JP2518554B2 - Method for producing molded article of thermoplastic polymer-based composite material reinforced with carbon fiber - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite material molded article from a reinforcing material mainly composed of carbon fiber and a thermoplastic polymer. More specifically, the present invention relates to a method for producing a composite material molded article by passing an electric current through the carbon fibers in the reinforcing material to generate heat, and softening or melting the thermoplastic polymer by the heat to impregnate the reinforcing material to impregnate the reinforcing material.

[0002]

2. Description of the Related Art So-called high-performance composite material molded products using long-fiber carbon fibers as a reinforcing material are usually manufactured by a hot press molding method, an autoclave molding method, a diaphragm molding method, etc., and are used for tennis rackets, golf club shafts, etc. Is applied to aircraft structural materials such as sports equipment, helicopter blades and aircraft wings.

Most of these composite material molded products use a thermosetting resin such as an epoxy resin or an unsaturated polyester resin as a matrix resin. Since the resin has a low viscosity, the resin in the reinforcing fiber is used. Although the impregnation is good, it requires a long time for molding because it involves a reaction.

On the other hand, when a thermoplastic polymer is used as a matrix resin, a high temperature is required to soften or melt the thermoplastic polymer, and the viscosity of the softened and melted polymer is high, so that the polymer is reinforced in the reinforcing fiber. It has the drawback of being difficult to impregnate. For example, in the usual hot press molding method for thermoplastic polymer composite molded articles,
In order to soften and melt the polymer, it is necessary to heat the press platen and the mold for molding, which not only consumes excessive energy, but also takes a long time to impregnate into the reinforcing fiber and prolongs the molding cycle. There is a drawback.

[0005]

DISCLOSURE OF THE INVENTION The present invention shortens the molding cycle in producing a composite material molded article using a thermoplastic polymer as a matrix resin by using a reinforcing material containing carbon fiber as a main component, It is therefore an object of the present invention to provide a method for rationally producing a high performance composite material molded article by improving the production rate, reducing the energy loss, and remarkably enhancing the impregnation property of the polymer into the reinforcing material. Is.

[0006]

The main object of the present invention is to apply an electric current directly to the carbon fibers in the reinforcing material constituting the composite material molded article to generate heat, and the heat softens or melts the thermoplastic polymer. The purpose of this is to rapidly and efficiently manufacture a high-performance composite material molded product in the absence of voids.

That is, the present invention differs from the usual hot press molding method in which heat is applied through a press board or a molding die to soften or melt the polymer, and an electric current is applied to the carbon fiber in the reinforcing material. The carbon fiber itself is caused to generate heat, and the heat causes the thermoplastic polymer in the peripheral portion to be softened or melted, so that the reinforcing material is quickly impregnated.

As a conventional method for producing a molded article by passing heat through carbon fibers to generate heat, a method has been proposed in which a material to be molded is sandwiched by electrodes from above and below and is pressed with energization heat generation (" Journal of the Japan Aerospace Society, 37th
Volume 424, pp. 238-246, ibid. 438, 37
1-38).

In this method, an electrode such as a copper foil is inserted between the material containing the carbon fiber to be molded and the molding die as described above, and the energy is applied in the direction perpendicular to the surface of the material. The aim is to reduce consumption and shorten the molding cycle. However, since pressure molding is performed via the electrodes, fluctuations in load pressure lead to fluctuations in current, making temperature control difficult.

On the other hand, the present invention is a method for supplying electricity to the carbon fibers in the reinforcing material along the surface direction of the reinforcing material containing carbon fiber as a main component, and for molding a composite material molded article. The current can be controlled independently of the required load pressure. That is, it is possible to manufacture a high-quality molded product by minimizing the variation in heating temperature and easily controlling the amount of current. Further, as will be described later, a flat or curved flat surface, a rod shape, a pipe shape, a box shape, or other various shapes of molded articles can be manufactured by a batch or continuous process by selecting the shape of the electrodes for energization and the connection method. Is possible.

