WO2013191073A1

WO2013191073A1 - Carbon fiber mat and carbon fiber composite material including same

Info

Publication number: WO2013191073A1
Application number: PCT/JP2013/066300
Authority: WO
Inventors: 成瀬恵寛; 佐野高男; 関戸俊英; 橋本貴史; 三好且洋
Original assignee: 東レ株式会社
Priority date: 2012-06-18
Filing date: 2013-06-13
Publication date: 2013-12-27
Also published as: JPWO2013191073A1

Abstract

A carbon fiber mat characterized by being obtained by stacking a plurality of sheets of anisotropic discontinuous-fiber web which comprise carbon fibers having a fiber length of 5-100 mm and have a basis weight of 5-50 g/m² per sheet and uniting the stack so that the resultant laminate has quasi-isotropy; and a carbon fiber mat composite comprising such carbon fiber mats and a carbon fiber composite material obtained using such carbon fiber mats. With the carbon fiber mat and the carbon fiber composite material, high flowability can be exhibited during molding, and the molded articles therefrom have satisfactory mechanical properties and high isotropy of the mechanical properties in transverse and longitudinal directions.

Description

Carbon fiber mat and carbon fiber composite material comprising the same

The present invention relates to a carbon fiber mat and a carbon fiber composite material comprising the same, and in particular, a carbon fiber that can produce a molded article having excellent formability even in a complicated shape and having highly isotropic mechanical properties. The present invention relates to a mat and a carbon fiber composite material comprising the mat.

In order to manufacture a molded product of carbon fiber reinforced plastic, for example, a sheet-like carbon fiber composite material is used as a molding material, and the carbon fiber composite material is pressed into a predetermined shape under a predetermined temperature and pressure condition. A technique for forming (stamping) is known. In such molding, in particular, when the shape to be molded is a complicated shape, carbon as a molding material is formed so as to be molded in a desired carbon fiber reinforced form over all parts of the complex shape. High fluidity is required for fiber composite materials. When the fluidity of the carbon fiber composite material is low, not only good moldability cannot be obtained, but the mechanical properties of the molded product may be lowered, and the variation in mechanical properties may be increased.

As a conventional technique, Patent Document 1 discloses a carbon fiber composite material in which carbon fibers are opened to form a mat and impregnated with a thermoplastic resin. In the carbon fiber composite material of Patent Document 1, since the carbon fibers are opened, the surface quality is good and thinning is possible. However, since the opened carbon fibers are strongly entangled, the material at the time of press molding The fluidity of was low. Further, since the orientation of the carbon fibers has anisotropy, the ratio of the mechanical properties of the obtained molded product is large.

Patent Document 2 discloses a carbon fiber composite material in which a carbon fiber bundle is separated by a card spinning machine to form a two-dimensional pseudo-isotropic carbon fiber mat and impregnated with a thermosetting resin. ing. However, in the carbon fiber mat of Patent Document 2, although the carbon fibers are in a quasi-isotropic orientation state in the plane direction, the carbon fiber mat is oriented extremely randomly in the three-dimensional direction, so the thickness direction (z-axis direction) Due to the presence of a large number of carbon fibers oriented in the direction, the fluidity at the time of molding is low, and it is difficult to make the variation in mechanical properties of the molded product uniform.

JP 2011-178890 A JP 2008-174605 A

The problem of the present invention is that the carbon fiber composite material obtained from a conventional carbon fiber mat can exhibit high fluidity at the time of molding, the molded product has good mechanical properties, and the background of the mechanical properties. The object is to provide a carbon fiber mat and a carbon fiber composite material having a high isotropic ratio.

In the carbon fiber mat of the present invention, the carbon fibers in the discontinuous fiber web have anisotropy, and a plurality of the webs are stacked and bonded in a pseudo isotropic manner.

The pseudo isotropic lamination of the present invention is, for example, a web spun from a card machine or the like, and a plurality of the webs are laminated so as to have pseudo isotropic as a whole. The lamination method is not particularly limited. As a lamination method, the web may be a two-layer lamination of 0 ° / 90 °, a four-layer lamination of 0 ° / 90 ° / 45 ° / −45 °, or an eight-layer lamination in which it is symmetrical. It is also good. An example of the pseudo-isotropic laminate of the present invention is shown in FIG. FIG. 1 is a schematic view showing a state in which eight layers of anisotropic discontinuous fiber webs are laminated at (0 ° / 90 ° / 45 ° / −45 °) s (s indicates the target arrangement). In addition, for example, a plurality of webs stacked in layers such as a plurality of sheets in the same 0 ° direction and a plurality of sheets in the same 90 ° direction are stacked, and a plurality of layers are stacked in a pseudo isotropic manner as a whole. Is within the range. Needless to say, the webs oriented at the respective angles may be randomly combined and laminated so as to have pseudo-isotropic properties as a whole. Furthermore, the stacking angle is not particularly limited, and pseudo isotropic stacking may be performed by combining other angles such as 30 ° and 60 ° in addition to 0 °, 45 °, and 90 °. As a preferred laminate, a four-layer laminate of 0 ° / 90 ° / 45 ° / −45 ° is used as one unit, and more preferably an eight-layer laminate obtained by symmetrizing it is used as one unit. .

In the present invention, the carbon fiber mat laminated as described above can be used as one unit, and a plurality of them can be combined to form a carbon fiber mat composite. For example, a plurality of carbon fiber mats can be stacked to form a carbon fiber mat composite, or a plurality of sets can be arranged vertically and horizontally to form a carbon fiber mat composite. What is necessary is just to design and produce a carbon fiber mat composite so that it becomes the target thickness and shape when the carbon fiber mat of the present invention is used as a composite material, and there is no particular limitation as to the combination.

