JP2008044165A - Method for producing prepreg excellent in uniformity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a prepreg excellent in uniformity from a sheet-shaped reinforcing fibrous material and a thermoplastic resin. <P>SOLUTION: When a sheet made of the reinforcing fibrous material is immersed in a suspension bath in which the powdered thermoplastic resin is dispersed in a solvent or a mixed solvent comprising water, an alcohol, and a ketone or a halogenated carbon, the powdered resin is adhered to the sheet, the sheet is taken out from the bath, the powdered resin is melted, and the resin is integrated with the fibrous material to produce the prepreg excellent in uniformity, (1) a plurality of the sheets are introduced into the bath through introduction rollers respectively to be immersed, (2) the sheets are laminated to be taken out from the bath in the form of a laminated sheet, (3) while the sheet is immersed in the bath, the suspension is ejected on the surface of the sheet and between the laminated layers from a spray nozzle set in the bath, and (4) the laminated sheet taken out from the bath is heated at 170-390°C to melt the powdered resin. In this way, the method for producing the prepreg is composed. <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, the performance of the obtained prepreg is excellent, but there is room for further improvement in that the resin powder is uniformly adhered to the reinforcing fiber material in the suspension bath containing the resin powder. was there.
JP 2005-238596 A Japanese Patent Laid-Open No. 2005-239843

An object of the present invention is to provide a method for stably producing a prepreg excellent in uniformity having few voids and little variation in thickness, comprising a sheet-like reinforcing fiber material and a thermoplastic resin impregnated therein. Is to provide.

The present invention comprises a reinforcing fiber material in a suspension bath in which a thermoplastic resin powder is dispersed in one or more solvents or mixed solvents selected from water, alcohols, ketones, and halogenated carbons. Immerse the sheet, let the resin powder adhere to the sheet, then take the sheet with the resin powder attached out of the bath, heat the sheet to melt the resin powder, and integrate the reinforced fiber material and the thermoplastic resin uniformly When producing prepregs with excellent properties,
(1) Introducing and immersing a plurality of sheets in a suspension bath through an introduction roller,
(2) Laminating a plurality of sheets and deriving from a suspension bath via a take-up roller as a single laminated sheet;
(3) While a plurality of sheets are immersed in the suspension bath, the suspension is sprayed between the surface and the layer of the sheet from the spray nozzle installed in the bath,
(4) heating the laminated sheet derived from the suspension bath to 170-390 ° C. to melt the resin powder;
This is a method for producing a prepreg having excellent uniformity, characterized in that (Invention of Claim 1).

According to the present invention, a prepreg obtained by impregnating a thermoplastic resin into a sheet-like reinforcing fiber material can be produced stably and efficiently. 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 comprises a reinforcing fiber material in a suspension bath 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 sheet is immersed and the resin powder is adhered to the sheet. (1) Each of the plurality of sheets is introduced and immersed in a suspension bath through an introduction roller. (2) Thereafter, the plurality of sheets are laminated. And is drawn out from the suspension bath through a take-off roller as a single laminated sheet, and (3) a sheet from a spray nozzle installed in the bath while the plurality of sheets are immersed in the suspension bath. Suspension is jetted between the surface and the interlayer.

An example of the step of attaching the resin powder to the sheet made of the reinforcing fiber material in the present invention will be described with reference to the drawings. In FIG. 1, 1 is a suspension bath, 2a and 2b are sheets made of reinforcing fiber material, 3a and 3b are both sheet introduction rollers, 4 is a take-up roller for laminated sheets, 5a to 5e are guide rollers, 6a, 6b and 6c. Are jet nozzles, and 7 is a laminated sheet.

Sheets 2a and 2b made of a reinforcing fiber material are introduced and immersed in the suspension bath 1 through introduction rollers 3a and 3b, respectively. Even if the resin powder in the suspension bath adheres to the sheet as it is, in the present invention, while the sheet is immersed in the suspension bath, from the injection nozzles 6a to 6c installed in the bath, the surface of the sheet and A suspension is jetted between the layers. By spraying the suspension in this way, the resin powder is sufficiently adhered to the sheet surface, and when a plurality of such sheets are laminated to form a single laminated sheet 7, the resin is localized or unevenly distributed between the layers of each sheet. It becomes a state. And when this laminated sheet 7 is passed through the heating / melting step described later, the resin is uniformly impregnated throughout the sheet, and a prepreg excellent in uniformity can be obtained.

