JPH06143275A - Pitch carbon fiber prepreg - Google Patents

Abstract

PURPOSE:To provide an unidirectional prepreg of pitch high-elastic carbon fiber of low weight per unit area and of almost no openings. CONSTITUTION:An unidirectional prepreg is composed of arranged fiber bundles and provided with 15-75g/m<2> fiber weight per unit area impregnated with thermosetting resin, and its fiber bundles are continuous fiber of 4-8mum average fiber diameter and composed of pitch carbon fiber bundles constituted of no-doubling yarns. The prepreg is an unidirectional prepreg of low weight per unit area composed of high-elastic fine diameter carbon fiber, and almost no openings are found, and its thickness is uniform, and the prepreg is suitable for improving the rigidity or lessening the weight of a tubular composite molded product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved unidirectional prepreg used for obtaining various moldings reinforced with carbon fiber, and more particularly to a low basis weight unidirectional prepreg of pitch-based carbon fiber. It is a thing.

[0002]

2. Description of the Related Art In recent years, prepregs obtained by impregnating reinforcing fibers such as carbon fibers, glass fibers and aramid fibers with a matrix resin typified by an epoxy resin have been utilized for their excellent mechanical properties, such as fishing rods and golf shafts. It has been widely used in fields such as sports and leisure, industrial fields such as rolls and rotating bodies, and aerospace fields such as primary and secondary structural materials of aircraft. Particularly in the sports and leisure field, carbon fiber prepregs occupy most of the high-performance reinforcing fibers, and in recent years, with the aim of achieving even higher functionality, lower resin content of prepregs and use of highly elastic fibers have been adopted. Being tried. For example, in the use of a fishing rod, in order to obtain the crushing strength of the fishing rod, instead of the conventionally used ultrathin glass scrim cloth, an ultrathin unidirectional carbon fiber prepreg that is laminated orthogonally is used,
A product has been developed aiming at improving the crushing strength and reducing the weight. With the demand for higher functionality of such molded products, the need for prepregs with a low basis weight using high-elasticity carbon fibers is increasing.

In recent years, as carbon fibers having an elastic modulus of more than 600 GPa, pitch-based carbon fibers made of mesophase pitch, which is easy to have a high elastic modulus, have been mainly manufactured, and the application of the prepreg has been developed. Has been done. At that time, as the fiber becomes more elastic, the fiber yarn becomes more rigid, and development of a prepreg having good molding workability is required. The conventional pitch-based high elasticity carbon fiber has an average fiber diameter of 8
When the unidirectional prepreg using the fiber is wound around the tubular body in the angle direction and used, the fiber breaks when the winding end is raised or rolling, and the strength and rigidity of the molded product are reduced. . Further, in order to produce a low fiber basis weight prepreg of 75 g / m ² or less using pitch-based high elastic carbon fibers, a method of producing a prepreg using a carbon fiber bundle having a small number of filaments and a low fineness is used. Generally, the lower the number of filaments in a fiber bundle, the higher the price per unit weight thereof, so that the prepreg having a low basis weight becomes more expensive.

On the other hand, a fiber bundle obtained by combining a plurality of fiber bundles is
Easy to separate into the original fiber bundle unit, poor handling,
In addition, the fiber alignment is poor, and the resulting unidirectional prepreg has the drawbacks of causing fiber meandering and opening. by the way,
There is a method of twisting in order to improve the handling property, but the prepreg is inferior in the opening property and an opening occurs, so that a satisfactory unidirectional prepreg cannot be obtained. Especially 90 fishing rods
The slit tape used for reinforcement in the ° direction is required to have a high-precision tape width and good unwinding property when taping, so the unidirectional prepreg, which is the raw material, has no openings and no thickness unevenness. It needs to be more uniform.

A technique for widening a carbon fiber bundle to obtain a unidirectional prepreg is disclosed in JP-A-56-43,435.
JP-A-57-77,432 and JP-A-60
-9,961 and JP-A-1-282,362. In these methods, a method of previously opening the fiber bundle by mechanical contacting means, or a method of removing the sizing agent of the fiber bundle by opening the fiber bundle, and the like are adopted. According to such a method, in the pitch-based high elasticity carbon fiber bundle, the pitch-based high elasticity with a low basis weight that requires a wider amount per fiber bundle is required due to its fiber characteristics of higher elasticity and smaller elongation than general carbon fibers. As for the unidirectional prepreg of carbon fiber, only those with creases or fluff were obtained.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a unidirectional prepreg of pitch-based highly elastic carbon fiber having a low basis weight, which does not have the above-mentioned drawbacks and has almost no openings.

