CN110709553A

CN110709553A - Method for producing carbon fiber bundle provided with sizing agent

Info

Publication number: CN110709553A
Application number: CN201880038040.1A
Authority: CN
Inventors: 金山启司; 伊藤隆弘
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2017-07-10
Filing date: 2018-06-04
Publication date: 2020-01-17
Also published as: KR102076465B1; US20200123688A1; WO2019012856A1; MX2019014095A; JPWO2019012856A1; EP3653772A1; KR20190141015A; TW201908565A; RU2020102001A; EP3653772A4; JP6455637B1

Abstract

In order to solve the problem of entanglement due to the fixation of sizing liquid to a guide roll (3), in a sizing agent liquid tank (4), a carbon fiber bundle (1) is immersed in the sizing agent liquid tank (4), and the guide roll surface tackiness of the first guide roll (3) after the carbon fiber bundle (1) is exposed from the liquid surface of the sizing agent liquid tank (4) is set to 0.2N/cm²The following.

Description

Method for producing carbon fiber bundle provided with sizing agent

Technical Field

The present invention relates to a method for producing a sizing agent-added carbon fiber bundle to which a sizing agent is added.

Background

Carbon fiber bundles have excellent mechanical properties, and in particular, have a high specific strength and a high specific elastic modulus, and therefore are widely used in general industrial applications such as aerospace applications, sports and leisure applications, automobiles, and windmills. In recent years, customers who use carbon fiber bundles have been strongly required to improve quality and reduce cost.

Carbon fiber bundles generally have low elongation and are brittle, and in a high-grade processing step, fluff is likely to be generated and yarn breakage may occur due to contact with a roller, friction with a yarn path guide, and the like. Therefore, generally, various sizing agents are applied to the carbon fiber bundle to improve the handling property, improve the bundling property and the friction resistance of the carbon fiber bundle, and suppress the generation of fluff in the carbon fiber bundle to maintain the quality.

As a method of applying the sizing agent to the carbon fiber bundle, there are various methods such as a sprayer-jet method, a dropping method, and a kiss-coating-roll method. In view of efficiency that can be easily provided to a plurality of filaments at the same time, an immersion method in which the carbon fiber bundle is immersed in the sizing agent tank is preferable. However, when the carbon fiber bundle is multi-threaded or the production speed is increased in order to reduce the cost, the amount of the sizing agent liquid adhering to the carbon fiber bundle and being carried out from the sizing agent liquid tank increases, and the amount of the sizing agent liquid adhering to the guide roller leading to the drying step subsequent to the sizing agent applying step also increases. Then, the sizing agent liquid dries on the surface of the guide roll to generate resin accumulation, thereby increasing the viscosity. If the carbon fiber bundles contact the resin pool, fluff is generated, and the carbon fiber bundles may be wound around a guide roll to reduce the process throughput. When the interval between adjacent carbon fiber bundles is narrowed for the purpose of making the carbon fiber bundles into a plurality of filaments, a film formed from the sizing agent liquid tends to be generated between the adjacent filaments. Further, the liquid film is directly dried to generate a stain of the sizing agent liquid. Further, the carbon fiber bundles running adjacent to each other are likely to stick to each other due to the surface tension of the sizing agent liquid, and thus a problem of poor fiber separation is likely to occur.

As an improvement technique,

patent documents

1 and 2 disclose a method of removing a liquid film formed of a sizing agent generated between filaments of a carbon fiber bundle by ejecting a pressurized gas to the carbon fiber bundle after the carbon fiber bundle is exposed from a liquid surface of a sizing agent liquid tank.

Patent document 3 discloses a method of preventing drying of a sizing agent solution by removing an excess sizing agent solution impregnated in a carbon fiber bundle and applying the sizing agent solution to the surface of a roll by nipping the carbon fiber bundle between at least a pair of rolls. Patent document 4 discloses a method for producing a carbon fiber bundle having excellent fiber opening properties, in which a carbon fiber bundle in an untwisted state is subjected to sizing treatment and then dried by a heat roll, in which a wiping cloth is pressed against the heat roll to remove excess sizing agent liquid from the heat roll.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-23785

