JPH0663133B2 - Carbonaceous fiber having acidic groups - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbonaceous fiber having an acidic group, and more specifically to a carbonaceous fiber having a stable acidic group, particularly a carbonaceous fiber by a floating method. Is.

(Prior Art) Carbonaceous fiber is a raw material that has been rapidly expanding in recent years as various composite materials due to its excellent mechanical properties. Conventional carbon fibers have been manufactured by a method such as sintering organic carbon to carbonize, but recently carbon fiber has been manufactured by a vapor phase method in which carbonaceous fibers are produced by thermal decomposition and catalytic reaction of hydrocarbons. Attempted (eg industrial materials, Showa 57)
July issue, p.109, Endo, Koyama and JP-A-58-180615
Issue).

Carbon fibers obtained by the vapor phase method have excellent crystallinity, orientation and high strength as compared with conventional ones, and nonwoven fabrics, laminates and the like obtained from the fibers have electrical conductivity. Therefore, it is about to be used for an electrode material of a battery, a heating element, etc., and a filter, a catalyst carrier, etc. by utilizing its heat resistance and chemical resistance.

(Problems to be solved by the invention) However, the conventional carbonaceous fiber by the vapor phase method is for growing the carbonaceous fiber on the substrate or for growing the carbonaceous fiber with the ultrafine powder of the metal dispersed on the substrate. In addition, the obtained fiber diameter is relatively large, and when it is used in a composite material with a resin, the adhesiveness with the resin is not good and there is a problem in practical use.

Further, in general, conventional carbonaceous fibers have poor wettability, and therefore the adhesiveness with a resin becomes an important issue. For this reason, surface modification methods have been studied for various existing carbon fibers, and for example, chemical reactions in a liquid phase or a gas phase, plasma treatment, and the like have been investigated. It cannot be said that the group has a stable group, and sufficient adhesiveness could not be obtained.

The present inventors introduced a hydrocarbon and a specific organometallic compound together with a carrier gas into a heating zone, and thermally decomposed and catalytically reacted the hydrocarbon to obtain a carbonaceous fiber having an extremely thin and unique structure. We found that it could be synthesized and filed a patent application (Japanese Patent Application No. 59-83495 and Japanese Patent Application No. 59-83495).
-231967, 59-253550, etc.).

(Means for Solving Problems) The inventors of the present invention have investigated various chemical reactivity of the carbonaceous fiber, and found that the fiber has extremely high reactivity, and particularly stabilizes an acidic functional group. The inventors have found that they can hold the present invention and arrived at the present invention.

The carbonaceous fiber of the present invention has a fiber diameter of 0.01 to 4 μm, a fiber length / fiber diameter of 20 or more, a crimp number of 1 or more, and a crimp degree.
10 to 50%, the amount of acidic functional group by titration method is 0.5 to 500 μmol
/ G, oxygen concentration O ₁ s / C by X-ray spectroscopy (ESCA)
₁ s is 0.05 or more, and a layer of graphite or a carbon that is easily converted into graphite is formed by arranging in a ring shape parallel to the longitudinal axis,
It is characterized by having an acidic group.

The carbonaceous fiber of the present invention has a diameter of 0.01 to 4 μm, preferably
It is 0.05 to 3 μm (particularly 0.07 to 2.5 μm). When the diameter of the fiber is larger than this, the degree of entanglement of the fiber is lowered and the desired properties cannot be obtained. The fiber length (L) / fiber diameter (D) is 20 or more, preferably 50 or more (especially 100 or more).
Is. If the L / D is less than 20, sufficient entanglement cannot be obtained when the fibers are assembled, and the desirable properties deteriorate.

The carbonaceous fiber of the present invention has a crimp number of 1 or more and a crimp degree of 10 to 50%. In this case, the number of crimps means the total number of peaks and troughs of a fiber having a fiber length of 20 μm using an observation photograph of a scanning electron microscope, and the degree of crimp means a straight line between a and b between two points of the fiber. At a distance
40 μm is taken, and the actual fiber lengths a and b in the meantime are measured by a planimeter and calculated by the following formula (average value of 5 measurements at random).

If the number of crimps and the degree of crimp are too small, the entanglement between the fibers becomes less when the aggregate or the deposit is formed, and the electrical conductivity and the like decrease.

When observed with an electron microscope, it was found that the carbonaceous fiber of the present invention was formed by arranging graphite or a layer of carbon which is easily converted into graphite in an annual ring shape parallel to the longitudinal axis. . The carbonaceous fiber of the present invention is a generic term for carbon fiber and graphitized fiber.

