JP2008044999A - Process for producing prepreg excellent in uniformity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high productivity process for providing a prepreg excellent in uniformity which is composed of a sheet-like reinforcing fibrous material and a thermoplastic resin with which the sheet-like reinforcing fibrous material is impregnated. <P>SOLUTION: The process for producing a prepreg by impregnating a sheet-like reinforcing fibrous material with a thermoplastic resin comprises dipping the sheet-like reinforcing fibrous material in a suspension obtained by dispersing a thermoplastic resin powder in one or more solvents or a mixed solvent selected from water, alcohols, ketones, and halogenated hydrocarbons to allow the resin powder to attach to this reinforcing fibrous material, next, heating and drying this reinforcing fibrous material by the system of bringing it into contact with a hot roll until the content of the solvent or mixed solvent comes to 10 wt.% or less, and thereafter heating the dried reinforcing fibrous material at 170-390°C, and melting the resin powder to integrate the sheet-like reinforcing fibrous material with the thermoplastic resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for producing a prepreg excellent in uniformity from a sheet-like reinforcing fiber material and a thermoplastic resin impregnated therein.

In recent years, reinforcing fiber materials such as carbon fibers, glass fibers, and aramid fibers have been combined with various matrix resins, and the resulting reinforcing fiber composite materials have been widely used in various fields and applications. And in the aerospace field and general industrial fields where high mechanical properties and heat resistance are required, conventionally, thermosetting resins such as unsaturated polyester resin, epoxy resin, and polyimide resin have been used as matrix resins. It has been. However, especially in the aerospace field, these matrix resins have the drawbacks of being brittle and inferior in impact resistance, and therefore, improvement has been demanded. Further, in the case of a thermosetting resin, when this is used as a prepreg, there are problems in the storage management of the prepreg due to the life of the resin, and problems such as a long molding time and low productivity.

On the other hand, in the case of a thermoplastic resin prepreg, the impact resistance when made into a composite material is excellent, the storage management of the prepreg is easy, the molding time is short, and the molding cost may be reduced. Conventional methods for producing a thermoplastic resin prepreg include, for example, a method in which a film-like resin is heated and melted to impregnate a reinforcing fiber material (melting impregnation method), and a powdery resin is reinforced by a fluidized bed method or a suspension method. A method of applying and fusing to a fiber material (powder method) and a method of making a resin into a solution and removing the solvent after impregnating the reinforcing fiber material (solution impregnation method) are known. However, the melt impregnation method has a high melt viscosity of the resin, so it is difficult to uniformly impregnate the resin into the inside of the fiber material. In the powder method, it is difficult to adjust the amount of the resin adhered, and the solution impregnation method However, there are problems and drawbacks in that the types of resins and solvents that can be used are limited.

As a method for producing a prepreg with improved prior art, a thermoplastic resin powder is dispersed in an organic solvent such as alcohol or a mixed solvent of an organic solvent and water to form a suspension, and a strand or sheet of carbon fiber is immersed in the suspension. A method has been proposed in which resin powder is attached to a strand or sheet and then heated to melt the resin so that the thermoplastic resin and the carbon fiber strand or sheet are integrated (see Patent Document 1). According to this method, a prepreg in which the resin is impregnated relatively uniformly (variation value of impregnated resin amount is 4.2 to 5.0) can be obtained. It is exemplified that 2.8 to 3.8 were also obtained. However, as a recent material in the field of aerospace, in particular, a prepreg having further excellent uniformity and the like has been demanded, and its manufacturing method needs to be as simple as possible.
Japanese Patent Publication No. 4-12894

The present inventor also produced a prepreg by impregnating a sheet-like reinforcing fiber material with a thermoplastic resin. One or two thermoplastic resin powders selected from alcohols, ketones and halogenated carbons were used. Using the above organic solvent or a suspension dispersed in a mixed solvent of such an organic solvent and water, a method for producing a prepreg excellent in uniformity and surface smoothness by adopting specific processing conditions was proposed. (Refer patent documents 2-3). However, in the proposed method, although the performance of the obtained prepreg is excellent, there is a problem that productivity is not necessarily high.
JP 2005-238596 A Japanese Patent Laid-Open No. 2005-239843

An object of the present invention is to provide a prepreg excellent in uniformity with few voids and little variation in thickness, comprising a sheet-like reinforcing fiber material and a thermoplastic resin impregnated therein. It is to provide a high manufacturing method.

