JP2024019021A - Fiber-reinforced resin sheet, method for manufacturing fiber-reinforced resin sheet, and laminate - Google Patents

Abstract

The present invention aims to provide a thin fiber-reinforced resin sheet that contributes to improving the quality of molded products, a method for producing the fiber-reinforced resin sheet, and a laminate using the fiber-reinforced resin sheet. [Solution] The film includes a thermoplastic resin film and a plurality of continuous carbon fibers oriented in the same direction, has a regular transmittance of light of 1% or less at a wavelength of 550 nm, and has a thickness of 90 μm. Providing the following fiber reinforced resin sheet. [Selection diagram] Figure 1

Description

The present invention relates to a fiber-reinforced resin sheet, a method for manufacturing a fiber-reinforced resin sheet, and a laminate.

Fiber-reinforced resin sheets containing carbon fiber and resin are lightweight and have excellent strength and durability, so they are used in a wide range of applications such as automobiles, aircraft, temporary civil engineering materials, electrical and electronic equipment, toys, home appliances, and sporting goods. used in the field.

For example, as an example of a fiber-reinforced resin sheet, that of Patent Document 1 is known. Patent Document 1 discloses a fiber-reinforced resin sheet (thermoplastic carbon fiber prepreg) that can be formed by a film stacking method by disposing resin films on one side and the other side of spread sheet-like carbon fibers. Disclosed. More specifically, the fiber reinforced resin sheet described in Patent Document 1 has a resin film thickness of 8 μm or more and 55 μm or less, a tear strength in the width direction according to JIS 7128 of 28 mN or more, and heat shrinkage in the width direction. This is a fiber-reinforced resin sheet characterized in that the fiber-reinforced resin sheet has a fiber-reinforced resin sheet of less than 7%. Conventional sheets had a problem in that it was difficult to increase the strength of the resulting fiber-reinforced resin sheet because the thick resin film lowered the carbon fiber content (Vf value) of the sheet. However, according to the fiber-reinforced resin sheet described in Patent Document 1, it is stated that it is possible to make the sheet thinner and to improve the strength by increasing the carbon fiber content of the fiber-reinforced resin sheet. ing.

Japanese Patent Application Publication No. 2020-122137

However, in a thin fiber-reinforced resin sheet, there are likely to be many continuous gaps (gaps) between carbon fibers, and when a product is molded using a sheet with many gaps, the surface quality may be poor. Problems were likely to occur, and the quality of the molded product might not be stable.

The present invention has been made in view of the above circumstances, and provides a thin fiber-reinforced resin sheet that contributes to improving the quality of molded products, a method for manufacturing the fiber-reinforced resin sheet, and a fiber-reinforced resin sheet. The purpose is to provide a laminate using.

As a result of various studies, the present inventors have found that the above object can be achieved by the following present invention. That is, the fiber reinforced resin sheet according to one aspect of the present invention includes a thermoplastic resin film and a plurality of continuous carbon fibers oriented in the same direction, and has a specular light transmittance at a wavelength of 550 nm. 1% or less, and the thickness is 90 μm or less.

Carbon fiber has large absorption in the visible light region including a wavelength of 550 nm. Therefore, it is thought that the more gaps there are between carbon fibers in the fiber-reinforced resin sheet, especially the gaps that are continuous gaps between carbon fibers, the higher the regular transmittance of light at a wavelength of 550 nm of the fiber-reinforced resin sheet becomes. Therefore, the fact that the specular transmittance of light at a wavelength of 550 nm of the fiber-reinforced resin sheet is 1% or less means that the gaps in the fiber-reinforced resin sheet are sufficiently small. By molding a product using this sheet, quality such as surface quality of the molded product can be improved.

Further, since the thickness of the fiber-reinforced resin sheet is 90 μm or less, there is no possibility that the fluidity of the resin and fibers becomes too poor during molding due to the thickness of the fiber-reinforced resin sheet being too thick. Therefore, the shapeability of the product obtained by molding the sheet can be improved.

From the above, it is possible to provide a thin fiber-reinforced resin sheet that contributes to improving the quality of molded products.

Further, in the fiber-reinforced resin sheet, it is preferable that the aperture ratio, which is the area ratio of the portion where the carbon fibers are not present in the fiber-reinforced resin sheet, is 10% or less.

Furthermore, in the fiber-reinforced resin sheet, it is preferable that the number of gaps that are continuous from one end to the other end in a 50 mm square area arbitrarily extracted from the fiber-reinforced resin sheet is 15 or less.

Moreover, in the fiber-reinforced resin sheet, it is preferable that the maximum width of the gap is 1 mm or less.

Each of the above aspects makes it possible to more reliably provide a thin fiber-reinforced resin sheet that contributes to improving the quality of molded products.

A method for producing a fiber-reinforced resin sheet according to another aspect of the present invention is the method for producing the fiber-reinforced resin sheet described above, wherein fiber bundles of carbon fibers are opened at a spreading ratio of 25% to 40% to form a band. The method includes spreading the carbon fibers in the same direction and laminating them on both sides of the resin film in a state where the opened carbon fibers are oriented in the same direction.

