JP6662079B2 - Sheet for fiber reinforced plastic molding - Google Patents

Description

  The present invention relates to a sheet for a fiber-reinforced plastic molded article. Specifically, the present invention relates to a sheet for a fiber-reinforced plastic molded article having a fiber orientation parameter (fp) of a reinforcing fiber in a thickness direction and a plane direction in a specific range.

  Non-woven fabrics (also referred to as sheets for fiber-reinforced plastic moldings) containing reinforcing fibers such as carbon fibers and glass fibers are heated and pressurized, and molded fiber-reinforced plastic moldings have already been used in various sports, leisure and aircraft materials. Used in various fields. A thermosetting resin such as an epoxy resin, an unsaturated polyester resin, or a phenol resin is often used as a matrix resin in these fiber-reinforced plastic molded articles. However, when a thermosetting resin is used, the nonwoven fabric in which the thermosetting resin and the reinforcing fiber are mixed must be stored in a refrigerator, and there is a disadvantage that long-term storage cannot be performed.

  For this reason, in recent years, fiber reinforced nonwoven fabrics containing a reinforcing fiber using a thermoplastic resin as a matrix resin have been developed. A fiber-reinforced nonwoven fabric using such a thermoplastic resin as a matrix resin has advantages that storage management is easy and long-term storage is possible. Further, the nonwoven fabric containing the thermoplastic resin has an advantage that the molding process is easier than the nonwoven fabric containing the thermosetting resin, and the molded product can be formed by performing the heat and pressure treatment. ing.

  Heretofore, thermoplastic resins which are inferior to thermosetting resins in chemical resistance, strength and the like have been mainly used. However, in recent years, thermoplastic resins excellent in heat resistance, chemical resistance, etc. have been actively developed, and the above-mentioned drawbacks which have been common knowledge about thermoplastic resins have been remarkably improved. I have. Such a thermoplastic resin is a resin called “engineering plastic (engineering plastic)”, and includes polycarbonate (PC), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyamideimide (PAI), and polyetherimide. (PEI) and the like (for example, Non-Patent Document 1).

  Carbon fibers, glass fibers, aramid fibers, and the like are used as the reinforcing fibers. Such reinforcing fibers serve to increase the strength of the fiber-reinforced plastic molding. In addition, it is known that the strength of a fiber-reinforced plastic molded article has directionality by adjusting the orientation direction of the reinforcing fiber to a specific direction (for example, Patent Documents 1 to 6). Such a fiber-reinforced plastic molded article is used for a reinforcing core material such as a bumper beam of an automobile, and a structural component requiring mechanical strength in one direction.

JP-A-5-44188 JP-A-9-41280 JP-A-6-155495 JP-A-4-208405 JP-A-4-208406 JP-A-4-208407

"2007 Survey Report on the Application of Thermoplastic Resin Composite Materials to the Machine Industry", Next Generation Metals and Composite Materials R & D Association, Japan Machinery Federation, March 2008

  As described above, in the sheet for a fiber-reinforced plastic molded article obtained by the conventional technique, the strength of the fiber-reinforced plastic molded article can be given a certain degree of directionality by orienting the reinforcing fibers in one direction. However, in recent years, there has been a demand for a fiber-reinforced plastic molded article having an increased strength in one direction, and in such a fiber-reinforced plastic molded article, the bending strength of the entire fiber-reinforced plastic molded article tends to be insufficient. It was a problem because it could be seen. For this reason, there has been a demand for the development of a fiber-reinforced plastic molded article having a mechanical strength increased in a specific direction, and having an increased bending strength of the entire fiber-reinforced plastic molded article.

  Therefore, the present inventors, in order to solve such problems of the prior art, a fiber-reinforced plastic molded body in which strength in a specific direction is sufficiently increased, the bending strength of the entire fiber-reinforced plastic molded body is high. The study was conducted for the purpose of providing a sheet for a fiber-reinforced plastic molded article capable of molding a fiber-reinforced plastic molded article.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that, in a reinforcing fiber and a sheet for a fiber-reinforced plastic molded article containing a thermoplastic resin, the fiber of the reinforcing fiber in the thickness direction and the planar direction is used. By setting the orientation parameter (fp) in a specific range, it has been found that the strength in a specific direction can be sufficiently increased and a fiber-reinforced plastic molded article having excellent bending strength can be formed.
Specifically, the present invention has the following configuration.

[1] A sheet for a fiber-reinforced plastic molding containing a reinforcing fiber and a thermoplastic resin, wherein the absolute value of the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction of the sheet for the fiber-reinforced plastic molding is 0. A sheet for a fiber-reinforced plastic molded article having a fiber orientation parameter (fp) in the plane direction of 5 to 1.0 and an absolute value of 0.25 to 1.0.
[2] The sheet for a fiber-reinforced plastic molded article according to [1], wherein the thermoplastic resin is a thermoplastic resin fiber.
[3] The fiber-reinforced plastic according to [1] or [2], further including a binder component, wherein the binder component is included in an amount of 0.1 to 10% by mass relative to the total mass of the sheet for a fiber-reinforced plastic molded article. Sheet for molded body.
[4] The sheet for a fiber-reinforced plastic molded article according to [3], wherein the binder component contains polyethylene terephthalate or modified polyethylene terephthalate fibers.
[5] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [4], wherein the mass average fiber length of the reinforcing fibers is 3 to 100 mm.
[6] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [5], wherein the reinforcing fibers are at least one selected from glass fibers, carbon fibers, and aramid fibers.
[7] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [6], wherein the reinforcing fiber is a carbon fiber having a single fiber strength of 4600 MPa or more.
[8] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [7], wherein the thermoplastic resin is at least one selected from polyetherimide fibers, polycarbonate fibers, polyamide fibers, and polypropylene fibers.
[9] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [8], wherein the thermoplastic resin is a polypropylene fiber.
[10] The sheet for a fiber-reinforced plastic molded article according to [9], wherein the polypropylene fiber is an acid-modified polypropylene fiber.
[11] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [8], wherein the thermoplastic resin is a nylon fiber.
[12] The sheet for a fiber-reinforced plastic molded article according to [11], wherein the nylon fiber is a nylon 6 fiber.
[13] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [12], wherein the reinforcing fibers and the thermoplastic resin are chopped strands.
[14] The sheet for a fiber-reinforced plastic molded article according to any one of [1] to [13] is formed by pressurizing and heating at a temperature not lower than the melting point or glass transition temperature of the thermoplastic resin. An absolute value of a fiber orientation parameter (fp) of a reinforcing fiber in a thickness direction of the fiber-reinforced plastic molded article in a thickness direction of the fiber-reinforced plastic molded article is 0.5 to 1.0, and a fiber orientation parameter (fp) of a planar direction is provided. Is a fiber-reinforced plastic molded product having an absolute value of 0.25 to 1.0.
[15] The fiber-reinforced plastic molded article according to [14], wherein the bending strength in the first direction of the fiber-reinforced plastic molded article and the bending strength in the second direction orthogonal to the first direction are 2.5 or more. .
[16] The fiber-reinforced plastic molded article according to [14] or [15], wherein the fiber-reinforced plastic molded article is formed by heating and pressing at a temperature of 150 to 600 ° C.
[17] The fiber-reinforced plastic molded article according to any one of [14] to [16], wherein the thickness is greater than 40 µm and not more than 100 µm.
[18] The fiber-reinforced plastic molded article according to any one of [14] to [16], wherein the thickness is greater than 20 µm and equal to or less than 40 µm.
[19] The fiber-reinforced plastic molded article according to any one of [14] to [18], and a core material having a density of 0.2 to 0.9 g / cm ³ ,
A laminate in which the fiber-reinforced plastic molded body is adhered to both surfaces of the core material.
[20] A step of wet-papermaking a slurry obtained by mixing a reinforcing fiber and a thermoplastic resin fiber, wherein the step of wet-papermaking is a step of papermaking using an inclined-type paper machine. And a method for producing a sheet for a fiber-reinforced plastic molded article which travels so that the jet wire ratio is 0.98 or less.
[21] The method for producing a sheet for a fiber-reinforced plastic molded article according to [20], wherein the wire of the inclined paper machine travels so that a jet wire ratio becomes 0.90 or less.
[22] The method for producing a sheet for a fiber-reinforced plastic molded article according to [20] or [21], wherein the viscosity of the dispersion medium of the slurry at 25 ° C is more than 1.00 mPa and not more than 4.00 mPa.

  ADVANTAGE OF THE INVENTION According to this invention, the intensity | strength of a specific direction is sufficiently raised and the sheet | seat for fiber reinforced plastic molded articles which can shape | mold the fiber reinforced plastic molded article which has excellent bending strength can be obtained. The fiber-reinforced plastic molded article molded from the sheet for a fiber-reinforced plastic molded article of the present invention is preferably used for structural parts or the like that require mechanical strength in one direction.

FIG. 1 is an image diagram of a cross-section observation test piece for measuring a fiber orientation parameter of a sheet for a fiber-reinforced plastic molded product of the present invention. FIG. 2 is a diagram for explaining the configuration of the inclined paper machine used in the embodiment.

  Hereinafter, the present invention will be described in detail. The description of the components described below may be made based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In addition, in this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

(Sheet for fiber-reinforced plastic molding)
The present invention relates to a sheet for a fiber-reinforced plastic molded article containing a reinforcing fiber and a thermoplastic resin. In the present invention, the absolute value of the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction in the sheet for a fiber-reinforced plastic molded product is 0.5 to 1.0, and the absolute value of the fiber orientation parameter (fp) in the planar direction. Is 0.25 to 1.0.

  In the present specification, the fiber orientation parameter (fp) of the reinforcing fiber is a parameter representing the orientation state of the reinforcing fiber in the sheet for a fiber-reinforced plastic molded article. The fiber orientation parameter (fp) is a parameter representing the fiber orientation distribution by a numerical value of -1.0 to 1.0. When fp = -1.0 and fp = 1.0, the reinforcing fibers are oriented in one direction. When fp = 0.0, it means that the reinforcing fibers are completely randomly arranged.

