JP5441437B2 - Partially impregnated prepreg, method for producing the same, and method for producing a fiber-reinforced composite material using the same - Google Patents

Description

The present invention provides a partially impregnated prepreg which can form a high-quality fiber-reinforced composite material without using an expensive molding apparatus such as an autoclave, and has excellent handleability, and a production method thereof, The present invention relates to a method for producing a fiber-reinforced composite material using the prepreg.

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 in general industries and sports applications.

As one 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 high-viscosity liquid uncured thermosetting resin composition, is laminated. There is a method of shaping and then curing by heating and pressurization to obtain a desired molded body.

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 device 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 has been proposed (for example, a patent) Reference 1 and 2).

US Pat. No. 6,139,942 International Publication No. 00/27632 Pamphlet

When molding a composite material by laminating conventional prepregs, the air trapped between the layers may become voids in the molded product. To prevent this, molding is performed by applying high pressure using an autoclave or the like. There were many. 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 (oven molding) becomes possible.

On the other hand, in recent years, high-weight carbon fiber sheets have been used for the purpose of simplifying the laminating operation. In particular, a multiaxial stitch base material (multiaxial fabric) in which two or more layers in which carbon fiber bundles are arranged in parallel in a sheet shape is laminated and these layers are integrated by stitch yarns is often used. A prepreg using a base material is being frequently used.

However, when such a prepreg is made into a partially impregnated prepreg for use in oven molding, since the base material has a high basis weight and is partially impregnated, dry fibers (not impregnated with resin) inside the prepreg. A large number of fibers). In addition, when the prepreg is cut, a large number of fluffs are generated from the dry fiber, and there is a problem that workability is remarkably deteriorated. On the contrary, when the impregnation degree is increased in order to suppress the generation of fluff, there is a problem that voids are generated without sufficient deaeration as described above.

An object of the present invention is to provide a partially impregnated prepreg that can be easily degassed and can produce a large-area fiber-reinforced composite material with few voids with a simple method and means, and such a partially impregnated prepreg. It is providing the manufacturing method of the fiber reinforced composite material using this.

In the course of studying a method for producing a finely reinforced composite material using a partially impregnated prepreg, the present inventor has a partial impregnation ratio and impregnation state of a matrix resin, a type of reinforcing fiber base to be used, a type of matrix resin to be used, Furthermore, the present inventors have found that selection of molding conditions for a molded article using a partially impregnated prepreg is very important, and have reached the present invention. That is, the said subject of this invention is achieved by the following this invention of Claims 1-11 of a claim.

The invention described in claim 1 is a prepreg in which a thermosetting resin sheet is partially impregnated on both surfaces of a reinforcing fiber substrate, and the resin impregnation is performed by non-uniform pressure during transfer of the resin sheet. When the ratio of the unimpregnated portion is evaluated by an ultrasonic flaw detection method, the area of the reinforcing fiber base is 80% or more 80%. % Partially impregnated prepreg characterized by being in the range of less than%.

The invention described in claim 2 is a multiaxial stitch base material in which the reinforcing fiber base material is formed by laminating two or more layers in which carbon fiber bundles are arranged in parallel in a sheet shape, and integrating these layers with stitch yarns. The partially impregnated prepreg according to claim 1, wherein:

The invention described in claim 3, the fiber basis weight of the reinforcing fiber substrate is a portion impregnated prepreg according to claim 1 or 2 characterized in that the 200~1,000g / m ^2.

The invention described in claim 4 is characterized in that the ratio of the unimpregnated portion of the thermosetting resin is in the range of 2 to 15% in terms of water absorption when evaluated by the water absorption method. It is a partially impregnated prepreg.

In the invention described in claim 5, a thermosetting resin sheet is placed on both sides of a reinforcing fiber base material, and then the reinforcing fiber base material and the resin sheet are non-uniformly pressed to apply the resin to the reinforcing fiber base. The material is impregnated non-uniformly, and the ratio of the unimpregnated portion of the resin when evaluated by an ultrasonic flaw detection method is within a range of 25% or more and less than 80% of the area of the reinforcing fiber base. This is a method for producing a partially impregnated prepreg.