In the present invention, it is possible to use alternating current and direct current, but it is preferable to use alternating current, particularly when obtaining a large-sized molded product or when manufacturing in a high cycle.

From the relationship of thermal efficiency in the impregnation / molding process and the molding cycle, the proportion of carbon fibers used in the composite material molded article according to the present invention is preferably 70% by weight or more, and more preferably 80% by weight or more of the total reinforcing material. More preferable. Examples of the reinforcing fiber used together with the carbon fiber include glass fiber, aramid fiber, ceramic fiber and the like, which are usually used as the reinforcing fiber of the composite material molded article.

The carbon fiber used in the present invention is a long fiber, and the shape of the reinforcing material is a multi-fabric sheet of aligned type (so-called UD sheet), a sheet material such as a woven or knitted material, a blade or a filament wind. It is a cylindrical object or a three-dimensional object. Also,
Not only the above-mentioned various shapes are used alone, but also used in combination with a fibrous matrix obtained from a thermoplastic polymer described below to form a UD carbon fiber / thermoplastic knit fabric, carbon fiber / thermoplastic polymer woven fabric or co-blade product. It is also possible to use in a form in which the reinforcing material and the matrix thermoplastic polymer are integrated. In any case, the carbon fibers overlap with each other or come into contact with each other via a conductor, whereby an electric current flows along the surface direction of the reinforcing material.

As the thermoplastic polymer used in the present invention, the thermoplastic polymers used for ordinary molded articles of composite materials can be used, such as polycarbonate, polyamide (various nylons), polybutylene terephthalate,
Engineering plastics such as polyethylene terephthalate, polyphenylene sulfide and polyurethane, and super engineering plastics such as polyether ether ketone, polyether imide, polyether sulfone and polyimide can be used. Among them, thermoplastic polymers such as polycarbonate, various nylons, polyetheretherketone, polyphenylene sulfide, etc. are preferable for application fields requiring toughness or heat resistance.

The form of the thermoplastic polymer used together with the reinforcing material in the present invention may be a film form, a sheet form, a fabric form (woven fabric, knitted fabric, etc.), a non-woven fabric (non-woven), a matte form and the like. In order to further enhance the effect of heat molding due to electric current and heat generation to the carbon fiber, which is a feature of the present invention, it is preferable that it is in the form of a film, a thin sheet or a fabric.

Since the present invention is characterized by a method in which an electric current is directly applied to the carbon fiber which is the main component of the reinforcing material to generate heat as described above, the reinforcing material, matrix and electrodes constituting the composite material molded article are It is necessary to maintain an electrically insulating state between the system described above and the molding die, and specifically, it is necessary to insulate via a suitable electrically insulating material. Examples of preferable insulating materials include ceramic coatings, fluorine coatings, insulating films, and the like.

In the method of the present invention, the carbon fibers are directly energized to generate heat, and the heat softens or melts the polymer. In order to further improve thermal efficiency, the outer portion of the molding die is made of heat-resistant material. It is preferably covered with a good insulating material. Specific examples of such a heat insulating material include heat-resistant resins such as fluorine-based or polyimide-based resins or sheet-like materials thereof, ceramic sheets or blocks, and inorganic-based sheets such as asbestos.

In the present invention, pressure is applied during molding in order to improve the properties of the intended composite material molded article and to accelerate the impregnation of the polymer in the reinforcing material. Is preferred. The pressure depends on the type of the target polymer or the molding temperature,
Usually, 5 to 30 kgf / cm ² is used, but it is not particularly limited to this.

In the present invention, an ordinary electrically conductive material is used as the electrode used for passing an electric current through the carbon fiber, and a typical material thereof is a metal material such as copper, iron and aluminum.

The form of the electrode and the method of contact with the carbon fiber are not particularly limited, but a typical contact method is (a)
A method of sandwiching them between bar-shaped electrodes, (b) a method of embedding a planar electrode in a part of an electric insulating layer so that both are in the same plane,
A roll-shaped surface contact method, a method using (d) a point electrode, or the like can be adopted.

