JP6747543B2 - Sheet for fiber-reinforced plastic molding - Google Patents

Description

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

Fiber reinforced plastic moldings made by heating and pressing a non-woven fabric (also called a sheet for fiber reinforced plastic moldings) containing reinforced fibers such as carbon fibers and glass fibers have already been used for sports, leisure goods, aircraft materials, etc. It is 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 products. However, when the thermosetting resin is used, the nonwoven fabric in which the thermosetting resin and the reinforcing fibers are mixed must be stored in a refrigerating state, and it is difficult to store for a long period of time.

Therefore, in recent years, development of a fiber-reinforced non-woven fabric containing a reinforcing fiber using a thermoplastic resin as a matrix resin has been promoted. The fiber-reinforced non-woven fabric using such a thermoplastic resin as a matrix resin has advantages that storage management is easy and long-term storage is possible. Further, a nonwoven fabric containing a thermoplastic resin has an advantage that it can be molded more easily than a nonwoven fabric containing a thermosetting resin, and a molded product can be molded by performing heat and pressure treatment. ing.

Conventionally, thermoplastic resins have generally been inferior in chemical resistance and strength to thermosetting resins. 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. There is. Such a thermoplastic resin is a so-called "engineering plastic (engineering plastic)", and includes polycarbonate (PC), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamide imide (PAI), and polyether imide. (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. Further, it is known that the reinforcing fiber has a directionality in the strength of the fiber-reinforced plastic molded product by adjusting the orientation direction thereof to a specific direction (for example, Patent Documents 1 to 6). Such a fiber-reinforced plastic molded product is used for a reinforcing core material such as a bumper beam of an automobile or a structural component that requires mechanical strength in one direction.

JP-A-5-44188 Japanese Unexamined Patent Publication No. 9-41280 JP-A-6-155495 JP-A-4-208405 JP-A-4-208406 JP-A-4-208407

"FY2007 Survey Report on Application of Thermoplastic Resin Composite Materials to the Machine Industry Field", Japan Next Generation Metals and Composite Materials Research and Development Association, Japan Machinery Federation, March 2008

As described above, in the fiber-reinforced plastic molded body sheet obtained by the conventional technique, the strength of the fiber-reinforced plastic molded body can be made to have 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 body having an increased strength in one direction, and in such a fiber-reinforced plastic molded body, the bending strength of the entire fiber-reinforced plastic molded body tends to be insufficient. It was a problem because it was seen. Therefore, there has been a demand for the development of a fiber-reinforced plastic molded body having a mechanical strength increased in a specific direction, and a fiber-reinforced plastic molded body having an increased bending strength of the entire fiber-reinforced plastic molded body.

Therefore, in order to solve the problems of the prior art, the inventors of the present invention have a fiber-reinforced plastic molded body having a sufficiently high strength in a specific direction, and the bending strength of the entire fiber-reinforced plastic molded body is high. The study was advanced for the purpose of providing a sheet for a fiber-reinforced plastic molded body capable of molding a fiber-reinforced plastic molded body.

As a result of intensive studies to solve the above problems, the present inventors have found that reinforcing fibers and fibers of the reinforcing fiber in the thickness direction and the plane direction in the sheet for fiber-reinforced plastic molded articles containing a thermoplastic resin. It has been found that by setting the orientation parameter (fp) within a specific range, the strength in a specific direction can be sufficiently increased and a fiber-reinforced plastic molded product having excellent bending strength can be molded.
Specifically, the present invention has the following configurations.

[1] A sheet for a fiber-reinforced plastic molded body 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 molded body is 0. A sheet for a fiber-reinforced plastic molded product having a fiber orientation parameter (fp) of 5 to 1.0 and an absolute value of a fiber orientation parameter (fp) in a plane direction of 0.25 to 1.0.
[2] The sheet for fiber-reinforced plastic molding 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, and the binder component being contained in an amount of 0.1 to 10 mass% with respect to the total mass of the sheet for a fiber-reinforced plastic molded body. Sheet for molded products.
[4] The sheet for a fiber-reinforced plastic molded product according to [3], which contains polyethylene terephthalate or modified polyethylene terephthalate fiber as a binder component.
[5] The sheet for a fiber-reinforced plastic molded product according to any one of [1] to [4], wherein the reinforcing fibers have a mass average fiber length of 3 to 100 mm.
[6] The sheet for fiber-reinforced plastic molding according to any one of [1] to [5], wherein the reinforcing fiber is at least one selected from glass fiber, carbon fiber and aramid fiber.
[7] The sheet for fiber-reinforced plastic molding 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 fiber-reinforced plastic molding 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 fiber-reinforced plastic molding according to any one of [1] to [8], wherein the thermoplastic resin is polypropylene fiber.
[10] The polypropylene fiber is a sheet for a fiber-reinforced plastic molding according to [9], which is an acid-modified polypropylene fiber.
[11] The sheet for fiber-reinforced plastic molding according to any one of [1] to [8], wherein the thermoplastic resin is nylon fiber.
[12] The sheet for fiber-reinforced plastic molding according to [11], wherein the nylon fiber is nylon 6 fiber.
[13] The fiber-reinforced plastic molded sheet according to any one of [1] to [12], in which the reinforcing fiber and the thermoplastic resin are chopped strands.
[14] The sheet for fiber-reinforced plastic molding described in any one of [1] to [13] is formed by press-heating at a temperature not lower than the melting point or glass transition temperature of the thermoplastic resin. A fiber-reinforced plastic molded product, wherein the absolute value of the fiber orientation parameter (fp) of the reinforcing fibers in the thickness direction of the fiber-reinforced plastic molded product is 0.5 to 1.0, and the fiber orientation parameter (fp) in the plane direction. A fiber-reinforced plastic molded product having an absolute value of 0.25 to 1.0.
[15] The fiber-reinforced plastic molded product according to [14], in which the strength ratio of the bending strength of the fiber-reinforced plastic molded product in the first direction and the bending strength in the second direction orthogonal to the first direction is 2.5 or more. ..
[16] The fiber-reinforced plastic molded product according to [14] or [15], which is formed by heat-press molding at a temperature of 150 to 600°C.
[17] The fiber-reinforced plastic molded product according to any one of [14] to [16], which has a thickness of more than 40 μm and 100 μm or less.
[18] The fiber-reinforced plastic molded product according to any one of [14] to [16], which has a thickness of 20 μm or more and 40 μm or less.
[19] The fiber-reinforced plastic molded product 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 molding is adhered to both surfaces of the core material.
[20] A wet papermaking process includes a wet papermaking process of a slurry in which reinforcing fibers and thermoplastic resin fibers are mixed, and the wet papermaking process is a process of making paper using an inclined paper machine, and the wire of the inclined paper machine is A method for producing a sheet for a fiber-reinforced plastic molded article, which travels so that the jet wire ratio becomes 0.98 or less.
[21] The method for producing a sheet for a fiber-reinforced plastic molded product according to [20], wherein the wire of the inclined type paper machine runs so that the jet wire ratio becomes 0.90 or less.
[22] The method for producing a sheet for a fiber-reinforced plastic molded product according to [20] or [21], wherein the dispersion medium of the slurry has a viscosity at 25°C of more than 1.00 mPas and 4.00 mPas or less.

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

FIG. 1 is an image view of a cross-section observing 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 illustrating the configuration of the inclined paper machine used in the examples.

Hereinafter, the present invention will be described in detail. The description of the constituents described below may be made based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

(Sheet for fiber reinforced plastic molding)
TECHNICAL FIELD The present invention relates to a sheet for a fiber-reinforced plastic molded body 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 of 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) of the plane direction. Is 0.25 to 1.0.