In the invention described in claim 6, when pressurizing the reinforcing fiber base and the thermosetting resin sheet, a base having 0.02-0.1 mm unevenness in the thickness direction is used as the reinforcing fiber base. The partially impregnated prepreg manufacturing method according to claim 5, wherein the pressurizing is performed.

The invention according to claim 7 is characterized in that when the reinforcing fiber base and the thermosetting resin sheet are pressed, the surface is pressed non-uniformly using a slit roller having an unevenness of 0.02 to 0.1 mm on the surface. The partially impregnated prepreg manufacturing method according to claim 5.

The invention according to claim 8 is a prepreg formed by partially impregnating a thermosetting resin sheet on both sides of a reinforcing fiber base material, wherein the resin impregnated portion is formed by non-uniform pressure during transfer of the resin sheet. And the unimpregnated portion is in the form of stripes, lattices, or diagonal lattices, and the proportion of the unimpregnated portions is 25% or more and 80% of the area of the reinforcing fiber substrate when evaluated by an ultrasonic flaw detection method. A plurality of partially impregnated prepregs in the range below are laminated to form a laminated body, and the obtained laminated body is covered with a back material, and then the inside is depressurized at a temperature of 25 ° C. or lower, and then the outside is maintained while maintaining the reduced pressure. The fiber-reinforced composite material manufacturing method is characterized in that a thermosetting resin is impregnated into the inside of the reinforcing fiber base material and cured by heating.

The invention according to claim 9 is, as a thermosetting resin, a liquid epoxy resin (A) whose viscosity at 25 ° C. is 100 Pa · S or more, an epoxy resin (B) which is solid at 25 ° C., and dicyandiamide curing. The method for producing a fiber-reinforced composite material according to claim 8, wherein an epoxy resin composition containing an agent (C) as an essential component is used.

In the invention according to claim 10, the pressure reduction is performed in the range where the viscosity of the epoxy resin composition is 5 × 10 ⁵ Pa · S or more, 15 minutes or more, and the degree of vacuum is −0.09 MPa or less. It is a manufacturing method of the fiber reinforced composite material of Claim 9 characterized by the above-mentioned.

The invention according to claim 11 is characterized in that the heating is performed by a step cure method in which the heating is held for 10 hours at a temperature lower by 10 to 25 ° C. than the curing start temperature of the epoxy resin composition, and then raised to the curing temperature. It is a manufacturing method of the fiber reinforced composite material of Claim 9 or 10.

According to the present invention, a partially impregnated prepreg excellent in handleability, which is a high weight prepreg for oven molding, can be obtained. When such a prepreg is used, a fiber-reinforced composite material with good quality can be obtained without using an expensive molding device such as an autoclave.

The partially impregnated prepreg of the present invention is a prepreg obtained by impregnating both sides of a reinforcing fiber substrate with a thermosetting resin sheet (including a film), and the resin of the resin sheet is partially applied to the reinforcing fiber substrate. The ratio of the resin impregnated portion when impregnated and evaluated by the ultrasonic flaw detection method is in the range of 25% or more and less than 80%, preferably 30 to 70% of the area of the reinforcing fiber base. Is. Moreover, when the ratio of the non-impregnated part of the thermosetting resin is evaluated by a water absorption method, the water absorption is in the range of 2 to 15%, preferably in the range of 3 to 10%.

The area of the unimpregnated portion of the prepreg by the ultrasonic flaw detection method is determined by the following method. Using an ultrasonic flaw detector (for example, SDS-3600: manufactured by Nippon Kraut Kramer Co., Ltd.), measurement is performed at a frequency of 5 Hz by the double transmission method. First, ultrasonic flaw detection is performed on a prepreg completely impregnated with a resin composition, and a value of amplification degree (dB) is set. Next, the partially impregnated prepreg is measured with the set amplification factor (dB), and a threshold value of 50% or less is defined as an unimpregnated portion. Then, the ratio of the threshold value of 50% or less is calculated with respect to the measured area, and the ratio of the unimpregnated portion is quantified.

The water absorption rate of the prepreg is determined by the following method. Cut the prepreg to 100 × 100 mm and measure the 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)

When the unimpregnated portion is less than the predetermined range in the above, the ventilation path of the reinforcing fiber layer may be insufficient, and if it exceeds the predetermined range, there is a high possibility that fluff is generated when the prepreg is cut. .