[0007]

SUMMARY OF THE INVENTION According to the present invention, in a unidirectional prepreg having a basis weight of 15 to 75 g / m ² in which a fiber bundle is impregnated with a thermosetting resin, the fiber bundle has an average fiber diameter of 4 to
A unidirectional prepreg, which is a pitch-based carbon fiber bundle composed of 8 μm continuous fibers and non-bonded yarns.

The number of filaments constituting the above fiber bundle is 2,000 to 12,000, the filament has a tensile strength of 3.0 GPa or more and a tensile elastic modulus of 600.
It is preferably at least GPa. Furthermore, the bending strength B of the fiber bundle is expressed by the following formula B ≧ (2.875 × 10 ⁻⁴ TM-0.17) ⁻¹ [where B: bending strength (MPa), TM: tensile elastic modulus (GPa)]. It is desirable to be satisfied.

The present invention will be described in detail below. First, the unidirectional prepreg referred to in the present invention is parallel to each other,
In addition, a large number of fiber bundles aligned in a sheet shape are impregnated with a so-called B-stage thermosetting resin that stays in a thermoplastic state for a longer time than usual, and one fiber bundle has an initial width. 2 to 10 times wider.

In the present invention, the average fiber diameter, tensile strength, tensile elastic modulus and flexural strength are the values determined as follows. (Average fiber) The average fiber diameter D of the carbon fiber is the following formula: D = √ (4W / Nρπ) [where W: weight of fiber bundle per unit length, N: number of filaments (number of single yarns), ρ: Fiber density]. (Tensile Strength and Tensile Elastic Modulus of Filament) The tensile strength of the filament was determined in accordance with the resin-impregnated strand test method defined in JIS R7601. The tensile modulus was determined by the direct reading method in the range of 10 to 30% of the breaking load. (Flexural strength) Take out a carbon fiber bundle of 1 m in length and
As shown in the figure, both ends of the carbon fiber bundle 17 are aligned, a wire 19 having a diameter of 1 mm is hooked on the loop portion of the fiber bundle on the loop where the tabs 18 are attached with an adhesive, and the wire or tab is 0.2 m / min. A value obtained by dividing the load measured by the load meter 20 by the cross-sectional area of one carbon fiber bundle when the loop was pulled at a speed and the loop broke at the wire portion was defined as the bending strength.

The pitch-based carbon fiber bundle used for carrying out the present invention has an average fiber diameter of 4 to 8 μm and a total fiber length of 2,000.
˜12,000 continuous fibers are composed of non-bonded yarns. In a unidirectional prepreg using a fiber bundle having an average fiber diameter of more than 8 μm and a modulus of elasticity exceeding 600 GPa, if it is used by winding it around a tubular body in the angle direction, the winding end portion rises at the time of molding, which lowers the molding workability, and eventually the fiber. This causes a problem of breaking the strength and rigidity of the molded product. On the other hand, if the diameter is less than 4 μm, it is difficult to manufacture continuous fibers of pitch-based carbon fibers, and in view of their productivity, they are extremely expensive and impractical. The number of filaments of the fiber bundle needs to be 2,000 or more in order to improve the productivity when producing the fiber bundle and the prepreg. When the number of filaments is less than 2,000, the fineness (unit length of the carbon fiber bundle) The weight of the fiber bundle per hit is small and the productivity is impaired. Further, when the number of filaments exceeds 12,000, the fiber areal weight used for reinforcement of the composite molded product is 75 g / m ²
The following unidirectional prepreg has many openings and is not suitable for the present invention.

The physical properties of the carbon fiber bundle used are as follows:
In order to improve the functionality of the molded product, the tensile elastic modulus is 600G
It is Pa or more, and the tensile strength is 3.0 GPa or more, preferably 3.5 GPa or more, and more preferably 4.0 GPa or more. If the tensile strength is less than 3.0 GPa, the elongation of the fiber is extremely small, and the use as a high-performance material is extremely limited. The flexural strength varies greatly depending on the elastic modulus, but for example, when the elastic modulus is 600 GPa, 400 M
Less than Pa, less than 32 MPa when elastic modulus is 700 GPa,
If the elastic modulus is less than 17 MPa when the elastic modulus is 800 GPa, the handling of the fiber bundle is significantly impaired, the fiber bundle is broken during the production of the prepreg, and fluff is generated, resulting in a prepreg having a poor appearance.