In the present specification, the fiber orientation parameter (fp) of the reinforcing fiber is a parameter indicating the orientation state of the reinforcing fiber in the sheet for fiber-reinforced plastic molding. The fiber orientation parameter (fp) is a parameter representing the fiber orientation distribution with 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 arranged completely randomly.

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 product 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. It is more preferably 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. It is more preferably from 4 to 1.0, further preferably from 0.60 to 1.0. As described above, in the sheet for a fiber-reinforced plastic molded product of the present invention, the orientation of the reinforcing fibers in the thickness direction and the orientation in the plane direction are preferably constant.
The fiber orientation parameter (fp) of the reinforcing fibers in the thickness direction and the plane direction in the fiber-reinforced plastic molded sheet can be controlled by appropriately selecting, for example, the method for manufacturing the fiber-reinforced plastic molded sheet. It is possible.

(Calculation of fiber orientation parameter in the thickness direction)
When measuring the fiber orientation parameter (fp) of reinforcing fibers in the thickness direction in a sheet for a fiber-reinforced plastic molded body, an epoxy resin for embedding which is generally used for electron microscope observation in a sheet for a fiber-reinforced plastic molded body. And the like are impregnated with each other to prepare a cross-section observation test piece. The reason for impregnating the epoxy resin for embedding here is to prevent the orientation direction of the fibers from being changed by the shearing force at the time of cutting the cross-section to be described later. As the embedding resin, a resin having sufficient strength/hardness capable of withstanding shearing force such as epoxy resin or styrene resin is preferable, but in the present invention, by using the epoxy resin, the fiber orientation of the reinforcing fiber in the thickness direction The parameter (fp) is measured. Examples of the embedding resin include Aronix LCA D-800 manufactured by JEOL Ltd. For thermosetting resins and resins that generate heat during curing, the adhesive strength between the reinforcing fibers of the binder in the sheet for fiber-reinforced plastic molding is reduced by the heat during 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 serve as a heat source during curing, such as a photo-curing type epoxy resin such as ultraviolet rays.
As the resin embedding method, a method generally used in electron microscope observation or optical microscope observation can be adopted. Specifically, the sheet for fiber-reinforced plastic molding is cut into a width of 5 mm and a length of 10 mm, and the above-mentioned embedding epoxy resin is dropped and impregnated until at least the entire surface of the test piece is covered, and then cured. Moreover, the dropping of the embedding epoxy resin can be performed using, for example, a dropper.

FIG. 1 is a conceptual diagram of a cross-section observing test piece obtained by impregnating a sheet for a fiber-reinforced plastic molded product with an ultraviolet curing type embedding epoxy resin. As shown in FIG. 1A, the cross-section observation test piece 45 includes the reinforcing fiber 20 and the thermoplastic resin 25 that form the sheet 5 for the fiber-reinforced plastic molded body, and the embedding epoxy resin 40. To do. In the cross-section observation test piece 45, the positional relationship and shape of the reinforcing fiber 20 and the thermoplastic resin 25 are the same as those in the sheet 5 for the 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 shape of the reinforcing fiber 20 and the thermoplastic resin 25.

In addition, in FIG. 1A, the thermoplastic resin 25 is shown in a fiber shape, but in reality, it may not be a fiber shape, and may be a particle shape or the like. When the thermoplastic resin 25 has a fibrous shape as shown in FIG. 1A, it has a shape similar to that of the reinforcing fiber 20, and it seems that they cannot be distinguished. However, when observing the orientation state of the reinforcing fibers, it is possible to observe the orientation of only the reinforcing fibers by utilizing the difference in fiber diameter, the 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 cross-section observation test piece, and the cross section in the thickness direction of the obtained test piece is observed with an optical microscope. As a cutting method, a method of cutting vertically with a thin sharp blade such as a safety razor or a surgical knife can be adopted. However, since it is difficult to obtain a vertical cross section manually, a film slicer for cutting out a FT-IR measurement section or an ion slicer for cutting out a section for electron microscope observation can be used. Examples of the film slicer include Slice Master HS-1 manufactured by JASCO Corporation, and examples of the ion slicer include EM-09100IS manufactured by JEOL Ltd. Here, the cutting-out direction of the test piece is a direction parallel to the reference line in the plane direction obtained by the method described later. As the optical microscope, a microscope manufactured by Keyence Corporation is used, and the fiber is observed by enlarging it to a magnification at which the monofilament can be visually recognized. When the reinforcing fiber is not a transparent fiber (for example, carbon fiber), the reinforcing fiber can be observed by transmitted light. In the present embodiment, for example, the magnification can be selected from 300 times, 600 times, and 800 times. Further, the observation of the reinforcing fibers is performed by focusing on the observation surface of the test piece and the opposite surface thereof to a portion having a depth of 10 μm or more. The test piece may be cut out using a microtome.
In the present invention, by embedding in an epoxy resin and cutting out a cross section in the thickness direction, it is possible to prevent the fiber angle 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 due to the difference in the chromaticity of the fibers when observed with an optical microscope. For example, when observing carbon fibers, black fibers can be observed as reinforcing fibers.

When a transparent reinforcing fiber such as 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, in the same manner as above, the fiber-reinforced plastic molded article sheet was embedded with an epoxy resin, cut out so that the cross-section of the cross-section observation test piece was exposed, and then the element mapping was performed to align the reinforced fibers. 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 glass fibers, the Si or Ca element can be measured for the fiber orientation by mapping with an electron microscope equipped with an energy dispersive X analysis (EDS/EDX: Energy Dispersive X-Ray Spectroscopy) device. .. An example of such an apparatus is a tabletop scanning electron microscope "PRO X" manufactured by Phenomworld, Netherlands.

The orientation direction of the reinforcing fibers is the major axis direction of the reinforcing fibers. In addition, the reinforcing fibers may be confirmed to have an elliptical shape in the cross section in the thickness direction. When the reinforcing fiber is confirmed to have an elliptical shape, the major axis direction of this ellipse is 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, the cross section in the thickness direction of the test piece is observed under the above conditions with an optical microscope or the like, and a continuously selected 1.5 mm ² measurement region of the cross section is observed. The orientation angles θi of all the visible reinforcing fibers (the number of fibers is n) existing in the are measured. The orientation angle θi is an angle of 0° or more and less than 180°, which is obtained by measuring the angle in the clockwise direction with respect to the reference line.

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 formula (1).
fp=2×Σ(cos ² θ _i /n)-1 Expression (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 visible n reinforcing fibers existing in the measurement region 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 formula.
fp(p)=2×Σ(cos ² α(p) _i /n)−1
(I=1, 2, 3,..., N)
Next, the provisional reference line p (p _+z , p _-z (z = 1 to 90)) obtained by rotating the provisional reference line p by ±1° until it becomes ±90° is taken, and the provisional reference line p _{+z is obtained.} Then, the angle between the provisional reference line p _−z and n fibers is calculated. The angle in this case is represented by α(p _+z ) _i and α(p _−z ) _i (i=1 to n).
The rotated tentative reference line (p _+z , p- _z (z=1 to 90)) and the fiber orientation parameter (fp(p± _z )) of the reinforcing fiber 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 way, the provisional reference line set when the maximum value of the absolute values of the obtained fp(p) value and fp(p± _z ) value is obtained can be set as the reference line P. The fiber orientation parameter calculated from the thus determined reference line P 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 parallel to the direction in which most of the fibers are oriented. That is, the BB' direction is a direction parallel to the reference line in the plane direction obtained by the 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, respectively. In addition, in FIG. 1B, the dotted line P′ is a line parallel to the reference line, and is for explaining the angle formed by the reference line P and the orientation lines (Q and R) of each reinforcing fiber in an easy-to-understand manner. It is an auxiliary line. In FIG. 1B, since the angle formed by P′ and Q (orientation angle θ ₁ ) is 0°, P′ and Q overlap. The angle formed by P′ and R (orientation angle θ ₂ ) is represented as θ ₂ . In this way, θ ₁ to θ _n are measured. In FIG. 1B, only the reinforcing fibers are shown in order to make it easier to confirm the orientation of the reinforcing fibers.

