JPS5936726A - Precursor pitch fiber for carbon fiber - Google Patents

Abstract

PURPOSE:The titled pitch fibers, having specific values of orientation angle, crystal size, layer spacing in X-ray diffraction and strength after calcination, and capable of preventing the enlargement of crystals in calcination and giving carbon fibers having a high strength and modulus by the calcination. CONSTITUTION:Precursor pitch fibers for carbon fibers, having 30-50Angstrom , preferably 35-45Angstrom , orientation angle measured by the X-ray diffraction, 25- 40Angstrom , preferably 27-37Angstrom , crystal size and 3.43-3.50Angstrom layer spacing measured by the X-ray diffraction and >=200kg/mm.<2> strength in calcination at 1,500 deg.C. Preferably, a pitch containing >=30wt% preferably 50-70wt%, quinoline-soluble component is used. Preferably, the fibers contain an optically isotropic component dispersed in the fiber axis direction in many streaky or fibrillar forms in an optically isotropic and quinoline soluble matrix of the fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel carbon fiber precursor pinch fiber. More specifically, it relates to pinch fibers that become high-strength, high-modulus carbon fibers by being subjected to infusibility-firing (carbonization) treatment.

Currently, carbon fibers mainly include polyacrylo, -
Trill (1'AN) PAN-based carbon fibers made from M fibers and pinch-based carbon fibers made from coal-based and petroleum-based pitches are produced. However, the mainstream of high-strength, high-modulus carbon fibers used primarily as reinforcing materials for resins in composite I materials is PAN-based fibers, and pinch-based fibers are only produced with a relatively low strength of less than 200 kg/ma. Not yet.

Recently, attempts have been made to produce higher performance fibers in such pinch-based carbon fibers, and the following methods of using pitch have been proposed so far in the busy manufacturing process of carbon fibers. 1, (a) A method using pitch obtained by hydrogen-treating or heat-treating a specific condensed polynomial aromatic compound (Japanese Patent Publication No. 45-2801
No. 3, Special Publication No. 49-11634).

(A method in which petroleum-based tar or pitch is subjected to a first heat treatment in the presence of a Lewis acid catalyst, and then the catalyst is removed and a second heat treatment is performed to use mesoface pitch. No. 7533) 1(c) A method of using mesoface pitch with a predetermined mesoface inclusion by heating the pitch under an inert gas flow or under reduced pressure (Japanese Unexamined Patent Application Publication No. 1983-1999)
No. 86717, JP-A-53-86718) 1(d)
Solvents (benzene, toluene,
A method of using neomesoface formed by treating it with heptane, etc.) and heating the insoluble part (Japanese Patent Laid-Open No. 54-1604
No. 27, JP-A-55-58287, JP-A-55-13
No. 0809).

However, even with these methods, it is not possible to obtain carbon fibers with advanced performance comparable to that of PAN-based carbon fibers, so to date, pitch-based carbon fibers have low performance, such as asbestos substitutes. The reality is that it is used in fields where it is acceptable.

In view of the current state of pitch-based carbon fibers as described above, the present inventors have conducted research to develop a method for producing carbon fibers with superior quality using pitches as raw materials. We have proposed a new method for manufacturing carbon fiber using a unique brimesoface pitch that converts into an optically anisotropic membrane during the infusibility/carbonization process (Patent Application 1983-
No. 117470).

As a result of further research based on this knowledge, the present inventors found that
In order to form high-performance carbon fibers, the process of melt-spinning and intervening the pinch, that is, the fine number of carbon fiber precursor pitch fibers, is required.
18 structure and the chemical properties of the pitch are important, and by controlling these, carbon #a fibers with excellent properties that cannot be expected from conventional pitch-based carbon fibers can be formed. This is the heading that led to the present invention.

That is, the carbon fiber precursor pinch fiber of the present invention has an orientation angle of 30 to 50X determined by X-ray diffraction, a crystal size of 25 to 40X, a layer spacing of 3.43 to 3.50X, and Moreover, the strength when fired at 1500℃ is 20
It is characterized by being 0 kg/- or more.

