JP2019105003A - Carbon short fiber wet non-woven fabric and carbon fiber reinforced resin - Google Patents

Abstract

SOLUTION: This invention relates to a carbon short fiber wet non-woven fabric characterized in that: the proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric; the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to total carbon short fibers; and the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total carbon short fibers.EFFECT: A carbon short fiber wet non-woven fabric can be obtained which exhibits excellent molding flowability when processed into a carbon fiber reinforced resin (CFRP) and has excellent strength and uniformity after CFRP processing.SELECTED DRAWING: None

Description

  The present invention relates to a carbon short fiber wet nonwoven fabric and a carbon fiber reinforced resin.

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

  As carbon fibers, currently, PAN-based carbon fibers obtained by carbonizing and graphitizing polyacrylonitrile and pitch systems obtained by melt-spinning tar pitch liquefied coal and then carbonizing and graphitizing Carbon fiber and is used. The carbon fiber produced in this way was processed as a woven fabric, or after being arranged in one direction, a material called a carbon fiber prepreg impregnated with an uncured resin was cut to fit the mold of the target molding It is often used as a carbon fiber reinforced resin (hereinafter, "carbon fiber reinforced resin" may be abbreviated as "CFRP") obtained by curing the resin later. Alternatively, when using carbon fibers obtained by recycling CFRP waste material, carbon fibers are shorted in the recycling process to become carbon short fibers and can not be processed as woven fabrics, so they are processed as non-woven fabrics Is common.

  As a method of forming a carbon short fiber into a sheet and forming a carbon short fiber non-woven fabric, a carbon short fiber and a water-swelled fibrillated fiber are dispersed in water to prepare a slurry for paper making, and the fiber is entangled, A method of making a nonwoven is disclosed. As water-swelled fibrillated fibers, fibrillated para-type aromatic polyamide fibers and fibrillated acrylic fibers are mentioned (see Patent Document 1). However, this method does not take into consideration the flowability of fibers and resin during CFRP processing of a carbon short fiber non-woven fabric and the uniformity of carbon short fibers in the non-woven fabric, and there are problems when processing CFRP. It may occur. When the flowability of fibers and resin is low during CFRP processing, the fibers and resin may not spread to fine parts when processing CFRP having a complicated shape, and it may not be able to be processed into a complicated shape. Moreover, when the carbon short fiber in a nonwoven fabric is not uniform, the intensity | strength after CFRP process will also become uneven, and it may not be suitable as CFRP.

  In addition, as another method of producing a carbon short fiber wet nonwoven fabric, in a method of producing a carbon short fiber wet nonwoven fabric comprising 75% by mass to 97% by mass of carbon short fibers and 25% by mass to 3% by mass of cellulose A solvent-containing aqueous dispersion aid is added to 10% by mass or less of carbon short fibers and carbon short fibers to a predetermined amount of water with respect to carbon short fibers and stirred, and the slurry solid concentration is further adjusted to 0.05% by mass or less A method of wet papermaking after a step of dilution and circulation is shown (see Patent Document 2). However, since 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, the fiber / resin molding when carbon short fiber non-woven fabric is CFRP processed It is not considered in terms of flowability or uniformity of carbon short fibers in the non-woven fabric, and a defect may occur during CFRP processing or after CFRP processing.

International Publication No. 2014/021366 Pamphlet JP, 2004-353124, A

  An object of the present invention is to obtain a carbon short fiber wet nonwoven fabric which exhibits excellent molding flowability when processed into CFRP, has high strength after CFRP processing, and is excellent in uniformity.

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

(1) The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98 mass with respect to all carbon short fibers A short carbon fiber non-woven fabric characterized in that the ratio of short carbon fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total short carbon fibers.
(2) A carbon fiber reinforced resin comprising the carbon short fiber wet nonwoven fabric according to the above (1) and a resin composited with the nonwoven fabric.

