JP7765320B2 - Method for producing the composite - Google Patents

Description

The present invention relates to a method for producing a composite.

A thin film of fiber-reinforced resin (hereinafter simply referred to as "Uni-Direction (UD) sheet") is known, which contains multiple reinforcing fibers oriented in one direction and a resin composition (matrix resin) impregnated into the reinforcing fibers. Because UD sheets are lightweight and strong, they are expected to be used in a variety of reinforcing materials.

When using UD sheets as a reinforcing material for resin material, insert molding can be used to obtain resin material reinforced by UD sheets, in which the resin that will form the resin material is injected into a mold with the UD sheet placed in it. However, during insert molding, there is a problem in that the UD sheet can become misaligned due to the flow of the injected resin. To prevent this misalignment, it is desirable to temporarily fix the UD sheet before injecting the resin. Patent Document 1 describes methods for temporary fixation, such as temporary fixation using a jig, temporary fixation using adhesive such as double-sided tape, and temporary fixation using suction with negative pressure.

JP 2015-193118 A

Patent Document 1 describes a method for temporarily fixing UD sheets using a jig, adhesive, and negative pressure.

However, when the UD sheet is temporarily fixed using a jig, the timing of removing the jig must be strictly controlled when the resin to be molded is introduced. Furthermore, if the UD sheet is temporarily fixed vertically or if the temporary fixing position of the UD sheet is curved, a complex movement mechanism is required to move the jig. Furthermore, temporary fixing using adhesive is not very strong, so it is unable to fully prevent the UD sheet from shifting position when the resin to be molded is introduced. Furthermore, when temporary fixing using negative pressure is used, for example, if the UD sheet has fine cracks, or if the temporarily fixed surface is curved and the UD sheet cannot deform to fit the curve, leaving gaps at the edges, the resin to be molded can seep into the suction mechanism through the cracks when the resin to be molded is introduced, requiring work to remove this resin.

As such, conventional methods for temporarily fixing UD sheets have had problems such as requiring complex equipment, not being able to fully prevent the UD sheet from shifting position, and molding resin getting inside the temporary fixing equipment. Similar problems have also arisen when manufacturing molded products by introducing molding resin into a mold containing reinforcing materials other than UD sheets, and when manufacturing fiber-reinforced resin by introducing matrix resin into a mold containing reinforcing fibers.

In light of these problems, the present invention aims to provide a method for manufacturing composites that achieves temporary fixation of reinforcing materials during insert molding using a simple device configuration that is also designed to prevent molding resin from penetrating the interior of the temporary fixation device.

In order to solve the above-mentioned problems, one aspect of the present invention relates to a method for manufacturing a composite, which includes the steps of: placing a reinforcing material inside a mold having two or more gates in a position that covers a first gate; introducing a first resin through the first gate to temporarily fix the reinforcing material; and introducing a second resin through a second gate different from the first gate to mold a composite of the temporarily fixed reinforcing material and the second resin.

The present invention provides a method for manufacturing a composite that achieves temporary fixation of reinforcing materials during insert molding using a simple device configuration that prevents molding resin from penetrating the interior of the temporary fixation device.

FIG. 1 is an exemplary flow chart of a method for producing a composite according to one embodiment of the present invention. FIG. 2A is a schematic diagram showing the general configuration of a mold used in this embodiment, and FIG. 2B is a cross-sectional view of the mold taken along the dashed line 2B-2B shown in FIG. 2A. 3A and 3B are a schematic view and a cross-sectional view similar to FIGS. 2A and 2B, showing the placement of a reinforcing material in a mold. FIG. 4 is a schematic diagram showing the state in which the mold is placed in the injection molding machine and the reinforcing material is temporarily held in place. FIG. 5 is a schematic diagram showing how the reinforcing material is temporarily fixed. FIG. 6 is a schematic diagram showing the state of the vicinity of the first gate (area A in FIG. 5) when the first nozzle is opened. FIG. 7 is a schematic diagram showing the vicinity of the first gate (region A in FIG. 5) in a modified example in which the shape of the first gate is changed. FIG. 8 is a schematic diagram showing the formation of a complex. 9A and 9B are schematic diagrams showing an embodiment in which the first resin and the second resin are different types of resin. 10A and 10B are schematic diagrams showing another embodiment in which the first resin and the second resin are different types of resin.

The present invention will now be described with reference to the drawings, which illustrate exemplary embodiments. Please note that the drawings may exaggerate key features or omit unnecessary elements, and may not accurately reflect the actual embodiment.

Figure 1 is an exemplary flowchart of a method for manufacturing a composite according to one embodiment of the present invention. The manufacturing method according to this embodiment includes the steps of placing a reinforcing material in a mold having two or more gates at a position that covers a first gate, introducing a first resin through the first gate to temporarily fix the reinforcing material, and introducing a second resin through a second gate different from the first gate to mold a composite of the temporarily fixed reinforcing material and the second resin.