In the present invention, a prepreg formed by impregnating a thermosetting resin sheet on both sides of a reinforcing fiber substrate, the resin of the resin sheet is striped in the fiber direction inside the reinforcing fiber substrate, and in a lattice shape Or what has the impregnation part and the non-impregnation part formed in the diagonal grid | lattice form is preferable. In such a case, the impregnated portion and the non-impregnated portion are alternately present in the prepreg, and the ventilation path of the non-impregnated portion is secured, so that the deaeration can be sufficiently performed in the decompression step in the oven molding. Therefore, even a highly-prepared prepreg having an increased degree of impregnation can be obtained by providing a non-impregnated portion continuous with the resin-impregnated portion in a striped manner inside the prepreg, thereby obtaining a molded product with less voids.

The prepreg of the present invention, the reinforcing fiber content per unit area of those is preferably 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.

The reinforcing fiber for reinforcing fiber substrate used in the present invention is not particularly limited, and examples thereof include glass fiber, aramid fiber, carbon fiber, graphite fiber, boron fiber and the like. Among these, carbon fiber is preferable in terms of specific strength and specific 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, from the viewpoint of controlling the proportion of the unimpregnated portion of the partially impregnated prepreg, the fiber reinforced fabric used for partial impregnation is preferably a multiaxial fabric. The multiaxial woven fabric is a multiaxial stitch base material in which a reinforcing fiber base material is formed by laminating two or more layers in which carbon fiber bundles are arranged in parallel in a sheet shape, and the laminated body is integrated by stitch yarns or the like. 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. In the present invention, among the multiaxial woven fabrics, those having unevenness with a height of 0.02 to 0.1 mm in the thickness direction are particularly preferable.

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% by weight, 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, and if it exceeds 80% by weight, poor resin impregnation occurs. The resulting composite material can be highly voided.

As a thermosetting resin suitable for the present invention, the viscosity at 25 ° C. of the resin or resin composition is 5 × 10 ⁵ Pa · S or more, and the curing start temperature of the resin composition is in the range of 100 to 120 ° C. In addition, an epoxy resin composition having a viscosity (minimum viscosity) in the range of 0.1 to 2 Pa · S is desirable.

Examples of the epoxy resin composition include 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 a dicyandiamide curing agent (C). Is an epoxy resin composition containing, as an essential component, the viscosity of the resin composition at 25 ° C. is 5 × 10 ⁵ Pa · S or more, and the curing start temperature of the resin composition is in the range of 100 to 120 ° C. And an epoxy resin composition having a viscosity (minimum viscosity) in the range of 0.1 to 2 Pa · S.

The epoxy resin composition of the preferable aspect of this invention uses the liquid epoxy resin (A) whose viscosity in 25 degreeC is 100 Pa * S or more as an essential component. By blending this component (A), it is possible to impart appropriate tack and drape to the prepreg at room temperature. In a resin composition having a viscosity at 25 ° C. of less than 100 Pa · S, when a finely reinforced composite material is produced using a partially impregnated prepreg, the resin flows in the decompression step after lamination of the partially impregnated prepreg, and the unimpregnated reinforcement Since the ventilation path is blocked before the fiber portion is sufficiently decompressed, many internal voids may be generated after the thermoforming.

Specifically, as the liquid epoxy resin (A), for example, a glycidyl ether type epoxy resin obtained from a compound having a hydroxyl group in the molecule, a glycidylamine type epoxy resin obtained from a compound having an amino group in the molecule, a molecule A glycidyl ester type epoxy resin obtained from a compound having a carboxyl group in it, a cycloaliphatic epoxy resin obtained from a compound having an unsaturated bond in the molecule, or two or more types selected from these are mixed in the molecule An epoxy resin or the like 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 composition of the preferable aspect of this invention uses the epoxy resin (B) which is solid at 25 degreeC as an essential component. Such component (B) is used by being dissolved in the epoxy resin composition of the present invention, and in the decompression step near the room temperature of the partially impregnated prepreg, while increasing the viscosity of the epoxy resin composition and suppressing the resin fluidity, 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 of a preferred embodiment of the present invention 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 the epoxy resin composition of a preferred embodiment of the present invention, if necessary, in addition to the components (A), (B), and (C), organic particles such as rubber particles and thermoplastic resin particles, soluble thermoplastic One or more resins 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.

