JP5173358B2 - Prepreg with protective film - Google Patents

Description

The present invention relates to a prepreg with a protective film comprising a prepreg obtained by impregnating a reinforcing fiber base material with an epoxy resin composition having a high viscosity at room temperature, and a protective film that covers and protects one or both sides thereof.

In recent years, fiber reinforced composite materials using carbon fibers, aramid fibers, etc. as reinforcing fibers have utilized their high specific strength and specific modulus to make structural materials such as aircraft and automobiles, tennis rackets, golf shafts, fishing rods, etc. It has been widely used for general industrial applications.

As a method for producing such a fiber-reinforced composite material, a prepreg which is a sheet-like intermediate base material in which a reinforcing fiber base material is impregnated with a matrix resin, for example, a high viscosity liquid uncured thermosetting resin composition is used. A method of laminating and shaping the resin composition and then curing the resin composition by heating and pressurization was common.

And as a conventional sheet-like prepreg, what used the matrix resin completely impregnated with the matrix-like reinforcing fiber base material is mainly used, and the autoclave molding was mainly used as the molding method. However, recently, as a method that does not use an expensive molding apparatus such as an autoclave, a molding method in which a prepreg obtained by partially impregnating a matrix resin into a reinforcing fiber base and oven molding is proposed (for example, a patent) References 1 and 2).
US Pat. No. 6,139,942 International Publication No. 00/27632 Pamphlet

When forming a fiber reinforced composite material by laminating conventional prepregs, air trapped between the layers may form voids in the molded product. To prevent this, molding is performed by applying high pressure using an autoclave or the like. There were many things to do. However, in the partially impregnated prepreg, the portion of the unimpregnated reinforcing fiber becomes a ventilation path. Therefore, if the pressure and pressure are sufficiently reduced after heating, pressurization is performed at a lower pressure than that of the conventional prepreg and less voids are formed. There is an advantage that becomes possible.

In the method using such a partially impregnated prepreg, it is necessary to flow the thermosetting resin composition in the heating / pressurizing step and impregnate unimpregnated reinforcing fibers. For this purpose, a thermosetting resin composition having a high viscosity and low fluidity at room temperature and a low viscosity and good impregnation property in a relatively high temperature range is preferable. It is suitable for the production of partially impregnated prepregs using a resin having a relatively high viscosity at room temperature and a sufficiently low viscosity in a relatively high temperature region, and for producing fiber-reinforced composite materials by resin film infusion. As an epoxy resin composition, a resin composition in which a crystalline thermosetting resin having a melting point of 50 ° C. or higher is dispersed in the form of particles has also been proposed (see, for example, Patent Document 3).
JP 2005-298713 A

By the way, there is a prepreg in which a protective film is adhered and laminated on one side or both sides of a sheet-like prepreg in order to prevent foreign matter from adhering to the prepreg surface depending on the application. However, in the case of a prepreg using a resin composition having a relatively high viscosity at room temperature and a low fluidity as described above, the protective film attached to one or both surfaces of the sheet-like prepreg is transferred during prepreg. There is a problem that it is easy to peel off. In particular, when a sheet-like prepreg is cut into an appropriate size by an automatic cutting machine, there is a problem that a protective film peeled off from the prepreg gets entangled with the blade of the cutting machine and causes a cutting trouble.

An object of the present invention is to select a protective film that is suitable for coating and protecting the surface of a sheet-like prepreg and that has appropriate adhesion (peelability), and a resin composition having a relatively high viscosity at room temperature. To provide a prepreg with a protective film comprising a prepreg used, in particular, a partially impregnated prepreg obtained by partially impregnating a reinforcing fiber base material with a high-viscosity epoxy resin composition, and a protective film adhered to the surface thereof. is there.

According to the first aspect of the present invention, a reinforcing fiber base material is impregnated with an epoxy resin composition having a viscosity at 25 ° C. in the range of 5 × 10 ⁵ to 1 × 10 ⁷ Pa · S. A prepreg with a protective film comprising a prepreg and a protective film with a protective film in close contact with one or both surfaces thereof, wherein the surface wettability of the protective film is in the range of 32 to 45 mmN / m. .