The fiber bundle used in the present invention is characterized by being non-bonded yarn. This is in the production of pitch-based carbon fibers, after once obtaining a pitch fiber bundle, in the state of pitch fibers,
Alternatively, if a prepreg is manufactured using a fiber bundle that has been combined after infusibilization or after carbonization, it will be divided into fiber bundle units before combining when the yarn is drawn from the creel stand to the impregnator, and workability will be improved. Is significantly reduced. Further, the combined fiber bundle contains twists and has a poor spreadability. Particularly, in the case of unidirectional prepreg having a low basis weight, fibers can meander and open, and a satisfactory prepreg cannot be obtained. Therefore, the fiber bundle used in the present invention is a precursor pitch fiber without being combined,
The number of filaments is 2,000 to 12,000 at the spinning stage.
Must be manufactured in a book.

Next, a manufacturing method for obtaining the unidirectional prepreg according to the present invention will be described below. First, an example of a production method for obtaining a pitch-based highly elastic carbon fiber bundle used in the present invention will be described. FIG. 1 is a sectional view of a melt spinning nozzle, in which the melt spinning nozzle 12 includes a nozzle plate 2.
A plurality of capillaries 9 are arranged on the nozzle plate 2. The capillaries 9 are arranged concentrically in 3 to 20 rows. The outermost radius of the capillary positions arranged concentrically is preferably 50 to 250 mm. If the number of rows of capillaries is less than 3, it is difficult to arrange 1,000 or more capillaries in a single nozzle plate, or the nozzle plate becomes very large. On the other hand, if the number of rows exceeds 20, the atmospheric temperature in the central portion of the rows becomes higher than the atmospheric temperature in the outer or inner rows, which makes stable spinning difficult.

Further, as shown in FIG. 2 and FIGS. 3 to 8, the location of the capillaries must be divided into two or more blocks. The distance between the capillaries is preferably 1 to 6 mm, more preferably 2 to 3
mm is suitable. When the blocks are divided into fan shapes (FIGS. 3 to 6), it is preferable that the blocks be spaced at an angle of 10 to 30 ° or that the narrowest portion be spaced at least 10 mm. The diameter of the capillary is 50
μm to 110 μm, preferably 70 μm to 100 μm. If the capillary diameter exceeds 110 μm, the spinning of fine pitch fibers becomes unstable, and if it is less than 50 μm, the processing of the capillary becomes very difficult and the maintenance of the nozzle is complicated, which is not preferable. If the location where the capillaries are arranged becomes a continuous concentric circle without being divided, the introduction of the atmospheric gas into the center of the nozzle becomes insufficient, and the atmosphere in the center of the nozzle becomes high temperature, making it difficult to continue stable spinning.

Also, a height of 20 mm at the bottom of the nozzle plate
Above, preferably a cylindrical protrusion 3 of 30 to 150 mm
Is essential. The cylindrical protrusion 3 plays a role of controlling the air flow flowing between the blocks in which the capillaries are arranged and the gap between the blocks. When the protrusion 3 is not present or when the height is less than 20 mm, the cylindrical protrusion 3 flows through the gap between the blocks. The airflow collides with the central part of the nozzle, and the airflow is extremely disturbed in the central part of the nozzle, which makes it extremely difficult to stabilize spinning near the central part of the nozzle (near the capillary located near the innermost circumference of the nozzle). By dividing the arrangement of the columnar protrusions and capillaries into blocks, it is possible to bring about both the effects of cooling the inner peripheral portion of the nozzle and stabilizing spinning by controlling the accompanying flow. As shown in FIGS. 9 to 12, the cylindrical protrusion 3 is not limited to a cylinder, and even if one end of the cylinder is reduced or the corners are rounded, a significant difference in effect is not obtained. Not seen, Figure 9
The height H shown in to 12 is 20 mm or more, preferably 30
It may be up to 150 mm.

