JPS623246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing flame-resistant fibers, in particular, a method for producing flame-resistant fibers, in particular acrylic fiber yarns (hereinafter referred to as precursors).
In the flame-retardant heating method using an oxidizing atmosphere at 400℃, we aim to stabilize operations, and at the same time, the subsequent carbonization or graphitization treatment in a high-temperature non-oxidizing atmosphere reduces fuzz and single yarn breakage. The present invention also relates to a method for producing flame-resistant fibers that can be made into carbon fibers or graphitized fibers with excellent mechanical properties. Conventionally, carbon fibers or graphitized fibers are produced by converting a precursor that can be carbonized or graphitized into flame-resistant fibers in an oxidizing atmosphere of about 200 to 400 degrees Celsius, and then carbonizing them at high temperatures of about 800 degrees Celsius or higher in a non-oxidizing atmosphere. A method of graphitizing at a higher temperature of about 2000° C. or higher in a non-oxidizing atmosphere has been adopted as a general industrial manufacturing method. However, so-called flame-retardation, in which the precursor is converted into flame-retardant fibers in a high-temperature heating atmosphere, is an oxidation reaction that generates heat from the precursor, so rapid heating causes local heat accumulation, which tends to lead to heterogeneous reactions. As a result, the precursors may fuse or coalesce with each other, or become brittle, making it difficult to obtain high-quality carbon fibers or graphitized fibers. Of course, it is also true that various attempts are being considered to solve this problem. For example, in JP-A No. 51-53020, fiber deterioration during flame-proofing is prevented by opening precursors in advance by airflow treatment to remove cohesive fusion between fibers, and then applying flame-retardant treatment. It is said that this improves the mechanical properties (strength and elastic modulus) of carbon fibers. However, while removing the coagulation of the precursor does improve the fibrous properties of carbon fibers,
Because of the improved opening properties, the single fibers of the precursor are easily squeezed by guides, especially when a heating method using a high-temperature oxidizing atmosphere is sought for the flame-retardant process.
In addition, there was a drawback that adjacent comrades were likely to become entangled, causing fuzz or single thread breakage. Furthermore, in JP-A No. 52-148227, it is said that impregnating a precursor with a silicon-based compound can prevent the coalescence or fusing of single fibers during flame-retardation and improve the mechanical properties of carbon fibers. Although silicone-based compound treatment can prevent single fibers from adhering or fusing together, silicone-based compounds are inherently highly water-repellent, and precursors treated with this compound are prone to electrostatic damage and lack convergence, making them difficult to maintain. The above-mentioned flame-retardant treatment under such conditions not only causes fuzz and single yarn breakage, but also tends to cause the yarn to become fluffy when strained with a guide, causing frequent wrapping around the guide rollers, impairing stable operation. There was a drawback. The inventors of the present invention have conducted intensive studies to solve the drawbacks of the prior art described above, and as a result, have arrived at the present invention.That is, the purpose of the present invention is to
The purpose is to stabilize operations and improve productivity by imparting specific entangling or cohesive properties to the precursor when flame-resistant by heating in an oxidizing atmosphere at °C. Another objective is to obtain carbon fibers or graphitized fibers with less wing/fiber breakage and excellent mechanical properties. The object of the present invention is to reduce the degree of entanglement of the acrylic fiber yarn by a fluid injection method when making the acrylic fiber yarn flame resistant by heating in a high-temperature oxidizing atmosphere.
A method for producing flame-resistant fibers, which is characterized in that the fibers are subjected to an entanglement treatment so that the CF value is 20 to 40, then subjected to a low twisting treatment of 10 times/m or less, and then supplied to a flame-retardant treatment. It is achieved by doing so. The precursor in the present invention is usually a single yarn denier.
0.5~2.0d, number of constituent filaments ranges from 500~30000. The precursor is guided at a speed of usually 1 to 10 m/min into a flameproofing furnace equipped with multiple pairs of guide rollers, where it is subjected to flameproofing treatment under oxidizing gas heated to a predetermined temperature. However, the important point in the present invention is that the precursor supplied to the flameproofing furnace is subjected to a specific entangling treatment and then subjected to a low twisting treatment of 10 times/m or less. be. That is, the precursor is subjected to an entanglement treatment by a fluid jet method in the state of a substantially untwisted continuous filament yarn, whereby the filaments are appropriately entangled with each other. If this confounding state is expressed as a CF value, it should be between 20 and 40. Precursors with a CF value of 20 or more can be obtained by the general twisting method, but if the entangled state or convergence is improved only by twisting, as mentioned above, severe flame resistance may be obtained. In this case, processing spots or deterioration of the precursor itself occur mainly due to heat accumulation, and the high quality carbon fiber or graphitized fiber that is the object of the present invention cannot be obtained. The entanglement treatment using the fluid jetting method here refers to the fluid jetting method (interlacing), which has recently been attracting attention as a manufacturing method for normal processed fiber yarns, or a method similar thereto, in which, for example, the flow of air, which is a compressible fluid, is restricted. In this method, the filaments are entangled with each other by rapidly ejecting the air from a chamber to form a disturbed region of air, and passing the continuous filament yarn through this disturbed region. However, unlike ordinary processed yarn, processing conditions for the precursor used in the present invention should be selected so as not to form fuzz or loops, and in particular, the tension of the precursor supplied to the above-mentioned fluid disturbance region should be set to 0.005 to 0.2 g. It is best to adjust the atmosphere to /d. Of course, such processing conditions, such as the number of processing times, the tension of the precursor, the amount of air, the total denier of the precursor, and the processing speed, should be appropriately selected to meet the purpose of the present invention. Further, the above-mentioned CF value is a value determined by the measurement method described below. [Measurement method of CF value] One end of a fiber approximately 100 cm long is fixed to the upper end of a centimeter index finger, and a weight in grams equal to 0.2 times the denier of the fiber is lowered to the lower end. (However, if the weight exceeds 500 denier, use 100 g.) Separate 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 fixed point. This hook is made of single thread denier.
Make the weight the same number of grams as 2.5 times. Drop the hook until it catches the thread, and read the distance L from the starting point of separation 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 OF value is 100 divided by the value of M in cm. The above-mentioned precursor, that is, the precursor which is substantially untwisted and has a suitable entangling property obtained by an entangling treatment using a fluid injection method, further has a twisting rate of 10 times/m or less,
Preferably, a low twisting treatment of 5 to 7 times/m is performed. As described above, it is essential for the present invention to integrally perform the entanglement treatment using the fluid injection method and the low twisting treatment for the precursor, and if any of these are lacking, the convergence of the precursor will be poor as described above. As a result, fluff and single yarn breakage occur frequently during the flameproofing process, and stable operation becomes impossible due to the precursor being wound around the roller. On the other hand, even if the above-mentioned entangling treatment and low twisting treatment are performed, if these treatments are not appropriate, for example, if the number of twists exceeds 10 times/m, it will not work under severe flame resistance conditions such as ambient temperature. Mainly due to internal heat accumulation in the precursor, processing spots or deterioration of the precursor itself occurs, and not only fuzz and single thread breakage occur, but also carbonization obtained by subsequent carbonization or graphitization treatment in a high-temperature non-oxidizing atmosphere. The mechanical properties of the fibers or graphitized fibers, especially the strength and modulus of elasticity, are significantly reduced. The low twisting treatment here must be carried out before supplying the material to the flame-retardant process, and a method is used in which the supply package is rotated while adjusting the speed according to the diameter so that the number of actual twists is constant. is good. This direction of rotation is the direction in which the yarn is wound, providing stable yarn twisting and unraveling properties. The above-described entanglement treatment and low twist treatment in the present invention are particularly effective for precursors treated with silicon-based compounds. For example, the general formula, However, R ₁ to R ₃ : H, -CH ₃ , C ₂ H ₅ or -C ₆ H ₅ R ₄ : -(CH ₂ ) - _o (n=integer from 1 to 10) R ₅ to R ₆ : H, _{-CH 3 _ _ _ _ _} )