In the present invention, when a prepreg is produced by impregnating a sheet-like reinforcing fiber material with a thermoplastic resin, the thermoplastic resin powder is selected from water, alcohols, ketones, and halogenated carbons. A sheet-like reinforcing fiber material is immersed in a suspension dispersed in a solvent of at least one kind or a mixed solvent so that the suspension containing the resin powder is attached to the reinforcing fiber material, and then the reinforcing fiber material is brought into contact with a hot roll. And heating and drying until the content of the solvent or mixed solvent is 10 wt% or less, preferably 5 wt% or less, and then heating the dried reinforcing fiber material to 170 to 390 ° C to melt the resin powder And a sheet-like reinforcing fiber material and a thermoplastic resin are integrated, and a method for producing a prepreg having excellent uniformity.

According to the present invention, a prepreg obtained by impregnating a thermoplastic resin into a sheet-like reinforcing fiber material can be produced with high production efficiency. The obtained prepreg can be molded into a reinforced fiber composite material for various uses by using this, and the physical properties such as mechanical properties and heat resistance of the obtained composite material are extremely high because the prepreg has high uniformity. It will be excellent.

The present invention relates to a sheet-like reinforcing fiber material in a suspension in which a thermoplastic resin powder is dispersed in one or more solvents or mixed solvents selected from water, alcohols, ketones, and halogenated carbons. The suspension containing resin powder is adhered to the reinforcing fiber material.

In the present invention, the sheet-like reinforcing fiber material means that the fiber materials are arranged in a sheet shape in one direction, these are laminated, for example, orthogonally, and the fiber material is formed into a fabric such as a woven fabric, a knitted fabric or a non-woven fabric. All strands such as braids and braids are included. As the reinforcing fiber material, there are fiber materials made of inorganic fibers, organic fibers, metal fibers, or a mixture thereof. Specifically, 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, polyamide fibers, and polyester fibers. Preference is given to carbon fibers and aramid fibers.

The thermoplastic resin used in the present invention is not particularly limited, but a crystalline or amorphous thermoplastic resin having a melting point or glass transition temperature of 150 ° C. or higher is preferable. Specific examples of preferred resins are polypropylene, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, aromatic or aliphatic polyamide, aromatic polyester, aromatic polycarbonate, polyetherimide, polyarylene oxide, thermoplastic polyimide. Polyamideimide. Two or more of these resins may be used in combination. For aircraft prepregs, polyetherimide (PEI) or polyimide (PI) is particularly preferred.

In the present invention, the resin powder has a particle diameter of 50 μm or less in consideration of good adhesion to the reinforcing fiber material (a state in which the resin powder is held between fibers or on the fiber surface). It is good that it is not less than 1 μm, and an average particle size in the range of 5 to 20 μm is preferable. The thermoplastic resin powder having a particle size distribution in the above range is stable in dispersion (dispersion of the resin powder in the suspension bath) when dispersed in a dispersion medium described later, and can be used for long-term production. The resin powder can be stably attached to the fiber material.

In the present invention, the content of the solvent or the mixed solvent is obtained by immersing the sheet-like reinforcing fiber material in the dispersion, allowing the resin powder to adhere to the reinforcing fiber material, and then bringing the reinforcing fiber material into contact with a hot roll. Is 10% by weight (based on the total weight of the reinforcing fiber material and the solvent or mixed solvent) or less, preferably 5% by weight or less, and then the dried reinforcing fiber material is 170 to 390 ° C. And the resin powder is melted to integrate the sheet-like reinforcing fiber material and the thermoplastic resin.

The present invention is characterized in that a method of contacting with a hot roll is adopted as a method and means for heating and drying until the content of the solvent or mixed solvent becomes 10% by weight or less. As a method / means for impregnating the solvent and drying the wet sheet-like reinforcing fiber material, a hot-air dryer, a far-infrared dryer, an electrothermal dryer, or the like is usually used. However, it is difficult to reduce the solvent content to 10% by weight or less by such ordinary methods and means, and there is a problem that the productivity of the drying process is low (the drying speed is slow). Moreover, it is difficult to control the temperature with a far-infrared dryer, and there is a problem that the powder rises with a hot-air dryer.

