JP7573577B2 - Resin molded body with a thickness of 1 mm or less - Google Patents

Description

The present invention relates to a fiber-reinforced resin composite molding and a method for manufacturing the same.

2. Description of the Related Art Fiber-reinforced resin molded articles have been used in a wide range of industrial fields, such as sports, leisure, and aviation, due to their high strength and high rigidity.
2. Description of the Related Art As a method for producing fiber-reinforced resin moldings, methods of compression molding prepregs in which reinforcing fibers are impregnated with a thermosetting resin, sheet molding compounds, and the like, are adopted in many fields.

Prepreg uses long fibers as reinforcing fibers, which allows for the production of molded products with high strength and rigidity, but it is difficult to mold them into complex shapes. In contrast, sheet molding compounds use short fibers as reinforcing fibers, which means that the strength of the molded products is lower than that of prepreg, but they have excellent fluidity during molding and can be easily molded into complex shapes such as ribs and bosses.

In addition, in order to incorporate the advantages of both prepregs and sheet molding compounds, while maintaining rigidity, and enabling the creation of complex shapes, it has been proposed to laminate prepregs and sheet molding compounds and perform compression molding (Patent Document 1).

JP 2009-083441 A

However, in the case of a composite molded product made by laminating prepregs and sheet molding compounds and compressing them, the thickness of the layer formed from the sheet molding compound can only be about 70% of the thickness of the sheet molding compound before compression molding, so the overall thickness of the molded product cannot be made thin, and it has not been possible to obtain a thin-walled molded product that is rigid and can be molded into complex shapes.

The present invention has been made in consideration of the above points, and aims to provide a fiber-reinforced resin composite molding that has rigidity and can be formed into complex shapes and thin walls, and a manufacturing method thereof.

A first aspect of the invention relates to a fiber-reinforced resin composite molding comprising a rigid layer formed from a fiber-reinforced resin material for the rigid layer, a mold layer formed on at least one side of the rigid layer from a compound for the mold layer comprising fibers shorter than the fibers contained in the fiber-reinforced resin material for the rigid layer and a thermosetting resin, and a resin formed by hardening liquid resin adhered to the surface of the mold layer, wherein the fiber-reinforced resin material for the rigid layer and the compound for the mold layer are heated, compressed, and hardened together with the liquid resin in a laminated state.

A second aspect of the invention is characterized in that, in the first aspect of the invention , the fiber-reinforced resin material for the rigid layer is a prepreg, the compound for the shape-imparting layer is a sheet molding compound, and the liquid resin is a thermosetting resin.

A third aspect of the invention is a method for producing a fiber-reinforced resin composite molding comprising a rigid layer formed from a fiber-reinforced resin material for a rigid layer, a mold layer formed on at least one side of the rigid layer from a compound for a mold layer comprising fibers shorter than the fibers contained in the fiber-reinforced resin material for the rigid layer and a thermosetting resin, and a resin formed by hardening the liquid resin adhering to the surface of the mold layer, characterized in that a liquid resin is applied to the surface of the compound for the mold layer, or a liquid resin is applied to a mold surface of a mold that will press the surface of the compound for the mold layer, and the fiber-reinforced resin material for the rigid layer and the compound for the mold layer are heated and compressed in the mold together with the liquid resin in a stacked state, and hardened.

A fourth aspect of the invention is characterized in that, in the third aspect of the invention , the fiber-reinforced resin material for the rigid layer is a prepreg, the compound for the shape-imparting layer is a sheet molding compound, and the liquid resin is a thermosetting resin.

According to the present invention, the fiber-reinforced resin composite molded body is a product of heating, compressing and curing the fiber-reinforced resin material for the rigid layer, the compound for the mold layer and the liquid resin in a laminated state together with the liquid resin. During heating and compression by a mold to manufacture the fiber-reinforced resin composite molded body, the liquid resin acts as an insulating layer between the compound for the mold layer and the mold surface of the mold, and the curing reaction of the compound for the mold layer is delayed. This increases the flow rate of the compound for the mold layer until the completion of curing, and the mold layer formed from the compound for the mold layer can be made thin. Furthermore, the liquid resin acts as a lubricant between the compound for the mold layer and the mold surface of the mold to improve the fluidity of the compound for the mold layer, which also makes it possible to make the mold layer thinner. As a result, a fiber-reinforced resin composite molded body that has rigidity due to the rigid layer and can be shaped into a complex shape by the mold layer and is further thin can be obtained.