In the present invention, the absolute value of the fiber orientation parameter (fp) of the reinforcing fibers in the thickness direction in the sheet for a fiber-reinforced plastic molded article may be 0.5 to 1.0. The absolute value of the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction is preferably 0.6 to 1.0, more preferably 0.7 to 1.0, and 0.8 to 1.0. More preferably, it is 0. The absolute value of the fiber orientation parameter (fp) in the plane direction in the sheet for a fiber-reinforced plastic molded product may be 0.25 to 1.0, preferably 0.30 to 1.0, and 0.1 to 1.0. It is more preferably from 4 to 1.0, and further preferably from 0.60 to 1.0. As described above, in the sheet for a fiber-reinforced plastic molded article of the present invention, it is preferable that the orientation of the reinforcing fibers in the thickness direction and the orientation in the planar direction are constant.
In addition, the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction and the planar direction in the sheet for a fiber-reinforced plastic molded article can be controlled by appropriately selecting, for example, a method for producing the sheet for a fiber-reinforced plastic molded article. It is possible.

(Calculation of fiber orientation parameter in thickness direction)
When measuring the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction in the sheet for a fiber-reinforced plastic molded article, the epoxy resin for embedding which is generally used for electron microscopic observation is added to the sheet for the fiber-reinforced plastic molded article. To prepare a test piece for cross-sectional observation. Here, the reason for impregnating the embedding epoxy resin is to prevent the orientation direction of the fiber from being changed by the shearing force at the time of cutting when a cross section to be described later is cut out. As the embedding resin, a resin having sufficient strength and hardness to withstand a shearing force, such as an epoxy resin or a styrene resin, is preferable. However, in the present invention, the fiber orientation of the reinforcing fibers in the thickness direction is controlled by using an epoxy resin. Measure the parameter (fp). As the embedding resin, for example, Aronix LCA D-800 manufactured by JEOL Ltd. can be exemplified. In the case of a thermosetting resin or a resin that generates heat at the time of curing, the adhesive force between the reinforcing fibers of the binder in the sheet for a fiber-reinforced plastic molded article decreases due to the heat at the time of curing, and the angle of the reinforcing fibers changes. there is a possibility. For this reason, it is preferable to use a resin that does not become a heat source at the time of curing, such as a photocurable epoxy resin such as an ultraviolet ray.
As a method of embedding the resin, a method generally used in electron microscope observation or optical microscope observation can be employed. Specifically, the sheet for a fiber-reinforced plastic molded body is cut into a width of 5 mm and a length of 10 mm, and the above-described epoxy resin for embedding is dropped and impregnated until at least the entire surface of the test piece is covered, and is cured. The dropping of the epoxy resin for embedding can be performed using, for example, a dropper.

  FIG. 1 is a conceptual diagram of a cross-section observation test piece obtained by impregnating a sheet for a fiber-reinforced plastic molded body with an ultraviolet-curable epoxy resin for embedding. As shown in FIG. 1A, the cross-section observation test piece 45 includes the reinforcing fiber 20 and the thermoplastic resin 25 constituting the sheet 5 for the fiber-reinforced plastic molded article, and the epoxy resin 40 for embedding. I do. In the cross-section observation test piece 45, the positional relationship and the shape of the reinforcing fibers 20 and the thermoplastic resin 25 are the same as those in the sheet 5 for a fiber-reinforced plastic molded body. That is, in the cross-section observation test piece 45, the embedding epoxy resin 40 is present so as to maintain the positional relationship and the shape of the reinforcing fiber 20 and the thermoplastic resin 25.

  Although the thermoplastic resin 25 is shown in a fiber shape in FIG. 1A, the thermoplastic resin 25 may not be actually a fiber shape but may be a particle shape or the like. When the thermoplastic resin 25 has a fibrous shape as shown in FIG. 1A, the thermoplastic resin 25 has a shape similar to that of the reinforcing fiber 20, and it seems that it is indistinguishable. However, when observing the orientation state of the reinforcing fibers, it is possible to observe the orientation of only the reinforcing fibers by utilizing a difference in fiber diameter, a difference in fiber color, elemental mapping, and the like.

When observing the fiber orientation in the thickness direction, a test piece having a width of 0.3 to 0.6 mm is cut out from the test piece for cross-sectional observation, and the cross section in the thickness direction of the obtained test piece is observed with an optical microscope. As a method of cutting out, a method of vertically cutting with a thin sharp blade such as a safety razor or a surgical scalpel can be adopted. However, since it is difficult to obtain a vertical cross section by manual operation, a film slicer for cutting out sections for FT-IR measurement or an ion slicer for cutting out sections for observation with an electron microscope can be used. The film slicer is exemplified by Slice Master HS-1 manufactured by JASCO Corporation, and the ion slicer is exemplified by EM-09100IS manufactured by JEOL Ltd. Here, the cutting direction of the test piece is a direction parallel to a reference line in a plane direction obtained by a method described later. A microscope manufactured by KEYENCE CORPORATION is used as an optical microscope, and the fibers are observed at a magnification that allows a monofilament to be visually recognized. When the reinforcing fiber is not a transparent fiber (for example, a carbon fiber or the like), the reinforcing fiber can be observed with transmitted light. In the present embodiment, for example, the magnification can be selected from 300 times, 600 times, and 800 times. In addition, the observation of the reinforcing fiber is performed by focusing on a portion having a depth of 10 μm or more from each of the observation surface and the opposite surface of the test piece. In addition, you may cut out a test piece using a microtome.
In the present invention, by embedding with an epoxy resin and cutting out a cross section in the thickness direction, it is possible to prevent the angle of the fiber from being changed by the shearing force at the time of cutting.

  When the reinforcing fibers are opaque fibers such as carbon fibers, the orientation direction of the reinforcing fibers can be observed depending on the difference in chromaticity of the fibers when observed with an optical microscope. For example, when carbon fibers are observed, black fibers can be observed as reinforcing fibers.

  When a transparent reinforcing fiber such as a glass fiber is used, the interface between the reinforcing fiber and the resin may not be clearly visible even when observed with an optical microscope as described above. In that case, the fiber reinforced plastic molded sheet is embedded with an epoxy resin in the same manner as described above, and cut out so that the cross section of the test piece for cross section observation is exposed. Can be observed. In this case, the element to be mapped is an element that is contained only in the reinforcing fiber and does not contain the thermoplastic resin and the epoxy resin. For example, in a glass fiber, the Si or Ca element can be mapped by an electron microscope equipped with an energy dispersive X-ray analysis (EDS / EDX: Energy Dispersive X-Ray Spectroscopy) device to measure the fiber orientation. . An example of such an apparatus is a desktop scanning electron microscope “PROX” manufactured by Phenom World, the Netherlands.

The orientation direction of the reinforcing fiber is the major axis direction of the reinforcing fiber. Further, in the cross section in the thickness direction, the reinforcing fibers may be confirmed to be elliptical. When the reinforcing fiber is confirmed to be elliptical, the major axis direction of the ellipse is defined as the orientation direction of the fiber. The orientation angle θi of the reinforcing fiber is an angle formed by the orientation direction (orientation line) of the selected reinforcing fiber with respect to the reference line. In the present invention, a cross section in the thickness direction of the test piece is observed with an optical microscope or the like under the above conditions, and a continuous measurement area of 1.5 mm ² arbitrarily selected from the cross sections is observed. The orientation angles θi of all visible reinforcing fibers (the number of fibers is assumed to be n) existing in the sample are measured. The orientation angle θi is obtained by measuring an angle in a clockwise direction with respect to a reference line, and is set to an angle of 0 ° or more and less than 180 °.

The fiber orientation parameter (fp, hereinafter also referred to as fp value) in the thickness direction can be calculated from the orientation angle θi measured by the above method using the following equation (1).
fp = 2 × Σ (cos ² θ _i / n) −1 Equation (1)
Here, θ _i is the orientation angle (i = 1 to n) of the selected reinforcing fiber with respect to the reference line.

Here, the reference line can be determined by the following method.
When setting the reference line, first, the provisional reference line p is selected, and the angles of all the visible reinforcing fibers n existing in the measurement area are measured. In this case, the angle between the temporary reference line p and each fiber is represented by α (p) _i (i = 1 to n).
The fiber orientation parameter (fp (p)) with the provisional reference line p can be calculated using the following equation.
fp (p) = 2 × Σ (cos ² α (p) _i / n) −1
(I = 1, 2, 3,..., N)
Next, a temporary reference line (p _{+ z} , p- _z (z = 1 to 90)) obtained by rotating the temporary reference line p by ± 1 ° until it becomes ± 90 ° is taken, and a temporary reference line p _{+ z} And the angle between the temporary reference line p- _z and the n fibers are calculated. The angle in this case is represented by α (p _{+ z} ) _i and α (p− _z ) _i (i = 1 to n).
The rotated provisional reference lines (p _{+ z} , p- _z (z = 1 to 90)) and the fiber orientation parameter (fp (p ± _z )) of the reinforcing fibers can be calculated using the following formula.
fp (p ± _z ) = 2 × Σ (cos ² α (p ± _z ) _i / n) −1
(I = 1, 2, 3,..., N)
In this manner, the temporary reference line set when the maximum value is obtained among the absolute values of the obtained fp (p) value and fp (p ± _z ) value can be used as the reference line P. The fiber orientation parameter calculated from the reference line P thus determined can be used as the fiber orientation parameter (fp) in the thickness direction.

FIG. 1B is a conceptual cross-sectional view in which the cross-section observation test piece 45 shown in FIG. 1A is cut out in the BB ′ direction and the thickness direction is the vertical direction. The BB ′ direction is preferably a direction parallel to the direction in which most of the fibers are oriented. That is, the BB ′ direction is a direction parallel to a reference line in a plane direction obtained by a method described later.
In FIG. 1B, the reference line determined by the above method is a dotted line represented by P, and the orientation of each reinforcing fiber is represented by a dotted line of Q and R. In FIG. 1 (b), the dotted line P ′ is a line parallel to the reference line, and is used to easily explain the angle between the reference line P and the orientation lines (Q and R) of each reinforcing fiber. It is an auxiliary line. In FIG. 1B, since the angle (orientation angle θ ₁ ) between P ′ and Q is 0 °, P ′ and Q overlap. The angle (orientation angle θ ₂ ) between P ′ and R is represented as θ ₂ . Thus, θ ₁ to θ _n are measured. In FIG. 1B, only the reinforcing fibers are shown in order to easily confirm the orientation state of the reinforcing fibers.