If the above requirements are satisfied, the number of nozzles is 1,000 or more, preferably 2,000 to 6,0.
For the first time, stable spinning is possible even with a nozzle having a number of capillaries, which is considered to be completely impossible with a conventional spinning device, such as 00 capillary. However, when the pitch fiber is melt-spun, the nozzle plate surface is significantly soiled by vapor or decomposed products generated from the pitch during melt-spinning. For this reason, the duration of stable spinning must be limited due to contamination of the nozzle plate. As a countermeasure against this, it is effective to bring the accompanying flow generated during spinning close to the vicinity of the nozzle plate, the replacement of the atmosphere immediately below the nozzle plate becomes good, and the contamination of the nozzle can be significantly reduced. Specifically, a circumferential slit is provided on the outer periphery of the capillary arrangement portion and the lower portion of the nozzle plate, and atmospheric gas is sucked from this slit, whereby the accompanying flow generated by spinning flows just below the nozzle plate.

At this time, the slit is 20 mm or more from the outermost peripheral portion of the capillary arrangement portion, preferably 50 to 200 mm.
And the width of the slit is 5 to 30 mm.
Is preferred. When the outermost radius of the concentric circles of the capillary positions exceeds 100 mm, it becomes difficult to perform uniform suction over the entire slit at one suction position. Therefore, if necessary, two or more, preferably 4 to 8 Stable spinning can be performed by dividing the portion into parts and controlling the suction amount to be uniform. As shown in FIG. 1, the flow of the airflow at this time is drawn toward the nozzle plate 2 side as a whole by the suction of the suction slit 4, and the starting position of the accompanying flow flows directly below the nozzle plate. Further, the air flow passing through the gaps between the blocks in which the capillaries are arranged is given a downward flow by the columnar projections 3, and the air flow stably flows without being disturbed, which enables stable spinning.

The raw materials for the pitch for spinning used in the carbon fiber bundle of the present invention are coal-based pitch such as coal tar and coal tar pitch, coal liquefied pitch, ethylene tar pitch,
It includes various pitches such as petroleum pitch such as decant oil pitch obtained from fluidized catalytic cracking residual oil, or synthetic pitch made from naphthalene or the like using a catalyst and the like. The mesophase pitch used for the carbon fiber bundle of the present invention is the above-mentioned pitch in which the mesophase is generated by a known method. It is desirable that the mesophase pitch has a high orientation of pitch fibers when spun. Therefore, the mesophase content is desirably 40% or more, more preferably 70% or more, and further preferably 90% or more. Further, the mesophase pitch has a softening point of 200 to 400 ° C., more preferably 250 to 350.
Good at ℃. Prior to spinning, it is necessary to remove foreign matter from the pitch by a filter having an absolute filtration accuracy of 3 μm or less, or a filtration method capable of obtaining a filtration accuracy equal to or higher than this filter, prior to spinning. If solid foreign matter of 3 μm or more exists in the pitch, yarn breakage will occur frequently.

The conditions for spinning the above mesophase pitch with the above spinning nozzle include, for example, a viscosity of 200 to 900.
At a temperature that indicates a poise, the pressure is 10 to 100 kg / cm ² ·
While extruding at about G, 100-1,000 m / min
The pitch fiber having a predetermined fiber diameter can be obtained by drawing at a take-up speed of preferably 300 to 600 m / min. At this time, a pitch fiber may be obtained by using a spinning nozzle having 2,000 or more capillaries alone, or two or more such spinning nozzles, and a plurality of spinning nozzles of the present invention arranged as shown in FIG. In the spinning device described above, the pitch fiber extruded from the spinning nozzle may be drawn by a single roll to obtain a multifilament pitch fiber. The number of spinning nozzles lined up at this time is preferably 6 or less. If the number is larger than this, adjustment between the nozzles becomes complicated, and the spacing between the spinning nozzles is widened so that the spinning can be performed with a single roll. Becomes difficult, and it becomes difficult to produce a multifilament carbon fiber with good yarn alignment.

With the above-described spinning nozzle, pitch fibers for a fine carbon fiber bundle having a number of filaments of 2,000 or more can be obtained. The fiber diameter of the pitch fiber is infusibilized, carbonized, and graphitized to cause shrinkage of the fiber diameter, so the fiber diameter of the pitch fiber may be determined in consideration of this amount. By spinning into a diameter of 5 to 11 μm, a fine carbon fiber having a fiber diameter of 4 to 8 μm can be obtained. Next, the obtained pitch fiber is infusibilized, carbonized, graphitized, and surface-treated by a conventionally known method to have a fiber diameter of 4 to 8 μm and a number of filaments of 2,000 to
A pitch-based carbon fiber bundle composed of 12,000 thin fibers can be obtained.