On the other hand, when the method of contacting with a hot roll as in the present invention is used, powder scattering is avoided, the drying speed and efficiency are high, and the content of the solvent or mixed solvent can be easily reduced to 10% by weight or less. As a result, the resin can be prevented from being hydrolyzed and deteriorated in the subsequent melting step of the resin powder. The heating means for the heat roll may be any of electric heating or heating with steam. In addition, the number and arrangement of the heat rolls can be arbitrarily set as necessary, but the solvent or the mixed solvent content is set to 10% by weight or less at a drying speed of 1 to 10 m / min. Is preferred.

After drying, the dried reinforcing fiber material is heated to 170 to 390 ° C., preferably 200 to 300 ° C., to melt the resin powder to integrate the sheet-like reinforcing fiber material and the thermoplastic resin. Using a pair of upper and lower heating / pressurizing rollers, the roller pressure is 3 to 10 kg / cm (calculated linear pressure), the roller temperature (Tg + 15) to (Tg + 100) ° C. is heated to impregnate the resin, and the sheet-like reinforcing fiber material It is preferable to fully integrate the resin and the thermoplastic resin.

An example of the production method of the present invention will be described with reference to FIG. In FIG. 1, a sheet-like reinforcing fiber material 1 is introduced through a guide roller 3 into a suspension bath 2 in which a thermoplastic resin powder is dispersed in a dispersion medium. The resin powder adheres to the reinforcing fiber material 1 while the reinforcing fiber material 1 passes through the suspension bath 2. Next, the reinforcing fiber material 1 taken out from the suspension bath 2 is introduced into a dryer 4 and dried by removing the dispersion medium. Subsequently, the reinforcing fiber material 1 is heated to such an extent that the resin is melted in the heating zone 5 and is simultaneously guided to a pair of upper and lower heating / pressure rollers 6, and a roller pressure of 3 to 10 kg / cm (calculated linear pressure) and a roller temperature. Heating and pressing are performed at (Tg + 15) to (Tg + 100) ° C. The resin powder adhering to the reinforcing fiber material 1 by such operation is melted and impregnated between the fiber material surface and the fibers. Next, the reinforcing fiber material is wound around the take-up roller 8 via the take-up roller 7.

In the present invention, the reinforcing fiber material is heated and dried by the dryer 4 until the content of the solvent or the mixed solvent becomes 10% by weight or less in a manner of contacting with the hot roll. In addition to the arrangement shown in FIG. 1, the heat rolls may have, for example, the number and arrangement shown in FIG. 2 or FIG. 3. The heating / drying temperature is a temperature at which the thermoplastic resin does not decompose or react. Generally, 1 to 20 minutes at 80 to 200 ° C is sufficient. A drying speed of 1 to 10 m / min is appropriate.

The dispersion medium for dispersing the thermoplastic resin used in the present invention is one or two or more solvents or mixed solvents selected from water, alcohols, ketones, and halogenated carbons. Examples of alcohols include methanol, ethanol, isopropyl alcohol, and methyl cellosolve. Examples of ketones include acetone and methyl ethyl ketone. Examples of halogenated hydrocarbons include methylene chloride and dichloroethane. Of these, ethanol, isopropyl alcohol, acetone, a mixed solvent thereof with water, or water is preferable. Such a dispersion medium also has an effect of appropriately opening the fiber material when the sheet-like reinforcing fiber material is immersed, so that it is effective for the resin powder in the suspension to uniformly adhere to the fiber material.

The combination of the thermoplastic resin and the dispersion medium (solvent) for dispersing the thermoplastic resin must not dissolve in the solvent, and the resin must swell or not dissolve in the solvent. is there.

The concentration of the thermoplastic resin in the suspension ((thermoplastic resin weight / dispersion medium weight + thermoplastic resin weight) × 100) is 1 to 50% by weight, preferably 1 to 30% by weight, more preferably 5 to 15% by weight. %. In the present invention, the content of the thermoplastic resin in the prepreg is suitably 10 to 70% by weight, preferably 20 to 50% by weight.

