JP2013209446A - Carbon fiber-reinforced thermoplastic plastic and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon fiber reinforced thermoplastic having a low pressing pressure during production and good fluidity.
In a carbon fiber reinforced thermoplastic plastic obtained by impregnating a carbon fiber web with a thermoplastic resin,
The carbon fiber web comprises at least a carbon fiber bundle (a) and a carbon fiber bundle (b), the carbon fiber bundle (a) has a fiber length of 5 to 15 mm, and the carbon fiber bundle (b) has a fiber length of less than 5 mm. The carbon fiber bundle (a) is 30 to 90% by mass, the carbon fiber bundle (b) is 10 to 70% by mass, and the carbon fiber bundle (a) and the carbon fiber bundle (b) This is solved by a carbon fiber reinforced thermoplastic made of a carbon fiber bundle having a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.7 to 0.90.
[Selection figure] None

Description

  The present invention relates to a carbon fiber reinforced thermoplastic and a method for producing the same.

  Carbon fiber reinforced thermoplastics made of carbon fiber and thermoplastic resin are widely used in electrical / electronic applications, civil engineering / architecture applications, automotive applications, aircraft applications and the like because of their excellent specific strength and specific rigidity. Discontinuous carbon fiber reinforced thermoplastics are materials that have better fluidity and can be molded into complex shapes than continuous carbon fiber reinforced thermoplastics. Among them, carbon fiber reinforced thermoplastics for press molding have attracted attention in recent years because they have a longer fiber length than injection molding materials and are excellent in mechanical strength. As a method for producing this press-molding substrate, there is a method of impregnating a reinforced carbon fiber web with a thermoplastic resin by laminating a reinforced carbon fiber web and a thermoplastic resin sheet, and heating and pressing. However, since the press-molded product has lower fluidity than the injection-molded product, further improvement is required.

JP 2011-157524 A

  By the way, the carbon fiber reinforced thermoplastic described in Patent Document 1 has improved strength and quality deterioration due to the pickle, but has not yet obtained sufficient fluidity. Further, the carbon fiber reinforced thermoplastic of Patent Document 1 requires high-pressure hot press molding for impregnating the thermoplastic resin, and the impregnation of the resin is not sufficient. Therefore, an object of the present invention is to obtain a carbon fiber reinforced thermoplastic having a low pressing pressure during production and good fluidity.

  The present invention provides a thermoplastic resin by forming a carbon fiber bundle having a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.7 to 0.90 and a carbon fiber bundle having different fiber lengths into a web. Disclosed is a carbon fiber reinforced thermoplastic having excellent impregnation and fluidity.

  The carbon fiber reinforced thermoplastic produced by the present invention refers to a molded body containing at least two types of carbon fiber and a thermoplastic resin serving as a matrix resin. The carbon fiber used in the present invention is a glass fiber, carbon fiber, metal fiber, aromatic polyamide fiber, polyaramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and the like, which are used in combination with high strength, high elasticity fiber. Two or more kinds may be mixed.

  According to the present invention, it is possible to provide a carbon fiber reinforced thermoplastic plastic having excellent mechanical properties, good resin impregnation properties and good fluidity during molding, and a method for producing the same.

  The carbon fiber reinforced thermoplastic resin plastic of the present invention is a carbon fiber reinforced thermoplastic using a carbon fiber web containing at least a carbon fiber bundle (a) and a carbon fiber bundle (b), and a method for producing the same.

  Examples of the carbon fiber include PAN-based carbon fiber, pitch-based carbon fiber, cellulose-based carbon fiber, vapor-grown carbon fiber, and graphitized fibers thereof. PAN-based carbon fibers are carbon fibers made from polyacrylonitrile fibers. Pitch-based carbon fiber is carbon fiber made from petroleum tar or petroleum pitch. Cellulosic carbon fibers are carbon fibers made from viscose rayon, cellulose acetate, or the like. Vapor-grown carbon fibers are carbon fibers made from hydrocarbons or the like. Of these, PAN-based carbon fibers are preferable because they are excellent in balance between strength and elastic modulus.