The invention described in claim 2 is that the adhesion between the prepreg and the protective film adhered to one or both sides thereof is in the range of 0.05 to 1.0 N / cm at 90 ° peel strength. The prepreg with a protective film according to claim 1.

According to a third aspect of the present invention, the prepreg is a partially impregnated prepreg obtained by partially impregnating a reinforcing fiber base material with an epoxy resin composition. It is a prepreg.

In the invention described in claim 4, the epoxy resin composition comprises a liquid epoxy resin (A) having a viscosity at 25 ° C. of 100 Pa · S or more, an epoxy resin (B) that is solid at 25 ° C., and dicyandiamide. It is an epoxy resin composition containing a hardening | curing agent (C), The prepreg with a protective film of any one of Claims 1-3 characterized by the above-mentioned.

The invention described in claim 5 is the prepreg with a protective film according to any one of claims 1 to 4, wherein the reinforcing fiber substrate is a multiaxial woven fabric.

And the invention described in Claim 6 is a prepreg with a protective film of any one of Claims 1-5 whose fiber fabric weight of a reinforcement fiber base material is 200-1,000 g / m < ² >.

According to the present invention, a prepreg with a protective film obtained by impregnating a reinforcing fiber base material with an epoxy resin composition having a high viscosity at room temperature can be obtained. Since the protective film can be sufficiently adhered to the sheet-like prepreg, it is possible to prevent foreign matters from adhering to the prepreg and to improve troubles during prepreg cutting. Further, since the adhesion, that is, the peelability is appropriately adjusted, the protective film can be easily peeled off when the prepreg is laminated.

In the present invention, particularly when a prepreg with a protective film made of a partially impregnated prepreg obtained by partially impregnating a reinforcing fiber substrate with a high-viscosity epoxy resin composition is used, in the molding process of the fiber-reinforced composite material Thus, it is possible to easily deaerate, and an excellent effect that a large-area fiber-reinforced composite material with few voids can be produced with high productivity can be obtained.

The present invention relates to an epoxy resin composition having a viscosity at 25 ° C. in the range of 5 × 10 ⁵ to 1 × 10 ⁷ Pa · S, preferably in the range of 5 × 10 ^{5 to} 5 × 10 ⁶ Pa · S. In a prepreg with a protective film comprising a prepreg impregnated in a base material and a protective film adhered to one or both surfaces thereof, the surface wettability of the protective film is 32 to 45 mmN / m, preferably 32 to 40 mmN / m. Is within the range of

The surface wettability in the present invention is an index representing surface characteristics related to the hydrophobicity / hydrophilicity / adhesiveness of a film, and is a “plastic-film and sheet-wetting tension test method” of JIS K · 6768. Means the value measured by

In the present invention, when the surface wettability of the protective film is less than 32 mmN / m, the adhesion between the prepreg and the protective film is insufficient, and the protective film tends to peel from the prepreg. Moreover, when the surface wettability of a protective film exceeds 45 mmN / m, a prepreg and a protective film will adhere too much and it will become difficult to peel a protective film from a prepreg.

In order to adjust the surface wettability of the protective film within the above range, the surface of the protective film may be surface-treated by a method such as corona discharge, plasma treatment, ozone treatment, or UV treatment. In the present invention, corona discharge treatment is preferable. In the corona discharge treatment, a corona discharge is generated by applying a high-frequency / high-voltage output supplied by a high-frequency power source between the discharge electrode and the treatment roll, and the corona treatment is performed by passing the protective film under the corona discharge.

Examples of the protective film of the present invention include films of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and the like. From the viewpoint of cost, polyethylene (PE) and polypropylene (PP) are preferable.

As described above, the present invention is suitable for adhesion between a prepreg obtained by impregnating a reinforcing fiber base material with a high-viscosity epoxy resin composition and the protective film as described above, and the surface of the protective film is appropriate by corona discharge or the like. It is characterized by improved surface treatment to give wettability. As the prepreg, a partially impregnated prepreg obtained by partially impregnating a reinforcing fiber base material with an epoxy resin composition can also be used.