As the portion for measuring the fiber orientation parameter (fp) and the fiber orientation parameter (fp(p± _z )) of the tentative reference line and the reinforcing fiber, avoid the end of the cross section in the thickness direction of the test piece for cross section observation. It is preferably near the center. Specifically, it is preferable to avoid a region up to 5% (5% with respect to the thickness of the cross-section observation test piece) in the thickness direction from both end sides of the cross-section observation test piece as the measurement region.

(Calculation of fiber orientation parameter in plane direction)
On the other hand, the measurement of the fiber orientation parameter in the plane direction of the sheet for a fiber-reinforced plastic molded product can be performed without any processing such as resin embedding. Specifically, place a sheet for fiber-reinforced plastic molding that is cut into a length of 3 cm and a width of 3 cm on a slide glass, then further mount the slide glass from above, and observe by ordinary measurement of reflected light using a microscope. can do.
In the present invention, one surface of a test piece sandwiched between slide glasses is observed with an optical microscope. As the optical microscope, a microscope manufactured by Keyence Corporation is used, and the fiber is observed by magnifying the monofilament to a magnification at which the monofilament can be visually recognized and by reflected light or by using reflected light and transmitted light in combination. In the present embodiment, for example, the magnification can be selected from 300 times, 600 times, and 800 times. Thereby, an arbitrarily selected continuous 2.0 mm ² measurement area on one surface is observed, and all visible reinforcing fibers (the number of fibers is m) existing in this measurement area. The orientation angle θi of is measured. The orientation angle θi is an angle of 0° or more and less than 180°, which is obtained by measuring the angle in the clockwise direction with respect to the reference line. 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)
However, i=1 to m.
Then, the other surface is also measured in the same manner, the average value of the one surface and the opposite surface is obtained, and this is set as the fiber orientation parameter (fp) in the plane direction. The measurement area on one surface and the measurement area on the opposite surface are, for example, areas that overlap in a plan view. In addition, in either observation of the one surface and the opposite surface, for example, the observation can be 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 for measuring the fiber orientation parameter in the plane direction can be determined by the following method.
When setting the reference line, first, the temporary reference line p is selected, and the angles of all visible m fibers existing in the measurement region 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 formula.
fp(p)=2×Σ(cos ² α(p) _i /m)−1
(I=1, 2, 3,..., m)
Next, the provisional reference line p (p _+z , p _-z (z = 1 to 90)) obtained by rotating the provisional reference line p by ±1° until it becomes ±90° is taken, and the provisional reference line p _+z Then, the angle between the provisional reference line p _−z and the m fibers is calculated. The angle in this case is represented by α(p _+z ) _i and α(p _−z ) _i (i=1 to m).
The rotated tentative reference line (p _+z , p- _z (z=1 to 90)) and the fiber orientation parameter (fp(p± _z )) of the reinforcing fiber 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 provisional reference line set when the maximum value of the obtained fp(p) value and fp(p± _z ) value is obtained can be set as the reference line P. The fiber orientation parameter calculated from the thus determined reference line P can be used as the fiber orientation parameter (fp) in the plane direction.

The reinforcing fibers may be oriented in any of the plane directions of the sheet for a fiber-reinforced plastic molded body, but should be oriented in the MD direction of the sheet for a fiber-reinforced plastic molded body (the flow direction of the papermaking line). 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 body. Further, in the fiber-reinforced plastic molded body obtained by molding the sheet for fiber-reinforced plastic molded body as described above, the bending strength of the entire fiber-reinforced plastic molded body is also increased.

In the present invention, when the absolute value of the fiber orientation parameter (fp) of the reinforcing fibers in the thickness direction and the plane direction is within the above range, the orientation of the reinforcing fibers in the thickness direction and the plane direction in the sheet for fiber-reinforced plastic molding is It means a fixed direction. That is, it means that the reinforcing fibers are oriented in one direction in the sheet for a fiber-reinforced plastic molded body. Further, also in the fiber-reinforced plastic molded product molded from such a fiber-reinforced plastic molded product sheet, the reinforcing fibers are oriented in one direction.
In the sheet for fiber-reinforced plastic molded products and the fiber-reinforced plastic molded products, the fact that the orientation of the reinforcing fibers in the thickness direction is constant means that the reinforced fibers are the same as those for the sheet for fiber-reinforced plastic molded products and the fiber-reinforced plastic molded products. It means that it is oriented parallel to the surface (paper making surface).

In the sheet for a fiber-reinforced plastic molded product of the present invention, the mixing ratio of the reinforcing fibers is preferably 20 to 83% by mass. By setting the mixing 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 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 and the thermoplastic resin in the sheet for a fiber-reinforced plastic molded body is preferably 1:0.2 to 1:10, and more preferably 1:0.5 to 1:5. It is more preferably 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 product can be molded.

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

(Reinforcing fiber)
The reinforcing fiber is preferably at least one selected from glass fiber, carbon fiber and aramid fiber. These reinforcing fibers may use only 1 type and may use 2 or more types. Further, it may contain an organic fiber having excellent heat resistance such as PBO (polyparaphenylenebenzoxazole) fiber.

As the reinforcing fiber, for example, when an inorganic fiber such as carbon fiber or glass fiber is used, a fiber-reinforced plastic molded body is obtained by heating and pressing at the melting temperature of the thermoplastic resin contained in the sheet for the fiber-reinforced plastic molded body. Can be formed.
Further, when the organic fiber such as aramid is used as the reinforcing fiber, it is possible to improve the wear resistance as compared with the molded body generally formed from the sheet for the fiber-reinforced plastic molded body using the inorganic fiber as the reinforcing fiber. ..

The mass average fiber length of the reinforcing fibers is preferably 3 to 100 mm, more preferably 3 to 75 mm, further preferably 3 to 50 mm, and particularly preferably 6 to 50 mm. By setting the fiber length of the reinforcing fiber within the above range, it is possible to prevent the reinforcing fiber from falling out of the sheet for a fiber-reinforced plastic molded body, and to form a fiber-reinforced plastic molded body having excellent strength. Is possible. Further, by setting the fiber length of the reinforcing fibers within the above range, the dispersibility of the reinforcing fibers can be improved. As a result, the fiber-reinforced plastic molded product after 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, both carbon fibers and glass fibers having a fiber diameter of about 5 to 25 μm are preferably used. Further, a plurality of materials and shapes may be used together for the reinforcing fiber.
In addition, in this specification, an average fiber diameter is an average value when measuring the fiber diameter of 100 fibers.