  According to the present invention, it is possible to obtain a carbon short fiber wet nonwoven fabric which exhibits excellent molding flowability when processed into CFRP and has excellent strength and uniformity after CFRP processing.

In an Example, it is the figure which showed the method of rib-forming in the case of <CFRP molding flowability evaluation>.

  The present invention is a method for obtaining a carbon short fiber wet non-woven fabric having excellent moldability and flowability when it is processed into CFRP. When the carbon short fiber non-woven fabric is processed into CFRP, when the molding flowability of the carbon short fiber non-woven fabric is low, there may occur a problem that it can not be processed into a complicated shape. That is, although carbon short fibers do not flow with the resin and only the resin forms a complicated shape, the strength of the portion of only the resin becomes very weak, which may cause a problem that it is not suitable as a CFRP. Moreover, even if there is molding fluidity of the carbon short fiber nonwoven fabric, when the carbon short fibers flow, the carbon short fibers are gathered together and there are places where the density becomes high, and as a result, the strength and the high density of the low density place Since the strength of the portion becomes uneven, the quality of the CFRP also becomes uneven, which may cause a problem of being unsuitable as a carbon short fiber non-woven fabric for CFRP processing.

  As a result of conducting earnest research to solve these problems, the proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the nonwoven fabric, and the proportion of carbon short fibers whose fiber length is longer than 2 mm Is 20 to 98 mass% with respect to total carbon short fibers, and the ratio of carbon short fibers having a fiber length of 2 mm or less is 80 to 2 mass% with respect to total carbon short fibers The wet non-woven fabric was found to have high moldability of carbon short fibers and high strength and uniformity after CFRP processing. If the proportion of carbon short fibers having a fiber length of 2 mm or less exceeds 80% by mass, the strength after CFRP processing becomes low, which is not suitable as a carbon short fiber non-woven fabric for CFRP. In addition, when the proportion of carbon short fibers having a fiber length of more than 2 mm exceeds 98 mass%, voids tend to be increased in the non-woven fabric, and the carbon short fibers tend to be nonuniform during CFRP processing. By filling the voids in the non-woven fabric with carbon short fibers having a fiber length of 2 mm or less, CFRP in which carbon short fibers are uniform can be obtained.

  In the present invention, the proportion of carbon short fibers having a fiber length of more than 2 mm is from 20 to 98% by mass, more preferably from 25 to 95% by mass, and still more preferably from 30 to 90%. It is mass%. In addition, the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass, more preferably 75 to 5% by mass, and still more preferably 70 to 10% by mass with respect to total carbon short fibers. is there.

  In the present invention, carbon short fibers refer to fibers having a fiber length of 50 mm or less. Moreover, it is preferable that the lower limit of the fiber length in "a carbon short fiber whose fiber length is 2 mm or less" is 0.1 mm. When the fiber length of carbon short fibers is less than 0.1 mm, the fibers may fall off when producing a wet nonwoven fabric.

  As carbon short fibers, carbon short fibers produced by any method such as PAN type and pitch type can be used. In addition, there is no problem in both new and unused carbon short fibers and carbon short fibers obtained by recycling discarded carbon fibers. Considering the cost required to obtain carbon short fibers, carbon short fibers obtained by recycling are more preferable.

  In the short carbon fiber non-woven fabric of the present invention, fibers other than short carbon fibers can be contained as long as the performance is not impaired. Hereinafter, "fibers other than carbon short fibers" may be abbreviated as "other fibers". Examples of other fibers include cellulose fibers, semi-synthetic fibers, synthetic fibers, inorganic fibers and the like.

  Cellulose fibers can be used. Examples of the type of cellulose fiber include natural cellulose fiber, regenerated cellulose fiber and the like. Natural cellulose fibers include wood pulp such as softwood pulp and hardwood pulp; wood pulp such as straw pulp, bamboo pulp, linter pulp and kenaf pulp or herbaceous pulp. Examples of regenerated cellulose fibers include regenerated cellulose fibers such as rayon, cupra and lyocell. These cellulose fibers may be fibrillated (beaten) at all. Furthermore, pulp fibers obtained from waste paper, broke or the like may be used.

