JP7574042B2 - Manufacturing method of glass paper prepreg and fiber reinforced plastic - Google Patents

Description

The present invention relates to a method for producing glass paper prepregs and fiber-reinforced plastics .

The effect of fiber breakage on the mechanical properties of surface coatings on fiber reinforced plastics (FRP) is explained below using a pressure vessel.

Traditionally, there is reverse osmosis (RO) as a technology for desalinating seawater, and ultrafiltration (UF) as a technology for making groundwater sterile for drinking or medical use.

In both methods, water treatment is carried out by applying water pressure to a membrane; the reverse osmosis membrane method requires a pressure vessel with an operating pressure of 2 to 8 MPa, while the ultrafiltration membrane method requires a pressure vessel with an operating pressure of 0.2 to 0.9 MPa. In either case, to ensure that the pressure vessel will not be destroyed by the water pressure during water treatment operation, for example, for a pressure vessel with an operating pressure of 8 MPa, a pressure vessel that will not be destroyed even at 48 MPa, which has a safety factor of six times the operating pressure, is used.

However, since thermoplastic resins such as polypropylene resin do not have sufficient pressure resistance as materials for these pressure vessels, fiber reinforced plastics (FRP), which is a composite of glass fiber or carbon fiber and epoxy resin, are used.

For example, to improve the aesthetic appearance of a water treatment plant, the surface of the FRP pressure vessel after molding is painted in a light color such as white or light blue to match the image of water treatment, and a transparent top coat is applied as a protective layer on top of the design paint. In addition, in order to make the most of the unfinished surface design (crossing fiber pattern) of the FRP molded product, a transparent top coat is applied directly to the surface of the FRP molded product without a design paint. Various other processes are applied to the surface of the FRP molded product, but there is a demand to make the surface processing of the FRP molded product easier than it is now. In particular, when the FRP base material is a woven carbon fiber cloth (carbon cloth), a transparent top coat is often applied to make the most of the crossing fiber pattern.

These FRP pressure vessels are cylindrical in shape, and are manufactured using two methods: the filament winding method, in which fibers are impregnated with epoxy resin, crossed, and wound around a mandrel that serves as a core metal, and then heated and cured; and the sheet winding method, in which a woven fabric is first impregnated with epoxy resin to create a semi-cured prepreg, which is then wound like a sushi roll around a mandrel that serves as a core metal, and then heated and cured.

The filament winding method allows for the appropriate combination of two fiber orientations, fiber bundles in a helical (spiral) direction of ±40 to 60 degrees and fiber bundles in a hoop (rotation) direction of ±85 to 89 degrees with the long axis of the mandrel in the 0 degree direction, and the layer thicknesses thereof, and is therefore widely used for a wide range of applications, from low-pressure vessels in the ultrafiltration membrane process to high-pressure vessels in the reverse osmosis membrane process.

On the other hand, in the sheet winding method, the long axis of the mandrel is in the 0 degree direction, the fibers in the width direction of the woven fabric are in the 0 degree direction of the pressure vessel, and the fibers in the length direction of the woven fabric are in the 90 degree direction. In the FRP molded product made by this sheet winding method, the width of the woven fabric is the length of the pressure vessel (for example, 1250 mm). In this sheet winding method, the woven fabric is the fiber base material, so the fiber orientation is 0 degrees in the length direction of the pressure vessel and 90 degrees in the circumferential direction. Furthermore, the pressure vessel made by this sheet winding method is cylindrical with an equal thickness over its entire length, and the parts that abut against the lids at both openings cannot be made thick like a clay pipe, so from the standpoint of pressure resistance, it is not suitable for pressure vessels for high-pressure reverse osmosis membrane methods and is used for pressure vessels for low-pressure ultrafiltration membrane methods.

When the thermosetting resin 31 used in the manufacture of FRP, such as epoxy resin, is heated and hardened, a 10-30 μm inactive layer 31' is formed on the surface of the FRP molded product X, which is unsuitable for bonding to other materials or painting. This inactive layer 31' becomes an obstacle when carrying out subsequent design processing (design painting or topcoat painting) (because paint does not adhere well to the surface of the FRP molded product X), so if other materials are to be bonded to the surface of the hardened resin 31, it is necessary to remove the inactive layer 31' by surface cutting processing such as sanding or sandblasting (see Figures 6 and 7).

In addition, with the filament winding method, the fibers are dense where the helical fibers overlap (for example, the intersection of fibers at +50° and -50°), and the fibers are sparse in the gaps between one intersection and the next. On the other hand, with the sheet winding method, the fibers are dense where the warp and weft threads of the woven fabric intersect, and the fibers are sparse in the gaps between one intersection and the next. Therefore, with both the filament winding method and the sheet winding method, the surface of the FRP molded product is convex in the areas where the fibers overlap, and concave in the gaps between the overlapping fibers and the adjacent overlapping fibers.

In particular, the sheet winding method produces a tubular FRP molded product X by winding, for example, carbon cloth prepreg 30 around a mandrel in a sushi roll shape, and the inner and outer layers of this sushi roll are bonded together by hardening with resin 31 that wells up from the semi-hardened prepreg due to the heating and pressure of a heated roll adjacent to the mandrel. However, because the resin 31 that wells up from the prepreg due to the heating and pressure of the heated roll is a viscous syrup-like substance that does not flow easily, concave depressions tend to form in areas where the fibers 32 become coarse. Because the warp and weft threads of carbon cloth are regularly arranged, the surface of the FRP molded product X formed by the sheet winding method has checkerboard-like depressions 33 where the open spaces between the warp and weft threads are regularly recessed.

The depth of the recesses 33 of the checkerboard pattern is 50 to 60 μm from the surface of the FRP molded product X, and can be as deep as 70 to 80 μm, or 80 μm or more depending on the molding conditions of the sheet winding method (for example, when rotating at high temperature and high speed to shorten working time) or when the resin 31 of the carbon cloth prepreg 30 does not flow easily. As with the inactive layer 31' described above, paint does not adhere well to the surface of the FRP molded product X with these recesses 33, so it is necessary to perform surface cutting processing such as sanding or sandblasting on the surface of the FRP molded product X until the recesses 33 disappear.