(Carbon fiber)
Carbon fibers are preferably used as the reinforcing fibers. As the carbon fiber contained in the reinforcing fiber, carbon fiber of polyacrylonitrile (PAN) type, petroleum/coal pitch type, rayon type, lignin type or the like can be used. These carbon fibers may be used alone or in combination of two or more. 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 3 to 100 mm, more preferably 3 to 75 mm, further preferably 3 to 50 mm, and particularly preferably 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 body, and to mold a fiber-reinforced plastic molded body having excellent strength. Is possible. Further, by setting the fiber length of the carbon fibers within the above range, the dispersibility of the reinforcing fibers can be improved. As a result, the fiber-reinforced plastic molded product after 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. Single fiber strength refers to the tensile strength of a monofilament. When such a carbon fiber is used, the bending strength is significantly improved by the 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 a generally preferable range is 5 to 20 μm. By setting the fiber diameter of the carbon fibers within the above range, the strength of the fiber-reinforced plastic molded product can be increased.

(Thermoplastic resin)
The thermoplastic resin forms a binding point at the intersection of the matrix or the fiber component during the heat and pressure treatment. Nonwoven fabric-like sheets for fiber-reinforced plastic moldings using such thermoplastic resins do not require autoclave treatment compared to sheets using thermosetting resins, and heat and pressure molding time during processing is shorter. It only takes time, and productivity can be increased.

The thermoplastic resin is preferably a thermoplastic resin fiber. As the thermoplastic resin fiber, polycarbonate (PC), polyether ether ketone (PEEK), polyamide imide (PAI), polyphenylene sulfide (PPS), polyether imide (PEI), polyether ketone ketone (PEKK), polyamide, polypropylene Etc. can be illustrated. Above all, it is preferable to use polycarbonate, polyetherimide, or polyamide in order to obtain a fiber-reinforced plastic molded product having good fiber dispersibility and high strength. The polyamide is preferably nylon, more preferably nylon 6.

In the present invention, it is also preferable to use polypropylene fiber as the thermoplastic resin because it is inexpensive and has a low melting point, which facilitates the molding process. Furthermore, when polypropylene is used as the matrix resin, the polypropylene is preferably acid-modified polypropylene. When the modified polypropylene is used, the adhesiveness between the modified polypropylene and the reinforcing fiber is improved, so that the bending strength and elastic modulus of the fiber-reinforced plastic molded product 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 acid such as acrylic acid, methacrylic acid, crotonic acid, sorbic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid. Dicarboxylic acids such as itaconic anhydride and citraconic anhydride can be used. 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 α-olefin, a block copolymer of propylene and another olefin, and the like. 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 inexpensively available, 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. Graft copolymerization is preferred from the viewpoint that carboxyl groups are easily exposed on the surface when formed into fibers. From the viewpoint of having a large amount of carboxyl groups, the acid-modified polypropylene is preferably one or more selected from the group consisting of maleic acid-modified polypropylene and maleic anhydride-modified polypropylene. The above acid-modified polypropylene may be used alone or in combination of two or more kinds.

In the fibrous state, the thermoplastic resin preferably has a limiting oxygen index of 24 or more, more preferably 27 or more. By setting the limiting oxygen index of the thermoplastic resin within the above range, it is possible to obtain a sheet for a fiber-reinforced plastic molded article and a fiber-reinforced plastic molded article having excellent flame retardancy. In the present invention, the “limit oxygen index” represents the oxygen concentration necessary for continuing combustion, and is a numerical value measured by the method described in JIS K7201. That is, the limiting oxygen index of 20 or less is a numerical value indicating that combustion occurs in normal air.
Further, it is preferable that the amount of smoke at 20 minutes of combustion of the thermoplastic resin measured by the method described in ASTM E-662 is around 30 ds, and a sheet for fiber-reinforced plastic moldings 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 such as 300° C. to 400° C. when forming the fiber-reinforced plastic molded body. It should be noted that even super engineering plastic fibers having a glass transition temperature of less than 140° C. such as PPS resin fibers can be used as long as they are fiberized from super engineering plastics whose resin deflection temperature under load is 190° C. or higher. Such a thermoplastic resin is melted by heating and pressurization to form a resin block having a very high flame retardancy with a limiting oxygen index of 30 or more.

The mass average fiber length of the thermoplastic resin fibers is preferably 2 to 100 mm, more preferably 2 to 50 mm, further preferably 3 to 50 mm, particularly preferably 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 prevent the thermoplastic resin fiber from falling out of the sheet for a fiber-reinforced plastic molded product, and for a fiber-reinforced plastic molded product excellent in handling property. You can get a sheet. Further, by setting the fiber length of the thermoplastic resin within the above range, it is possible to improve the dispersibility of the thermoplastic resin fiber, and thus it becomes possible to form a fiber-reinforced plastic molded product having excellent strength. .. As a result, the fiber-reinforced plastic molded product after heat and pressure molding has good strength and appearance.

In the sheet for a fiber-reinforced plastic molded product used in the present invention, the thermoplastic resin has a fiber form, so that voids are present in the sheet.
In the present invention, since the thermoplastic resin maintains the fiber form before the heat and pressure molding, the sheet itself is flexible and has the drape property before forming the fiber reinforced plastic molded body. Therefore, it is possible to store and transport the sheet for a fiber-reinforced plastic molded product in a rolled-up form, and it has a feature that it is excellent in handleability.

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

(Binder component)
The fiber-reinforced plastic molded sheet of the present invention preferably further contains a binder component. The binder component is preferably contained so as to be 0.1 to 10 mass% with respect to the total mass of the fiber-reinforced plastic layer, more preferably 0.3 to 10 mass%, and 0.4 to It 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. When the amount of the binder component increases, both the surface strength and the interlaminar strength increase, but conversely, the problem of odor during heat molding tends to occur. However, in the above range, a odor problem hardly occurs, and a sheet for a fiber-reinforced plastic molding can be obtained in which delamination does not occur even after repeated cutting steps.

As the binder component, polyester resins such as polyethylene terephthalate and modified polyethylene terephthalate, acrylic resins, styrene-(meth)acrylic acid ester copolymer resins, urethane resins, PVA resins and various starches, which are generally used in the production of nonwoven fabrics, are used. , Cellulose derivative, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, Polyvinyl acetate resin, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene-(meth)acrylic acid ester 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. Among them, the binder component preferably contains a copolymer containing at least one of a repeating unit derived from a monomer containing a methyl methacrylate and a repeating unit derived from a monomer containing an ethyl methacrylate. Further, these monomers may be copolymerized with other monomers such as styrene, vinyl acetate and acrylamide.
In addition, in this invention, "(meth)acrylate" means including both "acrylate" and "methacrylate", and "(meth)acrylic acid" means "acrylic acid" and "methacrylic acid." Is meant to include both.

Further, as the binder component preferable in the present invention, a polyester resin and a modified polyester resin can be mentioned. Polyethylene terephthalate (PET) is particularly preferable as the polyester resin. 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 preferable. The modified polyethylene terephthalate is preferably copolymerized polyethylene terephthalate (coPET), and examples thereof include urethane modified copolymerized polyethylene terephthalate. The polyester resin is compatible with the thermoplastic resin of the present invention at the time of heating and melting, and therefore, it is difficult to impair heat and the function of the resin even after cooling, and therefore, it is preferably used.
The copolymerized polyethylene terephthalate preferably has a melting point of 140° C. or lower, more preferably 120° C. or lower. Moreover, you may use the modified polyester resin as described in Japanese Patent Publication No. 1-30926. As a specific example of the modified polyester resin, a product name “Melty 4000” manufactured by Unitika Ltd. (fiber in which all the fibers are copolymerized polyethylene terephthalate) is particularly preferable. In addition, as the binder fiber having a core-sheath structure, the product name "Melty 4080" manufactured by Unitika, the product name "N-720" manufactured by Kuraray Co., Ltd., and the like can be preferably used.