  Among the above-mentioned cellulose fibers, it is preferable to use one or more cellulose fibers selected from the group of softwood pulp, linter pulp and lyocell, and it is more preferable to use lyocell. Also, lyocell is preferably fibrillated (beaten). By using these preferred cellulose fibers, it is possible to suppress the falling off of the fibers. In addition, the effect of stabilizing the operability in the case of producing a carbon short fiber wet non-woven fabric by a papermaking method is also obtained.

  Fibrillated (refined) cellulose fibers can be produced by fibrillating the above-described cellulose fibers. As devices for fibrillation, beaters, PFI mills, single disc refiners (SDR), double disc refiners (DDR), ball mills used for dispersing or crushing pigments, etc., dyno mills, mixers, milling machines, high speed Rotary blade type homogenizer which applies shear force by rotary blade, Double cylindrical type high speed homogenizer which produces shear force between cylindrical inner blade rotating at high speed and fixed outer blade, Refinement by ultrasonic impact Ultrasonic crusher, apply a pressure difference of at least 20MPa to the fiber suspension, pass through a small diameter orifice to make it high speed, collide it and rapidly decelerate it to apply high shear force and cutting force to the fiber An apparatus such as a homogenizer may be mentioned. By using these devices alone or in combination, fibrillated cellulose fibers can be produced. And, by adjusting the fibrillation conditions such as the type of these devices, processing conditions (fiber concentration, temperature, pressure, number of revolutions, shape of refiner blade, gap between refiner plates, number of times of treatment), desired fibrillation You can get the status.

  Examples of synthetic fibers include polyolefin-based, polyamide-based, polyacrylic-based, vinylon-based, polyvinylidene chloride-based, polyvinyl chloride-based, polyester-based, benzoate-based, polychloral-based, and phenol-based synthetic fibers. . Inorganic fibers include inorganic fibers such as glass fibers, rock fibers, slug fibers and metal fibers. Moreover, as a semi-synthetic fiber, acetate, triacetate, promix etc. are mentioned.

  In the carbon short fiber wet non-woven fabric of the present invention, a binder synthetic fiber can be used as long as the performance is not impaired. Examples of binder synthetic fibers include composite fibers such as core-sheath fibers (core-shell type), parallel fibers (side-by-side type), radially divided 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 develops a binder ability in the drying process of the paper machine. The composite fiber is less likely to form a film, and thus the mechanical strength can be improved while maintaining the space of the carbon short fiber wet nonwoven fabric. More specifically, as a composite fiber, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), high melting point polyester (core) and low melting polyester (sheath) A combination of The undrawn fibers include undrawn fibers such as polyester. In addition, low-melting-point synthetic resin single fibers such as single fibers (full melting type) composed only of low-melting-point resins such as polyethylene and polypropylene, and hot water-soluble fibers such as polyvinyl alcohol, form a film in the drying step. Although easy to use, it can be used in the present invention. In the present invention, a polyvinyl alcohol-based binder synthetic fiber which is a hot water soluble fiber is preferable because it easily forms a hydrogen bond with a functional group on the surface of a carbon short fiber to exhibit strength.

  Among the other fibers, the fiber length of non-fibrillated regenerated cellulose fiber, synthetic fiber, inorganic fiber and semi-synthetic fiber is not particularly limited, but is preferably 3 mm or more and less than 30 mm. As the fiber length of these other fibers is longer, the number of contact points between fibers increases, and the fibers tend to be less likely to come off, so the fiber length of these other fibers 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 the fiber length is preferably less than 30 mm. The fiber diameter is also 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. If fibers with a fiber diameter of less than 1 μm are blended, the carbon short fiber wet non-woven fabric will have an excessively dense structure. For example, when processing such as impregnating a resin into carbon short fiber wet non-woven fabric It may inhibit and the performance of CFRP after processing may deteriorate. 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 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 all the fibers contained in the carbon short fiber wet nonwoven fabric. It is further preferred that When the content of the carbon short fiber is less than 10% by mass, the effect that the carbon short fiber has “high strength and light weight” may not be sufficiently exhibited when processed. When the content of carbon short fibers is more than 98% by mass, bonding of the fibers becomes insufficient, and there may be generation of dropped fibers.