However, when the recesses 33 are deep, such as 80 μm, and the surface of the FRP molded product X is subjected to surface cutting processing such as sanding or sandblasting until the recesses 33 disappear in order to obtain a good paint base, the fibers 32 near the surface layer are cut, reducing the strength and elasticity of the FRP molded product X. In the case of an FRP pressure vessel, if surface cutting processing such as sanding or blasting that cuts the fibers 32 is performed, problems such as cracks appearing in the pressure vessel during water treatment operation will occur, causing water leakage, making it impossible to maintain the internal pressure inside the pressure vessel, reducing the water production efficiency, and in some cases causing the pressure vessel to burst and be unable to produce water using the water treatment equipment.

However, if the surface cutting process such as sanding or sandblasting is limited to a level that does not cut the fibers 32 of the FRP molded product X, depressions 33 will remain on the surface of the FRP molded product X. Therefore, for example, in order to paint a design, these depressions 33 must be eliminated.

Conventionally, before applying a design to the surface of this FRP molded product X, the surface of the FRP molded product X is degreased by surface cutting such as sanding or sandblasting to the extent that the fibers 32 are not cut (see Figure 7), the recesses 33 are filled with a polyester resin-based putty 34, and the areas filled with this putty 34 are again surface cut to flatten the surface of the FRP molded product X (see Figure 8), and a design is applied to the surface of the FRP molded product X after the unevenness adjustment.

Here, we will explain in detail the conventional surface treatment (conventional example) of FRP molded product X (cylindrical (curved surface of a cylinder) carbon cloth FRP: CFRP, 1000 mm wide and 1500 mm long), from preparing the surface base to applying a design (design painting and top coat painting).

First, prepare the carbon cloth prepreg 30 cut into a rectangle with a width of 1000 mm and a length of 1500 mm.

This carbon cloth prepreg 30 is a cloth (woven fabric) prepreg made of 3,000 carbon fiber filaments, with 3,000 carbon fiber filaments, warp threads 32 and weft threads 32 both having a weave density of 12.5 threads/25 mm and a basis weight of 198 to 200 g/ ^m2 , and is a prepreg made of resin 31 (epoxy resin) that has the property of being heat-cured at 130 to 150°C for 1 hour.

Eight sheets of this carbon cloth prepreg 30 are stacked and set into a cylindrical lower mold, the upper mold is fitted, and the mixture is heated and compressed at a temperature of 150°C and a pressure of 3 MPa. Heating and pressure are maintained for 60 minutes, and slow cooling is started after 60 minutes. 90 minutes after heating and compressing, the mold is opened to obtain FRP molded product X.

Because this FRP molded product X uses carbon cloth, as mentioned above, its surface has regular checkerboard-like depressions 33 that follow the crossing pattern of the fibers (see Figure 6).

Therefore, if a design is applied to the surface of this FRP molded product X (by painting the design and applying a top coat), the process will proceed as follows. Figure 9 shows a cross section of the conventional coating.

First, the surface of the FRP molded product X is cut (sanded or sandblasted) to a depth that does not cut the fibers 32, and then a degreasing process is performed (Step 1, see Figure 7).

Next, the recesses 33 remaining on the surface of the FRP molded product X even after the surface cutting process are filled with putty 34 (for example, a black polyester resin-based putty). This putty 34 is cured according to the recommended curing conditions (temperature, time) for the putty 34 used. For example, it is cured with hot air at 40 to 60°C for 3 to 6 hours or at room temperature for one day, and after curing, the convex parts on the surface of the FRP molded product X are sanded with, for example, #240 sandpaper, and unevenness is adjusted so that the surface to be painted with the design is roughly flat without any extreme protrusions (Step 2, see Figure 8). Note that when curing the putty 34 and drying and curing the paint in this step 2, if the temperature is set to, for example, 80°C or higher, the drying and curing time will be shorter, but microcracks will occur in the putty 34 and paint, and peeling will occur from the surface of the FRP molded product X, so it is desirable to cure the putty 34 and dry and harden the paint at a low temperature, for example, 60°C or lower. If the temperature is lowered, the drying and curing time will be longer.

Next, a clear paint that will form the undercoat layer 41 is applied to the surface of the FRP molded product X after unevenness adjustment with a spray gun to a thickness of 25 to 30 μm, and the paint is dried and hardened, for example, at 40°C for half a day to a day (step 3).

This undercoat layer 41 is formed to a thickness of 25 to 30 μm for the purpose of obtaining adhesion to the base material of the surface of the FRP molded product X after unevenness adjustment, and corrosion resistance to alkali and acid of the surface of the FRP molded product X. At the same time, it obtains adhesion to the intermediate coat layer 42 described below.

Next, the clear paint that will form the intermediate coat layer 42 is applied to the surface of the undercoat layer 41 with a spray gun to a thickness of 40 to 45 μm, and the paint is dried and hardened, for example, at 40°C for half a day to a day (step 4).

The intermediate coat layer 42 is formed to a thickness of 40 to 45 μm in order to maintain the smoothness of the undercoat layer 41 and to obtain impact resistance for the entire coating. At the same time, it ensures adhesion to the topcoat layer 44, which will be described later. If design painting (or design printing) is to be performed, it is applied on top of the intermediate coat layer 42. The intermediate coat layer 42 also serves the purpose of forming a smooth base for design painting or design printing.

Next, if pearlescent paint is used as the design paint, it is applied to the surface of the intermediate coat layer 42 after the intermediate coat layer 42 has been formed, to a thickness of 15 to 20 μm. This design paint layer (design layer 43) is also dried and hardened, like the other layers, for example, at 40°C for half a day to a day (step 5).

In addition to painting designs, brand names and designs may also be silk-screened or stickers may be affixed to add designs.