Patent document 2: japanese laid-open patent publication No. 7-145549

Patent document 3: japanese patent laid-open publication No. 2011-256486

Patent document 4: japanese laid-open patent publication No. 1-292038

Disclosure of Invention

Problems to be solved by the invention

However, the methods of

patent documents

1 and 2 have a problem that the sizing agent liquid remains attached to the carbon fiber bundles and the sizing agent liquid is transferred to the surface of the guide roll to cause resin accumulation even if the liquid film between the filaments of the carbon fiber bundles can be removed. Further, in the method of patent document 3, since the brittle carbon fiber bundle is nipped by the nip roller, there is a problem that fuzz occurs and the process throughput is lowered. In the method of patent document 4, since the excess sizing agent liquid adhering to the heat roll is removed by the wiping cloth, resin accumulation of the heat roll itself due to drying of the sizing agent liquid is suppressed, but there is a problem that the sizing agent liquid is easily dried on the first guide roll before the heat roll and after the sizing agent applying step, and the monofilament of the carbon fiber bundle is taken up to the resin accumulation generated at the time of drying of the sizing agent liquid, and thus fluffing and tangling occur.

An object of the present invention is to solve the above-described problems of the prior art and to provide a method for producing a carbon fiber bundle to which a sizing agent is applied, which can solve the problems of entanglement and fuzzing of the carbon fiber bundle due to drying of the sizing agent liquid at a guide roll and resin accumulation.

Means for solving the problems

In order to achieve the above object, the present invention has the following configurations. That is to say that the first and second electrodes,

a method for producing a sizing agent-added carbon fiber bundle, which comprises a sizing agent adding step of immersing a plurality of carbon fiber bundles in parallel in a sizing agent tank, and a drying step of subjecting the carbon fiber bundles to be subjected to sizing agent addition, wherein the carbon fiber bundles are immersed in the sizing agent tank, and the guide roll surface tackiness of the first guide roll after the carbon fiber bundles are exposed from the liquid surface of the sizing agent tank is 0.2N/cm²The following.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, in the method for producing a sizing-agent-added carbon fiber bundle to which a sizing agent liquid is added, a high-quality carbon fiber bundle with less fluff can be obtained by preventing drying and resin accumulation of the sizing agent liquid at the guide roll. In addition, the carbon fiber bundle can be prevented from being wound on the guide roller, and the process throughput is also excellent.

Drawings

FIG. 1 is a schematic configuration diagram showing an example of a sizing step in the present invention.

FIG. 2 is a schematic configuration diagram showing another example of the sizing step in the present invention.

FIG. 3 is a schematic configuration diagram showing another example of the sizing step in the present invention.

FIG. 4 is a schematic configuration diagram showing another example of the sizing step in the present invention.

Fig. 5 is a diagram showing a method of calculating a force for starting movement of a carbon fiber bundle.

Fig. 6 is a schematic configuration diagram showing an example of a conventional sizing step.

Detailed Description

The method for producing a sizing-agent-added carbon fiber bundle according to the present invention is a method for producing a sizing-agent-added carbon fiber bundle, which comprises a sizing agent adding step of immersing a plurality of carbon fiber bundles in parallel in a sizing agent tank, and a drying step provided thereafter, wherein the carbon fiber bundle is immersed in the sizing agent tank, and the adhesion of the surface of the first guide roll to the surface of the first guide roll after the carbon fiber bundle is exposed from the liquid surface of the sizing agent tank is 0.2N/cm²The following.

Hereinafter, a method for producing a carbon fiber bundle provided with a sizing agent according to the present invention will be described in detail.

The carbon fiber bundle used in the present invention may be a carbon fiber bundle obtained from any of pitch-based, rayon-based, polyacrylonitrile-based, and the like raw materials, but from the viewpoint of quality and productivity, a polyacrylonitrile-based carbon fiber bundle is preferable. The form of the carbon fiber bundle used in the present invention is not particularly limited, and for example, a bundle of carbon fibers having a monofilament diameter of 3 μm or more and 10 μm or less may be used. The number of filaments of the carbon fibers constituting the carbon fiber bundle is not particularly limited, and may be, for example, 1000 to 100000 filaments. However, the effect of the present invention is easily exerted when a large number of carbon fiber bundles of 3000 or more filaments, which have a relatively large number of filaments, are taken out of the sizing agent liquid tank.