A method for producing a fiber-reinforced resin sheet according to still another aspect of the present invention is the method for producing the fiber-reinforced resin sheet, which comprises opening fiber bundles of carbon fibers at a spreading rate of 20% or more and 30% or less. The method includes spreading the carbon fibers into a belt shape and laminating them on one side of the resin film in a state in which the opened carbon fibers are oriented in the same direction.

In still another method of manufacturing a fiber-reinforced resin sheet with a curved surface according to the present invention, a first carbon fiber bundle and a second carbon fiber bundle are each opened at a spreading ratio of 20% or more and 55% or less. A state where the first carbon fiber after opening and the second carbon fiber after opening are oriented in the same direction between the first resin film and the second resin film. Including laminating with.

Any of the above methods can produce a thin fiber-reinforced resin sheet that contributes to improving the quality of molded products.

A laminate according to still another aspect of the present invention includes a plurality of the fiber-reinforced resin sheets, wherein the fiber directions of the carbon fibers are in the same direction or have angular differences from each other in plan view. are laminated in the thickness direction.

With such a configuration, it is possible to provide a laminate that contributes to improving the quality of molded products.

According to the present invention, it is possible to provide a thin fiber-reinforced resin sheet that contributes to improving the quality of molded products, a method for manufacturing the fiber-reinforced resin sheet, and a laminate using the fiber-reinforced resin sheet.

FIG. 1 is a perspective view showing an example of a fiber reinforced resin sheet in this embodiment. FIG. 2 is a diagram showing an example of a schematic configuration of an apparatus for manufacturing a fiber-reinforced resin sheet in this embodiment. FIG. 3 is a diagram for explaining an example of a method of laminating a plurality of fiber-reinforced resin sheets to form a laminate according to the present embodiment.

Hereinafter, embodiments according to the present invention will be specifically described, but the present invention is not limited thereto.

<Fiber reinforced resin sheet>
(Composition of fiber reinforced resin sheet)
First, the structure of the fiber-reinforced resin sheet of this embodiment will be specifically explained below with reference to FIG. FIG. 1 is a perspective view showing a fiber reinforced resin sheet 1 according to this embodiment. As shown in FIG. 1, the fiber reinforced resin sheet 1 includes a thermoplastic resin film 2 and a plurality of carbon fibers 3. A plurality of carbon fibers 3 are laminated on the resin film 2 with their fiber directions oriented in the same direction. Specifically, the plurality of carbon fibers 3 are laminated on the resin film 2 with their fiber directions substantially parallel to the longitudinal direction of the fiber-reinforced resin sheet 1 and oriented in the same direction.

Here, in this specification, "carbon fibers are laminated on a resin film" means that carbon fibers are arranged and fixed in a layer on one surface (at least one surface in the thickness direction) of the resin film. . In this case, each carbon fiber can be fixed to the resin film by an appropriate method such as fusion bonding, compression bonding, or adhesion. Further, when carbon fibers are fixed by fusion bonding or compression bonding, a part or all of each carbon fiber may be impregnated from the surface of the resin film into the inside.

The specific meaning of such "lamination" changes depending on the physical property values and shape of the resin film, the type of treatment performed for lamination, the conditions thereof, etc. That is, "lamination" in this specification means that heating, cooling, pressure treatment, etc. may be performed as necessary during "lamination".

Moreover, in the fiber-reinforced resin sheet of this embodiment, the plurality of carbon fibers may be laminated on at least one surface of the resin film. More specifically, for example, a plurality of carbon fibers may be laminated on one side of the resin film, or a plurality of carbon fibers may be laminated on both sides of the resin film. Furthermore, the fiber-reinforced resin sheet may be formed such that two or more resin films sandwich a plurality of carbon fibers. More specifically, for example, the fiber reinforced resin sheet includes two or more resin films, a plurality of carbon fibers are laminated on one resin film, and another resin film is laminated with the plurality of carbon fibers. It may be placed on the surface of the laminated resin films.

Next, each component included in the fiber reinforced resin sheet of this embodiment will be explained below.

The resin film included in the fiber reinforced resin sheet of this embodiment is a film containing a thermoplastic resin. Furthermore, the resin film may contain other additives in addition to the thermoplastic resin, if necessary.

The thermoplastic resin is not particularly limited, but includes polyamide (particularly PA6, PAMXD6, PA9T), polyolefin, polyester, polyacetal, polyphenylene sulfide, polycarbonate, acrylic resin, acrylonitrile-butadiene-styrene copolymer (ABS), and polyamideimide. , polysulfone, polyphenylsulfone, polyetherimide, polyethersulfone, polyetheretherketone, polyetherketoneketone, polyimide, polyarylate, fluororesin, liquid crystal polymer, thermoplastic epoxy resin, and the like. Further, a polymer alloy obtained by mixing two or more of these thermoplastic resins may be used as the material for the resin film.

In addition, when the fiber reinforced resin sheet includes two or more resin films, the two or more resin films may be made of the same material or may be made of different materials.

The method for producing the resin film is not particularly limited, and the resin film can be produced by any method known to those skilled in the art. Examples include the T-die method and the calendar method. Further, by using a coextrusion method or a lamination method, it is possible to increase the thickness of the resin film or to laminate resin films having different resin compositions.