In this specification, a composite refers to an article in which a reinforcing material and a resin are integrated, obtained by pouring a resin into a mold in which a reinforcing material has been placed and then solidifying the resin. The reinforcing material is preferably placed on the surface of the composite, but may also be placed inside the composite.

[First step: placement of reinforcing material]
In this process, a reinforcing material is placed within a mold having two or more gates in a position that covers the first gate.

Figure 2A is a schematic diagram showing the general configuration of the mold used in this embodiment, and Figure 2B is a cross-sectional view of the mold shown in Figure 2A taken along dashed line 2B-2B. As shown in Figures 2A and 2B, the mold 100 has a first gate 110 and a second gate 120. The first gate 110 and the second gate 120 are both through-holes that penetrate the mold 100 and open to the cavity surface 130, and act as gates for introducing molten resin from the injection device into the cavity surface 130 side of the mold 100.

The positions of the first gate 110 and the second gate 120 are not particularly limited. As described below, the first gate 110 is used to temporarily fix the reinforcing material by introducing a first resin, and the second gate 120 is used to produce a composite by introducing a second resin. Therefore, the first gate 110 is preferably provided at a position in the composite where the reinforcing material will be placed. The second gate 120 is preferably provided at a position that will not be covered by the reinforcing material when the reinforcing material is placed in a position that covers the first gate 110.

In this process, reinforcing material 200 is placed on the cavity surface 130 of the mold 100 in a position that covers the first gate 110. Figures 3A and 3B are schematic and cross-sectional views similar to Figures 2A and 2B, showing the reinforcing material 200 placed on the mold 100. The reinforcing material 200 is placed on a portion of the cavity surface 130 corresponding to the position in the composite produced in this embodiment where reinforcement with the reinforcing material is to be performed. The shape of the reinforcing material 200 is not particularly limited. In this embodiment, the reinforcing material 200 is a UD sheet.

At this time, it is preferable to temporarily hold down the reinforcing material 200 placed on the cavity surface 130. The temporary holding down can be any method that prevents the reinforcing material 200 from shifting position until the reinforcing material 200 is temporarily fixed in place in the next step. For example, the reinforcing material 200 can be held down against the cavity surface 130 using a jig such as a holding rod, or the reinforcing material 200 can be attached to the cavity surface 130 with an adhesive (including double-sided tape). Note that the introduction of the first resin in the next step does not involve flow of the resin in contact with the reinforcing material 200, so it is sufficient to temporarily hold down the reinforcing material with a force smaller than that used for temporary fixing in the next step. Therefore, temporary holding down using the jig or adhesive is sufficient.

In Figures 3A and 3B, the reinforcing material 200 is placed horizontally on the planar cavity surface 130. However, the surface on which the reinforcing material 200 is placed may not be flat, but may be curved. Furthermore, when using an injection molding machine in which the mold is placed vertically, the cavity surface 130 may not be horizontal when placed in the injection molding machine. When the cavity surface 130 of the mold 100 placed in the injection molding machine is not horizontal, the reinforcing material 200 placed on the cavity surface 130 is likely to become misaligned, so it is desirable to temporarily hold the reinforcing material 200.

Figure 4 is a schematic diagram showing the mold 100 placed in the injection molding device 400 and the reinforcing material 200 temporarily held in place.

The injection molding apparatus 400 is a vertical injection molding apparatus in which the mold 100 is arranged vertically, and the cavity surface 130 of the arranged mold 100 is non-horizontal (oriented vertically). The injection molding apparatus 400 also includes a kneading device 410 that melts, kneads, and extrudes resin, a manifold 420 formed with a flow path 422 through which the resin extruded from the kneading device 410 flows, a stationary platen 430 having a first nozzle 432 that introduces a first resin into the first gate 110 and a second nozzle 434 that injects a second resin into the second gate 120, and a first opening/closing mechanism 442 that opens and closes the first nozzle 432 and a second opening/closing mechanism 444 that opens and closes the second nozzle 434 (both valve gates in this embodiment). Note that the injection molding apparatus 400 has a movable core for forming the cavity, but since the cavity does not need to be formed at this stage, the movable core is not shown in Figure 4. Note that neither the first nozzle 432 nor the second nozzle 434 is open at this stage.

In FIG. 4, a pressure rod 450 serving as a jig is used to press the reinforcing material 200 against the cavity surface 130 (the first gate 110 side) from the side opposite the first gate 110, temporarily holding the reinforcing material 200. In this embodiment, the size of the surface of the pressure rod 450 pressing against the reinforcing material 200 is larger than the surface area of the surface of the reinforcing material 200 facing the cavity surface 130, allowing the entire reinforcing material 200 to be pressed against the cavity surface 130. However, the size of the pressure rod 450 is not limited to this and may be smaller. However, from the perspective of preventing leakage of the first resin from the end of the reinforcing material 200 in the next process, it is preferable that the size of the surface of the pressure rod 450 pressing against the reinforcing material 200 be larger than the size of the opening of the first gate 110. As mentioned above, the method of temporary holding is not limited to this.

