JP2013203943A - Carbon fiber prepreg, carbon fiber prepreg tape, carbon fiber-reinforced composite material and vehicle component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg which has small thickness deviation, is hardly cracked and is thin though the fineness of a fiber bundle is large and a so-called large tow-type carbon fiber bundle is used and to provide a carbon fiber-reinforced composite material which has excellent mechanical properties and is suitable for vehicle components.SOLUTION: A carbon fiber prepreg is obtained by pulling/aligning a plurality of carbon fiber bundles (A), each of which is configured so that the average fineness of single fibers may be 1.0-2.4 dtex and the total fineness thereof is 30,000-67,000 dtex, to one direction and impregnating the plurality of aligned carbon fiber bundles with a matrix resin (B). A sizing agent (C) containing 60-100 mass% of a polyalkylene group is stuck to the carbon fiber bundle (A) while controlling so that the amount of the (C) component to be stuck to the (A) component is 0.2-2.4 mass%. The average roundness of the single fibers of the carbon fiber bundle (A) is 0.70-0.90.

Description

  The present invention relates to a carbon fiber prepreg, a carbon fiber prepreg tape, a carbon fiber reinforced composite material, and an automotive part.

  One method of forming a carbon fiber reinforced composite material is to use a prepreg formed by impregnating a carbon fiber with a matrix resin. The carbon fiber reinforced composite material used for the prepreg is used in a wide range of applications from sports and leisure related applications to aircraft applications. In addition, a carbon fiber reinforced composite material in which a matrix resin is a thermoplastic resin is excellent in impact resistance and has a short molding time, and is therefore optimal for automotive parts and the like. (Patent Document 1)

  In recent years, carbon fiber bundles having a total fineness of 30000 dtex or more, so-called large tow type carbon fiber bundles, have been put on the market, and development for prepregs using the carbon fiber bundles is indispensable for expanding the demand for carbon fibers.

  In the production of prepregs, it is important to reduce the production efficiency and the production cost while ensuring the required quality and quality, and for this purpose, it is necessary to make the prepregs with less thickness unevenness even with a low basis weight. However, when a large tow type carbon fiber bundle is used, due to the large number of filaments in the carbon fiber bundle, the opening property is inferior, the portion where the opening width is narrow has a thickness, and there is a gap between adjacent yarns. To cause cracks. Moreover, when using a fiber bundle with inferior openability, there is also a problem that the production rate is reduced because the processing speed of the prepreg must be reduced. In addition, the thickness unevenness decreases the impregnation property with the resin, and the smoothness is deteriorated due to local peeling from the release paper and generation of wrinkles, leading to a quality defect of the prepreg. In particular, when a thermoplastic resin is used as the matrix resin, since the viscosity at the time of impregnation is higher than that of a thermoplastic resin such as an epoxy resin, the decrease in impregnation due to thickness unevenness is significant. In the carbon fiber reinforced composite material formed using such a thick spot or poorly impregnated prepreg, the thick spot part or poorly impregnated part becomes a starting point of destruction, and there is a problem that the mechanical properties of the carbon fiber reinforced composite material are deteriorated. is there.

Japanese Patent Laid-Open No. 9-155862

  An object of the present invention is to provide a thin prepreg having a large thickness of fiber bundles, a so-called large tow type carbon fiber bundle with little thickness unevenness and cracking, and having good mechanical properties and automotive parts. It is providing the carbon fiber reinforced composite material suitable for.

In order to solve the above problems, in the present invention, a plurality of carbon fiber bundles (A) having an average single fiber fineness of 1.0 to 2.4 dtex and a total fineness of 30000 to 67000 dtex are aligned in one direction. In the carbon fiber prepreg impregnated in the matrix resin (B), a sizing agent (C) containing 60% by mass to 100% by mass of a polyoxyalkylene group is attached to the carbon fiber bundle (A). C) A carbon fiber prepreg in which the adhesion amount of component (A) to component (A) is 0.2 to 2.4% by mass, and the average single fiber roundness of carbon fiber bundle (A) is 0.70 to 0.70. The sized carbon fiber prepreg of claim 1 which is 0.90. However, the roundness is a value obtained by the following formula (I), and S and L are obtained by image analysis of the cross section perpendicular to the fiber axis of the single fiber by SEM observation. Cross-sectional area and perimeter.
Roundness = 4πS / L ² (I)

  ADVANTAGE OF THE INVENTION According to this invention, although it is what is called a large tow type carbon fiber bundle with the fineness of a fiber bundle, it can provide a thin prepreg with few thickness spots and cracks, and it is suitable for automotive parts with good mechanical properties. A carbon fiber reinforced composite material can be provided.