The polyacrylonitrile-based carbon fiber bundle preferably used in the present invention can be obtained by subjecting a polyacrylonitrile-based precursor fiber bundle to flame resistance, preliminary carbonization, and carbonization by a known method, and is not particularly limited. The flame resistance can be carried out in an oxidizing atmosphere at 200 to 300 ℃. The oxidizing gas used for flame resistance is preferably air from the viewpoint of economy. Then, the pre-carbonization can be performed in a pre-carbonization furnace with a maximum temperature of 300 to 1000 ℃ in an inert atmosphere. Further, the pre-carbonized fiber bundle is carbonized at a maximum temperature of 1200 to 2000 ℃ to obtain a carbon fiber bundle. The carbon fiber bundle can be further graphitized at 2000-3000 ℃ according to the requirement. The precarbonization, carbonization, and graphitization are performed in an inert atmosphere, and the inert gas used is, for example, nitrogen, argon, and xenon, and from the viewpoint of economy, nitrogen is preferably used.

In addition, in order to easily improve the affinity and adhesion between the carbon fiber bundle and the matrix resin when the carbon fiber-reinforced composite material is produced, it is preferable to subject the carbon fiber bundle to a surface treatment such as an electrolytic oxidation treatment in an electrolyte solution or an oxidation treatment in a gas phase or a liquid phase. As the electrolyte, either an acidic aqueous solution or an alkaline aqueous solution can be used, but as the acidic aqueous solution, sulfuric acid or nitric acid showing strong acidity is preferable, and as the alkaline aqueous solution, an aqueous solution of an inorganic base such as ammonium carbonate, ammonium hydrogen carbonate (carbonic acid solution アンモニウム), or ammonium hydrogen carbonate (heavy carbonic acid solution アンモニウム) is preferable.

The sizing agent liquid used in the present invention may be a sizing agent liquid obtained by dispersing or dissolving a sizing agent in water or an organic solvent such as acetone, but is preferably an aqueous dispersion or an aqueous solution obtained by dispersing or dissolving a sizing agent in water from the viewpoint of providing uniformity to the carbon fiber bundle and safety. The sizing agent may be used in accordance with a matrix resin used for advanced processing, from among sizing agents known in the field of carbon fibers. The sizing agent may contain a main agent and various additives described later, and for example, may be composed of a main agent and an emulsifier. The carbon fiber bundle impregnated with the sizing agent liquid is dried, whereby a sizing agent-added carbon fiber bundle having a sizing agent attached to the surface of the carbon fiber bundle can be obtained.

The type of sizing agent used in the present invention is not particularly limited, but the present invention is effective for a sizing agent liquid that is easily dried on a guide roll, and generates a resin pool to form an adhesive deposit. When the sizing agent contains a thermosetting resin as a component, an epoxy resin, an epoxy-modified urethane resin, a polyester resin, a phenol resin, a polyamide resin, a polyurethane resin, a polycarbonate resin, a polyetherimide resin, a polyamideimide resin, a polyimide resin, a bismaleimide resin, a urethane-modified epoxy resin, a polyvinyl alcohol resin, a polyvinyl pyrrolidone resin, a polyether sulfone resin, or the like, or a combination of two or more thereof can be used as a main component of the sizing agent. In addition, in the case where the component of the sizing agent contains a thermoplastic resin, as a main component of the sizing, a material containing at least one or more components selected from the group consisting of polycarbonate, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, polyethyleneimine, polyacrylamide, polyphenylene ether, polyacetal, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, an elastomeric cellulose compound, an acrylic resin, a polyurethane resin, a polyamide resin, a fluororesin, an ABS resin, a liquid crystal polymer, and a sodium hydroxide (partially) neutralized product of a styrene-maleic anhydride copolymer can be used.

In addition, since these organic compounds tend to be insoluble in water, a surfactant may be added to make an emulsion. The type of the surfactant is not particularly limited, and a nonionic surfactant is preferably used. Examples of the nonionic surfactant include ether types such as polyoxyethylene alkyl ether, single linear polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene solid alcohol ether, polyoxyethylene lanolin derivative, an ethylene oxide derivative of an alkylphenol-formaldehyde condensate, and polyoxyethylene polyoxypropylene alkyl ether, ether ester types such as polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene sorbitol fatty acid ester, and ester types such as polyethylene glycol fatty acid ester and polyglycerol fatty acid ester, and 1 to several kinds of these may be used in combination.