FIGS. 1 to 5 show specific examples thereof. FIG. 1 shows a layer (hereinafter referred to as a composite material component) composed of a reinforcing material containing a carbon fiber as a main component and a thermoplastic polymer (hereinafter referred to as a composite material component) (1). ) Above and below, and a pair of molding dies having an electrically insulating material (2) such as a fluororesin coating and a heat insulating material (3) such as asbestos or porous ceramics (4) interposed therebetween. And a pair of bar-shaped electrodes (5) are provided near the inlets on both sides of the mold to form a composite material component (1).
This is an example in which an electric current is caused to flow along the surface direction of the reinforcing material (horizontal direction in FIG. 1) by contacting with the carbon fiber inside. In this example, at the time of molding, the upper and lower molding dies sandwich the composite material component (1) and preferably press it to produce a composite material molded article having a predetermined shape.

In FIG. 2, a bar-shaped electrode (6) is embedded in a part of the electric insulating material (2) provided on the innermost surface of the molding die to form the electrode (6) and the electric insulating material (2). This is an example in which the surfaces are aligned. At the time of molding, the composite material component (1) sandwiched between the upper and lower molding dies is pressed to flow a current along the surface direction of the reinforced material (almost horizontally in FIG. 2). This is an example.

In FIG. 3, point-shaped electrodes are used instead of the bar-shaped electrodes of FIG. 1, and the composite material component (1) is pressed by a pair of upper and lower molding dies along the surface direction of the reinforcing material. This is an example in which a current is passed (in the horizontal direction in FIG. 3).

FIG. 4 shows a cylindrical mold material (4) having an electrically insulating material (2) on its inner surface and an electrically insulating material (2) on its outer surface.
It is an example of producing a cylindrical composite material molded article using a mandrel (9) having a ring, and a ring-shaped electrode (6a) provided on the inner wall surface of one inlet of the molding die and the vicinity of the outlet. A strip-shaped electrode (6) provided on a part of the peripheral surface of the mandrel (9)
b) is brought into contact with the carbon fibers in the composite material component (1), and an electric current is applied to the carbon fibers between the electrodes. The center of FIG. 4 is a partially cutaway cross-sectional view, and both ends are cross-sectional views near the respective ends.

FIG. 5 shows an example of producing a continuous-length sheet-shaped composite material molded product by using a pair of nip rolls (8). The surface of the roll (8) serving as a molding die is an electrically insulating material (2). ), And a strip-shaped electrode (6) is provided on a part of its peripheral surface. In this example, the electrode (6) and the carbon fibers in the composite material component contact each other while the composite material component (1) continuously passes between the rolls, and a current flows in the width direction of the composite material component (1). It is like this.

In the method of the present invention, an appropriate electric current is applied to the carbon fibers in the reinforcing material in the composite material component (1) along the plane direction of the reinforcing material by the means as described above. It is essential to heat the carbon fiber. On the other hand, as is conventionally known, the composite material component (1)
It is difficult to control the temperature of the composite material component (1) at an arbitrary temperature during molding by the method of energizing the composite material in the vertical direction, and the molding productivity is poor, so that the composite material molded article is industrially manufactured. Is not suitable for.

[0027]

According to the method of the present invention as described above, since the carbon fibers themselves are heated by the energization at the time of molding, the compatibility with the thermoplastic polymer is improved and the adhesion between the reinforcing material and the polymer is improved. However, it is possible to obtain a high-performance composite material molded article having high strength and toughness. Further, the method of the present invention has a small heat loss and therefore a desired composite material molded article with high energy efficiency, since the carbon fiber is directly heated by heating, not by heating the press board or the molding die. It is possible to obtain. Further, by using the method of the present invention, the production speed (molding cycle) of the composite material molded product is remarkably improved, and improvement of productivity and improvement of thermal efficiency (reduction of energy loss) can be realized at the same time.

[0028]

EXAMPLES Next, the method of the present invention will be described in more detail by way of examples. However, these examples are for explaining the method of the present invention and for demonstrating the effect, and the scope of the present invention is not limited by these examples.