The temperature of the suspension when immersing the sheet-like reinforcing fiber material is not particularly limited as long as the dispersion state of the resin is kept good, and varies depending on the type and concentration of the thermoplastic resin and dispersion medium used. Usually, it is 5-50 degreeC, Preferably it is 5-30 degreeC, More preferably, it is 15-30 degreeC. The immersion time depends on the amount of the thermoplastic resin attached, but usually 5 to 180 seconds is sufficient.

In the present invention, in order to further improve the uniformity of the adhesion of the resin powder, an energization process using a direct current may be performed between the fiber material and the suspension bath when the sheet-like reinforcing fiber material is immersed. For example, an electrode roller outside the bath in contact with the fiber material is used as the anode, a cathode is provided in the suspension bath, and the current density is 0.001 to 5 A / m ² per unit surface area of the fiber material in the bath. Energize.

Next, the dried reinforcing fiber material is heated in the heating zone 4 to such an extent that the resin melts. Heating can be performed by passing between rollers heated to 170 to 390 ° C. or between slits, or passing through an atmosphere of such a temperature. The resin adhered by such treatment is melted.

In the present invention, the reinforcing fiber material is then subjected to a roller pressure of 3 to 10 kg / cm (calculated linear pressure) using a pair of upper and lower heating rollers, preferably 5 to 10 kg / cm, and a roller temperature (Tg + 15) to (Tg + 100). A prepreg is manufactured by heating at ℃, preferably (Tg + 20) to (Tg + 80) ℃, impregnating the resin, and integrating the sheet-like reinforcing fiber material and the thermoplastic resin. By this treatment, the prepreg is made uniform and the surface is smoothed.

In the present invention, in order to further enhance the adhesive force between the sheet-like reinforcing fiber material and the thermoplastic resin, when a fiber sizing agent, an oil agent, a glue, etc. are attached to the sheet-like reinforcing fiber material, It is desirable to remove these in advance. If necessary, the fiber material may be opened in advance, or may be subjected to surface treatment with electrolysis or chemicals.

Hereinafter, the present invention will be described with reference to specific examples. In each example and comparative example, the uniformity of the obtained prepreg was evaluated by relatively evaluating the void ratio indicating the quality of the resin impregnation into the sheet-like reinforcing fiber material, and by observing the cross section with a microscope. It was indicated by sufficiently smooth (（), considerably smooth (◯), and poor in smoothness (×). The void ratio was measured by the sulfuric acid decomposition method.

[Example 1]
Polyimide resin (PIXA-M manufactured by Mitsui Chemicals) powder (particle size distribution, 10%: 8 μm, 50%: 12 μm, 90%: 17 μm) was dispersed in acetone to prepare a 7% concentration suspension. In a suspension bath, 80 sheets of carbon fiber A (IM600 manufactured by Toho Tenax Co., Ltd., single fiber diameter: 5.0 μm, 12,000) were aligned in parallel, and a sheet with a CF basis weight adjusted to 145 g / m ² was immersed for 30 to 60 seconds. The amount of resin adhered was adjusted to 35 ± 3% by weight. Subsequently, the sheet was heated and dried by bringing it into contact with the hot roll shown in FIG. 1 at 150 ° C. for 1 minute. In this step, the solvent content was 3.0% by weight. Subsequently, it was heated to such an extent that the resin was melted through a roller having a surface temperature of 380 to 390 ° C. Next, an integrated reinforced carbon fiber prepreg was obtained by passing the resin between a pair of upper and lower rollers having a surface temperature of 250 ° C. at a pressure of 5 kgf / cm and sufficiently impregnating the carbon fiber material with the resin. The void ratio and internal resin impregnation property of the obtained prepreg were as shown in Table 1.

[Comparative Example 1]
A prepreg was obtained under the same conditions as in Example 1 except that no heat roll was used. The void ratio and internal resin impregnation property of the obtained prepreg were as shown in Table 1.

