JPS6052206B2 - Method for manufacturing acrylic carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an industrially advantageous method for producing high-performance carbon fiber that can exhibit excellent suitability as a reinforcing material. The present invention relates to a method for producing carbon fibers, which is characterized in that the carbon fibers attached to precursors are fired in the process.

Conventionally, acrylonitrile-based fibers have been known to be useful as precursors for producing carbon fibers, but the disadvantages of acrylonitrile-based precursors are that they form fluff during firing, which impedes passage through the firing furnace; It has been pointed out that fusion and adhesion occur between fibers, which impairs the durability of the resulting carbon fibers.

As a method to improve such defects, for example, 1 to 6% by weight of oil agents such as fatty acid esters, higher alcohols, higher alcohol sulfates, alkylbenzenesulfonic acids, and nonionic surfactants are attached to fibers in a water-swollen state. A method using fibers with a sparse surface structure with a specific surface area of 2 to 7-1y as a precursor was published in Japanese Patent Publication No. 49-16.
No. 66, however, this method is still not sufficient to achieve the above object. Also,
As another method, a method of treating an acrylonitrile precursor with alkyl silicone, phenyl silicone, or a condensate thereof is proposed in JP-A-49-117724, but the precursor obtained by this method also During the firing process, friction with yarn guides, rollers, etc. occurs, and static electricity accumulates in the fibers, causing problems such as fuzzing, spreading, and breakage of the yarns, resulting in the creation of the carbon fibers that are the object of the present invention. That's difficult. Still another method is to impregnate or contain 0.01% by weight or more of an aminosiloxane with a specific structure into a water-swollen fiber in a precursor stock solution or in a method disclosed in JP-A-51-116225. No. or JP-A-52-3
It is proposed as No. 4025. In this method, aminosiloxane is trapped inside the fiber structure, and by heat-treating the fiber, aminosiloxane is mutually trapped inside the fiber.
Alternatively, a crosslinked structure is formed between an acrylonitrile polymer and an aminosiloxane, and even when the precursor is subjected to external force, it prevents the occurrence of cracks centered on the board inside the precursor, and prevents carbon from forming due to fluff during firing of the precursor. The purpose of this method is to prevent fiber breakage and process troubles. However, in this method, aminosiloxane is strongly bonded inside the fiber as a precursor, so the fiber accumulates static electricity during firing, and the static electricity causes damage to the single yarn. It is difficult to prevent thread breakage due to fuzzing, spreading, etc. Furthermore, in order to impregnate the board-like fibers with aminosiloxane, the method of impregnating and drying it to form a precursor is a method in which if aminosiloxane is attached to the fiber surface, the molecular weight of the aminosiloxane attached to the surface increases when the precursor is dried. This can cause problems such as sticking to guides, rollers, etc. and stopping the process.
Since this precursor is hard and difficult to produce high-performance carbon fiber by firing, it is not preferable to attach siloxane to the surface of the precursor in this method, and the carbon fiber manufacturing process becomes extremely sensitive, resulting in significant improvements from an industrial standpoint. It is hoped that this will be done.
Therefore, the inventors of the present invention have developed a fiber that does not cause any trouble in the manufacturing process of the precursor, is properly opened during firing, does not cause problems such as fusion or adhesion, and has good bundling properties during the carbonization process. We are currently considering a method for manufacturing carbon fiber that can be fired in a dry state, using a method that involves attaching a silicone oil that can be dispersed in water to acrylonitrile fibers that are manufactured by the usual method after drying, that is, containing almost no board. By using the precursor as a precursor,
The inventors have completed the present invention by discovering that it is possible to achieve the above objectives and to produce carbon fibers with high elasticity and high strength.

In the present invention, a water-dispersible silicone oil agent is attached to substantially board-free acrylonitrile fibers that have been spun, drawn, washed, and dried in a proportion of 0.1 to 2.5% by weight calculated as fiber weight. A method for producing carbon fiber characterized by firing an acrylonitrile fiber and carbonizing or graphitizing it, and in the above method, the acrylonitrile fiber without a board has a fiber weight of 3 to 25
The method uses as a precursor an acrylonitrile fiber to which 0.1 to 2.5 weight % of water and a water-dispersible silicone oil are attached in a ratio of 0.1 to 2.5 weight % in terms of fiber weight.

The acrylonitrile fiber used in carrying out the present invention is preferably a polymer containing 90 mol % or more of acrylonitrile.