The unidirectional prepreg using the pitch-based carbon fiber bundle thus obtained can be manufactured by a known hot-melt type prepreg manufacturing apparatus. An example of the manufacturing method will be described below. FIG. 15 is a schematic view of a prepreg manufacturing apparatus suitable for manufacturing the one-way prepreg of the present invention. The fiber bundles 23 unwound from the bobbins 22 set up on the creel stand 21 are drawn and aligned through the combs 24 arranged at equal intervals.
Aligned while being opened by a bar 25 with a satin-finished surface heated to ℃, preferably 60 to 120 ℃. The number of fiber bundles used here is determined by the desired fiber areal weight, prepreg width, and fineness of the fiber bundle. A coated paper 26 in which a predetermined amount of a thermosetting resin is applied to a release paper is sent from above and below to a nip roll 27 so as to be superposed thereon, and a fiber bundle that has been aligned is sent in between. The fiber bundle passes through nip rolls 27, 28 and 29 heated to 80 to 150 ° C. to give a linear pressure of 3 to 15 kg per cm to widen the fiber bundle and transfer the resin.
After impregnating and cooling, peel off the upper release paper 32,
A cover film 33 made of a thermoplastic resin such as polyethylene is adhered and wound on a paper tube by a winder 36, so that a fiber basis weight of 15 to 75 g / m ² unidirectional prepreg 3
5 can be obtained.

The unidirectional prepreg of the present invention is uniform in thickness and has no openings in the low basis weight area where a wider width per fiber bundle is required, as compared with a prepreg made from a combined fiber bundle. It has been found that the appearance of fluff and fiber meandering is also excellent. This is because the fiber bundle used is a non-bonded yarn, so the twisting and fiber entanglement of the fiber bundle are less than in the composite fiber bundle, and the spread width of the fiber bundle is extremely uniform in the length direction. Guessed.

The thermosetting resin used in the present invention is mainly composed of a usual resin used as a matrix resin of a fiber reinforced composite material, for example, an epoxy resin, a phenol resin, a bismaleide resin, etc. Epoxy resins are preferred because they provide particularly excellent mechanical properties and have good moldability. As the curing agent, known ones compatible with each matrix resin can be used. The resin content is preferably 20 to 50 wt%, more preferably 30 to 45 wt% from the viewpoint of tack retention and physical properties. INDUSTRIAL APPLICABILITY The unidirectional prepreg of the present invention is a low-basis weight prepreg composed of a highly elastic thin carbon fiber which has never been used in the past, and has the above-mentioned uniformity, and thus is suitable for improving the rigidity and weight saving of a tubular composite molded article Is. In particular, it is suitable as an original fabric of a unidirectional prepreg for a slit tape used for reinforcing a tubular body.

[0025]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples.

Example 1 (Production of Purified Pitch) Coal tar pitch having a quinoline insoluble content removed and a softening point of 80 ° C. was used as a raw material, and direct hydrogenation was carried out using a catalyst. After heat-treating this hydrogenated pitch at 480 ° C. under normal pressure, the low boiling point was removed to obtain mesophase pitch. The softening point of this pitch is 300 ° C,
The mesophase content was 95%. This pitch was filtered at a temperature of 340 ° C. using a stainless fiber filter having a filtration accuracy of 3 μm to remove foreign matter in the pitch to obtain a purified pitch.

(Production of Pitch Fiber) Using this purified pitch as a spinning raw material, a nozzle plate having a diameter of 220 mm and a nozzle pack having a capillary diameter of 1000 m, a capillary length of 150 μm and a number of 2000 capillaries was used. The arrangement of capillaries is in the form of Figure 5,
The capillary position on the outermost circumference has a radius of 100 mm,
The innermost circumference has a radius of 75 mm, and a block in which 11 rows of capillaries are concentrically arranged is divided into four at intervals of 23 °. At the center of the nozzle, a columnar protrusion having a height of 50 mm and a diameter of 120 mm and having a sectional shape of FIG. 9 was attached. In addition, the outer diameter of the nozzle plate is 300 mm,
A slit having a width of 15 mm was provided, and suction was performed by dividing the slit from four directions. Nozzle plate surface temperature 316 ° C, spinning viscosity 600 poise, pitch flow rate per capillary of 0.
The roll was rotated and stretched at 043 g / min so that the spinning speed was 400 m / min, and the obtained pitch fiber was drawn by a suction nozzle and stored in a can. At this time, there was no yarn breakage for a long time of 6 hours, and the average fiber diameter was 9.8μ.
A pitch fiber having m and 2,000 filaments was obtained.