[Example 2]
PPS (polyphenylene sulfide, manufactured by Dainippon Ink) powder (average particle size: 10 μm) was used as the thermoplastic resin, and this was dispersed in acetone to prepare a 7% concentration suspension. In the suspension bath, the same sheet-like reinforcing fiber material as that of the carbon fiber A of Example 1 was immersed for 30 to 60 seconds, and the amount of the resin adhered was adjusted to 35 ± 3% by weight. Subsequently, the sheet was heated and dried by bringing it into contact with the hot roll shown in FIG. 1 at 150 ° C. for 1 minute. In this step, the solvent content was 3.5% by weight. Next, the resin was heated to such an extent that the resin was melted through a roller having a surface temperature of 330 to 350 ° C. Next, an integrated reinforced carbon fiber prepreg was obtained by passing between a pair of upper and lower rollers with a surface temperature of 130 ° C. at a pressure of 5 kgf / cm and completely impregnating the carbon fiber material with the resin. The void ratio and internal resin impregnation property of the obtained prepreg were as shown in Table 1.

[Comparative Example 2]
A prepreg was obtained under the same conditions as in Example 2 except that no heat roll was used. The void ratio and internal resin impregnation property of the obtained prepreg were as shown in Table 1.

From the results shown in Table 1, it can be seen that only when the drying with the heat roller of the present invention is sufficient, the void ratio and the internal resin impregnation property are sufficiently satisfied.

The prepreg excellent in uniformity and surface smoothness according to the present invention can be laminated, heated and pressurized again according to the purpose, and formed into a composite material having a substantially uniform structure. Since the obtained composite material has excellent mechanical properties such as impact resistance and excellent heat resistance, it is widely used in aerospace and general industrial fields.

It is the schematic which shows an example of the manufacturing process of the prepreg of this invention. It is a figure which shows an example of the contact system of the hot roll in the dryer in this invention. It is a figure which shows the other example of the contact system of the hot roll in the dryer in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reinforcing fiber material 2 Suspension bath 3 Guide roller 4 Dryer 5 Heating zone 6 A pair of heating and pressure rollers 7 Take-up roller 8 Take-up roller

Claims (8)

In the production of a prepreg by impregnating a sheet-like reinforcing fiber material with a thermoplastic resin, the thermoplastic resin powder is one or more solvents selected from water, alcohols, ketones and halogenated carbons. Alternatively, a sheet-like reinforcing fiber material is immersed in a suspension dispersed in a mixed solvent so that the suspension containing the resin powder is adhered to the reinforcing fiber material, and then the reinforcing fiber material is brought into contact with a hot roll, Alternatively, the mixture is heated and dried until the content of the mixed solvent becomes 10% by weight or less, and then the dried reinforcing fiber material is heated to 170 to 390 ° C. to melt the resin powder. A method for producing a prepreg having excellent uniformity, characterized in that a plastic resin is integrated. The method for producing a prepreg excellent in uniformity according to claim 1, wherein the solvent or the mixed solvent is heated and dried until the content of the solvent or the mixed solvent becomes 5% by weight or less. The reinforcing fiber material to which the resin powder is adhered and heated and dried is heated to 170 to 390 ° C. to melt the resin powder, or after being melted, using a pair of upper and lower heating / pressure rollers. The roller is heated and pressurized at a roller pressure of 3 to 10 kg / cm and a roller temperature (Tg + 15) to (Tg + 100) ° C., and the resin is melted and impregnated into a sheet-like reinforcing fiber material to be integrated. Or the manufacturing method of the prepreg excellent in the uniformity of 2 description. The average particle diameter of thermoplastic resin powder is 5-20 micrometers, The manufacturing method of the prepreg excellent in the uniformity of any one of Claims 1-3 characterized by the above-mentioned. The method for producing a prepreg excellent in uniformity according to any one of claims 1 to 4, wherein the concentration of the thermoplastic resin in the suspension is 1 to 50% by weight. The method for producing a prepreg excellent in uniformity according to any one of claims 1 to 5, wherein the content of the thermoplastic resin in the prepreg is 10 to 70% by weight. The prepreg excellent in uniformity according to any one of claims 1 to 6, wherein the thermoplastic resin is a crystalline or amorphous thermoplastic resin having a melting point or glass transition temperature of 150 ° C or higher. Manufacturing method. The group in which the thermoplastic resin is polypropylene, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, aromatic polycarbonate, polyetherimide, polyarylene oxide, thermoplastic polyimide, polyamideimide The method for producing a prepreg excellent in uniformity according to any one of claims 1 to 7, wherein the resin is one or more resins selected from the group consisting of:

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