In addition, as a portion for measuring the fiber orientation parameter (fp) or the temporary reference line and the fiber orientation parameter (fp (p ± _z )) of the reinforcing fiber, avoid the end of the cross section in the thickness direction of the test piece for cross section observation, Preferably, it is near the center. Specifically, it is preferable to set the measurement area so as to avoid an area of 5% (5% with respect to the thickness of the cross-section observation test piece) in the thickness direction from both ends of the cross-section observation test specimen.

(Calculation of fiber orientation parameter in plane direction)
On the other hand, the measurement of the fiber orientation parameter in the planar direction in the sheet for a fiber-reinforced plastic molded body can be measured without particularly performing a treatment such as embedding in a resin. Specifically, a sheet for a fiber-reinforced plastic molded body cut into a length of 3 cm and a width of 3 cm is placed on a slide glass, the slide glass is further placed from above, and observation is performed using a microscope with ordinary reflected light measurement. can do.
In the present invention, one surface of a test piece sandwiched between slide glasses is observed with an optical microscope. A microscope manufactured by KEYENCE CORPORATION is used as an optical microscope, and the fiber is observed with a reflected light or a combined use of the reflected light and the transmitted light with a magnification that allows the monofilament to be visually recognized. In the present embodiment, for example, the magnification can be selected from 300 times, 600 times, and 800 times. Thereby, a continuous measurement area of 2.0 mm ² arbitrarily selected from one surface is observed, and all visible reinforcing fibers present in this measurement area (the number of fibers is m). Is measured. The orientation angle θi is obtained by measuring an angle in a clockwise direction with respect to the reference line and is set to an angle of 0 ° or more and less than 180 °. The fiber orientation parameter (fp, hereinafter also referred to as fp value) can be calculated from the orientation angle θi measured by the above method using the following equation (2).
fp = 2 × Σ (cos ² θ _i / m) −1 Equation (2)
Here, i = 1 to m.
Then, the same measurement is performed for the opposite surface, and the average value of the one surface and the opposite surface is obtained, and this is defined as the fiber orientation parameter (fp) in the planar direction. The measurement region on one surface and the measurement region on the opposite surface are, for example, regions that overlap in plan view. Also, in observation of either one surface or the opposite surface, for example, it is possible to focus on a portion having a depth of 10 μm or more from each of the one surface and the opposite surface.

The reference line for measuring the fiber orientation parameter in the planar direction can be determined by the following method.
When setting the reference line, first, the provisional reference line p is selected, and the angles of all visible m fibers in the measurement area are measured. In this case, the angle between the temporary reference line p and each fiber is represented by α (p) _i (i = 1 to m).
The fiber orientation parameter (fp (p)) with the provisional reference line p can be calculated using the following equation.
fp (p) = 2 × Σ (cos ² α (p) _i / m) −1
(I = 1, 2, 3,..., M)
Next, a temporary reference line (p _{+ z} , p- _z (z = 1 to 90)) obtained by rotating the temporary reference line p by ± 1 ° until it becomes ± 90 ° is taken, and a temporary reference line p _{+ z} And the angle between the temporary reference line p- _z and the m fibers are calculated. The angle in this case is represented by α (p _{+ z} ) _i and α (p− _z ) _i (i = 1 to m).
The rotated provisional reference lines (p _{+ z} , p- _z (z = 1 to 90)) and the fiber orientation parameter (fp (p ± _z )) of the reinforcing fibers can be calculated using the following formula.
fp (p ± _z ) = 2 × Σ (cos ² α (p ± _z ) _i / m) −1
(I = 1, 2, 3,..., M)
In this way, the temporary reference line set when the maximum value is obtained among the obtained fp (p) value and fp (p ± _z ) value can be set as the reference line P. The fiber orientation parameter calculated from the reference line P thus determined can be used as the fiber orientation parameter (fp) in the planar direction.

  The reinforcing fibers may be oriented in any of the plane directions of the sheet for a fiber-reinforced plastic molded article, but must be oriented in the MD direction (flow direction of a papermaking line) of the sheet for a fiber-reinforced plastic molded article. Is preferred.

  In the fiber-reinforced plastic molded body obtained by molding the sheet for a fiber-reinforced plastic molded body as described above, the bending strength in one direction is enhanced. In particular, when the reinforcing fibers are oriented in the MD direction, the strength in the MD direction is increased in the fiber-reinforced plastic molded article. Furthermore, in the fiber reinforced plastic molded article obtained by molding the sheet for a fiber reinforced plastic molded article as described above, the overall bending strength of the fiber reinforced plastic molded article is also increased.

In the present invention, the fact that the absolute value of the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction and the planar direction is within the above range means that the orientation of the reinforcing fiber in the thickness direction and the planar direction in the sheet for a fiber-reinforced plastic molded article. It means that the direction is constant. That is, in the sheet for a fiber-reinforced plastic molding, the reinforcing fibers are oriented in one direction. And also in the fiber reinforced plastic molded article molded from such a sheet for a fiber reinforced plastic molded article, the reinforcing fibers are oriented in one direction.
In the sheet for a fiber-reinforced plastic molded article or the fiber-reinforced plastic molded article, the fact that the orientation of the reinforcing fiber in the thickness direction is a fixed direction means that the reinforcing fiber is a sheet for a fiber-reinforced plastic molded article or a fiber-reinforced plastic molded article. It means that it is oriented parallel to the surface (papermaking surface).

  In the sheet for a fiber-reinforced plastic molding of the present invention, the compounding ratio of the reinforcing fibers is preferably 20 to 83% by mass. By setting the blending ratio of the reinforcing fibers within the above range, the number of fibers oriented in a specific direction can be increased. As a result, the distance between the reinforcing fibers is shortened, the packing density of the reinforcing fibers after the heat and pressure molding is increased, and the strength of the fiber-reinforced plastic molded body can be effectively increased.

  Further, the mass ratio of the reinforcing fibers to the thermoplastic resin in the sheet for a fiber-reinforced plastic molded product is preferably from 1: 0.2 to 1:10, and more preferably from 1: 0.5 to 1: 5. More preferably, it is 1: 0.7 to 1: 3. By setting the mass ratio of the reinforcing fiber to the thermoplastic resin within the above range, a lightweight and high-strength fiber-reinforced plastic molded body can be molded.

  For the sheet for a fiber-reinforced plastic molded product, JAPAN TAPPI Paper Pulp Test Method No. The air permeability defined in 5-2 is preferably 250 seconds or less, more preferably 230 seconds or less, and even more preferably 200 seconds or less. This numerical value indicates that the smaller the numerical value, the easier the air passes (the better the air permeability). In the present invention, by setting the air permeability of the sheet for a fiber-reinforced plastic molding within the above range, the molding speed in the heating and pressing step can be increased, and the production efficiency can be increased.

(Reinforced fiber)
The reinforcing fibers are preferably at least one selected from glass fibers, carbon fibers and aramid fibers. One type of these reinforcing fibers may be used, or a plurality of types may be used. Further, organic fibers having excellent heat resistance such as PBO (polyparaphenylenebenzoxazole) fibers may be contained.

As the reinforcing fibers, for example, when inorganic fibers such as carbon fibers and glass fibers are used, the fiber-reinforced plastic molded body is heated and pressurized at the melting temperature of the thermoplastic resin contained in the sheet for the fiber-reinforced plastic molded body. It can be formed.
Further, when an organic fiber such as aramid is used as the reinforcing fiber, generally, the wear resistance can be improved more than a molded article formed from a sheet for a fiber-reinforced plastic molded article using inorganic fibers as the reinforcing fiber. .

The mass average fiber length of the reinforcing fibers is preferably from 3 to 100 mm, more preferably from 3 to 75 mm, further preferably from 3 to 50 mm, and particularly preferably from 6 to 50 mm. By setting the fiber length of the reinforcing fibers within the above range, it is possible to prevent the reinforcing fibers from falling off from the sheet for a fiber-reinforced plastic molded article, and to form a fiber-reinforced plastic molded article having excellent strength. Becomes possible. Further, by setting the fiber length of the reinforcing fibers within the above range, the dispersibility of the reinforcing fibers can be improved. Thereby, the fiber-reinforced plastic molded product after the heat and pressure molding has good strength and appearance.
In addition, in this specification, a mass average fiber length is an average value of the fiber length measured about 100 fibers.

The fiber diameter of the reinforcing fibers is not particularly limited as an average fiber diameter, but generally, fibers having a fiber diameter of about 5 to 25 μm are preferably used for both carbon fibers and glass fibers. Further, a plurality of materials and shapes may be used in combination for the reinforcing fibers.
In addition, in this specification, an average fiber diameter is an average value when measuring the fiber diameter of 100 fibers.

(Carbon fiber)
It is preferable to use carbon fibers as the reinforcing fibers. As the carbon fibers contained in the reinforcing fibers, carbon fibers such as polyacrylonitrile (PAN), petroleum / coal pitch, rayon, and lignin can be used. One type of these carbon fibers may be used alone, or two or more types may be used in combination. Further, among these carbon fibers, it is preferable to use polyacrylonitrile (PAN) -based carbon fibers from the viewpoint of productivity and mechanical properties on an industrial scale.

  The mass average fiber length of the carbon fibers is preferably from 3 to 100 mm, more preferably from 3 to 75 mm, further preferably from 3 to 50 mm, and particularly preferably from 6 to 50 mm. By setting the fiber length of the carbon fibers within the above range, it is possible to suppress the carbon fibers from falling off from the sheet for a fiber-reinforced plastic molded article, and to form a fiber-reinforced plastic molded article having excellent strength. Becomes possible. By setting the fiber length of the carbon fiber within the above range, the dispersibility of the reinforcing fiber can be improved. Thereby, the fiber-reinforced plastic molded product after the heat and pressure molding has good strength and appearance.

  The single fiber strength of the carbon fiber is preferably 4500 MPa or more, more preferably 4600 MPa or more, and further preferably 4700 MPa or more. The single fiber strength refers to the tensile strength of a monofilament. When such a carbon fiber is used, the bending strength is greatly improved by a synergistic effect with the effect of the fiber orientation of the reinforcing fiber described above. The single fiber strength can be measured according to JIS R7601 “Carbon fiber test method”.

  The fiber diameter of the carbon fiber is not particularly limited, but is generally preferably 5 to 20 μm. By setting the fiber diameter of the carbon fiber within the above range, the strength of the fiber-reinforced plastic molded body can be increased.

