JP4988229B2 - A hybrid composite material excellent in surface smoothness and a molding method thereof. - Google Patents

Description

The present invention relates to a hybrid composite material having excellent surface smoothness, which is used as a fiber-reinforced plastic molded article, and a molding method thereof.

Fiber reinforced plastic molded products usually use composite materials composed of fiber reinforcement and matrix resin, and methods such as autoclave molding, resin transfer molding (RTM method), resin film infusion molding (RFI method), etc. Molded with. In the autoclave molding method, so-called prepreg is mainly used, and in the RTM method or RFI method, a fiber reinforcing material is laid in a mold and then a matrix resin is injected into the mold cavity, or a resin film is laid in the mold, A fiber reinforced plastic molded product is manufactured by a method in which a fiber reinforcing material is disposed thereon and the resin is melted and impregnated by heating.

As the fiber reinforcement used in the autoclave molding method, the RTM method, the RFI method and the like, a fiber reinforcement processed into a sheet shape such as a woven fabric is usually used. There are various forms of sheet-like fiber reinforcement, but woven fabrics and multiaxial fabrics are widely used. When sheet-like fiber reinforcements such as woven fabrics and multiaxial fabrics are placed on the surface of a fiber-reinforced plastic molded product, the unevenness of the texture and the unevenness of the stitches of the multiaxial fabric appear on the surface of the molded product. There is a drawback that the smoothness of the glass is impaired.

When using multiaxial woven fabric, as a method to improve surface smoothness, use low melting point polymer for stitch yarn of multiaxial woven fabric, and when molding fiber reinforced plastic molded product, heat molding above melting point of low melting point polymer A method of melting the stitch yarn has been introduced (Patent Document 1). However, even when using a multi-axial woven fabric using a low melting point polymer for the stitch yarn, the shape before the stitch yarn is melted is retained, and a slight dent is observed around the stitch yarn, and the surface is completely It is difficult to smooth out. In addition, as a method for improving the surface smoothness, a method of using a surface mat such as a nonwoven fabric or a gel coating agent on the surface of a molded product has been implemented. However, even if a surface mat is used, the surface of the product may not be smooth depending on the material and thickness of the surface mat and the type of fiber reinforcement used for the layer below the surface mat material.
JP 2002-227066 A

Alternatively, in order to form a fiber-reinforced plastic molded product having a complicated shape / pattern on the surface, a complicated shape / pattern is sufficient if a sheet-like fiber reinforcing material such as a woven fabric or a multiaxial fabric is used. Not formed. In such a case, a method of arranging chopped strands / prepregs on the surface layer portion is also known, but the conventional method has a problem that mechanical properties are lowered.

An object of the present invention is to provide a hybrid composite material for obtaining a fiber-reinforced plastic molded article having a smooth surface or a design surface having a complicated shape / pattern.

The invention described in claim 1 of the present invention is a hybrid composite material comprising a core layer and a surface layer laminated on one or both sides thereof, wherein the core layer is formed of a matrix resin and a fiber reinforcing material, A surface characterized in that the surface layer is formed from a chopped strand prepreg of a thermoplastic resin obtained by cutting a fiber-reinforced thermoplastic resin sheet formed by applying a thermoplastic resin to the aligned fiber bundle It is a hybrid composite material with excellent smoothness.

The invention described in claim 2 is a fiber reinforced heat formed by applying a thermoplastic resin to a bundle of fibers arranged on one side or both sides of a core layer formed of a thermoplastic resin and a continuous fiber reinforcing material. When a surface layer formed from a chopped strand prepreg of a thermoplastic resin obtained by cutting a plastic resin sheet is laminated and then the laminate is heated to form a hybrid composite material having excellent surface smoothness. A method for forming a hybrid composite material having excellent surface smoothness, wherein the chopped strand prepreg is laminated and disposed so that fiber orientation is random.

The invention described in claim 3 is characterized in that as the surface layer formed from the chopped strand prepreg, the surface layer previously integrated into a sheet shape by pressurization and / or partial adhesion is used. Item 3. A method for molding a hybrid composite material having excellent surface smoothness according to Item 2 .