  The carbon fiber used in the present invention is a glass fiber, carbon fiber, metal fiber, aromatic polyamide fiber, polyaramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and the like, which are used in combination with high strength, high elasticity fiber. Two or more kinds may be mixed.

  The carbon fiber bundle is preferably a discontinuous fiber bundle, and more preferably a chopped fiber. The number of single fibers constituting the carbon fiber bundle is not particularly limited, but is preferably 12,000 or more, more preferably 48,000 or more from the viewpoint of productivity. The upper limit of the number of single fibers is not particularly limited, but considering the balance between dispersibility and handleability, it is possible to maintain good productivity, dispersibility, and handleability with about 640,000. .

  In the present invention, only a carbon fiber bundle having a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.70 to 0.90 is used. When the single fiber fineness is less than 1.0 dtex, the gap due to the overlap of the fibers becomes narrow and the dispersibility of the web is poor, and good fluidity and resin impregnation are not obtained. On the other hand, when the single fiber fineness is larger than 2.4 dtex, the carbon fibers do not overlap closely, so the handling of the web is bad and good strength cannot be obtained.

  The roundness of the carbon fiber is preferably slightly flat. When the roundness is larger than 0.90, the contact surface of the fiber becomes small and the strength is hardly developed. If the roundness is less than 0.70, the fluidity is deteriorated and a large resin molded part cannot be produced.

  As the carbon fiber bundle (a) and the carbon fiber bundle (b), fiber bundles having different fiber lengths are used. When only reinforcing fiber bundles having the same fiber length are used, the object of the present invention cannot be achieved.

  The length of the fiber bundle means the length of the fiber constituting the fiber bundle, and can be adjusted by cutting the fiber to a predetermined length when preparing the fiber bundle.

  The fiber length of the carbon fiber bundle (a) is 5 to 15 mm, and more preferably 6 to 15 mm. The fiber length of the carbon fiber bundle (b) is less than 5 mm, and preferably 4 mm or less. The lower limit of the length of the carbon fiber bundle is usually 0.1 mm or more. When the carbon fiber bundle (a) or the carbon fiber bundle (b) is used alone, if the carbon fiber length is less than 5 mm, the reinforcing effect of the fiber is low, and there is a problem in the handling property that the base material is torn during the paper making process. On the other hand, when it exceeds 50 mm, it becomes difficult to disperse the single fiber, and when a carbon fiber web is produced, it becomes easy to make a pickle. The mechanical properties and quality of carbon fiber reinforced thermoplastics obtained from carbon fiber webs made from such carbon fibers are reduced. When the carbon fiber bundle (a) and the carbon fiber bundle (b) are mixed and the carbon fiber web is used, the reinforcing effect of the reinforcing fiber can be expressed by the carbon fiber bundle (a), and the reinforcing fiber can be obtained by the carbon fiber bundle (b). The effect of improving the dispersibility of the fiber bundle during papermaking is exhibited, and as a result of mixing these, a carbon fiber reinforced thermoplastic having good quality and excellent mechanical properties can be realized.

  It is important that the mixing ratio of the carbon fiber bundle (a) and the carbon fiber bundle (b) is carbon fiber bundle (a): carbon fiber bundle (b) = 30: 70 to 90:10 in mass ratio. More preferably, it is 50: 50-70: 30. When the reinforcing fiber bundle (a) is less than 30% by mass, the reinforcing effect of the reinforcing fiber is reduced, and when the reinforcing fiber bundle (a) is 90% by mass or more, the dispersibility of the reinforcing fiber is deteriorated. By setting it within the above range, it is possible to obtain a reinforced fiber web excellent in dispersion state, and to realize a fiber reinforced thermoplastic having good quality and excellent mechanical properties.