Hereinafter, the present invention will be described in detail.
≪Carbon fiber thermal prepreg≫
In the carbon fiber prepreg of the present invention, a plurality of carbon fiber bundles (A) having an average single fiber fineness of 1.0 to 2.4 dtex and a total fineness of 30000 to 67000 dtex are aligned in one direction to form a matrix resin (B In the carbon fiber prepreg impregnated in (1), a sizing agent (C) containing 60% by mass to 100% by mass of a polyoxyalkylene group is attached to the carbon fiber bundle (A). A carbon fiber prepreg having an adhesion amount to the component (A) of 0.2 to 2.4% by mass, and the average single fiber roundness of the carbon fiber bundle (A) is 0.70 to 0.90. The sized carbon fiber prepreg according to claim 1. However, the roundness is a value obtained by the following formula (I), and S and L are obtained by image analysis of the cross section perpendicular to the fiber axis of the single fiber by SEM observation. Cross-sectional area and perimeter.
Roundness = 4πS / L ² (I)

The fiber basis weight and fiber content of the carbon fiber prepreg are not particularly limited, but preferably the fiber basis weight is 20 to 150 g / m ² and the fiber content is 25 to 60% by volume. More preferably, the fiber basis weight is 40 to 115 g / m ² and the fiber content is 35 to 50% by volume.

When the fiber basis weight is less than 20 g / m ² , when the tension required to sufficiently widen the carbon fiber bundle is applied, the carbon fiber bundle is abraded and fluff and thread damage occur, leading to a deterioration in the quality of the prepreg. .

If the fiber basis weight exceeds 150 g / m ² , the prepreg of the required quality and quality can be obtained if the production efficiency is lowered even with the conventional technology. However, when the fiber basis weight is 150 g / m ² or less, the fiber basis weight is particularly 115 g. The present invention is effective when it is less than / m ² .

<Carbon fiber bundle (A)>
The total fineness of the carbon fiber bundle (A) used in the present invention is limited to 30000 to 67000 dtex. When a carbon fiber bundle having a total fineness of less than 30000 dtex is used, a prepreg having the required quality and quality can be obtained by reducing the production efficiency even in the prior art. When it exceeds 67000 dtex, even if the present invention is applied, good openability cannot be obtained, resulting in a prepreg having many thickness spots and cracks.

  The single fiber constituting the carbon fiber bundle (A) needs to have an average single fiber fineness of 1.0 to 2.4 dtex. By setting the average single fiber fineness to 1.0 dtex or more, due to a decrease in the contact area between the metal guide bar and the fiber at the time of opening, the unevenness of the contact resistance of the yarn is reduced, so There is less cracking. When it exceeds 2.4 dtex, in the case of a low fiber basis weight, a decrease in the number of filaments in a unit width in the prepreg causes spread spots, which causes thickness spots and cracks. Moreover, it is preferable to make it less than 2.4 dtex because the cross-sectional double structure of the carbon fiber is appropriate, the strand strength / elastic modulus is not lowered, and the mechanical properties of the carbon fiber reinforced composite material are not lowered.