The type of reinforcing material 200 is not particularly limited, and may be any reinforcing material, such as a resin member (including an oriented sheet), a fiber-reinforced resin, or a reinforcing fiber. The shape of the reinforcing material 200 is also not particularly limited, and may be any shape, such as a plate, a sheet, a thicker molded body, or a molded body with a complex shape. Furthermore, when the reinforcing material 200 is a reinforcing fiber, it may be either a long fiber or a short fiber, and these reinforcing fibers may be aligned or arranged randomly.

[Second step: temporary fixing of reinforcing material]
In this step, a first resin is introduced from the first gate of a mold in which a reinforcing material is placed in a position that covers the first gate, thereby temporarily fixing the reinforcing material 200 .

Figure 5 is a schematic diagram showing how the reinforcing material is temporarily fixed in place in this process. With the mold 100 in place and the reinforcing material 200 temporarily held down by the holding rod 450, the first nozzle 432 of the injection molding device 400 is opened and the first resin is allowed to flow from the first nozzle 432 into the first gate 110. In Figure 5, the valve pin that constitutes the valve gate, which is the first opening/closing mechanism 442, is retracted to open the first nozzle 432. Note that the second nozzle 434 does not open at this time.

Figure 6 is a schematic diagram showing the state near the first gate 110 (area A in Figure 5) when the first nozzle 432 is open. Note that for ease of understanding, the pressure rod 450 has been omitted from Figure 6. Also, since it is not necessary to form a cavity in this process yet, the movable core is not shown in Figure 6 either.

When the first nozzle 432 is opened, the molten first resin 600 flows into the first gate 110, passes through the inside of the first gate 110, and reaches the reinforcing material 200. The first resin 600 then comes into contact with the reinforcing material 200 from the first gate 110 side at the opening 110a.

At this time, the first resin 600 may be extruded from the kneading device 410 and a predetermined pressure applied to cause the first resin 600 to flow into the first gate 110. However, in this process, it is sufficient for the first resin 600 to move only within the relatively short first gate 110, and for a relatively small amount of the first resin 600 to come into contact with the reinforcing material 200 at the opening 110a. Therefore, the pressure applied to the first resin 600 does not need to be very large; for example, the first resin 600 may be caused to flow into the first gate 110 by the residual pressure within the flow path 422, without applying pressure from the kneading device 410. At this time, it is preferable to heat the mold 100 using a heating mechanism (not shown) of the injection molding device 400.

Then, the first nozzle 432 is closed to stop the introduction of the first resin 600, and if the mold 100 is being heated, the heating is also stopped, allowing the first resin 600 in contact with the reinforcing material 200 to cool and solidify. This allows the reinforcing material 200 to be temporarily fixed to the mold 100 by the solidified first resin 600.

Once the reinforcing material 200 has been temporarily fixed by the solidification of the first resin 600, the temporary clamping of the reinforcing material 200 performed in the previous process may be removed.

The above-mentioned temporary fixation temporarily fixes the reinforcing material 200 using the first resin 600 filled inside the first gate 110, and allows for temporary fixation of the reinforcing material 200 with greater force than temporary fixation using adhesives, etc. Furthermore, temporary fixation is performed on the cavity surface 130 side of the mold 100, and after the temporary holddown is removed, no jig is placed inside the cavity (the side opposite the first gate 110). This eliminates the need to remove the jig during injection molding of the second resin, and makes it possible to temporarily fix the reinforcing material 200 with a simple configuration. Furthermore, unlike temporary fixation using negative pressure, there is no risk of the resin entering the interior of the device.

Figure 7 is a schematic diagram showing the area near the first gate 110 (area A in Figure 5) in a modified example in which the shape of the first gate 110 has been changed.

The first gate 110 is typically tubular. Therefore, the area of the opening 110a of the first gate 110 is small, and the contact area between the reinforcing material 200 and the first resin 600 at the opening 110a is also small. In contrast, as shown in FIG. 7 , by making the opening 110a of the first gate 110 wider, the contact area between the reinforcing material 200 and the first resin 600 at the opening 110a can be increased, enabling the reinforcing material 200 to be temporarily fixed more firmly. In this case, the size of the wide opening 110a is preferably equal to or smaller than the surface area of the face of the reinforcing material 200 facing the cavity surface 130, from the perspective of suppressing a drop in pressure in the first resin 600 due to leakage from the end of the reinforcing material 200.