The carbon fiber web preferably has 5 to 15 mm of carbon fibers having a single fiber content of 20 to 70% and less than 5 mm of carbon fibers of 30 to 80%. When the number of fibers of 5 to 15 mm is less than 20%, the reinforcing effect of the reinforcing fiber is reduced, and when it is 70% or more, the dispersibility of the reinforcing fiber is deteriorated.
By blending the carbon fiber bundle (a) and the carbon fiber bundle (b) at such a ratio, the reinforcing effect of the carbon fiber bundle (a) and the uniform dispersibility of the carbon fiber bundle (b) are compatible. It can be expressed.

  There is no restriction | limiting in particular as a kind of thermoplastic resin. For example, polypropylene, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, aromatic polycarbonate, polyetherimide, polyarylene oxide, thermoplastic polyimide, polyamideimide, poly Examples include butylene terephthalate, polyethylene terephthalate, polyethylene, polyamide (nylon), acrylonitrile-butadiene-styrene (ABS) resin, copolymers thereof, modified products, and resins obtained by blending two or more types. Moreover, in order to provide a flame retardance and electroconductivity, resin may contain the additive.

Basis weight of the carbon fiber web is preferably 10 to 500 g / ^{m 2,} and more preferably 50 to 300 g / ^{m 2.} If it is less than 10 g / m ² , there is a risk of problems in handling such as tearing of the substrate. If it exceeds 500 g / m ² , it takes a long time to dry the substrate in the wet method, or the web in the dry method. May become thick, and handling may become difficult in subsequent processes.

Next, a method for producing a carbon fiber reinforced thermoplastic according to the present invention will be described.
In the production method of the present invention, a carbon fiber web is obtained by using the carbon fiber bundle (a) and the carbon fiber bundle (b), and the carbon fiber web is impregnated with a thermoplastic resin to obtain a carbon fiber reinforced thermoplastic plastic. Is what you get.

  Papermaking can be performed by either a wet method or a dry method. The wet method is a method of making paper by dispersing carbon fiber bundles in water, and the dry method is a method of making paper by dispersing carbon fiber bundles in air. In the case of the wet method, a carbon fiber web can be obtained by making a slurry obtained by dispersing the carbon fiber bundle (a) and the carbon fiber bundle (b) in water.

  The carbon fiber web is impregnated with a thermoplastic resin by heating and melting the resin to impregnate the fiber reinforcement (melt impregnation method), or by adding a powdered resin to the fiber reinforcement by a fluidized bed method or a suspension method. Any method can be used, such as a method of applying and fusing to a fiber (powder method), a method of dissolving a resin and removing the solvent after impregnating the fiber reinforcement (solution impregnation method), but using a melt impregnation method Is preferred. Moreover, when impregnating a carbon fiber web with a thermoplastic resin, you may laminate | stack a carbon fiber web.

Basis weight of the carbon fiber reinforced thermoplastic plastic is preferably 100~5000g / ^{m 2,} and more preferably 200~5000g / ^{m 2.} If it is less than 100 g / m ² , there is a risk of problems in handling such as tearing of the substrate in the process, and if it exceeds 5000 g / m ² , the thickness of the carbon fiber reinforced thermoplastic becomes large, and winding or cutting Is difficult to manufacture.
The carbon fiber web is 5 to 90% by mass, the thermoplastic resin is preferably 10 to 95% by mass, the carbon fiber web is 20 to 80% by mass, and the thermoplastic resin is 20 to 80% by mass. Is more preferable. If the carbon reinforcing fiber web is less than 5% by mass, the effect of reinforcing fibers cannot be obtained, and if it exceeds 80% by mass, impregnation with the thermoplastic resin may be difficult.

  Examples The fiber-reinforced molding substrate of the present invention will be specifically described below with reference to examples, but the following examples do not limit the present invention.

[Void rate]
The void ratio was used as an index representing the quality of the resin impregnation into the sheet-like reinforcing fiber material. Measured by sulfuric acid decomposition method.