The single fiber constituting the carbon fiber bundle (A) preferably has an average single fiber roundness of 0.70 to 0.90. By setting the average single fiber roundness to 0.90 or less, the long axis of the elliptical single fiber is aligned in the opening direction at the time of opening, so that a good opening property is obtained, and thickness irregularities and cracks are obtained. The prepreg with less. On the other hand, when it is less than 0.70, good opening property can be obtained. However, when the carbon fiber reinforced composite material is used, the mechanical properties of the carbon fiber reinforced composite material are lowered due to local stress concentration in the filament. However, the roundness is a value obtained by the following formula (II), and S and L are obtained by image analysis of the cross section perpendicular to the fiber axis of the single fiber by SEM observation. Cross-sectional area and perimeter.
Roundness = 4πS / L ² (II)

  The type of the carbon fiber bundle (A) used in the present invention is not particularly limited, and examples thereof include PAN-based carbon fibers and PICH-based carbon fibers. One type may be used alone, or two or more types may be used in combination. However, PAN-based carbon fibers can be used particularly preferably.

<Matrix resin (B)>
The matrix resin (B) used in the present invention is not particularly limited, but the present invention is particularly effective when a thermoplastic resin is used for the matrix resin (B). Examples of the thermoplastic resin include polycarbonate resin, polyester resin, polyamide resin, liquid crystal polymer resin, polyether sulfone resin, polyether ether ketone resin, polyarylate resin, polyphenylene ether resin, polyphenylene sulfide resin, polyacetal resin, polysulfone. Examples thereof include resins, polyimide resins, polyolefin resins, polystyrene resins, modified polystyrene resins, ABS resins, modified ABS resins, MBS resins, polymethyl methacrylate resins, modified resins thereof, and polymer alloy resins thereof. Any one of these may be used alone, or two or more may be used in combination, but a polypropylene resin and / or polyamide resin, or a modified resin of polypropylene resin and / or polyamide resin is preferable.

<Sizing agent (C)>
The sizing agent (C) used in the present invention needs to contain 60% by mass to 100% by mass of a polyoxyalkylene group. By setting it to 60% by mass or more, the frictional resistance between the yarn and the opening bar at the time of opening is appropriate, good opening property is obtained, and a prepreg with less thickness unevenness and cracking is obtained. The content mass fraction of the oxyalkylene group is determined by the charged amount and can be measured by NMR.

  The compound containing a polyoxyalkylene group is, for example, a polymer compound obtained by random or block copolymerization using an alkylene oxide such as ethylene oxide or propylene oxide as a monomer. The compound containing a polyoxyalkylene group used in the present invention may have a part having an aromatic ring structure such as a bisphenol A structure, a bisphenol F structure, or a bisphenol E structure, if necessary.

  As for the molecular weight of the compound containing the polyoxyalkylene group used by this invention, 400-20000 are preferable, More preferably, it is 1000-10000. When the molecular weight is less than 400, it has a melting point of room temperature (23 ° C.) to about 30 ° C., and changes from liquid to solid depending on the atmospheric temperature when handling the carbon fiber. Lacks stability. On the other hand, if it exceeds 20000, the fixing property is increased, the convergence property of the carbon fiber filament is increased, and the flexibility of the carbon fiber bundle and the opening property of the carbon fiber bundle in the resin impregnation step are significantly inhibited. .

  The amount of adhesion of the sizing agent (C) used in the present invention to the carbon fiber bundle (A) needs to be 0.2 to 2.4% by mass. If the amount is less than 0.2% by mass, the convergence and scratching properties tend to be insufficient, and fluff is likely to occur due to mechanical friction or the like. On the other hand, if the content exceeds 2.4% by mass, the coefficient of friction against the metal decreases and the convergence becomes strong, so that the openability of the carbon fiber bundle is deteriorated. The impregnation property of the matrix resin into the resin deteriorates.

<Sizing agent application method>
The sizing agent (C) used in the present invention can be applied to the carbon fiber bundle (A) by a known method, but the polyoxyalkylene group-containing compound used in the present invention is soluble in water. Therefore, it is desirable to use an aqueous solution. The use of an aqueous solution means that the sizing solution is stable and easy to handle, as compared with the case of sizing with an organic solvent solution such as acetone, and the hygienic and safety aspects of the working atmosphere. The advantage of is also obtained.

