JPH0515825B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing carbon fibers, and particularly to a method for producing carbon fibers to which no sizing agent has been added with good quality and high productivity. [Conventional technology] Conventionally, the method for manufacturing carbon fibers is to make precursor fibers for carbon fibers (hereinafter simply referred to as precursors) flame resistant, carbonize them, perform surface treatment as necessary, and then improve handling properties. Therefore, it was customary to dry the sizing agent and then wind it onto a bobbin. That is, carbon fiber products generally include those to which a sizing agent has been applied. However, recently, matrices for composite materials have become more diverse, and the development of composite materials using matrices of metals, ceramics, thermoplastic resins, etc. is rapidly expanding from the conventional thermosetting resins. For such matrices, if a sizing agent is attached, it may cause poor wettability with the matrix, or impregnation such as reduction treatment or coating treatment to improve the wettability of carbon fibers. There is a problem that when pre-treatment is performed, it becomes an impurity and the treatment effect is reduced. Therefore, carbon fibers to which no sizing agent is attached are required for these matrix applications. For this purpose, sizing-treated carbon fibers have conventionally been used after the sizing agent is removed by a method such as burning off. However, burning off this sizing agent causes significant fuzzing and deterioration of physical properties, and adding a burning process reduces productivity and economic efficiency, so in the end, carbon fibers that are not subjected to sizing treatment are preferable. Therefore, conventionally, the sizing agent treatment after carbonization was simply omitted,
Moreover, a method of winding it in a dry state has been adopted. However, carbon fibers that are not treated with a sizing agent naturally have extremely poor cohesiveness and are prone to fuzzing, and in addition, such rolled-up package cages of carbon fibers tend to suffer from the so-called collapse of the package shoulders. This is easy to happen, and for this reason, there was a problem that the winding weight per bobbin could not be increased. [Problems to be Solved by the Invention] An object of the present invention is to solve the problems of the above-mentioned conventional techniques and provide a method for manufacturing high-quality carbon fibers with good productivity without treating carbon fibers with a sizing agent. There is a particular thing. [Means for Solving the Problems] The above object of the present invention is to carbonize precursor fibers for carbon fibers, and add 0.1% by weight of water having an electrical conductivity of 300 μS/cm or less at 20° C. to the obtained carbon fibers. More than 30
This can be solved by winding up the product while retaining the adhesion below % by weight and packaging it in moisture-impermeable packaging. That is, the precursor in the present invention is not particularly limited, and acrylic fibers, pitch fibers, rayon fibers, etc. can be used, but acrylic fibers are preferable. After making these precursors flameproof or infusible using conventionally known techniques, the method of the present invention can be applied to carbon fibers carbonized at 1000 to 2000°C or graphitized fibers graphitized at 2000°C or higher. The carbon fibers in the present invention include the above-mentioned carbon fibers and graphitized fibers. In addition, the number of twists of the precursor at this time is not particularly limited, and may be untwisted or twisted, but
In order to prevent deterioration of physical properties, it is preferable to use no twisting or twisting of 40 T/m or less. The water in the present invention has an electrical conductivity of 300μS/
cm or less, soft water, tap water, ion exchange water, distilled water, etc. are used, but preferably 10μS/cm
Distilled water or ion-exchanged water with a concentration of 2 μS/cm or less is more preferred. Incidentally, a surfactant such as "Neugen" (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) or the like may be added to these water supplies as necessary to improve wettability. At this time, if the conductivity of the water exceeds 300 μS/cm, it will contain a large amount of impurities such as metal ions, which will cause problems such as poor adhesion and poor curing of resin due to impurities in high-order processing steps. . Note that this electrical conductivity is a value measured at 20°C. In addition, the amount of water attached to the carbon fiber is 0.1% to 30% by weight, preferably 0.3 to 25% by weight,
More preferably, it is 0.5 to 20% by weight. This water content refers to the water content in the carbon fiber at the winding stage. If this water content is less than 0.1% by weight, the focusing effect will be small, causing fuzz, single fiber breakage, and
Problems such as shoulder collapse in pack cages began to occur frequently. On the other hand, if it exceeds 30% by weight, the effect of adhering water will be saturated, and excess water will seep out of the package cage, causing water to accumulate inside the package cage when it is packaged with a moisture-impermeable film. There are problems such as causing rust in the winder's traverse guide, etc. At this time, the method of applying water is not particularly limited, as long as it is possible to maintain a predetermined amount of water attached to the carbon fibers by passing it through a water tank or by a shower method. Further, the fiber tension during water application may be the tension during firing, or the tension may be appropriately controlled via a drive roller. The winding method and winding package of the carbon fiber to which a predetermined amount of water has been applied are not particularly limited, and conventionally known methods can be applied. After winding up, the carbon fibers are wrapped in moisture-impermeable packaging such as shrink film to prevent moisture adhering to them from evaporating. If such moisture-impermeable packaging is not used, there are problems in that the end surfaces are likely to collapse during transportation, and fuzz is likely to occur when unrolling. It is also desirable to keep the temperature and humidity at approximately constant levels during winding to avoid being affected by the seasons. [Example] Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 Acrylic fibers with a single filament fineness of 1.0 denier and 12,000 filaments were finally carbonized at 1,250° C. in an inert atmosphere, and then subjected to electrolytic surface treatment with a dilute nitric acid aqueous solution using the carbon fibers as anodes. Next, the electrolytically treated carbon fibers were washed through a washing tank filled with water having an electrical conductivity of 0.7 μS/cm, and then wound onto a bobbin without drying. The amount of moisture attached to the yarn during winding was approximately 6% by weight. Furthermore, as a result of visually counting the fuzz on the yarn during winding, the number of fuzz (single thread breakage) of 5 mm or more was as small as about 1 piece/m. In addition, the winding amount is 10 with a width of 30 cm using the square end method.
I was able to reliably wind up to Kg. The packages thus obtained were left for 30 days under the conditions shown in Table 1. Both the bobbin shape after being left and the unrolled state during composite molding were able to be maintained in good condition by using moisture-impermeable packaging.