(Thermoplastic resin)
The thermoplastic resin forms binding points at the intersections of the matrix or the fiber components during the heat and pressure treatment. Such a sheet for a non-woven fiber-reinforced plastic molded article using a thermoplastic resin does not require autoclave treatment and has a shorter heating / pressing molding time during processing than a sheet using a thermosetting resin. Saves time and increases productivity.

  The thermoplastic resin is preferably a thermoplastic resin fiber. Examples of thermoplastic resin fibers include polycarbonate (PC), polyetheretherketone (PEEK), polyamideimide (PAI), polyphenylenesulfide (PPS), polyetherimide (PEI), polyetherketoneketone (PEKK), polyamide, and polypropylene. And the like. Among them, it is preferable to use polycarbonate, polyetherimide, or polyamide in order to obtain a fiber-reinforced plastic molding having good fiber dispersibility and high strength. The polyamide is preferably nylon, and more preferably nylon 6.

  In the present invention, it is also preferable to use a polypropylene fiber as the thermoplastic resin because the molding process is facilitated because of its low cost and low melting point. Further, when polypropylene is used as the matrix resin, the polypropylene is preferably an acid-modified polypropylene. When the modified polypropylene is used, the adhesiveness between the modified polypropylene and the reinforcing fibers is improved, so that the bending strength and the elastic modulus of the fiber-reinforced plastic molded article are improved. The acid-modified polypropylene is preferably an acid group-containing polyolefin, and the acid group-containing polyolefin is not particularly limited, but it is preferable to use an acid-modified polypropylene having a polar group. For example, polypropylene copolymerized with a monomer containing a carboxyl group can be used. The monomer containing a carboxyl group is not particularly limited, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, sorbic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid And dicarboxylic acids such as itaconic anhydride and citraconic anhydride. The polypropylene to be copolymerized may be a propylene homopolymer or a propylene copolymer. Examples of the propylene copolymer include a random copolymer of propylene and an α-olefin, and a block copolymer of propylene and another olefin. Examples of the α-olefin include ethylene, 1-butene, 1-pentene, and the like. Specifically, a propylene-ethylene random copolymer or the like can be used as the propylene copolymer. Among them, a propylene homopolymer is preferable because it is available at low cost, has a high melting point, and is excellent in impact resistance. The method of copolymerization is not particularly limited, and for example, random copolymerization, block copolymerization, graft copolymerization and the like can be used. From the viewpoint that a carboxyl group easily appears on the surface when formed into a fiber, graft copolymerization is preferred. From the viewpoint of a large amount of carboxyl groups, the acid-modified polypropylene is preferably at least one selected from the group consisting of maleic acid-modified polypropylene and maleic anhydride-modified polypropylene. The acid-modified polypropylene may be used alone or in combination of two or more.

The thermoplastic resin preferably has a limiting oxygen index of 24 or more, more preferably 27 or more in a fibrous state. By setting the limiting oxygen index of the thermoplastic resin within the above range, a sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article having excellent flame retardancy can be obtained. In the present invention, the “limit oxygen index” indicates an oxygen concentration necessary for continuing combustion, and refers to a numerical value measured by a method described in JIS K7201. That is, when the limiting oxygen index is 20 or less, it is a numerical value indicating that combustion takes place in normal air.
Further, the amount of smoke generated during 20 minutes of combustion of the thermoplastic resin measured by the method described in ASTM E-662 is preferably about 30 ds, and a sheet for a fiber-reinforced plastic molded article having a very small amount of smoke can be obtained. it can.

  The glass transition temperature of the thermoplastic resin is preferably 140 ° C. or higher. The thermoplastic resin is required to be sufficiently fluid under a temperature condition of 300 ° C. to 400 ° C. when forming a fiber-reinforced plastic molded body. In addition, even if it is a super engineering plastic fiber having a glass transition temperature of less than 140 ° C., such as a PPS resin fiber, a fiber made of a super engineering plastic having a resin deflection temperature of 190 ° C. or more can be used. Such a thermoplastic resin is melted by heating and pressurizing to form a very flame-retardant resin block having a critical oxygen index of 30 or more.

  The mass average fiber length of the thermoplastic resin fiber is preferably from 2 to 100 mm, more preferably from 2 to 50 mm, further preferably from 3 to 50 mm, particularly preferably from 3 to 40 mm, More preferably, it is 3 to 25 mm. By setting the fiber length of the thermoplastic resin fiber within the above range, it is possible to suppress the thermoplastic resin fiber from falling off from the sheet for the fiber reinforced plastic molded article, and to provide a fiber reinforced plastic molded article excellent in handleability. You can get a sheet. Further, by setting the fiber length of the thermoplastic resin within the above range, the dispersibility of the thermoplastic resin fibers can be improved, so that it is possible to form a fiber-reinforced plastic molded article having excellent strength. . Thereby, the fiber-reinforced plastic molded product after the heat and pressure molding has good strength and appearance.

In the sheet for a fiber-reinforced plastic molding used in the present invention, voids are present in the sheet because the thermoplastic resin is in a fiber form.
In the present invention, since the thermoplastic resin maintains the fiber form before heat-press molding, the sheet itself is flexible and drapable before forming the fiber-reinforced plastic molded body. For this reason, the sheet for a fiber-reinforced plastic molding can be stored and transported in a wound form, and has a feature of excellent handling properties.

[Mass ratio of reinforcing fiber to thermoplastic resin]
In the sheet for a fiber-reinforced plastic molded article of the present invention, the mass ratio of the reinforcing fiber to the matrix resin fiber is preferably from 10:90 to 80:20, more preferably from 20:80 to 70:30, and more preferably from 30:80 to 70:30. : 70 to 70:30. By setting the mass ratio of the reinforcing fiber to the matrix resin fiber within the above range, a lightweight and high-strength fiber-reinforced plastic molded product can be obtained.

(Binder component)
The sheet for a fiber-reinforced plastic molded article of the present invention preferably further contains a binder component. The binder component is preferably contained in an amount of 0.1 to 10% by mass relative to the total mass of the fiber-reinforced plastic layer, more preferably 0.3 to 10% by mass, and 0.4 to 10% by mass. The content is more preferably 9% by mass, and particularly preferably 0.5 to 8% by mass. By setting the content of the binder component within the above range, the strength during the manufacturing process can be increased, and the handling property can be improved. In addition, when the amount of the binder component increases, both the surface strength and the interlayer strength increase, but on the contrary, the problem of the odor at the time of heat molding tends to occur. However, within the above range, a sheet for a fiber-reinforced plastic molded article which hardly causes odor problems and does not cause delamination or the like even after repeated cutting steps can be obtained.

  Examples of the binder component include polyester resins such as polyethylene terephthalate and modified polyethylene terephthalate, acrylic resins, styrene- (meth) acrylate copolymer resins, urethane resins, PVA resins, and various types of starch, which are generally used for nonwoven fabric production. , Cellulose derivatives, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer alkaline salt, isobutylene-maleic anhydride copolymer alkaline salt, Polyvinyl acetate resin, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene- (meth) acrylate copolymer and the like can be used.

The binder component preferably contains a copolymer containing at least one of a repeating unit derived from a methyl (meth) acrylate-containing monomer and a repeating unit derived from an ethyl (meth) acrylate-containing monomer. Above all, the binder component preferably contains a copolymer containing at least one of a repeating unit derived from a methyl methacrylate-containing monomer and a repeating unit derived from an ethyl methacrylate-containing monomer. These monomers may be copolymerized with other monomers such as styrene, vinyl acetate, acrylamide and the like.
In the present invention, “(meth) acrylate” means including both “acrylate” and “methacrylate”, and “(meth) acrylic acid” means “acrylic acid” and “methacrylic acid” It is meant to include both.

Further, polyester resins and modified polyester resins are preferred as binder components in the present invention. As the polyester resin, polyethylene terephthalate (PET) is particularly preferable. The modified polyester resin is not particularly limited as long as the melting point is lowered by modifying the polyester resin, but modified polyethylene terephthalate is preferred. As the modified polyethylene terephthalate, copolymerized polyethylene terephthalate (coPET) is preferable, and examples thereof include urethane-modified copolymerized polyethylene terephthalate. The polyester resin is preferably used because it is compatible with the thermoplastic resin of the present invention at the time of heating and melting, so that the heat and the function of the resin are hardly impaired even after cooling.
The copolymerized polyethylene terephthalate preferably has a melting point of 140 ° C. or lower, more preferably 120 ° C. or lower. Further, a modified polyester resin as described in Japanese Patent Publication No. 1-30926 may be used. As a specific example of the modified polyester resin, particularly, "Melty 4000" (trade name, manufactured by Unitika Ltd.) (a fiber in which all fibers are copolymerized polyethylene terephthalate) is preferably mentioned. As the binder fiber having a core-sheath structure, "Melty 4080" (trade name, manufactured by Unitika), "N-720" (trade name, manufactured by Kuraray Co., Ltd.) and the like can be preferably used.

  In the present invention, the sheet for a fiber-reinforced plastic molded article is made by wet papermaking to increase the strength aspect ratio. In general, when the strength aspect ratio is increased, the fibers tend to be arranged in one direction, and the density of the nonwoven fabric tends to increase. As a result, the number of intersections between fibers in the nonwoven fabric increases, so that the amount of the binder component added can be reduced, and sufficient surface strength can be obtained even with a small amount of binder.

(Fiber shape)
In the present invention, the thermoplastic resin fibers and the reinforcing fibers are preferably chopped strands cut to a certain length. Further, it is preferable that the binder fibers are also chopped strands. By adopting such a form, various fibers can be uniformly mixed in the sheet for a fiber-reinforced plastic molded article.

  When producing the sheet for a fiber-reinforced plastic molded article of the present invention, a method of forming a web by dispersing a chopped strand of a thermoplastic resin fiber, a reinforcing fiber, and a binder fiber in a solvent and then removing the solvent (wet process) Papermaking method) is adopted.