It is important that the fiber length of the carbon fiber of the present invention is in the range of 5 to 100 mm. By forming the anisotropic discontinuous fiber web with carbon fibers in such a fiber length range, it becomes possible to flow the carbon fiber composite material while maintaining a state in which the carbon fibers are well dispersed. Variation in the distribution of carbon fibers after molding (for example, variation in fiber volume content) is reduced, the mechanical properties of the molded product are stabilized, and the variation in mechanical properties is also reduced. In addition, by setting the fiber length within this range, it becomes easy to control the anisotropy of the carbon fiber when the web is made with a card machine or the like within the target range. A more preferable range of the fiber length is 5 to 50 mm, and a more preferable range is 10 to 30 mm.

Also, in the present invention, it is one of preferred embodiments that carbon fibers having different fiber lengths are mixed. By mixing carbon fibers with different fiber lengths, the orientation of carbon fibers with different fiber lengths when the mat of the present invention is produced by a card machine or the like changes, so that the anisotropy is controlled. Can do. One type of carbon fibers having different fiber lengths may be mixed, or two or more types may be mixed depending on the purpose.

It is important that the basis weight of the anisotropic discontinuous fiber web of the present invention is in the range of 5 to 50 g / m ² . In the present invention, an anisotropic discontinuous fiber web having a relatively small basis weight is characterized by being quasi-isotropically laminated, and has a different form from a conventional carbon fiber mat. Since the web having such a weight per unit area can be designed to have a small thickness when quasi-isotropically stacked, not only can the overall thickness be reduced even when a plurality of stacked minimum units are stacked. In addition, since a structure in which more discontinuous fibrous webs having anisotropy are laminated, a carbon fiber mat having more uniform isotropic properties can be obtained. Moreover, since the number of laminated webs can be increased when a material having a desired thickness is produced, it is possible to suppress variation in the local basis weight of the carbon fiber mat after the pseudo isotropic lamination. A more preferable range of the basis weight is 5 to 30 g / m ² , and a more preferable range is 10 to 20 g / m ² .

In the carbon fiber mat of the present invention, a plurality of anisotropic discontinuous fiber webs are stacked and joined. The term “bonded” means that the webs are joined together by some method, and the bonding method is preferably bonded, entangled, or stitched, and these may be combined singly or in combination depending on the purpose. preferable. When only a plurality of carbon fiber webs are laminated, each web is easily displaced and broken when handled, and the handling property is bad. When the resin is impregnated to make this a carbon fiber composite material In some cases, the layers of the webs are displaced from each other, making it difficult to mold, or the physical properties of the obtained carbon fiber composite material are low. On the other hand, since the carbon fiber webs are joined as in the present invention, the webs are integrated, so that the handleability is improved and the webs are not displaced during resin impregnation. The formability is good and the physical properties of the obtained carbon fiber composite material are good, which is preferable.

As a method for adhering the webs, an adhesive, an adhesive such as a tackifier, a thermal fusion film or a thermal fusion fiber may be used.

Further, as a method of entanglement between the webs, carbon fibers may be entangled by needle punch, water jet punch or the like, or various fibers such as synthetic fiber and glass fiber may be mixed and entangled by the above method. .

方法 As a method of stitching between webs, it is preferable to connect them with stitch yarns. Although it does not specifically limit as a kind of fiber of a stitch yarn, Polyamide fiber, polyester fiber, polyolefin fiber, polyaramid fiber, etc. are mentioned.

The background anisotropy of the carbon fibers in the anisotropic discontinuous fiber web of the present invention is preferably in the range of 1: 1.05 to 1: 5. Since the background anisotropy required by the measurement method described later is within this range, the orientation of carbon fibers in the carbon fiber mat when quasi-isotropically laminated becomes more random isotropic as a whole. The difference in physical properties between 0 ° and 90 ° in the mechanical properties of the carbon fiber composite material is reduced, and the mechanical properties of the molded product are stabilized and the variation thereof is reduced. A more preferable range of the background anisotropy is 1: 1.05 to 1: 2, and a more preferable range is 1: 1.05 to 1: 1.4.

The tensile strength of the carbon fiber of the present invention is preferably 3300 to 6500 MPa. By setting the tensile strength within this range, the mechanical properties when the carbon fiber mat of the present invention is made into a carbon fiber composite material can be further enhanced. Moreover, when the tensile strength is within this range, it is preferable because the carbon fibers are hardly cut when the mats of the present invention are joined. A more preferable range of the tensile strength is 4200 to 6500 MPa, and a further preferable range is 4800 to 6500 MPa.

The tensile elastic modulus of the carbon fiber of the present invention is preferably 200 to 600 GPa. By setting the tensile elastic modulus within this range, the mechanical properties when the carbon fiber mat of the present invention is made into a carbon fiber composite material can be further enhanced. Further, it is preferable that the tensile elastic modulus is within this range, since the carbon fibers are difficult to bend when the mat of the present invention is produced by a card machine or the like, and the anisotropy of the discontinuous fiber web can be increased. A more preferable range of the tensile modulus is 220 to 600 GPa, and a more preferable range is 280 to 600 GPa.

The carbon fiber of the present invention is preferably provided with a sizing agent. By imparting the sizing agent, it is possible to control the convergence of the carbon fibers, and it is possible to control the anisotropy of the web when producing the discontinuous fiber web. As the kind of the sizing agent, various modified products of polyethylene glycol, various modified products of glycerin and polyglycerin, various modified products of bisphenol A, and unsaturated polyesters as main components are preferable. These may be used alone or in combination according to the purpose. By using the above sizing agent, it is possible to appropriately adjust the bundling property and adhesion of the single yarn in the carbon fiber bundle, so that the anisotropy of the carbon fiber in the web can be controlled. Specifically, if a sizing agent with high carbon fiber bundling and adhesion is used, the carbon fibers are likely to be relatively bundled, and the carbon fibers are bundled when applied to a card machine or the like. Opening is difficult, and the carbon fibers in the web tend to face in one direction, so the anisotropy tends to increase. Among the above sizing agents, it is more preferable to use various modified products of bisphenol A as the sizing agent, and further to use various modified products of polyethylene glycol from the viewpoint of improving the adhesion and sizing properties of the carbon fibers. preferable.