[Table] Comparative Example 1 After carbonization, electrolytic surface treatment, and water washing were performed under the same conditions as in Example 1, the product was dried and rolled up in a moisture-free state. The number of fuzz pieces of 5 mm or more was as high as about 10 pieces/m, and the amount of yarn that could be wound was only 3 kg due to the yarn slipping and causing the shoulders to collapse. Example 2 Under the same conditions as Example 1, carbonization was followed by continuous graphitization at 2000°C, and the electrical conductivity was increased without electrolytic surface treatment.
After passing through a water tank filled with 230 μS/cm water, the material was wound onto a bobbin without drying. The amount of water adhering to the carbon fibers at the time of winding was approximately 0.8% by weight. The fuzz of the yarn was about 3 fuzz/m, and it was possible to stably wind up up to 6 kg. This was packaged in moisture-impermeable polyethylene film. This allowed us to keep it in good condition. Comparative Example 2 After carbonization and graphitization under the same conditions as in Example 2, the product was passed through a water bath without electrolytic surface treatment, and then rolled up in a dry and moisture-free state. The amount of fuzz on the yarn was about 25 pieces/m, and the amount of winding was limited to 1 kg due to the yarn slipping and causing the shoulders to collapse. Comparative Example 3 In Example 2, the conductivity of the aquarium water was
Winding was carried out under the same conditions except that the water concentration was changed to 1000 μS/cm, and the film was further packaged in moisture-impermeable polyethylene film. The amount of moisture attached to the carbon fiber was approximately 1.0% by weight, and the fluff and winding amount of the yarn were approximately 4 pieces/m and 6 kg, respectively, but curing failure occurred during the subsequent resin impregnation process. woke up. [Effects of the Invention] Since the carbon fiber produced by the method of the present invention is wound into a package with a predetermined amount of attached moisture, the cohesiveness in the winding process is improved and fuzzing due to friction with the roller is reduced. At the same time as the quality improves,
By increasing the winding amount based on the reduction in shoulder collapse during bobbin winding, productivity could be significantly improved. On the other hand, in the high-order processing process of carbon fibers, it is possible to not only solve the problem of adhesion with the matrix caused by the sizing agent, but also to prevent problems caused by fluff, which has the remarkable effect of improving the quality of the final product and improving handling properties. was recognized.

Claims (1)

[Claims] 1 Carbonize the precursor fiber for carbon fiber, and the electrical conductivity of the obtained carbon fiber at 20°C is 300μS/
A method for manufacturing carbon fiber, which comprises winding the fiber in a state in which it retains 0.1% to 30% by weight of water in an amount of 0.1 cm or less, and packaging it in moisture-impermeable packaging.