In diluting the sizing agent solution, it is preferable to dilute the sizing agent solution with water which is economical and safe. In the case of using an aqueous dispersion as the sizing agent, the concentration range in which water is present as a continuous phase is adjusted, but a method of impregnating the carbon fiber bundles with the sizing agent by diluting the tank concentration of the sizing agent to about 0.1 to 10 mass% so that the amount of the sizing agent attached to the carbon fiber bundles becomes a desired amount is common. When diluting the sizing agent liquid by adding water thereto in order to adjust the sizing agent liquid to a desired tank concentration, the dilution may be performed 1 time or may be performed a plurality of times depending on the composition concentration of the sizing agent liquid such as the main component other than water. The sizing agent liquid may contain various additives such as a surfactant, a smoothing agent, and an emulsifier in addition to the above main component.

The resin pool of the sizing agent liquid on the guide roller after the passage of the sizing agent applying step is generated by transferring and accumulating the sizing agent liquid carried out from the sizing agent liquid tank by the carbon fiber bundle on the guide roller and drying the same in the traveling direction of the carbon fiber bundle. If the resin of the sizing agent liquid dries at the guide roller and a resin pool is generated, the traveling carbon fiber bundle comes into contact with the resin pool on the guide roller, the adhesion degree when the carbon fiber bundle is separated from the resin pool becomes large, and fluff, entanglement, and the like are generated. In the method for producing a carbon fiber bundle of the present invention, the guide roll surface tackiness of the first guide roll after the carbon fiber bundle is exposed from the liquid surface of the sizing agent liquid tank is 0.2N/cm²Hereinafter, it is preferably 0.1N/cm²Thereafter, the drying of the sizing agent liquid on the guide roller can be prevented, and the resin accumulation of the sizing agent can be prevented. The adhesion degree on the surface of the guide roller is more than 0.2N/cm²In the case of (2), a problem of fluff generation from the carbon fiber bundle and entanglement may occur. The guide roll surface tackiness is preferably maintained at 0.20N/cm²It is more preferably kept at 0.10N/cm or less²The following. The lower the degree of adhesion of the guide roll surface, the better the quality of the carbon fiber bundle, but the present invention aims to obtain a high-quality carbon fiber bundle with less fluff by preventing drying and resin accumulation of the sizing agent liquid at the guide roll, and further, it is necessary to apply the sizing agent to the carbon fiber bundle. Then, the sizing agent liquid is not dried and resin is accumulated on the guide roller, and therefore, tackiness is generated. Therefore, the surface tackiness of the guide roll is not substantially zero, and the lower limit of the surface tackiness of the guide roll is preferably 0.01N/cm²。

Here, the guide roll surface tackiness was calculated by the following equation.

Guide roll surface tackiness (N/cm)²) Initial movement of carbon fiber bundleForce/guide roller surface contact area of carbon fiber bundle.

A method of calculating the force to start moving the carbon fiber bundle will be described with reference to fig. 5. The force for starting the movement of the carbon fibers was measured as follows within 10 minutes from the stop of the production facility of the carbon fiber bundle during the long-term stable production, and was regarded as a value during the production.

First, the guide roller 3 to which the sizing agent liquid is attached is fixed so as not to rotate, and then the absolutely dry carbon fiber bundle 1 immediately before the sizing agent is applied is hung from the uppermost position of the guide roller 3 and set in a state where the contact angle is 180 °. Next, a loop was formed at one end of the carbon fiber bundle 1 set in the circumferential direction of the guide roller 3, and a hook was attached to the tip of the load cell 7 to hook the loop of the carbon fiber bundle. The load measuring instrument is not particularly limited, but is preferably a push-pull force meter capable of measuring the instantaneous maximum load. The carbon fiber bundle was gradually pulled by a load cell, and the maximum force immediately before the carbon fiber bundle 1 started moving from the surface of the guide roll 3 was set as the starting moving force (in newtons) of the carbon fiber.

The term "long-term stable production" means a case where continuous production is industrially stably performed for a long period of time (24 hours or more) without fluffing, curling, or the like. The stop of the carbon fiber bundle manufacturing apparatus means a timing of stopping the manufacturing apparatus including the steps from the sizing agent tank to the guide roll of the carbon fiber bundle. By stopping the carbon fiber bundle manufacturing equipment, the guide roller can be fixed and the starting force of the carbon fiber bundle can be measured.

The starting force of the carbon fiber bundle can be adjusted by adjusting the degree of drying of the sizing agent liquid adhering to the surface of the guide roller and by changing the material of the guide roller.

The guide roller surface contact area of the carbon fiber bundle is calculated from the product of the circumferential length of the carbon fiber bundle in the circumferential direction of the guide roller surface from the position where the carbon fiber bundle comes into contact with the guide roller to the position separated from the guide roller and the filament width of the carbon fiber bundle. The surface contact area can be changed by changing the contact circumferential length of the carbon fibers on the guide roll, the number of filaments of the carbon fiber bundle, and the like.