Conventionally, when obtaining high-strength, high-modulus fibers using mesophase pitch, it has been said that it is preferable that the precursor pitch fibers immediately after spinning be highly oriented. However, carbon fiber duri produced from highly oriented precursor pitch fibers,
The size of crystals oriented in the fiber axis direction (IJC) increases, and although high thermal conductivity and electrical conductivity as graphitization characteristics can be exhibited, the mechanical properties (strength and elongation) as a fiber are
However, it was insufficient compared to PAN-based carbon fiber. The reason for this is that excessively high orientation in pursuit of a graphitized structure results in fine inhomogeneity within the fibers.
It is thought that this causes vertical cracks in the fibers, leading to deterioration in strength.

As described above, the carbon fiber precursor pitch fiber of the present invention is
By adjusting the structural parameters determined by line diffraction to a suitable range (t1), it is possible to prevent the enlargement of crystals during sintering (carbonization) and to prevent the occurrence of cracks in the fiber axis direction. It is something.

In other words, highly oriented pinch fibers with an orientation angle (OA) of less than 30' tend to have a coarse radial structure in the crystals inside the fibers during the carbonization (sintering) stage, and cracks are less likely to occur. When the corner reaches 50', fine alignment during the carbonization (firing) stage is impossible, and high strength and high modulus are developed.

The crystal size, that is, the apparent microcrystalline thickness (LO) and the interlayer spacing (DOOM), are correlated with the orientation angle; when the orientation angle is small, the crystal size increases and the interlayer spacing decreases; To obtain −, the orientation angle (
OA), crystal size (LQ), and layer spacing (dqqt)
The balance of the four 47Q structural parameters is important, and a carbon fiber with good performance can be obtained if all of these parameters are within the following ranges.

・Orientation angle (OA)...30~soX, preferably steep,
35-45A ・Crystal size (Lc)...25-40X, preferably 27-37A ・Layer spacing (DOO...3.43-3.5OA) Orientation angle (OA), crystal size (Lc) ) and interlayer spacing (doOs) are values measured by wide-angle X-ray diffraction, a method commonly used in the state of fibers.

That is, a bundle of fibers is attached to the X-ray beam perpendicularly to 1α, the azimuth angle 2θ is skimmed from 0 to 90°, and the At value of the intensity distribution in the (002) band (approximately 26°) is calculated. From the full width (half width) B1 at the 1/2 position and the azimuth 2θ, Lc, d, and oot are calculated using the following formulas (however, K
= 0.9, b = 0.0017rPLd, λ=
1.5418A) λ 2 sin θ Also, the fiber bundle is x7! at the azimuth position where the i-fluorescence distribution of the (002) band has the maximum value. By rotating the beam by 180° in the hand plane, the intensity distribution of the (002) band is taken, and half 1i[1
Let i width be the orientation angle.

The carbon fiber precursor pitch fiber of the present invention preferably contains at least 1% or more, particularly 50 to 70% by weight of a quinoline-soluble component. Quinoline soluble component is 301
When the carbon fiber structure is less than 1, in other words, when the quinoline-soluble component exceeds 70% by weight and 9%, the resulting carbon fiber structure tends to have a radial shape.

In particular, the quinoline soluble component occupies 50 to 70 parts by weight, and the optically isotropic quinone H (major of the soluble component). In the case of a 47-Y structure in which carbon is dispersed in the form of fine sushi or fibrils, crystals are formed in the carbonization (firing) process with the optically anisotropic component dispersed in fine nil as the core. Ideal crystal size and arrangement are achieved in the fiber.

It is important that this optically anisotropic component does not exist in a spherulite state but is oriented in the direction of the fiber axis, and the width of the anisotropic region extending in the form of stripes or fibrils is 1μ. The length is 105 or more (usually 10-10
0μ).

FIG. 1 is a partially cutaway enlarged view of a fiber schematically showing this preferred embodiment. In the figure, l□ is a matrix portion that is optically isotropic and consists of a quinoline-soluble component, and is a dark field under crossed Nicols. 2 is an optically anisotropic component that is dispersed in a fine sushi-like or fibril-like shape, and is a portion that appears to shine under crossed Nicols.