(Production of Carbon Fiber Bundle) Next, while the pitch fiber was housed in a can, while blowing an oxidizing gas obtained by adding 5% by volume of nitrogen dioxide gas to the air from the lower part of the can to 150 ° C. to 300 ° C., 1 ° C. The temperature was raised at a rate of 1 / min, and the temperature was maintained at 300 ° C. for 30 minutes to obtain infusible fiber. With the infusible fiber stored in a can, the infusible fiber was heated at a rate of 10 ° C./min in a nitrogen gas atmosphere to 390 ° C. and maintained at that temperature for 30 minutes for primary carbonization. Next, this primary carbonized yarn was linearly fired while winding the fiber yarn from the can into a furnace having an internal temperature of 1,100 ° C. and a nitrogen gas atmosphere, and wound on a bobbin. The carbonized fiber yarn was rewound from the obtained bobbin for graphitization at a temperature of 2,400 ° C. After surface oxidation, a sizing agent was applied and dried, and the bobbin was wound up. The characteristics of the obtained carbon fiber bundle are shown in Table 1 as N
o. Shown in 1.

(Production of prepreg) This carbon fiber bundle 18
Using a six-way unidirectional prepreg manufacturing apparatus as shown in FIG. 15, by using a release paper coated with a predetermined amount of epoxy resin,
Width of fiber basis weight 30 g / m ² , resin content 42 wt% 1,
A unidirectional prepreg with a cover film of 000 mm was manufactured. The obtained prepreg (No. 1 in Table 1) had a good appearance with no openings or fluff.

Example 2 Three spinning nozzles used in Example 1 were arranged in a straight line in parallel, and a pitch fiber extruded from three nozzles by one roll located below the spinning nozzle located in the center of the three spinning nozzles. Were simultaneously drawn and spun. The spinning conditions at this time are: nozzle plate surface temperature of 316 ° C., spinning viscosity of 600 poises,
With the pitch flow rate per capillary set to 0.035 g / min, the roll was rotated and stretched so that the spinning speed was 400 m / min, and the obtained pitch fiber was drawn by a suction nozzle and stored in a can. At this time, there was no yarn breakage for a long time of 2 hours, and pitch fibers having an average fiber diameter of 8.8 μm and a number of filaments of 6,000 were obtained.

This pitch fiber was prepared under the same conditions as in Example 1,
Infusibilization, carbonization, graphitization at a temperature of 2,500 ° C., surface oxidation, application of a sizing agent, drying, and winding on a bobbin. The characteristics of the obtained carbon fiber bundle are shown in Table 1 as N
o. 2 shows. Using this 139 carbon fiber bundles, a release paper coated with a predetermined amount of epoxy resin in the same prepreg manufacturing apparatus as in Example 1 was used to form a cover having a fiber areal weight of 55 g / m ² and a resin content of 38 wt% and a width of 1,000 mm. A unidirectional prepreg with a film was manufactured. The resulting prepreg (No. 2 in Table 1) had a good appearance with no openings or fluff.

Example 3 The prepreg obtained in Example 1 was cut to a width of 250 mm, and the release paper was peeled off and wound up to a length of 205 m. Next, this prepreg having a width of 250 mm was slit to obtain a slit tape having a width of 5 mm and a length of 200 m. The slit tape thus obtained had a width of 5.0 mm ± 0.1 mm and had a neat winding appearance. In addition, remove the cover film from this slit tape with a taping machine,
As a result of being wound on a core metal having a length of 1 mm and a length of 1,100 mm, the unwinding property was good, and the wound tape had no fiber breakage.

Example 4 The prepreg produced in Example 2 was processed in the same manner as in Example 3 to obtain a slit tape having a width of 7 mm and a length of 205 m. The slit tape thus obtained had a width of 7.0 mm ± 0.1 mm and had a beautiful winding appearance. Further, as a result of performing a taping test similar to that of Example 3 on this slit tape,
The unwinding property was good, and there was no fiber break in the wound tape.