(Fiber reinforced plastic molding)
The sheet for a fiber-reinforced plastic molded article of the present invention can be processed into an arbitrary shape in accordance with the shape of the intended molded article and the molding method. The sheet for the fiber-reinforced plastic molded body is used alone or laminated so as to have a desired thickness, and is heated and pressed by a hot press or preheated by an infrared heater or the like, and then heated and pressed by a mold. be able to. As described above, by processing the sheet for a general fiber-reinforced plastic molded body using the heat and pressure molding method, a fiber-reinforced plastic molded body having excellent strength can be obtained.

  The present invention relates to a fiber-reinforced plastic molded article formed by subjecting a sheet for reinforcing fiber and a fiber-reinforced plastic molded article containing a thermoplastic resin to pressure and heat molding at a temperature not lower than the melting point or the glass transition temperature of the thermoplastic resin. It is also about. Here, the absolute value of the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction in the sheet for a fiber-reinforced plastic molded article is 0.5 to 1.0, and the absolute value of the fiber orientation parameter (fp) in the planar direction is 0.25 to 1.0.

  In the fiber-reinforced plastic molded article of the present invention, most of the reinforcing fibers are substantially parallel to the surface of the fiber-reinforced plastic molded article, and have a bending strength in the first direction and a second direction perpendicular to the first direction. The strength ratio of the bending strength in two directions is 2.5 or more.

  The thickness of the fiber-reinforced plastic molded body is not particularly limited, but is preferably thinner from the viewpoint of weight reduction when used as a housing of a mobile device or the like. Specifically, it is preferably from 0.1 to 50.0 mm, more preferably from 0.1 to 10.0 mm, even more preferably from 0.4 to 1.0 mm. The fiber-reinforced plastic molded article of the present invention has excellent strength and increased strength in a certain direction even when the thickness is within the above range.

  In the fiber-reinforced plastic molded article of the present invention, since most of the reinforcing fibers are arranged substantially parallel to the surface of the fiber-reinforced plastic molded article, breakage occurs due to the flow of the resin at the time of heating and pressing. Hateful. Therefore, a fiber-reinforced plastic molded product thinner than the above range can be molded. For example, the thickness of the fiber-reinforced plastic molded article can be set to 100 μm or less. Further, the thickness of the fiber-reinforced plastic molded article of the present invention is more than 40 μm and can be 100 μm or less. Further, the thickness of the fiber-reinforced plastic molded article of the present invention may be greater than 20 μm and 40 μm or less. It is also possible to obtain a fiber-reinforced plastic molded body having a size of 10 μm or more and 20 μm or less.

Such a fiber-reinforced plastic molded body can be suitably used as a reinforcing sheet or a tape base material for obtaining a lightweight (high-strength) member (laminated body) by bonding to both surfaces of a low-density core material. The present invention may relate to a laminate in which a fiber-reinforced plastic molded body is adhered to both surfaces of a core material.
When laminating a fiber-reinforced plastic molded body on both sides of a low-density core material, examples of the core material include non-woven fabrics containing at least one material selected from natural pulp, synthetic pulp, inorganic fibers, organic fibers, and the like. No. Further, as the core material, a heat-pressed product of the above-described nonwoven fabric, a porous body such as a foam made of a thermoplastic resin or a thermosetting resin, or the like is also preferably used.

The lower the density of the core material, the better the lightness, and the higher the density, the better the strength. From such a viewpoint, the density of the core material is preferably 0.2 to 0.9 g / cm ³ . By setting the density of the core material within the above range, a lightweight and high-strength laminate can be obtained.

  The method of bonding the core material and the fiber-reinforced plastic molded article is a method of applying an adhesive to the core material to bond the fiber-reinforced plastic molded article, or a method of applying an adhesive to the fiber-reinforced plastic molded article and bonding. Or a method of thermocompression bonding a core material and an adhesive, but is not limited thereto.

  When an adhesive is applied to the fiber-reinforced plastic molded product, an adhesive layer or an adhesive layer may be provided on one or both surfaces of the fiber-reinforced plastic molded product. In this case, it is also possible to improve the handleability by sticking a release paper on the adhesive layer. Since the fiber-reinforced plastic molded article of the present invention can be curved so as to have a radius of curvature as described below, when an adhesive layer is provided and a release paper is further adhered, it is transported in a wound shape. It becomes possible. Such a form is also suitable for merchandise distribution.

  Instead of the core material described above, a core of a corrugated liner or a core of a honeycomb structure may be used. In this case, the fiber-reinforced plastic molded product of the present invention can be used as a base paper for the core of the corrugated liner or a base paper for the core of the honeycomb structure.

  The fiber-reinforced plastic molded article of the present invention has excellent tensile strength because most of the reinforcing fibers are arranged substantially parallel to the surface of the fiber-reinforced plastic molded article. Therefore, when the fiber-reinforced plastic molded body is used as a reinforcing material as described above, a sufficient strength can be obtained even when the thickness of the fiber-reinforced plastic molded body is small, so that a laminate having both lightness and high strength is obtained. be able to. Further, since the fiber-reinforced plastic molded article of the present invention has excellent strength in a specific direction, it is possible to obtain a laminate in which the strength in a necessary direction is particularly increased depending on the application.

Furthermore, in the fiber-reinforced plastic molded body, most of the reinforcing fibers are arranged almost parallel to the surface of the fiber-reinforced plastic molded body. It is characterized in that cracking does not occur even if it is bent to 10 mm or less, 5 mm or less, or even 3 mm or less.
Taking advantage of this feature, it is processed into a cylindrical or spiral shape to be used as a protective material for sensors, etc., corrugated and processed into a corrugated shape, and liner sheets are stuck on both sides for lightweight and high strength It is also possible to obtain a laminate.

  In the fiber-reinforced plastic molded article, most of the reinforcing fibers are arranged substantially parallel to the surface of the fiber-reinforced plastic molded article, and thus have excellent compressive strength. Therefore, it can be suitably used also as a honeycomb processed core material.

In addition, a plate-shaped fiber-reinforced plastic molded article can be obtained by injection molding, but by obtaining a fiber-reinforced plastic molded article using the sheet for a fiber-reinforced plastic molded article of the present invention, a thin film can be obtained, and It has the advantage that no breakage or breakage occurs during molding.
When a sheet for a fiber-reinforced plastic molded article is used as in the present invention, a thin molded article can be produced by adjusting the basis weight of the sheet for a fiber-reinforced plastic molded article. In particular, in the sheet for a fiber-reinforced plastic molded article of the present invention, the reinforcing effect in the plane direction can be obtained by setting the absolute value of the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction to 0.5 or more, and the sheet is extremely thin. Even in the production of a thin molded article, there is a technical significance that tearing and breakage hardly occur during molding. Accordingly, the thickness of the fiber-reinforced plastic molded article of the present invention can be set to be larger than 40 μm and 100 μm or less. Further, the thickness of the fiber-reinforced plastic molded article of the present invention may be greater than 20 μm and 40 μm or less. It is also possible to obtain a fiber-reinforced plastic molded body having a size of 10 μm or more and 20 μm or less.

When producing the fiber-reinforced plastic molded article of the present invention, the number of laminated sheets for the fiber-reinforced plastic molded article may be one, or a plurality of laminated sheets may be heated and pressed. In other words, in order to obtain a fiber-reinforced plastic molding having a basis weight of 60 g / m ^2, 60 g / to m ² of fiber-reinforced plastic molded body sheet may be heated pressure molding, fiber reinforced plastic 20 g / m ² Three sheets of molded article may be laminated, or two sheets of 10 g / m ² fiber-reinforced plastic molded article and two sheets of 20 g / m ² fiber-reinforced plastic molded article may be laminated. Good. When the number of laminations is one or a small number, the lamination process is simplified, which is preferable in terms of production efficiency and production cost.

  On the other hand, when laminating a plurality of sheets for a fiber-reinforced plastic molded article, there is an advantage that the uniformity of the fiber-reinforced plastic molded article is improved, and pinholes and the like are hardly generated even if the sheet is thin. Furthermore, the lower the basis weight of the sheet for fiber-reinforced plastic moldings, the thinner the sheet for fiber-reinforced plastic moldings, so that the orientation of the reinforcing fibers in the thickness direction of the fiber-reinforced plastic moldings tends to be in a certain direction, Since the orientation parameter (fp) in the thickness direction easily approaches 1.0, there is an advantage that the strength of the fiber-reinforced plastic molded body is improved and the amount of deflection is reduced.

Further, when laminating a plurality of sheets for a fiber-reinforced plastic molded body, the sheets for a fiber-reinforced plastic molded body containing different types of reinforcing fibers or thermoplastic resin fibers are laminated depending on the use of the fiber-reinforced plastic molded body. You can also. For example, a sheet for a fiber-reinforced plastic molded article containing carbon fibers as reinforcing fibers and a sheet for a fiber-reinforced plastic molded article containing glass fibers as reinforcing fibers can be laminated. In this case, since carbon fiber and glass fiber have different tensile strength, elongation at break, conductivity, and thermal conductivity of the fiber, by appropriately adjusting the number of layers, strength, electromagnetic shielding properties, thermal conductivity, etc. Can be adjusted according to the application.
Further, in the case of an application in which a core material is adhered to one surface, a thermoplastic resin contained in a sheet for a fiber-reinforced plastic molded body disposed on the adhesion surface is a resin having excellent adhesion to a core material, for example, having a low melting point. It can be changed to a material having adhesiveness, a material having excellent compatibility with the components contained in the core material, and the like.

In the fiber-reinforced plastic molded product, the geometric mean value of the bending strength is preferably 350 MPa or more. The geometric mean value of the bending strength is preferably 400 MPa or more, and more preferably 450 MPa or more. As described above, since the density of the reinforcing fibers on the plane parallel to the surface of the fiber-reinforced plastic molded article is high, the fiber-reinforced plastic molded article obtained by the present invention has excellent mechanical strength.
Here, the geometric mean value of the bending strength is a geometric mean value of the bending strengths of the fiber orientation direction (MD direction) and the direction (CD direction) orthogonal to the orientation direction of the reinforcing fibers in the fiber-reinforced plastic molded article, The strength is represented by the following equation.
Geometric mean value of bending strength = √ (FMD × FCD)
Here, FMD represents bending strength in the FD direction, and FCD represents bending strength in the CD direction.

