JP6976767B2 - Carbon short fiber wet non-woven fabric and carbon short fiber reinforced resin composition - Google Patents

Description

The present invention relates to a carbon short fiber wet non-woven fabric.

Carbon fiber is lighter than iron and has excellent mechanical properties of high strength. Therefore, carbon fiber composite materials are used in a wide range of fields such as aircraft, automobiles, tennis rackets, fishing rods, and blades for wind power generation, and their applications are expected to expand in the future.

Currently, the carbon fibers are mainly PAN-based carbon fibers obtained by carbonizing and graphitizing polyacrylonitrile, and pitch-based carbon fibers obtained by melt-spinning tar-pitch liquefied coal and then carbonizing and graphitizing. Carbon fiber is used. The carbon fibers thus produced were processed as woven fabrics or arranged in one direction, and then a material called carbon fiber prepreg impregnated with an uncured resin was cut to fit the mold of the target molded product. It is often used as a carbon fiber reinforced resin (hereinafter abbreviated as "CFRP") obtained by curing the resin later. Alternatively, when carbon fiber obtained by recycling CFRP waste material is used, it cannot be processed as a woven fabric because the carbon fiber is shortened to carbon short fiber in the recycling process, so that it is processed as a non-woven fabric. Is common.

As a method of forming a carbon short fiber non-woven fabric into a sheet, the carbon short fiber and the water-swelling fibrillated fiber are dispersed in water to prepare a papermaking slurry, and the fibers are entangled to obtain a wet carbon short fiber. A method for producing a non-woven fabric is disclosed. Examples of the water-swelled fibrillated fiber include a fibrillated para-type aromatic polyamide fiber and a fibrillated acrylic fiber (see Patent Document 1). However, in this method, when the carbon short fiber wet non-woven fabric is processed into CFRP, the permeability of the resin into the carbon short fiber wet non-woven fabric and the uniform resin in the carbon short fiber non-woven fabric are obtained in steps such as cutting and compression. The point of permeation is not taken into consideration, and trouble may occur during CFRP processing. When a carbon short fiber non-woven fabric that is difficult for the resin to permeate is used, it may take time for the resin to permeate into the carbon short fibers, and the permeation amount of the resin may differ between the front and back sides. In addition, when a carbon short fiber non-woven fabric that is difficult to penetrate uniformly with resin is used, there are some parts in the carbon short fiber non-woven fabric where the resin is abundant and some parts where the resin is not so much, and there is a difference in quality when compressed and heat-processed. It may come out.

Further, as another method for producing the carbon short fiber wet non-woven fabric, in the method for producing the carbon short fiber wet non-woven fabric composed of 75% by mass to 97% by mass of carbon short fiber and 25% by mass to 3% by mass of cellulose, nitrogen-containing organic is used. Add 10% by mass or less of the aqueous dispersion aid containing a solvent and carbon short fibers to a predetermined amount of water and stir, and further reduce the slurry solid content concentration to 0.05% by mass or less with water. A method of wet paper making after undergoing a step of diluting and circulating is shown (see Patent Document 2). However, the carbon short fiber wet non-woven fabric of Patent Document 2 is a non-woven fabric having gas permeability and conductivity and is not a non-woven fabric used for CFRP. Therefore, when the carbon short fiber wet non-woven fabric is processed into CFRP, it is cut and compressed. In the above steps, the point of facilitating the permeation of the resin or the point of uniformly permeating the resin is not taken into consideration, and it is conceivable that a problem may occur when the resin is processed as CFRP.

International Publication No. 2014/021366 Pamphlet Japanese Unexamined Patent Publication No. 2004-353124

An object of the present invention is to provide a carbon short fiber wet non-woven fabric in which a resin permeates uniformly in a short time when processed into CFRP.

As a result of conducting research to solve this problem, the present inventors have found the following means.

(1) The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and 5 bundles composed of 10 or more carbon short fibers / cm ² has more than the average number of fibers short carbon fibers constituting the strapping is Ri der 500 / cohesion less, short carbon fibers wet-laid nonwoven fabric which is characterized that you blended cellulosic fibers.
(2) The carbon short fiber wet non-woven fabric according to (1) above, wherein the average fiber length of the carbon short fibers is 1 mm or more.
(3) A carbon short fiber reinforced resin composition comprising the carbon short fiber wet non-woven fabric according to the above (1) or (2) and a resin composited with the non-woven fabric.