In the present invention, the fiber-reinforced plastic molded sheet is subjected to wet papermaking to increase the strength/width ratio. Generally, 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 non-woven 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 the binder.

(Fiber shape)
In the present invention, the thermoplastic resin fiber and the reinforcing fiber are preferably chopped strands cut into a certain length. Further, the binder fiber is also preferably chopped strand. With such a configuration, various fibers can be uniformly mixed in the sheet for fiber-reinforced plastic molded body.

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

(Fiber reinforced plastic molding)
The sheet for a fiber-reinforced plastic molded product of the present invention can be processed into any shape according to the shape of the target molded product and the molding method. A single sheet of fiber-reinforced plastic molded product may be used alone, or may be laminated to have a desired thickness and heated and pressed by a hot press, or preheated by an infrared heater in advance and heated and pressed by a mold. be able to. As described above, the fiber-reinforced plastic molded product having excellent strength can be obtained by processing the sheet for a fiber-reinforced plastic molded product by a general method of heating and pressing.

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

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

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

In the fiber-reinforced plastic molded product of the present invention, most of the reinforced fibers are arranged substantially parallel to the surface of the fiber-reinforced plastic molded product, and therefore, the resin is ruptured due to the flow of the resin during the heat and pressure molding. Hateful. Therefore, it is possible to mold a fiber-reinforced plastic molded body that is thinner than the above range. For example, the thickness of the fiber-reinforced plastic molded body can be 100 μm or less. Further, the thickness of the fiber-reinforced plastic molded product of the present invention may be greater than 40 μm and 100 μm or less. Further, the thickness of the fiber-reinforced plastic molded product of the present invention can be made thicker than 20 μm and 40 μm or less. It is also possible to obtain a fiber-reinforced plastic molded product having a size of 10 μm or more and 20 μm or less.

Such a fiber-reinforced plastic molded product can be suitably used as a reinforcing sheet or a tape base material for bonding to both surfaces of a low-density core material to obtain a lightweight and high-strength member (laminate). The present invention may also relate to a laminate in which fiber-reinforced plastic moldings are bonded to both surfaces of a core material.
When the fiber-reinforced plastic molded product is attached to both surfaces of the low-density core material, the core material is, for example, a nonwoven fabric containing at least one material selected from natural pulp, synthetic pulp, inorganic fibers, organic fibers, and the like. Can be mentioned. Further, as the core material, the above-mentioned heat-pressed and molded non-woven fabric, or a porous body such as a foam made of a thermoplastic resin or a thermosetting resin 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 for adhering the core material and the fiber-reinforced plastic molding is a method of applying an adhesive to the core material to adhere the fiber-reinforced plastic molding, or a method of applying an adhesive to the fiber-reinforced plastic molding to adhere. Alternatively, a method of thermocompression-bonding the core material and the adhesive may be used, but the method is not limited thereto.

When the adhesive is applied to the fiber-reinforced plastic molded body, a pressure-sensitive adhesive layer or an adhesive layer may be provided on one side or both sides of the fiber-reinforced plastic molded body. In this case, release paper can be attached on the adhesive layer to improve the handling property. Since the fiber-reinforced plastic molded product of the present invention can be curved so as to have a radius of curvature as described later, when an adhesive layer is provided and release paper is further attached, the molded product is rolled up and transported. It becomes possible. Such a form is suitable for the distribution of products.

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

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

Furthermore, in the fiber-reinforced plastic molded body, most of the reinforcing fibers are arranged substantially parallel to the surface of the fiber-reinforced plastic molded body, so that if the thin molding is performed as described above, the radius of curvature R becomes It has a feature that cracks do not occur even when bent to 10 mm or less, 5 mm or less, and further 3 mm or less.
Taking advantage of this feature, it is processed into a tubular or spiral shape and used as a protective material for sensors, etc., or corrugated and processed into a corrugated shape, and a liner sheet is attached on both sides to make it lightweight and high strength. It is also possible to obtain a laminated body of.

In the fiber reinforced plastic molded body, most of the reinforced fibers among the reinforced fibers are arranged substantially parallel to the surface of the fiber reinforced plastic molded body, and therefore the compression strength is also excellent. Therefore, it can be suitably used also as a honeycomb-processed core material.

Although it is possible to obtain a plate-shaped fiber-reinforced plastic molded product by injection molding, a thin film can be obtained by obtaining a fiber-reinforced plastic molded product using the fiber-reinforced plastic molded product sheet of the present invention, and It has the advantage that it does not break or break during molding.
When a sheet for a fiber-reinforced plastic molded body is used as in the present invention, a thin molded body can be manufactured by adjusting the basis weight of the sheet for a fiber-reinforced plastic molded body. Particularly, in the sheet for a fiber-reinforced plastic molded product of the present invention, when the absolute value of the fiber orientation parameter (fp) of the reinforcing fibers in the thickness direction is 0.5 or more, the reinforcing effect in the plane direction is obtained and it is extremely thin. Even in the production of a thin molded product, it has a technical significance that breakage or breakage is unlikely to occur during molding. As a result, the thickness of the fiber-reinforced plastic molded product of the present invention can be greater than 40 μm and 100 μm or less. Further, the thickness of the fiber-reinforced plastic molded product of the present invention can be made thicker than 20 μm and 40 μm or less. It is also possible to obtain a fiber-reinforced plastic molded product having a size of 10 μm or more and 20 μm or less.

When manufacturing the fiber-reinforced plastic molded product of the present invention, the number of laminated sheets for the fiber-reinforced plastic molded product may be one, or a plurality of sheets may be laminated for heat and pressure molding. That is, in order to obtain a fiber-reinforced plastic molded body having a basis weight of 60 g/m ^2, a sheet for a fiber-reinforced plastic molded body of 60 g/m ² may be heated and pressed, or a fiber-reinforced plastic of 20 g/m ² may be molded. You may laminate|stack three sheets for molded objects, and you may also laminate two sheets for 10 g/m< ² > fiber-reinforced plastic molded objects, and two sheets for 20 g/m< ² > fiber-reinforced plastic molded objects. Good. When the number of stacked sheets is one or a small number, the stacking process is simplified, which is preferable from the viewpoint of production efficiency and manufacturing cost.

On the other hand, when a plurality of sheets for a fiber-reinforced plastic molded body are laminated, there is an advantage that the uniformity of the fiber-reinforced plastic molded body is improved and pinholes and the like are less likely to occur even if it is thin. Furthermore, the lower the basis weight of the fiber-reinforced plastic molded body sheet, the thinner the thickness of the fiber-reinforced plastic molded body sheet, so that the orientation of the reinforcing fibers in the thickness direction of the fiber-reinforced plastic molded body tends to be a fixed 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 product is improved and the amount of deflection is reduced.