[Press fluidity]
A carbon fiber web and a polypropylene resin film were cut out and laminated to 150 mm × 150 mm, and this laminate was press-molded at a temperature of 200 ° C. and a pressure of 20 MPa for 5 minutes to obtain a carbon fiber reinforced molding substrate. A carbon fiber reinforced molding substrate was cut into a thickness of 70 × 70 × 4 mm to obtain a fluidity evaluation sample. A fluidity evaluation sample was set in a flat plate mold of 100 × 100 × 2 mm, press-molded for 5 minutes at a temperature of 200 ° C., 20 MPa, and 10 MPa, and evaluated according to the following three stages depending on the filling condition. .
○: Filling is possible under any conditions of 20 MPa and 10 MPa.
Δ: Fillable at 20 MPa, unfilled portion can be confirmed at 10 MPa.
X: An unfilled part can be confirmed under any conditions of 20 MPa and 10 MPa.

[CF1-CF5 carbon fiber]
CF1: 1.4 dtex PAN-based carbon fiber, single fiber fineness 1.4 dtex, single fiber diameter 10 μm, single fiber roundness 0.87, fiber length 6.4 mm
CF2: 1.4 dtex PAN-based carbon fiber, single fiber fineness 1.4 dtex, single fiber diameter 10 μm, single fiber roundness 0.87, fiber length 3.2 mm
CF3: 2.4 dtex PAN-based carbon fiber, single fiber fineness 2.4 dtex, single fiber diameter 13 μm, single fiber roundness 0.87, fiber length 6.4 mm
CF4: 2.4 dtex PAN-based carbon fiber, single fiber fineness 2.4 dtex, single fiber diameter 13 μm, single fiber roundness 0.87, fiber length 3.2 mm
CF5: 1.4 dtex PAN-based carbon fiber, single fiber fineness 1.4 dtex, single fiber diameter 10 μm, single fiber roundness 0.75, fiber length 6.4 mm
CF6: 1.4 dtex PAN-based carbon fiber, single fiber fineness 1.4 dtex, single fiber diameter 10 μm, single fiber roundness 0.75, fiber length 3.2 mm
CF7: 0.7 dtex PAN-based carbon fiber, single fiber fineness 0.7 dtex, single fiber diameter 7 μm, single fiber roundness 0.90, fiber length 6.4 mm
CF8: 0.7 dtex PAN-based carbon fiber, single fiber fineness 0.7 dtex, single fiber diameter 7 μm, single fiber roundness 0.90, fiber length 3.2 mm

[Thermoplastic resin]
・ Polypropylene resin (Nippon Polypro Co., Ltd., trade name “NOVATEC PP” (registered trademark) SA06A)

[Dispersion medium (B1)]
Water and a water-soluble polymer (manufactured by Sumitomo Seika Co., Ltd., trade name: PEO-8Z) were mixed to obtain a dispersion medium having a concentration of 0.25% by mass. The viscosity of the dispersion medium measured with a B-type viscometer was 10 mPa · s.

[Mesh (C1)]
A plastic wire mesh (manufactured by Nippon Filcon Co., Ltd., SS-400 (trade name)) was used as the mesh 10 used for manufacturing the papermaking substrate.
Type: Double woven mesh opening area: 0.01 mm ²
Air permeability of mesh: 150 cm ³ / cm ² / s

[Example 1]
The carbon fiber bundle (a) was cut to 6.4 mm with a cartridge cutter to obtain chopped carbon fiber CF1. Moreover, the carbon fiber bundle was cut into 3.2 mm as the carbon fiber bundle (b) to obtain a carbon fiber bundle CF2.
A dispersion tank was used for the production. On the bottom surface of the 600 mm × 600 mm × 600 mm dispersion tank, a carbon fiber was dispersed and then a mesh was disposed to collect the carbon fiber. Further, in order to prevent the slack of the mesh, a mesh reinforcement having a mesh wire mesh attached on a perforated plate having a thickness of 20 mm is disposed below the mesh. A total of six fluid inlets, one on each side at 150 mm pitch on the opposite side of the side of the dispersion tank, and the fluid inlets facing each other so that the fluid introduced from the fluid inlet collides in the dispersion tank. Each axial center line was arranged at a position where it was almost a straight line.