And the epoxy resin composition of this invention is an epoxy resin composition whose viscosity in 25 degreeC exists in the range of 5 * 10 < ⁵ > -1 * 10 < ⁷ > Pa * S. In the present invention, the viscosity of the resin or resin composition was determined by the following method. That is, using a dynamic viscoelasticity measuring device (for example, rheometer VAR-100: manufactured by Rheologicala Co., Ltd.), the temperature is simply raised at a heating rate of 2 ° C./min with a parallel plate, and measured at a frequency of 1 Hz and a plate interval of 1 mm. Went. When the viscosity was 10 ⁴ Pa · s or more, measurement was performed using a parallel plate of Ф8. When the viscosity was less than 10 ⁴ Pa · s, the measurement was performed using a parallel plate of Ф40. In the process of heating the resin composition, the viscosity of the resin composition decreases, but when curing starts at a certain temperature, the viscosity rapidly increases. The temperature at the bending point of the viscosity curve at this time is the curing start temperature, and the viscosity at that time is defined as the minimum viscosity.

In the present invention, the epoxy resin composition is preferably a liquid epoxy resin (A) having a viscosity of 100 Pa · S or more at 25 ° C., an epoxy resin (B) that is solid at 25 ° C., and a dicyandiamide curing agent (C ) As an essential component.

Further, in the present invention, it is particularly preferable that the resin composition has a curing start temperature in the range of 100 to 120 ° C. and the viscosity (minimum viscosity) at that time is in the range of 0.1 to 5 Pa · S. . Furthermore, the viscosity at 25 ° C. is preferably 5 × 10 ^{5 to} 5 × 10 ⁶ Pa · s. From the viewpoint of moldability, particularly impregnation into reinforcing fibers such as carbon fibers, the minimum viscosity is preferably 0.1 to 2 Pa · S.

Examples of the liquid epoxy resin (A) include a glycidyl ether type epoxy resin obtained from a compound having a hydroxyl group in the molecule, a glycidyl amine type epoxy resin obtained from a compound having an amino group in the molecule, and a carboxyl group in the molecule. A glycidyl ester type epoxy resin obtained from a compound having a cycloaliphatic epoxy resin obtained from a compound having an unsaturated bond in the molecule, or an epoxy resin in which two or more types selected from these are mixed in the molecule Can be used.

Specific examples of the glycidyl ether type epoxy resin include bisphenol A type epoxy resin obtained by reaction of bisphenol A and epichlorohydrin, bisphenol F type epoxy resin obtained by reaction of bisphenol F and epichlorohydrin, resorcinol and epi Examples thereof include resorcinol type epoxy resins obtained by reaction of chlorohydrin, other polyethylene glycol type epoxy resins, polypropylene glycol type epoxy resins, naphthalene type epoxy resins, and halogen or alkyl substituted products thereof.

Specific examples of the glycidylamine type epoxy resin include tetraglycidyldiaminodiphenylmethanes, glycidyl compounds of aminophenol, glycidylanilines, and glycidyl compounds of xylenediamine.

The epoxy resin (B) that is solid at 25 ° C. is used after being dissolved in the epoxy resin composition of the present invention. For example, in the case of preparing a partially impregnated prepreg, there is an effect of increasing the viscosity of the epoxy resin composition and suppressing the resin fluidity in the decompression step near room temperature. On the other hand, at the time of molding and curing, the viscosity is lowered before gelation of the epoxy resin composition (before the start of curing) and good fluidity is imparted. The preferable range of the melting point of the component (B) is 50 to 130 ° C, more preferably 60 to 100 ° C.

The component (B) solid epoxy resin includes bisphenol A type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, stilbene type epoxy resin, hydroquinone type epoxy resin, terephthalic acid type epoxy resin, isocyanurate type epoxy resin. And polyalkyl bisphenol F type epoxy resins.

Another essential component in the epoxy resin composition is a dicyandiamide curing agent (C). Such component (C) is used by being dispersed in the epoxy resin composition of the present invention. The curing agent is usually used in the form of particles, but the average particle size is preferably 10 μm or less, and more preferably 7 μm or less. In order to adjust the curing start temperature, it is preferable to use a curing accelerator in addition to the components (A), (B), and (C). As the curing accelerator, urea-based curing accelerators, imidazole compounds, amine adducts and the like are preferably used.