[Formula] (R ₇ and R ₈ are H, or an alkyl group or phenyl group having 10 or less carbon atoms) A silicon compound represented by the formula, such as a polydimethylsiloxane ethylene oxide adduct, is a monomer in the precursor during flame resistance, as described above. It is also effective against coalescence or fusion between fibers,
On the other hand, there were drawbacks such as static electricity interference and focusing ability, but
This point can be fully covered by applying the present invention. In this case, the precursor usually contains or has a silicon-based compound attached thereto in an amount of about 1.0 to 2.0% per precursor. Further, the precursor obtained by the above-mentioned treatment of the present invention may be supplied as it is to the flame-retardant process, but after a plurality of precursors, for example, 2 to 4 precursors are once aligned (or knotted), Even if it is supplied, the effects of the present invention are not diminished at all, but rather it is effective in that productivity can be improved by increasing the amount of flame-retardant treatment. As described above, the gist of the present invention is to integrally perform a specific entangling treatment and low twisting treatment on the precursor when flame-resistant by heating in an oxidizing atmosphere at 200 to 400°C. Therefore, the operation in the flameproofing process is stable, and the subsequent carbonization or graphitization treatment produces carbon fibers or graphitized fibers with less wing breakage and excellent mechanical properties, particularly strength, and elastic modulus. A flame-resistant fiber that can be used as a flame resistant fiber is obtained. Furthermore, if the precursors of the present invention are suitably aligned (or doubled) and subjected to flame-retardant treatment, productivity can be improved without reducing the above-mentioned effects of the present invention. The present invention will be specifically described below with reference to Examples. Example 1 Substantially untwisted acrylic filament yarn (number of filaments: 6000, amount of silicone compound deposited: 1.5)
%) was subjected to entangling treatment using an airflow treatment nozzle. At this time, the CF value was changed by adjusting the amount of air. Next, the interlaced yarn was heated using a twisting machine to form a flame-resistant precursor. After aligning two of the precursors, they were fed to a flameproofing furnace at a speed of 4 m/min and flameproofed in air at 250 to 260°C for 30 minutes. The flameproofing furnace used here was equipped with 2 pairs x 8 stages of grooved rollers.
Hot air at a predetermined temperature is circulated inside the furnace. Next, the flame-retardant yarn obtained by the above-described flame-retardant treatment was carbonized for 2 minutes in a carbonization furnace at a maximum temperature of 1300° C. in nitrogen gas. Operational stability during flame-retardant treatment (single yarn wrapping on roller, yarn breakage), quality of carbonized yarn (fuzz,
Strength) is shown in Table 1.

【table】

Claims (1)

[Scope of Claims] 1. When making acrylic fiber yarns flame-resistant by heating in a high-temperature oxidizing atmosphere, the yarns are treated with a fluid jetting method so that the degree of entanglement of the yarns becomes 20 to 40 as a CF value. A method for producing flame-resistant fibers, which comprises subjecting the fibers to an interlacing treatment, then subjecting them to a low twisting treatment of 10 times/m or less, and then supplying them to a flame-resistant treatment. 2. The method for producing a flame-resistant fiber according to claim 1, wherein the number of twists of the yarn by low twisting treatment is 5 to 7 times/m. 3. The method for producing a flame-resistant fiber according to claim 1, wherein the acrylic fiber yarn contains 1.0 to 2.0% of a silicon compound.