[0029]

[Example 1] Carbon fiber ("Torayca T-30" manufactured by Toray Industries, Inc.)
0 ": 3000 filaments) plain weave woven fabric (unit weight: 198 g / m ² ; 80 mm width) 3 plies and polycarbonate film (L-1225 type: 160 μm thick) 4 plies by the contact method shown in FIG. An aluminum rod was used as an electrode, and an alternating current was connected via a slidac. On the other hand, an aluminum plate backed up by a heat insulating layer made of an asbestos sheet and the surface of which was coated with a fluororesin was set as a mold for molding in a mold clamping machine.

The composite material component consisting of the above-mentioned carbon fiber woven fabric and polycarbonate film was sandwiched between molding dies and set in a mold clamping machine, and a pressure of 30 kgf / cm ² was applied. In this state, the voltage of the slidac was raised and an electric current was applied to the carbon fiber to heat the carbon fiber. The current required in the temperature raising step was about 47 amps at a voltage of 19 volts.

Further, while controlling the voltage, the temperature was raised to a predetermined temperature, that is, 300 ° C., and the temperature was maintained for 2.5 minutes. When the temperature became sufficiently lower than the glass transition temperature (Tg) of the polymer, the pressure was stopped and the molding die was opened to obtain a carbon fiber / polycarbonate-based composite material molded article in which the polymer was well impregnated.

1 from the obtained molded product (thickness 0.64 mm)
2.5 mm x 60 mm test piece (volume fiber content (Vf):
54%) was cut out, and the bending characteristics were measured according to JIS standard. The bending strength was 72 kgf / mm ^2, which was extremely excellent, indicating that the interfacial adhesion between the carbon fiber and the polymer was good.

[0033]

COMPARATIVE EXAMPLE 1 A carbon fiber woven fabric and a polycarbonate film having the same constitution as used in Example 1 were covered with a "Kapton" film having a release agent applied on the surface thereof, and set in a usual hot press machine. . Then heat press 310
The temperature was raised to 0 ° C., a pressure of 30 kgf / cm ² was applied, and the temperature was maintained for 30 minutes to impregnate the polymer. further,
The heater of the hot press was turned off and cooled to a temperature of Tg or lower, and then taken out from the molding die to obtain a composite material molded product.
The time required during this period was 45 minutes or more, which was about 10 times longer than the time required for Example 1 of 5 minutes or less.

[0034]

Example 2 Carbon fiber ("Torayca-300": 3000)
Plain woven fabric made of filaments (weight: 198g)
/ M ² ; 150 mm width) 6 plies and woven fabric made of polyetheretherketone fiber (Basis weight: 100 g / m ² ).
Nine plies were laminated, an electrode was connected to the carbon fiber by the same method as in Example 1, and the polymer temperature was raised to 410 ° C. by applying electricity to the carbon fiber while applying a pressure of 60 kgf / cm ² . The current required to raise the temperature was about 90 amps at a voltage of 15 volts. The temperature was maintained for 2 minutes to impregnate the carbon fiber with the polymer, and then the current was stopped by cooling to obtain a carbon fiber / polyetheretherketone-based composite material molded article in a good impregnated state.

From the obtained molded product (0.9 mm thickness), 1
A 2.5 mm × 60 mm test piece was cut out and the bending characteristics were measured according to JIS standards. The bending strength was 78 kgf / mm ^2, which was a good result. In addition, the time required from the temperature rise to the removal of the molded product in the above molding operation was an extremely short time of about 5 minutes.

[0036]

[Example 3] A carbon fiber woven fabric having the same structure as that used in Example 1 was cut into a width of 50 mm, and 10 plies thereof were laminated with 6 polycarbonate plies of the same type as used in Example 1. Then, in the same manner as in Example 1, it was placed in a molding die having an electric insulating layer and a heat insulating layer, and 38 kgf / cm.
A pressure of ² was applied, and the carbon fiber was energized to generate heat and impregnated with the polycarbonate. In this example, the time required from temperature increase to cooling was about 8 minutes, including the time of holding at 300 ° C. for 2 minutes, which was extremely short.