Among the carbon fiber bundles forming the carbon fiber mat of the present invention, the number of carbon fibers constituting the carbon fiber bundle (1) having a weight of 90 or more carbon fibers constituting a carbon fiber bundle having a weight of 0.1 mg or more. Is preferably in the range of 90 to 1000 fibers / bundle, and the standard deviation σ of the number of carbon fibers constituting the carbon fiber bundle (1) is preferably in the range of 50 to 500.

The carbon fiber bundle in the carbon fiber mat has a number average x of the number of carbon fibers constituting the carbon fiber bundle (1) in which the number of carbon fibers constituting the carbon fiber bundle is 90 or more in the range of 90 to 1000. From the viewpoint of the appearance of the surface of the molded product when it is made into a carbon fiber composite material, the quantity average x of the number of carbon fibers constituting the bundle is 90 to 600. More preferably, it is in the range of 90 to 500. From the viewpoint of increasing the carbon fiber content when obtaining a carbon fiber composite material and obtaining a high elastic modulus, the number average x is more preferably in the range of 300 to 1,000, more preferably 500 to 1,000. is there. When the number average x of the carbon fiber bundles is less than 90, the number of entanglements between the fibers increases and the fluidity deteriorates. When the number exceeds 1000, the mechanical properties and the carbon fiber followability to fine parts such as ribs are deteriorated, and the variation in mechanical properties becomes large.

When the standard deviation σ of the number _xn of carbon fibers constituting the carbon fiber bundle (1) in the carbon fiber sheet is in the range of 50 ≦ σ ≦ 500, the carbon fiber bundle is dispersed in the carbon fiber sheet. By being distributed, it is possible to obtain a carbon fiber mat that can achieve both high fluidity and mechanical properties, has little variation in mechanical properties, and has excellent carbon fiber followability to fine parts. When the standard deviation σ is less than 50, the fluidity is deteriorated, and when the standard deviation σ is more than 500, the mechanical characteristics are deteriorated and the variation of the mechanical characteristics is increased. The standard deviation σ is more preferably in the range of 100 ≦ σ ≦ 350, still more preferably in the range of 150 ≦ σ ≦ 350, and still more preferably in the range of 150 ≦ σ ≦ 300.

In the present invention, it is preferable that at least one selected from synthetic fibers, natural fibers, glass fibers, and inorganic fibers is mixed with carbon fibers. By blending the above fibers together with carbon fibers, it is possible to improve yield, stabilize production, and reduce costs during web production. Further, it is possible to impart functionality and control mechanical properties when a carbon fiber composite material is used. When the mat of the present invention is made of a carbon fiber composite material, if the matrix resin is a thermoplastic resin, the synthetic fiber of the thermoplastic resin is integrated with the matrix resin when melt-molded. It is preferable since the physical properties of the material do not deteriorate. From the above viewpoint, it is more preferable that synthetic fibers are mixed.

The blend ratio of various fibers to carbon fibers is not particularly limited, but is preferably carbon fiber: mixed cotton fiber = 90%: 10% to 50%: 50%.

The carbon fiber mat of the present invention has a structure in which a plurality of anisotropic continuous webs are laminated, and it is preferable that all the layers have the same basis weight. Here, the same basis weight means that the basis weight of each layer falls within ± 10 g / m ² with the average value as the center value. It is preferable that the basis weights of the respective layers are the same because variations in mechanical properties are reduced when the carbon fiber composite material is formed by quasi-isotropic lamination. Further, it is preferable because the fluidity at the time of stamping molding is uniform in any direction.

Further, the carbon fiber mat of the present invention has a structure in which a plurality of anisotropic discontinuous fiber webs are laminated, and it is also a preferable aspect that each layer has a different basis weight. If each layer has a different basis weight, each web is laminated in a pseudo-isotropic manner to form a carbon fiber composite material, and a layer with a relatively large basis weight when stamped and formed has many carbon fiber composite materials. A layer that flows well in the direction in which the layer faces and a layer with a relatively small basis weight can be designed to be difficult to flow, which is preferable.

It is preferable that 70% or more of the carbon fibers in the anisotropic discontinuous fiber web of the present invention are opened to single fibers. The mechanical properties of the carbon fiber composite material can be greatly improved by opening the single fiber. Moreover, when the single fiber is opened, the surface appearance is improved when the carbon composite material is formed into a molded product. In the present invention, it is more preferable that 80% or more of the single fibers are opened, and more preferably 90% or more are opened.

Further, in the carbon fiber of the present invention, it is also a preferable aspect that 70% or more of the carbon fibers in the anisotropic discontinuous fiber web are in a bundle shape. The presence of single fibers in bundles can improve the fluidity when the carbon fiber composite material is molded by stamping or the like. In addition, since the single fibers are present in a bundle shape, the single fibers are concentrated so that the direction in which the single fibers are present can be easily directed, and the anisotropy in the mat can be controlled. In the present invention, 80% or more of the carbon fibers are more preferably bundled, and more preferably 90% or more are bundled. In order to control the state of the bundle of carbon fibers, as described above, it is preferable to appropriately select a sizing agent according to the purpose.

The carbon fiber mat of the present invention can be integrated with a matrix resin to form a carbon fiber composite material. Although it does not specifically limit as matrix resin, It is preferable to use a thermoplastic resin, a thermosetting resin, and resin which can be carbonized after baking, These may be used independently and it is also preferable to use in combination of multiple.

The thermoplastic resin used in the present invention includes polyamide resin, polyester resin, polyolefin resin, polyphenylene sulfide resin, polyacetal resin, polycarbonate resin, polyether sulfone resin, polyether ether ketone resin, polyphenylene ether resin, polysulfone resin, liquid crystal polymer. Etc. In consideration of moldability, physical properties, cost, etc., among the thermoplastic resins, it is preferable to use a polyamide resin, a polyolefin resin, a polyphenylene sulfide resin, or a polyether ether ketone resin.