In this case, the cross-sectional shape of the first gate 110 may be such that only the opening 110a is wide, as shown in Figure 7, or the flow path width (cross-sectional area) of the first gate 110 may increase continuously or in stages toward the opening 110a.

The first resin 600 is not particularly limited as long as it is a thermoplastic resin.

Examples of the above thermoplastic resins include polycarbonate resin, styrene-based resin, polyamide resin, polyester resin, polyphenylene sulfide resin (PPS resin), modified polyphenylene ether resin (modified PPE resin), polyacetal resin (POM resin), liquid crystal polyester, polyarylate, acrylic resins including polymethyl methacrylate resin (PMMA), etc., polyolefins including vinyl chloride, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone (PEEK), polyethylene, polypropylene, polybutene, and poly4-methyl-1-pentene, etc., modified polyolefins which are modified products of these, and phenoxy resin. The polyolefin may be a copolymer including an ethylene/propylene copolymer, an ethylene/1-butene copolymer, an ethylene/propylene/diene copolymer, an ethylene/carbon monoxide/diene copolymer, an ethylene/ethyl (meth)acrylate copolymer, an ethylene/glycidyl (meth)acrylate copolymer, and an ethylene/vinyl acetate/glycidyl (meth)acrylate copolymer.

When the reinforcing material 200 is a material containing resin, such as a resin member or fiber-reinforced resin, it is preferable that the first resin 600 be compatible with the resin contained in the reinforcing material 200. In this specification, "compatible" means that a single phase is formed when both resins are heated and mixed above their melting points and cooled to 25°C. It is more preferable that both resins are the same. In this specification, "same" means that the monomer composition, weight-average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of both resins are the same within the measurement error range. If both resins are compatible, or even identical, they can be fused together, allowing the first resin 600 to temporarily fix the reinforcing material 200 more strongly.

[Third step: molding of composite]
In this step, a second resin is introduced from a second gate to form a composite of the temporarily fixed reinforcing material 200 and the second resin.

Figure 8 is a schematic diagram showing how a composite is formed in this process. A movable core 810 is positioned opposite the cavity surface 130 of the mold 100, and the mold 100 and movable core 810 form a sealed cavity 820. In this state, the second nozzle 434 of the injection molding device 400 is opened, and the second resin is injected from the second nozzle 434 through the second gate 120 into the cavity 820. In Figure 8, the valve pin that constitutes the valve gate, which is the second opening/closing mechanism 444, is retracted to open the second nozzle 434. Note that the first nozzle 432 does not open at this time.

At this time, the second resin 800 is extruded from the kneading device 410, and the molten second resin 800 is injected into the cavity 820 through the second gate 120 under a predetermined pressure. In the embodiment illustrated in FIG. 8, the first resin 600 and the second resin 800 are the same resin. The temperature, pressure, injection time, injection speed of the second resin 800, the heating temperature of the mold 100 and movable core 810, the pressure inside the cavity 820, etc. may be set appropriately depending on the type of second resin 800, the shape and size of the cavity 820, etc.

After the second resin 800 has sufficiently filled the cavity 820, the second nozzle 434 is closed to stop the introduction of the second resin 800, and the heating of the mold 100 and movable core 810 is also stopped, allowing the second resin 800 to cool and solidify. This allows a composite including the solidified second resin 800 and the reinforcing material 200 to be obtained.

In this case, the reinforcing material 200 may be used as a bulk object such as a resin member or fiber-reinforced resin to produce a composite (insert molded product) in which the second resin 800 and the reinforcing material 200 are bonded. Alternatively, the reinforcing material 200 may be used as reinforcing fibers to produce a composite (fiber-reinforced resin) in which the second resin 800 is impregnated into the reinforcing fibers.

In this embodiment, the reinforcing material 200 is temporarily fixed in place by the first resin 600 in the previous step, so even when the second resin 800 is injected in this step, the reinforcing material 200 is less likely to shift position.

The second resin 800 may be a thermoplastic resin or a thermosetting resin.

Examples of the above thermoplastic resins include polycarbonate resin, styrene-based resin, polyamide resin, polyester resin, polyphenylene sulfide resin (PPS resin), modified polyphenylene ether resin (modified PPE resin), polyacetal resin (POM resin), liquid crystal polyester, polyarylate, acrylic resins including polymethyl methacrylate resin (PMMA), etc., polyolefins including vinyl chloride, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone (PEEK), polyethylene, polypropylene, polybutene, and poly4-methyl-1-pentene, etc., modified polyolefins which are modified products of these, and phenoxy resin. The polyolefin may be a copolymer including an ethylene/propylene copolymer, an ethylene/1-butene copolymer, an ethylene/propylene/diene copolymer, an ethylene/carbon monoxide/diene copolymer, an ethylene/ethyl (meth)acrylate copolymer, an ethylene/glycidyl (meth)acrylate copolymer, and an ethylene/vinyl acetate/glycidyl (meth)acrylate copolymer.