The thickness of the obtained carbon fiber / polycarbonate-based molded product was 1.9 mm, and the volume content of carbon fiber (V
f) was 61%. Further, a test piece was cut out from the molded product and the bending characteristics were measured. As a result, the bending strength was 92.
It was extremely good at kgf / mm ² . In addition, in the scanning electron micrograph of the molded product, no microvoid was observed between the layers.

[0038]

[Comparative Example 2] A laminated product of carbon fiber woven fabric and polycarbonate film having the same structure as in Example 3 was sandwiched from the upper and lower sides by using copper foil as an electrode, and set in a molding die via an electric insulating layer, and a mold clamping machine. Pressurized with. Then, electricity was applied to the copper foil electrode, and an attempt was made to generate heat by utilizing the electrical conductivity associated with the contact of the carbon fiber woven cloth. It took about 20 minutes to reach a predetermined temperature. After that, the energization was stopped and the product was taken out after cooling.

The copper foil (electrode) attached to the surface of the molded product was removed by etching, a test piece was cut out, and a bending test was carried out in the same manner as in Example 3. Bending strength is 73kgf / mm
It was a slightly low value of ² . When a scanning electron micrograph of the molded product was observed, some microvoids were observed in the central portion between the layers, and it was speculated that the impregnation of the polymer was insufficient.

[0040]

[Example 4] "UD / CF / PC knit fabric" in which unidirectionally aligned carbon fibers (CF: "Torayca T-300", 3000 filaments) were used as warp threads and polycarbonate (PC) fibers were used as knitting threads. (Total basis weight: 240 g / m ² , CF / PC capacity ratio = 58/4
2) was used as a composite material component and was energized and heated by an electrode connection method as shown in FIG.

The total time from the start of temperature increase to the holding at 300 ° C. for 2 minutes to the cooling was about 8 minutes, which was an extremely short time. The bending strength of the obtained UD-reinforced carbon fiber / polycarbonate-based composite material molded product is 184 kgf / mm.
² , the flexural modulus was 11,700 kgf / mm ² , which was extremely good.

[0042]

[Example 5] A plain weave fabric (weight per unit area: 160 g / weight) was obtained by using the carbon fibers used in Example 3 as warp yarns and fibers obtained from polyether ether ketone (PEEK) as weft yarns.
m ² ; 200 mm width) was woven.

The mixed woven fabric is sandwiched between a pair of rolls having an insulating layer and a strip-shaped surface electrode on the surface as shown in FIG.
A current was passed between the upper and lower strip electrodes to energize the carbon fiber / PEEK fiber woven product. Due to this heat generation by energization, the PEEK fiber used as the weft is melted and impregnated between the carbon fibers,
A desired laminated molded product was obtained.

The carbon fibers of the obtained molded product were substantially aligned in one direction, and the bending strength of the test piece taken out from the mold for cooling after cutting was 178 kgf / mm ² , which was extremely good. there were.

[0045]

[Example 6] Two plies of the carbon fiber woven fabric used in Example 1 and a plain woven fabric made of nylon-6 fiber (weight: 10
0 g / m ² ) 4 plies were cut into 200 mm square and laminated to obtain a composite material component. Then, 20 mm ends of the upper and lower outermost nylon woven fabrics were cut and set so that the carbon fiber woven fabrics were in direct contact with the upper and lower planar electrodes of the electrode connection system shown in FIG.

Further, after pressurizing with a mold clamping machine so as to have a pressure of 16 kgf / cm ² through a molding die, an electric current was passed through the electrodes to heat the carbon fibers. Due to this heat generation, the nylon fiber woven fabric was melted and impregnated into the carbon fiber. Two
After holding at 70 ° C. for 2 minutes, the current was stopped and the product was cooled, and the molded product was taken out from the mold for molding.

The carbon fiber / nylon type molded product thus obtained is
The bending strength was 69 kgf / mm ² . That is, by the method of the present invention, a composite material molded article having excellent physical properties could be obtained in an extremely short time.