Next, the clear paint that will form the topcoat layer 44 is applied to the surface of the design layer 43 with a spray gun to a thickness of 40 to 45 μm, and the paint is dried and hardened, for example, at 40°C for half a day to a day (step 6).

In addition, in step 6, as shown in Figure 10, a top coat layer 44 may be formed on the surface of the intermediate coat layer 42 without forming a design layer 43. In this case, a transparent top coat is directly applied to the surface of the FRP molded product X without applying a design paint, in order to make use of the raw surface design (crossing fiber pattern) of the FRP molded product X.

If necessary, a clear coating that will form a second topcoat layer (not shown) is applied to the surface of topcoat layer 44 with a spray gun to a thickness of 40 to 45 μm, and the coating is then dried and hardened, for example, at 40°C for half a day to a day (step 7).

This topcoat layer 44 is the topcoat coating mentioned above, and is formed to a thickness of 40 to 90 μm for the purposes of maintaining gloss, improving aesthetics, scratch resistance, weather resistance, and stain resistance.

As described above, the surface of the FRP molded product X is painted through the above steps, and there is a demand to simplify this surface painting process, which involves many steps.

The present invention has been made in view of the above-mentioned conventional demands, and provides a novel and extremely practical method for producing glass paper prepregs and fiber-reinforced plastics , which allows surface treatment to be performed on the surface of an FRP molded product without the need for unevenness adjustment.

The gist of the present invention will be explained with reference to the attached drawings.

A glass paper prepreg for forming a fiber reinforced plastic by layering on a unidirectional glass prepreg or a unidirectional carbon prepreg, or a glass cloth prepreg or a carbon cloth prepreg 30 and heating and pressing the same , the glass paper prepreg 1 being formed by impregnating glass paper 2 with resin 3, the content of the resin 3 being 60 wt % or more, and the resin flow calculated from the following formula 1 being set to 40% or more.
Resin flow (%) = amount of resin 3 flowing out after pressing (g) / weight of prepreg before pressing (g) ... Equation 1

The present invention also relates to a glass paper prepreg, characterized in that in the glass paper prepreg described in claim 1, the resin impregnated in the glass unidirectional prepreg or the carbon unidirectional prepreg, or the glass cloth prepreg or the carbon cloth prepreg 30, and the resin 3 impregnated in the glass paper prepreg 1 are both thermosetting resins.

The present invention also relates to a glass paper prepreg, characterized in that in the glass paper prepreg described in claim 1 , the resin 3 impregnated into the glass paper prepreg 1 is a resin 3 made by mixing a thermoplastic resin and a thermosetting resin in a compounding ratio (mass percentage ratio) of 15:85 to 35:65.

The glass paper prepreg according to claim 3 is characterized in that phenoxy resin is used as the thermoplastic resin and urethane acrylate resin is used as the thermosetting resin.

The present invention relates to a glass paper prepreg according to any one of claims 1 to 4, characterized in that the resin 3 is continuously coated by a coating machine, and the tensile strength of the glass paper 2 is 15 N/15 mm or more in one direction and 4 N/15 mm or more in another direction perpendicular to the one direction.

The present invention also relates to a method for producing fiber-reinforced plastic, in which the glass paper 2 pulled out from the wound state is passed through a resin impregnation tank section 12 containing resin 3 to impregnate it with the resin 3, and then the resin-impregnated glass paper 2 that has passed through the resin impregnation tank section 12 is passed through a heating section 13 to semi-cure the resin 3, and the glass paper prepreg 1 having a resin 3 content of 60 wt % or more and a resin flow calculated from the following formula 1 of 40% or more is laminated on a glass unidirectional prepreg or carbon unidirectional prepreg, or a glass cloth prepreg or carbon cloth prepreg 30 , and heated and pressurized to form a fiber-reinforced plastic.
Resin flow (%) = amount of resin 3 flowing out after pressing (g) / weight of prepreg before pressing (g) ... Equation 1

In addition, in the method for producing fiber-reinforced plastics described in claim 6, the resin impregnated into the unidirectional glass prepreg or the unidirectional carbon prepreg, or the glass cloth prepreg or the carbon cloth prepreg 30, and the resin 3 impregnated into the glass paper prepreg 1 are both thermosetting resins.

The present invention also relates to a method for producing fiber-reinforced plastics , characterized in that the resin 3 impregnated into the glass paper prepreg 1 is a mixture of a thermoplastic resin and a thermosetting resin in a compounding ratio (mass % ratio) of 15:85 to 35:65.

The present invention also relates to a method for producing fiber-reinforced plastics , characterized in that a phenoxy resin is used as the thermoplastic resin and a urethane acrylate resin is used as the thermosetting resin, in the method for producing fiber-reinforced plastics described in claim 8.

The present invention relates to a method for producing fiber-reinforced plastics as described in any one of claims 6 to 9 , characterized in that the tensile strength of the glass paper 2 is 15 N/15 mm or more in one direction and 4 N/15 mm or more in another direction perpendicular to the one direction.

Since the present invention is configured as described above, it is possible to perform surface treatment on the surface of an FRP molded product without adjusting the unevenness of the surface, thereby providing a novel and extremely practical method for producing glass paper prepregs and fiber-reinforced plastics .

FIG. 2 is a perspective view showing a glass paper prepreg and a carbon cloth prepreg according to Example 1. FIG. 2 is an explanatory diagram illustrating the production of the glass paper prepreg according to Example 1. 1 is a table showing measurement results confirming the performance of Example 1 and Comparative Example. 2 is a cross-sectional view illustrating a surface-treated portion of the FRP molded product A according to Example 1. FIG. A cross-sectional view explaining the refraction state of light at the surface-treated portion of the FRP molded product A according to Example 2. 1 is a cross-sectional view illustrating an FRP molded product X molded by a conventional manufacturing method. 1 is a cross-sectional view illustrating an FRP molded product X molded by a conventional manufacturing method. 1 is a cross-sectional view illustrating an FRP molded product X molded by a conventional manufacturing method. 1 is a cross-sectional view illustrating a surface-treated portion of an FRP molded product X molded by a conventional method. 1 is a cross-sectional view illustrating the refraction of light at a surface-treated portion of an FRP molded product X molded by a conventional method.

