is suitable because of its economy and simplicity.

The heating body in the present invention may be various conventionally known heating rollers, heating plates, etc., and is not particularly limited. - An example is the group of heating rollers 3 shown in FIG. The temperature of the heating element is a temperature at which the oxidation reaction proceeds rapidly and at which adhesion and adhesion of fibers do not occur during the reaction, which is achieved at 200 to 350°C. If the temperature of the heating element is below 200°C, the oxidation reaction will be very slow, and if it is above 350°C, the occurrence of adhesion will become noticeable.

The preferred temperature range of the heating body is 220 to 320°C, more preferably 240 to 300°C. Further, when using a group of heating rollers as shown in FIG. 2, the temperature may be set in multiple stages.

According to the method of the present invention, a flame-resistant fiber can be produced by oxidizing an organic polymer fiber bundle to some extent in an oxidizing atmosphere using a heating element and then further heating and oxidizing it in an oxidizing atmosphere. The degree of oxidation achieved by the heating element must be such that runaway reactions are unlikely to occur during the subsequent heat treatment in an oxidizing atmosphere. For example, in the case of polyacrylonitrile fibers, if the degree of oxidation is expressed as C, I, the average C of the surface area of the fiber bundle that comes into contact with the heating element and the inside of the fiber bundle that is not exposed to the surface.
It is sufficient to set 0■ to 0.2 or more. Preferably 0.30
A value of 0.42 or less is preferable. When a polyacrylonitrile fiber bundle with a total of 500.000 deniers, a width of 20 cm, and a thickness of 5 mm is heat-treated by a group of heating rollers 3 as shown in FIG. 2, the fiber bundle on the heating rollers 3 has a width of 20 cm and a thickness of 0.5 m. m. In this case, oxidizing flame will naturally appear on the surface and inside of the fiber bundle if the heated roller treatment is carried out for a short time, but the heated roller treatment should be continued until the average C and I of both are 0.2 or more. .

C and I mentioned here are Cabonization I
It is an abbreviation for ndex, and is determined as follows [inner circle, 2θ of the X-ray scattering intensity curve obtained by performing xlt3 measurement without rotating the sample around the incident X-ray axis.
It is calculated from the scattering intensity II at =17° and the scattering intensity I2 at 2θ=25.5° (both values are values obtained by subtracting the value of air scattering) using the following equation.

(2) C and I of the flame-resistant fiber in the present invention are 0.5 or more.

The width and thickness of the organic polymer fiber bundle during heating body treatment are not particularly limited. Industrially, the width of organic polymer fibers commonly used may be used as is, and the thickness may be determined as desired, that is, the thickness necessarily determined from the width based on the torque denier. Practically preferred width is 50cm
Below, the thickness is preferably 0.3 mm or more and 5 mm or less.

The organic polymer fiber bundle that has been heat-treated with a heating element is then heat-treated in an oxidizing atmosphere. This is to impart a certain degree of heat resistance and reduce the possibility of runaway reactions during subsequent heat treatment in an oxidizing atmosphere. Therefore, it does not matter if there are reaction spots in the fiber bundle after the heating body heat treatment. This is because these reaction spots can be improved in a short time by heating in an oxidizing atmosphere. The significance of the latter heating in an oxidizing atmosphere is that
Eliminates the oxidation reaction site in the previous stage and advances the actual oxidation degree,
Moreover, the purpose is to produce flame-resistant fibers of good quality in a short time. Therefore, the heat treatment by the first-stage heating element and the second-stage heat treatment by the oxidizing atmosphere are integrated, and if either the first stage or the second stage is missing, the object of the present invention cannot be achieved as in the prior art. is not possible. Also, the first part,
Even if the order of the subsequent stages is changed, it is impossible to prevent runaway reactions or eliminate reaction spots.

The heating in the oxidizing atmosphere in the latter stage of the present invention may be performed in a conventionally known tunnel furnace or net conveyor set furnace as shown in FIG. 1, and is not particularly limited. Although the width of the organic polymer fiber bundle supplied for heating in an oxidizing atmosphere is not particularly limited, it is practically preferred that the width is the same as the width at the time of the heating body treatment in the previous stage. The heating temperature is
In order to allow the oxidation reaction to proceed quickly, the lower limit is 200
℃, while adhesion is prevented, and although the oxidation reaction has progressed to some extent, there is still a possibility of a runaway reaction, so it is better to set the upper limit to 350℃. Preferably 210-300°C, more preferably 220-300°C
280"C is preferable. Also, the temperature may be applied in multiple stages.

Furthermore, the present inventors have discovered that once the reaction spots are eliminated by heating in an oxidizing atmosphere, the reaction spots never appear again. Therefore, as a result of extensive research, we found that the oxidation reaction caused by a heating element is faster than the oxidation reaction caused by heating in an oxidizing atmosphere due to heat transfer between solids.
Following the heat treatment in an oxidizing atmosphere at 200 to 350°C (hereinafter referred to as second stage heat treatment), the organic polymer fiber bundle is further heat treated in an oxidizing atmosphere by contacting with a heating element at 250 to 400°C (hereinafter referred to as second stage heat treatment). The above-mentioned second manufacturing method, which is characterized by a third stage heat treatment, has been achieved.