The present invention will be described in further detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of a sizing step in the present invention. In the embodiment shown in fig. 1, the carbon fiber bundle 1 is immersed in the sizing agent liquid tank 4 by the immersion roller 2, exposed from the liquid surface by the guide roller 3, and led to the drying step which is the next step of the sizing step. In such a configuration, since the carbon fiber bundle 1 to which the sizing agent liquid is applied passes through, the sizing agent liquid adheres to the guide roller 3. Therefore, in order to prevent the sizing agent liquid adhering to the guide roller 3 from being fixed, at least 1 contact body 5 selected from elastic materials such as cloth, resin, rubber, and the like is brought into contact with the guide roller 3. The surface tackiness of the guide roller was adjusted to 0.2N/cm by wiping off the sizing agent liquid adhering to the guide roller through the contact body 5²The following.

Here, the method of bringing the contact body into contact with the guide roller is not particularly limited, and examples thereof include a method of uniformly pressing the contact body against the guide roller. The contact body to be pressed is a resilient material such as cloth, flannel, resin, rubber, or metal, and the sizing agent liquid attached to the guide roller is removed to make the surface tackiness of the guide roller 0.2N/cm²The following is possible. In particular, plain cloth having a nap, such as plain cloth (calico), cotton flannel having a nap, such as flannel, and wool fabric are preferable from the viewpoint of being less likely to generate static electricity, strong, and water-absorbing.

The pressing pressure of the contact body is not particularly limited as long as the sizing agent liquid adhering to the guide roller can be removed, and the contact body may be set in a fixed or rotating state. However, if the pressing pressure is weak, the removal of the sizing agent liquid becomes insufficient and the effect becomes weak, while if the pressing pressure is too high, the guide roller does not rotate, and a large amount of fluff is generated in the traveling carbon fiber bundle by friction and is wound around the guide roller, thereby deteriorating the process throughput. In this respect, the cloth-like contact body is preferably windable and rotatable with respect to the guide roller. Further, the position of pressing the contact body is not particularly limited, but pressing against the surface of the traveling carbon fiber bundle that is not in contact is preferable in preventing occurrence of fuzz/disconnection due to contact between the contact body and the traveling carbon fiber bundle.

Further, when pressing the elastic material or the metal, it is preferable from the viewpoint of the removal efficiency of the sizing agent liquid that the guide roller is formed into a sharp shape like a doctor blade to such an extent that the guide roller is not damaged. When the doctor blade is used, the sizing agent liquid transferred on the surface of the guide roller while the guide roller rotates is carried out in such a manner that the sizing agent liquid is intercepted at the sharp leading end portion of the doctor blade which is in contact with the guide roller. In order to efficiently intercept the sizing agent liquid to the entire surface of the guide roll by the doctor blade, it is preferable that the sharp distal end portion of the doctor blade be in line contact with the guide roll in parallel with the axial direction thereof. The sharp portion of the doctor blade is preferably a hard blade edge made of metal or plastic, and thus, a solid deposit or an adhesive deposit such as a resin deposit generated on the guide roll during drying of the sizing agent liquid can be uniformly removed. Further, in order to remove the sizing agent liquid by the doctor blade over the entire width direction of the guide roller, a guide means such as a guide rail for a blade edge may be provided in a direction parallel to the axis of the guide roller, and the doctor blade may be provided in the axial direction of the guide roller. This enables the solid deposits and adhesive deposits on the guide roller to be effectively removed.

FIG. 2 is a schematic configuration diagram showing another example of the sizing step in the present invention. In the embodiment shown in fig. 2, the carbon fiber bundle 1 is immersed in the sizing agent liquid tank 4 by the immersion roller 2, exposed from the liquid surface by the guide roller 3, and led to the drying step which is the next step of the sizing step. In this embodiment, the carbon fiber bundle 1 to which the sizing agent liquid is applied passes through, and thus the sizing agent liquid adheres to the guide roller 3. Therefore, in order to prevent the sizing agent from adhering to the guide roller 3 from being fixed, the sizing agent liquid is separately supplied to the guide roller 3 independently of the sizing agent liquid from the sizing agent liquid tank 4 by using the sizing agent liquid spraying device 6 or the like. The method of applying the sizing agent liquid is not particularly limited to the sizing agent liquid spraying device 6, and examples thereof include a method of dropping or spraying the sizing agent liquid on the entire surface of the guide roll, a method of immersing the guide roll in the sizing agent liquid, and the like. In such a configuration, the guide roll can be made to be undried by applying the sizing agent liquid to the guide rollThe surface tackiness was 0.2N/cm²Hereinafter, there is no particular limitation as long as the retention/drying of the sizing agent liquid on the surface of the guide roll and the resin accumulation do not occur.