The preferred embodiment of the present invention will be briefly explained below, showing the operation of the invention based on the drawings.

When a sheet of glass paper prepreg 1 according to the present invention is laminated on top of a unidirectional glass prepreg or a unidirectional carbon prepreg, or a glass cloth prepreg or a carbon cloth prepreg 30, and a fiber-reinforced plastic (FRP molded product A) is molded, a layer having a flat surface without any recesses is formed on the surface of this FRP molded product A.

The glass paper 2 used in the present invention contains a large amount of resin 3, and the viscosity of the resin 3 decreases when heated and pressurized during molding, and there is an appropriate resin flow that allows the resin 3 to completely cover the recesses in the FRP molded product A. After the resin 3 flows, its viscosity increases and it hardens in a state where it has completely covered the recesses, forming a layer with a flat surface without any recesses.

For example, the glass paper 2 has a tensile strength of 15 N/15 mm or more in one direction and 4 N/15 mm or more in the other direction perpendicular to the one direction, so that the glass paper 2 can be continuously coated with the resin 3 without breaking during the coating process. Furthermore, when the glass paper 2 is impregnated with the resin 3 to form a glass paper prepreg, the resin content and resin flow are set to the optimum level stably and continuously.

Therefore, without the need for conventional unevenness adjustment on the surface of the FRP molded product A obtained by the present invention, it is possible to paint a design on the flat layer formed on the surface of this FRP molded product A, and then paint this design-painted surface with a transparent top coat as a protective layer. In other words, the layer formed on the surface of this FRP molded product A when it is molded serves as an ideal base for applying designs such as painting or printing.

The layer formed on the surface of this FRP molded product A is a clear, colorless, transparent layer, because the glass paper 2 becomes transparent by being impregnated with the resin 3.

In other words, the unfinished surface design (cross-pattern of fibers) of FRP molded product A can be seen through this transparent layer.

Therefore, this transparent layer itself functions as a protective layer, and there is no need to apply multiple layers to form a protective layer as in the past.

A specific embodiment 1 of the present invention will be described with reference to the drawings.

As shown in FIG. 1, this embodiment is a glass paper prepreg 1 for forming a fiber-reinforced plastic (FRP molded product A/FRP pressure vessel) by laminating it on a unidirectional glass prepreg or a unidirectional carbon prepreg, or a glass cloth prepreg or a carbon cloth prepreg 30. As shown in FIG. 4, this FRP molded product A has a two-phase layer structure consisting of a layer A1 made of a carbon cloth prepreg 30 and a layer A2 (a fiber base material layer in the form of a nonwoven fabric with anisotropic fiber orientation) made of glass paper prepreg 1 provided on top of this layer A1.

The carbon cloth prepreg 30 used in this embodiment is a cloth (woven fabric) prepreg made of 3,000 carbon fiber filaments, as in the conventional case described above, and is a carbon cloth with 3,000 carbon fiber filaments, warp threads 32 and weft threads 32 both having a weave density of 12.5 threads/25 mm and a basis weight of 198 to 200 g/ ^m2. This prepreg is made of epoxy resin 31 that has the property of being heat-cured at 130 to 150°C for 1 hour.

In this embodiment, an FRP pressure vessel is used as the FRP molded product A, but any other product that exhibits the characteristics of this embodiment can be used as appropriate.

The glass sheet prepreg 1 according to this embodiment is described below.

This glass sheet prepreg 1 is made by coating glass paper 2 with resin 3, and in this embodiment, a vertical coating machine is used for coating the prepreg.

As shown in Figure 2, this vertical coating machine is provided with a glass paper delivery section 10 that delivers the glass paper 2 in a rolled state before prepreg processing, and a glass paper prepreg winding section 11 that winds up the prepreg-processed glass paper prepreg 1. Between these sections are a resin impregnation tank section 12 that impregnates the glass paper 2 with resin 3, and a heating section 13 (semi-curing zone) through which the resin-impregnated glass paper 2 that has passed through the resin impregnation tank section 12 passes vertically up and down to heat and semi-cure the resin 3 impregnated in the glass paper 2. Reference numeral 14 denotes a tension roller.

In this embodiment, a roll of glass paper 2 having a unit weight of 25 g/ ^m2 , a width of 1,040 mm and a length of 100 m is set in the glass paper delivery section 10. The glass paper 2 is then passed through a resin impregnation tank section 12 to be impregnated with resin 3. The resin-impregnated glass paper 2 that has passed through the resin impregnation tank section 12 is then passed through a heating section 13 to semi-cure the resin 3 to form a glass paper prepreg 1. The glass paper prepreg 1 is then wound up in a glass paper prepreg winding section 11 for continuous prepreg coating.

In addition, in this embodiment, the glass paper 2 used has a tensile strength of 15 N/15 mm in the length direction (vertical direction) and 4 N/15 mm in the width direction (horizontal direction), and is anisotropic in that the strength is higher in the length direction than in the width direction.

In this embodiment, the resin impregnation tank 12 contains resin 3, which is a mixture (mass %) of phenoxy resin as a thermoplastic resin and urethane acrylate resin as a thermosetting resin disclosed in Japanese Patent Application No. 2018-37390, in a ratio of 15:85, or a resin containing 100% urethane acrylate resin. In addition, an epoxy resin that hardens at 130 to 150°C for 1 hour, similar to the resin 31 used in the carbon cloth prepreg 30 described above, such as an epoxy resin made of an epibis liquid epoxy as a base agent and dicyandiamide as a hardener, may also be used.

In addition, a method for impregnating the glass paper 2 with the resin 3 is preferably an impregnation method in which the entire glass paper 2 is immersed in the resin impregnation tank 12 (called a dipping method), as in this embodiment.