1 is a cross-sectional view of one embodiment of a fiber-reinforced resin composite molded product according to the present invention. FIG. 2 is a cross-sectional view of one embodiment of a mold. 1 is a table showing the configuration of the applied resin and the thickness after molding in each of the examples and comparative examples.

The fiber-reinforced resin composite molded product and the method for producing the same of the present invention will be described below.
The fiber-reinforced resin composite molding 10 shown in Figure 1 comprises a rigid layer 11 formed from a rigid fiber-reinforced resin material, a mold layer 21 formed from a mold layer compound, and resin 31 formed by hardening liquid resin adhered to the surface of the mold layer compound.

The rigid layer 11 is made of a fiber-reinforced resin material for a rigid layer that is heated, compressed, and cured.
The fiber reinforced resin material for the rigid layer is a fiber sheet impregnated with a thermosetting resin. Examples of the fiber sheet include those made of fibers such as carbon fiber, glass fiber, and aramid fiber. In particular, carbon fiber is preferable from the viewpoints of weight reduction and improved rigidity. The fiber sheet may be woven, knitted, nonwoven, etc. Examples of the woven fabric include plain weave, twill weave, satin weave, and triaxial weave. The fiber sheet may be made of fibers oriented in one direction or multiple directions. The fiber sheet is preferably a woven fiber from the viewpoint of improved rigidity.

The fibers constituting the fiber sheet are preferably longer than the fibers contained in the compound for the mold layer described below, and may be, for example, continuous or discontinuous fibers.

Thermosetting resins impregnated into the fiber sheet include epoxy resins, phenolic resins, vinyl ester resins, unsaturated polyester resins, and mixtures of these resins. Prepregs are preferred as fiber-reinforced resin materials for rigid layers in which the fiber sheet is impregnated with a thermosetting resin.

The shaping layer 21 is made of a compound for the shaping layer, which is made of a thermosetting resin and fibers shorter than those contained in the fiber-reinforced resin material for the rigid layer, and is heated, compressed, and hardened. The surface shape of the shaping layer 21 may be an appropriate concave, convex, or uneven shape depending on the application of the fiber-reinforced resin composite molding 10.

The length of the fibers contained in the compound for the mold layer is preferably 30 mm or less from the viewpoint of moldability, and 5 mm or more from the viewpoint of improving rigidity. Examples of fibers contained in the compound for the mold layer include short fibers such as carbon fiber and glass fiber. Carbon fiber is particularly preferred from the viewpoints of weight reduction and improving rigidity.

Examples of the thermosetting resin contained in the compound for the mold layer include epoxy resin, phenol resin, vinyl ester resin, unsaturated polyester resin, and mixed resins thereof.
The compound for the mold layer is preferably a sheet molding compound (hereinafter referred to as SMC). SMC refers to a sheet-shaped molding material in which a compound containing a thermosetting resin, a filler, a curing agent, etc. is impregnated into a fiber material such as glass fiber or carbon fiber.

The resin 31 is made of a hardened liquid resin. The liquid resin is made of a thermosetting resin. When the fiber-reinforced resin composite molding 10 is produced, the liquid resin is heated and compressed together with the compound for the mold layer, and mixes with the hardener for the thermosetting resin contained in the compound for the mold layer, so that the resin can harden even without the hardener.

The thermosetting resin constituting the liquid resin is preferably a radical polymerization type thermosetting resin such as vinyl ester resin, unsaturated polyester resin, or epoxy resin. If necessary, a hardener, dispersant, flame retardant, UV absorber, etc. may be added to the thermosetting resin. In addition, a solvent may be mixed with the thermosetting resin to adjust the viscosity of the liquid resin so that it can be applied.