When laminating a plurality of sheets for a fiber-reinforced plastic molded body, a sheet for a fiber-reinforced plastic molded body containing different types of reinforcing fibers or thermoplastic resin fibers is 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 body containing carbon fiber as a reinforcing fiber and a sheet for a fiber-reinforced plastic molded body containing glass fiber as a reinforcing fiber can be laminated. In this case, carbon fiber and glass fiber have different tensile strength, elongation at break, electrical conductivity, and thermal conductivity, so the strength, electromagnetic shielding, thermal conductivity, etc. can be adjusted by appropriately adjusting the number of laminated layers. Can be adjusted according to the application.
Further, in the case where the core material is adhered to one surface, the thermoplastic resin contained in the sheet for a fiber-reinforced plastic molded body arranged on the adhesive surface is a resin excellent in adhesiveness with the core material, for example, having a low melting point. It is also possible to change to those having adhesiveness, those 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 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 surface parallel to the surface of the fiber-reinforced plastic molded body is high, the fiber-reinforced plastic molded body 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 orthogonal to the orientation direction of the reinforcing fibers (CD direction) in the fiber-reinforced plastic molding, It means the strength represented by the following formula.
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 between the bending strength of the fiber-reinforced plastic molded body in the first direction 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, still more preferably 5 or more. 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 product within the above range, it is possible to obtain a fiber-reinforced plastic molded product having increased strength in a specific direction. Such a fiber-reinforced plastic molding is preferably used for structural parts used in automobiles, aircrafts, etc., which require mechanical strength in one direction.

(Method for molding fiber-reinforced plastic molding)
The method for molding the sheet for a fiber-reinforced plastic molded product of the present invention is not particularly limited, and can be selected according to the application of the molded product and the like. A typical method is press molding. In addition, as a method of press molding, among various existing press molding methods, an autoclave method that is often used when producing a molded body member of a large aircraft or a mold press whose process is relatively simple The method is preferred. The autoclave method is preferable from the viewpoint of obtaining a high-quality molded body with few voids. On the other hand, from the viewpoint of energy consumption in equipment and molding process, simplification of molding jigs and auxiliary materials to be used, molding pressure, and degree of freedom of temperature, metal molds are used for molding. It is preferable to use a mold pressing method, and these can be selected according to the application.

As the die pressing method, a heat and cool method or a stamping molding method can be adopted. In the heat and cool method, a sheet for fiber-reinforced plastic molding is placed in advance in a mold, pressure and heat are applied together with mold clamping, and then the sheet is cooled by cooling the mold while the mold is clamped. Is a method for obtaining a molded body. In the stamping molding method, the sheet is heated in advance with a heating device such as a far infrared heater, a heating plate, a high temperature oven, and a dielectric heating device, and the thermoplastic resin is placed in a molded body mold in a state of being melted and softened. In this method, the mold is closed, the mold is clamped, and then pressure cooling is performed. Further, when the temperature at the time of molding is relatively low, such as when obtaining a molded article having a low density, the hot pressing method can be adopted.

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 eliminating decomposed gas and mixed air during molding from the mold, but in order to suppress excessive resin outflow, minimize the open part during molding process and It is also preferable to adopt a shape that suppresses outflow to the outside of the mold.

Furthermore, a die having at least one selected from a punching mechanism and a tapping mechanism can be used for the die. By using a two-stage press mechanism or the like, it is possible to punch the molded body continuously after hot pressing. Further, depending on the purpose of use, the molded body can be provided with protrusions or screw holes for reinforcing the strength and processing of ribs, bosses, etc., and can be provided with a pattern for the purpose of imparting designability.

It is also possible to bond more complicated shaped members by outsert molding or insert molding at the same time as molding the fiber-reinforced plastic molded body sheet or after molding.

When the fiber-reinforced plastic molded body is molded from the fiber-reinforced plastic molded body sheet, specifically, the fiber-reinforced plastic molded body sheet is preferably heated and pressed at a temperature of 150 to 600°C. The heating temperature is preferably a temperature at which the thermoplastic resin flows and the reinforcing fibers do not melt.

The pressure for molding the fiber-reinforced plastic molding is preferably 5 to 20 MPa. Further, the rate of temperature increase until reaching the desired holding temperature is preferably 3 to 20° C./minute, the holding time at the desired hot press temperature is 1 to 30 minutes, and then the temperature at which the molded product is taken out (200° C. It is preferable that the cooling rate is 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 to slowly cool by air cooling from the holding temperature of the hot press to the glass transition temperature of the matrix resin at 0.1 to 3° C./min. It is also possible to perform hot press molding using rapid heating and rapid cooling (heat and cool) molding, and the temperature rising and cooling rates in this case are 30 to 500° C./min. Furthermore, in the case of using an infrared heater, heating can be performed at a temperature of 150 to 600° C., preferably 200 to 500° C. for 1 to 30 minutes, and then molding can be performed at a pressure of 30 to 150 MPa.

(Method for producing sheet for fiber-reinforced plastic molded body)
The manufacturing process of the sheet for a fiber-reinforced plastic molded product of the present invention includes a process of wet-papermaking a slurry in which reinforcing fibers and a thermoplastic resin are mixed.

In the step of mixing the reinforcing fiber and the thermoplastic resin to obtain the slurry, each fiber can be sufficiently dispersed by adjusting the concentration of the dispersion liquid and the viscosity of the solvent. The viscosity of the solvent can be adjusted by a method such as adding a polyacrylamide polymer. By sufficiently dispersing the fibers, the fibers in the sheet for a fiber-reinforced plastic molded body are uniformly mixed and made into paper. As a result, in the fiber-reinforced plastic molded body obtained by heat-pressing and molding this sheet, for example, it is possible to prevent the proportion of the resin from increasing partially, and the bending strength of the fiber-reinforced plastic can be increased. In the mixing step, it is preferable to disperse the reinforcing fibers in a single fiber form.

When making a sheet for a fiber-reinforced plastic molded body, the viscosity of the dispersion medium of the slurry at 25° C. (however, according to the measuring method specified in JIS Z 8803 “Viscosity measuring method for liquid”) is 1.00 mPa. It is preferably more than •s and 4.00 mPa·s or less, and more preferably 1.05 to 2.00 mPa·s.
The slurry referred to here is the slurry immediately before the papermaking process, and is the slurry in the inlet. Further, when measuring the viscosity of the dispersion medium of the slurry, 500 ml of the slurry in the inlet is sampled and the filtrate obtained by filtering the fiber with a 150 mesh metal screen is used.

The viscosity of the dispersion medium of the slurry can be adjusted by adding a polyacrylamide-based viscous agent to the inlet. By setting the viscosity of the dispersion medium of the slurry within the above range, it is possible to suppress the turbulence of the flow of the dispersion liquid in the vicinity of the wire and form a laminar flow. Accordingly, the fiber orientation parameter (fp) in the thickness direction and the plane direction of the sheet for a fiber-reinforced plastic molded body can be set within a desired range.

The wet papermaking step is preferably a step of making a paper using an inclined type paper machine. And, the wire of the inclined type paper machine preferably 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 the ratio of the supply speed of the slurry containing the reinforcing fiber and the binder component and the wire traveling speed, and is represented by the 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 called "push formation". Further, when the jet wire ratio is 1 or less, the slurry supply speed is slower than the wire traveling speed, and this case is referred to as "pull formation".
In the present invention, the jet wire ratio is set in the above range and the paper is made in the “drawing formation”, whereby the fiber orientation parameter (fp) in the thickness direction of the sheet for fiber reinforced plastic molding can be set within a desired range. .. Furthermore, the fiber orientation parameter (fp) in the plane direction of the fiber-reinforced plastic molded sheet can be set within a desired range.

The wet paper making step may be a step of making a paper using a cylinder paper machine or a fourdrinier paper machine instead of the inclined paper machine. When performing papermaking using a cylinder paper machine, the diameter of the cylinder of the cylinder paper machine is preferably 80 cm or more. By setting the diameter of the cylinder of the cylinder paper machine in 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. It becomes easy to orient. Thereby, the strength in a specific direction can be further increased in the fiber-reinforced plastic molded body.