According to the present invention, it is possible to obtain a carbon short fiber wet non-woven fabric in which a resin permeates uniformly in a short time when it is processed into CFRP.

It is an electron micrograph of a carbon short fiber wet non-woven fabric which is composed of 10 or more carbon short fibers and does not have a bond. It is an electron micrograph of a carbon short fiber wet non-woven fabric in which the average number of carbon short fibers constituting the bundling is 500 fibers / bundling or less. It is an electron micrograph of a carbon short fiber wet non-woven fabric in which the average number of carbon short fibers constituting the bundling is 500 fibers / more than bundling.

In a non-woven fabric containing carbon short fibers, it may be difficult to uniformly permeate the resin when processing into CFRP. The cause is that carbon short fibers have high strength and poor flexibility, and thus form a complicated three-dimensional structure when processed into a non-woven fabric, resulting in low density. That is, since the number of voids in the non-woven fabric increases, the resin may permeate only on the coated surface when the high-viscosity resin is applied, and the resin may not permeate to the non-coated surface of the non-woven fabric on the opposite surface. If hot press processing is performed with the resin concentration on the front and back, a resin concentration gradient may occur even in the completed CFRP, and the quality may be uneven. There is also a method of uniformly infiltrating the resin by diluting the resin with an organic solvent and applying it, and then evaporating the organic solvent. It should be avoided as much as possible. From these facts, a carbon short fiber wet non-woven fabric in which a resin easily penetrates is necessary to obtain stable quality of CFRP at low cost.

1 to 3 are electron micrographs of a carbon short fiber wet non-woven fabric. Carbon short fibers have very high strength and poor flexibility. Therefore, as shown in FIG. 1, the carbon short fiber wet non-woven fabric produced by papermaking carbon short fibers having little or no binding tends to have a very low density and uniformly permeates the resin. It can be difficult to get it done. Therefore, by adjusting the conditions for dispersing the carbon short fibers during papermaking, as shown in FIG. 2, the average number of carbon short fibers constituting the binding is 500 fibers / binding or less. A wet non-woven fabric can be obtained. Since the binding is a state in which the carbon short fibers are tightly packed, the carbon short fiber wet non-woven fabric in which the binding is present tends to have a relatively high density. This facilitates uniform penetration of the resin. However, as shown in FIG. 3, in the carbon short fiber wet non-woven fabric in which the fibers are hardly dispersed and the average number of carbon short fibers constituting the binding is 500 / more than the binding, the resin is contained up to the inside of the binding. Since it does not penetrate and the strength inside the binding becomes very weak, there may be unevenness in the strength after CFRP processing, which may be a drawback. Reference numeral 1 in FIG. 2 is carbon short fiber binding (the number of carbon short fibers constituting the binding is 500 fibers / binding or less), and reference numeral 2 in FIG. 3 is carbon short fiber binding (carbon short fibers constituting the binding). The number of fibers is 500 / more than binding).

As the carbon short fibers, carbon short fibers manufactured by any manufacturing method such as PAN type and pitch type can be used. Further, there is no problem with new and unused carbon short fibers or carbon short fibers obtained by recycling the discarded carbon fibers. Considering the cost required to obtain carbon short fibers, carbon short fibers obtained by recycling are more preferable.

The average fiber length of the carbon short fibers is preferably 1 mm or more, more preferably 3 mm or more, still more preferably 5 mm or more. The longer the average fiber length of the carbon short fibers, the easier it is for the carbon short fibers to form a bundle, and the uniformity of the resin tends to increase. The maximum value of the average fiber length is not particularly limited, but if the average fiber length is too long, the operability may become unstable when the sheet is made by the papermaking method, so that it is preferably less than 100 mm.

Here, the average fiber length of the carbon short fibers is obtained by the following method. First, 20 short carbon fibers are randomly collected and their fiber lengths are measured. After that, the average fiber length of the carbon short fibers is calculated by the following calculation method.