The rigid layer 11, the molding layer 21, and the resin 31 are integrated together by hardening the fiber-reinforced resin material for the rigid layer, the compound for the molding layer, and the liquid resin on the surface of the compound in a layered state through heating and compression during the manufacture of the fiber-reinforced resin composite molded body 10.

The manufacturing method of the fiber-reinforced resin composite molded body 10 is explained below. The manufacturing method of the fiber-reinforced resin composite molded body 10 consists of a coating process and a heating and compressing process.

In the coating process, uncured liquid resin is applied to one side surface of the compound for the mold layer or to the mold surface of the mold. The mold 60 shown in FIG. 2 is composed of an upper mold 61 and a lower mold 63. When applying uncured liquid resin to the mold surface of the mold, the liquid resin is applied to the mold surface that will press the compound for the mold layer in the next heating and compression process, for example, the mold surface of the upper mold 61. In addition, the liquid resin may be applied to one side surface of the compound for the mold layer by stacking the fiber-reinforced resin material for the rigid layer and the compound for the mold layer on the lower mold 63 of the mold 60, and applying the liquid resin to the surface of the compound for the mold layer. The coating method may be brush coating, roller coating, spray coating, or the like, and any method may be used. In addition, the area to which the liquid resin is applied is not limited to the entire surface of the compound for the mold layer, and may be a part of it.

The compound for the mold-imparting layer is as described in the fiber-reinforced resin composite molded body 10. The size of the compound for the mold-imparting layer used here is preferably 30 to 100% of the planar dimensions of the product (fiber-reinforced resin composite molded body 10).
The liquid resin is as described in the fiber-reinforced resin composite molded body 10. The amount of liquid resin applied to the surface of the compound for the mold layer is preferably 20 to 200 g/ ^m2 .

In the heating and compressing process, the fiber reinforced resin material for the rigid layer, the compound for the shaping layer, and the liquid resin are arranged in a layered state between the mold surfaces of the upper die 61 and the lower die 63 of the metal mold 60, and are heated and compressed in this state by the mold surfaces of the upper die 63 and the lower die 61. A cavity for shaping the fiber reinforced resin composite molding 10 is formed in the lower die 63. The planar size of the cavity for shaping is set to be equal to the planar size of the fiber reinforced resin composite molding 10.

By heating and compression, the fiber-reinforced resin material for the rigid layer is compressed, and the compound for the mold layer is compressed and flows in the mold 60, and the fiber-reinforced resin material for the rigid layer and the compound for the mold layer are molded into the cavity shape and hardened. At that time, since the liquid resin is present between the compound for the mold layer and the mold surface, the liquid resin acts as a lubricant on the surface of the compound for the mold layer, improving the fluidity of the compound for the mold layer in the mold 60, and the compound for the mold layer is molded thinly. In addition, the liquid resin acts as an insulating layer between the compound for the mold layer and the mold surface, delaying the hardening reaction of the compound for the mold layer due to heat transfer from the mold surface, and increasing the flow amount of the compound for the mold layer until hardening is completed, which also causes the compound for the mold layer to be molded thinly.

During heating and compression, the liquid resin on the surface of the compound for the mold layer is pressed by the mold surface, and mixes with the thermosetting resin on the surface of the compound for the mold layer and in its vicinity, and hardens. At that time, even if the liquid resin does not contain a hardener, it can harden by mixing with the hardener contained in the compound for the mold layer.

Heating during the heat compression process is performed by a heating means such as an electric heater installed in the mold, or by a method in which the mold is placed in a heating furnace or the like and heated in advance. The heating temperature is set to a temperature at which the thermosetting resin and liquid resin contained in the fiber-reinforced resin material for the rigid layer and the compound for the mold-imparting layer harden.