The hybrid composite material of the present invention has a hybrid configuration of a surface layer formed from a chopped strand prepreg and a core layer formed from a matrix resin and a fiber reinforcing material. A smooth molding surface is obtained. In addition, according to the present invention, a fiber-reinforced composite material (molded product) having a design property (smoothness, glossiness, unevenness, etc.) surface corresponding to a complicated shape / pattern and excellent mechanical properties. Including) is obtained.

In the hybrid composite material of the present invention, a core layer formed from a matrix resin and a fiber reinforcing material is laminated with a surface layer formed from a chopped strand prepreg of a thermoplastic resin on one side or both sides. . In the present invention, the term “hybrid composite material” includes not only a fiber-reinforced plastic molded product finally molded, but also an intermediate composite material (core layer and / or surface layer partially before molding into a molded product). Intermediate material in an integrated state). When the composite material is finally formed into a fiber-reinforced plastic molded product for various uses, a design resin layer is formed on the outer surface of the surface layer constituting the composite material by painting or other methods. In some cases, such an embodiment is also included in the scope of the present invention.

There is no restriction | limiting in particular as a fiber reinforcement used for the core layer of this invention, The fiber which consists of an inorganic fiber, an organic fiber, a metal fiber, or those mixtures used for a normal composite material can be used. Examples of the inorganic fiber include carbon fiber, graphite fiber, silicon carbide fiber, alumina fiber, tungsten carbide fiber, boron fiber, and glass fiber. Examples of organic fibers include aramid fibers, high-density polyethylene fibers, and other general organic fibers such as nylon and polyester. As the metal fibers, fibers such as stainless steel and iron can be used, and there are also carbon fibers coated with metal. The fiber is preferably a continuous fiber (continuous fiber reinforcing material) such as a filament, a strand, a spun yarn, and a tow from the viewpoint of mechanical properties. Particularly preferred in the present invention is carbon fiber. In the case of carbon fibers, strands of 800-1600 tex, 12K-24K filaments are preferred.

The form of the fiber reinforcing material is not particularly limited, but for the purpose of the present invention, a sheet-like material processed into a woven fabric, a multiaxial woven fabric, a non-crimped woven fabric (see Japanese Patent Laid-Open No. 55-30974) or the like is suitable. Examples of the woven fabric include plain weave, twill weave, satin weave, and bias weave. Multiaxial woven fabric is a bundle of fiber reinforcements that are aligned in one direction and laminated at different angles, and stitched yarns such as nylon yarn, polyester yarn, and glass fiber yarn. It refers to a woven fabric that penetrates in the vertical direction and stitches by reciprocating along the surface direction between the front and back surfaces of the laminate. Although there is no restriction | limiting in particular about the fabric weight of a fiber reinforcement, For example, in the case of a polyaxial fabric, a fabric weight of about 100-2000 g / m < ² > is suitable.

As the matrix resin for forming the core layer of the present invention, a resin usually used for producing a molded product can be used, but a thermoplastic resin is preferable. As thermoplastic resins, polypropylene, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, aromatic polycarbonate, polyetherimide, polyarylene oxide, thermoplastic polyimide, polyamideimide, Examples thereof include one or more resins selected from the group consisting of polybutylene terephthalate, polyethylene terephthalate, polyethylene, polyamide (nylon), and acrylonitrile-butadiene-styrene (ABS) resin. Moreover, depending on a use, it can also be mixed and used partially with a thermosetting resin. Of these, polyamide resins and acrylonitrile-butadiene-styrene (ABS) resins having excellent heat resistance, elastic modulus, and chemical resistance are particularly preferable. These thermoplastic resins may contain commonly used colorants and various additives. The content of the matrix resin in the core layer is usually 10 to 70% by weight.