In addition to the components (A), (B), and (C), the epoxy resin composition of the present invention contains organic particles such as rubber particles and thermoplastic resin particles, a soluble thermoplastic resin, and the like as necessary. One kind or two or more kinds can be contained. The addition amount is in the range of 20% by weight or less with respect to the total amount of the components (A), (B), and (C).

As the rubber particles, cross-linked rubber particles and core-shell rubber particles obtained by graft polymerization of a different polymer on the surface of the cross-linked rubber particles are preferably used from the viewpoint of handleability and the like. As the thermoplastic resin particles, polyamide particles and polyimide particles are preferably used. As the soluble thermoplastic resin, polyethersulfone, polysulfone, polyimide, polyetherimide, polycarbonate, polyetherethersulfone, polyvinyl formal, polymethyl methacrylate and the like are preferably used.

In the present invention, it is preferable that the adhesion between the prepreg and the protective film adhered to one or both sides thereof is 90 ° peel strength and is in the range of 0.05 to 1.0 N / cm. The adhesion between the sheet-shaped prepreg and the protective film is in accordance with JIS K 6854-1 “90 degree peeling adhesion strength test method”, the test speed is 50 mm / min, and the length 50 mm test. The average peel strength is defined as the adhesion of the protective film.

The adhesion of the protective film is preferably in the range of 0.05 to 1.0 N / cm, but if the adhesion of the protective film is less than 0.05 N / cm, the adhesion between the prepreg sheet and the protective film. May not be sufficient, and the protective film may be peeled off from the prepreg. If it exceeds 1.0 N / cm, the prepreg sheet and the protective film are too close to each other, and the protective film may not be peeled off from the prepreg.

The reinforcing fiber for the reinforcing fiber substrate used in the present invention is not particularly limited, and examples thereof include glass fiber, Kevlar fiber, carbon fiber, graphite fiber, and boron fiber. Of these, carbon fibers and graphite fibers are preferred in terms of specific strength and specific elastic modulus.

The form of the reinforcing fiber base material for prepreg is not particularly limited, but a plain fabric, a twill fabric, a satin fabric using reinforcing fiber bundles as warp and / or weft, and a collection of reinforcing fiber bundles arranged in parallel Unidirectional woven fabric, bi-directional woven fabric, multiaxial woven fabric, and the like. Alternatively, it may be a nonwoven fabric made of reinforcing fibers, mat, knit, braid or the like. Multiaxial woven fabric is a bundle of fiber reinforcements aligned in one direction, laminated at different angles, and stitched yarns such as nylon yarn, polyester yarn, and glass fiber yarn. It refers to a woven fabric that penetrates in the direction and stitches by reciprocating along the surface direction between the front and back surfaces of the laminate.

In the present invention, when a partially impregnated prepreg obtained by partially impregnating a reinforcing fiber base material with an epoxy resin composition is used, the fiber reinforcement used for partial impregnation is used from the viewpoint of controlling the unimpregnated ratio of the partially impregnated prepreg. The woven fabric is preferably a multiaxial woven fabric. Examples of preferred multiaxial fabrics include [+ 45 / −45], [−45 / + 45], [0/90], [0 / + 45 / −45], [0 / −45 / + 45], [0 / + 45/90 / -45]. 0, ± 45, 90 represents the lamination angle of each layer constituting the multiaxial woven fabric, and the fiber axis directions of the reinforcing fibers aligned in one direction are 0 °, ± 45 ° with respect to the length direction of the woven fabric. , 90 °. The stacking angle is not limited to these angles, and can be any angle.

The prepreg of the present invention preferably has a reinforcing fiber amount (fiber basis weight) per unit area of 200 to 1000 g / m ² . When the amount of prepreg reinforcing fibers is less than 200 g / m ^2, it is necessary to increase the number of laminated sheets in order to obtain a predetermined thickness when forming for a fiber reinforced composite material, which may complicate the operation. When it exceeds 1000 g / m ² , the drapeability of the prepreg tends to decrease.