The heating and compressing process integrates the rigid layer formed by compressing and hardening the fiber-reinforced resin material for the rigid layer, the shaping layer formed by compressing and hardening the compound for the shaping layer in a thin shaped state, and the resin formed by hardening the liquid resin on its surface, resulting in a thin fiber-reinforced resin composite molded body 10 consisting of the rigid layer 11, the shaping layer 21, and the resin 31 on its surface, as shown in Figure 1.

A carbon fiber fabric (Teijin Limited, product name: W-3161L, thickness 0.22 mm) cut to 400 x 400 mm was immersed in a phenolic resin solution (Sumitomo Bakelite Co., Ltd., product name: PR-55791B, resin concentration 60 wt% ethanol solution), removed, and naturally dried at room temperature of 25°C for 2 hours, and then dried in an atmosphere of 60°C for 1 hour to form a fiber-reinforced resin material (prepreg) for the rigid layer.

A sheet of fiber-reinforced resin material (prepreg) for rigid layer is placed on the molding surface of the lower mold of the mold, and a compound for molding layer (SMC, manufactured by Mitsubishi Chemical Corporation, product name: STR120N131, thickness 2 mm, fiber content 53%) cut to a size of 300 x 300 mm is laminated on it, and the surface of the compound for molding layer is coated with a liquid uncured coating resin (thermosetting resin) shown in each example of FIG. 3 with a brush, and then the mold is closed and heated and compressed at 150 ° C. x 20 minutes at a pressure of 200 kgf / cm ² to cure the fiber-reinforced resin material for rigid layer (prepreg), the compound for molding layer, and the coating resin in a laminated compressed state. As a result, a fiber-reinforced resin composite molded body consisting of a laminated integral product of a rigid layer formed from a fiber-reinforced resin material for rigid layer (prepreg), a molding layer formed from a compound for molding layer, and a resin formed from a coating resin was produced. The mold is composed of a lower mold and an upper mold, and has a molding surface of 460 mm wide x 460 mm long.

In addition, the fiber-reinforced resin composite moldings of Comparative Examples 1 to 3 were produced by hot compression molding the compound for the mold layer without applying a thermosetting resin to the surface thereof.
The thickness after molding was measured for the fiber-reinforced resin composite molded body of each Example and each Comparative Example. The results are shown in FIG. 3. The charge rate [%] in FIG. 3 is the ratio of the thickness of the molded layer to the original thickness (2 mm) of the compound for the molded layer. In calculating the charge rate, the thickness of the molded layer was calculated by subtracting the thickness (0.22 mm) of the fiber-reinforced resin material (prepreg) for the rigid layer from the thickness after molding (thickness of the fiber-reinforced resin composite molded body), assuming that the thickness (0.22 mm) of the fiber-reinforced resin material (prepreg) for the rigid layer does not change due to heating and compression.

Example 1 is an example in which 50 g/m ² of vinyl ester resin (manufactured by Showa Denko K.K., product name: Lipoxy R-806) was applied as a coating resin (thermosetting resin) to the surface of the compound for the mold layer. In Example 1, the thickness of the fiber-reinforced resin composite molded body after molding was 0.95 mm and the charge rate was 37%. The thickness of the mold layer formed from the compound for the mold layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molded body (0.95 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 0.73 mm, and the mold layer was formed thin.

Example 2 is an example in which the same vinyl ester resin (manufactured by Showa Denko K.K., product name: Lipoxy R-806) as in Example 1 was applied to the surface of the compound for the mold layer at 75 g/m ² as the coating resin (thermosetting resin). In Example 2, the thickness of the fiber-reinforced resin composite molded body after molding was 0.93 mm and the charge rate was 36%. The thickness of the mold layer formed from the compound for the mold layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molded body (0.93 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 0.71 mm, and the amount of coating resin applied was increased compared to Example 1, so that the mold layer was formed thinner than in Example 1.

Example 3 is an example in which the same vinyl ester resin (manufactured by Showa Denko K.K., product name: Lipoxy R-806) as in Examples 1 and 2 was applied to the surface of the compound for the mold layer at 100 g/m ² as the coating resin (thermosetting resin). In Example 3, the thickness of the fiber-reinforced resin composite molded body after molding was 0.91 mm and the charge rate was 35%. The thickness of the mold layer formed from the compound for the mold layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molded body (0.91 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 0.69 mm, and the amount of coating resin was increased more than in Examples 1 and 2, so that the mold layer was formed even thinner than in Examples 1 and 2.