In addition, in FIG. 1, although the example using two sheets which consist of a reinforced fiber material was shown, by increasing the introduction roller, one laminated sheet using three sheets, four sheets or more sheets Can also be created. Further, as long as the guide rollers are arranged so that each sheet can be sufficiently immersed in the suspension bath, the number and arrangement position thereof are not limited. Further, the number and installation positions of the injection nozzles installed in the bath are not particularly limited as long as the suspension can be sufficiently injected between the surface and the layer of the sheet, but usually 2 to 10 nozzles are installed. preferable.

In the present invention, a sheet made of a reinforcing fiber material is a sheet in which fiber materials are aligned in one direction, a sheet in which these are laminated orthogonally, and a fiber material is formed into a fabric such as a woven fabric, a knitted fabric, or a nonwoven fabric. All strands such as braids and braids are included, but those in which strand-like fiber materials are arranged in a sheet in one direction are preferable. 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 (Invention of Claim 6). 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 (Invention of Claim 7). 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). The average particle size is preferably within the range of 5 to 20 μm, preferably not less than 1 μm (Invention of claim 3). The thermoplastic resin powder having a particle size within the range of the present invention has a stable dispersibility (dispersion of resin powder in the suspension bath) when dispersed in a dispersion medium described later, and is a fiber material even in long-term production. Is characterized in that the resin powder can be stably attached.

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 (invention of claim 4), preferably 1 to 30% by weight, More preferably, it is 5 to 15% 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, while a plurality of sheets are immersed in the suspension bath, the suspension is sprayed between the surface and the layer of the sheet from the spray nozzle installed in the bath. As long as the suspension is jetted between the surface and the interlayer of the sheet, the shape, position and number of the jet nozzles are not particularly limited. There are no particular restrictions on the spraying conditions, and the suspension may be spread evenly between the sheet surface and the layers.

Under the above conditions, the sheet-like reinforcing fiber material usually has a thermoplastic resin powder of 10 to 70% by weight (based on the total amount of the fiber material and the thermoplastic resin) (invention of claim 5). However, it is preferably 20 to 50% by weight in the production of the prepreg.

In FIG. 1, a laminated sheet 7 made of a reinforcing fiber material led out from a suspension bath 1 through a take-up roller 4 is usually dried by introducing it into a dryer (not shown) and removing the dispersion medium. Drying conditions and methods are not particularly limited, but are usually dried at a temperature at which the thermoplastic resin does not decompose or react. Generally, it is dried at 80 to 200 ° C. for 1 to 20 minutes.

Next, the laminated sheet made of the reinforcing fiber material is heated at 170 to 390 ° C. to such an extent that the resin powder adhered to the sheet is melted, and the reinforcing fiber material and the thermoplastic resin are integrated.

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.

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 of the examples and comparative examples, the uniformity of the obtained prepreg was relatively evaluated by evaluating the relative void ratio and the cross-sectional observation using a microscope, which indicate the quality of the resin impregnation into the sheet-like reinforcing fiber material. Are shown as smooth (◎), fairly smooth (◯), and inferior in smoothness (×). The void ratio was measured by the sulfuric acid decomposition method.

[Example 1]
Polyetheretherketone resin (PEEK manufactured by Victrex) powder (particle size distribution, 10%: 8 μm, 50%: 12 μm, 90%: 17 μm) was dispersed in acetone to prepare a 7% concentration suspension. Forty carbon fibers A (HTA manufactured by Toho Tenax Co., Ltd., single fiber diameter: 5.0 μm, 12,000) were arranged in parallel to make a sheet, and the basis weight of the carbon fiber of the sheet was adjusted to 145 g / m ² . Then, the sheet is divided into two sheets, and the two sheets are introduced into the suspension bath by the apparatus and operation as shown in FIG. 1 and immersed in the suspension bath for about 30 seconds. %, And a single laminated sheet was derived from the splash bath. Subsequently, the obtained laminated sheet was dried at 150 ° C. for 1 to 5 minutes, and passed through a roller having a surface temperature of 380 to 390 ° C. to melt and impregnate the resin. The void ratio and microscopic observation results 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 one sheet was used. In this comparative example, since the resin was not sufficiently impregnated, the uniformity was not satisfied. The void ratio and microscopic observation results 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, two sheets of the same reinforcing fiber material as the carbon fiber of Example 1 were used and immersed for about 30 seconds in the same manner as in Example 1 so that the amount of resin adhered was 35 ± 3% by weight. It adjusted so that it might become, and it derived | led-out from the splash bath as one laminated sheet. Subsequently, drying was performed at 150 ° C. for 1 to 5 minutes, and the resin was melted and impregnated through a roller having a surface temperature of 330 to 350 ° C. The void ratio and microscopic observation results of the obtained prepreg were as shown in Table 1.