M) The optically isotropic and quinoline-soluble component constituting the IJ tux moiety is preferably a pinch which the present inventors named "brimethoface" earlier, and in particular, a number-average molecule. Presentation.

700-170G (especially 1000-1500) is preferable. In addition, pinch +i constituting the fiber, specific gravity at 20°C 1.29 to 1.40 (particularly 1.30 to 1.3
5) A pitch mainly composed of polynomial condensation compounds having a degree of aromatization of 0.45 to 0.9 is optimal.

Moreover, this pinch is preferably one in which Hlo is within a very limited range of 0.50 to 0.65.

Furthermore, the above-mentioned quinoline-soluble component has a chemical shift of 5 to 7 on the basis of tetramethylsilane (TMS) with respect to all detected hydrogen excluding the solvent in 'H-NMR. The proportion of ppm water 75HA is 4.5~xOn, and 3
The proportion of ~4 ppm hydrogen HB is 2.5-7.5%
I prefer one that is 17.

The pinch that satisfies these threads is t with 4 to 6 condensed rings.
Two to ten t'l structural units are connected via side chains, the aromatic nucleus of each structural unit is partially hydrogenated, and the planar structure of the molecule is distorted. Therefore, by melt-spinning the pinch composition, it is easy to form the special microstructure as described above.

In addition, here, several thousand equivalent molecular weight, degree of aromatization, 'H-
Measurement of NMR, u/a is performed as follows, (1)
0 constant Ov, p using vpo with number average molecular weight pyridine as a solvent.
Knauner D as a vapor pressure osmometer
Using ampfdruck Ostometer,
Pyridine was used as the solvent and benzyl was used as the standard vJ shell.

(2) Aromatization degree Calculated from the IR measured by the KBr tablet method using the following formula.

Aromatic BL=3050cm-'Intensity/(aoso,
rm-' Strong + 2925 cm-' Strong 1 Note that the R-measurement device used was the R-27G model manufactured by Shimadzu Corporation.

(3) 'H-NMR A JEOL ps-too type spectrometer was used as the measuring device, and the chemical shift was expressed as a δ value using TMS as an internal standard. NMR spectra were measured using vertical pyridine as a solvent.

(4) Uxs/c-(H analysis value/1)/(O analysis value/12) created according to the following formula from elemental analysis measured according to Hlo 515M-8813 According to the research of the present inventors, this condition The pitch that satisfies
The nucleus of the polycyclic condensed compound is partially hydrogenated, and the planarity of the molecule is distorted, so it has sufficient force fluidity despite its relatively large molecular weight, and is soluble in quinoline. The compatibility between the components and insoluble components is also good.

This pitch is partially hydrogenated during the infusibility process, and is rapidly oxidized, making it possible to become infusible in a short time.Furthermore, hydrogen is removed during the infusibility-explosion process, which improves the planarity of the molecules. The carbon fiber precursor pitch fiber of the present invention, which is composed of one or more of the above-mentioned materials that can be recovered and mesophased to produce good crystals, can be made into a high-strength, high-modulus fiber by being melted and fired by a known method. carbon fiber. The strength of the product fired at 1500℃ is at least 200K (/aJ, modulus is 10 ton/- or more, and the strength after firing at 1500℃ is 250h/- or more, modulus 15 tr). The carbon fiber precursor pinch fiber according to the present invention having a fiber length of n or more is produced, for example, by the following method.

[Pinch set for spinning, manufacturing of products]

Raw material pitches include coal tar, coal tar pitch, coal-based oils such as coal liquefied products, normal pressure residual oil of petroleum, vacuum distillation residual oil, and tar, pitch, and oil sand produced by heat treatment of these residual oils. Although petroleum-based heavy oils such as , pitumen, and the like can be used, coal tar pitch is preferred because it facilitates the preparation of the pinch composition of the present invention.

The pinch composition of the present invention includes a first stage treatment in which the raw material pinch is heated in a specific hydrogenation solvent after being purified, and a second stage in which the raw material pinch is heated to a disease temperature after or while removing the solvent. It is left behind by applying processing.