  Further, in the fiber-reinforced plastic molded body, the strength ratio of the bending strength in the first direction of the fiber-reinforced plastic molded body and the bending strength in the second direction orthogonal to the first direction may be 2.5 or more, It is preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more. Note that the first direction refers to the orientation direction of the reinforcing fibers in the fiber-reinforced plastic molded body, and the second direction refers to the direction orthogonal to the orientation direction of the reinforcing fibers. By setting the strength ratio of the fiber-reinforced plastic molded body within the above range, a fiber-reinforced plastic molded body having increased strength in a specific direction can be obtained. Such a fiber-reinforced plastic molded product is preferably used for a structural component used in automobiles, aircraft, and the like, which requires mechanical strength in one direction.

(Molding method of fiber-reinforced plastic molding)
The method for molding the sheet for a fiber-reinforced plastic molded article of the present invention is not particularly limited, and can be selected according to the use of the molded article. As a typical method, press molding is exemplified. In addition, the press molding method includes, among various press molding methods, an autoclave method often used when producing molded members such as a large aircraft, and a mold press having a relatively simple process. The method is preferably mentioned. The autoclave method is preferred from the viewpoint of obtaining a high-quality molded article with few voids. On the other hand, from the viewpoint of the amount of energy used in equipment and the molding process, the simplification of molding jigs and auxiliary materials to be used, the degree of freedom in molding pressure and temperature, a metal mold formed using a metal mold is used. It is preferable to use a mold pressing method, and these can be selected according to the application.

  As the mold pressing method, a heat and cool method or a stamping molding method can be adopted. In the heat and cool method, a sheet for a fiber-reinforced plastic molded body is placed in a mold in advance, pressurized and heated together with the mold, and then cooled while cooling the mold with the mold closed. To obtain a molded body. In the stamping molding method, the sheet is preliminarily heated by a far-infrared heater, a heating plate, a high-temperature oven, a heating device such as a dielectric heating, and the thermoplastic resin is melted and softened. This is a method in which the mold is closed, the mold is clamped, and then pressurized and cooled. When the temperature at the time of molding is relatively low, such as when a low-density molded body is obtained, a hot press method can be employed.

  Molds for molding are roughly classified into two types. One is a closed mold used for casting and injection molding and the other is an open mold used for press molding and forging. When the sheet for a fiber-reinforced plastic molding of the present invention is used, any mold can be used depending on the application. An open mold is preferable from the viewpoint of removing decomposed gas and mixed air outside the mold during molding.However, in order to suppress excessive resin outflow, the number of open portions should be reduced as much as possible during molding to minimize resin It is also preferable to adopt a shape that suppresses outflow from the mold.

  Further, a mold having at least one selected from a punching mechanism and a tapping mechanism can be used as the mold. By devising such as using a two-stage press mechanism, it is also possible to continuously punch out the molded body after hot pressing. Further, depending on the purpose of use, the molded article can be formed with projections and screw holes for reinforcing and processing the strength such as ribs and bosses, and can be provided with a pattern for the purpose of imparting designability.

  It is also possible to adhere more complicated shaped members by outsert molding or insert molding at the same time as molding the sheet for a fiber-reinforced plastic molded article, or after molding.

  When molding a fiber-reinforced plastic molded article from a sheet for a fiber-reinforced plastic molded article, specifically, it is preferable to heat-press and mold the sheet for a fiber-reinforced plastic molded article at a temperature of 150 to 600 ° C. Note that the heating temperature is preferably a temperature at which the thermoplastic resin flows and the reinforcing fiber does not melt.

  The pressure for molding the fiber-reinforced plastic molded body is preferably 5 to 20 MPa. Further, the rate of temperature rise until reaching the desired holding temperature is preferably 3 to 20 ° C./min, the holding time at the desired hot pressing temperature is 1 to 30 minutes, and then the temperature at which the molded body is taken out (200 ° C.) It is preferable to set the cooling rate at 3 to 20 ° C./min while maintaining the pressure up to the following. Further, although the production efficiency is slightly lowered, it is also preferable from the viewpoint of improving the strength that the air is cooled slowly at a rate of 0.1 to 3 ° C./min from the holding temperature of the hot press to the glass transition temperature of the matrix resin. It is also possible to carry out hot press molding using rapid heating and rapid cooling (heat and cool) molding, in which case the temperature rise and cooling rates are respectively 30 to 500 ° C./min. Further, in the case of using an infrared heater, it can be heated at a temperature of 150 to 600 ° C., preferably 200 to 500 ° C. for 1 to 30 minutes, and then molded at a pressure of 30 to 150 MPa.

(Production method of sheet for fiber-reinforced plastic molded body)
The step of producing the sheet for a fiber-reinforced plastic molded article of the present invention includes a step of wet-papermaking a slurry in which reinforcing fibers and a thermoplastic resin are mixed.

  In the step of obtaining the slurry by mixing the reinforcing fibers and the thermoplastic resin, the fibers can be sufficiently dispersed by adjusting the concentration of the dispersion and the viscosity of the solvent. The viscosity of the solvent can be adjusted by a method such as adding a polyacrylamide-based polymer. By sufficiently dispersing the fibers, the fibers in the sheet for a fiber-reinforced plastic molded article are uniformly mixed. This makes it possible to prevent, for example, the proportion of the resin from being partially increased in the fiber-reinforced plastic molded body obtained by subjecting the present sheet to heat and pressure molding, and to increase the bending strength of the fiber-reinforced plastic. In the mixing step, it is preferable to disperse the reinforcing fibers into a single fiber.

When a sheet for a fiber-reinforced plastic molded article is made, the viscosity of the dispersion medium of the slurry at 25 ° C. (provided by the measuring method prescribed in JIS Z 8803 “Method of measuring viscosity of liquid”) is 1.00 mPa. It is preferably more than 4.00 mPa · s and more preferably more than 1.05 to 2.00 mPa · s.
In addition, the slurry here means the slurry immediately before the papermaking process, and is the slurry in the inlet. When measuring the viscosity of the dispersion medium of the slurry, 500 ml of the inlet slurry is sampled, and the viscosity is measured using a filtrate obtained by filtering the fibers with a 150-mesh metal sieve.

  The viscosity of the dispersion medium of the slurry can be adjusted by adding a polyacrylamide-based viscosity agent to the inlet. By setting the viscosity of the dispersion medium of the slurry within the above range, the turbulence of the flow of the dispersion in the vicinity of the wire can be suppressed, and a laminar flow can be obtained. Thereby, the fiber orientation parameter (fp) in the thickness direction and the planar direction of the sheet for a fiber-reinforced plastic molded product can be set within a desired range.

  The wet papermaking step is preferably a papermaking step using an inclined paper machine. And it is preferable that the wire of the inclined paper machine travels so that the jet wire ratio becomes 0.98 or less. The jet wire ratio of the wire of the inclined paper machine is more preferably 0.96 or less, further preferably 0.90 or less, and particularly preferably 0.80 or less.

Here, the jet wire ratio is a ratio of a supply speed of a slurry containing a reinforcing fiber and a binder component to a wire traveling speed, and is expressed by slurry supply speed / wire traveling speed. When the jet wire ratio is greater than 1, the slurry supply speed is faster than the wire traveling speed, and this case is referred to as "push formation". When the jet wire ratio is 1 or less, the supply speed of the slurry is lower than the traveling speed of the wire, and this case is referred to as “pulling formation”.
In the present invention, the fiber orientation parameter (fp) in the thickness direction of the sheet for a fiber-reinforced plastic molded article can be within a desired range by setting the jet wire ratio in the above range and performing papermaking by “pulling formation”. . Further, the fiber orientation parameter (fp) in the planar direction of the sheet for a fiber-reinforced plastic molded product can be set within a desired range.

  It should be noted that the wet papermaking step may be a papermaking step using a round paper machine or a fourdrinier paper machine instead of the inclined paper machine. When papermaking is performed using a circular paper machine, the diameter of the circular mesh of the circular paper machine is preferably 80 cm or more. By setting the diameter of the mesh of the mesh machine to the above range, the orientation direction of the reinforcing fibers can be made one direction, and most of the reinforcing fibers are parallel to the surface of the fiber-reinforced plastic molded body. Orientation becomes easy. Thereby, the strength of the fiber-reinforced plastic molded body in a specific direction can be further increased.

  The papermaking speed in the case of performing papermaking using a round paper machine is preferably 15 m / min or more. By setting the papermaking speed to the above, the orientation direction of the reinforcing fibers can be made one direction, and it becomes easy to orient most of the reinforcing fibers so as to be parallel to the surface of the fiber-reinforced plastic molded body. Thereby, the strength of the fiber-reinforced plastic molded body in a specific direction can be further increased.

When the step of manufacturing a sheet for a fiber-reinforced plastic molded article includes a step of making a paper using an inclined paper machine, the suction force of a plurality of suction boxes provided on an inclined wire of the inclined paper machine is appropriately adjusted. Is preferred. Specifically, it is preferable to adjust the dehydration amounts of the plurality of suction boxes to the same level or to adjust the dehydration amounts of the suction boxes downstream of the inclined wire to be large. FIG. 2 is a diagram illustrating a configuration of an example of the inclined paper machine 100 that can be used in the present invention. As shown in FIG. 2, the inclined paper machine 100 includes a first suction box 101, a second suction box 102, and a third suction box below an inclined wire 120 provided at a bottom of an inlet 110. 103 and a fourth suction box 104. In such an inclined type paper machine 100, when the dehydration amount in all the suction boxes is 100, the dehydration amount of the first suction box 101 is preferably 5 to 65, preferably 20 to 60. More preferably, it is more preferably 35 to 60. When the amount of dehydration of the first suction box 101 is set to more than 25, it is preferable that the amounts of dehydration of the second to fourth suction boxes are adjusted so as to decrease sequentially.
By adjusting the amount of dehydration in this way, the orientation direction of the reinforcing fibers can be adjusted, the strength in a specific direction is increased, and a fiber-reinforced plastic molded article having excellent bending strength can be formed. .

It is preferable that the air permeability of the inclined wire of the inclined type paper machine is 250 cm ³ / cm ² / sec or more. In addition, the air permeability of the wire can be appropriately adjusted according to the viscosity of the dispersion medium of the slurry in the inlet described above.

  In the step of producing a sheet for a fiber-reinforced plastic molded article, a binder component may be added after the papermaking step. For example, a solution containing a binder component or an emulsion containing a binder component may be internally added, applied or impregnated to a paper-made sheet, and then heated and dried. By providing such a process, scattering, fluffing and falling off of surface fibers of the sheet for a fiber-reinforced plastic molded article can be suppressed, and a sheet for a fiber-reinforced plastic molded article having excellent handling properties can be obtained.