For example, as shown in fig. 2, by providing a sizing agent liquid spray device 6 above the guide roller 3 and spraying the sizing agent liquid from the sizing agent liquid spray device 6, drying of the sizing agent liquid on the guide roller 3 can be sufficiently suppressed. The upper limit of the amount of the sizing agent sprayed from the sizing agent liquid spraying device 6 is not particularly limited as long as the guide roll 3 is wet, but is preferably 50 to 130mg/cm²A more preferable range is 80 to 100mg/cm²And/hr. The spraying amount is less than 50mg/cm²In the case of/hr, the sizing agent liquid may evaporate on the guide roll 3, causing accumulation of resin and occurrence of fuzz and entanglement. The spraying amount is more than 130mg/cm²In the case of/hr, the amount of sizing is excessively used, and therefore, it is disadvantageous in terms of cost.

Further, as shown in fig. 3, by immersing the guide roll 3 in a sizing agent liquid tank 8 different from the sizing agent liquid tank used in the sizing step, the drying of the sizing agent liquid in the guide roll 3 can be sufficiently suppressed.

The sizing agent solution separately applied to the guide roll as in the embodiments shown in fig. 2 and 3 is not particularly limited, but the composition and amount of the sizing agent applied to the obtained carbon fiber bundle are preferably not changed, and more preferably the same as the sizing agent solution for immersing the carbon fiber bundle.

The effect is further enhanced by combining the method of bringing the contact body into contact with the guide roller and the method of separately providing the sizing agent liquid separately from the sizing agent liquid tank 4. For example, as shown in fig. 4, by spraying the sizing agent liquid from the sizing agent liquid spraying device 6 onto the guide roll 3 and then pressing the contact body, it is possible to remove the excess sizing agent liquid while reliably preventing the sizing agent liquid from being fixed, compared with the method of pressing only the contact body, and to adjust the guide roll surface tackiness to a predetermined range.

Further, in the present invention, when the carbon fiber bundle 1 is immersed in the sizing agent liquid tank 4 by the immersion roller 2 and is exposed from the liquid surface by the guide roller 3 to be guided to the drying step which is the next step of the sizing agent applying step, it is preferable to use a guide roller having non-water-contact property as the guide roller 3 in order to prevent the guide roller 3 from generating resin accumulation due to the sizing agent liquid. Specific examples of the guide roller having water repellency include fluorine resin and stainless steel (SUS). In particular, since the carbon fiber bundle to which the sizing agent liquid is applied travels over the guide roller, the guide roller surface is always in a wet state, and therefore stainless steel (SUS) which is not prone to rust is more preferable. Examples of the types of stainless steel include SUS304, SUS304L, SUS316, and SUS 316L.

In the production method of the present invention, after the carbon fiber bundle is immersed in the sizing agent liquid, a sizing agent liquid film is easily formed between adjacent filaments at a position from the liquid surface to the guide roll which is first in contact with the carbon fiber bundle and at a position from the guide roll to the drying step. The sizing agent liquid film may be formed of an excess sizing agent liquid carried out by the carbon fiber bundle immersed in the sizing agent liquid tank, or a sizing agent liquid separately supplied to the guide roller from the sizing agent liquid in the sizing agent liquid tank as described above. If a sizing agent liquid film is formed between adjacent filaments, the adjacent filaments come into contact with each other due to the surface tension of the sizing agent liquid film to generate fuzz, or the sizing agent adhesion spots, drying spots, and color spots of the resulting carbon fiber bundle increase. Therefore, it is preferable to remove the sizing agent liquid film at each position. The method for removing the sizing agent liquid film is not particularly limited, and examples thereof include spraying of a pressurized gas, application of vibration, application of ultrasonic waves, and physical contact by providing a guide. Among these, a non-contact method is preferable in terms of easily preventing the occurrence of fuzz in the carbon fiber bundle, and further, the injection of the pressurized gas is more preferable in terms of suppressing the facility cost to a low level.