The core layer is formed by impregnating a fiber reinforcing material with a matrix resin. For example, when the matrix resin is a thermoplastic resin, a fiber, a nonwoven fabric, a mat, or a woven or knitted resin is heated to melt the fiber. A method of impregnating a reinforcing material (melt impregnation method), a method of applying and fusing a powdered resin to a fiber reinforcing material by a fluidized bed method or a suspension method (powder method), a solution of the resin, and impregnating the fiber reinforcing material Any method such as a method of removing the post solvent (solution impregnation method) may be used. In the present invention, when a thermoplastic resin melt-blown nonwoven fabric (see Japanese Patent Application Laid-Open No. 2005-220447) is used, since this nonwoven fabric is composed of fine fibers, the fiber reinforcing material has good impregnation properties and a preferable core layer is provided. can get. The basis weight of the resin is not particularly limited, but about 5 to 100 g / m ² is appropriate. In the case of a melt blown nonwoven fabric, those having a fiber diameter of 2 to 20 μm and a basis weight of about 5 to 100 g / m ² are preferable.

The surface layer of the present invention is formed from a chopped strand prepreg of a thermoplastic resin, and the types of the thermoplastic resin and the fiber reinforced material of the prepreg are the same as those in the core layer described above.

The chopped strand prepreg is a small piece of prepreg obtained by cutting a unidirectionally arranged strand (fiber bundle) using a thermoplastic resin as a matrix into a fiber length of, for example, about 5 mm to 50 mm. Although any chopped strand prepreg can be used in the present invention, a particularly preferred chopped strand prepreg has a fiber volume content (Vf) of the prepreg of 20 to 50% and the length of the prepreg in the fiber axis direction. The thickness is 15 to 45 mm, and the thickness of the prepreg is 0.13 mm or less. In the present invention, when forming the surface layer, the chopped strand prepreg is preferably laminated so that the fiber orientation is random. By using such chopped strand prepreg as a surface layer, the chopped strand prepreg flows in irregularities such as ribs, and smooth and precise shaping is performed.

In the chopped strand prepreg used in the present invention, strands (fiber bundles) of fiber reinforcing materials are aligned so that the thickness is 0.1 mm or less, and a thermoplastic resin is then added to the aligned fiber bundles in a fiber volume. The content (Vf) is applied so as to be in the range of 20 to 50%, and the formed fiber-reinforced thermoplastic resin sheet is in a desired width, preferably 10 to 30 mm, in the fiber axis direction with respect to the longitudinal direction. Is obtained by cutting so that the thickness is in the range of 5 to 50 mm, preferably 15 to 45 mm. The strands of the fiber reinforcement may be untwisted or twisted, but it is preferable to open the strands as much as possible when aligning. The method for applying the thermoplastic resin is not particularly limited. For example, a method of impregnating a fiber-reinforced material strand with a directly melted thermoplastic resin, a method of melting a film-shaped thermoplastic resin and impregnating a fiber-reinforced material strand, and melting a powdered thermoplastic resin There is a method of impregnating strands of fiber reinforcement. The method of cutting the strand of the fiber reinforcing material impregnated with the resin is not particularly limited, but a cutter such as a pelletizer, a guillotine method, or a Kodak method can be used.

The chopped strand prepreg is preferably deposited and laminated uniformly on the core layer so that the fiber orientation is random. As a method of depositing and laminating chopped strands and prepregs randomly and uniformly, for example, in the case of continuous production, the prepreg obtained by cutting is naturally dropped directly from a high position, and a belt conveyor such as a steel belt. -A method of depositing on the upper core layer, a method of blowing air into the dropping path, or a method of attaching a baffle plate are conceivable. In the case of batch type production, a method may be considered in which the cut prepreg is accumulated in a container, a conveying device is attached to the lower surface of the container, and the prepreg is dispersed in a mold for sheet production.

The hybrid composite material of the present invention has a surface layer formed from a chopped strand prepreg of a thermoplastic resin laminated on one or both sides of a core layer formed from a thermoplastic resin and a continuous fiber reinforcement, This laminate can be heated and molded / manufactured. At that time, it is preferable that the chopped strand prepreg is laminated by the above-described method and means so that the fiber orientation is random.