Tetrahydroquinoline (hereinafter abbreviated as THQ) is optimal as the hydrogenation solvent used in the first stage treatment, but a mixture of quinoline and TI (Q) may also be used.
In addition, in the presence of a catalyst (cobalt-molybdenum type, iron oxide type), it is also possible to i+B. TI as a hydrogenation solvent (when Q is m-, add JHQ, 130 to 10011 parts by weight per 100 parts by weight of raw material pitch, and add 300 to
Heat at 500°C, preferably 340-450°C, for 10-60 minutes. The product thus treated is the following pl)
Subjected to two-stage processing.

In the 142-stage process, the THQ processing pinch is performed under reduced pressure, for example, at a pressure of 50 to 11 g or less, at 450°C or higher, preferably at 4
Hold at 50-550°C for 5-60 minutes. In this case, instead of such a vacuum treatment, THQ may be removed and then held at 450 to 550°C for 5 to 60 minutes under normal pressure. −℃
After raising the temperature to a higher temperature, it may be lowered to 400i-430°C and held at this temperature for 15L-180 minutes.

In the two-stage treatment, a preferable spinning pitch composition can be obtained by appropriately selecting treatment conditions within the above range depending on the composition and properties of the raw material pitch.

The melt-spinning property is very good. [Production of pitch fiber kasuri] Melt-spinning of the pitch composition can be performed by a method known per se. For example, if the pitch composition of the present invention has a pore size of 0.
From a spinneret with 1 to 0.8 holes, the softening point is 50 to
The filament extruded at a temperature higher than 100°C and discharged from the spinneret is spun (take-up) at a speed of 300 to 15% under quenching conditions.
The pinch fiber of the present invention can be easily obtained by winding the fiber in 7 minutes.

The pitch fibers of the present invention are then heated to K O,I in the presence of oxygen.
Heat to 250 to 350°C at a heating rate of s to 3°C/min, hold for 5 to 30 minutes, and infusible with K.
This is further heated in an inert gas to 2-b 1000-150.0°C, and then heated to this temperature for 10-150.0°C.
Carbonization (firing) treatment is performed by maintaining the temperature for 30 minutes.

The pitch fiber of the present invention can be obtained by the carbonization (calcination) treatment.
At this point, the carbon fiber becomes a complete membrane, fully oriented, and has a dense structure that does not contain large domains.

The obtained carbon P# fiber has a high strength of 2ooKf/- or more and a modulus of 10'tOn/- or more, and in a particularly preferred embodiment, a strength of zsogf/- or more and a modulus of 15
ton/- or more, resulting in extremely excellent performance.

Next, the present invention will be explained in further detail by Examples and Comparative Examples.
Explain.

In addition, the fiber diameter (thread diameter), tensile strength, elongation, and modulus of the carbon fibers in each example were measured according to the "J-Ko SR7601F Carbon Fiber Test Method".

Note that the fiber diameter was measured using a helium-neon laser.

In addition, the viscosity was measured using a Koka formula 7 rJ-tester, and the apparent viscosity was measured from the amount of drop under the following conditions: Cylinder cross-sectional area: tc, 4 nozzles'''/D = OJ rrrm/O- Load between 3: 50 to heavy L (cm)...Nozzle land length P (~tVty4)...Load Q (c14/5eC)...Discharge amount and fractional state of the optically anisotropic part is The pitch fibers were fixed in an epoxy resin matrix, the side surfaces of the fibers were cut out, and the side surfaces were observed using a polarizing microscope.

The content of quinoline-soluble components in NK and pitch fibers was measured according to JIS K-2425.

Example 1 City JI12 coal tar medium pitch 134f and THQ4o
2f′! ! ``RUB-3 equipped with electromagnetic induction rotating stirring station
After putting it into a 16Jqlt autoclave and replacing it with nitrogen, the inner and outer parts are OKq/ty! l (), and after sealing, raise the temperature to 430°C while stirring, and after reaching 430°C,
The mixture was maintained for an additional 15 minutes, then cooled to room temperature, and the contents were filtered using a G4 glass filter to remove insoluble materials. P liquid final 29
The mixture was distilled under reduced pressure to 0° C. r 10 rrrrnlIg abs to remove volatile components mainly consisting of unreacted T)IQ and quinoline produced by the reaction, to obtain a carbon fiber raw material pinch composition. 11g of the raw material pitch composition at 465°C
After heat treatment in an N% atmosphere for 15 minutes, pitch for carbon fiber spinning was prepared.