Examples of copolymerized components other than acrylic acid include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, α
- Esters of acrylic acid or methacrylic acid such as methylene glutaric acid, methyl acrylate, methyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide or methacrylamide, N-alkoxymethylacrylamide or methacrylamide, N
Amide derivatives such as -N-dimethylacrylamide, vinyl ketones such as methyl vinyl ketone and ethyl vinyl ketone, acrolein, methacrolein, vinyl pyridines, vinyl sulfonic acids such as sodium methacryl sulfonate and sodium styrene sulfonate, vinyl acetate, and methacrylate. Examples include lonitrile. Acrylonitrile polymers are preferably produced by conventional methods such as solution polymerization, aqueous suspension polymerization, and emulsion polymerization using conventional polymerization catalyst systems such as radical polymerization and redox polymerization. To make the acrylonitrile fiber used in carrying out the present invention, the fiber produced as described above is dissolved in an organic solvent such as dimethylacetamide, dimethylformamide, or dimethyl sulfoxide to prepare a spinning stock solution.
Yarns are formed by a wet or wet-dry method using a solvent-aqueous coagulation bath, and the yarns that come out of the coagulation bath are washed, stretched, dried and densified, and then made into a silicone-based material that exhibits water dispersibility. It may be treated with a compound and, if necessary, contain water in an appropriate proportion.

The silicone oil agent that exhibits dispersibility in water used in carrying out the present invention has the formula /-\ (wherein, R1 is -R(H-℃H2, -R''-NH2
or -R'-N(R'')2, where R'' is -(CH2+
-*(In the formula, X..y is the same as above, A..b is 1 to 10
(indicates an integer of ).

The process of adhering the silicone oil to the acrylonitrile fibers described above requires adhering to the acrylonitrile fibers that have virtually no board after washing, stretching, and drying. In addition to various process troubles occurring in the treatment of oil-based oils, the properties of the resulting carbon fibers are also unsatisfactory in strength and modulus compared to the carbon fibers produced by the method of the present invention. So I don't like it.

In addition, the silicone oil can be applied by dissolving the silicone oil in a solvent such as toluene, acetone, methyl ethyl ketone, etc., but the most preferable method is to use a treatment agent in which the silicone oil is dispersed in water. The amount of silicone oil based on the fiber weight is 0.1 to 2.5.
In this method, the adhesion treatment is performed so that the proportion of water is 3 to 25% by weight.

As mentioned above, the acrylic precursor used in the present invention is treated with a silicone oil, especially containing 3 to 25% by weight of water.
Precursor containing a proportion of However, it does not cause abnormal fluffing or spreading due to charging, and it extremely efficiently prevents fusion and adhesion during firing, so it has excellent continuous firing properties, and has high elasticity and high properties. It is possible to make strong carbon fiber.

This can be achieved by attaching a specific amount of the water-dispersible silicone oil specified in the present invention to the acrylic fibers that have substantially no board: ', , R'' is CmH2.
．． +1 group, X. ．． y is an integer from 0 to 15, M, . n
represents an integer from 1 to 3) or the formula, and the effect can be further enhanced by further adding water to this system.

Furthermore, the above-mentioned effects can be further enhanced by adding amines such as dimethylamine and diethanolamine during the treatment of silicone oils.

The present invention will be explained in more detail with reference to Examples below.
A few supplementary notes regarding the measured values in the examples.

A copolymer with a specific viscosity of 0.10 g was added to a dimethylformamide (referred to as DMF) solution containing 0.1N in a sorter.
It was dissolved in 0 mt and measured at 250°C.

Fiber adhesion amount of silicone compound Secondary X-ray intensity of silicon generated by irradiating X-rays to fiber bundles arranged in a certain shape using a fluorescent X-ray analyzer (Rigakuden 4a! GF-S type) Measure.

This is a method of determining the amount of adhesion for which the amount of adhesion is unknown from a calibration curve obtained for a fiber bundle whose amount of adhesion is known. Strand strength and modulus shell chemistry epoxy resin (Epicote 8
28) A bundle (strand) of carbon fiber impregnated and cured with a sample length of 200T1r! n1 deformation speed 5Tn! It was determined by conducting a tensile break test at n/min.

Tow strength was determined by conducting an elongation rupture test on a bundle of carbon fibers drawn parallel to each other with a trial length of 100 pieces and a deformation rate of 1 WrIn/min.