Examples of the thermosetting resin used in the present invention include epoxy resins, phenol resins, amino resins, unsaturated polyester resins, urea resins, melamine resins, and the like. In consideration of moldability, physical properties, cost, and the like, it is preferable to use an epoxy resin, a phenol resin, or an unsaturated polyester resin among the thermosetting resins.

It is also preferable to use a resin that can be carbonized after firing as the resin used in the matrix resin of the present invention. Resin that can be carbonized after firing is a polymer that can be carbonized by firing after impregnation of the carbon fiber mat of the present invention, and there is no particular limitation on the resin as long as it can be carbonized. From the viewpoint of physical properties and ease of production as a c (carbon / carbon) composite, a phenol resin is preferable.

The carbon fiber composite material of the present invention can be various molded products. By forming into a flat plate by press molding, or pressing and flowing in a mold, a molded product having a complicated shape can be obtained. Moreover, it can also be set as a molded article by RTM shaping | molding, RIM shaping | molding, RFI shaping | molding, etc.

Although the carbon fiber composite material of the present invention can be formed as a single product, it is a carbon fiber composite based on a unidirectional material of carbon fiber, woven fabric, papermaking, SMC, airlaid nonwoven fabric, injection pellet, GMT, metal, etc. In combination with the material, a composite molded product of the carbon fiber composite material can be obtained.

Since the molded product of the present invention is superior in physical properties and moldability compared to conventional products, it can be applied to various products such as sports applications, automotive members, aircraft members, and general industrial applications.

As described above, according to the carbon fiber composite material of the present invention, the fluidity at the time of molding is excellent, and excellent moldability is obtained even when molding into a complicated shape, and the mechanical properties of the molded product are high. In addition, it is possible to provide an extremely useful carbon fiber composite material that can be used for press molding, and that can suppress variations in mechanical properties thereof. Therefore, by molding using this carbon fiber composite material, a molded product having desirable characteristics can be obtained easily and reliably.

It is a conceptual diagram which shows an example of the pseudo-isotropic lamination of this invention. It is explanatory drawing of the flow rate in this invention. It is a schematic block diagram of the carding apparatus used in the Example. It is a schematic block diagram of the airlaid apparatus used in the Example.

Hereinafter, the present invention will be described in detail mainly with reference to examples.
The carbon fiber mat according to the present invention is formed by stacking and joining a plurality of anisotropic discontinuous fiber webs and quasi-isotropically laminating the carbon fiber mat according to the present invention. The anisotropy of the carbon fibers inside plays a major role. In addition, in evaluating the performance of the carbon fiber composite material according to the present invention, the flow rate represented by the ratio of the area after pressurization to the area before pressurization when pressurized under a predetermined temperature and pressure condition. Plays a big role. Furthermore, as described above, in the carbon fiber composite material according to the present invention, the tensile strength, the tensile elastic modulus and the ratio thereof, and the bending strength, the bending elastic modulus and the ratio also play an important role. Therefore, these will be described first.

(1) Anisotropy of discontinuous fiber web The winding direction of discontinuous fiber webs obtained in Examples and Comparative Examples described later is 0 °, and the webs are all laminated in the 0 ° direction to form a carbon fiber mat. After further laminating a nylon resin meltblown nonwoven fabric (“CM1001”, relative viscosity of resin ηr = 2.3, manufactured by Toray Industries, Inc.) so that the volume ratio of the carbon fiber mat and the thermoplastic resin is 20:80, The whole is sandwiched between stainless plates, preheated at 240 ° C. for 90 seconds, and hot pressed at 240 ° C. for 180 seconds while applying a pressure of 2 MPa. Subsequently, it cools to 50 degreeC by a pressurization state, and the flat plate of a carbon fiber composite material with a thickness of 2.5 mm is obtained. Test pieces were cut out in the 0 ° direction (MD) and 90 direction (TD) from the obtained flat plate, and the bending strength and bending elastic modulus in the 0 ° direction and 90 ° direction were measured in accordance with ASTM D638. . The ratio of the elastic modulus in the 0 ° direction and 90 ° direction of the obtained elastic modulus (MD / TD) can be taken to determine the anisotropy of the anisotropic discontinuous fiber web.

(2) Flow test (fluidity in press molding (for example, stamping molding))
[When the matrix resin is polyamide]
As shown in FIG. 2, two carbon fiber composite materials 101 having dimensions of 100 × 100 mm × 2 mm are preheated to 260 ° C., then placed on a press panel 102 heated to 120 ° C., and heated at 20 MPa for 5 seconds. Pressed and flowed to form. The area A2 (mm ² ) after compression (after flow) of the carbon fiber reinforced plastic 103 after press molding and the area A1 (mm ² ) of the sheet before compression (before flow) are measured. (%) Was used for evaluation of fluidity.

[When the matrix resin is polypropylene (PP) resin]
In the same manner as described above, two carbon fiber composite materials having dimensions of 100 × 100 mm × 2 mm were preheated to 230 ° C., placed on a press plate heated to 80 ° C., and pressed at 20 MPa for 5 seconds. The area A2 (mm ² ) after compression and the area A1 (mm ² ) of the sheet before compression were measured, and A2 / A1 was defined as a flow rate (%).

(3) Tensile test Carbon fiber composite materials obtained in Examples and Comparative Examples were cut into test pieces and measured according to JIS K7164, and the tensile strength, tensile modulus, and ratio thereof were determined.

(4) Bending test The carbon fiber composite materials obtained in Examples and Comparative Examples were cut into test pieces and measured according to ASTM D 638 to obtain bending strength, bending elastic modulus and ratio thereof.

