JP3303442B2 - Prepreg - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg. The prepreg can be used for molding fiber-reinforced plastic. Specifically, it can be used for molded articles for aerospace, the body of a lightweight vehicle, the hull of a lightweight ship, parts of the machine industry, and the like.

[0002]

2. Description of the Related Art Reinforcing fibers are unidirectional (Uni Direc).
The UD prepreg impregnated with a thermosetting resin prepared in the same manner as described above is known and has already been industrially used. However, since the UD prepreg has no reinforcing effect in the direction perpendicular to the fiber, practically, a plurality of prepregs are laminated many times so that the reinforcing effect appears in any direction.

In order to reduce the number of laminations, the reinforcing fibers are impregnated with a thermosetting resin in the form of a woven fabric of fibers that are perpendicular to each other or a triaxial woven fabric having a pseudo isotropic orientation of 0 °, 60 °, and −60 °. Also known prepregs. Also, a prepreg obtained by impregnating a thermosetting resin of a randomly oriented web is known. As prepregs that are widely applied industrially, SMC (Sheet Molding Comp) is used.
sound), which is obtained by impregnating a random chopped strand with a thermosetting resin, and is formed by compression molding in a mold.

On the other hand, when a fiber-reinforced plastic molded article having a random orientation is produced, there is a so-called hand lay-up molding as a method not involving prepreg. This is a method in which a fiber mat is impregnated with a liquid uncured unsaturated polyester and is made to follow a molding die.

[0005]

The UD prepreg must be laminated in order to obtain a reinforcing effect in a plurality of directions, and the operation is complicated. The prepreg, in which the reinforcing fiber is a woven fabric, requires considerable effort in fabricating the woven fabric itself, and the more the direction of the reinforcing fiber is increased in order to approach the isotropic property, the more the flexibility of the woven fabric is lost, so that the prepreg conforms to the mold. In addition, the space formed in the weave of the woven fabric is large, and the resin pool is easily generated in the space. In a randomly oriented web prepreg, the web is not easily deformed along a curved surface, so that bending or tension occurs, and it is difficult to accurately obtain a desired molded product. This tendency becomes more remarkable as the web becomes thicker. In an extreme case, the prepreg is cracked at a stage along the mold. Usually 50k for SMC molding
Since it is necessary to perform compression molding at a high pressure of about g / cm ² , the mold cost is extremely high, and the volume content of the fiber is limited to about 20% in order to secure the required fluidity during compression molding. Therefore, it cannot be used for applications requiring a high reinforcing effect.

[0006] The hand lay-up method requires lamination many times in order to obtain a required thickness, and the working environment is poor due to scattering of styrene monomer. Also, since the resin is manually impregnated, the fiber volume content is about 20 as with SMC.
%, And the reinforcing effect may not be sufficient. That is, an object of the present invention is to provide a prepreg that is substantially isotropic, has excellent mechanical properties such as strength and elasticity, does not lose flexibility and shape retention even if it has a certain thickness, and has excellent mold conformability. Is to provide. Another object of the present invention is to minimize cumbersome laminating work and eliminate the poor working environment of the conventional hand lay-up method. Still another object is to provide an economical molding method which requires a small energy cost for curing and molding the prepreg and does not require a large heat source facility.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, a substantially isotropic strand mat formed by knitting the strands of the reinforcing fiber has a certain thickness. Even if there is, it is excellent in flexibility and shape retention required during resin impregnation or molding, and when this strand mat is impregnated with a UV curable resin composition to form a prepreg, it is almost isotropic, strength and elasticity It has been found that it excels in mechanical properties such as modulus, is flexible even with a certain thickness, shows excellent conformability and shape retention, and can be molded more economically than thermosetting resins. Heading reached the present invention.

That is, the gist of the present invention resides in a prepreg characterized in that a substantially isotropic strand mat formed by knitting a strand of reinforcing fibers is impregnated with an ultraviolet-curable resin composition. .

[0009]

Hereinafter, the present invention will be described in more detail. The material of the reinforcing fiber used in the present invention is not particularly limited as long as it is a reinforcing fiber that can transmit ultraviolet rays.Typically, glass fiber, polyester fiber, or the like can be used, and is selected in consideration of desired mechanical properties and price. do it.