Here, the nozzle diameter of the fluid inlet is 0.9 mm. 160 liters of dispersion medium is charged into the dispersion tank, 20 g of fiber bundle is charged into the dispersion tank, and then air is introduced from the fluid inlet at a flow rate of 6 liters / minute for 1 minute. After stirring, air introduction from the fluid inlet was stopped, and a slurry in which reinforcing fiber bundles were dispersed in units of reinforcing fibers was prepared. Immediately after stopping the introduction of air from the fluid inlet, the dispersion medium removal valve was opened, and the dispersion medium was removed from the slurry by vacuum suction to obtain a papermaking substrate made of carbon fibers having a basis weight of 60 g / m ² .

  The obtained papermaking substrate was dried at a temperature of 100 ° C. for 1 hour. A 150 × 150 papermaking substrate and a PP film were laminated, put into a 200 ° C. press hot platen, and press molded at 20 MPa for 10 minutes to obtain a carbon fiber reinforced thermoplastic resin plastic. Table 1 shows the operating conditions and the evaluation results of the obtained carbon fiber reinforced thermoplastic.

[Example 2]
A base material was obtained in the same manner as in Example 1 except that the mass ratio of the carbon fiber bundle (a) was 30% and the mass ratio of the carbon fiber bundle (b) was 70% and the mixture was charged into the dispersion tank. The execution conditions and the evaluation results of the obtained fiber-reinforced thermoplastic are shown in Table 1.

[Example 3]
A base material was obtained in the same manner as in Example 1 except that the mass ratio of the carbon fiber bundle (a) was 80% and the mass ratio of the carbon fiber bundle (b) was 20% and the mixture was charged into the dispersion tank. Table 1 shows the operating conditions and the evaluation results of the obtained carbon fiber reinforced thermoplastic.

[Example 4]
Example 1 except that CF3 carbon fiber was used and the mass ratio of the carbon fiber bundle (a) was 50%, and CF4 carbon fiber was used and the mass ratio of the carbon fiber bundle (b) was 50%. A substrate was obtained in the same manner. Table 1 shows the operating conditions and the evaluation results of the obtained carbon fiber reinforced thermoplastic.

[Example 5]
Example 1 except that CF5 carbon fiber was used and the mass ratio of the carbon fiber bundle (a) was 50%, and CF6 carbon fiber was used and the mass ratio of the carbon fiber bundle (b) was 50%. A substrate was obtained in the same manner. Table 1 shows the operating conditions and the evaluation results of the obtained carbon fiber reinforced thermoplastic.

[Comparative Example 1]
Reinforcing fiber webs were made with only CF1 carbon fiber bundles (a) having a length of 6.4 mm. Otherwise, a substrate was obtained in the same manner as in Example 1. The execution conditions and the evaluation results of the obtained fiber-reinforced thermoplastic are shown in Table 1.

[Comparative Example 2]
Example 1 except that CF7 carbon fiber was used and the mass ratio of the carbon fiber bundle (a) was 50%, and CF8 carbon fiber was used and the mass ratio of the carbon fiber bundle (b) was 50%. A substrate was obtained in the same manner. Table 1 shows the operating conditions and the evaluation results of the obtained carbon fiber reinforced thermoplastic.

[Comparative Example 3]
Example 1 except that CF7 carbon fibers were used and the mass ratio of carbon fiber bundles (a) was 70%, and CF8 carbon fibers were used and the mass ratio of carbon fiber bundles (b) was 30%. A substrate was obtained in the same manner. Table 1 shows the operating conditions and the evaluation results of the obtained carbon fiber reinforced thermoplastic.

  As is clear from Table 1, carbon fiber bundles (a) and carbon having different fiber lengths using carbon fibers having a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.70 to 0.90. The fiber bundle (b) was mixed and made, and a carbon fiber reinforced thermoplastic having excellent quality and moldability was obtained by using a carbon fiber web.