In the present invention, the prepreg preferably has a fiber content of 30 to 80% by weight. More preferably, it is 35-70 weight%, More preferably, it is 40-65 weight%. If the fiber ratio is less than 30%, the amount of the resin is too large to obtain the advantages of the fiber reinforced composite material having excellent specific strength and specific elastic modulus. If the fiber ratio exceeds 80% by weight, poor resin impregnation occurs. The resulting composite material can be highly voided.

The partially impregnated prepreg used in the preferred embodiment of the present invention, in which the reinforcing fiber base is partially impregnated with the epoxy resin composition, is not completely impregnated with the reinforcing fiber base, Although it is a partially impregnated prepreg, the degree is defined by the measurement by the water absorption method described below.

In the prepreg partially impregnated with the epoxy resin composition, when the unimpregnated ratio of the prepreg is evaluated by a water absorption method, the water absorption is preferably 5 to 30% by weight, more preferably 10 to 25%. % By weight. In addition, the water absorption rate of a prepreg here cuts a prepreg into 100x100 mm, and measures a weight (W1). Thereafter, the prepreg is submerged in water in a desiccator and decompressed to replace the air and water inside the prepreg. The prepreg is taken out of the water, the surface water is wiped off, and the weight (W2) of the prepreg is measured. The water absorption rate is calculated by the following formula.
Water absorption (%) = [(W2−W1) / W1] × 100
W1: Weight of prepreg (g)
W2: Weight of prepreg after water absorption (g)

If the unimpregnated portion has a water absorption of less than 5% by weight, the reinforcing fiber layer may have an insufficient ventilation path. If it exceeds 30% by weight, the thickness of the partially impregnated prepreg and the fiber-reinforced composite material after molding The thickness of the fiber is different, and the fiber reinforced composite material tends to wrinkle and wrinkle.

Hereinafter, an example of the manufacturing method of the prepreg with a protective film of this invention is demonstrated. In the present invention, it is preferable to first prepare an epoxy resin composition by mixing and dissolving the liquid epoxy resin (A) and the solid epoxy resin (B), and dispersing and blending the curing agent (C) therein. Next, the epoxy resin composition is coated on a release paper with a reverse roll coater or a knife coater to form a film, and the obtained film is continuously laminated and arranged on both sides of the reinforcing fiber base. A prepreg can be produced by pressurizing and impregnating the reinforcing fiber substrate with the resin composition. Here, conditions such as temperature, pressure and time for impregnation can be adjusted to adjust the degree of resin impregnation into the reinforcing fibers.

Next, one side is subjected to, for example, corona discharge treatment, a polyethylene protective film having a surface wettability adjusted to 40 mmN / m is prepared, the release paper on the upper surface of the prepreg is peeled off, and the prepreg surface and corona discharge-treated protective film are prepared. The prepreg with a protective film can be continuously produced by combining the surfaces and pressurizing at 40 ° C. using a hot roller or the like. By appropriately setting heating / pressurizing conditions such as a hot roller, the adhesion between the prepreg and the protective film can be adjusted to a range of 0.05 to 1.0 N / cm at 90 ° peel strength. it can.

Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, the viscosity of the uncured product of the epoxy resin composition is simply increased by a dynamic viscoelasticity measuring device (Rheometer VAR-100: manufactured by Rheology Corporation) using a parallel plate at a temperature rising rate of 2 ° C./min. The measurement was performed at a frequency of 1 Hz and a plate interval of 1 mm. When the viscosity was 10 ⁴ Pa · s or higher, a parallel plate of Ф8 was used and the strain was measured at 0.0032. When the viscosity was less than 10 ⁴ Pa · s, a parallel plate of Ф40 was used and the strain was measured at 3.16.

In the examples, the prepreg was produced as follows. The epoxy resin composition was formed into a film on release paper using a knife coater so as to have a weight per unit area of 150 g / m ² , thereby producing a resin film. As a reinforcing fiber base material, carbon fiber multiaxial woven fabric made of “TENAX” (registered trademark) HTA-12K manufactured by Toho Tenax Co., Ltd. (two layers laminated at an angle of + 45 / −45, total basis weight of the woven base material 500 g / m ² ), the carbon fiber multiaxial woven fabric was coated with the resin film on both upper and lower surfaces, and impregnated with an impregnation apparatus having a heating zone of 2 m, which was composed of a hot plate heated to a predetermined temperature and three hot rollers. .
A line speed of 2 m / min and 3 hot rollers were each impregnated at a linear pressure of 50 kg / m to obtain a prepreg having a resin content of 37% by weight.