In other words, in addition to the dipping method, there is also an impregnation method (called the hot melt method) in which heated and molten resin is pressed into one side of the fiber base material using the pressure of a roll or press plate, and the temperature and pressure of the press molding process or autoclave molding process that is the next process for the prepreg are used to fully impregnate the fiber base material. However, in order to achieve the effect of eliminating the need for unevenness adjustment for the paint base, the dipping method, in which the resin is fully impregnated at the prepreg coating stage, is preferable.

In this embodiment, the heating temperature of the prepreg heating section 13 of the vertical coater is set to 150°C, but the temperature of the heating section 13 and the coating speed are appropriately determined according to the length and heating capacity of the heating section 13 and the gel time of the resin so that the obtained prepreg is at the desired semi-cured level. For example, the temperature of the heating section 13 can be increased from 150°C to 180°C, and the coating speed can be increased while keeping an eye on the residence time in the heating section 13, the gel time of the resin 3, and the semi-cured state of the resin 3 impregnated in the prepreg after passing through the heating section 13. In this embodiment, a vertical coater in which the path of the heating section 13 is vertical is described, but a horizontal coater in which the heating section 13 is horizontal may also be used for prepreg coating.

The inventors also tried to coat the prepreg with glass paper 2 having a tensile strength of 15 N/15 mm or less in the length direction (vertical direction) and 4 N/15 mm or less in the width direction (horizontal direction), but the forward tension and back tension during the prepreg coating caused the glass paper to tear in the length direction and width direction, making continuous coating impossible.

Therefore, it is desirable that the tensile strength of the glass paper 2 used in this prepreg coating (continuous coating of resin 3 by a coating machine) is 15 N/15 mm or more in the length direction (vertical direction) and 4 N/15 mm or more in the width direction (horizontal direction) (resulting in anisotropy). Also, in this continuous coating, the tensile strength of the glass paper 2 may be 15 N/15 mm in the length direction (vertical direction) and 15 N/15 mm in the width direction (horizontal direction) (resulting in isotropy).

By the way, the resin 3 impregnated and coated on the glass paper prepreg 1 reaches a semi-cured state, and this semi-cured state is determined by the resin flow of the prepreg.

Specifically, the obtained prepreg is cut to a set size (e.g., 200 mm square), and the entire prepreg is press molded in a press molding machine at a set temperature and pressure (e.g., a temperature of 150°C and a pressure of 0.3 MPa, which are sufficient to cure the resin blend), and the degree of semi-curing is determined by the amount of resin that flows after molding. With this method of determination, the glass paper 2, whose fibers are intricately intertwined in the base material, does not flow with the resin and remains there.

If the resin is close to being cured, it will not flow easily, and if it is close to being uncured, it will flow easily, so the state of semi-curing can be measured by the way the resin spreads out (resin flow).

The degree of semi-curing is determined by the weight of the resin that has flowed out and the weight of the prepreg before it flowed out, and the percentage calculated using the following formula is called the resin flow.

Resin flow FL (%) = amount of resin flowing out by pressing: F (g) / weight of prepreg before pressing: W (g) ... Equation 1
Amount of resin flowing out after pressing: F (g) = Weight of prepreg before pressing W1 (g) - Weight of FRP plate after resin flowing out after pressing W2 (g) ... Equation 2
The resin flow is calculated by substituting F of Equation 2 into Equation 1.

In this embodiment, various prototypes were made by varying the prepreg coating conditions of the vertical coater (e.g., coating speed, viscosity of resin 3, temperature setting of heating section 13, etc.) to obtain glass paper prepreg 1 with a resin content of 80 wt% and a resin flow of 50%, and one sheet of this glass paper prepreg 1 with a resin content of 80 wt% and a resin flow of 50% was prepared with a width of 1000 mm and a length of 1500 mm.

On the other hand, eight sheets of the carbon cloth prepreg 30 (a prepreg made of carbon cloth with 3000 carbon fiber filaments, warp and weft threads both having a weave density of 12.5 threads/25 mm and a basis weight of 198 to 200 g/ ^m2 , and epoxy resin that hardens at 130 to 150°C for 1 hour) with a resin content of 35 wt% described above are prepared, each sheet having a width of 1000 mm and a length of 1500 mm.

Eight sheets of this carbon cloth prepreg 30 were laminated, and one sheet of glass paper prepreg 1 was laminated on top of the eight sheets of carbon cloth prepreg 30. This laminate was set in a cylindrical lower mold 1000 mm wide and 1500 mm long, and the upper mold was fitted. It was then heated and pressed at a temperature of 150°C and a pressure of 3 MPa. Heating and pressure application were maintained for 60 minutes, and slow cooling was started after 60 minutes. 90 minutes after heating and pressing, the mold was opened to provide FRP molded product A.

This FRP molded product A had a smooth surface without any checkerboard-like depressions and was a cylindrical molded product with a thickness of 1.9 to 1.95 mm.

When the cross section of this FRP molded product A was observed under a microscope, it was found that layer A1 made of carbon cloth prepreg 30 and layer A2 made of glass paper prepreg 1 placed on top of layer A1 were integrated and well bonded, with layer A1 made of carbon cloth prepreg 30 being 1.72 to 1.8 mm thick and layer A2 made of glass paper prepreg 1 being 0.15 to 0.18 mm thick.

Next, the surface of this cylindrical FRP molded product A (surface of layer A2) was sandblasted to a depth of 40-60 μm in order to remove the inactive layer specific to FRP and to impart the design for the next process.

In this example, sandblasting was performed because the molded surface was cylindrical, but sanding can also be used if the FRP molded product A is flat or cylindrical, as long as a sanding machine that can follow the shape is available.

After sandblasting, there were no recesses on the surface of FRP molded product A, and when the cross section of FRP molded product A after sandblasting was examined under a microscope, layer A2 of the surface glass paper prepreg 1 remained, and there were no areas where the carbon fibers of layer A1 of carbon cloth prepreg 30 had been cut.