Examples of the thermosetting resin include epoxy resin, phenolic resin, melamine resin, urea resin, diallyl phthalate resin, silicone resin, urethane resin, furan resin, ketone resin, xylene resin, thermosetting polyimide resin, unsaturated polyester resin, and diallyl terephthalate resin.

Note that Figure 8 shows an example configuration in which the first resin 600 and the second resin 800 are the same resin, but the first resin 600 and the second resin 800 may be different types of resin.

Figures 9A and 9B are schematic diagrams showing an embodiment configuration in which the first resin 600 and the second resin 800 are different types of resin. As shown in Figures 9A and 9B, the reinforcing material is first temporarily fixed with the first resin 600a in the first injection molding device 400a. The mold 100 is then moved to the second injection molding device 400b, where the second resin 800b is injected into the cavity. This allows the composite of this embodiment to be produced using the first resin 600a and the second resin 800a as different types of resin.

10A and 10B are schematic diagrams showing another embodiment in which the first resin 600 and the second resin 800 are different types of resin. In FIGS. 10A and 10B, an injection molding apparatus 400c is used, which has a first kneading apparatus 410ca connected to a first nozzle 432c via a flow path 422ca and a second kneading apparatus 410cb connected to a second nozzle 434c via a flow path 422cb. First, while keeping the second nozzle 434c closed, the first nozzle 432c is opened by the first opening/closing mechanism 442c, and the reinforcing material is temporarily fixed with the first resin 600c supplied from the first kneading apparatus 410ca. Next, while the first nozzle 432c remains closed, the second nozzle 434c is opened by the second opening/closing mechanism 444c, and a composite is produced using the second resin 800c supplied from the second kneading device 410cb.

When the reinforcing material 200 is a material containing resin, such as a resin member or fiber-reinforced resin, the second resin 800 is preferably compatible with the resin contained in the reinforcing material 200, and more preferably the same. If both resins are compatible or even the same, the two resins can be fused together to increase the bonding strength between the second resin 800 and the reinforcing material 200. Since this simplifies the device configuration and is expected to have the effect of improving both the strength of the temporary fixation and the bonding strength of the composite, it is preferable that the first resin 600 and the second resin 800 are both compatible with the resin contained in the reinforcing material 200, and more preferably the same.

After the composite is removed from the mold 100, the first resin 600 that has adhered to the reinforcing material 200 may be removed, if necessary.

[About reinforcement materials]
The type of reinforcing material 200 is not particularly limited, and may be any reinforcing material such as a resin member (including an oriented sheet), a fiber-reinforced resin, or a reinforcing fiber. The types of these resins and reinforcing fibers are not particularly limited, and any material may be used.

For example, when the reinforcing material 200 is relatively heavy, it is difficult to temporarily fix it in a non-horizontal position within the mold 100 using adhesives or suction. However, in this embodiment, the first resin 600 makes it easy to temporarily fix it, regardless of the shape of the mold or the configuration of the injection molding machine. This makes it possible to produce a composite with a simpler configuration without using a jig, which is expected to reduce costs when producing the composite and increase the freedom of designing the shape of the composite.

Furthermore, when the weight of the reinforcing material 200 is relatively small (for example, when the reinforcing material 200 is a reinforcing fiber or stretched sheet), displacement due to the injected resin is likely to occur. However, in this embodiment, the first resin 600 provides a stronger temporary fixation, more effectively suppressing displacement. Furthermore, to compensate for the insufficient displacement suppression effect of conventional temporary fixation, for example, Patent Document 1 requires the molten resin to contact the fiber-reinforced resin sheet from above, but this is not necessary in this embodiment. For example, as shown in Figures 8, 9B, and 10B, in this embodiment, the second resin 800 injected into the cavity 820 and flowing inside the cavity 820 can be brought into contact with the reinforcing material 200 from the side (first contacting the end in the thickness direction), providing sufficient displacement suppression effect.

The effects of the present invention are particularly pronounced when using a fiber-reinforced resin sheet as the reinforcing material 200, which is lightweight but has traditionally been difficult to temporarily hold down and prone to misalignment. Furthermore, because the orientation direction of the reinforcing fibers in a UD sheet is closely related to the direction in which strength is exerted, even a slight misalignment (misalignment of the reinforcing fibers) can significantly reduce the reinforcing effect of the composite. Therefore, the effects of the present invention are even more pronounced when using a UD sheet as the reinforcing material 200.

(About UD seats)
The UD sheet is a fiber-reinforced resin sheet including a plurality of reinforcing fibers aligned in one direction and a matrix resin impregnated into the plurality of reinforcing fibers.