Next, a voltage of 5 to 12 KV is applied between the discharge electrode and the treatment roll in the atmosphere to generate a corona discharge, and a polyethylene protective film is passed under the corona discharge to perform a corona treatment on one side of the protective film. A protective film made of polyethylene having different wettability was prepared. Then, the release paper on the upper surface of the prepreg was peeled off, the surface of the prepreg and the film surface subjected to corona discharge treatment were combined, and pressurized with a roller linear pressure of 50 kg / m at 40 ° C. to obtain a prepreg sheet with a protective film.

A small piece having a width of 25 × 200 mm was cut out from the above prepreg, and the peel strength of the protective film from the prepreg was evaluated in accordance with the JIS K 6854-1 90 degree peel adhesion strength test method. The test speed was 50 mm / min, a 50 mm length test was performed, and the average peel strength was determined.

A small piece of 100 × 100 mm was cut out from the prepreg sheet, and the release paper and the protective film were peeled off. Then, the prepreg was submerged in water in a desiccator and decompressed to replace the air and water inside the prepreg. Next, the prepreg pieces were taken out of the water, the surface water was wiped off, the weight of the prepreg pieces before and after water absorption was measured, the water absorption was calculated, and the degree of partial impregnation of the prepreg was determined.

The prepregs obtained as described above were laminated on an aluminum mold in a plane-symmetric manner, and the whole was bagged with a nylon bag, and the interior of the bag was vacuumed at -0.1 MPa for 30 minutes at 25 ° C. The pressure was reduced. Thereafter, while maintaining the reduced pressure, the mixture was heated to 90 ° C. at a rate of 2 ° C./min, and held at 90 ° C. for 30 minutes. Thereafter, the mixture was heated to 130 ° C. at a rate of 2 ° C./min and cured at 130 ° C. for 90 minutes to produce a fiber-reinforced composite material (molded body). A cross-sectional observation of the central portion of the molded body was performed, and the void area ratio with respect to the cross-sectional area was calculated as the void ratio.

[Example 1]
As component (A), EPN-1138 (phenol novolac resin [Asahi Kasei Epoxy Co., Ltd.) 62 parts by weight and as component (B) EP-1002 (bisphenol A epoxy resin [Japan Epoxy Resin Co., Ltd.]) 38 parts by weight, 5 parts by weight of dicyandiamide (DICY) as component (C), 3 of 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DUMU) as a curing accelerator as component (D) Part by weight was used.

The mixture of components (A) and (B) was heated and dissolved at 120 ° C., then cooled to 70 ° C. at room temperature, and components (C) and (D) were added and kneaded. The viscosity of this resin composition at 25 ° C. was 1 × 10 ⁶ Pa · s, and the minimum viscosity of the resin composition was 1 Pa · s (curing start temperature 106 ° C.).

Using this resin composition, a prepreg was produced by the above method (hot plate and hot roller temperature 100 ° C.). Next, the release paper on the upper surface of the prepreg was peeled off, and the polyethylene film having a surface wettability of 40 mmN / m and the prepreg were combined and pressurized at 40 ° C. with a roller linear pressure of 50 kg / m to obtain a prepreg with a sheet-like polyethylene film. .

As shown in Table 1, the adhesion strength (peeling strength) of the polyethylene film was 0.6 N / cm, the adhesion strength of the polyethylene film was good, and the handleability of the prepreg was also good. The water absorption of the prepreg was 17% by weight. And the void rate of the molded object produced by the said method using this partial impregnation prepreg was 0.5%, and the favorable molded object with few voids was obtained. In Table 1, the handleability of the prepreg is indicated by good (◯) or not (×), and the moldability of the molded body is indicated by the large void ratio (×) and small (◯).

[Example 2]
The same experiment as in Example 1 was performed, except that a polyethylene film having a surface wettability of 45 mmN / m was used. As shown in Table 1, the adhesion of the polyethylene film was good and the handleability of the prepreg was good.