Therefore, the surface of the FRP molded product A after sandblasting can be subjected to the process of forming the undercoat layer 41 in step 3 or the design layer 43 in step 5 without any need for surface preparation. The adhesion of the undercoat layer 41 was excellent, scoring 10 points in the cross-cut test according to JIS K5600.

Here, as an example, one laminate of eight carbon cloth prepregs 30 was laminated with one glass paper prepreg 1 on top of the other and pressed to form a flat plate, and the surface layer (surface layer on the glass paper prepreg side) of the plate was sandblasted. As a comparative example, the surface layer of a flat plate was press molded with only eight carbon cloth prepregs 30 and sandblasted until all recesses disappeared. The bending strength and bending modulus of elasticity of both plates were measured with the sandblasted surface facing up according to the test method of JIS K7074, and the values are as shown in the table in Figure 3.

In the comparative example, when sandblasting was performed until all the recesses were removed, a 19.5% decrease in bending strength and an 8.3% decrease in bending modulus were observed.

In addition, in the comparative example, it was visible to the naked eye that the carbon fibers on the surface had partially broken, whereas in this example, even though sandblasting was performed to a depth of 40 to 60 μm, layer A2 of the surface glass paper prepreg 1 remained and the carbon fibers were not cut, so it is believed that there was no decrease in the strength and elastic modulus of the FRP molded product A.

In addition, in this embodiment, one sheet of glass paper prepreg 1 is laminated, but if the storage life of the carbon cloth prepreg 30 is approaching and the resin flow of the carbon cloth prepreg 30 is lower than when it was fresh, two sheets of glass paper prepreg 1 may be laminated.

Specifically, when there is one sheet (one layer) of glass paper 2, it is desirable for the resin content of the glass paper prepreg 1 to be 70 wt% or more and for the resin flow to be 40% or more.

In the inventors' experiments, when a glass paper prepreg 1 had a resin content of 70 wt% or less and a resin flow of 40% or less, and there was only one sheet of glass paper 2, checkerboard-shaped depressions sometimes appeared in parts of the surface of the FRP molded product A.

Furthermore, when there are two sheets (two layers) of glass paper 2, the resin content of the glass paper prepreg 1 does not need to be 70 wt% or more, and it has been confirmed that it is better to make the resin content 60 wt% or more and to laminate two sheets with a resin flow of 40% or more.

In addition, when there are three or more sheets (three layers) of glass paper 2, it is advisable to laminate three or more sheets of glass paper prepreg 1 with a resin content of 60 wt% or more and a resin flow rate of 40% or more, just as in the case when there are two sheets (two layers) of glass paper 2.

In the present embodiment, the carbon cloth prepreg 30 uses a prepreg of cloth (woven fabric) made of 3,000 carbon fiber filaments. For example, if a cloth (woven fabric) made of 12,000 carbon fiber filaments is used for the carbon cloth prepreg 30, the carbon fibers will be thicker than those of 3,000 filaments, and the fibers will be dense at the intersections of the warp and weft threads of the woven fabric, and the fibers will be coarser in the gaps between one intersection and the next. Therefore, in order to eliminate recesses on the surface of the FRP molded product A after sandblasting, to leave layer A2 of the surface glass paper prepreg 1, and to avoid cutting the carbon fibers, it is sufficient to use multiple sheets of glass paper 2 (multi-layers).

In this embodiment, as shown in FIG. 4, the FRP molded product A has a layer A2 made of glass paper prepreg 1 as a base, on whose surface the design paint layer (design layer 43) described above in step 5 is formed, and furthermore, the topcoat layer 44 described above in step 6 is formed on the surface of this design layer 43. In addition to the design paint, for example, a brand name or design may be silk-screened or a sticker may be attached to impart a design.

Therefore, steps 1 to 4 are not required for the FRP molded product A produced using this embodiment.

Since this embodiment is configured as described above, it is possible to easily perform surface processing of the FRP molded product A, such as by directly applying design paint or printing to the surface of the FRP molded product A without adjusting the surface unevenness.

In Example 1, the case of press molding using an upper and lower mold was explained, but in autoclave molding using only an upper mold or only a lower mold, it is also possible to easily perform surface processing of the FRP molded product A, such as directly applying design paint or printing without adjusting for unevenness.

In Example 1, carbon cloth prepreg 30 was used for the explanation, but glass cloth prepreg, glass unidirectional prepreg, or carbon unidirectional prepreg can also be used to easily perform surface processing of the FRP molded product A, such as directly applying design paint or design printing without adjusting for unevenness.

A specific example 2 of the present invention will be described with reference to the drawings.

In this embodiment, as shown in Figure 5, no design layer or topcoat layer is formed on layer A2 made of glass paper prepreg 1, and layer A2 is used as a topcoat layer (protective layer) through which the unfinished surface design (cross-fiber pattern) of FRP molded product A can be seen. The other configurations are the same as in Example 1.

Conventionally, when the unfinished surface design (a design of crossed fibers) of FRP molded product A is to be made transparent and visible, after the molding process, as described above, a topcoat layer is formed on the surface through steps 1 to 7 (in this case step 5 is not performed).

In the process described above, there are cases where only the top coat is applied in two layers, but the undercoat and undercoat may also be applied twice, with each layer being thinner, to avoid microcracks and peeling from the lower layer caused by shrinkage during drying and hardening, so in reality, many processes and man-hours are required to complete the painting.

For example, if the thickness of the topcoat layer is 80 μm, trying to apply it in one coat can result in a discrepancy in the dryness state of the surface and the interior, with the surface being dry but the interior not dry, and the coating film being pulled towards the surface during drying, which can lead to cracks and fissures.

Depending on the drying conditions, the surface of the coating may become matte. Cracks, crevices, and matte surfaces in the coating will cause the coating to lose its transparency, and the cross-fiber pattern will no longer be clearly visible. Therefore, clear coating that allows the cross-fiber pattern to be seen is applied thinly once, then polished with #1000 paper to improve smoothness, and then dried and applied multiple times to create a thick coat. However, clear coating that allows the cross-fiber pattern to be seen is quite costly in terms of both materials and labor, including the drying time of the paint, and the number of days required, drying equipment, painting, and management of drying conditions.