Further, the carbonaceous fiber of the present invention has an amount of acidic functional groups of 0.5 to 200 (particularly 1 to 50) μmol / g as determined by a titration method. The amount of acidic functional group by this titration method is determined by the following method. That is, about 5 g of the sample is weighed in a 500 ml stoppered Erlenmeyer flask, and water 1
Accurately add 00 ml, 1/50 NaOH 40 ml with a whole pipette, and add 60 ml of water to make 200 ml.
After leaving it for a minute, it is immersed in an ultrasonic shaker for 15 minutes, 50 ml of the solution is taken into a Dharma flask with a whole pipette, and titrated with 1/50 N HCl. For the titration, the amount of functional groups is determined from the titration curve using a Metrohm potentiometric titrator.

If the amount of this acidic functional group does not reach 0.5, sufficient adhesiveness cannot be obtained when mixed with resin, binder, etc.
When it exceeds μmol / g, the peculiar properties of the carbonaceous fiber are deteriorated, which is not preferable.

The oxygen concentration of the carbonaceous fiber of the present invention by X-ray photoelectron spectroscopy (ESCA), that is, the relative integrated intensity of O ₁ s with respect to C ₁ s (O ₁ s / C ₁ s) is 0.05 or more, preferably 0.07 or more, It is preferably 0.1 or more. The relative integrated intensity (O ₁ s / C ₁ s) in this case was measured using an X-ray photoelectron spectrometer, using AlKα1486.6eV as the excitation X-ray, and measuring the X-ray output 1
0 kV, 20 mA, temperature 40 ° C. vacuum degree of 10 ^- was measured at ⁹ torr. _O 1 s from the obtained spectra for _{C 1} s
Was calculated as the index of the amount of oxygen-containing functional groups on the carbon fiber surface. If this value is less than 0.05, the acidic groups are not sufficient, and the adhesiveness with the resin or the like decreases.

The fiber of the present invention, the half width of the C _{1 s} band in ESCA is 1.6eV or less, in particular shows the following sharp band peak 1.5 eV, and has a homogeneous structure.

The carbonaceous fiber of the present invention requires a fiber obtained by introducing a mixed liquid of a hydrocarbon and a specific organometallic compound into a heating zone together with a carrier gas, if necessary, to thermally decompose and catalytically react the hydrocarbon. It is produced by introducing an acidic functional group after heat treatment according to the above.

The hydrocarbons are not particularly limited, at room temperature including anthracene, naphthalene, etc. solid hydrocarbons at room temperature, benzene, toluene, xylene, styrene, hexane, isooctane cyclohexane, cyclopentadiene, etc. Liquid hydrocarbons, or methane,
It may be any of gaseous hydrocarbons including ethane, propane, butane, ethylene, propylene, butylene, butadiene, acetylene and the like.

Examples of the organometallic compound used in the present invention include those listed in the periodic table.
Group IVa (especially Ti, Zr), Group Va (especially V), Special group VIa (especially Cr, Mo, W), Group VIIb (especially Mn), Group VIII (especially
Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) compounds, especially cyclopentadienyl metal compounds, carbonyl metal compounds, benzene-metal compounds, alkyl, allyl or alkynyl metal compounds , Β-diketone metal complexes, keto acid ester metal complexes, metal carboxylates, among these, especially bis (cyclopentadienyl)
Iron such as iron, cyclopentadienyl compound such as nickel or cobalt, iron carbonyl, nickel carbonyl,
Cobalt carbonyl, iron such as cyclopentadienylcarbonyl iron, carbonyl compounds such as nickel or cobalt, iron such as iron complex of di- or triacetylacetone, β-diketone metal complex such as nickel or cobalt, di- or triacetoacetic acid ester Iron such as iron complex, nickel or cobalt complex, iron such as iron fumarate and iron naphthenate, fumarate such as nickel or cobalt, carboxylate of higher hydrocarbon, or a derivative thereof gives good results.

As the method of supplying the organometallic compound, these are directly heated to be supplied to the reaction system in a gas state, or the organometallic compound is dissolved or finely dispersed in a liquid of hydrocarbon and heated to react. A method of supplying or jetting to the system is used.

The amount of the organometallic compound supplied (% by weight supplied per minute) is 0.01% by weight or more, preferably 0.05% by weight or more, and particularly 0.2% or more with respect to the mixture with the hydrocarbon. If the amount of organometallic compound is too small, it will be difficult to form fibrous substances,
Granules tend to increase.