The thickness of the resin film is not particularly limited, but is preferably 5 μm or more and 50 μm or less. By setting the thickness of the resin film within the above range, when the fiber-reinforced resin sheet is molded so that the sheet thickness is within the predetermined range, the fiber-reinforced resin sheet has fewer gaps and contributes to improving the quality of the molded product. It is thought that it can be obtained more reliably.

The upper limit of the thickness of the resin film is more preferably 45 μm or less, and even more preferably 40 μm or less. Further, the lower limit of the thickness is more preferably 7 μm or more, and even more preferably 10 μm or more.

The plurality of carbon fibers included in the fiber reinforced resin sheet of this embodiment are continuous fibers whose fiber directions are oriented in the same direction. The plurality of carbon fibers are a plurality of carbon fibers opened from a carbon fiber bundle, and as described above, the plurality of carbon fibers are laminated on the resin film while being oriented in the same direction. The fiber-spreading method and fiber-spreading rate will be explained in detail in (method for producing fiber-reinforced resin sheet) below.

The carbon fibers are not particularly limited, but include, for example, polyacrylonitrile (PAN)-based, petroleum/coal pitch-based, rayon-based, lignin-based, and the like. Among these, PAN-based carbon fibers with high strength are preferred. Note that carbon fibers may be used alone or in an appropriate combination of two or more types, as long as the fiber directions are oriented in the same direction.

In addition, in the fiber-reinforced resin sheet, when two or more layers of carbon fibers are included, such as when a plurality of carbon fibers are laminated on both sides of the resin film, the two or more layers of carbon fibers are They may be made of the same type of carbon fiber or may be made of different types of carbon fiber.

(Physical properties of fiber reinforced resin sheet)
The regular transmittance of the fiber reinforced resin sheet of this embodiment at a wavelength of 550 nm is 1% or less. Here, in this specification, "regular transmittance" refers to transmittance of light that does not include diffused light. Carbon fiber has large absorption in the visible light region including a wavelength of 550 nm. Therefore, it is thought that the more gaps there are between carbon fibers in the fiber-reinforced resin sheet, especially the gaps that are continuous gaps between carbon fibers, the higher the regular transmittance of light at a wavelength of 550 nm of the fiber-reinforced resin sheet becomes. Therefore, the fact that the specular transmittance of light at a wavelength of 550 nm of the fiber-reinforced resin sheet is 1% or less means that the gaps in the fiber-reinforced resin sheet are sufficiently small. Further, the lower limit is not particularly limited, and the closer the value is to 0%, the fewer the gaps are, and it is possible to more reliably obtain a fiber-reinforced resin sheet that contributes to improving the quality of molded products.

The specular transmittance of the fiber-reinforced resin sheet at a wavelength of 550 nm is preferably 0.7% or less, more preferably 0.5% or less.

In this embodiment, the specular transmittance can be measured using a commercially available spectrophotometer (for example, V-570 manufactured by JASCO Corporation).

The thickness of the fiber reinforced resin sheet of this embodiment is 90 μm or less. By having a thickness of 90 μm or less, the thickness of the fiber-reinforced resin sheet will not be too thick and the fluidity of the resin and fibers will become too poor during molding, and the product obtained by molding the sheet can be shaped. can improve sex. Moreover, if the thickness is too thick, the physical properties of the product obtained by molding may deteriorate. Specifically, for example, if the thickness is too thick, the carbon fibers may not be sufficiently impregnated with the resin, which may cause deterioration in the physical properties of the product obtained by molding. Therefore, when the thickness is 90 μm or less, deterioration in physical properties of a product obtained by molding can be suppressed.

The thickness of the fiber-reinforced resin sheet is preferably 80 μm or less, more preferably 75 μm or less, and more preferably 70 μm or less. Further, the lower limit of the thickness is not particularly limited, but is preferably 30 μm or more, more preferably 35 μm or more.

Moreover, it is preferable that the aperture ratio of the fiber reinforced resin sheet of this embodiment is 10% or less. In addition, in this specification, "aperture ratio" refers to the area ratio of a portion where carbon fibers do not exist in a fiber-reinforced resin sheet, and can be measured, for example, by the method shown in Examples. When the aperture ratio is 10% or less, it is possible to more reliably obtain a fiber-reinforced resin sheet that has few gaps and contributes to improving the quality of molded products. Further, the lower limit of the aperture ratio is not particularly limited, and the smaller the aperture ratio is, the fewer the gaps are, and it is possible to more reliably obtain a fiber-reinforced resin sheet that contributes to improving the quality of the molded product.

The aperture ratio of the fiber-reinforced resin sheet is more preferably 9% or less, and even more preferably 8% or less.

In the fiber reinforced resin sheet of this embodiment, the number of gaps is preferably 15 or less. More specifically, it is preferable that the number of continuous gaps from one end to the other end in a 50 mm square area arbitrarily extracted from the fiber reinforced resin sheet is 15 or less. When the number of gaps is 15 or less, it is possible to more reliably obtain a fiber-reinforced resin sheet that contributes to improving the quality of molded products. Further, the lower limit of the number of gaps is not particularly limited, and the smaller the number of gaps, the more reliably a fiber-reinforced resin sheet that contributes to improving the quality of the molded product can be obtained. The number of gaps is more preferably 10 or less, and even more preferably 7 or less.