When molding / manufacturing the hybrid composite material of the present invention, the chopped strand prepreg may be laminated in a chopped form on the core layer, or alternatively, the layer comprising the chopped strand prepreg may be pre-pressurized and It is also possible to form and manufacture a hybrid composite material by integrating in a sheet form by partial adhesion and laminating and arranging such a surface layer on the core layer. As a method and means for forming a sheet, for example, a prepreg layer deposited on a steel belt is heated and pressed by passing the steel belt together between hot rolls, or intermittently pressed, so that the thermoplastic resin is made uniform. There is a method of partially melting and partially integrating the fiber reinforcement. Other methods of partial integration include, for example, a method in which heating and cooling are continuously performed by a belt press, a method in which a pre-heating is performed using a far infrared heater, a cold pressing, or a batch method in which a heating / cooling press is used. Can be considered. Particularly preferred is laminating a chopped strand prepreg on a steel belt so that the fiber orientation is random, and then laminating the laminate at 150-400 ° C. using a double belt press, intermittent hot press or hot roll. In this method, heating and pressurizing are performed at 0.1 to 10 MPa.

A design resin layer can be formed on the outer surface of the surface of the hybrid composite material of the present invention (the surface that is not in contact with the core layer) by coating or the like. In order to form such a resin layer, for example, acrylic, acrylurethane, fluorine, silicone, and epoxy resins can be used, and coloring agents such as dyes and pigments are added to the resin layer. You can also. Such a resin layer can be formed by a method of applying a design resin layer on the surface of the hybrid composite material, for example, a spray, a bar coater, a die coater, or a spinner method.

In the present invention, a surface layer formed from a chopped strand prepreg of a thermoplastic resin is laminated on one side or both sides of a core layer formed from a thermoplastic resin and a continuous fiber reinforcement, and then this laminate is As a method and means for molding a hybrid composite material having excellent surface smoothness by heating, conventionally known methods such as a die press method, an autoclave method, a heating / cold press method, a resin transfer molding method (RTM method) ), A resin film infusion molding method (RFI molding method) can be employed. At this time, in order to adjust the fiber volume content (Vf) or the resin content in the composite material, a thermoplastic resin can be additionally laminated as necessary. The content of the thermoplastic resin in the final molded product is usually 10 to 90% by weight, preferably 20 to 80% by weight.

Hereinafter, the present invention will be described in detail by way of examples. The fiber volume content (Vf) was measured according to the method of JIS K7075. The bending strength and the flexural modulus were measured according to JIS K 7017. The surface smoothness and shape imparting property were evaluated by visual evaluation of the surface of the obtained composite material. The resin impregnation property was evaluated by visually observing the cross section. The standard of visual evaluation was evaluated in four stages: very good (◎), good (○), slightly inferior (△), and inferior (×).

[Examples 1 and 2]
Using carbon fiber HTA-12K (800 tex, 12,000 strands, manufactured by Toho Tenax Co., Ltd.), a PA6 film (on a sheet of carbon fiber strands having a basis weight of 40 g / m ² in which long fibers are oriented in one direction) Nylon 6, manufactured by Unitika Co., Ltd., with a basis weight of 28.75 g / m ² ) was layered and heated to 230 to 260 ° C. to melt impregnate the PA6 film into the sheet. The obtained resin-impregnated sheet was 0.07 to 0.08 mm in thickness. The fiber volume fraction was 30%.

After slitting the resin-impregnated sheet-like material obtained above to a width of 20 mm (for one strand), using a guillotine type cutting machine, cutting the resulting chopped strand prepreg while cutting to a length of 25 mm, It dropped and deposited on a belt conveyor of a steel belt. The prepreg was laminated on a steel belt so that the fiber orientation was random. Subsequently, the laminate was heated and pressurized at 230 to 260 ° C. and 0.5 to 1.5 MPa using a hot roll to produce a surface layer used in the present invention.