Average fiber length = {(fiber length (mm) of carbon short fiber 1) + (fiber length (mm) of carbon short fiber 2) + (fiber length (mm) of carbon short fiber 3) + ... (carbon short fiber 20) Fiber length (mm)} / 20

The average number of carbon short fibers constituting the binding is preferably 500 fibers / binding or less, and more preferably 300 fibers / binding or less. Since the average number of fibers is intended for "binding composed of 10 or more carbon short fibers", the preferable lower limit of the average number of fibers is 10 fibers / binding. If the average number of carbon short fibers constituting the bundling is 500 / more than the bundling, the resin does not penetrate into the bundling and the strength inside the bundling becomes very weak, which may be a defect after CFRP processing. be.

In the present invention, the carbon short fiber wet non-woven fabric has a binding composed of 10 or more carbon short fibers of 5 pieces / cm ² or more, and ^{more preferably 10 pieces / cm 2} or more. When the number of bundles composed of 10 or more carbon short fibers ^{is less than 5 pieces / cm 2} , the density of the carbon short fiber wet paper machine non-woven fabric becomes low, and it may be difficult to uniformly permeate the resin.

Since it is extremely difficult to visually measure the average number of carbon short fibers constituting the bundling, in the present invention, the average number of carbon short fibers constituting the bundling is obtained by the following method.

First, a short carbon fiber is photographed with an electron microscope (SEM) to measure the cross-sectional area of one fiber. Next, 100 bundles composed of 10 or more carbon short fibers are randomly collected from the carbon short fiber wet non-woven fabric, and the total mass of the 100 bundles is measured. After that, the total number of carbon short fibers of 100 bound is calculated by the following calculation method, and the average value is obtained to calculate the average number of carbon short fibers [unit: fiber / bound] constituting the bundle. ..

(Cross-sectional area of carbon short fibers) x (average fiber length of carbon short fibers) x (carbon short fiber density) = (mass per carbon short fiber)

(Mass of 100 bound fibers) ÷ (Mass per carbon short fiber) = (Total number of carbon short fibers of 100 bound)

(Total number of carbon short fibers of 100 bound) ÷ 100 = (Average number of carbon short fibers constituting the bundle)

In the carbon short fiber wet non-woven fabric of the present invention, cellulose fibers can be used as long as the performance is not impaired. Types of cellulose fibers include wood pulp such as coniferous tree pulp and broadleaf tree pulp; woody materials such as straw pulp, bamboo pulp, linter pulp, and kenaf pulp, natural pulp fibers such as herbaceous pulp, and rayon, cupra, and lyocell. Examples include regenerated cellulose fiber. These cellulose fibers may be fibrillated (beaten) at all. Further, natural pulp fibers obtained from used paper, waste paper and the like may be used.

Among the above-mentioned cellulose fibers, it is preferable to use one or more kinds of cellulose fibers selected from the group of softwood pulp, linter pulp, and lyocell, and it is more preferable to use lyocell. Further, it is preferable that the lyocell fiber is fibrillated (beaten). By using these preferable cellulose fibers, a network structure containing the cellulose fibers as an essential component can be easily formed, and the fibers can be suppressed from falling off. Further, it is possible to obtain the effect of stabilizing the operability when the carbon short fiber wet non-woven fabric is produced by the papermaking method.

The fibrillated (beating) cellulose fiber can be produced by fibrillating the above-mentioned cellulose fiber. Devices for fibrillation include beaters, PFI mills, single disc refiners (SDRs), double disc refiners (DDRs), ball mills used for dispersing and crushing pigments, dyno mills, mixers, grinders, and high-speed devices. A rotary blade homogenizer that applies shear force by a rotary blade, a double cylindrical high-speed homogenizer that generates shear force between a cylindrical inner blade that rotates at high speed and a fixed outer blade, and miniaturization by impact with ultrasonic waves. A high pressure that applies shearing force and cutting force to the fibers by applying a pressure difference of at least 20 MPa to the ultrasonic crusher and fiber suspension to pass through a small-diameter orifice to increase the speed, and then colliding them to make a sudden deceleration. Examples include devices such as homogenizers. Fibrilized cellulose fibers can be produced by using these devices alone or in combination. Then, by adjusting the fibrillation conditions such as the type of these devices, processing conditions (fiber concentration, temperature, pressure, rotation speed, shape of refiner blade, gap between refiner plates, number of processings), the desired fibrillation is achieved. You can get the state.