Even if carbon fibers have high strand strength and appear to exhibit fairly excellent performance, if the tow strength is less than 6 to 7 V1d, the fiber bundles will easily break when tension is applied during the process of forming the composite material. There is a possibility that it could be done.

Example 1 Using a redox catalyst consisting of potassium persulfate and acidic sodium sulfite, continuous aqueous suspension polymerization was carried out at a temperature of 50°C to produce 97.0 mol% of acrylonitrile (hereinafter referred to as AN) and methyl acrylate (hereinafter referred to as AN). methacrylic acid (hereinafter referred to as MAA) 0.5 mol%
A copolymer having the composition was prepared.

The specific viscosity of this copolymer was 0.221. 21 parts of this copolymer was uniformly dispersed in a portion of dimethylacetamide (hereinafter referred to as DMAc), heated to a temperature of 80°C to dissolve it, and further defoamed and filtered to obtain a stock solution for spinning. . The viscosity of the spinning dope was 510 poise at 50°C.
Using this spinning stock solution, the number of pores is 100,001 and the pore diameter is 0.065.
T! r! ! A filament bundle was formed by a wet spinning method in which the filament was discharged through a tφ spinneret into a coagulation bath at 35° C. having a composition of 68% DMAc and 32% water. What about coagulated threads? The fibers were stretched 8.4 times using a drawing machine with a warm water bath at 100°F, and at the same time the fibers were washed to reduce the solvent content to 0.1%.A post-process oil was applied to the fibers in an amount of 0.1% based on the weight of the fibers. The fibers are passed over cylinder rollers heated to 130°C to dry and remove moisture, and are densified into transparent fibers (this is called dry fiber).

The dry fiber had a weight fineness of 14,383 denier, a tensile strength of 5.4 fId1, and an elongation at break of 11.2%.

The moisture content was 1.2%, and the cross-section of the fiber observed with a scanning electron microscope showed a smooth texture, with neither large boards nor small boards (interfibril voids) often seen in wet-spun fibers observed. The dried fibers were then subjected to a 2% shrinkage treatment in atmospheric steam, silicone treated to form an aqueous dispersion, and then wound up. The silicone aqueous dispersion was prepared by diluting a mother liquor (manufactured by Nippon Unicar Co., Ltd.: aminosiloxane dispersion) consisting of 1 (1) part of UCC silicone Y-6165 and 15 parts of polyoxyethylene nonyl phenyl ether with water. The moisture content of the fibers was measured immediately after winding them up and after drying these fibers at a hot air temperature of 105° C. for 3 hours. The amount of silicone solids adhered was adjusted to be as shown in Table 1. Table 1 shows the performance of the raw material fibers after the adhering water was air-dried and removed.
The UCC silicone Y-6165 used is said to have a chemical composition shown by the following formula, and as a result of analysis, the elemental composition ratio is 34.4% carbon and 8.6% hydrogen.
, 0.4% nitrogen, and the silica content was approximately 35%.

The fibers shown in Table 1 were fired into carbon fibers by a conventional method.

That is, the fiber bundle was continuously fed by roller drive into a flameproofing furnace in a hot air atmosphere having a temperature gradient in the range of 225 to 260°C, and was left there for 34 minutes to perform flameproofing treatment. The tension during the flameproofing treatment was approximately 120 m91d, and the fiber length was maintained at approximately the original length. The density of the flame-resistant fibers is 1.
It was in the range of 37 to 1.39 y'd. The flame-retardant fibers were heated in a carbonization furnace with a temperature gradient in the range of 320 to 700C and a heat treatment furnace at 1350C in a nitrogen gas atmosphere.
The carbon fibers were fired with a residence time of 4.5 minutes and 4.5 minutes.

The physical properties of the obtained carbon fibers were as shown in Table 2. As shown in Table 2, sample numbers 1 to 3 related to the present invention
The carbon fiber had excellent physical properties.

Comparative Example In the spinning process of the raw material fiber of Example 1, drawing,
After washing, the fibers including the board were treated with the amino silicone aqueous dispersion used in Example 1 as a process lubricant so that the amount of silicone adhesion was 0.2 to 0.5%.

When this aminosiloxane-adhered fiber was fed to a heated cylinder roller in the next step to dry it, the aminosiloxane adhered and deposited on the roller, and the amount of the aminosiloxane deposited increased over time as the molecular weight increased. .

