JPS6142006B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing carbon fiber. More specifically, the present invention relates to a method for producing carbon fibers of high quality, particularly high mechanical properties, by stabilizing the operation when firing organic polymer fiber threads. Due to its excellent mechanical, chemical, and electrical properties, carbon fiber is widely used in a variety of applications, including aerospace structural materials such as aircraft and rockets, and sporting goods such as tennis rackets, golf shafts, and fishing rods. Furthermore, it is expected to be used in fields such as transportation machinery applications such as ships and automobiles. Cellulose fibers, acrylic fibers, polyvinyl alcohol fibers, etc. are used as fiber materials that are raw materials for manufacturing such carbon fibers, that is, precursors, and these precursors are flame-resistant treated in an oxidizing atmosphere at 200 to 400°C. It is well known that the carbon fiber is then converted into carbon fiber through a carbonization process at a high temperature of at least 800°C in an inert atmosphere. The precursor, which is made flame resistant and then carbonized under such severe conditions, tends to accumulate local heat during firing, especially during the flame resistant process, which may cause fusion between single yarns or cause the precursor to become carbonized. The raw oil applied to the fiber turns into tar, causing fuzz and single fiber breakage, which not only impairs stable operation, but also affects the quality of the carbon fiber obtained by heat treatment in an inert atmosphere, especially There was a problem that mechanical properties were impaired. Various attempts have been made to avoid such problems. For example, in Japanese Patent Application Laid-Open No. 148227/1984, when an acrylic precursor impregnated with a silicone compound is treated to make it flame resistant, the single fibers do not combine with each other during the flame resistant process. It is said that the silicone compound prevents adhesion or fusion and improves the mechanical properties of carbon fibers. However, the silicone compound has strong water repellency, and the precursor to which it is applied is prone to electrostatic damage and has poor cohesiveness, so the flame resistance is In this process, there were drawbacks such as the occurrence of single yarn wrapping around guides, rollers, etc., fluffing, and single yarn breakage due to poor focusing of the precursor. The present inventors have developed a raw material oil for producing carbon fibers.
First, a raw material oil consisting of a higher alcohol-based and/or higher fatty acid-based oil having at least 18 carbon atoms and an organic antioxidant, and having a heat resistance of at least 200°C, is particularly suitable for the flame-retardant process. We have discovered and proposed a method to reduce fusing, fuzz, yarn breakage, etc. between single yarns, and to improve the mechanical properties of the carbon fibers. However, as a result of further studies on improving the quality of carbon fibers, especially on further improving their mechanical properties, we found that the focusing state of precursors, in other words, the opening state, is an important factor that affects the mechanical properties of carbon fibers. After discovering this, they conducted extensive research and came up with the present invention. That is, an object of the present invention is to provide a method for producing carbon fiber of high quality, particularly excellent mechanical properties, and another object of the present invention is to improve the operational stability in the firing process of the precursor to which the raw fiber oil has been applied, The object of the present invention is to provide a method for manufacturing carbon fiber with high production efficiency. The object of the present invention is to provide an organic polymer fiber yarn containing a higher alcohol-based and/or higher fatty acid-based oil having at least 18 carbon atoms and an organic antioxidant, and which has at least heat resistance. A raw yarn oil agent at 200°C is applied, the yarn is opened and entangled under tension by an air injection method, and then made flame resistant.
This can be achieved by a method for producing carbon fiber, which is characterized in that it is then carbonized. The precursor used in the present invention is effective against organic precursors such as cellulose-based, acrylic-based, and polyvinyl alcohol-based fibers, which tend to accumulate heat and become brittle during the firing process, especially during the flameproofing process, but acrylic fibers are preferred. . These precursors typically have a single yarn denier.
A fiber having a diameter of 0.5 to 2.0 d and a number of single threads of 500 to 30,000 is used. During the flame-retardant process, carbon fiber yarn is exposed to a high-temperature heating atmosphere of at least 200°C, and due to this high-temperature heating, the yarn undergoes complex chemical reactions such as intermolecular crosslinking and intramolecular cyclization. The fibers are converted into flame-resistant fibers through a reaction, but in this case, the fibers soften and partially melt during the initial stage of heating, and become tarred as the reaction progresses, causing fusion between single fibers. It is unavoidable that defects are likely to be formed in the fibers. The occurrence of inter-filament fusion and fiber defects during the initial high-temperature heating of the yarn varies markedly depending on the type of oil attached to the yarn, and the oil has low heat resistance and evaporates at temperatures below 200℃. When thermally decomposed, it cannot be expected to be effective in preventing the occurrence of such fusion and fiber defects, and on the contrary, it has an adverse effect. In the oil agent of the present invention, when the number of carbon atoms in the higher alcohol-based and/or higher fatty acid-based oil agent, which is the main component of the oil agent, is less than 18, the oil agent penetrates into the yarn significantly and the fusion prevention effect decreases. However, the number of carbon atoms should be at least 18, as this may cause deterioration of the physical properties of carbon fibers, especially the occurrence of defects in carbon fibers.
Preferably, the number is 18 to 25. Examples of such oils of the present invention include stearyl alcohol phosphate ester salts as higher alcohol oils, or ethylene oxide [(EO)n] added to which the number n is approximately 20 to 40.
Examples include stearyl alcohol (EO) n, oleyl alcohol (EO) n, behenyl alcohol (EO) n, isopentacosanyl alcohol (EO) n, etc., but stearyl alcohol (EO) n, oleyl alcohol ( EO)n,
Isopentacosanyl alcohol (EO)n and the like are preferably used. Two or more of these oil agents may be used in combination. In addition, examples of higher fatty acid oils include stearic acid glyceride,
Or polyethylene glycol (PEG) with a molecular weight of 400 to 1000, PEG stearate, PEG
Examples include oleate, PEG sorbitan oleate, PEG sorbitan stearate, etc.
PEG stearate, PEG olate, etc. are preferably used. Note that two or more of these oil agents may be used in combination. Furthermore, the heat resistance of typical higher alcohol-based oils and higher fatty acid-based oils is shown in Table 1.