  The short carbon fiber non-woven fabric of the present invention is obtained by a paper making method in which the short carbon fiber is formed into a sheet by a paper machine.

  In the paper making method, for example, a long mesh type, a circular mesh type, and an inclined wire type can be used. A paper machine having these papermaking systems alone may be used, or a combination paper machine in which two or more papermaking systems of the same type or different types are installed on-line may be used. In order to produce a carbon short fiber wet non-woven fabric excellent in uniformity, it is preferable to use a papermaking method that can be dewatered from the slurry on the wire gently, such as a long mesh type or a gradient wire type. The carbon short fiber wet nonwoven fabric of the present invention may be a single layer or multiple layers.

  In the papermaking method, a pulping operation is carried out for the purpose of dispersing carbon short fibers and other fibers. The type of pulper is not particularly limited, and a vertical pulper may be used, a horizontal pulper may be used, and other types of pulpers have no problem. The disaggregation ability of the pulper is also not particularly limited, but if the disaggregation ability of the pulper is too strong, carbon short fibers may be crushed by the pulper to become milled and the strength after CFRP processing may be reduced. If the pulping ability is too weak, the carbon short fibers may not be completely disintegrated, the texture may deteriorate, the carbon short fibers may become uneven, and the strength after CFRP processing may also become uneven. The state of carbon short fiber disaggregation is desirably controlled by adjusting the strength and time of the pulper.

  When the fibers are dispersed in water in order to disperse the fibers uniformly in water or to impart various functions in the papermaking method, various anionic, nonionic, cationic or amphoteric dispersants, antifoaming agents Chemicals such as hydrophilic agent, drainage agent, paper strength improver, viscosity improver, antistatic agent, polymer adhesive, mold release agent, antibacterial agent, bactericidal agent, pH adjustor, pitch control agent, slime control agent, etc. It may be added.

  A sizing agent can be blended into the carbon short fiber wet nonwoven fabric of the present invention as required. As sizing agents, fortified rosin sizing agents, rosin emulsion sizing agents, petroleum resin sizing agents, synthetic sizing agents, neutral rosin sizing agents, alkyl ketene dimers (AKD) as long as the desired effects of the present invention are not impaired. Any of the sizing agents such as) can be used.

  The wet short web produced by the paper machine is dried with a Yankee dryer, air dryer, cylinder dryer, suction drum dryer, infrared dryer or the like to obtain a carbon short fiber wet non-woven fabric. When the wet paper is dried, by bringing it into close contact with a heat roll such as a Yankee drier and performing heat and pressure drying, the smoothness of the adhered surface is improved. Hot-pressure drying refers to pressing a wet paper against a heat roll with a touch roll or the like to dry it. 100-180 degreeC is preferable, as for the surface temperature of a heat roll, 100-160 degreeC is more preferable, and 110-160 degreeC is still more preferable. The pressure is preferably 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

Although the basis weight of the carbon short fiber wet nonwoven fabric of the present invention is not particularly limited, it is preferably 10 g / m ² or more and 500 g / m ² or less, and more preferably 30 g / m ² or more and 400 g / m ² or less. If the basis weight is less than 10 g / m ² , the density of the non-woven fabric tends to be too low, and it is necessary to stack many non-woven fabrics during CFRP processing, and the difference in penetration of resin tends to occur. It may impair the uniformity of the If the basis weight is more than 500 g / m ² , it may be difficult to uniformly dry when drying with a drier, and unevenness may occur in the quality of the carbon short fiber wet non-woven fabric.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In the examples, parts and percentages are on a mass basis.