Example 4 is an example in which 50 g/m ² of unsaturated polyester resin (manufactured by Showa Denko K.K., product name: RIGOLAC T-543TPA) was applied as a coating resin (thermosetting resin) to the surface of the compound for the mold layer. In Example 4, the thickness of the fiber-reinforced resin composite molded body after molding was 1.00 mm, and the charge rate was 39%. The thickness of the mold layer formed from the compound for the mold layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molded body (1.00 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 0.78 mm, and it was formed thin.

In this way, in Examples 1 to 4, by applying a liquid thermosetting resin to the surface of the compound for the mold layer laminated to the fiber-reinforced resin material (prepreg) for the rigid layer and then performing heat compression molding, the thickness of the mold layer formed from the compound for the mold layer could be thinned to 0.69 to 0.78 mm, and a thin fiber-reinforced resin composite molded body with a thickness of 1 mm or less could be obtained.

Comparative Example 1 is an example in which liquid thermosetting resin was not applied to the surface of the compound for the mold layer, and the heating and compression conditions were the same as those of Examples 1 to 4. In Comparative Example 1, the thickness of the fiber-reinforced resin composite molding after molding was 1.12 mm, and the charge rate was 45%. The thickness of the mold layer formed from the compound for the mold layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molding (1.12 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 0.90 mm, and the mold layer was formed thicker than Examples 1 to 4 by not applying liquid thermosetting resin to the surface of the compound for the mold layer.

Comparative Example 2 is an example in which the area of the compound for the molding layer in Comparative Example 1 was increased by 10%, and liquid thermosetting resin was not applied. In Comparative Example 2, the thickness of the fiber-reinforced resin composite molding after molding was 1.30 mm, and the charge rate was 54%. The thickness of the molding layer formed from the compound for the molding layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molding (1.30 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 1.08 mm, and by increasing the amount of compound for the molding layer, the molding layer was formed thicker than in Comparative Example 1.

Comparative Example 3 is an example in which the area of the compound for the molding layer in Comparative Example 1 was increased by 20%, and liquid thermosetting resin was not applied. In Comparative Example 3, the thickness of the fiber-reinforced resin composite molding after molding was 1.60 mm, and the charge rate was 69%. The thickness of the molding layer formed from the compound for the molding layer (thickness 2 mm) was the thickness of the fiber-reinforced resin composite molding (1.60 mm) - the thickness of the fiber-reinforced resin material for the rigid layer (0.22 mm) = 1.38 mm, and by increasing the amount of compound for the molding layer, the molding layer was formed thicker than Comparative Examples 1 and 2.

In this way, the present invention makes it possible to obtain a fiber-reinforced resin composite molding that has both the rigidity provided by the rigid layer and the ability to be molded into a complex shape with a thin wall provided by the molding layer.

Reference Signs List 10 Fiber-reinforced resin composite molded body 11 Rigid layer 21 Shape-imparting layer 31 Resin 60 Mold 61 Upper mold 63 Lower mold

Claims (2)

A cured resin layer;
A shape-imparting layer containing only a thermosetting resin and short fibers having a fiber length of 30 mm or less;
a rigid layer including only fiber sheets having a fiber length longer than the short fibers,
The cured resin layer, the shape-imparting layer, and the rigid layer are laminated in this order.
A resin molded body with a thickness of 1 mm or less. A cured resin layer;
A shape-imparting layer made of a sheet molding compound containing a thermosetting resin and short fibers having a fiber length of 30 mm or less;
and a rigid layer made of a prepreg including a fiber sheet having a fiber length longer than the short fibers,
The cured resin layer, the shape-imparting layer, and the rigid layer are laminated in this order.
A resin molded body with a thickness of 1 mm or less.

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