The papermaking speed in the case of performing papermaking using a cylinder 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 unidirectional, and most of the reinforcing fibers can be easily oriented so as to be parallel to the surface of the fiber-reinforced plastic molded body. Thereby, the strength of the fiber-reinforced plastic molded product in a specific direction can be further increased.

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

The inclination wire of the inclined type paper machine preferably has an air permeability of 250 cm ³ /cm ² /sec or more. The air permeability of the wire can be appropriately adjusted by the viscosity of the dispersion medium of the slurry in the inlet described above.

In the step of producing the sheet for a fiber-reinforced plastic molded body, the binder component may be added after the paper making step. For example, a solution containing a binder component or an emulsion containing a binder component may be internally added to, coated on or impregnated in a paper-made sheet, and dried by heating. By providing such a step, it is possible to prevent the surface fibers of the sheet for a fiber-reinforced plastic molded body from scattering, fluffing, and falling off, and to obtain a sheet for a fiber-reinforced plastic molded body having excellent handleability.

After the solution containing the binder component or the emulsion containing the binder component is internally added to, coated or impregnated with, the sheet for fiber-reinforced plastic molding, it is preferable to rapidly heat the sheet for fiber-reinforced plastic molding. 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 body. Furthermore, the binder component can be localized in the form of a wet film.

(Uses of fiber reinforced plastic moldings)
Examples of applications of the fiber-reinforced plastic molded body include, for example, "OA equipment, mobile phones, smartphones, personal digital assistants, portable electronic devices such as tablet PCs and digital video cameras, housings for air conditioners and other home appliances, and housings. Reinforcing materials such as ribs to be attached, civil engineering such as "struts, panels, reinforcing materials", building material parts, "various frames, bearings for wheels, 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 reinforcing materials", "instrument panels, interior parts such as seat frames", or "gasoline tanks, various piping," Fuel systems such as various valves, exhaust systems, or intake systems parts", "Engine cooling water joints, thermostat bases for air conditioners, headlamp supports, pedal housings," automotive parts, motorcycle parts, "winglets, spoilers," etc. Parts for railway vehicles, parts for railway vehicles such as "seat members for rail cars, outer panels, reinforcements attached to outer panels, ceiling panels, air outlets for air conditioners," and "resin (thermosetting Reinforcement material for molded products made of resin and thermoplastic resin, reinforcement material for molded products made of resin and reinforcing fiber, plant-derived sheet (kraft paper, cardboard, oil resistant paper, insulating paper, conductive paper, release paper, impregnated paper) , Glassine paper, cellulose nanofiber sheet, etc.) and the like. Furthermore, since the fiber-reinforced plastic molded product of the present invention is excellent in flame retardancy even if it is thin, it can be suitably used also as a substrate for electrical insulation by using glass fiber having high electrical insulation as the reinforcing fiber.
As described above, since the fiber-reinforced plastic molded product of the present invention has high strength and high flame retardancy, it has high safety, and therefore has a high level of safety. It is preferably used for parts, civil engineering, panels for building materials, and various other purposes.

The features of the present invention will be described more specifically below with reference to Examples and Comparative Examples. The 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 limitedly interpreted by the following specific examples. In the following, Examples 1 to 3 are to be read as Reference Examples 1 to 3, respectively.

<Example 1>
A carbon fiber having a fiber length of 12 mm (T700, manufactured by Toray Industries, Inc.) was added to water so that the slurry concentration became 0.5%, and Emanone (registered trademark) 3199V (manufactured by Kao Corporation) was used as a dispersant. It was added in an amount of 1 part by mass with respect to parts by mass. Incidentally, Emanone 3199V was dissolved in water in advance so as to be an aqueous solution having a concentration of 0.5% and added. After that, stirring was performed for 30 seconds using a waste paper disaggregation pulper to carry out 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 powdery anionic polymer polyacrylamide thickener (MT Aqua Polymer Co., Ltd., Sumifloc) was dissolved was prepared. The powdery anionic polymer polyacrylamide thickener was added so as to be 0.1% by mass relative to the total mass of the aqueous solution. This aqueous solution was added to the above carbon fiber slurry. The amount of the aqueous solution added was adjusted so that the solid content of the thickener was 60 ppm with respect to the total mass of the aqueous solution. Then, the mixture was stirred and dispersed until the carbon fibers became monofilaments.

Next, a mass mixing ratio of nylon 6 fiber having a thickness of 2.2 dtex and fiber length of 15 mm (Toray Industries, Inc., Amilan, fiber length 15 mm) and PVA fiber (Kuraray Co., Ltd., VPB-105-2) used as a binder are used. Weighed so as to be in Table 1. This was poured into water so that the slurry concentration would be 10% to obtain a thermoplastic resin slurry. Since the 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.

This fiber slurry is continuously fed to an inclined paper machine equipped with a Yankee dryer-type drying equipment, is made at a paper making speed of 30 m/min, and has a basis weight of 50 g/m ^2. 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 the measuring method specified in JIS Z 8803 “Viscosity measuring method 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 inlet slurry and filtering the fibers with a 150-mesh metal screen. The viscosity of the dispersion medium of the slurry was adjusted by continuously adding an aqueous solution prepared by dissolving an anionic polymer polyacrylamide thickener (Sumifloc, manufactured by MT Aqua Polymer Co., Ltd.) in circulating white water.

In addition, the inclined type paper machine used in Example 1 was provided with four suction boxes (dehydration boxes) in the inclined wire portion. FIG. 2 is a diagram illustrating the configuration of the inclined paper machine 100 used in the examples. As shown in FIG. 2, the slant type paper machine 100 includes a first suction box 101, a second suction box 102, and a third suction box below a slanting wire 120 provided at a bottom portion of an inlet 110. 103 and a fourth suction box 104 are provided.
In addition, in Example 1, the wire constituting the inclined wire portion had a gas permeability of 350 cm ³ /cm ² /sec when a differential pressure of 125 Pa was applied. In Example 1, the ratio of the dehydration amount of each suction box when the total amount of circulating white water dehydrated from the four suction boxes is 100 is shown in Table 1 by adjusting the suction force of each suction box. I made it as follows.
Further, the jet wire ratio of the wires of the inclined paper machine was adjusted to be as shown in Table 1 by controlling the total amount of circulating white water. In this way, a sheet for fiber-reinforced plastic molding was produced. The absolute value of the fp value of the obtained sheet for fiber-reinforced plastic molding is shown in Table 1.

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

<Example 2>
Example 2 is the same as Example 1 except that the suction force of the suction box is adjusted so that the dehydration amount of all suction boxes is the same amount as in Example 1, and the fiber-reinforced plastic molding is the same. A sheet and a fiber-reinforced plastic molded body were produced.

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

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

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

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

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

<Example 11>
A sheet for a fiber-reinforced plastic molded product and a fiber-reinforced plastic molded product 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., Ltd., fiber diameter 30 μm, fiber length 15 mm). ..

<Example 12>
A sheet for a fiber-reinforced plastic molded product and a fiber-reinforced plastic molded product were obtained 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.). It was made.

<Example 13>
A sheet for a fiber-reinforced plastic molded product and a fiber-reinforced plastic molded product were obtained 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). It was made.