The temperature range for introducing hydrocarbons and organometallic compounds is 1500 ° C
The following, preferably 100 ~ 1300 ℃, particularly preferably 100 ~ 50
A position of 0 ° C is suitable. If the temperature at the introduction position is too low, it is difficult to maintain the gas phase of the raw material, and it is not preferable for activation of the organometallic compound. Further, if it exceeds 1500 ° C, carbonization is likely to occur to increase the production of particulates, causing clogging and decreasing the fiber yield. The reaction heating temperature range is preferably 500 to 1800 ° C, particularly 800 to 1500 ° C.
If the temperature of the reaction part is out of the above range, particulate matter is likely to be produced.

In the present invention, in order to introduce an acidic functional group into the carbonaceous fiber, a known method, for example, a gas phase oxidation method, an electrolytic solution phase oxidation method,
An oxidant liquid phase oxidation method, a plasma treatment method or the like can be used. For example, in the gas phase oxidation method using air, oxygen, ozone, etc., when ozone is used, the ozone concentration is 0.
The treatment temperature is preferably 1 to 5% by weight, and the treatment temperature is preferably 30 to 300 ° C. When air is used, it is usually desirable to carry out in heated air at 350 to 800 ° C. If necessary, oxygen diluted with an inert gas may be mixed into the air to adjust the oxygen concentration. When the electrolytic solution-phase oxidation method is used, it is performed by using a carbonaceous fiber as the anode and applying a voltage between the carbon fiber and the cathode plate in the electrolytic solution. In the case of the oxidant liquid phase oxidation method, for example, nitric acid, hypochlorous acid, chromate, dichromate, chromic anhydride, permanganate, etc. are dissolved in water or an organic solvent, and necessary. The carbonaceous fiber may be treated with the heated material according to the above. Further, the plasma treatment method is, for example, a glow method in which a gas containing oxygen, oxygen and carbon monoxide, carbon dioxide, and a gas containing an organic matter as necessary are circulated under reduced pressure in an internal electrode type low temperature plasma generator having a pair of discharge electrodes. It suffices to discharge. In this case, the oxygen concentration in the gas is preferably 10% by weight or more. Helium,
The acidic functional group can also be introduced by contacting with an unsaturated carboxylic acid after plasma treatment with an inert gas such as neon, argon or nitrogen. The atmosphere pressure in the plasma device is preferably in the range of, for example, 0.001 to 10 torr, and stable under such gas pressure by applying 10 W to 100 KW of power at a high frequency of 10 KHz to 10 MHz between the discharge electrodes. Glow discharge can be performed. In addition to the above high frequencies, low frequencies, microwaves, direct current, etc. can be used as the discharge frequency band. Since the introduction of such acidic functional groups has high reactivity of the carbonaceous fiber used as a raw material, a large amount of acidic functional groups (eg, carboxyl group, phenolic hydroxyl group, etc.) is introduced under mild conditions without weight loss. can do.

(Effects of the Invention) The carbonaceous fiber having an acidic group of the present invention has a large amount of acidic functional groups without deteriorating the characteristics of the carbonaceous fiber itself, and thus when used as a composite material, the base material Excellent adhesion to resin (especially reactivity with epoxy resin), eg OA
Anti-static parts such as equipment, fields requiring electrical conductivity such as electrode materials, fields generating high heat (automobile engine related)
It is effectively used as a fiber for composite materials, such as the above-mentioned parts, parts in the field requiring thermal conductivity, and the like.

Hereinafter, the present invention will be specifically described with reference to examples.