The material of the reinforcing fibers is not particularly limited. For example, carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and metal fiber can be used as the reinforcing fibers. Of these, carbon fiber is preferred because it has excellent mechanical properties and can reduce the weight of molded products. Examples of the carbon fiber include PAN-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber. Of these, PAN-based long carbon fiber is preferred because it has an excellent balance between strength and elastic modulus.

The carbon fiber preferably has a surface oxygen concentration ratio [O/C], which is the ratio of the number of oxygen (O) to carbon (C) atoms on the surface of the carbon fiber as measured by X-ray photoelectron spectroscopy, of 0.05 to 0.5, more preferably 0.08 to 0.4, and even more preferably 0.1 to 0.3. A surface oxygen concentration ratio of 0.05 or greater ensures a sufficient number of functional groups on the carbon fiber surface, further enhancing adhesion to the matrix resin. A surface oxygen concentration ratio of 0.5 or less results in excellent handleability and productivity of the carbon fiber. The surface oxygen concentration ratio [O/C] can be measured by the method described in WO 2017/183672. The surface oxygen concentration ratio [O/C] can be controlled by known methods, including electrolytic oxidation, chemical oxidation, and gas-phase oxidation, but control by electrolytic oxidation is preferred.

From the viewpoint of fully enhancing the strength-improving effect of the reinforcing fibers, the average diameter of the reinforcing fibers is preferably 1 μm or more and 20 μm or less, more preferably 3 μm or more and 15 μm or less, and even more preferably 4 μm or more and 10 μm or less.

The length of the reinforcing fibers is typically 15 mm or more. The lower limit of the length of the reinforcing fibers is preferably 20 mm or more, more preferably 100 mm or more, and even more preferably 500 mm or more. The maximum upper limit of the length of the reinforcing fibers is preferably the same as the maximum length of the UD sheet, for example 50 m. Typically, the UD sheet used in the resin molding described below is a UD sheet that has been cut to the desired length after production. Therefore, the length of the reinforcing fibers contained in the UD sheet contained in the resin molding may be shorter than the minimum length mentioned above.

The reinforcing fibers are preferably formed by opening fiber bundles that have been bundled with a sizing agent. There are no particular restrictions on the number of single fibers in the fiber bundle, but it is typically between 100 and 350,000, preferably between 1,000 and 250,000, and more preferably between 5,000 and 220,000.

The sizing agent may be any known sizing agent, including olefin-based emulsions, urethane-based emulsions, epoxy-based emulsions, and nylon-based emulsions. Of these, olefin-based emulsions are preferred, and ethylene-based emulsions or propylene-based emulsions are more preferred. Examples of ethylene-based polymers contained in the ethylene-based emulsions include ethylene homopolymers and copolymers of ethylene and an α-olefin having 3 to 10 carbon atoms. Examples of propylene-based polymers contained in the propylene-based emulsions include propylene homopolymers and copolymers of propylene and ethylene or an α-olefin having 4 to 10 carbon atoms.

In particular, from the perspective of further enhancing the adhesion between the reinforcing fiber bundles and the matrix resin, the sizing agent preferably contains both an unmodified polyolefin and a modified polyolefin. The unmodified polyolefin is preferably homopolypropylene, homopolyethylene, ethylene-propylene copolymer, propylene-1-butene copolymer, or ethylene-propylene-1-butene copolymer. The modified polyolefin may be, for example, an unmodified polyolefin in which a carboxylic acid group, a carboxylic anhydride group, or a carboxylic acid ester group has been grafted onto the polymer chain, and in which a salt has been formed between the functional group and a metal cation. Of these, modified polyolefins containing a metal carboxylate salt are more preferred.

The matrix resin is a resin composition containing a thermoplastic resin or a thermosetting resin. The matrix resin may also contain fillers and other components other than the resin component.

Examples of the above thermoplastic resins include polycarbonate resin, styrene-based resin, polyamide resin, polyester resin, polyphenylene sulfide resin (PPS resin), modified polyphenylene ether resin (modified PPE resin), polyacetal resin (POM resin), liquid crystal polyester, polyarylate, acrylic resins including polymethyl methacrylate resin (PMMA), etc., polyolefins including vinyl chloride, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone (PEEK), polyethylene, polypropylene, polybutene, and poly4-methyl-1-pentene, etc., modified polyolefins which are modified products of these, and phenoxy resin. The polyolefin may be a copolymer including an ethylene/propylene copolymer, an ethylene/1-butene copolymer, an ethylene/propylene/diene copolymer, an ethylene/carbon monoxide/diene copolymer, an ethylene/ethyl (meth)acrylate copolymer, an ethylene/glycidyl (meth)acrylate copolymer, and an ethylene/vinyl acetate/glycidyl (meth)acrylate copolymer.

Examples of the thermosetting resin include epoxy resin, phenolic resin, melamine resin, urea resin, diallyl phthalate resin, silicone resin, urethane resin, furan resin, ketone resin, xylene resin, thermosetting polyimide resin, unsaturated polyester resin, and diallyl terephthalate resin.