  As an example of the method for applying the sizing agent, for example, a roller dipping method or a roller contact method can be applied. In addition, the adhesion amount of the sizing agent to the carbon fiber can be adjusted by adjusting the concentration of the sizing agent aqueous solution, adjusting the passing process such as a drawing controller. After the sizing agent aqueous solution is attached to the surface of the carbon fiber, the moisture is removed by a subsequent drying process to obtain the desired sized carbon fiber. In addition, the method using a heat medium, such as a hot air, a hot plate, a roller, an infrared heater, can be applied to the drying process at this time.

<Method for producing carbon fiber prepreg>
The carbon fiber prepreg can be produced by a known method. Similarly, when a thermoplastic resin is used as the matrix resin, it can be produced by a known method. For example, a method of impregnating a molten resin with an extruder, a method of dispersing a powder resin in a fiber layer and melting, a resin A method of laminating a film, a method in which a resin is dissolved in a solvent and impregnated in the form of a solution, and then the solvent is volatilized. There is a method of polymerizing into a polymer. The method of impregnating the molten resin with an extruder has the advantage that the resin does not need to be processed, but it is difficult to produce a stable prepreg. The method of dispersing the powder resin in the fiber layer has an advantage that it is easily impregnated, but it is difficult to uniformly disperse the powder in the fiber layer. The method of laminating the resin into a film requires film processing, but tends to produce a relatively good quality.

  The step of impregnating the thermoplastic resin by the melting method is not only the extruder, but also a method of solidifying the prepreg after melt impregnation by a combination of a heating press and a cooling press, and a heating zone and a cooling zone are provided using a double belt press. There is a way. The method using a double belt press is excellent in productivity because it can be produced continuously.

≪Carbon fiber prepreg tape≫
The carbon fiber prepreg tape of the present invention is obtained by cutting the carbon fiber prepreg. The carbon fiber prepreg tape in the present invention can be produced by a known method. As an example, a technique using a cutting plotter or a technique using a slitter and a rotary cutter together can be mentioned. The width and length of the carbon fiber prepreg tape are not particularly limited.

≪Carbon fiber reinforced composite material≫
The carbon fiber reinforced composite material of the present invention can be obtained by heating or pressurizing and heating and cooling the carbon fiber prepreg and / or the carbon fiber prepreg tape. The carbon fiber reinforced composite material in the present invention can be produced by a known method. Examples include press molding and autoclave molding.

≪Automobile parts≫
The automotive part of the present invention is partly or wholly composed of the carbon fiber reinforced composite material.

Next, the present invention will be described in more detail with reference to examples.
The present invention is not limited to these examples.
The raw materials, carbon fiber thermoplastic prepreg production methods, carbon fiber composite material plate production methods, and physical property evaluation methods used in the following examples are shown below.

<Raw material>
Carbon fiber (A)
PAN-based carbon fiber bundle 1 (average single fiber fineness: 1.4 dtex, roundness: 0.87, number of filaments: 24000)
PAN-based carbon fiber bundle 2 (average single fiber fineness: 1.4 dtex, roundness: 0.82, number of filaments: 28000)
PAN-based carbon fiber bundle 3 (average single fiber fineness: 2.4 dtex, roundness: 0.83, number of filaments: 14000)
PAN-based carbon fiber bundle 4 (average single fiber fineness: 0.7 dtex, roundness: 0.72, number of filaments: 60000)
PAN-based carbon fiber bundle 5 (average single fiber fineness: 0.8 dtex, roundness: 0.85, number of filaments: 50000)

Matrix resin (B)
Modified polypropylene (Mitsubishi Chemical Corporation, product name: Modic P958 38 μm thick film)

Sizing agent (C)
Polyethylene glycol (molecular weight: 1500, oxyalkylene group content: 100% by mass)
Water-based epoxy resin (Mitsubishi Chemical Corporation, product name: jER W2821R70 (oxyalkylene group content: 22% by mass))

<Smoothness evaluation method>
Using a three-dimensional surface roughness measuring device, the measurement was performed at a detection speed of 0.5 mm / second and a width of 40 mm in a direction perpendicular to the prepreg fiber alignment direction. An average line that is an average value obtained from the detection curve is drawn, an average value of the maximum height from the maximum peak height measured in the thickness direction from any straight line that is parallel to the average line and does not cross the detection curve, and A difference between the average value of the height of the valley bottom from the deepest to the fifth and expressed in μm was calculated as a concavo-convex coefficient, and used as a scale representing thickness spots. The evaluation results are shown in Table 1.