(Example 1) Using the apparatus shown in FIG. 1, carbonaceous fibers having an acidic group of the present invention were produced. This device is a raw material liquid mixed with a catalyst.
A reaction tower (reaction part) 7 in which a nozzle (for example, a two-fluid nozzle) 3 for ejecting 11 with a carrier gas (hydrogen and argon) 9, a heater 5 and a cooling nozzle 15 are sequentially provided.
And a recovery part (bag filter) 17 communicating with the lower part of the reaction tower 7 via a communication part 21. In the figure, 13 is a cooling gas (for example, nitrogen gas), and 19 is an exhaust gas. Using the above-mentioned apparatus in which the volume of the reaction tower 7 is 40, a mixture of styrene containing 0.5% by weight of iron pentacarbonyl and 0.1% by weight of bisacetylacetonato iron is mixed as a raw material with 50% by volume of hydrogen and 50% by volume of argon. The gas was jetted from the nozzle 3 into the reaction tower 7 as a carrier gas. The temperature in the vicinity of the heating section in the tower was 1050 ° C., and the spraying state was adjusted so that the sprayed raw material did not directly collide with the heater 5. Nitrogen gas is ejected as a cooling gas from the nozzle 15 in the lower part of the reaction tower 7 to cool the produced carbon fibers and to entrain the produced carbon fibers in the bag filter 17 through the communicating portion 21 so as to collect the produced carbon fibers. I chose Raw material styrene 4g / min, mixed gas of hydrogen and argon 0.5 / mi
When the reaction time was 30 minutes with a cooling gas of 1 / min, the diameter was 0.23 μm, L / D200 or more, crimping degree 12%, X
The (002) plane spacing d _{0 0 2} is 3.52 Å, the crystal size Lc ( _{0 0 2} ) in the c-axis direction is 35 Å, and the half-width of C ₁ s is 1.44 eV in X-ray photoelectron spectroscopy (ESCA). A carbonaceous fiber was obtained.

This carbon fiber was treated with 68% concentrated nitric acid for a predetermined time. The processing conditions are as shown in Table 1. The treated carbon fiber was washed with ion-exchanged water for about 1 hour and then dried in an oven at 120 ° C. for 30 minutes to evaluate the treated product. X
Oxygen concentration (O ₁ s / C ₁ by line photoelectron spectroscopy (ESCA)
s) and the method for measuring the amount of acidic functional group by the titration method are as described above.

(Comparative Example 1) Alumina furnace core tube (inner diameter 10 cm, length 100 cm) in an electric furnace.
Was installed horizontally, and a graphite substrate with ultrafine Fe powder (300 Å under) sprinkled therein was set. The board is 5 cm wide and 30 c long
The particle size was 0.5 m, the thickness was 0.5 cm, and the ultrafine powder was sprayed by suspending it in ethyl alcohol. The spraying was performed almost uniformly on the substrate, and the amount of the ultrafine powder sprayed was about 1 mg. A gas introduction pipe was connected to one end of the furnace core tube, and a discharge pipe was connected to the other end, and 1000 cc (normal temperature) of hydrogen gas containing 10% by volume of benzene vapor was passed through the gas introduction pipe. And temperature 10
The temperature was raised to 00 ° C. and the temperature was maintained for 180 minutes. Then, the temperature was raised to 1200 ° C. and the temperature was maintained for 60 minutes. After that, the gas was switched to nitrogen and cooled, and the substrate was taken out. The produced carbon fiber was taken out from the substrate and weighed. as a result,
A carbon fiber having a fiber diameter of 10 μm was obtained at 0.033 g / cm ² · hr (JP-A-57-117622).

Half width of the diameter of the carbon fibers _{10μm, d 0 0 2} is 3.52Å, _{C 1} s in ESCA was 1.72 eV. About this fiber
Treatment was performed with 68% concentrated nitric acid as shown in Table 1.

(Comparative Example 2) A copolymer consisting of 99.5 mol% of acrylonitrile (AN) and 0.5 mol% of itaconic acid and having an intrinsic viscosity (η) of 1.80 was blown with ammonia to substitute the carboxyl group-terminated hydrogen of the copolymer with an ammonium group. Then, a modified polymer was prepared, and a dimethyl sulfoxide (DMSO) solution having a concentration of the modified polymer of 20% by weight was prepared. This solution was used as a furnace material and filtered using a sintered metal filter having an eyelid of 5μ,
The temperature was adjusted to 60 ° C, and the mixture was discharged into a DMSO aqueous solution having a temperature of 60 ° C and a concentration of 50%. The die used had a hole diameter of 0.05 mm and the number of holes was 4500, and the solidification take-off speed was 18 m / min. After washing the coagulated yarn with water and stretching it 4 times in hot water, after treating it with a silicone-based oil agent, it was dried and densified by contact with the roller surface heated to 130 to 160 ° C, and then 40 kg / cm ³ Was stretched three times in a pressure steam of No. 58 to obtain a fiber bundle having a single yarn fineness of 0.7d and a total denier of 3150D (Japanese Patent Laid-Open No. 58-214527).

The carbon fiber ( _{0 0 2} ) plane spacing d _{0 0 2} is 3.68Å, ESCA
The full width at half maximum of C ₁ s at 1.85 eV was 1.85 eV. This fiber was treated with concentrated nitric acid as shown in Table 1.