(5) Carbon fiber volume content (Vf) in the carbon fiber composite material
About 2 g of a sample was cut out from the carbon fiber composite material press-molded product after the above flow test, and its mass was measured. Thereafter, the sample was heated in an electric furnace heated to 500 ° C. for 1 hour to burn off organic substances such as a matrix resin. After cooling to room temperature, the mass of the remaining carbon fiber was measured. The ratio of the mass of the carbon fiber to the mass of the sample before burning the organic substance such as the matrix resin was measured, and the respective volumes were determined from the density of the matrix resin and the density of the carbon fiber, and the volume content of the carbon fiber was obtained.

(6) Measuring method of carbon fiber bundle A sample of 100 mm × 100 mm was cut out from the carbon fiber composite material, and then the sample was heated in an electric furnace heated to 500 ° C. for about 1 hour to burn off organic substances such as matrix resin. It was. After measuring the mass of the carbon fiber aggregate remaining after cooling to room temperature, all the carbon fiber bundles were extracted from the carbon fiber aggregate with tweezers. For all the extracted carbon fiber bundles, the weight M _n and the length L _n of each carbon fiber bundle are measured using a balance capable of measuring up to 1/10000 g. After the measurement, M _n / L _n , M _n / (L _n × D) and the number of single carbon fiber yarns constituting the carbon fiber bundle x _n = M _n / (L _n × F) are calculated for each bundle. To do. Here, D is the carbon fiber diameter, F is the single yarn fineness of the carbon fiber, and _xn is the number of constituent single yarns of the carbon fiber bundle.

The carbon fiber bundle constituted a single yarn number x _n is more than 90 pieces of carbon fiber bundle and carbon fiber bundle (1), the total weight as M _1, a bundle total number as N, measured. Further, the carbon fiber bundle under construction single yarn number x _n is 90 present a fiber bundle (2), the total weight of the carbon fiber bundle (2) as M _2, is measured. The fiber bundles opened to such an extent that they cannot be extracted with tweezers were collectively measured and finally weighed. Further, when the fiber length is short and it becomes difficult to measure the weight, the fiber length is classified at intervals of about 0.2 mm, the weight is measured for a bundle of a plurality of classified bundles, and an average value may be used. . After all classification and measurement, the quantity average x = Σ {M _n / (L _n × F)} / N of the number of carbon fibers constituting the bundle with respect to the carbon fiber bundle (1), the carbon constituting the carbon fiber bundle carbon fibers constituting the standard deviation σ = {1 / n × Σ (x n -x) 2} 1/2 is calculated, and number-average x and the carbon fiber bundle of the carbon fiber number constituting the bundle of fibers number _{x n} The standard deviation σ of the number _xn is obtained. N is the total number of bundles of carbon fiber bundles (1). Moreover, the ratio of the carbon fiber bundle (1) to the total weight of the carbon fiber bundle is obtained by the following mathematical formula.

M ₁ / (M ₁ + M ₂ ) × 100

Hereinafter, examples and comparative examples will be described. First, the carbon fiber bundles (A) to (E) used in Examples and Comparative Examples and carding performed using them will be described.

First, carding will be explained. As illustrated in FIG. 3, a carding apparatus 1 for carding a carbon fiber bundle includes a cylinder roll 2, a take-in roll 3 provided on the upstream side in the vicinity of the outer peripheral surface, a take-in roll 3, Is provided near the outer peripheral surface of the cylinder roll 2 between the take-in roll 3 and the doffer roll 4 between the doffer roll 4 provided near the outer peripheral surface of the cylinder roll 2 on the opposite downstream side. A plurality of worker rolls 5, a stripper roll 6 provided in the vicinity of the worker roll 5, a feed roll 7 and a belt conveyor 8 provided in the vicinity of the take-in roll 3 are mainly configured.

A carbon fiber bundle 9 cut to a predetermined length is supplied to the belt conveyor 8, and the carbon fiber bundle 9 is introduced onto the outer peripheral surface of the cylinder roll 2 through the outer peripheral surface of the feed roll and then the outer peripheral surface of the take-in roll 3. The Up to this stage, the carbon fiber bundles are solved to some extent to form an aggregate of carbon-like carbon fiber bundles (carbon fiber aggregate). A part of the aggregate of cotton-like carbon fiber bundles introduced on the outer peripheral surface of the cylinder roll 2 is wound around the outer peripheral surface of the worker roll 5, and this carbon fiber is peeled off by the stripper roll 6 and again the cylinder roll. 2 is returned to the outer peripheral surface. A large number of needles and protrusions are present on the outer peripheral surface of each of the feed roll 7, the take-up roll 3, the cylinder roll 2, the worker roll 5 and the stripper roll 6, and the carbon fiber is The bundle is opened to a predetermined bundle by the action of the needle and oriented to some extent. Through this process, a predetermined carbon fiber bundle is opened and moved to the outer peripheral surface of the doffer roll 4 as a sheet-like web 10 which is one form of a carbon fiber aggregate, whereby a desired sheet-like web 10 is obtained. Is obtained.

Next, airlaid will be described. Airlaid is a method for producing a nonwoven sheet of short fibers. General airlaid methods include the Honshu Paper Manufacturing Method, Cloyer Method, Dunweb Method, J & J Method, KC Method, Scott Method, etc. reference).

For example, as shown in FIG. 5, the airlaid device 11 includes a cylindrical drum 12 having a fine hole that rotates in reverse to each other and a pin cylinder 13 installed in each drum 12, and a carbon fiber together with a large amount of air. A single bundle or a carbon fiber bundle and a thermoplastic resin fiber are blown to the drum 12, opened by the pin cylinder 13 in the drum 12, discharged from the pores, and dropped onto the wire 14 that travels thereunder. Here, air used for air blowing is sucked into a suction box 15 installed under the wire 14, and the opened carbon fiber bundle alone or the opened carbon fiber bundle and the thermoplastic resin fiber remains on the wire 4. To form a carbon fiber sheet.