In the carbon short fiber wet non-woven fabric of the present invention, the binder synthetic fiber can be used as long as the performance is not impaired. Examples of the binder synthetic fiber include composite fibers such as core-sheath fibers (core-shell type), parallel fibers (side-by-side type), and radial split fibers; undrawn fibers; low melting point synthetic resin single fibers; and hot water-soluble fibers. The binder synthetic fiber has a low glass transition temperature or melting temperature (melting point) of the whole fiber or a part of the fiber, and exhibits the binder ability in the drying step of the paper machine. Since the composite fiber is difficult to form a film, the mechanical strength can be improved while maintaining the space of the carbon short fiber wet non-woven fabric. More specifically, as the composite fiber, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), a high melting point polyester (core) and a low melting point polyester (sheath). The combination of. Examples of the unstretched fiber include unstretched fiber such as polyester. In addition, low melting point synthetic resin single fibers such as single fibers (total fusion type) composed only of low melting point resins such as polyethylene and polypropylene, and hot water soluble fibers such as polyvinyl alcohol-based fibers form a film in the drying process. It is easy to use, but it can be used in the present invention. In the present invention, polyvinyl alcohol-based binder synthetic fibers, which are hot water-soluble fibers, are preferable because they easily form hydrogen bonds with functional groups on the surface of short carbon fibers to exhibit strength.

In the present invention, synthetic fibers, inorganic fibers and the like can be blended into a carbon short fiber wet non-woven fabric. For example, synthetic fibers such as polyolefin-based, polyamide-based, polyacrylic-based, vinylon-based, polyvinylidene chloride-based, polyvinyl chloride-based, polyester-based, benzoate-based, polyclaral-based, and phenol-based; glass fiber, rock fiber, slug fiber, etc. Examples include inorganic fibers such as metal fibers. Further, semi-synthetic fibers such as acetate, triacetate and promix can also be used.

The fiber length of the synthetic fiber, the inorganic fiber and the semi-synthetic fiber is not particularly limited, but is preferably 3 mm or more and less than 30 mm. The longer the fiber length of the synthetic fiber, the inorganic fiber and the semi-synthetic fiber, the more the contact points between the fibers per fiber and the more difficult it is for the fiber to fall off. The fiber length is preferably 3 mm or more. If the fiber length is too long, the papermaking property and the texture of the non-woven fabric may deteriorate, so that the fiber length is preferably less than 30 mm. The fiber diameter is not particularly limited, but is preferably 1 μm or more and less than 30 μm, and particularly preferably 2 μm or more and less than 20 μm. When a fiber having a fiber diameter of less than 1 μm is blended, the inside of the carbon short fiber non-woven fabric becomes a dense structure. May go down. When the fiber diameter is 30 μm or more, synthetic fibers or inorganic fibers having no binder ability may easily fall off.

In the present invention, the content of the carbon short fibers is 10 to 98% by mass, more preferably 20 to 97% by mass, and more preferably 30 to 96% by mass with respect to the total fibers contained in the carbon short fiber nonwoven fabric. It is more preferable to have. When the content of the carbon short fibers is less than 10% by mass, the effect of "high strength and light mass" of the carbon short fibers when processed may not be sufficiently exhibited. If the content of the carbon short fibers is more than 98% by mass, the fibers may not be sufficiently bonded to each other and shed fibers may be generated.

In the present invention, the short carbon fibers are made into a sheet by a paper machine. That is, a carbon short fiber wet non-woven fabric is manufactured by a papermaking method.

In the papermaking method, for example, a long net type, a circular net type, and an inclined wire type can be used. A paper machine having these paper making methods alone may be used, or a combination paper machine in which two or more paper machines of the same type or different types are installed online may be used. In order to produce a carbon short fiber wet non-woven fabric having excellent uniformity, it is preferable to use a papermaking method capable of gently dehydrating the slurry on the wire, such as a long net type or a slanted wire type. The carbon short fiber wet non-woven fabric of the present invention may be a single layer or a plurality of layers.