Furthermore, in the fiber-reinforced resin sheet of this embodiment, the maximum width of the gaps is preferably 1 mm or less. More specifically, it is preferable that the maximum width of the gaps that are continuous from one end to the other end in a 50 mm square area arbitrarily extracted from the fiber reinforced resin sheet is 1 mm or less. . With such a configuration, it is possible to more reliably obtain a fiber-reinforced resin sheet that has fewer gaps and contributes to improving the quality of molded products. The maximum width of the gap is preferably 0.5 mm or less, more preferably 0.3 mm or less.

In the fiber-reinforced resin sheet of this embodiment, it is preferable that the volume content Vf of carbon fibers to the fiber-reinforced resin sheet is 30% or more and 70% or less. By having the volume content Vf within the above range, when the fiber reinforced resin sheet is molded so that the thickness of the sheet is within a predetermined range, there are fewer gaps and the fiber reinforced resin sheet contributes to improving the quality of the molded product. It is thought that it is possible to obtain it more reliably.

The volume content Vf of the carbon fibers is more preferably 35% or more, and still more preferably 40% or more. Further, the volume content Vf of the carbon fibers is more preferably 65% or less, still more preferably 60% or less.

(Method for manufacturing fiber reinforced resin sheet)
Next, a method of manufacturing the fiber-reinforced resin sheet 1 of this embodiment will be described, but the method of manufacturing the fiber-reinforced resin sheet of this embodiment is not limited to the manufacturing method illustrated below. As described above, the fiber-reinforced resin sheet 1 of the present embodiment includes a sheet in which spread carbon fibers 3 are laminated on both sides of a resin film 2, and a sheet in which spread carbon fibers 3 are laminated on one side of the resin film 2. There may be various types of sheets, such as, but first, one method of manufacturing a sheet in which carbon fibers 3 are laminated on both sides of a resin film 2 will be described.

One method for producing a sheet in which carbon fibers 3 are laminated on both sides of a resin film 2 is to spread the fiber bundle 3' of carbon fibers into a band shape by opening them at a spreading ratio of 25% to 40%. An example of this method is to laminate the opened carbon fibers 3 on both sides of the resin film 2 while oriented in the same direction. This manufacturing method will be specifically explained below with reference to FIG. 2.

FIG. 2 is a diagram showing a schematic configuration of an apparatus for manufacturing the fiber-reinforced resin sheet 1. As shown in FIG. The fiber reinforced resin sheet 1 can be manufactured using, for example, a sheet manufacturing apparatus 50 shown in FIG. 2. This sheet manufacturing apparatus 50 is an apparatus that continuously manufactures a fiber reinforced resin sheet 1 from a fiber bundle 3' which is a bundle of carbon fibers and a thermoplastic resin film 2.

Specifically, the sheet manufacturing apparatus 50 includes a plurality of pairs (here, two pairs) of heating rollers 51 arranged vertically, and a plurality of pairs (here, two pairs) of cooling rollers 52 arranged vertically below the heating roller 51. , a pair of endless belts 54 stretched between a heating roller 51 and a cooling roller 52, a pair of pull-out rollers 55 located below the endless belt 54, and a winding disposed below the pull-out rollers 55. It is provided with a bobbin 56 for taking.

A spreading mechanism (not shown) is provided on both sides of the heating roller 51 at the uppermost stage to spread the fiber bundle 3' into a band shape. This opening mechanism is capable of forming a large number of continuous carbon fibers 3 spread in a thin band shape by continuously opening the fiber bundle 3'. The opening mechanism may be any mechanism that can perform such processing, such as a mechanism that spreads the fiber bundle by hitting it, a mechanism that spreads the fiber bundle by blowing air on it, a mechanism that spreads it by applying ultrasonic waves to the fiber bundle, etc. The following mechanism can be used.

In the example of FIG. 2, the opening mechanism includes a mechanism that supplies the spread carbon fibers 3 to one surface of the resin film 2, and a mechanism that supplies the spread carbon fibers 3 to the other surface of the resin film 2. It has a mechanism to The former mechanism is provided to introduce the carbon fibers 3 between one surface of the resin film 2 and a heating roller 51 in contact with the surface. The latter mechanism is provided to introduce the carbon fibers 3 between the other surface of the resin film 2 and the heating roller 51 in contact with the surface.

In the opening mechanism, the opening rate when opening the fiber bundle 3' into a plurality of carbon fibers 3 is preferably 25% or more, more preferably 30% or more, and 32%. It is more preferable that it is above. Further, the opening ratio is preferably 40% or less, more preferably 38% or less. When the opening ratio is 25% or more, there is an advantage that the sheet thickness does not become too thick and a fiber-reinforced resin sheet with excellent processability can be obtained. When the fiber opening ratio is 40% or less, there is an advantage that voids are less likely to occur. Therefore, by setting the fiber opening ratio to 25% or more and 40% or less, even if different fiber bundles are used, the fiber-reinforced resin sheet is thin, has few gaps, and contributes to improving the quality of molded products. can be obtained more reliably.

In addition, in this specification, "spreading ratio" is defined as the opening ratio of 100% (theoretical value) when the fibers of the fiber bundle are arranged in parallel so that they do not overlap one by one, and the actual opening width is the theoretical value. It can be calculated by calculating what percentage it corresponds to.