[Comparative Example 2]
One sheet was used without dividing the sheet, and a prepreg was obtained under the same conditions as in Example 2 except that. In this comparative example, since the resin was not sufficiently impregnated, the uniformity was not satisfied. The void ratio and microscopic observation results of the obtained prepreg were as shown in Table 1.

[Example 3]
Polypropylene (PP) resin (manufactured by Idemitsu Petrochemical) powder (average particle size 13 μm) was dispersed in acetone to prepare a 7% concentration suspension. A reinforcing fiber material (three sheets) in the same sheet form as the carbon fiber of Example 1 is immersed for about 30 seconds and adjusted so that the amount of resin attached becomes 30 ± 3% by weight, and a spun bath as one laminated sheet Derived from Subsequently, it was dried at 150 ° C. for 1 to 5 minutes, passed through a roller having a surface temperature of 170 to 180 ° C., and the resin was melted and impregnated. The void ratio and microscopic observation results of the obtained prepreg were as shown in Table 1.

[Comparative Example 3]
A prepreg was obtained under the same conditions as in Example 3 except that the sheet was divided into one sheet. In this comparative example, since the resin was not sufficiently impregnated, the uniformity was not satisfied. The void ratio and microscopic observation results of the obtained prepreg were as shown in Table 1.

From the results in Table 1, it can be seen that only when the conditions are divided into a plurality of sheets according to the present invention, the resin sufficiently impregnated with respect to the void ratio and the internal state is obtained.

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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Suspension bath 2a, 2b Sheet | seat 3a, 3b which consists of a reinforced fiber material Introductory roller 4 Take-out roller 5a-5e Guide roller 6a, 6b, 6c Injection nozzle 7 Laminated sheet

Claims (7)

A sheet made of a reinforcing fiber material is immersed in a suspension bath in which a thermoplastic resin powder is dispersed in one or two or more solvents or mixed solvents selected from water, alcohols, ketones, and halogenated carbons. The resin powder is adhered to the sheet, and then the sheet with the resin powder adhered is taken out of the bath, the sheet is heated to melt the resin powder, and the reinforcing fiber material and the thermoplastic resin are integrated to provide excellent uniformity. When manufacturing prepreg,
(1) Introducing and immersing a plurality of sheets in a suspension bath through an introduction roller,
(2) Laminating a plurality of sheets and deriving from a suspension bath via a take-up roller as a single laminated sheet;
(3) While a plurality of sheets are immersed in the suspension bath, the suspension is sprayed between the surface and the layer of the sheet from the spray nozzle installed in the bath;
(4) heating the laminated sheet derived from the suspension bath to 170-390 ° C. to melt the resin powder;
A method for producing a prepreg with excellent uniformity characterized by After heating the sheet to which the resin powder is adhered to melt the resin powder, using a pair of upper and lower heating / pressure rollers, the roller pressure is 3 to 10 kg / cm and the roller temperature (Tg + 15) to (Tg + 100) ° C. The method for producing a prepreg excellent in uniformity according to claim 1, wherein the sheet is heated and pressurized. The method for producing a prepreg excellent in uniformity according to claim 1 or 2, wherein the thermoplastic resin powder has an average particle size of 5 to 20 µm. The method for producing a prepreg excellent in uniformity according to any one of claims 1 to 3, 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 4, 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 5, 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 thermoplastic resin is polypropylene, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, aromatic or aliphatic polyamide, aromatic polyester, aromatic polycarbonate, polyetherimide, polyarylene oxide, thermoplastic polyimide, polyamide The method for producing a prepreg excellent in uniformity according to any one of claims 1 to 6, wherein the prepreg is one or more resins selected from the group consisting of imides.

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