Example 1
A vertical pulper is charged with short carbon fibers having a fiber length shown in Table 1, a beaten Lyocell, and a PVA binder (made by Kuraray, product name: VPB 107-1) in water at a blending ratio (mass basis) described in Table 1 After mixing and dispersing for 10 minutes, wet paper was further made by wet wire making with single layer by inclined wire method, dried by Yankee dryer with surface temperature of 130 ° C., carbon with basis weight of 50 g / m ² at paper making speed of 20 m / min. A short fiber wet non-woven fabric was obtained.

Examples 2 to 4 and Comparative Examples 1 to 4
The carbon short fiber wet nonwoven fabrics of Examples 2 to 4 and Comparative Examples 1 to 4 were obtained in the same manner as Example 1 except that the fiber length of carbon short fibers and the compounding ratio of carbon short fibers were changed to the contents described in Table 1. .

Examples 5 and 6
A carbon short fiber wet non-woven fabric of Examples 5 and 6 was obtained in the same manner as Example 1, except that the type of cellulose fiber or the type of binder synthetic fiber was changed to the contents described in Table 1.

Examples 7 and 8
A carbon short fiber wet non-woven fabric of Examples 7 and 8 was obtained in the same manner as Example 1 except that synthetic fibers were added and the blend ratio of each fiber was changed to the contents described in Table 1.

Examples 9 to 11 and Comparative Examples 5 to 7
The short carbon fiber non-woven fabrics of Examples 9 to 11 and Comparative Examples 5 to 7 were obtained in the same manner as Example 1 except that the content of the short carbon fibers was changed to the contents described in Table 1.

Examples 12 to 17 and Comparative Example 8
A carbon short fiber wet non-woven fabric of Examples 12 to 17 and Comparative Example 8 was obtained in the same manner as Example 1 except that the blending ratio of the carbon short fiber, the refined lyocell and the PVA binder was changed to the contents described in Table 1.

Examples 18 to 23
A carbon short fiber wet non-woven fabric of Examples 18 to 23 was obtained in the same manner as Example 1 except that the type and blending ratio of carbon short fibers were changed to the contents described in Table 1.

Examples 24-29
A carbon short fiber wet non-woven fabric of Examples 24 to 29 was obtained in the same manner as Example 1 except that the basis weight of the carbon short fiber wet non-woven fabric was changed to the contents described in Table 1.

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

Refined lyocell: lyocell fiber (fineness 1.4 dtex, fiber length 3 mm) was treated using a double disc refiner to prepare branches with a mean fiber diameter of 1 μm or less from a stem with a mean fiber diameter 14.0 μm fiber.
Reconstituted softwood pulp: Natural softwood pulp prepared to have a freeness of 500 ml CSF.
PET fiber: Polyethylene terephthalate (PET) drawn fiber, fineness 1.7 dtex, fiber length 5 mm
Aramid fiber: fineness 0.9 dtex, fiber length 5 mm
PVA binder: polyvinyl alcohol binder fiber (made by Kuraray, product name: VPB107-1)
PET binder: PET unstretched binder fiber, fineness 1.2 dtex, fiber length 5 mm

  The basis weight was measured in the carbon short fiber wet non-woven fabric manufactured in the examples and the comparative examples, and the strength, uniformity and molding flowability after CFRP processing were evaluated, and the measurement results and the evaluation results are shown in Table 1. .

<Basic weight>
The basis weight of the carbon short fiber wet non-woven fabric was measured according to JIS P 8124: 2011.

<CFRP processing>
CFRP processing of carbon short fiber wet non-woven fabric was performed. After applying a thermosetting resin in which a curing agent is mixed to a carbon short fiber non-woven fabric twice as much as the mass of the carbon short fiber non-woven fabric, heat pressing (temperature 120 ° C., pressure 5 MPa) is performed so that the thickness is 2 mm. , CFRP board of carbon short fiber wet non-woven fabric was obtained.