Next, the carbon fiber bundles (A) to (E) used in the examples and comparative examples will be described.

[Carbon fiber bundle (A)]
Carbon fiber in which 1.0% by weight of a sizing agent mainly composed of bisphenol A ethylene oxide adduct is attached to a carbon fiber bundle with a continuous carbon fiber bundle having a fiber diameter of 7 μm, a tensile modulus of 230 GPa, and a filament number of 12,000. A bundle (A) was obtained.

[Carbon fiber bundle (B)]
Bisphenol A type ethylene oxide maleic acid as unsaturated ester resin with 40% component of bisphenol A type epoxy resin (molecular weight = 370) for continuous carbon fiber bundle with fiber diameter 7μm, tensile modulus 230GPa, filament number 12000 A carbon fiber bundle (B) was obtained in which 1.0% by weight of a sizing agent mainly composed of 40% ester (molecular weight = 2500) and 20% emulsifier was attached to the carbon fiber bundle.

[Carbon fiber bundle (C)]
A 100% polyethylene glycol diglycidyl ether component (molecular weight = 670) aqueous sizing agent is attached to the carbon fiber bundle by 1.0% by weight on a continuous carbon fiber bundle having a fiber diameter of 7 μm, a tensile modulus of 230 GPa, and a filament number of 12,000. A carbon fiber bundle (C) was obtained.

[Carbon fiber bundle (D)]
A carbon fiber bundle (D) was obtained without applying a sizing agent to a continuous carbon fiber bundle having a fiber diameter of 7 μm, a tensile modulus of 230 GPa, and a filament number of 12,000.

[Carbon fiber bundle (E)]

A continuous sizing carbon fiber bundle having a fiber diameter of 7 μm, a tensile elastic modulus of 230 GPa, and a filament number of 24,000, a solvent-based sizing agent obtained by diluting glycerol triglycidyl ether with dimethylformamide (hereinafter abbreviated as DMF) is added to the carbon fiber bundle. A carbon fiber bundle (E) to which 5% by weight was adhered was obtained.

Example 1
The carbon fiber bundle (A) was cut to a fiber length of 50 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound to form an anisotropic discontinuous fiber web having a basis weight of 8.5 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 2.27. The web was wound at 0 °, and eight carbon fiber webs were laminated so as to be (0 ° / + 45 / −45 ° / 90 °) s. This was stacked as 12 units for one unit, and joined with nylon stitch yarn to obtain a quasi-isotropic laminated carbon fiber mat. A nylon resin meltblown nonwoven fabric (“CM1001”, relative viscosity of resin ηr = 2.3, manufactured by Toray Industries, Inc.) was further laminated so that the volume ratio of the obtained carbon fiber mat to the thermoplastic resin was 20:80. Thereafter, the whole was sandwiched between stainless plates, preheated at 240 ° C. for 90 seconds, and hot pressed at 240 ° C. for 180 seconds while applying a pressure of 2 MPa. Subsequently, it cooled to 50 degreeC by the pressurization state, and obtained the flat plate of the carbon fiber composite material of thickness 2.5mm. When the flow test of the obtained flat plate was carried out, the fluidity was 220% and the fluidity was excellent. Further, when the tensile test and the bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.09, the flexural modulus ratio was 1.14, and the mechanical properties. Was highly isotropic.

Further, the number average x of the number of carbon fibers constituting the bundle was 160, and the standard deviation σ was 61.

(Example 2)
The carbon fiber bundle (A) is cut to a fiber length of 50 mm, put into a carding apparatus as shown in FIG. 3, and cross-wrapped so that 13 layers of 8.5 g / m ² of web are overlapped. The resulting sheet was wound up to form an anisotropic discontinuous fiber web. The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 2.27. The web winding direction is set to 0 °, and the carbon fiber web is laminated so as to be 8 steps (0 ° / + 45 / −45 ° / 90 °) s, and bonded with nylon stitch yarns, and isotropically laminated. A carbon fiber mat was obtained. The obtained carbon fiber mat was impregnated with a thermoplastic resin by hot pressing in the same manner as in Example 1 to obtain a carbon fiber composite material flat plate having a thickness of 2.5 mm. When the flow test of the obtained flat plate was carried out, the fluidity was 215% and the fluidity was excellent. Further, when the tensile test and bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.10, the flexural modulus ratio was 1.24, and the mechanical properties were Was highly isotropic.

Further, the number average x of the number of carbon fibers constituting the bundle was 150, and the standard deviation σ was 59.

(Example 3)
The carbon fiber bundle (A) was cut into a fiber length of 15 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound up to form an anisotropic discontinuous fiber web having a basis weight of 17 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.53. The web was wound in a winding direction of 0 °, and two carbon fiber webs were laminated so as to be (0 ° / 90 °) s. This was stacked as a unit for 24 stages, and bonded with nylon stitch yarns to obtain a pseudo isotropic laminated carbon fiber mat. The obtained carbon fiber mat was impregnated with a thermoplastic resin by hot pressing in the same manner as in Example 1 to obtain a carbon fiber composite material flat plate having a thickness of 2.5 mm. When the flow test of the obtained flat plate was carried out, the fluidity was 250%, which was excellent in fluidity. Further, when the tensile test and the bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.08, the flexural modulus ratio was 1.53, and the mechanical properties. Was highly isotropic.

The number average x of the number of carbon fibers constituting the bundle was 168, and the standard deviation σ was 62.