Claims (15)

In a carbon fiber reinforced thermoplastic obtained by impregnating a carbon fiber web with a thermoplastic resin,
The carbon fiber web comprises at least a carbon fiber bundle (a) and a carbon fiber bundle (b), the carbon fiber bundle (a) has a fiber length of 5 to 15 mm, and the carbon fiber bundle (b) has a fiber length of less than 5 mm. The carbon fiber bundle (a) is 30 to 90% by mass, the carbon fiber bundle (b) is 10 to 70% by mass, and the carbon fiber bundle (a) and the carbon fiber bundle (b) A carbon fiber reinforced thermoplastic comprising a carbon fiber bundle having a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.7 to 0.90.   2. The carbon fiber reinforced thermoplastic according to claim 1, wherein the carbon fiber web has a carbon fiber bundle (a) fiber number of 20 to 70% and a carbon fiber bundle (b) fiber number of 30 to 80%. .   The carbon fiber reinforced thermoplastic according to claim 1 or 2, wherein at least one of the carbon fiber bundle (a) and the carbon fiber bundle (b) is a combination of two or more different fiber lengths.   The carbon fiber reinforced thermoplastic according to claim 1 or 2, wherein each of the carbon fiber bundle (a) and the carbon fiber bundle (b) is composed of one kind of fiber length. The basis weight of the carbon fiber web is 10 to 500 g / ^{m 2,} carbon fiber reinforced thermoplastics as claimed in claim 1. The basis weight of the carbon fiber-reinforced thermoplastics is 100~5000g / ^{m 2,} carbon fiber reinforced thermoplastics as claimed in claim 1.   The carbon fiber reinforced thermoplastic according to any one of claims 1 to 6, wherein the carbon fiber web is 5 to 90% by mass and the thermoplastic resin is 10 to 95% by mass.   Electrical / electronic equipment parts, civil engineering / architectural parts, structural parts for automobiles / motorcycles, or aircraft parts using the carbon fiber reinforced thermoplastics according to claim 1. (I) Carbon fiber bundle mixing process, (II) Carbon fiber web making process, (III) Carbon fiber reinforced heat for producing carbon fiber reinforced thermoplastic by impregnating carbon fiber web with thermoplastic resin In the method for producing plastic plastics,
The carbon fiber web comprises at least a carbon fiber bundle (a) and a carbon fiber bundle (b), the carbon fiber bundle (a) has a fiber length of 5 to 15 mm, and the carbon fiber bundle (b) has a fiber length of less than 5 mm. A carbon fiber bundle in which the carbon fiber bundle (a) and the carbon fiber bundle (b) have a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.7 to 0.90. And a method for producing a carbon fiber reinforced thermoplastic comprising 30 to 90% by mass of the carbon fiber bundle (a) and 10 to 70% by mass of the carbon fiber bundle (b).   10. The carbon fiber reinforced thermoplastic according to claim 9, wherein the carbon fiber web has 20 to 70% of the number of fibers of the carbon fiber bundle (a) and 30 to 80% of the number of fibers of the carbon fiber bundle (b). Production method.   The method for producing a fiber-reinforced thermoplastic according to claim 9 or 10, wherein two or more different fiber lengths are combined in at least one of the carbon fiber bundle (a) and the carbon fiber bundle (b).   The method for producing a fiber-reinforced thermoplastic according to claim 9 or 10, wherein each of the carbon fiber bundle (a) and the carbon fiber bundle (b) comprises one type of fiber length. The manufacturing method of the fiber reinforced thermoplastics in any one of Claims 9-12 whose fabric weights of the said carbon fiber web are 10-500 g / m < ² >. The basis weight of the carbon fiber-reinforced thermoplastics is 100~5000g / ^{m 2,} the production method of carbon fiber reinforced thermoplastics as claimed in any one of claims 9-13.   The method for producing a carbon fiber-reinforced thermoplastic according to any one of claims 9 to 14, wherein the carbon fiber web is 5 to 90% by mass and the thermoplastic resin is 10 to 95% by mass.