Next, the resin film 2 and the carbon fibers 3 introduced on both sides thereof are sandwiched and heated by the heating roller 51 from both sides via the endless belt 54, thereby continuously impregnating the carbon fibers 3 into the resin film 2. . Then, the resin film 2 impregnated with the carbon fibers 3 is cooled by the cooling roller 52 while being sandwiched from both sides via the endless belt 54, thereby fixing the carbon fibers 3 to the resin film 2. As a result, a fiber-reinforced resin sheet 1 in which carbon fibers 3 are laminated on both sides of the resin film 2 is formed.

By sequentially winding up the fiber-reinforced resin sheet 1 pulled out by the pull-out roller 55 using the winding bobbin 56, the fiber-reinforced resin sheet 1 can be gathered into a roll shape.

Next, a method for manufacturing a sheet in which carbon fibers 3 are laminated on one side of resin film 2 will be described. As a method for manufacturing a sheet in which carbon fibers 3 are laminated on one side of a resin film 2, a fiber bundle 3' of carbon fibers is opened at a spreading ratio of 20% to 30% and spread into a band shape. An example of this method is to laminate the opened carbon fibers 3 on one side of the resin film 2 while oriented in the same direction.

More specifically, in the fiber opening mechanism in the above manufacturing method shown in FIG. fiber-reinforced resin sheets can be manufactured. In the opening mechanism, the opening rate when opening the fiber bundle 3' into a plurality of carbon fibers 3 is not particularly limited, but is preferably 20% or more, and preferably 22% or more. is more preferable. Further, the opening ratio is preferably 30% or less, more preferably 28% or less. When the opening ratio is 20% or more, there is an advantage that the sheet thickness does not become too thick and a fiber-reinforced resin sheet with excellent processability can be obtained. When the opening ratio is 30% or less, there is an advantage that voids are less likely to occur. Therefore, by setting the fiber opening ratio to 20% or more and 30% or less, even if different fiber bundles are used, the fiber-reinforced resin sheet is thin, has few gaps, and contributes to improving the quality of molded products. can be obtained more reliably.

Next, a method for manufacturing a sheet of a type in which a plurality of carbon fibers are sandwiched between two or more resin films (hereinafter referred to as a multilayer resin type) will be described. Specifically, here, as the multilayer resin type sheet, a first resin film, a first carbon fiber after opening, a second carbon fiber after opening, and a second resin film are arranged in the thickness direction. An example of a type of fiber-reinforced resin sheet laminated in this order is shown below. Such a sheet can be manufactured, for example, by the following method.

First, a fiber bundle of first carbon fibers is opened at a spreading ratio of 20% to 55% and spread out into a band shape, and the first carbon fibers after the opening are oriented in the same direction. A first basic sheet is formed by laminating on one side of a resin film. Furthermore, the fiber bundle of the second carbon fibers is opened at a spreading ratio of 20% to 55%, spread out into a band shape, and the second carbon fibers are oriented in the same direction. A second basic sheet is formed by laminating on one side of the resin film. The first carbon fiber after opening and the second carbon fiber after opening are sandwiched between the first resin film and the second resin film. The first basic sheet and the second basic sheet are laminated. By such a method, the first resin film, the first carbon fiber after opening, the second carbon fiber after opening, and the second resin film are laminated in this order in the thickness direction. It is possible to manufacture fiber-reinforced resin sheets of this type.

More specifically, the method for forming the first basic sheet and the second basic sheet basically involves forming a sheet of the type described above in which the carbon fibers 3 are laminated on one side of the resin film 2. The same method as the manufacturing method can be used. In this case, the opening ratio of the carbon fibers (the first carbon fibers or the second carbon fibers) contained in the first basic sheet and the second basic sheet should be 20% or more. is preferable, and more preferably 25% or more. Further, the opening ratio is preferably 55% or less, more preferably 40% or less. When the opening ratio is 20% or more, there is an advantage that the sheet thickness does not become too thick and a fiber-reinforced resin sheet with excellent processability can be obtained. Furthermore, when the fiber opening ratio is 55% or less, there is an advantage that voids are less likely to occur in the fiber-reinforced resin sheet.

The method of laminating the first basic sheet and the second basic sheet includes laminating the first resin film and the second resin film, which overlap each other so as to sandwich the first carbon fiber and the second carbon fiber therebetween. Any method may be used as long as it can bond the two resin films to each other, and various methods may be used as long as they can be bonded to each other. As an example, the first basic sheet and the second basic sheet may be arranged such that the first carbon fiber and the second carbon fiber are sandwiched between the first resin film and the second resin film. A possible method is to heat both basic sheets while pressing them in the thickness direction with the sheets stacked one on top of the other.

Note that the multilayer resin type sheet can also be manufactured, for example, by the following continuous molding process. That is, the opened first carbon fibers and second carbon fibers supplied from the pair of fiber supply rollers are placed between the first resin film and the second resin film supplied from the pair of resin supply rollers. This is a method in which heat and pressure are applied using a heating roller or the like in this state. Also by such a method, a plurality of carbon fibers can be laminated between two resin films, and the multilayer resin type sheet can be manufactured.