  After the solution containing the binder component or the emulsion containing the binder component is internally added, applied or impregnated to the sheet for a fiber-reinforced plastic molded article, it is preferable to rapidly heat the sheet for a fiber-reinforced plastic molded article. By providing such a heating step, the solution containing the binder component or the emulsion containing the binder component can be transferred to the surface layer region of the sheet for a fiber-reinforced plastic molded article. Further, the binder component can be localized in the form of a webbed film.

(Uses of fiber-reinforced plastic moldings)
Examples of applications of the fiber-reinforced plastic molded article include, for example, “OA equipment, mobile phones, smartphones, personal digital assistants, tablet PCs, portable electronic devices such as digital video cameras, air conditioners and other home appliances, and housings. Reinforcing materials such as ribs to be pasted, civil engineering such as "posts, panels, reinforcing materials", parts for construction materials, "various frames, various wheel bearings, various beams, doors, trunk lids, side panels, upper back panels, front bodies , Underbody, various pillars, various frames, various beams, various supports, etc., outer panels or body parts and their reinforcements, "interior parts such as instrument panels and seat frames", or "gasoline tanks, various piping, Fuel, exhaust, or intake system parts such as various valves, Water-repellent joints, thermostat bases for air conditioners, headlamp supports, pedal housings, etc., parts for automobiles, motorcycles, aircraft parts such as "winglets, spoilers", seat members for railcars, skin panels, Parts for railway vehicles such as "reinforcing material to be attached to the outer panel, ceiling panel, air outlet of air conditioner, etc.", "reinforcing material of resin (thermosetting resin, thermoplastic resin), resin and reinforcing fiber Of molded articles made of reinforced plastics, reinforcing materials for plant-derived sheets (kraft paper, corrugated cardboard, oil-resistant paper, insulating paper, conductive paper, release paper, impregnated paper, glassine paper, cellulose nanofiber sheet, etc.) It is preferably used. Furthermore, since the fiber-reinforced plastic molded article of the present invention is excellent in flame retardancy even if it is thin, it can be suitably used as an electric insulating substrate by using glass fiber having high electric insulation as the reinforcing fiber.
As described above, since the fiber-reinforced plastic molded article of the present invention has high strength and excellent flame retardancy and is therefore highly safe, it can be used for electric and electronic equipment housings, structural parts for automobiles, and aircraft. It is preferably used for components, civil engineering, panels for building materials, and various other uses.

  Hereinafter, features of the present invention will be described more specifically with reference to examples and comparative examples. Materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples described below.

<Example 1>
A carbon fiber having a fiber length of 12 mm (T700, manufactured by Toray Industries, Inc.) is charged into water so as to have a slurry concentration of 0.5%, and Emanon (registered trademark) 3199V (manufactured by Kao Corporation) is used as a dispersant, and 100 mass of carbon fiber is used. 1 part by weight per part. Emanone 3199V was dissolved in water and added beforehand so as to be a 0.5% concentration aqueous solution. After that, the mixture was stirred for 30 seconds using a used paper disintegration pulper to perform initial dispersion, and then diluted with water to a slurry concentration of 0.15% (carbon fiber slurry).

  In a separate container, an aqueous solution in which a powdered anionic polymer polyacrylamide-based thickener (manufactured by MT Aqua Polymer Co., Ltd., Sumifloc) was dissolved was prepared. The powdered anionic polymer polyacrylamide thickener was added so as to be 0.1% by mass with respect to the total mass of the aqueous solution. This aqueous solution was added to the above carbon fiber slurry. The addition amount of the aqueous solution was adjusted so that the solid content of the thickener was 60 ppm based on the total mass of the aqueous solution. Thereafter, the mixture was stirred and dispersed until the carbon fibers became monofilament.

  Next, a mass mixing ratio of a nylon 6 fiber having a thickness of 2.2 dtex and a fiber length of 15 mm (manufactured by Toray Industries, Amilan, fiber length of 15 mm) and PVA fiber (VPB-105-2 manufactured by Kuraray Co., Ltd.) used as a binder was used. The weight was measured as shown in Table 1. This was poured into water so that the slurry concentration became 10%, to obtain a thermoplastic resin slurry. Since nylon 6 fiber had good dispersibility, it was sufficiently dispersed without any treatment such as stirring. The obtained thermoplastic resin slurry was mixed with the carbon fiber slurry and stirred so as to be uniformly mixed to obtain a fiber slurry.

The fiber slurry is continuously fed to an inclined paper machine equipped with a Yankee dryer type drying machine, is formed at a speed of 30 m / min, and has a basis weight of 50 g / m ² for a sheet for a fiber-reinforced plastic molded body. I got
At the time of papermaking, the viscosity of the dispersion medium of the slurry (viscosity at a liquid temperature of 25 ° C. measured by a measurement method specified in JIS Z 8803 “Method of measuring viscosity of liquid”) was adjusted as shown in Table 1. The dispersion medium of the slurry is a filtrate obtained by collecting 500 ml of the slurry of the inlet and filtering the fibers through a 150-mesh metal sieve. The viscosity of the dispersion medium of the slurry was adjusted by continuously adding an aqueous solution in which an anionic polymer polyacrylamide thickener (manufactured by MT Aqua Polymer Co., Ltd., Sumifloc) was dissolved in circulating white water.

The inclined paper machine used in Example 1 was equipped with four suction boxes (dewatering boxes) in the inclined wire portion. FIG. 2 is a diagram illustrating the configuration of the inclined paper machine 100 used in the embodiment. As shown in FIG. 2, the inclined paper machine 100 includes a first suction box 101, a second suction box 102, and a third suction box below an inclined wire 120 provided at a bottom of an inlet 110. 103 and a fourth suction box 104.
In Example 1, the wire constituting the inclined wire portion had a permeability of 350 cm ³ / cm ² / sec when a differential pressure of 125 Pa was applied. In the first embodiment, the ratio of the dewatering amount of each suction box when the total amount of the circulating white water dewatered from the four suction boxes is 100 is shown in Table 1 by adjusting the suction force of each suction box. It was as follows.
In addition, the jet wire ratio of the wire of the inclined paper machine was adjusted as shown in Table 1 by controlling the total amount of circulating white water. In this way, a sheet for a fiber-reinforced plastic molded body was produced. Table 1 shows the absolute value of the fp value of the obtained sheet for a fiber-reinforced plastic molded product.

<Preparation of fiber-reinforced plastic molded body for bending strength measurement>
Twenty-eight sheets of the obtained fiber-reinforced plastic molded sheets were laminated, the press speed was increased at 3.5 cm / sec, the press pressure was 10 MPa, the temperature was raised to 260 ° C, and after heating and pressing for 60 seconds, 50 ° C To obtain a fiber-reinforced plastic molded article having a thickness of 1.0 mm.

<Example 2>
Example 2 is a fiber-reinforced plastic molded body in the same manner as in Example 1 except that the suction force of the suction box was adjusted in Example 1 and the amount of dehydration of all suction boxes was changed to be equal. Sheet and a fiber-reinforced plastic molding were produced.

<Example 3>
Except that the viscosity of the inlet dispersion medium was as shown in Table 1 by increasing the continuous addition amount of an aqueous solution in which an anionic polymer polyacrylamide-based thickener (MT Aqua Polymer Co., Ltd., Sumifloc) was dissolved to the inlet. In the same manner as in Example 1, a sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced.

<Example 4>
A sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced in the same manner as in Example 3, except that the ratio of the dehydration amount of each suction box was adjusted as shown in Table 1.

<Example 5>
A sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced in the same manner as in Example 4, except that the wire used for the inclined wire portion was changed to a wire having an air permeability of 275 cm ³ / cm ² / sec.

<Example 6>
A sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced in the same manner as in Example 5, except that the viscosity of the dispersion medium in the inlet was adjusted as shown in Table 1.

<Examples 7 to 9>
A sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced in the same manner as in Example 6, except that the jet wire ratio was adjusted as shown in Table 1.

<Example 10>
A sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced in the same manner as in Example 9 except that the carbon fiber was changed to a fiber having a single fiber strength of 5880 MPa (T800, manufactured by Toray Industries, Inc.).

<Example 11>
A sheet for a fiber-reinforced plastic molding and a fiber-reinforced plastic molding were produced in the same manner as in Example 10, except that the thermoplastic resin fiber was changed to a polycarbonate fiber (manufactured by Daiwabo Co., fiber diameter 30 μm, fiber length 15 mm). .

<Example 12>
A sheet for a fiber-reinforced plastic molding and a fiber-reinforced plastic molding were prepared in the same manner as in Example 10 except that the thermoplastic resin fiber was an acid-modified polypropylene fiber (PZAD, 2.2 dtex × 15 mm, manufactured by Daiwabo Co., Ltd.). Produced.

<Example 13>
A sheet for a fiber-reinforced plastic molding and a fiber-reinforced plastic molding were produced in the same manner as in Example 10 except that the thermoplastic resin fiber was changed to PEI fiber (Kuraray Co., Ltd., 2.2 dtex × 15 mm). Produced.

<Comparative Examples 1 and 2>
A sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article were produced in the same manner as in Example 1 except that the jet wire ratio was adjusted so as to be as shown in Table 1.