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

(Evaluation)
<Measurement of fiber orientation parameter (fp value) of reinforcing fibers in the 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 curing type embedding epoxy resin (Aronix LCA D-800 manufactured by JEOL Ltd.) was cut. A dropper was used to cover the entire surface of the test piece to impregnate the test piece, and the test piece was irradiated with ultraviolet rays to be cured. Then, a slice master HS-1 manufactured by JASCO Corporation was used to cut out a specimen having a width of 0.4 mm and a length of 10 mm from the specimen for cross-section observation. The cutting direction was the BB′ direction in FIG. The BB' direction is a direction parallel to the reference line in the plane direction obtained by the method described later.
The cross section in the thickness direction of the obtained test piece was enlarged 300 times using a microscope manufactured by Ens Co., Ltd., and the reinforcing fiber was observed by transmitted light. Here, a continuous measurement area of 1.5 mm ^{2 in} the cross section was observed. Further, the observation was carried out 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. The angle θi (i=1 to n) with respect to the reference line set by the method described later is set for all the reinforcing fibers (the number of fibers is n) that are visible in the observation image and that are present in the measurement region. It was measured. The orientation angle θi was an angle of 0° or more and less than 180°, which was measured by measuring the angle in the clockwise direction with respect to the reference line. Then, the fiber orientation parameter in the thickness direction was calculated using the following equation (1) from the angle θi of the fiber with respect to the set reference line.
fp=2×Σ(cos ² θ _i /n)-1 Expression (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 visible n reinforcing fibers present in the measurement region were 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)) of the reinforcing fiber when the provisional reference line p was calculated using the following formula.
fp(p)=2×Σ(cos ² α(p) _i /n)−1
(I=1, 2, 3,..., N)
Then, the temporary reference line p by ± 1 °, the provisional reference line is rotated until _{± 90 ° (p + z,} p -z (z = 1~90)) takes a temporary reference line p _{+ z} The angle between the temporary reference line p _−z and n fibers was 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 line (p _+z , p- _z (z=1 to 90)) and the fiber orientation parameter (fp(p± _z )) of the reinforcing fiber were calculated using the following formulas.
fp(p± _z )=2×Σ(cos ² α(p± _z ) _i /n)-1
(I=1, 2, 3,..., N)
In this way, the provisional reference line set when the maximum value of the absolute values of the obtained fp(p) value and fp(p± _z ) value was obtained was used as the reference line.

<Measurement of fiber orientation parameter (fp value) of reinforcing fiber in the plane direction>
The sheets for fiber-reinforced plastic molded bodies obtained in Examples and Comparative Examples were cut out so as to have a width of 3 cm and a length of 3 cm, and the test piece was sandwiched with a slide glass, and one surface of the test piece was observed with an optical microscope. I observed. A microscope manufactured by Keyence Corp. was used as an optical microscope, and the reinforcing fibers were observed with reflected light after being magnified 300 times. Here, a continuous measurement area of 2.0 mm ^{2 on} the one surface was observed. The angle θi (i=1 to m) with respect to the reference line set by the method described below is set for all the reinforcing fibers (the number of fibers is m) that are visible in the observation image and that are present in this measurement region. It was measured. The orientation angle θi was an angle of 0° or more and less than 180°, which was measured by measuring the angle in the clockwise direction with respect to the reference line. 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 formula (2).
fp=2×Σ(cos ² θ _i /m)−1 Equation (2)
Then, the other surface was also measured in the same manner, the average value of the one surface and the other surface was obtained, and this was used as the fiber orientation parameter (fp) in the plane direction. The measurement area on one surface and the measurement area on the opposite surface were overlapped in a plan view. In addition, in both observations of one surface and the opposite surface, the 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 m visible reinforcing fibers present in the measurement region were 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 was calculated using the following formula.
fp(p)=2×Σ(cos ² α(p) _i /m)−1
(I=1, 2, 3,..., m)
Next, the provisional reference line p (p _+z , p _-z (z = 1 to 90)) obtained by rotating the provisional reference line p by ±1° until it becomes ±90° is taken, and the provisional reference line p _{+z is obtained.} Then, the angle between the provisional reference line p _−z and 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 line (p _+z , p- _z (z=1 to 90)) and the fiber orientation parameter (fp(p± _z )) of the reinforcing fiber were calculated using the following formulas.
fp(p± _z )=2×Σ(cos ² α(p± _z ) _i /m)−1
(I=1, 2, 3,..., m)
In this way, the provisional reference line set when the maximum value of the absolute values of the obtained fp(p) value and fp(p± _z ) value was obtained was used as the reference line.

<Measurement of bending strength>
The fiber reinforced plastic moldings for flexural strength measurement obtained in Examples and Comparative Examples were subjected to a fiber orientation direction (machine direction, hereinafter referred to as MD) and a fiber orientation according to the JIS K 7074 carbon fiber reinforced plastic bending test method. Was measured in a direction perpendicular to (cross direction, hereinafter referred to as CD), and the strength and the strength 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, formed from a sheet for a fiber-reinforced plastic molded body having an absolute fp value in the thickness direction of 0.5 or more and an absolute fp value in the plane direction of 0.25 or more. It can be seen that the fiber-reinforced plastic molded product produced 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 increased.

Further, comparing Examples 1 to 4, it can be seen that dehydration in the inclined wire portion can adjust the fp value in the thickness direction to a more preferable range by increasing the dehydration amount in the first half portion of the wire. This is because the portion where the distance from the liquid surface to the wire in the inlet is long does not easily become a turbulent flow because the flow velocity of the slurry is slow.By forming a wet web near this, the fibers can be controlled in the thickness direction of the sheet. It is thought to be easier to do. In FIG. 2, the suction box 101 has the longest distance from the liquid surface to the wire.
Further, looking at Examples 1 to 6, although the fp value can be set in a more preferable range by increasing the viscosity of the dispersion medium in the inlet, the dispersion medium in the inlet can be reduced by decreasing the air permeability of the wire. It can be seen that the fp value can be set in a more preferable range even if the viscosity is low. This means that the amount of the sticky agent added during papermaking can be reduced by using a wire having a low air permeability. As a result, the manufacturing cost can be reduced and the contamination of the papermaking tool due to the sticky agent can be reduced.

5 Sheet for Fiber Reinforced Plastic Molded Body 20 Reinforced Fiber 25 Thermoplastic Resin 40 Embedding Epoxy Resin 45 Cross Section Observation Test Piece 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 showing the angle of the reinforcing fiber with respect to the reference line R Line showing the angle of the reinforcing fiber with respect to the reference line

Claims (5)

Reinforcement fiber, a slurry mixed thermoplastic resin fiber, including a step of wet papermaking,
The wet paper making step is a step of making paper using an inclined paper machine,
The wire of the inclined paper machine runs so that the jet wire ratio is 0.98 or less ,
Below the inclined wire of the inclined paper machine, a first suction box, a second suction box, a third suction box and a fourth suction box are provided, and the dehydration amount of the first suction box is all The method for producing a sheet for a fiber-reinforced plastic molded body, which is 35 to 65 when the dehydration amount in the suction box is 100 . The method for producing a sheet for a fiber-reinforced plastic molded body according to claim 1, wherein the wire of the inclined type paper machine runs so that the jet wire ratio becomes 0.90 or less. The method for producing a sheet for a fiber-reinforced plastic molded product according to claim 1, wherein the dispersion medium of the slurry has a viscosity at 25° C. of more than 1.00 mPas and 4.00 mPas or less. The method for producing a sheet for a fiber-reinforced plastic molded product according to any one of claims 1 to 3, wherein the tilted wire of the tilted paper machine has an air permeability of 250 cm ³ /cm ² /sec or more. The slurry, a reinforcing fiber slurry obtained by dispersing reinforcing fibers, fiber-reinforced plastic molded body according to any one of claims 1 to 4, which is a thermoplastic resin fiber slurry obtained by mixing a dispersed thermoplastic resin slurry Sheet manufacturing method.