In the papermaking method, disintegration work is performed with a pulper for the purpose of dispersing short carbon fibers and other fibers. The type of pulper is not particularly limited, and vertical pulper may be used, horizontal pulper may be used, and other types of pulper may be used without any problem. The dissociation ability of the pulper is not particularly limited, but if the dissociation ability of the pulper is too strong, all the binding of the carbon short fibers may be dissociated, and if the dissociation ability of the pulper is too weak, the carbon short fibers are completely dissociated. Large bundles may remain on the non-woven fabric without dissociation, and the average number of carbon short fibers constituting the bundle may exceed 500 fibers / bundle. It is desirable to control the dissociation state of carbon short fibers by adjusting the strength and time of the pulper.

In the papermaking method, various anionic, nonionic, cationic, or amphoteric dispersants and defoamers are used when the fibers are dispersed in water for the purpose of uniformly dispersing the fibers in water and imparting various functions. , Hydrophilic agent, drainage agent, paper strength improver, slime agent, antistatic agent, polymer slime agent, mold release agent, antibacterial agent, bactericidal agent, pH adjuster, pitch control agent, slime control agent, etc. It may be added.

A sizing agent can be added to the carbon short fiber wet non-woven fabric of the present invention, if necessary. As the sizing agent, a reinforced rosin sizing agent, a rosin emulsion sizing agent, a petroleum resin-based sizing agent, a synthetic sizing agent, a neutral rosin sizing agent, and an alkyl ketene dimer (AKD), as long as they do not impair the desired effect of the present invention. ) And other sizing agents can be used.

Wet paper produced by a paper machine is dried with a Yankee dryer, an air dryer, a cylinder dryer, a suction drum type dryer, an infrared type dryer, or the like to obtain a carbon short fiber wet non-woven fabric. When the wet paper is dried, it is brought into close contact with a heat roll such as a Yankee dryer and hot-pressure dried, so that the smoothness of the contacted surface is improved. Hot pressure drying means drying by pressing wet paper against the hot roll with a touch roll or the like. The surface temperature of the heat roll is preferably 100 to 180 ° C, more preferably 100 to 160 ° C, still more preferably 110 to 160 ° C. The pressure is preferably 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

The basis weight of the short carbon fibers wet-laid nonwoven fabric of the present invention is not particularly limited, but is preferably less than 10 g / ^{m 2} or more 350 g / ^{m 2,} less than 30 g / ^{m 2} or more 300 g / ^{m 2} is more preferable. If the basis weight is ^{less than 10 g / m 2} , the density of the non-woven fabric tends to be low, and it is necessary to stack a large number of non-woven fabrics during CFRP processing, and the amount of resin permeation tends to differ between the front and back sides. It may impair uniformity. When the basis weight is 350 g / m ² or more, it is difficult to dry uniformly when drying with a dryer, and the quality of the carbon short fiber wet non-woven fabric may be uneven.

The density of the carbon short fiber wet non-woven fabric of the present invention ^{is preferably 0.12 g / cm 3} or more, and more preferably 0.15 g / cm ³ or more. If the density is ^{less than 0.12 g / cm 3} , there are many voids in the carbon short fiber wet non-woven fabric, and the resin does not penetrate to the back surface when the resin is applied, so that the quality of CFRP may differ between the front and back sides. The upper limit of the density is not particularly limited, but is preferably less than ^{0.5 g / cm 3} , and more preferably less than ^{0.4 g / cm 3.} When the density is 0.5 g / cm ³ or more, the permeation of the resin is hindered and the resin does not permeate to the back surface of the resin, so that the strength after CFRP processing may be uneven.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to this example. The number of copies and percentages in the examples are based on mass.