(Example 4)
The carbon fiber bundle (B) was cut into a fiber length of 25 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound up to form an anisotropic discontinuous fiber web having a basis weight of 26 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.05. The web was wound at 0 °, and four carbon fiber webs were laminated so as to be (0 ° / + 45 / −45 ° / 90 °) s. This was stacked as a unit in five stages, and carbon fibers mated with a needle punch and joined to obtain a carbon fiber mat that was quasi-isotropically laminated. After further laminating a nylon resin film (“CM2001”, relative viscosity of resin ηr = 2.3, manufactured by Toray Industries, Inc.) so that the volume ratio of the obtained carbon fiber mat and the thermoplastic resin is 30:70 The whole was sandwiched between stainless steel plates, preheated at 260 ° C. for 90 seconds, and hot pressed at 260 ° C. for 180 seconds while applying a pressure of 3.0 MPa. Subsequently, it cooled to 50 degreeC by the pressurization state, and obtained the flat plate of the carbon fiber composite material of thickness 2.5mm. When the flow test of the obtained flat plate was carried out, the fluidity was 230% and the fluidity was excellent. Further, when the tensile test and the bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.18, the flexural modulus ratio was 1.05, and the mechanical properties. Was highly isotropic.

Further, the number average x of the number of carbon fibers constituting the bundle was 324, and the standard deviation σ was 240.

(Example 5)
The carbon fiber bundle (C) was cut into a fiber length of 10 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound to form an anisotropic discontinuous fiber web having a basis weight of 8.5 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.67. The web was wound at 0 °, and the carbon fiber web was laminated so that eight carbon fiber webs were (0 ° / + 45 / −45 ° / 90 °) s. This was stacked as 12 units for one unit, and bonded by adhesion with a thermoplastic tackifier to obtain a quasi-isotropic laminated carbon fiber mat. After further laminating a nylon resin film (“CM2001”, relative viscosity of resin ηr = 2.3, manufactured by Toray Industries, Inc.) such that the volume ratio of the obtained carbon fiber mat and the thermoplastic resin is 25:75. The whole was sandwiched between stainless steel plates, preheated at 260 ° C. for 90 seconds, and hot pressed at 260 ° C. for 180 seconds while applying a pressure of 3.0 MPa. Subsequently, it cooled to 50 degreeC by the pressurization state, and obtained the flat plate of the carbon fiber composite material of thickness 2.5mm. When the flow test of the obtained flat plate was carried out, the fluidity was 243% and the fluidity was excellent. Further, when the tensile test and the bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.06, the flexural modulus ratio was 1.19, and the mechanical properties. Was highly isotropic.

The number average x of the number of carbon fibers constituting the bundle was 372, and the standard deviation σ was 190.

(Example 6)
The carbon fiber bundle (D) was cut into a fiber length of 50 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound to form an anisotropic discontinuous fiber web having a basis weight of 8.5 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 2.98. The web was wound at 0 °, and eight carbon fiber webs were laminated so as to be (0 ° / + 45 / −45 ° / 90 °) s. This was stacked as 12 units for one unit, and joined with a polypropylene stitch yarn to obtain a pseudo isotropic laminated carbon fiber mat. Polypropylene resin melt blown nonwoven fabric (“J1709QG”, MFR (melt flow rate) = 55 g / 10 min, manufactured by Prime Polymer Co., Ltd.) was further added so that the volume ratio of the obtained carbon fiber mat to the thermoplastic resin was 25:75. After the lamination, the whole was sandwiched between stainless plates, preheated at 240 ° C. for 90 seconds, and hot pressed at 240 ° C. for 180 seconds while applying a pressure of 2.0 MPa. Subsequently, it cooled to 50 degreeC by the pressurization state, and obtained the flat plate of the carbon fiber composite material of thickness 2.5mm. When the flow test of the obtained flat plate was carried out, the fluidity was 195% and the fluidity was excellent. Further, when the tensile test and the bending test of the flat plate were carried out, the results shown in Table 1 were obtained. The tensile modulus ratio was 1.12 and the flexural modulus ratio was 1.17. Was highly isotropic.

Further, the number average x of the number of carbon fibers constituting the bundle was 510, and the standard deviation σ was 354.

(Example 7)
The carbon fiber bundle (E) was cut to a fiber length of 15 mm, and the cut carbon fiber bundle and polyamide (nylon 6) short fibers (long fibers having a single fiber fineness of 1.7 dtex and a cut length of 5 mm) were used in a mass ratio of 90. : 10 and the mixture was put into an airlaid apparatus as shown in FIG. 4 to form a sheet-like carbon fiber aggregate having a basis weight of 10 g / m ² made of carbon fiber and nylon 6 fiber. The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.25. The winding direction of the sheet-like carbon fiber aggregate was 0 °, and 12 carbon fiber aggregates were laminated so as to be (0 ° / 90 ° / 0 ° / 90 ° / 0 ° / 90 °) s. . The carbon fiber mat was obtained by stacking 10 units as a unit, and joining the polyamide (nylon 6) short fibers in the web by heat-sealing at 220 ° C. to form a pseudo isotropic laminate. A nylon 610 resin film (“CM2001” manufactured by Toray Industries, Inc.) was further laminated so that the volume ratio of the obtained carbon fiber mat and the thermoplastic resin was 25:75, and the whole was sandwiched between stainless steel plates at 240 ° C. Was pre-heated for 90 seconds and then hot pressed at 240 ° C. for 180 seconds while applying a pressure of 1.0 MPa. Subsequently, it cooled to 50 degreeC in the pressurization state, and obtained the flat plate of the carbon fiber composite material of thickness 2mm. When the flow test of the obtained flat plate was carried out, the fluidity was 295% and the fluidity was excellent. Further, when the tensile test and the bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.12, the flexural modulus ratio was 1.21, and the mechanical properties. Was highly isotropic.

Further, the number average x of the number of carbon fibers constituting the bundle was 375, and the standard deviation σ was 295.

(Example 8)
A sheet-like carbon fiber aggregate was formed in the same manner as in Example 7 except that the carbon fiber bundle (E) was cut to a fiber length of 25 mm. The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.32. Further, in the same manner as in Example 7, a carbon fiber composite material flat plate having a thickness of 2 mm was obtained from the carbon fiber mat. When the flow test of the obtained flat plate was carried out, the fluidity was 276% and the fluidity was excellent. Moreover, when the tensile test and bending test of the flat plate were carried out, the results shown in Table 1 were obtained, the tensile modulus ratio was 1.25, the flexural modulus ratio was 1.29, and the mechanical properties were Was highly isotropic.