The epoxy resin composition according to a preferred embodiment of the present invention has a viscosity at 25 ° C. of 5 × 10 ⁵ Pa · S or more, the curing start temperature of the resin composition is in the range of 100 to 120 ° C., and The viscosity (minimum viscosity) at that time is in the range of 0.1 to 2 Pa · S. The viscosity at 25 ° C. is more preferably 7 × 10 ⁵ Pa · s or more. From the viewpoint of moldability, particularly impregnation into reinforcing fibers such as carbon fibers, the minimum viscosity is more preferably 0.1 to 1 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 Rheology Corporation), 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.

Hereinafter, an example of a method for producing a partially impregnated prepreg of the present invention and a fiber-reinforced composite material using the same will be described. In the present invention, first, the resin or the resin composition is applied onto a release paper by a reverse roll coater or a knife coater to form a sheet or film, and the obtained sheet or film is applied to both surfaces of the reinforcing fiber base. It can be produced by laminating, arranging, and impregnating a reinforcing fiber substrate with a resin or a resin composition by heating and pressing.

Here, the resin impregnated state is transferred from the resin sheet (including film) to the fiber base material as a method of causing the reinforcing fiber base material to have the impregnated portion and the non-impregnated portion in a striped, lattice-like or oblique lattice shape. There is a method of manufacturing by performing non-uniform pressurization. As a method of non-uniform pressing, a method using a substrate having slight unevenness, a method using a pressure plate subjected to slight unevenness processing, and a slight unevenness processing were performed in the case of continuous impregnation. A partially impregnated prepreg of a preferred embodiment in the present invention can be produced by a method using a roller (slit roller).

As the base material having slight unevenness, the reinforcing fiber base material preferably has unevenness with a height of 0.02 to 0.1 mm in the thickness direction. In a general woven fabric, the unevenness in the thickness direction is 0.02 mm or less. Therefore, as a method for providing the unevenness, it can be produced by overlapping adjacent reinforcing fibers. Moreover, as a roller which gave the slight uneven | corrugated process, the slit roller which has the unevenness | corrugation whose height is 0.02-0.1 mm on a surface is preferable.

If the impregnated portion and the non-impregnated portion are alternately present in the prepreg, and the ventilation path of the non-impregnated portion is secured, sufficient deaeration is possible in the decompression step in the oven molding. Therefore, even a high-weight prepreg with a high degree of impregnation can be obtained by forming an unimpregnated portion continuous with a resin-impregnated portion in a striped, lattice-like or oblique lattice shape inside the prepreg so that a molded product with less voids can be obtained. It becomes possible to obtain.

The fiber reinforced composite material of the present invention is obtained by laminating a plurality of the above partially impregnated prepregs to form a laminated body, covering the obtained laminated body with a back material (bagging bag), and then the inside at a temperature of 25 ° C. or lower. It can be produced by reducing the pressure and then heating and curing from the outside while maintaining the reduced pressure. Lamination or shaping may be performed by laminating a plurality of partially impregnated prepregs on a mold, or a plurality of partially impregnated prepregs may be wound around a mandrel. Heating is performed by an apparatus such as an autoclave, an oven, or a press.

It is preferable to perform the pressure reduction process in a bag on the conditions from which the viscosity of an epoxy resin composition will be 5 * 10 < ⁵ > Pa * s or more, for example. In view of handling the partially impregnated prepreg, the resin viscosity is preferably 5 × 10 ⁵ Pa · s or more at 25 ° C., but the temperature is controlled to 25 ° C. or less, and the viscosity of the epoxy resin composition is 5 × 10 ^5. You may choose the conditions used as Pa * s or more.

Moreover, it is preferable that a pressure reduction process is a vacuum degree -0.09 Mpa or less, and is heated up to hardening temperature, after depressurizing for 15 minutes or more. The pressure during decompression is best reduced to -0.1 MPa, but if the pressure is reduced to -0.09 MPa or less, the air present in the substrate can be sufficiently removed. If the pressure during decompression is greater than -0.09 MPa, that is, if the vacuum is not sufficiently secured, voids remain in the obtained molded product, and a good molded product cannot be obtained.