[0010] The number of reinforcing fibers is plural, more preferably 10
A mat is formed by knitting and forming a strand by knitting up to 10,000 strands. The average length of the reinforcing fibers constituting the strand is preferably about 1 to 20 cm, but is not limited thereto. When the fiber is 1 cm or more, it is easy to maintain the shape of the mat, and when the fiber is 20 cm or less, the conformability to the mold is good. A more preferred range is
2.5 to 15 cm. Knitting molding refers to forming a strand mat by regularly sewing another strand into a mat-like aggregate of a large number of strands arranged approximately at random. As a mat-like aggregate of strands, a homogeneously dispersed isotropic aggregate is most preferable, but a pseudo-isotropic orientation (0 °, 60 °, −60 °) is preferable.
°; 0 °, + 45 °, -45 °, 90 °). In order to form the pseudo-isotropic orientation, a method of laminating a plurality of mat-like aggregates of strands oriented in one direction while changing the orientation direction of the strands can be considered.

The strands for knitting may be the same as the other strands forming the strand mat,
It is preferable to use, for example, organic synthetic fibers such as polyester fibers from the viewpoint of economy. The converging number of the monofilaments constituting the knitting strands is better because the larger the number, the better the moldability, and the smaller the number, the more uniform the dispersion of the fibers. There are 1,000. The shape of the knitting strand is preferably flat to increase the fiber content.

The direction of knitting is usually only one direction, but even in two directions, pseudo isotropic orientation (0 °, 60 °, -60 °)
°; 0 °, + 45 °, -45 °, 90 °). The spacing between the knitting strands is not particularly limited as long as it contributes to the improvement of the shape retention of the mat, but is usually about 1 to 50 mm, more preferably 2 to 30 m.
m.

The mat formed by knitting the strand is, specifically, a “COFIL MAT” series manufactured by Brunswick Technologies, ie, “M
−600 ”,“ M-900 ”,“ M-1200 ”,“ M
-1500 "and" M-1800 "as well as" Vitex Q "of the company. A known composition can be used as the ultraviolet-curable resin, and examples thereof include a cationically polymerizable epoxy resin, a radically polymerizable vinyl ester resin, and an unsaturated polyester resin.

As the cationic polymerization type epoxy resin composition, for example, 50 parts by weight of “Epicoat 828” (Yuka Kasper Epoxy Co., Ltd., bisphenol A type epoxy resin) described in JP-A-61-196008 (ERL 4206) 50 parts by weight (union carbide, cycloaliphatic epoxy resin) "KBM 202" 4 parts by weight (Shin-Etsu Chemical, diphenyldimethoxysilane) "UVE-1014" 0.1 part by weight (General Electric Co., Ltd., propylene triarylsulfonium salt) Another example is "Epicoat 828" described in JP-A-61-202823, 20 parts by weight (Yuika Shell Epoxy Co., Ltd., bisphenol A type epoxy resin) "Epicoat 1001" 80 parts by weight (oiled shell epoki Bisphenol A type epoxy resin) 1 part by weight (UVE-1014) (General Electric Co., 50% solution of triarylsulfonium salt in procarbonate). Another example is described in JP-A-61-197879. "Epicoat 828" 12 parts by weight (Yuika Shell Epoxy Co., Ltd., bisphenol A type epoxy resin) "Epicoat 1001" 48 parts by weight (Yuika Shell Epoxy Co., Ltd., bisphenol A type epoxy resin) "KBM" 202 "2 parts by weight (Shin-Etsu Chemical Co., Ltd., diphenyldimethoxysilane)" UVE-1014 "0.6 parts by weight (General Electric Company, a 50% solution of triarylsulfonium salt in propylene carbonate).

As the radically polymerizable vinyl ester resin composition, 100 parts by weight of “DICLEITE UE-3810” described in JP-A-61-202823 (styrene solution of vinyl ester resin, Dainippon Ink) “Kyowa Mag # 20F "1 part by weight (magnesium oxide, Kyowa Chemical) benzoin isobutyl ether and the like.

The prepreg of the present invention refers to one obtained by impregnating a reinforcing fiber with a resin composition, which does not cure for a long time in a state in which ultraviolet rays are substantially blocked, but is completely cured by irradiation with ultraviolet rays. Properties required for the prepreg include shelf life, tackiness, and the like, and these depend on the type of the resin composition. Shelf life is the period during which the prepreg maintains its flexibility, conformity, and can be used, and usually 10 days or less under ultraviolet shielding.
One year, and about 2 to 6 months is practical. The tackiness is tacky and is related to the moldability, and there is an appropriate range depending on the purpose of use.