[Example 3]
The same experiment as in Example 1 was performed except that a polyethylene film having a surface wettability of 32 mmN / m was used. As shown in Table 1, the adhesion of the polyethylene film was good and the handleability of the prepreg was good.

[Comparative Example 1]
The same experiment as in Example 1 was performed except that a polyethylene film having a surface wettability of 30 mmN / m was used. As shown in Table 1, the adhesion of the polyethylene film was too weak, and the prepreg was poor in handleability.

[Comparative Example 2]
The same experiment as in Example 1 was performed except that a polyethylene film having a surface wettability of 50 mmN / m was used. The adhesion of the polyethylene film was too strong, and when the polyethylene film was peeled from the prepreg, the carbon fibers were peeled from the carbon fiber multiaxial fabric. Therefore, the handling property of the prepreg was bad.

[Comparative Example 3]
As component (A), 70 parts by weight of EPN-1138 (phenol novolac resin), 10 parts by weight of EP-828 (bisphenol A type epoxy resin [manufactured by Japan Epoxy Resin Co., Ltd.), and EP-1002 as component (B) (Bisphenol A type epoxy resin: solid) 20 parts by weight, 5 parts by weight of dicyandiamide as component (C), and 3- (3,4-dichlorophenyl) -1,1-dimethyl as curing accelerator (D) 3 parts by weight of urea was used.

A mixture of the two components (A) and (B) was heated and dissolved at 120 ° C., cooled to 70 ° C. at room temperature, and components (C) and (D) were added and kneaded. The viscosity of this resin composition at 25 ° C. was 5 × 10 ⁴ Pa · s, and the minimum viscosity of the resin composition was 0.4 Pa · s (curing start temperature 106 ° C.). Using this resin composition, a prepreg with a polyethylene film was obtained in the same manner as in Example 1. The water absorption of the obtained prepreg was 13% by weight. And the molded object was created by the said method using this partially impregnated prepreg.

As shown in Table 1, in this case, the viscosity of the epoxy resin composition was too low, and the handleability of the prepreg was poor. Moreover, the adhesion of the polyethylene film was strong, and when the polyethylene film was peeled from the prepreg, the carbon fiber was easily peeled from the carbon fiber multiaxial woven fabric.

[Comparative Example 4]
The same experiment as Comparative Example 3 was performed except that a polyethylene film having a surface wettability of 30 mmN / m was used. As shown in Table 1, in this case, the adhesion of the polyethylene film was good, and the handleability of the prepreg was good. However, the molded body produced by the above method using this partially impregnated prepreg had many voids, and the void ratio was 2.0%. Compared with the example, the void ratio was high (the moldability of the molded body was poor).

Claims (6)

A prepreg obtained by impregnating a reinforcing fiber base material with an epoxy resin composition having a viscosity at 25 ° C. in the range of 5 × 10 ⁵ to 1 × 10 ⁷ Pa · S, and a protective film adhered to one or both sides thereof A prepreg with a protective film, wherein the surface wettability of the protective film is in the range of 32 to 45 mmN / m. 2. The protective film according to claim 1, wherein the adhesion between the prepreg and the protective film adhered to one or both sides thereof is 90 ° peel strength and is in the range of 0.05 to 1.0 N / cm. Prepreg with. The prepreg with a protective film according to claim 1 or 2, wherein the prepreg is a partially impregnated prepreg obtained by partially impregnating a reinforcing fiber substrate with an epoxy resin composition. The epoxy resin composition includes a liquid epoxy resin (A) having a viscosity of 100 Pa · S or more at 25 ° C., an epoxy resin (B) that is solid at 25 ° C., and a dicyandiamide curing agent (C). It is a composition, The prepreg with a protective film of any one of Claims 1-3 characterized by the above-mentioned. The prepreg with a protective film according to any one of claims 1 to 4, wherein the reinforcing fiber substrate is a multiaxial woven fabric. Fiber areal weight of the reinforcing fiber substrate, 200~1,000g / ^{m 2} protective film with a prepreg of any one of claims 1 to 5,.