【table】

[Measurement method of CF value]

One end of the fiber with a length of about 100 cm is fixed to the upper end of the index finger in cm, and a weight of grams equal to 0.2 times the denier of the fiber bundle is lowered to the lower end (however, the weight is
If it exceeds 500 denier, it will be 100g). Divide the yarn and insert the hook so that at least 1/3 of the total number of filaments is on one side on the index finger 0.5 to 1.0 cm below the fixing point. This hook is a single thread denier 5
Double the weight to the same number of grams. Drop the hook until it catches the thread, and read the distance L from the separation starting point to the stationary point. Repeat this test 100 times with different samples, omitting the upper and lower 20% of L, and use the remaining average value as the representative value M of the sample. The CF value is 100 divided by the value of M in cm. In the present invention, after applying a yarn oil to the precursor and then applying an air injection treatment,
The heat treatment is particularly effective against static electricity damage, fusion, fuzz, thread breakage, etc. in the production of acrylic carbon fibers, and it is also possible to obtain carbon fibers with high mechanical properties. By using such air injection treatment, it is possible to further enhance the effect of the raw yarn oil agent in reducing fusion, fuzz, yarn breakage, etc. during the firing process, and to improve the mechanical properties of the carbon fiber. This is because the air injection treatment improves the opening properties between the single yarns of the precursor, and eliminates the cohesive fusion that occurs in the precursor, which reduces the occurrence of fusion during the firing process, especially during the flame-retardant process. This is thought to be because the flame resistance of each single yarn progresses evenly. In addition, fusion in the present invention refers to a state in which a single yarn softens and adheres to an adjacent single yarn, and the bonded boundary part is planar or the bonded boundary disappears. Bonding refers to the bonding between single yarns due to softening of the single yarns or due to solvents, oils, etc., and the bonded boundaries are dotted. The precursor, which has been subjected to the yarn oil adhesion treatment and the air injection treatment, is then flame-retardant treated in an oxidizing atmosphere within the range of 200 to 400°C, and is further flame-resistant treated in an inert atmosphere at at least 800°C, such as nitrogen gas. A known method is used for these flameproofing and carbonization treatments. According to the present invention, troubles such as fusion, fuzz, and thread breakage in the flameproofing or carbonization process can be prevented,
Carbon fibers can be manufactured with high productivity. It also has remarkable effects, such as the ability to obtain high-strength carbon fibers. The present invention will be specifically described below with reference to Examples. Example 1, Comparative Example 1 Acrylonitrile 99.5 mol%, itaconic acid
0.5 mol% was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent to obtain a spinning stock solution with a stock solution concentration of 22%, which was then spun into a dimethyl sulfoxide aqueous solution, washed with water, and stretched by a known method.
A raw yarn of 6000 denier and 6000 filament was obtained.
This drawn yarn was immersed in an 8.5% aqueous solution of a raw yarn oil (heat resistance was 210°C) consisting of 95% by weight of stearyl alcohol (EO) ₂₀ and 5% by weight of di(nonylphenyl)diphenyl phenyl phosphorite. After drying, an acrylic fiber filament with a strength of 6.3 g/d was obtained. The amount of oil attached is 1.9 per weight of yarn
It was %. Next, this yarn is untwisted and continuously twisted to a diameter of 20mmφ.
through an air injection nozzle. At this time, the yarn speed was 3 m/min, the yarn tension was 0.15 g/d, and the air pressure was 1.2 Kg/cm ² . Furthermore, this yarn is continuously spun at a yarn speed of 3.0 m/min.
Flame retardant treatment is performed at a temperature of 240-260℃ for 30 minutes,
Next, a carbonized thread was obtained by carbonization treatment at a temperature of 1300°C in a nitrogen atmosphere. A resin-impregnated strand was prepared from this carbonized yarn based on JIS R-7601 and its tensile strength was measured. As a comparative example, the same procedure as in Example 1 was carried out except that the air injection treatment was not performed. The results are shown in Table 2.

[Table] Examples 2 to 6, Comparative Example 2 The treatment was carried out in the same manner as in Example 1 except that the blending ratio or combination of the oil agent and the organic antioxidant was changed. The results are shown in Table 3. Incidentally, in each of the Examples, no aggregated fusion of the flame-resistant yarn was observed, but in the Comparative Example, a considerable amount of aggregated fusion was observed.

[Table] Examples 7 to 8, Comparative Examples 3 to 5 The resin-impregnated strands were treated in the same manner as in Example 1, except that the air pressure in the air injection was changed as shown in Table 4 to change the CF value. The strength was measured. The results are shown in Table 4.

【table】

Claims (1)

[Scope of Claims] 1 Organic polymer fiber yarn containing a higher alcohol-based and/or higher fatty acid-based oil having at least 18 carbon atoms and an organic antioxidant, and has a heat resistance of at least 200°C. 1. A method for producing carbon fibers, which comprises applying a raw yarn oil agent, opening and entangling the yarns under tension by an air injection method, making them flame resistant, and then carbonizing them. Here, the heat resistance of the oil is defined as the solid content of the oil.
This refers to the temperature at which the weight loss rate based on the weight of the oil agent (solid content) is 5% from the weight loss curve obtained when 10 mg is taken into a thermobalance and heated at a heating rate of 2.5°C/min. 2. The method for producing carbon fiber according to claim 1, wherein the degree of entanglement of the threads by opening and entangling treatment is 20 to 40 as a CF value.