Further, when the temperature is raised from room temperature to the curing temperature, the temperature may be increased to a curing temperature at a constant rate of temperature increase, or the temperature may be maintained at an intermediate temperature for a certain period of time, and then increased to the curing temperature. Thus, in the case of step cure that is held for a certain period of time at an intermediate temperature, the condition that the epoxy resin composition is 10 to 25 ° C. lower than the curing start temperature and the viscosity of the epoxy resin composition is 3 Pa · s or less. It is good to choose. As the curing temperature, 120 to 150 ° C. is preferably used because of the characteristics of the dicyandiamide curing agent and the curing accelerator. A temperature increase rate of 1 to 10 ° C./min is preferably used. If it is less than 1 ° C./minute, the viscosity may not be lowered sufficiently, so that it may be difficult to impregnate the reinforcing fiber with the epoxy resin. On the other hand, if the temperature exceeds 10 ° C./minute, a temperature difference occurs in various portions of the reinforcing fibers, and a uniform cured product may not be obtained.

As described above, the preferred embodiment of the present invention is, as described above, controlling the viscosity of the epoxy resin composition at room temperature, increasing the viscosity of the resin to such an extent that the resin does not flow in the decompression step, and heating / curing around 100 ° C. In the temperature range, an epoxy resin composition having a sufficiently low viscosity is used, and the impregnation state of the epoxy resin composition into the reinforcing fiber base is controlled.

Hereinafter, the present invention will be described more specifically with reference to examples. 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 that the weight per unit area was 125 g / m ² , thereby producing a resin film. Carbon fiber multiaxial stitch base material made of “Tenax” (registered trademark) HTA-12K manufactured by Toho Tenax Co., Ltd. as a reinforcing fiber base material (stacked at an angle of 0/90, overlapping adjacent reinforcing fibers) Using a substrate having a surface roughness of about 0.04 mm, 450 g / m ² ), and the resin film is laminated on both upper and lower surfaces of the carbon fiber multiaxial fabric. Pressure was applied with a heated press at a surface pressure of 0.1 MPa for 40 seconds to obtain a prepreg having a resin content of 36% by weight.

A small piece of 100 × 100 mm was cut from the prepreg, and the small piece 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.

Further, the prepreg was measured by a double transmission method using an ultrasonic flaw detector (SDS-3600: manufactured by Nippon Kraut Kramer Co., Ltd.) at a frequency of 5 Hz and an amplification factor of 25 dB. The ratio of the threshold value of 50% or less was calculated with respect to the measured area, and the ratio of the non-impregnated portion of the prepreg resin was quantified.

The prepregs obtained as described above were laminated on an aluminum mold in plane symmetry, and the whole was bagged with a nylon bag, and the interior of the bag was vacuumed at -0.1 MPa for 15 minutes at 25 ° C. The pressure was reduced. Thereafter, while maintaining the reduced pressure, the mixture was heated to 90 ° C. at a temperature increase of 5 ° C./min and held at 90 ° C. for 30 minutes. Then, it heated at 130 degreeC with the temperature increase of 5 degree-C / min, and it hardened at 130 degreeC for 90 minutes, and produced the fiber reinforced composite material (molded object). 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 resin component (A), EPN-1138 (phenol novolak resin [manufactured by Asahi Kasei Epoxy Co., Ltd.): 62 parts by weight of viscosity at 25 ° C., 1,000 Pa · s, and as component (B), EP-1002 (bisphenol A type) Epoxy resin [manufactured by Japan Epoxy Resin Co., Ltd.]: 38 parts by weight of solid, 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.

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, the partially impregnated prepreg produced by pressing for 40 seconds with a press heated to 125 ° C. with a surface pressure of 0.1 MPa has a water absorption of 15%, and the unimpregnated part by the ultrasonic flaw detection method. The proportion of was 55%. And the void rate of the molded object produced by the said method using this partial impregnation prepreg was 0.5%. Fluff did not occur during prepreg cutting.

[Example 2]
Using the resin composition of Example 1, a partially impregnated prepreg was prepared by the same method as described above (however, the pressing temperature was 105 ° C. and the pressing was performed at a surface pressure of 0.1 MPa for 60 seconds). The water absorption of the obtained prepreg was 13%, and the unimpregnated ratio by ultrasonic flaw detection was 76%. The void ratio of the molded body produced by the above method using this prepreg was 0.4%. Fluff did not occur during prepreg cutting.