Multiaxial woven fabric using carbon fiber HTA-12K (manufactured by Toho Tenax Co., Ltd.) (4 layers laminated at an angle of + 45 / −45 / −45 / + 45, 0.1 mm gap between strands, fabric weight of 800 g / m ² ) was cut into a width of 500 mm and a length of 500 mm. A surface layer (cut to a width of 500 mm and a length of 500 mm) obtained as described above is laid on a 700 × 700 mm mold, and two of the multiaxial fabrics are arranged on the surface layer. Further, a surface layer was laminated. A melt blown mat or film of nylon 6, which is a thermoplastic resin, was sandwiched between the two multiaxial fabrics and between the multiaxial fabric and the surface layer. Next, the mold was clamped and press molded at 250 ° C. for 0.5 hours under a pressure of 1 MPa. The properties of the obtained molded product are shown in Table 1. As the nylon 6 film, a film having a basis weight of 28.75 g / m ² was used (nylon 6, manufactured by Unitika Ltd.). Further, a nylon 6 melt blow mat having a basis weight of 100 g / m ² was used (manufactured by Kuraray Co., Ltd.).

[Comparative Examples 1-2]
A composite material was molded in the same manner as in Example 1 without using a surface layer, and the characteristics of the obtained molded product are shown in Table 1.
[Comparative Examples 3 to 4]
Using a thermoplastic resin for the surface layer, a composite material was molded in the same manner as in Example 1, and the properties of the obtained molded product are shown in Table 1.

[Example 3]
Instead of the multiaxial fabric of Example 1, the same as Example 1 except that 8 plain fabrics W-3101 (weight per unit area: 200 g / m ² ) using carbon fiber HTA-3K (manufactured by Toho Tenax Co., Ltd.) were used. Thus, the hybrid composite material of the present invention was obtained. When the cross-sectional thickness of the composite material was measured, the surface layer was 0.2 mm, the core layer was 1.6 mm, and the back side surface layer was 0.2 mm. When the surface of the obtained composite material was visually evaluated, there was no unevenness and the surface was clean.

[Example 4]
The surface of the composite material produced in Example 3 was polished with # 600 sandpaper and then urethane-coated (Kansai Paint Retan PG2K White) with a spray gun. The coating thickness was 0.1 mm. When the surface of the obtained composite material was visually evaluated, there was no unevenness and the surface was clean.

Claims (6)

In a hybrid composite material comprising a core layer and a surface layer laminated on one or both sides of the core layer, the core layer is formed of a matrix resin and a fiber reinforcing material, and the surface layer is formed by placing thermoplastic resin on the aligned fiber bundle. A hybrid composite material excellent in surface smoothness, characterized in that it is formed from a chopped strand prepreg of a thermoplastic resin obtained by cutting a fiber-reinforced thermoplastic resin sheet formed by application. It is obtained by cutting a fiber-reinforced thermoplastic resin sheet formed by applying a thermoplastic resin to a bundle of fibers aligned on one or both sides of a core layer formed from a thermoplastic resin and a continuous fiber reinforcement. When a surface layer formed from a chopped strand prepreg of a thermoplastic resin is laminated and then the laminate is heated to form a hybrid composite material having excellent surface smoothness, the chopped strand prepreg has a fiber orientation. A method for forming a hybrid composite material having excellent surface smoothness, wherein the layers are arranged so as to be random. 3. The hybrid composite with excellent surface smoothness according to claim 2 , wherein the surface layer formed from chopped strand prepreg is integrated with the surface layer in advance by pressing and / or partial adhesion. Material forming method. The method for molding a hybrid composite material having excellent surface smoothness according to claim 2 or 3, wherein the thermoplastic resin forming the core layer is a melt blown nonwoven fabric. The melt blown nonwoven fabric of thermoplastic resin has a fiber diameter of 2 to 20 μm and a basis weight of 5 to 100 g / m. ² The method for forming a hybrid composite material having excellent surface smoothness according to claim 4, which is a melt blown nonwoven fabric. As a surface layer formed from chopped strand prepreg, chopped strand prepreg is laminated on a steel belt so that the fiber orientation is random, and this laminate is then subjected to a double belt press, intermittent hot press or hot roll. It was excellent in surface smoothness according to any one of claims 2 to 5 using a sheet integrated by a method of heating and pressing at 0.1 to 10 MPa at 150 to 400 ° C. A method of forming a hybrid composite material.