Comparative Example 1 The refined pitch used in Example 1 was used as a spinning raw material and had a diameter of 22.
Capillary diameter 100μm on 0mm nozzle plate,
Spinning was performed under the same drawing conditions as in Example 1 using a nozzle pack having a capillary length of 150 μm and a number of capillaries of 500, and the average fiber diameter was 9.8 μm and the number of filaments was 500.
A book of pitch fibers was obtained. This pitch fiber was infusibilized and primary carbonized under the same conditions as in Example 1. Next, this primary carbonized yarn was combined into a furnace in a nitrogen gas atmosphere at an internal temperature of 1,100 ° C. while four filament yarns were being fed from the four cans while being combined into four filaments and fired into a linear shape. The yarn was wound on a bobbin as a fiber bundle. The carbonization fiber yarn was rewound from the obtained bobbin, and the same graphitization as in Example 1 was performed. After surface oxidation, a sizing agent was applied and dried, and the bobbin was wound. The characteristics of the obtained carbon fiber bundle are shown in Table 1 as No. 3 shows. A unidirectional prepreg similar to that of Example 1 was manufactured using 186 carbon fiber bundles. The obtained prepreg (No.
In 3), the openings were frequent, the fibers meandered, and the uniformity and appearance were poor.

Comparative Example 2 Pitch fibers having an average fiber diameter of 8.8 μm and 2,000 filaments were obtained under the same drawing conditions as in Example 2 with the spinning nozzle used in Example 1. This pitch fiber was infusibilized and primary carbonized under the same conditions as in Example 1. Next, this primary carbonized yarn was wound into a linear shape by winding three filament yarns from three cans into a furnace having an internal temperature of 1,100 ° C. and a nitrogen gas atmosphere, fired linearly, and wound on a bobbin. The carbonized fiber yarn was rewound from the obtained bobbin for graphitization at a temperature of 2,500 ° C. After surface oxidation, a sizing agent was applied and dried to wind the bobbin. The characteristics of the obtained carbon fiber bundle are shown in Table 1 as No. 4 shows. Using this 139 carbon fiber bundles, the same unidirectional prepreg as in Example 1 was manufactured. The resulting prepreg (No. 4 in Table 1) had frequent openings, fiber meandering, and poor uniformity and appearance.

Comparative Example 3 The prepreg obtained in Comparative Example 1 was processed in the same manner as in Example 3 to obtain a slit tape having a width of 5 mm and a length of 200 m. The width of the tape was 3.5 mm in some places, and the uniformity of the width was poor. Also, in this slit tape, whiskers-like fibers were projected on the winding side surface. As a result of performing a taping test similar to that in Example 3, the tape was frequently broken.

Comparative Example 4 A slit tape having a width of 7 mm and a length of 200 m was obtained from the prepreg manufactured in Comparative Example 2 in the same manner as in Example 4. The slit tape had a width of 5 to 6 mm, and the width was uneven. As a result of performing a taping test on this slit tape in the same manner as in Example 3, there was no fiber breakage.
The winding pitch was uneven and could not be evenly wound.

Comparative Example 5 The nozzle used in Example 1 had a capillary diameter of 130 μm.
And the pitch flow rate per capillary is 0.069 g /
Spinning was performed under the same conditions as in Example 1 except that the average fiber diameter was 12.9 μm and the number of filaments was 2,000.
The pitch fiber of was obtained. The pitch fiber was infusibilized and carbonized under the same conditions as in Example 1, graphitized at a temperature of 2,500 ° C., surface-oxidized, a sizing agent was added and dried, and then wound on a bobbin. The characteristics of the obtained carbon fiber bundle are shown in Table 1 as No. 5 shows. Using this 172 carbon fiber bundles, a unidirectional prepreg similar to that in Example 2 was manufactured. The obtained prepreg (No. 5 in Table 1) had no openings, but had many filament-like fluff on the surface of the prepreg.

[0039]

[Table 1]

Comparative Example 6 The prepreg produced in Comparative Example 5 was processed in the same manner as in Example 4 to obtain a slit tape having a width of 7 mm and a length of 225 m. Using this slit tape, a taping test was conducted in the same manner as in Example 3, and as a result, fiber breakage was observed on the tape wound around the core metal.