The specific gravity (20° C.) of the obtained pinch was 1,323°, the quinoline soluble portion was 40.3 weight 11A·%, the toluene insoluble portion was 84.9 weight %, and the viscosity at 320° C. was 1430 voids. The number average molecule 61 of the quinoline soluble component is 980.
Pressure (20°C) r, J: 1.3o6, and pinch aromatization degree i13.

The spinning pin was filtered with a filter of 1600 mθeh and L/D=0,110,1 (T/M) number of holes (H)
= 1 [j using an extruded cylinder equipped with gold, spinning temperature 360°C, discharge speed 8.4 m/yp;
*The carbon fiber precursor pinch fibers were obtained by spinning into air at room temperature at a winding speed of 60 .mu.m for 7 minutes. The orientation angle of the obtained pitch fibers was 36.1°, the crystal size (apparent, microcrystal height Lc) was 34.5 A, and the interlayer spacing (do
ot) was 3.47 A. The same pitch fibers were buried in an epoxy matrix and the sides were cut out and polarized light microscopy @
Upon observation, it was confirmed that the optically anisotropic component was dispersed in a fine sushi-like shape in the fiber axis direction. (See Figure 1) The same carbon fiber precursor pitch fiber was heat-treated in an infusibility furnace under an air atmosphere at a temperature increase rate of 2°C/min from 200°C to 300°C, and then heated at 300°C for 3 ( ) to make it infusible. Then, in the firing furnace, N! The material was heated in an atmosphere from 200° C. to 1500° C. at a rate of temperature increase of 10° C./min, followed by heat treatment at 1500° C. for 15 minutes to carbonize it.

The diameter of the obtained carbon PIi fiber is 1018 μ9, and the strength is 24
s K4 /ear elongation 1.4%, modulus is 1
It was 7.5 tons/-.

Examples 2-5 Commercially available coal tar pitch 354 f! THQ10
53F, SUS-3 with magnetic induction rotary stirring device
16? After the autoclave was charged into an i3t autoclave and the autoclave was sufficiently replaced with nitrogen, the internal pressure was set to Oh/ctla, and after the autoclave was sealed, the temperature was raised to 450°C with stirring, and after the autoclave was allowed to rise to 450°C, it was maintained for an additional 15 minutes.

Thereafter, the contents were cooled to room temperature and subjected to PiPA using a 04 glass filter to remove insoluble materials.
Distillation was carried out under reduced pressure at 0° C. and 10 Torr to remove volatile components mainly consisting of unreacted THQ and quinoline produced by the reaction, to obtain a carbon fiber raw material pitch composition.

The raw material pinch composition was heated at 465° C. and io torr.

A pinch for carbon fiber spinning was prepared by heat treatment in NN Goss air for 15 minutes.

The specific gravity (at 20°C) of the obtained pitch is 1,332°; the quinoline-soluble portion is 57.6 weight folds, and the toluene-insoluble portion is 89.0.
The viscosity in weight percent at 320C was 245° voids.

The number average molecular weight of the quinoline soluble component is 983 and the specific gravity is 1.3.
11, and the degree of aromatization of the pitch was 0.54.

The spinning pitch was changed to a 1600 mesh filter and L
/D-0,1/ 0.1 (17 hours), spinning temperature 380 using an extruded cylinder equipped with a nozzle of H=1.
℃, constant discharge speed s, 4 m/min, and changing the winding speed, spinning was carried out at room temperature in air to obtain various carbon fiber precursor pitch fibers. Table 1 shows the X-ray 41 formation parameters of each precursor pitch fiber.