The epoxy resin used is as follows.
Epoxy resin: GM-6800 (Bleni Giken)
Viscosity after curing agent mixing: 505 cps

  The epoxy resin was subjected to CFRP processing after the curing agent was mixed so that the main agent / curing agent would be 10/3.

<Strength evaluation after CFRP processing>
The strength of the produced CFRP board was evaluated by measuring N = 10 times for each sample in accordance with JIS K 7074: 1988.

○: A sufficiently high strength as CFRP was obtained.
Δ: A high strength was obtained although it was somewhat lower as CFRP.
X: The strength was insufficient as CFRP.

<Evaluation of uniformity after CFRP processing>
The coefficient of variation of the strength of the produced CFRP was determined and evaluated.

○: The variation coefficient was less than 10% and the intensity was uniform. Δ: the variation coefficient was 10 to 30%, and the intensity was somewhat nonuniform.
X: The coefficient of variation was higher than 30%, and the intensity was uneven.

<CFRP molding flowability evaluation>
In order to measure the molding fluidity of the carbon short fiber wet non-woven fabric, the composite 31 obtained by applying the thermosetting resin to the carbon short fiber non-woven fabric as in the above <CFRP processing> is an upper plate (with slits) 11 and a lower plate (without a slit) 21 and hot press forming (temperature 120 ° C., pressure 5 MPa) to form a rib 41 having a width of 2 mm and a length of 50 mm, and measuring the forming fluidity (Figure 1).

Good: Ribs containing carbon fibers were formed to be higher than 3 mm, and high molding flowability was observed.
Δ: Ribs containing carbon fibers were formed at a height of 0.5 to 3 mm, and somewhat high fluidity was observed.
X: The rib containing carbon fiber was formed lower than 0.5 mm, and molding fluid property was not seen.

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers In Examples 1 to 4 in which the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to the mass of all carbon short fibers, excellent molding flowability and strength and uniformity after CFRP processing It is understood that it has sex. Since carbon short fibers having a fiber length longer than 2 mm exhibit high strength of carbon fibers and short carbon short fibers having a length of 2 mm or less have high molding flowability, the fibers can flow in the ribs, It was possible to form CFRP ribs containing carbon short fiber wet non-woven fabric. In addition, since short carbon short fibers having a fiber length of 2 mm or less play a role of filling the void portion of CFRP, excellent uniformity of CFRP was shown by uniformly blending the carbon fiber inside the CFRP.

  Further, in Comparative Examples 1 and 2 in which all the carbon short fibers are carbon short fibers having a fiber length of 2 mm or less, it is understood that although they have excellent molding fluidity, the strength after CFRP processing is low. It is presumed that this is because all the carbon fibers are short and therefore the carbon fibers can not sufficiently exhibit the strength. Further, in Comparative Examples 3 and 4 in which all carbon short fibers are carbon short fibers longer than 2 mm, although the strength after CFRP processing was high, no carbon short fibers were found in the rib portion, and the molding flow to carbon short fibers I did not see any sex. This is because all carbon fibers are long, there are many points of contact between carbon short fibers, and only carbon short fibers in which the fibers are strongly bonded exist, so carbon short fibers do not enter the fine rib portion, and molding flowability is It is presumed that it could not be seen.

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers In Examples 5 to 8 in which the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total carbon short fibers, excellent molding flowability and strength and uniformity after CFRP processing are obtained. I know that I have. From the results of Example 5 in which the beaten lyocell of Example 1 was changed to a beaten softwood pulp and the results 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 were implemented It can be seen that there is no problem in changing to fibers other than the fibers described in Example 1. Further, in Examples 7 and 8 in which PET fiber or aramid fiber is blended as a synthetic fiber, no problem is observed in the evaluation result, so that blending of synthetic fiber has no influence on CFRP processability. Was confirmed.