(Application)
Regarding the fiber-reinforced resin sheet in this embodiment, as described later, a plurality of fiber-reinforced resin sheets may be laminated in the thickness direction and used as a laminate, or the fiber-reinforced resin sheet may be used as a laminate with a short side length of 2 mm or more and 20 mm. Hereinafter, it may be chopped into rectangular pieces with lengths of both sides of 10 mm or more and 40 mm or less and used as a fiber-reinforced resin chopped material. Alternatively, a laminate may be formed by laminating a plurality of chopped materials in the thickness direction with the fiber direction of the carbon fibers in an arbitrary direction.

Further, by performing press molding, tape winding molding, etc. using the fiber reinforced resin sheet of this embodiment, a molded product of any shape that can be manufactured can be manufactured. Examples of the molded products include those for general industrial use, automobiles, aircraft, temporary civil engineering materials, electrical and electronic equipment, toys, home appliances, and sporting goods.

<Laminated body>
The laminate according to the present embodiment includes a plurality of fiber-reinforced resin sheets according to the above-described embodiments, and the fiber directions of the carbon fibers are in the same direction or have angular differences from each other in plan view. are laminated in the thickness direction. With such a configuration, it is possible to obtain a laminate that has few gaps and contributes to improving the quality of molded products.

Here, in this specification, "fiber-reinforced resin sheets are laminated" means that a plurality of fiber-reinforced resin sheets are overlapped and fixed in the thickness direction. In this case, the fiber-reinforced resin sheet may be fixed to the other fiber-reinforced resin sheet by an appropriate method such as fusion, compression, or adhesion.

The specific meaning of such "lamination" changes depending on the physical property values and shape of the fiber-reinforced resin sheet, the type of treatment performed for lamination, the conditions thereof, etc. That is, during "lamination", heating, cooling, pressure treatment, etc. may be performed as necessary.

The laminate in this embodiment will be specifically described with reference to FIG. 3. As shown in FIG. 3, the fiber-reinforced resin sheet 1 in the above-described embodiment is cut and a plurality of base sheets 1A having a predetermined shape and size are laminated in the thickness direction, so that the thickness of the fiber reinforced resin sheet 1 is about several mm (for example, 2 mm). It is possible to form a plate-shaped laminate 10 having a thickness of .

At this time, in the example of FIG. 3, the plurality of base sheets 1A are laminated in the thickness direction in a state where the fiber directions X of the carbon fibers 3 have an angular difference from each other in plan view. More specifically, FIG. 3 shows an example in which a plurality of rectangular base sheets 1A are stacked such that the angles of the fiber direction X are shifted by 45 degrees in plan view. That is, the plurality of base sheets 1A to be laminated include a first base sheet 1Aa with an angle of 0° in the fiber direction X, a second base sheet 1Ab with an angle of 45° in the fiber direction It includes a third base sheet 1Ac whose angle in the direction X is 90 degrees and a fourth base sheet 1Ad whose angle in the fiber direction X is 135 degrees. Alternatively, without being limited to the example of FIG. 3, a plurality of base sheets 1A may be laminated in the thickness direction in a state in which the fiber directions X of the carbon fibers 3 are random in plan view (pseudo isotropic). .

Note that, regardless of the example of FIG. 3, the plurality of base sheets 1A are arranged in a state in which the fiber directions X of the carbon fibers 3 are in the same direction (that is, the fiber directions may be laminated in the thickness direction.

(Application)
A molded article of any shape that can be manufactured using the laminate in this embodiment can be manufactured. Examples of molded products include those for general industrial use, automobiles, aircraft, temporary civil engineering materials, electrical and electronic equipment, toys, home appliances, and sporting goods.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the scope of the present invention is not limited thereto.

[Examples 1 to 7, Comparative Examples 1 to 2]
The example described here is a fiber-reinforced resin sheet 1 manufactured using the sheet manufacturing apparatus 50 shown in FIG. 2 under the following manufacturing conditions.

(manufacturing conditions)
Film material: Nylon 9T (PA9T)
Film forming conditions: Extrusion molding at a forming temperature of 290 to 310°C Roll temperature: 280°C
Feed line speed: 20m/min
Lamination pattern: double-sided or single-sided Here, the film material and film molding conditions refer to the material and molding conditions of the resin film 2. The roll temperature refers to the temperature of the heating roller 51 in the sheet manufacturing apparatus 50. The feed line speed is the speed at which the carbon fibers 3 are fed to the resin film 2 in the sheet manufacturing apparatus 50. The lamination pattern indicates whether the carbon fibers 3 are laminated on one side or both sides of the resin film 2.

In this example, one of the following materials 1 and 2 was used as the carbon fiber 3.

(carbon fiber material)
Material 1: Carbon fiber with a fiber diameter of 7 μm, 12,000 fibers, and a fineness of 800 tex Material 2: Carbon fiber with a fiber diameter of 7 μm, 15,000 fibers, and a fineness of 1,000 tex Using the carbon fiber 3 made of either Material 1 or 2 above, Fiber-reinforced resin sheets of Examples 1 to 7 and Comparative Examples 1 to 2 shown in Table 1 were obtained under the above-mentioned manufacturing conditions. In addition, in order to easily compare each sheet, the volume content (Vf) in Examples 1 to 7 and Comparative Examples 1 to 2 was set to 50%, and the film was adjusted so that the volume content (Vf) was 50%. Adjusted the thickness.