The same carbon fiber precursor pitch fiber was heated from 200° C. to 300° C. at a temperature increase rate of 2° C./min in an air atmosphere in an air atmosphere without tension using an infusibility furnace, and then heat-treated at 300° C. for 30 minutes.

Next, in the firing furnace, N! Under atmosphere, from 200℃ to 1500℃
Heating at a heating rate of 15°C/min in a ℃ holder, and then heating to 1500°C.
Heat treatment was performed for 15 minutes.

The physical properties of the obtained carbon fibers are shown in Table 2.

Table 2 Physical properties of carbon fiber Examples 6 to 9 The same spinning bits used in Example 2 were used with a 1600 mesh filter and L/D = 0.370,3 (17''
/m/m) pH = 1 caps fx, t fc
Spinning temperature 380℃ using extrusion cylinder
Melt spinning was carried out by fixing the winding speed to 600% and 7 minutes and changing the dot ratio.

The XS structural parameters of the obtained precursor pitch fibers are shown in Table 3.

Table 3 Spinning conditions and physical properties of pinch fibers Each carbon fiber precursor pitch fiber was heated from 200°C to 300°C under no tension in an air atmosphere using an infusibility furnace at a heating rate of 2°C/min, and then heated to 300°C. Heat treatment was performed for 30 minutes.

Then, in a firing furnace, Nt'11. 15 from 200℃ under ambient atmosphere
Heating at a heating rate of 15°C/min to 00°C, followed by heating at 150°C.
Heat treatment was performed at 0°C for 15 minutes.

The physical properties of the obtained carbon fibers are shown in Table 4. Table 4 Physical Properties Comparative Example 1 of Carbon Fibers The same spinning pitch as in Example 1 was used with a filter of 1600 mesh and L / D = 0, 1 / 0, 1
Melt spinning was carried out using an extrusion type cylinder equipped with a nozzle having (myl'my+) + number of holes - 1 at a spinning temperature of 330° C., a discharge rate of 8.4 m/min, and a winding speed of a o on/min. At this time, a spinning tube with a length of 2 Qcm was provided directly below the spinneret, and the temperature inside the tube was maintained at 300°C.

The orientation angle of the obtained carbon fiber precursor pitch fiber was 27.8
°, crystal size (Lc) is 42. lλ, no interval (do
es) tj, 3.45X. This pitch N
It fibers were heated under no tension under air in a chemical furnace for 2 hours.
Temperature increase rate from 00°C to 300°C/min, then 30°C
Heat treatment was performed at 0°C for 30 minutes. Next, N in the firing furnace!
Under atmosphere, heating rate 10℃ from 200℃ to 1500℃
/min, followed by heat treatment at 1500°C for 15 minutes. When the fractured surface of the obtained carbon fiber was observed using a scanning electron microscope, the crystal alignment was radial and a second re-crank had occurred, and the weaving properties were 81.3h/IIIJ! Elongation 0.7
6%, and the modulus was 10° eton/-.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway sectional view showing a preferred embodiment of the carbon fiber precursor pitch fiber of the present invention, and 1 in the figure is quinoline-soluble and optically isotropic fl (7) -q )
The IJ tux part and the fibril part with double-digit optical anisotropy are shown. Designated agent: Director of Optical Industrial Technology Testing Institute Hayashi Hori, 1
Thatch 1 Figure-136-

Claims (1)

[Claims] 1. The orientation angle determined by X-ray diffraction is 30 to 50 degrees, the crystal size is 25 to 40 degrees, and the interlayer spacing is 3.43 degrees.
-3.50[chi], and has a strength of 20ob/- or more when fired at 1500C. 2. Claim V consisting of a pitch containing 30% by weight or more of a quinoline soluble component! A? i The carbon fiber precursor pitch fiber according to item 1. 3. 50 to 7.0 weight of quinoline soluble component, 'A2
Il consisting of a pinch in %A2? #'F mW range The carbon fiber precursor pinch fiber according to item 2. 4. The optically anisotropic component is dispersed in the optically isotropic and quinoline-soluble matrix in the form of a large number of sushi-like or folded fibrils extending in the fiber axis direction. Carbon fiber precursor pitch fiber according to item 3.