In the production method of the present invention, the tension of the carbon fiber bundle in the sizing agent applying step is preferably set to 3.5 to 8.5 cN/tex. When the tension is 3.5cN/tex or more, the reduction of the bundling property of the carbon fiber bundle can be prevented. On the other hand, in the case of 8.5cN/tex or less, the occurrence of fuzz and yarn breakage due to application of tension can be easily prevented. From the above viewpoint, the tension of the carbon fiber bundle in the sizing agent applying step is preferably 3.5 to 8.5cN/tex, more preferably 4.0 to 8.0cN/tex, and still more preferably 4.5 to 7.5 cN/tex. The tension of the carbon fiber bundle in the sizing agent applying step may be controlled solely in the sizing agent applying step, or may be controlled by the same mechanism as the tension in the drying step. The tension control method is not particularly limited, and examples thereof include a method based on adjustment of the ratio of the driving speed before and after the sizing agent application step. The process tension can be determined by measuring the running yarn immediately before the sizing agent liquid is applied by using a tensiometer or the like, and can be adjusted by applying a roller rotation torque before and after the sizing agent liquid.

The carbon fiber bundle is applied with the sizing agent liquid in the sizing agent applying step, dried at about 200 to 300 ℃ in the drying step, and wound around a paper tube. The drying method is not particularly limited, and a contact dryer such as a drum type dryer or a non-contact hot air dryer may be used alone or in combination.

Examples

The present invention is further specifically described by way of examples and comparative examples. Further, each evaluation item in examples and comparative examples was carried out by the following evaluation method.

[ degree of adhesion to guide roll surface ]

The guide roll surface tackiness was calculated by the following equation.

Surface tackiness of roll (N/cm)²) Initial moving force of the carbon fiber bundle/guide roller surface contact area of the carbon fiber bundle.

The starting moving force of the carbon fiber bundle was measured in the following manner after 5 minutes from the stop of the carbon fiber bundle production facility in the case of long-term stable production. That is, as shown in fig. 5, after the guide roller 3 made of stainless steel to which the sizing agent liquid is attached is fixed so as not to rotate, the absolutely dry carbon fiber bundle 1 immediately before the sizing agent liquid is applied is set in a state of hanging down from the uppermost position of the guide roller 3 and having a contact angle of 180 °. Then, a ring is made at one end of the carbon fiber bundle 1. A digital push-pull dynamometer manufactured by アイコーエンジニアリング (manufactured by KANTO K.K.) (RX series, No. RX-10) was used as the load cell 7. A hook ゲージアタッチメント (No. 011B) was attached to the tip of the digital push-pull dynamometer, and the carbon fiber bundle 1 was gradually pulled in the circumferential direction of the guide roller 3 in a state where the hook was hooked on the loop of the carbon fiber bundle 1. The maximum force before the carbon fiber bundle 1 starts moving on the surface of the guide roll 3, that is, the force to start moving the carbon fiber bundle, was measured using a push-pull force meter.

Further, the guide roller surface contact area of the carbon fiber bundle is calculated from the product of the guide roller circumferential length with which the carbon fiber bundle contacts and the filament width of the carbon fiber bundle.

[ quality ]

As the quality of the carbon fiber bundle to which the sizing agent was added, end face fuzz of the bobbin of the carbon fiber bundle after sealing was observed and judged by the following criteria.

◎ the fluff is less than 5 pieces/100 mm²

○ is 5 piles/100 mm²More than 10 pieces/100 mm²

The x is 10 piles/100 mm²The above.

[ example 1]

A sizing agent was applied to a plurality of carbon fiber bundles arranged in parallel in the configuration shown in fig. 1, and the carbon fiber bundles to which the sizing agent was applied were obtained through a drying step.

Specifically, a carbon fiber bundle having 3000 filaments of a polyacrylonitrile-based fiber as a precursor fiber bundle was immersed in a sizing agent liquid tank filled with a sizing agent liquid having a concentration of 3 mass% and containing a bisphenol a-type epoxy resin as a main component, which is an aromatic epoxy compound, and then subjected to a drying step to obtain a carbon fiber bundle to which a sizing agent was added. After the carbon fiber bundle is exposed from the liquid surface of the sizing agent, a guide roller made of stainless steel (SUS) is used as the guide roller 3 to be initially contacted, and a cotton flange cloth having a nap is pressed as a contact body 5 at the lowermost portion of the guide roller 3.

The surface tackiness of the guide roll 3 was 0.05N/cm²The end face fluff quality is extremely good. The results are shown in table 1.