[0048]

Example 7 A polycarbonate fiber woven fabric and a carbon fiber blade (braid) were placed on a pipe-shaped mandrel (outer diameter 8 mm) having a taper angle of 1 ° having an electrically insulating coating layer and strip electrodes as shown in FIG. , Polycarbonate fiber woven fabric, carbon fiber UD / fabric, polycarbonate fiber woven fabric, carbon fiber braid, and polycarbonate fiber woven fabric were stacked in this order, covered with a bisecting cylindrical molding die, and tightened from the outside.

Then, as shown in FIG. 4, an electric current is passed through the carbon fibers through the two electrodes to generate heat, and in the softened state of the polycarbonate, nitrogen gas is introduced into the pipe-shaped mandrel at a pressure of 5 kgf / cm ² gauge pressure. And held for 5 minutes. After cooling, the mold was opened and pulled out from the mandrel with a taper to obtain a desired pipe-shaped carbon fiber / polycarbonate-based composite material molded product.

[0050]

Example 8 The carbon fiber woven fabric used in Example 1 (weight:
198 g / m ² ) 3 ply and woven fabric obtained from polyphenylene sulfide (PPS) fiber (Basis weight: 120
g / m ² ) 4 plies were alternately laminated and set in a mold clamping machine with an electric insulating layer by the electrode connecting method similar to that in Example 1. Next, an electric current was applied to the carbon fiber through the bar-shaped electrode to generate heat, and the PPS polymer was melt-impregnated. The current required for heat generation and impregnation was 55 amperes at 22 volts. After holding at 320 ° C. for 2 minutes, the power supply was stopped and the mixture was cooled and taken out from the mold for molding to obtain a carbon fiber / polyphenylene sulfide-based composite material molded product having good impregnation property.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a process of the present invention. An example in which a bar-shaped electrode is brought into contact with carbon fibers will be shown.

FIG. 2 is a schematic view showing another example of the process of the present invention. An example in which a flat surface-shaped electrode is brought into contact with carbon fibers will be shown.

FIG. 3 is a schematic view showing another example of the process of the present invention. An example in which a dot electrode is brought into contact with carbon fiber will be shown.

FIG. 4 is a schematic view showing an example of manufacturing a cylindrical molded product by the process of the present invention. An example in which a planar electrode having a curved surface is brought into contact with the carbon fiber will be shown.

FIG. 5 is a schematic view showing an example of producing a continuous sheet-shaped molded product by the process of the present invention. An example in which an electrode provided on a part of the peripheral surface of the pair of nip rolls is brought into contact with the carbon fiber will be shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Composite material component 2 Electrical insulating material 3 Heat insulating material 4 Type material 5 Bar-shaped electrode 6, 6a, 6b Planar electrode 7 Point electrode 8 Roll 9 Mandrel

Claims (4)

(57) [Claims] 1. A reinforcing material containing carbon fiber as a main component ,
Upon manufacturing a composite molded article and a thermoplastic polymer, and said reinforcing material and said thermoplastic polymer is insulated via an electrically insulating material between the mold surface for molding, along the surface direction of the reinforcing material An electric current is applied to the carbon fibers in the reinforcing material to generate heat, and the thermoplastic polymer is softened or melted by the heat and impregnated in the reinforcing material to obtain a composite material molded article, A method for producing a molded product of a thermoplastic polymer composite material reinforced with carbon fiber. Wherein the carbon fibers are characterized and Turkey to heat by electric conduction of dc or ac method of producing a composite material molded article according to claim 1. 3. The method for producing a composite material molded product according to claim 1, wherein an outer portion of the molding die located in contact with the electrically insulating material is covered with a heat insulating material to suppress heat radiation. . 4. A step of obtaining a composite material molded article by passing an electric current through the carbon fiber to generate heat and softening or melting the thermoplastic polymer by the heat to impregnate the carbon fiber into a reinforcing material containing the carbon fiber as a main component to obtain a composite material molded article. 4. The method for producing a composite material molded article according to claim 1, wherein the molding die is pressed during or before and after energization.