(Evaluation)
<Measurement of fiber orientation parameter (fp value) of reinforcing fiber in thickness direction>
The sheet for fiber-reinforced plastic moldings obtained in Examples and Comparative Examples was cut into a width of 5 mm and a length of 10 mm, and an ultraviolet-curable epoxy resin for embedding (Aronix LCA D-800, manufactured by JEOL Ltd.) was used. The test piece was impregnated with a dropper so as to cover the entire surface of the test piece, and was cured by irradiating ultraviolet rays. Then, using a slice master HS-1 manufactured by JASCO Corporation, a test piece having a width of 0.4 mm and a length of 10 mm was cut out from the test piece for cross-sectional observation. The cutting direction was the BB 'direction in FIG. The BB ′ direction is a direction parallel to a reference line in a plane direction obtained by a method described later.
The cross section in the thickness direction of the obtained test piece was magnified 300 times with a microscope manufactured by Ens Co., Ltd., and the reinforcing fiber was observed with transmitted light. Here, a continuous measurement area of 1.5 mm ^{2 in} the cross section was observed. Further, observation was performed by focusing on a portion having a depth of 10 μm or more from each of the observation surface and the opposite surface of the test piece. Then, for all the reinforcing fibers (the number of fibers is assumed to be n) present in the measurement area and which can be visually recognized in the observation image, the angle θi (i = 1 to n) with respect to a reference line set by a method described later is calculated. It was measured. The orientation angle θi was measured in a clockwise direction with respect to a reference line, and was set to an angle of 0 ° or more and less than 180 °. Then, the fiber orientation parameter in the thickness direction was calculated from the angle θi of the fiber with respect to the set reference line using the following equation (1).
fp = 2 × Σ (cos ² θ _i / n) −1 Equation (1)

The reference line was determined by the following method. When determining the reference line, first, the provisional reference line p was selected, and the angles of all the visible reinforcing fibers n present in the measurement area were measured. In this case, the angle between the temporary reference line p and each fiber was represented by α (p) _i (i = 1 to n).
The fiber orientation parameter (fp (p)) of the reinforcing fibers when the temporary reference line p was calculated using the following equation.
fp (p) = 2 × Σ (cos ² α (p) _i / n) −1
(I = 1, 2, 3,..., N)
Next, a temporary reference line (p _{+ z} , p- _z (z = 1 to 90)) obtained by rotating the temporary reference line p by ± 1 ° until it becomes ± 90 ° is taken, and a temporary reference line p _{+ z} The angle between the tentative reference line p- _z and the n fibers was calculated. The angle in this case was represented by α (p _{+ z} ) _i and α (p− _z ) _i (i = 1 to n).
The rotated provisional reference lines (p _{+ z} , p- _z (z = 1 to 90)) and the fiber orientation parameters (fp (p ± _z )) of the reinforcing fibers were calculated using the following formula.
fp (p ± _z ) = 2 × Σ (cos ² α (p ± _z ) _i / n) −1
(I = 1, 2, 3,..., N)
The provisional reference line set when the maximum value among the absolute values of the fp (p) value and the fp (p ± _z ) value obtained in this manner was used as the reference line.

<Measurement of fiber orientation parameter (fp value) of reinforcing fiber in plane direction>
The sheet for a fiber-reinforced plastic molded body obtained in each of Examples and Comparative Examples was cut out so as to have a width of 3 cm and a length of 3 cm, the test piece was sandwiched between slide glasses, and one surface of the test piece was observed with an optical microscope. Observed. A microscope manufactured by KEYENCE CORPORATION was used as an optical microscope, and the reinforcing fibers were observed at a magnification of 300 times with reflected light. Here, a continuous measurement area of 2.0 mm ^{2 on} the one surface was observed. Then, for all the reinforcing fibers (the number of fibers is assumed to be m) present in the observation area, which are present in the measurement area, the angle θi (i = 1 to m) with respect to a reference line set by a method described later is determined. It was measured. The orientation angle θi was measured in a clockwise direction with respect to a reference line, and was set to an angle of 0 ° or more and less than 180 °. Then, the fiber orientation parameter in the thickness direction was calculated from the angle θi of the fiber with respect to the set reference line using the following equation (2).
fp = 2 × Σ (cos ² θ _i / m) −1 Equation (2)
Then, the same measurement was performed on the opposite surface, and the average value of the one surface and the opposite surface was obtained, and this was defined as the fiber orientation parameter (fp) in the planar direction. The measurement region on one surface and the measurement region on the opposite surface were defined as regions that overlap in plan view. In both observations on one surface and the opposite surface, observation was performed by focusing on a portion having a depth of 10 μm or more from each of the one surface and the opposite surface.

The reference line was determined by the following method. When determining the reference line, first, the provisional reference line p was selected, and the angles of all the visible reinforcing fibers m present in the measurement area were measured. In this case, the angle between the temporary reference line p and each fiber was represented by α (p) _i (i = 1 to m).
The fiber orientation parameter (fp (p)) with the provisional reference line p was calculated using the following equation.
fp (p) = 2 × Σ (cos ² α (p) _i / m) −1
(I = 1, 2, 3,..., M)
Next, a temporary reference line (p _{+ z} , p- _z (z = 1 to 90)) obtained by rotating the temporary reference line p by ± 1 ° until it becomes ± 90 ° is taken, and a temporary reference line p _{+ z} The angle between the tentative reference line p- _z and the m fibers was calculated. The angle in this case is represented by α (p _{+ z} ) _i and α (p− _z ) _i (i = 1 to m).
The rotated provisional reference lines (p _{+ z} , p- _z (z = 1 to 90)) and the fiber orientation parameters (fp (p ± _z )) of the reinforcing fibers were calculated using the following formula.
fp (p ± _z ) = 2 × Σ (cos ² α (p ± _z ) _i / m) −1
(I = 1, 2, 3,..., M)
The provisional reference line set when the maximum value among the absolute values of the fp (p) value and the fp (p ± _z ) value obtained in this manner was used as the reference line.

<Measurement of bending strength>
According to the bending test method of JIS K7074 carbon fiber reinforced plastic, the fiber orientation direction (machine direction, hereinafter referred to as MD) and fiber orientation of the fiber-reinforced plastic molded body for bending strength measurement obtained in Examples and Comparative Examples were used. The intensity and the intensity ratio between the MD direction and the CD direction are shown in Table 1.
Geometric mean value of bending strength = √ (FMD × FCD)
Here, FMD represents bending strength in the MD direction, and FCD represents bending strength in the CD direction.

  As shown in Table 1, the absolute value of the fp value in the thickness direction is 0.5 or more, and the absolute value of the fp value in the planar direction is 0.25 or more. It can be seen that the fiber reinforced plastic molded article has a high bending strength geometric mean value. Further, in such a fiber-reinforced plastic molded body, the bending strength in one of the plane directions is enhanced.

In addition, comparing Examples 1 to 4, it can be seen that the dehydration in the inclined wire portion can be adjusted to a more preferable range in the thickness direction by increasing the dehydration amount in the first half of the wire. This is because the flow rate of the slurry is low and the turbulent flow is unlikely to occur in the portion of the inlet where the distance from the liquid surface to the wire is long, so by forming a wet web in this area, the fibers can be controlled in the thickness direction of the sheet. It is thought that it becomes easy to do. In FIG. 2, the distance from the liquid surface of the suction box 101 to the wire is the longest.
Further, in Examples 1 to 6, the fp value can be set in a more preferable range by increasing the viscosity of the dispersion medium in the inlet. However, by decreasing the air permeability of the wire, the dispersion medium in the inlet can be reduced. It can be seen that the fp value can be set in a more preferable range even if the viscosity of is low. This means that the use of a wire having low air permeability can reduce the amount of the adhesive added during papermaking. As a result, it is possible to reduce the manufacturing cost and to reduce the contamination of the papermaking tool due to the adhesive.

Reference Signs List 5 Sheet for fiber-reinforced plastic molded article 20 Reinforced fiber 25 Thermoplastic resin 40 Epoxy resin for embedding 45 Test specimen for cross-section observation 100 Inclined paper machine 101 First suction box 102 Second suction box 103 Third suction box 104 Fourth suction box 110 Inlet 120 Inclined wire P Reference line P 'Line parallel to reference line (auxiliary line)
Q Line representing the angle of the reinforcing fiber with respect to the reference line R Line representing the angle of the reinforcing fiber with respect to the reference line

Claims (13)

A sheet for fiber-reinforced plastic moldings containing reinforcing fibers and thermoplastic resin fibers,
The fiber-reinforced plastic molded sheet is a wet papermaking sheet,
The fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction in the sheet for a fiber-reinforced plastic molded product is 0.5 to 1.0, and the fiber orientation parameter (fp) in the plane direction is 0.25 to 1.0. A sheet for a fiber-reinforced plastic molding.   The sheet for a fiber-reinforced plastic molded article according to claim 1, further comprising a binder component, wherein the binder component is contained in an amount of 0.1 to 10% by mass based on the total mass of the sheet for a fiber-reinforced plastic molded article.   The sheet for a fiber-reinforced plastic molded product according to claim 2, wherein the binder component contains polyethylene terephthalate or modified polyethylene terephthalate fibers.   The sheet for a fiber-reinforced plastic molded product according to any one of claims 1 to 3, wherein a mass average fiber length of the reinforcing fiber is 3 to 100 mm.   The sheet for a fiber-reinforced plastic molded product according to any one of claims 1 to 4, wherein the reinforcing fiber is at least one selected from glass fiber, carbon fiber, and aramid fiber.   The sheet for a fiber-reinforced plastic molded product according to any one of claims 1 to 5, wherein the reinforcing fiber is a carbon fiber having a single fiber strength of 4600 MPa or more.   The sheet for a fiber-reinforced plastic molded product according to any one of claims 1 to 6, wherein the thermoplastic resin fiber is at least one selected from a polyetherimide fiber, a polycarbonate fiber, a polyamide fiber, and a polypropylene fiber.   The sheet for a fiber-reinforced plastic molding according to any one of claims 1 to 7, wherein the thermoplastic resin fiber is a polypropylene fiber.   The sheet for a fiber-reinforced plastic molded article according to claim 8, wherein the polypropylene fiber is an acid-modified polypropylene fiber.   The sheet for a fiber-reinforced plastic molding according to any one of claims 1 to 7, wherein the thermoplastic resin fiber is a nylon fiber.   The sheet for a fiber-reinforced plastic molded product according to claim 10, wherein the nylon fiber is a nylon 6 fiber.   The sheet for a fiber-reinforced plastic molded product according to any one of claims 1 to 11, wherein the reinforcing fiber and the thermoplastic resin fiber are chopped strands. A method for producing a fiber-reinforced plastic molded article, comprising a step of pressure-heating and molding the sheet for a fiber-reinforced plastic molded article according to any one of claims 1 to 12 at a temperature of 150 to 600 ° C. ,
A fiber in which the fiber orientation parameter (fp) of the reinforcing fiber in the thickness direction in the fiber-reinforced plastic molded product is 0.5 to 1.0, and the fiber orientation parameter (fp) in the planar direction is 0.25 to 1.0. A method for producing a reinforced plastic molding.

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