Of these, thermoplastic resins are preferred from the viewpoints of increasing adhesion to the first resin, improving stability during temporary fixation, and increasing bonding strength with the second resin, as well as reducing melt viscosity to prevent resin leakage during temporary fixation and insert molding. Polyamide-based resins and polyester resins are preferred as resins with higher polarity, and polyolefin-based resins are preferred as resins with lower polarity. Furthermore, polypropylene-based resins and polyamide-based resins are preferred from the viewpoints of reducing costs and making the molded product lighter. Furthermore, the matrix resin may contain the aforementioned modified polyolefins from the viewpoint of increasing affinity with the reinforcing fibers bundled by the bundling agent.

The type of polypropylene resin is not particularly limited, and may be a propylene homopolymer, a propylene copolymer, or a mixture of these. The stereoregularity of the polypropylene resin is also not particularly limited, and may be isotactic, syndiotactic, or atactic. The stereoregularity is preferably isotactic or syndiotactic.

The polypropylene resin may be an unmodified polypropylene resin (P1), a modified polypropylene resin (P2) containing a carboxylate or the like bonded to the polymer chain, or a mixture thereof, but a mixture thereof is preferred. In the above mixture, the mass ratio of the unmodified polypropylene resin (P1) to the total mass of the unmodified polypropylene resin (P1) and the modified polypropylene resin (P2), [(P1)/(P1+P2)], is preferably 80% by mass or more and 99% by mass or less, more preferably 85% by mass or more and 98% by mass or less, and even more preferably 90% by mass or more and 97% by mass or less.

The type of polyamide resin is not particularly limited, and any known polyamide resin may be used. Examples of the polyamide resin include polyamide 6, polyamide 12, polyamide 66, polyamide 11, and aromatic polyamides. Of these, polyamide 6 and polyamide 12 are preferred.

The melt flow rate (MFR) of the polyamide resin, measured at 230°C under a load of 2.16 kg in accordance with ASTM D1238 after drying at 80°C for 5 hours, is preferably 40 g/10 min or more, and more preferably 40 g/10 min to 400 g/10 min. An MFR within this range makes it easier to sufficiently impregnate the reinforcing fibers with the matrix resin.

The weight-average molecular weight (Mw) of the above polyamide resin is preferably 5,000 or more and 50,000 or less, and more preferably 5,000 or more and 30,000 or less.

The matrix resin may contain other components, such as resins other than those mentioned above or short fibers shorter than the reinforcing fibers mentioned above.

[Other embodiments]
The above-described embodiment is merely an example of the present invention, and it will be understood by those skilled in the art that the present invention may take on configurations other than those described in the above-described embodiment based on its technical concept.

For example, in the above-described embodiment, the mold had one first gate and one second gate. However, the mold may have multiple first gates, or multiple second gates. For example, when placing reinforcing materials in multiple locations in the composite, the mold may have multiple first gates corresponding to the placement positions of these reinforcing materials, and these multiple first gates can temporarily fix the multiple reinforcing materials. When temporarily fixing multiple reinforcing materials, these reinforcing materials may be the same material, or may be different materials. Furthermore, from the perspective of more firmly temporarily fixing the reinforcing materials and preventing misalignment, it is preferable to have multiple first gates and fix one reinforcing material using these multiple first gates.

In addition, in the above-described embodiment, the cavity surface of the mold is flat. However, the cavity surface of the mold may be curved, or may have a shape in which multiple flat or curved surfaces are combined at a predetermined angle.

In addition, in the above-described embodiment, the first resin was in contact with a portion of the cavity surface side of the reinforcing material. However, the first resin may also be brought into contact with a portion of the cavity surface side of the reinforcing material to temporarily fix it. In this way, a composite body can be obtained in which a coating made of the first resin is formed on the surface of the reinforcing material. The coating made of the first resin can also be a protective coating or a color coating, or it can also be an inhibitor layer that inhibits the protrusion of the reinforcing fibers.

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

1. Preparation of Complex 1 (Example)
A composite with polypropylene was prepared using a UD sheet (manufactured by Mitsui Chemicals, Inc., TAFNEX ("TAFNEX" is a registered trademark of the company)) by the following method. This UD sheet contained polypropylene and carbon fiber, and had a fiber volume fraction (Vf) of 50% by volume and a thickness of 160 μm.

The mold shown in Figure 2 was installed in a vertical injection molding machine with a clamping force of 1000 tons, as shown in Figure 4. This mold had no special configuration, with the opening of the first gate being circular and having an inner diameter of 5 mm, and the distance between the first and second gates being 130 mm.