The method of impregnating the strand mat with the ultraviolet-curable resin composition includes a method using a solvent, a melt method, and the like, and any method may be used according to a conventional method. Ketones such as acetone can be used as the solvent in the cationically polymerizable epoxy resin composition. A large weight per unit area (FAW) of the reinforcing fiber means that the thickness of one ply of the prepreg is large, and in that case, the number of laminations may be small. Conversely, when the FAW is small, the thickness per prepreg ply becomes small, but the moldability is improved. Therefore, the FAW of the prepreg of the present invention may be appropriately adjusted depending on the application, but is usually 500 to 5000 g / c.
m ² , more preferably 1000 to 3000 g / cm ² .

The larger the volume content of the fiber, the greater the reinforcing effect. However, if the volume content is too large, the spring-back property due to the entanglement of the randomly oriented fibers deteriorates the conformability to the mold, and causes voids during molding. Since a defect easily occurs, 30 to 60% is preferable. The prepreg of the present invention can be formed into a thicker prepreg than conventional products while maintaining substantially isotropic, shape-retaining properties, and moldability.
Although a thickness of 1 mm to a maximum thickness of about 5 mm can be obtained, the thickness is preferably about 0.5 to 4 mm because the number of laminations is small and molding is easy.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples unless it departs from the gist.

[0020]

EXAMPLE As a mat of reinforcing fibers, a cofill mat "M-150" manufactured by Brunswick Technologies, Inc. was used.
0 "was used. In this mat, strands in which about 100 glass fibers each having a length of 5 cm are converged are randomly dispersed and knitted with polyester fibers. The spacing between the knitting fibers is about 4 mm. FAW is 1
It was 450 g / m ² .

As the ultraviolet curable resin composition, a cationically polymerizable epoxy resin was used. "Epicoat 828" 40 parts by weight (Yuika Shell Epoxy Co., Ltd., bisphenol A type epoxy resin) "Epicoat 1001" 60 parts by weight (Yuika Shell Epoxy Co., Ltd., bisphenol A type epoxy resin) "KBM 202" 2 parts by weight Part (Shin-Etsu Chemical Co., diphenyldimethoxysilane) 0.6 parts by weight "UVE-1014" (General Electric Co., Ltd., 50% propylene carbonate solution of triarylsulfonium salt) Using acetone as a solvent, immersion impregnation was performed. After the impregnation, the solvent is removed in vacuum at 40 ° C. for 24 hours,
I got a prepreg. The glass weight content was 63 wt% and the volume content was 45 vol%. Moldability was confirmed using one ply of this prepreg (size 50 cm × 50 cm).

A male mold having a mountain-shaped tip with a radius of curvature of 100 mm was attached. Since the prepreg slightly slackened, the resin was softened and allowed to follow the mold due to warm air at about 80 ° C. The working environment was very clean, without smell and without stickiness. Then FE
The film was covered with a P film and a transparent nylon film, and the ends were sealed with sealant tape to form a vacuum bag. While drawing a vacuum through a vacuum port, hot air was sent by a dryer to set the prepreg temperature to about 60 ° C., and almost all the air in the prepreg was removed. Then, the temperature in the bag was returned to room temperature while being kept in vacuum, and ultraviolet light was irradiated for about 15 minutes to complete the curing. A molded article having a good appearance was obtained. The volume content of the glass fiber was 48 vol%, and the thickness of the molded product was 1.2 mm.

[0023]

The prepreg of the present invention is substantially isotropic, has excellent mechanical properties such as strength and elastic modulus, is flexible even with a certain thickness, and exhibits excellent mold conformability and shape retention. . Unlike a prepreg made of a thermosetting resin, a large heat source is not required. Therefore, the lamination operation can be simplified, and a molded article having a large reinforcing effect can be obtained economically and easily, thereby providing a great industrial advantage.

Claims (6)

(57) [Claims] 1. A prepreg characterized by impregnating a substantially isotropic strand mat formed by knitting strands of reinforcing fibers with an ultraviolet curable resin composition. 2. The strand according to claim 1, wherein a plurality of reinforcing fibers each having a length of 1 to 20 cm are converged.
The prepreg described. 3. The prepreg according to claim 1, wherein the volume content of the reinforcing fibers is 30 to 60%. 4. The prepreg according to claim 1, wherein the convergence number of the monofilaments constituting the strand is 10 to 10000. 5. The reinforcing fiber has a weight per unit area of 50.
0-5000g / m ^Two5. The method according to claim 1, wherein
The prepreg according to the above. 6. The prepreg according to claim 1, wherein the reinforcing fibers are glass fibers.