As this phenomenon occurred, the fiber bundle dried by the heating roller began to become fluffy at the portions that came into contact with the sticky deposits, and was cut and could no longer be wound up.

When the set silicone adhesion amount was 0.2%, the fluffing start time was 4 hours and 2 powders, and when the silicone adhesion was 0.5%, it was 1 hour and 1 powder. Some of the fibers that could be wound up were tried to be fired into carbon fibers using the method described in Example 1.
When flame-retardant treatment was performed, broken single yarn fuzz wrapped around the roller, making continuous feeding impossible. Example 2 By the method of Example 1, an AN copolymer having a composition of 98 mol % AN and 2 mol % MAA was prepared.

The specific viscosity of this copolymer was 0.201. Copolymer A was made into a spinning stock solution with a polymer concentration of 23.3% using DMF as a solvent. Dissolution is performed by uniformly dispersing at a low temperature and then heating at a temperature of 80°C, and the viscosity of the spinning stock solution at 50°C is 7.
It was 00 poise. The spinning stock solution was kept at 60° C., then simultaneously discharged from four nozzles each having 500 holes and a hole diameter of 0.15 mφ, and was then guided into a coagulation bath through a gap of approximately 3 WR for spinning. Coagulation bath composition is DMF6O%,
The water content was 40%, and the bath temperature was 40°C.

After the coagulated threads were individually washed to remove the solvent in a 55°C water bath,
The film was stretched 6 times in a hot water bath at 30°C. The drawn fibers are bundled into a fiber bundle of 2,000 filaments, coated with 0.12% process oil, and then passed over heated cylinder rollers for 12 cycles to dry and form fibers without boards. did. The dried fibers were post-stretched by a factor of 1.5 in a heated steam atmosphere at 103° C., and then subjected to a relaxation shrinkage treatment of 5% in normal pressure steam. Then,
The aqueous silicone dispersion used in Example 1 was applied and then rolled up. The yarn properties of the fibers taken here were as follows. That is, when the fibers were fired in exactly the same manner as in Example 1 except that the residence time for flame resistance was changed to 27 minutes, the flame resistance fiber density was 1.394 q'd.

The strand strength of the obtained carbon fiber was 315 kgIi1
Same elastic modulus 22.5t0nIi1 tow strength 12.3VId
It had excellent physical properties. Example 3 In Example 1, when the obtained dry fibers were subjected to a 2% shrinkage treatment in normal pressure steam and then treated with a silicone aqueous dispersion, the types of silicone compounds used in the silicone aqueous dispersion were as follows. I changed it to something like the one shown and rolled up the fibers.

The following silicone compounds were used.

However, R1, R2 and R3 are -CH3, x is an integer of ≧15, and the viscosity measured at 25°C is about 500 centistokes.

However, R4 is -C3H7, X. ．． Y is an integer of ≧15, 2
The viscosities measured at 5° C. are approximately 25 αB), 500 (C) and 1000 sense Stoke (9).

(E) In the structural formula of formula (2), R4 is
outside "-""-??n"" and the epoxy group is about 1
Included in weight.

The viscosity measured at 25°C is 5000-7000 centistokes.

X. ．． Y is an integer greater than or equal to 15. The viscosity measured at 25° C. is about 200 centistokes.

In addition, when using the silicone compound (4), Corn water dispersion 10? A system was prepared in which 0.5 parts each of dimethylamine and diethanolamine were added to each sample, and was applied to fibers.

The filament properties of the obtained fibers were as shown in Table 3.

The fibers of sample numbers 5 to 12 were fired into carbon fibers by the method shown in Example 1.

In addition, the density of the flame-resistant fiber is 1.403f in the case of sample number 6.
For ICII17 it is 1.396y1c! The values other than 1 were in the range of 1.37 to 1.39y1cf1. The physical properties of the obtained carbon fibers are as shown in Table 4, and all showed excellent carbon fiber performance.

Claims (1)

[Claims] 1 Spun, stretched, washed, and dried acrylonitrile fiber with virtually no voids containing 3 to 30% by weight in terms of fiber weight.
Acrylonitrile fibers to which 25% by weight of water and a water-dispersible silicone oil are attached at a ratio of 0.1 to 2.5% by weight in terms of fiber weight are fired to carbonize or graphitize them. Characteristic carbon fiber manufacturing method.