<Checking method>
A gap having a width of 0.5 mm or more and a length of 20 mm or more existing between the aligned fibers per 1 m ^{2 of the} prepreg was used as a crack. The evaluation results are shown in Table 1.

Example 1
A sizing agent was applied to the PAN-based carbon fiber bundle 1 as a 5% by mass aqueous solution of raw material polyethylene glycol by a roller impregnation method, and water was dried with a steam heating roll at 120 ° C. The adhesion amount of the sizing agent to the carbon fiber bundle was 0.6% by mass. The 21 size-attached carbon fiber bundles obtained in this way are aligned to form a sheet-like material having a fiber weight of 70 g / m ^{2 having} a width of 1000 mm, and a carbon fiber prepreg is laminated by laminating a raw material-modified polypropylene film with a release paper at 240 ° C. Obtained. The smoothness and crack of this carbon fiber prepreg were evaluated.

(Example 2)
A carbon fiber prepreg was prepared in the same manner as in Example 1 except that the PAN-based carbon fiber bundle 2 was used instead of the PAN-based carbon fiber bundle 1 and the number of the aligned carbon fiber bundles was 18, and smoothness and cracking were achieved. evaluated.

(Example 3)
A carbon fiber prepreg was prepared in the same manner as in Example 1 except that the PAN-based carbon fiber bundle 3 was used instead of the PAN-based carbon fiber bundle 1 of polyethylene glycol 6, and smoothness and cracking were evaluated.

(Comparative Example 1)
A carbon fiber prepreg was prepared in the same manner as in Example 1 except that the PAN-based carbon fiber bundle 4 was used in place of the PAN-based carbon fiber bundle 1 and the number of the aligned carbon fiber bundles was 17, so that smoothness and cracking were achieved. evaluated.

(Comparative Example 2)
A carbon fiber prepreg was prepared in the same manner as in Example 1 except that the PAN-based carbon fiber bundle 5 was used in place of the PAN-based carbon fiber bundle 1 and the number of carbon fiber bundles to be aligned was 18, and smoothness and cracking were achieved. evaluated.

(Comparative Example 3)
A carbon fiber prepreg was prepared in the same manner as in Example 1 except that an aqueous 8-fold diluted aqueous solution of the raw water-based epoxy resin was used instead of the raw material ethylene glycol 5% by weight, and smoothness and cracking were evaluated.

Claims (7)

Carbon obtained by aligning a plurality of carbon fiber bundles (A) having an average single fiber fineness of 1.0 to 2.4 dtex and a total fineness of 30000 to 67000 dtex in one direction and impregnating the matrix resin (B). In fiber prepreg,
A sizing agent (C) containing 60% by mass to 100% by mass of a polyoxyalkylene group is attached to the carbon fiber bundle (A),
The adhesion amount of the component (C) to the component (A) is 0.2 to 2.4% by mass,
A carbon fiber prepreg in which the average single fiber roundness of the carbon fiber bundle (A) is 0.70 to 0.90.
However, the roundness is a value obtained by the following formula (I), and S and L are obtained by image analysis of the cross section perpendicular to the fiber axis of the single fiber by SEM observation. Cross-sectional area and perimeter.
Roundness = 4πS / L ² (I)   The carbon fiber prepreg according to claim 1, wherein the matrix resin (B) is a thermoplastic resin. Carbon fiber prepreg according to any one of claims 1 or 2 fiber basis weight of the carbon fiber prepreg is 40~115g / ^{m 2.}   A carbon fiber prepreg tape using the carbon fiber prepreg according to claim 1.   The carbon fiber reinforced composite material using the carbon fiber prepreg in any one of Claims 1-3.   A carbon fiber reinforced composite material using the carbon fiber prepreg tape according to claim 4.   An automotive part using the carbon fiber reinforced composite material according to claim 5.