The UD sheet was cut to a size of 100 mm x 100 mm and placed vertically in the mold in a position covering the first gate. A 20 mm x 20 mm area containing the vertex of the square was set at one of the four corners of the square UD sheet, and the UD sheet was placed along the cavity surface of the mold so that this area covered the opening of the first gate. The UD sheet was also placed so that the corner of the four corners of the UD sheet included in the area covering the opening of the first gate was closest to the second gate, and so that the second gate was located on the extension of the diagonal line connecting the corner included in the area and the opposite corner. In this state, the UD sheet was temporarily held down against the cavity surface of the mold using a holding rod as a jig to prevent the UD sheet from shifting position when the first resin was introduced.

In this state, polypropylene (Prime Polypro J106G, manufactured by Prime Polymer Co., Ltd.) was introduced as the first resin through the first gate using the residual pressure within the injection molding machine, with an introduction time of 1 second and a resin temperature of 260°C. It had been confirmed that this polypropylene forms a single phase (is compatible) when heated and mixed with the polypropylene contained in the UD sheet above its melting point and cooled to 25°C. The injection molding machine's bubble pin was closed to stop the inflow of polypropylene, and the polypropylene was left to solidify for 240 seconds. The jig that had been temporarily holding the UD sheet was then removed. It was confirmed that the UD sheet, once the jig was removed, remained attached to the cavity surface of the mold and was temporarily fixed to it.

Next, the mold was closed to form a cavity, and polypropylene (Prime Polypro J106G, manufactured by Prime Polymer Co., Ltd.) was injected as the second resin through the second gate with an injection time of 2.7 seconds, a resin temperature of 230°C, an injection speed of 40 m/s, a dwell time of 5 seconds, and a dwell pressure of 20 MPa. The bubble pin of the injection molding machine was closed to stop the inflow of polypropylene, and the machine was then left for a predetermined time to solidify the polypropylene. The injection molding machine was then opened, and the composite comprising the UD sheet and the second resin was removed from the mold. When composite 1 was inspected, no misalignment of the UD sheet had occurred.

2. Preparation of Composite 2 (Comparative Example)
Without using a jig, the entire inner periphery of the UD sheet was temporarily fixed to the cavity surface of the mold with double-sided tape (Teraoka Seisakusho Co., Ltd., No. 760). Instead of introducing and solidifying the first resin through the first gate, the second resin was injected from the second gate while still temporarily fixed with the double-sided tape and solidified. Composite 2 was produced under the same conditions as for composite 1. When composite 2 was inspected, it was found that the UD sheet had shifted position.

This invention enables more accurate insert molding with a simpler configuration. It is expected that this invention will expand the possibilities of insert molding and contribute to the further spread and development of this field.

REFERENCE SIGNS LIST 100 Mold 110 First gate 110a Opening 120 Second gate 130 Cavity surface 200 Reinforcing material 400, 400a, 400b, 400c Injection molding apparatus 400a First injection molding apparatus 400b Second injection molding apparatus 410, 410ca, 410cb Kneading apparatus 410ca First kneading apparatus 410cb Second kneading apparatus 422, 422ca, 422cb Flow path 420 Manifold 430 Fixed platen 432, 432c First nozzle 434, 434c Second nozzle 442, 442c First opening/closing mechanism 444, 444c Second opening/closing mechanism 450 Retaining rod 600, 600a, 600c First resin 800, 800b, 800c Second resin 810 Movable core 820 Cavity

Claims (8)

placing a reinforcing material inside a mold having two or more gates at a position that contacts a cavity surface of the mold having an opening for a first gate and covers the first gate;
introducing a first resin through the first gate to temporarily fix the reinforcing material;
introducing a second resin through a second gate different from the first gate to form a composite of the temporarily fixed reinforcing material and the second resin;
A method for producing a composite having the following structure: the reinforcing material comprises a resin;
The method for producing a composite according to claim 1 , wherein the first resin is compatible with the resin contained in the reinforcing material. the reinforcing material comprises a resin;
The method for producing a composite according to claim 1 or 2, wherein the second resin is compatible with the resin contained in the reinforcing material. the reinforcing material comprises a resin;
The method for producing a composite according to any one of claims 1 to 3, wherein both the first resin and the second resin are compatible with the resin contained in the reinforcing material. The method for manufacturing a composite according to any one of claims 1 to 4, wherein the reinforcing material is a fiber-reinforced resin sheet. The method for manufacturing a composite according to any one of claims 1 to 5, wherein the reinforcing material is a fiber-reinforced resin sheet containing a plurality of reinforcing fibers aligned in one direction and a matrix resin impregnated into the plurality of reinforcing fibers. the reinforcing material is a reinforcing fiber;
The method for producing a composite according to claim 1 , wherein the molding step includes impregnating the reinforcing fibers with the second resin. The method for producing a composite according to any one of claims 1 to 7, wherein the first gate is arranged at a portion where the cavity surface of the mold is non-horizontal.