Example 1
The short carbon fibers (average fiber length 5 mm), the beaten lyocell fibers, and the PVA binder fibers (manufactured by Kuraray, product name: VPB107-1) were added to water at the blending ratio (mass basis) shown in Table 1. After mixing and dispersing with a vertical pulper for 10 minutes, wet paper is wet-made with a single-layer papermaking using a tilted wire method, dried with a Yankee dryer with a surface temperature of 130 ° C., and has a papermaking speed of 20 m / min and a basis weight of 50 g / m. A short carbon fiber wet non-woven fabric of No. ^{2 was obtained.}

Examples 2-4
The carbon short fiber wet non-woven fabric of Examples 2 to 4 was obtained in the same manner as in Example 1 except that the dispersion time of the fibers was changed to the contents shown in Table 1.

Comparative Examples 1 to 4
The carbon short fiber wet non-woven fabrics of Comparative Examples 1 to 4 were obtained in the same manner as in Example 1 except that the dispersion time of the fibers was changed to the contents shown in Table 1.

Examples 5 and 6
The carbon short fiber wet non-woven fabrics of Examples 5 and 6 were obtained in the same manner as in Example 1 except that the composition of the carbon short fiber wet non-woven fabric was changed to the contents described in Table 1.

Examples 7 and 8
The carbon short fiber wet non-woven fabrics of Examples 7 and 8 were obtained in the same manner as in Example 1 except that the composition of the carbon short fiber wet non-woven fabric was changed to the contents shown in Table 1.

Examples 9-12
The carbon short fiber wet non-woven fabrics of Examples 9 to 12 were obtained in the same manner as in Example 1 except that the basis weight of the carbon short fiber wet non-woven fabric was changed to the contents shown in Table 1.

Comparative Example 5
The carbon short fiber wet non-woven fabric of Comparative Example 5 was obtained in the same manner as in Example 1 except that the basis weight of the carbon short fiber wet non-woven fabric was changed to the contents shown in Table 1.

Examples 13-16
The carbon short fiber wet non-woven fabrics of Examples 13 to 16 were obtained in the same manner as in Example 1 except that the average fiber length of the carbon short fibers was changed to the contents shown in Table 1.

Examples 17-22
The carbon short fiber wet non-woven fabrics of Examples 17 to 22 were obtained in the same manner as in Example 1 except that the composition of the carbon short fiber wet non-woven fabric was changed to the contents shown in Table 1.

The details of the fibers listed in Table 1 are as follows.

Beating lyocell: Lyocell fibers (fineness 1.4 dtex, fiber length 3 mm) were treated with a double disc refiner and prepared to generate branches with an average fiber diameter of 1 μm or less from a trunk with an average fiber diameter of 14.0 μm. fiber.
Beating softwood pulp: Natural softwood pulp prepared to have a freeness of 500 ml CSF.
PET fiber: Fineness 1.7 decitex, fiber length 5 mm
Aramid fiber: Fineness 0.9 decitex, fiber length 5 mm
PET binder: Polyethylene terephthalate (PET) unstretched binder fiber, fineness 1.2 decitex, fiber length 5 mm

In the prepared carbon short fiber wet non-woven fabrics in Examples and Comparative Examples, the number of bundles, the average number and density of carbon short fibers constituting the bundle were measured, and the permeability and papermaking property of the resin were evaluated. The measurement results and evaluation results are shown in Table 1.

<Number of carbon fiber bundles>
Ten pieces of carbon short fiber wet paper non-woven fabric cut into 1 cm × 1 cm squares were collected, the contact surface of the Yankee dryer was observed with an optical microscope, the number of fiber bundles was measured, and the average value was obtained.

<Average number of carbon short fiber bundles>
100 fiber binding portions were collected from the carbon short fiber wet non-woven fabric with tweezers, and the average number of carbon short fibers constituting the binding was determined from the mass thereof.

<Density>
The basis weight of the carbon short fiber wet non-woven fabric was measured according to JIS P 8124: 2011. The thickness was measured with a Teclock thickness gauge (meter diameter 16 mm, measuring load 5 N). The density was determined from the obtained basis weight and thickness.

<Resin permeable back side>
A thermosetting epoxy resin twice as much as the carbon short fiber wet nonwoven fabric was coated on the surface of the carbon short fiber wet nonwoven fabric, and whether or not the resin penetrated to the back surface was evaluated.