[ example 2]

As the contact body 5, a wiper made of plastic was used instead of cotton flannel having napExcept for the above, a carbon fiber bundle to which a sizing agent was added was obtained in the same manner as in example 1. The surface tackiness of the guide roll 3 was 0.07N/cm²The end face fluff quality is extremely good. The results are shown in table 1.

[ example 3]

A carbon fiber bundle to which a sizing agent was added was obtained in the same manner as in example 1, except that the sizing agent addition step was changed to the step shown in fig. 2. That is, the same operation as in example 1 was performed except that the sizing agent liquid was sprayed from the upper portion of the guide roll 3 which the carbon fiber bundle first contacted after being exposed from the sizing agent liquid surface, and the contact body was removed. The amount of the sizing agent solution sprayed at this time was set to 100mg/cm²And/hr. The surface tackiness of the guide roll 3 was 0.04N/cm²The end face fluff quality is extremely good. The results are shown in table 1.

[ example 4]

The spraying amount of the sizing agent liquid was changed to 80mg/cm²A carbon fiber bundle was obtained in the same manner as in example 3 except that the amount of carbon fiber was changed. The surface tackiness of the guide roll 3 was 0.13N/cm²The end face fluff quality is good. The results are shown in table 1.

[ example 5]

A carbon fiber bundle to which a sizing agent was added was obtained in the same manner as in example 1, except that the sizing agent addition step was changed to the step shown in fig. 3. That is, in example 1, the same operation as in example 1 was performed except that the guide roller 3, which was first contacted after the carbon fiber bundle was exposed from the surface of the sizing agent liquid, was immersed in another independent sizing agent liquid bath 8 and the contact body was removed. The surface tackiness of the guide roll 3 was 0.08N/cm²The end face fluff quality is good. The results are shown in table 1.

[ example 6]

A carbon fiber bundle to which a sizing agent was added was obtained in the same manner as in example 1, except that the sizing agent addition step was changed to the step shown in fig. 4. I.e., at a spray volume of 80mg/cm²The same operation as in example 1 was performed except that the sizing agent liquid was sprayed to the carbon fiber bundle fed from the guide roll 3. Surface adhesion of the guide roll 3The degree is 0.02N/cm²The end face fluff quality is extremely good. The results are shown in table 1.

[ example 7]

A carbon fiber bundle to which a sizing agent was added was obtained in the same manner as in example 1, except that the sizing agent liquid tank was filled with a sizing agent liquid having a concentration of 2 mass% and containing polyurethane as a main component. The surface tackiness of the guide roll 3 was 0.06N/cm²The end face fluff quality is extremely good. The results are shown in table 1.

Comparative example 1

A carbon fiber bundle to which a sizing agent was added was obtained in the same manner as in example 1, except that the sizing agent addition step was changed to the step shown in fig. 6. That is, the same operation as in example 1 was performed except that the cotton flannel as the contact body was not pressed. As a result, the sizing agent was dried on the guide roll to cause resin accumulation, and the surface tackiness of the guide roll 3 was increased to 0.25N/cm²The running carbon fiber bundle is fluffed, and the end face fluff quality is remarkably deteriorated. The results are shown in table 1.

[ Table 1]

Description of the symbols

1: carbon fiber bundle

2: impregnation roller

3: guide roller

4: sizing agent liquid groove

5: contact body

6: sizing agent liquid spraying device

7: load measuring instrument

8: a sizing agent tank different from the sizing agent tank 4.

Claims

1. A method for producing sizing agent-added carbon fiber bundles, which comprises a sizing agent adding step of immersing a plurality of carbon fiber bundles in parallel in a sizing agent tank, and a drying step of obtaining sizing agent-added carbon fiber bundlesA method for producing a carbon fiber bundle, wherein the carbon fiber bundle is immersed in a sizing agent tank, and the adhesion of the surface of the guide roll of the first guide roll after the carbon fiber bundle is exposed from the liquid surface of the sizing agent tank is 0.2N/cm²The following.

2. The method for producing a carbon fiber bundle provided with a sizing agent according to claim 1, wherein the guide roll surface tackiness is 0.2N/cm by bringing the contact body into contact with the guide roll²The following.

3. The method for producing a carbon fiber bundle with a sizing agent according to claim 1, wherein after the sizing agent applying step, a sizing agent solution is further applied to make the guide roll surface tackiness 0.2N/cm²The following.