Conventionally, in order for the cross-fiber pattern to be visible through the paint, the undercoat, intermediate coat, and top coat all need to be transparent. Also, for example, if the paint dries too quickly and a hardened film (interface film) is formed at the interface between the undercoat and intermediate coat, or between the intermediate coat and topcoat, birefringence or double reflection can occur at that interface (for example, the interface between the topcoat and intermediate coat), as shown in Figure 10, causing the cross-fiber pattern to become blurred or appear as a double image.

In particular, the surface of the above-mentioned topcoat layer 44 must be smooth enough that the reflection of the fluorescent light can be seen as a straight tubular fluorescent light. In steps 6 and 7, which form this topcoat layer 44, care must be taken with how it is applied and dried so that the tubular reflection of the fluorescent light does not appear jagged.

In addition, when the painted surface of an FRP molded product has a U-shaped cross section and is both horizontal and vertical, the paint film tends to be thick on horizontal surfaces and easily sagging on vertical surfaces, so consideration must be given to the horizontal and vertical surfaces when painting. If this is to be formed with a clear coat, there will be double refraction and double reflection at the paint interface in the dry state, so even more consideration must be given to the drying area and drying conditions.

In this respect, according to this embodiment, the surface layer (the transparent layer obtained by the glass paper prepreg) through which the cross-fiber pattern is transparently visible is a single layer, so there is no birefringence or double reflection at the interface (for example, the interface between the top coat and the undercoat, such as in painting), and the cross-fiber pattern does not become blurred or appear as a double image.

Furthermore, because this protective layer is formed using the mirror surface of the upper mold, it is smooth enough that the reflection of the fluorescent light can be seen as a straight tubular fluorescent light. There is no need to pay attention to how the paint is applied or how it dries, as in steps 6 and 7, where the clear coat is applied as described above, to prevent the tubular reflection of the fluorescent light from appearing jagged.

In addition, even if the painted surface of an FRP molded product has a horizontal and vertical surface, such as a U-shaped cross section, a transparent layer is obtained using glass paper prepreg by molding using a mold, so there is no need to worry about the paint film becoming thicker on horizontal surfaces or the paint film easily sagging on vertical surfaces, as occurs with painting (see Figure 5).

The surface layer (the transparent layer A2 obtained from the glass paper prepreg 1, called the top coat layer) through which the crossed fiber pattern can be seen transparently can be obtained by omitting all of the steps 1 to 7 described above.

As mentioned above, there is also a big difference between Example 2 and the conventional example in the number of days required for the process and the attention paid to each process to make the carbon cloth mesh stand out transparently.

That is, in Example 2, a transparent topcoat layer is obtained at the same time as molding FRP molded product A. When FRP is molded in a mold, the resin of the glass paper prepreg and the resin of the carbon cloth prepreg that form the topcoat layer are both thermosetting resins, and when heated, the resins flow out in liquid form and become compatible with each other and harden, resulting in good adhesion at the interface between the carbon cloth FRP layer and the glass paper FRP layer.

In addition, as explained in the resin flow determination method, glass paper 2, whose base material fibers are intricately intertwined, has the characteristic that the fibers do not flow with the resin but remain there. Therefore, when the glass fibers of glass paper 2 come into contact with the carbon fibers of the carbon cloth, the carbon fibers are held down by the glass fibers of glass paper 2, and the carbon fibers are not washed away by the flow of resin in the carbon cloth prepreg. Therefore, the mesh of the carbon cloth does not become misaligned, and the warp and weft threads are kept neatly perpendicular to each other.

In addition, the outermost layer, which requires careful painting, is a transfer of the mold surface in this embodiment, so there is no need to be careful about how it is painted, dried, or finished, in order to prevent the tubular reflection of the fluorescent light from becoming jagged, as occurs when painting. Also, in this embodiment, the topcoat layer is a single layer of a single material, prepreg made of glass paper, so there is no double refraction or double reflection that occurs with clear coating.

In the conventional example, after the molding of FRP molded product X, the process proceeds while paying careful attention to the coating thickness, drying, and hardening, and a transparent topcoat layer is finally obtained through surface preparation (flattening), undercoating, intermediate coating, and top coating. There are significant differences between the examples of this application and the conventional example in terms of process (e.g., the number of days required) and quality control (e.g., painting work to improve the surface condition of the coating and management of paint drying conditions).

This example was explained using the cross pattern of carbon fibers in FRP molded product A using carbon cloth prepreg 1, but a transparent topcoat layer can also be applied to FRP molded products using glass cloth prepreg, allowing the cross pattern of glass fibers to stand out transparently.

Furthermore, a transparent topcoat layer can be similarly applied to FRP molded products made from unidirectional glass prepregs or unidirectional carbon prepregs, allowing the unidirectional and crossing fiber patterns to stand out transparently.

In addition, the transparent topcoat layer made of glass paper prepreg 1 in this embodiment is hardened by the combination of resin and hardener, and is not made by drying out the organic solvent contained in paint, so a surface layer with excellent chemical resistance and scratch resistance can be obtained.

In this embodiment, as in the first embodiment, one sheet of glass paper prepreg 1 is laminated, but if the storage life of the carbon cloth prepreg 30 is approaching and the resin flow of the carbon cloth prepreg 30 is lower than when it was fresh, two sheets of glass paper prepreg 1 may be laminated.

Specifically, when there is one sheet (one layer) of glass paper 2, it is desirable for the resin content of the glass paper prepreg 1 to be 70 wt% or more and for the resin flow to be 40% or more.

In the inventors' experiments, when a glass paper prepreg 1 had a resin content of 70 wt% or less and a resin flow of 40% or less, and when there was only one sheet of glass paper 2, checkerboard-like depressions were formed in parts of the surface of the FRP molded product A, causing the tubular reflection of the fluorescent lamp to appear jagged.