Example 6 A prepreg of PAN-based carbon fiber (fiber basis weight 100 g / m ² , resin content 28 wt%) was applied 3 times in a 0 ° direction to a core metal having a diameter of 21 mm, and then the slit obtained in Example 4 was used. The tape was wound at a pitch of 7 mm in the 90 ° direction, and after the tape was wrapped, the tape was cured under predetermined conditions to obtain a pipe molded product. The 4-point bending strength of this pipe was 15% higher than that of a pipe molded product having the same laminated structure using the slit tape obtained in Comparative Example 6.

[0042]

The prepreg according to the present invention is a unidirectional prepreg with a low basis weight which is made of a high elasticity thin carbon fiber which has never been used, and has almost no openings.
Since the thickness is uniform, it is suitable for improving the rigidity and reducing the weight of the tubular composite molded product.

[Brief description of drawings]

FIG. 1 is a drawing for explaining an example of a production method for obtaining a carbon fiber bundle used in the present invention, and is a cross-sectional view of a melt spinning nozzle.

FIG. 2 is a drawing for explaining an example of a production method for obtaining a carbon fiber bundle used in the present invention, and is a bottom view of a melt spinning nozzle.

FIG. 3 is a drawing for explaining an example of a manufacturing method for obtaining a carbon fiber bundle used in the present invention, and is a capillary arrangement view of nozzles.

FIG. 4 is a capillary arrangement diagram of nozzles similar to FIG.

FIG. 5 is a capillary layout diagram of the nozzles similar to FIG.

FIG. 6 is a capillary arrangement view of nozzles similar to FIG.

FIG. 7 is a capillary arrangement view of the nozzles similar to FIG.

FIG. 8 is a capillary arrangement view of the nozzles similar to FIG.

FIG. 9 is a drawing for explaining an example of a manufacturing method for obtaining a carbon fiber bundle used in the present invention, and is a side view of a cylindrical protrusion.

FIG. 10 is a side view of a columnar protrusion similar to FIG.

FIG. 11 is a side view of a columnar protrusion similar to FIG.

FIG. 12 is a side view of a columnar protrusion similar to FIG.

FIG. 13 is a drawing for explaining an example of a production method for obtaining a carbon fiber bundle used in the present invention, and is a schematic diagram of a melt spinning apparatus.

FIG. 14 is a schematic diagram showing a method for measuring bending strength in order to explain the bending strength.

FIG. 15 is a schematic view showing a prepreg manufacturing apparatus suitable for obtaining the unidirectional prepreg of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Melting pitch, 2 ... Nozzle plate, 3 ... Cylindrical protrusion, 4 ... Suction slit, 6 Suction amount adjustment damper, 8
... Pitch fiber, 9 ... Capillary, 10 ... Nozzle plate retainer, 11 ... Capillary arrangement block, 12 ... Melt spinning device, 13 ... Stretching roll conveying roll, 14 ... Pitch fiber conveying roll, 15 ... Pitch fiber bundle suction nozzle, 16
... Pitch fiber storage cans, 17 ... Carbon fiber bundles, 18 ... Tabs, 19 ... Wires with a diameter of 1.0 mm, 20 ... Load cells, 21
... creel stand, 22 ... bobbin, 23 ... carbon fiber bundle, 24 ... comb, 25 ... bar, 26 ... coated paper, 27,
28, 29 ... Nip roll, 30 ... Heater, 31 ... Chiller plate, 32 ... Release paper, 33 ... Cover film,
34 ... Pull roll, 35 ... One-way prepreg, 36 ... Winder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Arai 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa, Nippon Steel Corporation Advanced Technology Research Laboratories

Claims (4)

[Claims] 1. A unidirectional prepreg having a fiber basis weight of 15 to 75 g / m ² in which fiber bundles are aligned and impregnated with a thermosetting resin, and the fiber bundles are continuous fibers having an average fiber diameter of 4 to 8 μm, and A unidirectional prepreg, which is a pitch-based carbon fiber bundle composed of non-bonded yarns. 2. The number of filaments constituting the fiber bundle is 2,
The one-way prepreg according to claim 1, wherein the number is 000 to 12,000. 3. The unidirectional prepreg according to claim 1, wherein the filaments constituting the fiber bundle have a tensile strength of 3.0 GPa or more and a tensile modulus of 600 GPa or more. 4. The flexural strength B of the fiber bundle is expressed by the following formula B ≧ (2.875 × 10 ⁻⁴ TM-0.17) ⁻¹ [where B: flexural strength (MPa), TM: tensile modulus (GPa)]. )] Is satisfied, the one-way prepreg according to claim 1 or 3.