◯: A large amount of resin penetrated to the back surface.
Δ: The resin slightly penetrated to the back surface.
X: The resin did not penetrate to the back surface.

<Inside resin permeable binding>
After coating the resin, the cross section of CFRP obtained by heating at 130 ° C. for 20 minutes to cure the resin was observed by SEM, and the permeation state of the resin inside the bundle of carbon short fibers was observed and evaluated.

◯: The resin penetrated evenly into the bundle.
Δ: A slight void was found inside the binding.
X: A void was found inside the binding.

<Papermaking>
It was confirmed whether or not a problem occurred when making a carbon short fiber wet non-woven fabric.
◯: No problem was found when papermaking.
Δ: Slight problems were seen when papermaking ×: Many problems were seen when papermaking.

The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more carbon short fibers is 5 pieces / cm ² or more. In Examples 1 to 4, which are carbon short fiber wet non-woven fabrics having an average number of carbon short fibers constituting the binding of 500 fibers / binding or less, both on the back surface and inside the binding. It can be seen that it is an excellent non-woven fabric with short carbon fibers because the resin has penetrated into it. Further, from the results of Examples 1 and 2, by shortening the disassembly time with the pulper, the average number of carbon short fibers constituting the bundling is increased and the bundling is increased, and as a result, the inside of the bundling is slightly increased. It can be seen that the resin is difficult to penetrate. Further, from the results of Examples 1 and 4, by lengthening the disassembly time with the pulper, the average number of carbon short fibers constituting the binding is reduced and the binding is reduced, and as a result, the carbon short fiber wet non-woven fabric is used. It can be seen that it is difficult for the resin to permeate because the density of carbon dioxide is low.

On the other hand, in Comparative Examples 1 and 2, since the dissociation time is short, the decoupling of the carbon short fibers is insufficient, so that the average number of carbon short fibers constituting the bundling is more than 500 / bundling. It was confirmed that the resin did not penetrate into the binding. Since the resin does not penetrate into the binding, there is a place where the strength is weak in the CFRP, and breakage may occur from that place, so that it may not be suitable as CFRP. In addition, there is a tendency for bundles with a large number of fibers to accumulate in tanks and pipes during papermaking, which causes problems during papermaking.

In Comparative Examples 3 and 4, it was confirmed that the short carbon fibers were almost completely dissociated and the number of bundles was small because the dissociation time was long. In Comparative Example 3, the number of bundles composed of 10 or more short carbon fibers was 1 piece / cm ² , and in Comparative Example 4, it was ^{0 piece / cm 2.} Therefore, the carbon short fiber wet non-woven fabric forms a complicated three-dimensional structure and has a low density, and the density of the carbon short fiber wet non-woven fabric of Comparative Example 4 is less than ^{0.12 g / cm 3.} This resulted in the resin not penetrating to the back surface. Since the resin does not penetrate to the back surface, a concentration gradient of the resin may occur during CFRP processing, and the quality is not stable, so that it may not be suitable as CFRP. In addition, the non-woven fabric having a small number of bundles tends to contain a large amount of water during papermaking, so that drying is insufficient, and a problem occurs during papermaking.

The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more carbon short fibers is 5 pieces / cm ² or more. In Examples 5 and 6, which are the carbon short fiber wet non-woven fabrics having an average number of carbon short fibers constituting the binding of 500 fibers / binding or less, both on the back surface and inside the binding. It can be seen that it is an excellent non-woven fabric with short carbon fibers because the resin has penetrated into it. Further, from the results of Example 5 in which the beaten lyocell of Example 1 was changed to beaten coniferous pulp and the result of Example 6 in which the PVA binder synthetic fiber of Example 1 was changed to PET binder synthetic fiber, fibers other than carbon short fibers. It can be seen that there is no problem even if the fiber is changed to a fiber other than the fiber described in Example 1.

The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more carbon short fibers is 5 pieces / cm ² or more. In Examples 7 and 8, which are the carbon short fiber wet non-woven fabrics having an average number of carbon short fibers constituting the binding of 500 fibers / binding or less, both on the back surface and inside the binding. It can be seen that it is an excellent non-woven fabric with short carbon fibers because the resin has penetrated into it. Even in Examples 7 and 8 in which PET fiber or aramid fiber is blended as the synthetic fiber, there is no problem in the permeability of the resin, so that the blending of the synthetic fiber does not affect the permeability of the resin. Was confirmed.