The number average x of the number of carbon fibers constituting the bundle was 420, and the standard deviation σ was 365.

(Comparative Example 1)
The carbon fiber bundle (A) was cut to a fiber length of 50 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound to form an anisotropic discontinuous fiber web having a basis weight of 8.5 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 2.27. The winding direction of this web was set to 0 °, and eight carbon fiber webs were stacked and stacked only in the 0 ° direction. This was stacked as 12 units for one unit and joined with nylon stitch yarn to obtain a carbon fiber mat. The obtained carbon fiber mat was impregnated with a thermoplastic resin by a press in the same manner as in Example 1 to obtain a carbon fiber composite material flat plate having a thickness of 2.5 mm. When the obtained flat plate was subjected to a flow test, the fluidity was 165%, which was inferior in fluidity. As shown in Table 1, the tensile modulus ratio was 1.89, and the flexural modulus ratio was 2.15. In other words, the mechanical properties were less isotropic than the examples.

Further, the number average x of the number of carbon fibers constituting the bundle was 162, and the standard deviation σ was 63.

(Comparative Example 2)
The carbon fiber bundle (B) was cut into a fiber length of 25 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound to form an anisotropic discontinuous fiber web having a basis weight of 8.5 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.05. The web was wound at 0 °, and eight carbon fiber webs were laminated so as to be (0 ° / + 45 / −45 ° / 90 °) s. By simply stacking 12 units as one unit, a carbon fiber mat that was quasi-isotropically laminated without joining was obtained. The obtained carbon fiber mat was impregnated with a thermoplastic resin by a press in the same manner as in Example 5 to obtain a carbon fiber composite material flat plate having a thickness of 2.5 mm. When the flow test of the obtained flat plate was carried out, the fluidity was 220%, which was excellent in fluidity. However, the web was not bonded, so the web was displaced when it was made into a carbon fiber composite material with a press. As shown in Table 1, the tensile modulus ratio is 1.41, the bending modulus ratio is 1.31, and the mechanical properties areotropic. However, the result was lower than that of the example.

Further, the number average x of the number of carbon fibers constituting the bundle was 320, and the standard deviation σ was 235.

(Comparative Example 3)
The carbon fiber bundle (A) was cut into a fiber length of 15 mm and put into a carding apparatus as shown in FIG. The sheet that came out was directly wound to form an anisotropic discontinuous fiber web having a basis weight of 8.5 g / m ² . The background anisotropy of the carbon fibers in this anisotropic discontinuous fiber web was 1: 1.53. The web was wound in a winding direction of 0 °, and three carbon fiber webs were laminated so as to be 0 ° / + 45/90 °. This was stacked as 25 units as a unit and joined with nylon stitch yarns to obtain a carbon fiber mat. A carbon fiber composite material flat plate having a thickness of 2.5 mm was obtained under the same molding conditions as in Example 1 so that the volume ratio of the obtained carbon fiber mat to the thermoplastic resin was 30:70. When the flow test of the obtained flat plate was carried out, the fluidity was 170%, which was inferior in fluidity. Moreover, when the tensile test and bending test of the flat plate were carried out, as shown in Table 1, the tensile modulus ratio was 1.16 and the flexural modulus ratio was 1.73. As a result, the mechanical properties were less isotropic than the examples.

The number average x of the number of carbon fibers constituting the bundle was 170, and the standard deviation σ was 65.

The present invention is particularly suitable for applications in which molding into a relatively complicated shape is performed by press molding of a carbon fiber composite material, such as automobile members, aircraft members, industrial members, and the like.

DESCRIPTION OF SYMBOLS 1 Carding apparatus 2 Cylinder roll 3 Take-in roll 4 Doffer roll 5 Worker roll 6 Stripper roll 7 Feed roll 8 Belt conveyor 9 Discontinuous carbon fiber 10 Sheet-like anisotropic discontinuous fiber web 11 Airlaid apparatus 12 Drum 13 Pin cylinder 14 Wire 15 Suction box 101 Carbon fiber composite material 102 before flowing Press machine 103 Carbon fiber reinforced plastic D1 after press molding Direction of carbon fiber anisotropy D2 Sheet traveling direction

Claims

A plurality of anisotropic discontinuous fiber webs made of carbon fibers having a fiber length of 5 to 100 mm and having a basis weight of 5 to 50 g / m 2 are stacked and bonded so as to have pseudo-isotropic properties. A carbon fiber mat characterized by comprising.
The carbon fiber mat according to claim 1, wherein the anisotropic discontinuous fiber webs are bonded to each other by bonding, entanglement, or stitching.
The carbon fiber mat according to claim 1 or 2, wherein the background anisotropy of the carbon fibers in the anisotropic discontinuous fiber web is 1: 1.05 to 1: 5.
The carbon fiber sizing agent is mainly composed of at least one selected from various modified products of polyethylene glycol, various modified products of polyglycerin, various modified products of bisphenol A, and unsaturated polyesters. The carbon fiber mat according to any one of the above.
A carbon fiber mat formed by a carbon fiber bundle (1) composed of 90 or more carbon fibers and a carbon fiber bundle (2) composed of less than 90 carbon fibers, the carbon fiber bundle (1) The number average x of the number of carbon fibers constituting the bundle is in the range of 90 to 1000 pieces / bundle, and the standard deviation σ of the number of carbon fibers constituting the carbon fiber bundle (1) is 50 to 500. The carbon fiber mat according to any one of claims 1 to 4, which is in the range of
A carbon fiber mat composite comprising a combination of a plurality of carbon fiber mats according to any one of claims 1 to 5.
A carbon fiber composite material comprising the carbon fiber mat according to any one of claims 1 to 5 and a matrix resin.