In order to compare the ease of introduction of acidic functional groups in the carbon fibers obtained in Example 1 and Comparative Examples 1 and 2, the carbon fibers were treated with 68% concentrated nitric acid for a predetermined time. The processing conditions are as shown in Table 1. The treated carbon fiber was washed with ion-exchanged water for about 1 hour and then dried in an oven at 120 ° C. for 30 minutes to evaluate the treated product. The oxygen concentration (O ₁ s / C ₁ s) by the internal X-ray electron spectroscopy (ESCA) of the evaluation was measured by using an X-ray photoelectron spectrometer, using AlKα1486.6eV as an excited X-ray, and an X-ray output of 10 kV, 20 mA, temperature 40 ° C. vacuum 10 ^{- 9} torr
It was measured in. From the obtained spectrum, C ₁ s
The relative integrated intensity of O ₁ s was calculated and used as an index of the amount of oxygen-containing functional groups on the carbon fiber surface.

The amount of acidic functional group by the titration method is the value obtained by the following method. That is, weigh about 5 g of a sample into a 300 ml Erlenmeyer flask with ground stopper, add 500 ml of water and 20 ml of 1/50 NaOH accurately with a whole pipette, add 30 ml of water to make 100 ml, and leave it for 20 minutes while shaking occasionally, and then put it on an ultrasonic shaker. Soak for 15 minutes, solution 50
Collect 1 ml in a Dharma flask with a whole pipette and
Titrate with NH Cl. For the titration, the amount of functional groups was determined from the titration curve using a Metrohm potentiometric titrator.

Next, the reactivity of the carbonaceous fiber introduced with the acidic group with the epoxy resin was tested. That is, 500 ml of a 10% (by weight) xylene solution of an epoxy resin (bisphenol A type) DER661 (manufactured by Dow Chemical Co., Ltd.) was heated to 150 ° C., and 5 g of the carbon fiber treated with the concentrated nitric acid was immersed in this. After the treatment for 1 hour, the fibers were separated by furnace, the unreacted epoxy resin was washed with acetone, and then dried under reduced pressure. The weight of the obtained fiber was precisely weighed, the weight increase (per 100 weight) was determined, and the amount of the epoxy resin bonded to the carbonaceous fiber was measured. The results are shown in Table 2.

Examples 2 to 5 Carbon fibers were produced under the same conditions as in Example 1 except that the organometallic compounds shown in Table 3 and the raw material hydrocarbons, carrier gas and cooling gas were used. Table 4 shows the physical properties of the obtained carbon fibers.

The same concentrated nitric acid treatment as in Example 1 was performed on the fibers obtained in Example 4 above. O ₁ s / C ₁ s of the obtained fiber
Was 1.85 and the acidic group by titration was 45 μmol / g.

The fiber of Example 5 was treated in air at 450 ° C. for 1 minute. The O ₁ s / C ₁ s of the obtained fiber was 0.63, and the acidic group by titration was 5.2 μmol / g.

The fibers of Example 2 above were treated with concentrated nitric acid at 120 ° C for 10
I went for a minute. The O ₁ s / C ₁ s of the obtained fiber was 0.54, and the acid group by titration was 4.9 μmol / g.

The fiber of Example 3 was treated with concentrated nitric acid at 120 ° C. for 20
I went for a minute. The titratable acidic group was 95 μmol / g.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing an example of an apparatus used for producing the carbonaceous fiber of the present invention. 1 ... Device body, 3 ... Nozzle, 5 ... Heater, 7 ...
… Reaction tower (reaction part), 9 …… Carrier gas, 11 …… Raw material liquid, 13 …… Cooling gas, 15 …… Cooling gas nozzle, 17…
… Bag filter (collection section), 19 …… Exhaust gas, 21 ……
Communication section.

Claims (1)

[Claims] 1. A fiber having a diameter of 0.01 to 4 μm and a fiber length /
Fiber diameter is 20 or more, crimp number is 1 or more, crimp degree is 10 to 50%,
The amount of acidic functional groups measured by the titration method is 0.5 to 200 μmol / g, and the oxygen concentration O ₁ s / C ₁ s measured by X-ray optical spectroscopy (ESCA) is 0.05.
A carbonaceous fiber having an acidic group formed by arranging graphite or a layer of carbon easily converted to graphite in a ring shape parallel to the longitudinal axis as described above.