Furthermore, when there are two sheets (two layers) of glass paper 2, it has been confirmed that it is best to laminate two sheets of glass paper prepreg 1 with a resin content of 60 wt% or more and a resin flow of 40% or more.

When there are three or more sheets (three layers) of glass paper 2, it is advisable to laminate three or more sheets of glass paper prepreg 1 with a resin content of 60 wt% or more and a resin flow rate of 40% or more, just as in the case of two sheets (two layers) of glass paper 2. This will result in a smooth topcoat layer that will not cause jagged reflections in the tubular shape of the fluorescent lamp.

In the present embodiment, the carbon cloth prepreg 30 is a prepreg of a cloth (woven fabric) made of 3,000 carbon fiber filaments. If, for example, a cloth (woven fabric) made of 12,000 carbon fiber filaments is used for the carbon cloth prepreg 30, the carbon fibers will be thicker than those of the 3,000 filament type, and the fibers will be dense at the intersections of the warp and weft threads of the woven fabric, and the fibers will be coarser in the gaps between one intersection and the next. Therefore, in order to obtain a smooth topcoat layer without checkerboard-like recesses on the surface of the FRP molded product A and without jagged tubular reflections of fluorescent lamps, it is sufficient to use multiple sheets of glass paper 2 (multi-layers).

Since this embodiment is configured as described above, the unfinished surface design (crossing fiber pattern) of FRP molded product A can be seen through the transparent layer formed when FRP molded product A is molded, and this layer functions as a protective layer, eliminating the need to apply multiple layers to form a protective layer as in the past, and making it easy to process the surface of FRP molded product A.

Since Example 2 has the same configuration as Example 1, the explanation has been given for the case of press molding using an upper and lower mold, but the same can be said for autoclave molding using only an upper mold or only a lower mold. The unfinished surface design (crossing pattern of fibers) of FRP molded product A can be seen through the transparent layer formed when FRP molded product A is molded, and this layer functions as a protective layer, making it unnecessary to apply multiple layers to form a protective layer as in the past, and thus simplifying the surface processing of FRP molded product A.

Since Example 2 has the same structure as Example 1, it has been explained using carbon cloth prepreg 30, but the same can be said for glass cloth prepreg, glass unidirectional prepreg, or carbon unidirectional prepreg. Through the transparent layer formed when FRP molded product A is molded, the raw surface design of the FRP molded product A (the cross pattern of fibers in one direction in the case of a cross prepreg) can be seen, and this layer functions as a protective layer, so there is no need to apply multiple layers to form a protective layer as in the past, and the surface processing of FRP molded product A can be easily performed.

1 Glass paper prepreg 2 Glass paper 3 Resin
12 Resin impregnation tank
13 Heating section
30 Carbon cloth prepreg

Claims (10)

A glass paper prepreg for forming a fiber reinforced plastic by layering on a unidirectional glass prepreg or a unidirectional carbon prepreg, or a glass cloth prepreg or a carbon cloth prepreg 30 and heating and pressing the same, the glass paper prepreg being made by impregnating glass paper with a resin, the resin content being 60 wt % or more, and the resin flow calculated from the following formula 1 being set to 40% or more.
Resin flow (%) = amount of resin 3 flowing out after pressing (g) / weight of prepreg before pressing (g) ... Equation 1 2. The glass paper prepreg according to claim 1, wherein the resin impregnated in the unidirectional glass prepreg or the unidirectional carbon prepreg, or the glass cloth prepreg or the carbon cloth prepreg, and the resin impregnated in the glass paper prepreg are both thermosetting resins. The glass paper prepreg according to claim 1 , characterized in that the resin impregnated into the glass paper prepreg is a resin obtained by mixing a thermoplastic resin and a thermosetting resin in a compounding ratio (mass % ratio) of 15:85 to 35:65. The glass paper prepreg according to claim 3, characterized in that phenoxy resin is used as the thermoplastic resin and urethane acrylate resin is used as the thermosetting resin. The glass paper prepreg according to any one of claims 1 to 4, characterized in that the resin is continuously coated by a coating machine, and the tensile strength of the glass paper is 15 N/15 mm or more in one direction and 4 N/15 mm or more in another direction perpendicular to the one direction. A method for producing fiber reinforced plastic, comprising the steps of: passing glass paper pulled out from a wound state through a resin impregnation tank section containing resin to impregnate the glass paper with the resin; subsequently, passing the resin-impregnated glass paper which has passed through the resin impregnation tank section through a heating section to semi-cure the resin; laminating this glass paper prepreg, in which the resin content is set to 60 wt % or more and the resin flow calculated from the following formula 1 is set to 40% or more, on top of a glass unidirectional prepreg or a carbon unidirectional prepreg, or a glass cloth prepreg or a carbon cloth prepreg , and heating and pressurizing the resulting fiber reinforced plastic.
Resin flow (%) = amount of resin 3 flowing out after pressing (g) / weight of prepreg before pressing (g) ... Equation 1 7. The method for producing fiber-reinforced plastics according to claim 6, wherein the resin impregnated in the unidirectional glass prepreg or the unidirectional carbon prepreg, or the glass cloth prepreg or the carbon cloth prepreg, and the resin impregnated in the glass paper prepreg are both thermosetting resins. The method for producing fiber-reinforced plastics according to claim 6 , wherein the resin impregnated into the glass paper prepreg is a resin obtained by mixing a thermoplastic resin and a thermosetting resin in a blending ratio (mass % ratio) of 15:85 to 35:65. 9. The method for producing fiber-reinforced plastics according to claim 8 , wherein a phenoxy resin is used as the thermoplastic resin, and a urethane acrylate resin is used as the thermosetting resin. The method for producing fiber-reinforced plastics according to any one of claims 6 to 9 , characterized in that the tensile strength of the glass paper is 15 N/15 mm or more in one direction and 4 N/15 mm or more in another direction perpendicular to the one direction.

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