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers In Examples 9 to 11 in which the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total carbon short fibers, excellent molding flowability and strength and uniformity after CFRP processing are obtained. I know that I have. From the results of Examples 9 to 11 in which the proportions of the carbon short fibers of 2 mm or less and the carbon short fibers longer than 2 mm in Example 1 were changed, carbon short fibers having a fiber length longer than 2 mm / carbon having a fiber length of 2 mm or less If the ratio of carbon short fibers having a fiber length of 2 mm or less and carbon short fibers having a fiber length longer than 2 mm is changed within the range of short fibers = 20 to 98 mass% / 80 to 2 mass%, there is a problem I understand that there is no.

  In Comparative Example 5, since the ratio of carbon short fibers having a fiber length of 2 mm or less is less than 2% by mass with respect to total carbon short fibers, carbon short fibers entering the rib portion and carbon entering voids in CFRP It is presumed that the molding flowability and the uniformity after CFRP processing are deteriorated because the short fibers are reduced. In Comparative Examples 6 and 7, the proportion of carbon short fibers having a fiber length longer than 2 mm is less than 20% by mass with respect to total carbon short fibers, and long fibers are reduced, so the carbon fiber strength is sufficiently exhibited. It is guessed that it can not be done.

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers In Examples 12 to 17 in which the proportion of carbon short fibers having a fiber length of 2 mm or less with respect to total carbon short fibers is excellent in molding flowability, CFRP strength, and uniformity. I understand. From the results of Example 1 and Examples 12 to 17 in which the ratio of carbon short fibers to total fibers constituting the nonwoven fabric is changed, if the ratio of carbon short fibers is 10 to 98% by mass with respect to all fibers, It turns out that there is no problem. In Example 12, since the proportion of carbon short fibers is somewhat low, the strength and molding flowability after CFRP processing were somewhat low.

  In Comparative Example 8 in which the proportion of carbon short fibers is less than 10% by mass with respect to all the fibers constituting the non-woven fabric, it is assumed that the strength after CFRP processing is insufficient because there are few carbon short fibers.

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers In Examples 18 to 23 in which the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total carbon short fibers, excellent molding flowability and strength and uniformity after CFRP processing are obtained. I know that I have. From the results of Examples 18 to 23 in which a plurality of carbon short fibers having a fiber length of 2 mm or less and a carbon short fiber having a fiber length longer than 2 mm are mixed, carbon short fibers having a fiber length greater than 2 mm / fiber length If it is within the range of carbon short fibers of 2 mm or less = 20 to 98% by mass / 80 to 2% by mass, it can be understood that there is no problem even if plural carbon short fibers having different fiber lengths are mixed and used.

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers In Examples 24 to 29, in which the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total carbon short fibers, excellent molding flowability and strength and uniformity after CFRP processing are obtained. I know that I have. From the results of Examples 24 to 29 in which the basis weight is changed, it can be understood that there is no problem even if the basis weight is changed as long as the ratio of carbon short fibers is in the above range.

  The carbon short fiber wet nonwoven fabric of the present invention can be suitably used for carbon fiber reinforced resin (CFRP) processing.

11 Upper plate (with slits)
21 Lower plate (without slits)
31 Carbon staple non-woven fabric and thermosetting resin composite 41 rib

Claims (2)

  The proportion of carbon short fibers is 10 to 98% by mass with respect to all the fibers constituting the non-woven fabric, and the proportion of carbon short fibers having a fiber length longer than 2 mm is 20 to 98% by mass with respect to all carbon short fibers A carbon short fiber wet nonwoven fabric characterized in that the proportion of carbon short fibers having a fiber length of 2 mm or less is 80 to 2% by mass with respect to total carbon short fibers.   A carbon fiber reinforced resin comprising the carbon short fiber wet nonwoven fabric according to claim 1 and a resin composited with the nonwoven fabric.