Table 1 shows the parameters of opening ratio, Vf (volume content), film thickness, and sheet thickness for Examples 1 to 7 and Comparative Examples 1 to 2. In addition, the opening rate is what percentage of the theoretical value the actual opening width corresponds to, assuming that the opening rate is 100% (theoretical value) when the fibers of the fiber bundle are arranged in parallel so that they do not overlap one by one. This is what I calculated. In the carbon fiber materials used in this example, the spread widths at a spreading rate of 100% (theoretical value) are 84 mm for material 1 and 105 mm for material 2, respectively. Vf is the volume content (%) of the carbon fibers 3 in the fiber-reinforced resin sheet 1, and Vf was measured by a combustion method. The film thickness refers to the thickness (μm) of the resin film 2, and the sheet thickness refers to the actual value of the thickness (μm) of the fiber-reinforced resin sheet 1. The film thickness and sheet thickness were measured using a micrometer manufactured by Mitutoyo Co., Ltd.

Next, the number and maximum width of gaps, regular transmittance at a wavelength of 550 nm, and aperture ratio in the fiber-reinforced resin sheets of Examples 1 to 7 and Comparative Examples 1 to 2 were measured using the following methods. The results are shown in Table 1.

(gap)
The fiber-reinforced resin sheet was cut into a 50 mm square piece at an arbitrary position to prepare a test piece. The test piece was held up to a fluorescent lamp, and the number of continuous gaps from one end of the test piece to the other end was visually confirmed, and the width of the gap was also measured to confirm the maximum width.

(regular transmittance)
The fiber-reinforced resin sheet was placed in parallel and close contact with the opening of the integrating sphere so that all the rays that passed through the fiber-reinforced resin sheet were received by the integrating sphere, and a spectrophotometer (JASCO Corporation) was used to measure the regular transmittance at a wavelength of 550 nm. The measurement was carried out using a commercially available product, V-570).

(Aperture ratio)
The area ratio of the portion where the carbon fibers are not present in the fiber reinforced resin sheet was calculated by the following method.

A fiber-reinforced resin sheet was photographed with a digital camera, and the ratio of the number of pixels of the portion where no carbon fibers exist and the number of pixels per 1 cm ² of the photographed fiber-reinforced resin sheet was arbitrarily extracted using the PC software Adobe Photoshop ( The aperture ratio was calculated by a method of displaying a histogram using CS2 (registered trademark).

(Consideration)
As can be seen from Table 1, it includes a thermoplastic resin film and a plurality of continuous carbon fibers oriented in the same direction, and has a regular transmittance of light at a wavelength of 550 nm of 1% or less, and When the fiber-reinforced resin sheet had a thickness of 90 μm or less (Examples 1 to 7), the layer was thin and had few gaps.

On the other hand, the fiber-reinforced resin sheet of Comparative Example 1 with an opening rate of 46% had the same lamination pattern (both sides) and the same fibers (Material 1) as Comparative Example 1, but had a different opening rate. There were more gaps than in Example 1 (spreading ratio 36%), Example 2 (spreading ratio 30%), and Example 3 (spreading ratio 25%). Similarly, the fiber reinforced resin sheet of Comparative Example 2 with a fiber opening ratio of 48% has the same lamination pattern (both sides) and the same fibers (Material 2) as those of Comparative Example 2, but has a different opening ratio. (spreading ratio: 35%), Example 5 (spreading ratio: 30%), and Example 6 (spreading ratio: 25%). This is considered to be because in Comparative Example 1 and Comparative Example 2, the fiber opening ratio exceeded 40%, so gaps were likely to occur.

From this, in a sheet with a double-sided lamination pattern, by setting the fiber opening ratio to about 25 to 40%, even if the fiber bundles (materials 1 and 2) are different, the layers are thin and there are few gaps. It can be seen that the sheet can be obtained more reliably.

On the other hand, when comparing Example 7, in which the lamination pattern is on one side, and Examples 1 to 3, in which the lamination pattern is on both sides, it is found that both the fiber reinforced resin sheets of Examples 1 to 3 and 7 are thin layers and It has both characteristics, such as having few gaps. However, when comparing Example 7 in which the same fiber bundle (Material 1) was used and the lamination pattern was on one side and Example 3 in which the lamination pattern was on both sides, the opening ratios were almost the same, but The sheet thickness and specular transmittance values differ greatly. This is thought to be because the range of suitable fiber opening ratios differs depending on the lamination pattern. Specifically, as mentioned above, it is preferable that the opening rate of a sheet with a laminated pattern on both sides is about 25 to 40%, while the opening rate of a sheet with a laminated pattern on one side is about 20%. It is considered preferable to set it to about 30%.

Next, examples of multilayer resin type sheets in which a plurality of carbon fibers are laminated between two resin films will be described as Examples 8 and 9.