The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more carbon short fibers is 5 pieces / cm ² or more. In Examples 9 to 12, which are carbon short fiber wet non-woven fabrics having an average number of carbon short fibers constituting the binding of 500 fibers / binding or less, both on the back surface and inside the binding. It can be seen that it is an excellent non-woven fabric with short carbon fibers because the resin has penetrated into it. In Example 12 having a basis weight of 350 g / m ² or more, it is difficult to uniformly dry the paper during wet papermaking, the quality tends to differ between the front and back sides, and the high density results in a slight resin. The result was that it was difficult to penetrate.

In Comparative Example 5, by lowering the basis weight, the number of bundles composed of 10 or more carbon short fibers ^{is less than 5 pieces / cm 2} , and the density is also low, so that the resin penetrates to the back surface. It may not be suitable as CFRP because the density gradient of the resin may occur during CFRP processing and the quality is not stable. In addition, since paper breaks frequently occur during papermaking, the result is inferior in papermaking performance. Since the smaller the basis weight of the carbon short fiber wet non-woven fabric, the lower the density tends to be, it can be seen that ^{the basis weight is preferably 10 g / m 2 or more.}

The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more carbon short fibers is 5 pieces / cm ² or more. In Examples 13 to 16, which are carbon short fiber wet non-woven fabrics having an average number of carbon short fibers constituting the binding of 500 fibers / binding or less, both on the back surface and inside the binding. It can be seen that it is an excellent non-woven fabric with short carbon fibers because the resin has penetrated into it. In Example 13 in which the average fiber length of the carbon short fibers is short, the fibers are difficult to entangle with each other, so that it is difficult to form a bond, and the carbon short fiber wet non-woven fabric having less binding tends to be a low-density non-woven fabric having a complicated three-dimensional structure. Therefore, it was confirmed that the resin was a little difficult to penetrate. In Example 16 in which the average fiber length of the carbon short fibers was long, the fibers tended to be easily deposited on the uneven portions of the paper machine during papermaking, resulting in slightly inferior manufacturability.

The content of short carbon fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more short carbon fibers is 5 pieces / cm ² or more. In Examples 17 to 22, which are carbon short fiber wet non-woven fabrics having an average number of short carbon fibers constituting the binding of 500 fibers / binding or less, the back surface also has the inside of the fiber binding. It can be seen that the resin is also permeated into the non-woven fabric, which is an excellent non-woven fabric with short carbon fibers. However, in Example 17 in which the content of the short carbon fibers is 10% by mass, it can be seen that the resin is somewhat difficult to permeate because a large amount of fine beaten lyocell and synthetic fibers are blended. Further, in Example 22 in which the content of the short carbon fibers was 98% by mass, there was no problem in the permeability of the resin, but there was a slight problem because a slight amount of shed fibers were generated during papermaking. ..

According to the present invention, it is possible to obtain a carbon short fiber wet non-woven fabric in which the resin permeates uniformly in a short time when it is processed into CFRP.

1 Carbon short fiber bundling (the number of carbon short fiber fibers constituting the bundling is 500 / bundling or less)
2 Carbon short fiber binding (the number of carbon short fiber fibers constituting the binding is 500 / more than binding)

Claims (3)

The content of carbon short fibers is 10% by mass to 98% by mass, the density of the non-woven fabric is 0.12 g / cm ³ or more, and the binding composed of 10 or more carbon short fibers is 5 pieces / cm ² or more. has an average number of fibers short carbon fibers constituting the strapping is Ri 500 / binding der hereinafter short carbon fibers wet-laid nonwoven fabric which is characterized that you blended cellulosic fibers. The carbon fiber wet non-woven fabric according to claim 1, wherein the average fiber length of the carbon short fibers is 1 mm or more. A carbon short fiber reinforced resin composition comprising the carbon short fiber wet non-woven fabric according to claim 1 or claim 2 and a resin composited with the non-woven fabric.

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