The conditions of the organic polymer fiber bundle to be treated in the second production method, the heating body used, and the heat treatment conditions of the first heat treatment by contact with the heating body (hereinafter referred to as the first stage heat treatment) are carried out in accordance with the first production method. good. For the oxidizing atmosphere furnace heating in the second stage heat treatment, the equipment to be used, the oxidizing atmosphere, the width and thickness of the organic polymer fiber bundle, and the temperature range conditions may be determined according to the conditions of the first manufacturing method. However, in the case of polyacrylonitrile fibers, the degree of oxidation achieved by atmospheric heating is
C, I is 0.42 or more, preferably 0.42 or more 0.4
It is advisable to set the conditions so that the value is 8 or less. This level of C
, I, the reaction spots caused by the first stage heating element are eliminated.

The organic polymer fiber bundle heat-treated in an oxidizing atmosphere is further supplied to a heating element heated in an oxidizing atmosphere in a third stage heat treatment. The temperature of the heating element at this time is set at a lower limit of 250° C. to allow the reaction to proceed rapidly, and an upper limit of 400° C. to prevent adhesion of the fiber bundle. There are no particular limitations on the width and thickness of the fiber bundle during the third-stage heat treatment, but for practical purposes, the width that is subjected to the oxidizing atmosphere heating in the second-stage heat treatment is preferred, and the thickness may be determined as desired. However, the width is 50cm
The thickness is preferably 0.3 mm or more and 5 mm or less.

<Example> The present invention will be specifically explained below using Examples.

Example 1 A continuous oxidation reaction apparatus consisting of a group of heating rollers 3 and a tunnel-type oxidizing atmosphere furnace 2 as shown in FIG. A flame-resistant fiber was obtained using the method. Air was used as the oxidizing atmosphere.

The surface temperature of the heating roller was maintained at 280°C. The width of the fiber bundle on the surface of the heating roller was 20 cm and the thickness was 0.5 mm.

The fiber bundle after the heating roller treatment has surface portions C, IO, 36
, internal 0.27 and spots were seen, but the average C and I were 0.
It was 33. The residence time on the heated roller was 5 minutes.

The oxidizing atmosphere furnace treatment was performed at a temperature of 250°C and a residence time of 24 minutes.
The test was conducted under the condition that the fiber bundle width was 20 cm.

The obtained fiber bundle had no reaction spots and C,I=0.53.
Even when exposed to pine flame, it did not catch fire.

Additionally, the same polyacrylonitrile fiber bundle as in Example 1 was treated using the same continuous oxidation reactor as in Example 1. The heating roller conditions were the same as in Example 1, but the tunnel furnace was oxidized at a temperature of 250° C., a residence time of 8 minutes, and a fiber bundle width of 20 cm. No reaction spots were observed in the obtained fiber bundle. The arrival C,1 was 0.43.

This fiber bundle is further heated using air as an oxidizing atmosphere.
When treated for 3 minutes with a group of heating rollers kept at 20℃,
A flame-resistant fiber bundle with C,I=0.54 and no spots was obtained.

Comparative Example 1 The same polyacrylonitrile fiber bundle as in Example 1 was
When the yarn was passed through a tunnel furnace in an air atmosphere at a temperature of 220° C., a runaway reaction occurred and the yarn bundle was cut.

Comparative Example 2 The same polyacrylonitrile fiber bundle as in Example 1 was
The oxidation treatment was carried out in an air atmosphere using a group of heating rollers at a temperature of ~330°C. At this time, the fiber bundle on the roller had a width of 20 cm and a thickness of 0.5 mm. It took one hour to obtain a flame-resistant fiber bundle with C1I=0.53 and no spots.

Example 3 Total 2 of pinch fiber bundle spun using petroleum residue
A yarn bundle of 00,000 D and a width of 80 m0 was oxidized using an apparatus as shown in FIG. Air was used as the oxidizing atmosphere.

The surface temperature of the heating roller was maintained at 270°C. The fiber bundle on the heating roller had a width of 8 cm and a thickness of 3.5 mm. Reaction spots were observed in the fiber bundle after the heating roller treatment.

The oxidizing atmosphere furnace treatment was performed at a temperature of 250°C and a fiber bundle width of 20cm.
It was conducted under the following conditions. The obtained fiber bundle had no reaction spots, and a good flame-resistant fiber bundle that did not melt even when exposed to a pine flame was obtained.

<Effects of the Invention> Since the method for producing flame-resistant fibers of the present invention is configured as described above, a thick organic polymer fiber bundle can be directly fed to the oxidation reaction without increasing its width. In addition, during the heat treatment, flame-resistant fibers can be produced in a short time without causing oxidation reaction spots.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional oxidizing atmosphere furnace, FIG. 2 is a cross-sectional view of a conventional heating body oxidizer shown as an example, and FIG. 3 is a cross-sectional view showing an example of an apparatus suitable for carrying out the present invention. It is. 1.-Fiber bundle, 2-oxidizing atmosphere furnace, 3-heating roller, 4-transfer roller.

Claims (1)

[Claims] 1. When oxidizing an organic polymer fiber bundle to obtain a flame-resistant fiber, the fiber bundle is heat-treated by contacting with a heating element at 200 to 350°C in an oxidizing atmosphere, and then heated to 200 to 350°C. A method for producing flame-resistant fibers, characterized by heat treatment in an oxidizing atmosphere at 350°C. 2. When oxidizing an organic polymer fiber bundle to obtain a flame-resistant fiber, the fiber bundle is heat-treated in an oxidizing atmosphere by contacting with a heating element at a temperature of 200 to 350°C, and then heated in an oxidizing atmosphere of 200 to 350°C. heat treated in an oxidizing atmosphere, and further heated in an oxidizing atmosphere
A method for producing flame-resistant fibers, which comprises heat-treating the fibers by contacting them with a heating element at 50 to 400°C.