[Example 8]
First, using the sheet manufacturing apparatus 50 shown in FIG. 2, a basic sheet A in which carbon fibers 3 were laminated on one side of a resin film 2 was created. The manufacturing conditions of the sheet manufacturing apparatus 50 were the same as those of Examples 1 to 7 and Comparative Examples 1 to 2 with respect to film material, film forming conditions, roll temperature, and feed line speed. Further, as the carbon fiber 3, the same material 1 as that used in Examples 1 to 3 and 7 and Comparative Example 1 was used. Further, the opening rate of the opening mechanism in the sheet manufacturing apparatus 50 was set to 26%. Note that the thickness of the resin film 2 used at this time was 20 μm.

Prepare two basic sheets A, overlap both basic sheets A so that the carbon fibers 3 in both basic sheets A are sandwiched between the two resin films 2, and pressurize the overlapped basic sheets A. and heating. As a result, a fiber-reinforced resin sheet (multilayer resin type sheet) having a sheet thickness of 84 μm was obtained.

[Example 9]
First, using the sheet manufacturing apparatus 50 shown in FIG. 2, a basic sheet B in which carbon fibers 3 were laminated on one side of a resin film 2 was created. The manufacturing conditions of the sheet manufacturing apparatus 50 were the same as those of Examples 1 to 7 and Comparative Examples 1 to 2 with respect to film material, film forming conditions, roll temperature, and feed line speed. Further, as the carbon fiber 3, Material 1 was used in the same manner as that used in Examples 1 to 3 and 7 and Comparative Example 1. Further, the opening rate of the opening mechanism in the sheet manufacturing apparatus 50 was set to 40%. Note that the thickness of the resin film 2 used at this time was 30 μm.

Two of these sheets B are prepared, and the two basic sheets B are overlapped so that the carbon fibers 3 in both basic sheets B are sandwiched between the two resin films 2, and both the overlapped basic sheets B are pressurized and Heating was applied. As a result, a fiber-reinforced resin sheet (multilayer resin type sheet) having a sheet thickness of 90 μm was obtained.

Regarding the Vf (volume content), film thickness, sheet thickness, number of gaps, maximum width, regular transmittance at a wavelength of 550 nm, and aperture ratio of the fiber reinforced resin sheets in Examples 8 and 9, Examples 1 to 7 and comparison Table 2 shows the results measured using the same measuring method as in Examples 1 and 2.

(Consideration)
As can be seen from Table 2, the fiber-reinforced resin sheets of Examples 8 and 9, which were created by overlapping basic sheets with a lamination pattern on one side, were composed of a thermoplastic resin film and a plurality of continuous fibers oriented in the same direction. It contained carbon fibers, had a regular transmittance of light at a wavelength of 550 nm of 1% or less, had a thickness of 90 μm or less, was a thin layer, and had few gaps.

This application is based on Japanese Patent Application No. 2022-119521 filed on July 27, 2022, and the contents thereof are included in the present application.

In order to express the present invention, the present invention has been appropriately and fully explained through the embodiments above with reference to specific examples, drawings, etc., but those skilled in the art will be able to modify and/or improve the above-described embodiments. It should be recognized that this can be done easily. Therefore, unless the modification or improvement carried out by a person skilled in the art does not leave the scope of the claims stated in the claims, such modifications or improvements do not fall outside the scope of the claims. It is interpreted as encompassing.

1 Fiber-reinforced resin sheet 2 Resin film 3 Carbon fiber 3' Fiber bundle 10 Laminated body

Claims (8)

Including a thermoplastic resin film and a plurality of continuous carbon fibers oriented in the same direction,
The regular transmittance of light at a wavelength of 550 nm is 1% or less, and
A fiber reinforced resin sheet having a thickness of 90 μm or less. The fiber-reinforced resin sheet according to claim 1, wherein the aperture ratio, which is the area ratio of the portion where the carbon fibers do not exist in the fiber-reinforced resin sheet, is 10% or less. The fiber-reinforced resin sheet according to claim 1, wherein the number of continuous gaps from one end to the other end in a 50 mm square area arbitrarily extracted from the fiber-reinforced resin sheet is 15 or less. The fiber reinforced resin sheet according to claim 3, wherein the maximum width of the gap is 1 mm or less. A fiber bundle of carbon fibers is opened at an opening rate of 25% to 40% and spread into a band shape,
The method for producing a fiber-reinforced resin sheet according to any one of claims 1 to 4, wherein the opened carbon fibers are laminated on both sides of a resin film while being oriented in the same direction. A fiber bundle of carbon fibers is opened at an opening rate of 20% to 30% and spread into a band shape,
The method for producing a fiber-reinforced resin sheet according to any one of claims 1 to 4, wherein the opened carbon fibers are laminated on one side of a resin film while being oriented in the same direction. Spreading a first carbon fiber bundle and a second carbon fiber bundle at an opening rate of 20% or more and 55% or less into a band shape,
Claim: The first carbon fiber after opening and the second carbon fiber after opening are laminated between a first resin film and a second resin film in a state where they are oriented in the same direction. 5. The method for producing a fiber-reinforced resin sheet according to any one of 1 to 4. comprising a plurality of fiber reinforced resin sheets according to any one of claims 1 to 4,
The plurality of fiber-reinforced resin sheets are stacked in the thickness direction so that the fiber directions of the carbon fibers are in the same direction or have angular differences from each other in plan view.