[Example 3]
Using the resin composition of Example 1, the same method as described above (however, using a concavo-convex press (step difference of 0.05 mm) without applying concavo-convex to the carbon fiber substrate at a press temperature of 125 ° C., the surface pressure was 0 A partially impregnated prepreg was prepared by pressurizing at 1 MPa for 40 seconds). The water absorption of the obtained prepreg was 3%, and the unimpregnated ratio by ultrasonic flaw detection was 33%. The void ratio of the molded body produced by the above method using this prepreg was 0.6%. Fluff did not occur during prepreg cutting.

[Example 4]
As component (A), EP-604 (tetraglycidyldiaminodiphenylmethane: manufactured by Japan Epoxy Resin Co., Ltd .: viscosity of 25 Pa at 200 Pa · s) is 40 parts by weight, and as component (B), EP-1002 (bisphenol A type epoxy resin) : Japan Epoxy Resin Co., Ltd .: solid) 30 parts by weight, EP-1001 (bisphenol A type epoxy resin: solid) 30 parts by weight, and as component (C), 5 parts by weight of dicyandiamide, and further a curing accelerator (D ), 3 parts by weight of 3- (3,4-dichlorophenyl) -1,1-dimethylurea 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 8 × 10 ⁵ Pa · s, and the minimum viscosity of the resin composition was 0.8 Pa · s (curing start temperature 106 ° C.).

The water absorption of the partially impregnated prepreg produced using this resin composition by the same method as in Example 1 was 12%, and the unimpregnated ratio by ultrasonic flaw detection was 75%. And the void rate of the molded object produced by the said method using this partial impregnation prepreg was 0.5%. Fuzz was hardly generated during the prepreg cut.

[Comparative Example 1]
Using the resin composition of Example 1, a partially impregnated prepreg was prepared in the same manner as in Example 1 (however, pressing was performed at a pressing temperature of 105 ° C. and pressing with a surface pressure of 0.1 MPa for 40 seconds). This partially impregnated prepreg had a water absorption of 26%, and the unimpregnated ratio by ultrasonic flaw detection was 95%. And the void rate of the molded object produced by the said method using this partial impregnation prepreg was 0.5%. Fluff that did not occur in Example 1 occurred during prepreg cutting.

[Comparative Example 2]
Using the resin composition of Example 1, a partially impregnated prepreg was prepared in the same manner as in Example 1. Next, using this prepreg, under the atmosphere of 35 ° C. (viscosity of the resin composition at 35 ° C. was 3 × 10 ⁴ Pa · s), stacking, bagging, and reducing the pressure inside the bag, A molded body was produced in the same manner as in Example 1. The obtained molded body had many voids and the void ratio was 2.5%.

[Comparative Example 3]
As component (A), EPN-1138 (phenol novolac resin: viscosity at 25 ° C., 1,000 Pa · s) is 70 parts by weight, and EP-828 (bisphenol A type epoxy resin: Japan epoxy resin not applicable to component (A)) 10 parts by weight, viscosity (15 Pa · s at 25 ° C.) as component (B), 20 parts by weight of EP-1002 (bisphenol A type epoxy resin: solid), 5 parts by weight of dicyandiamide as component (C), Further, 3 parts by weight of 3- (3,4-dichlorophenyl) -1,1-dimethylurea was used as the curing accelerator (D).

A mixture of component (A), EP-828 and component (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.).

The water absorption of the partially impregnated prepreg produced using this resin composition by the same method as in Example 1 was 1% by weight, and the proportion of the unimpregnated part by ultrasonic flaw detection was 15%. And the molded object produced by the said method using this prepreg had many voids, and the void rate was 2.0%. Compared with those of Examples 1 and 2, the void ratio was high.

Claims (11)

A prepreg in which a thermosetting resin sheet is partially impregnated on both sides of a reinforcing fiber substrate, and an unimpregnated portion continuous with a resin-impregnated portion inside the prepreg by non-uniform pressure during transfer of the resin sheet Is formed in a stripe shape, a lattice shape, or an oblique lattice shape, and the ratio of the unimpregnated portion is a range of 25% or more and less than 80% of the area of the reinforcing fiber base when evaluated by an ultrasonic flaw detection method. And a partially impregnated prepreg having a water absorption rate of 2 to 15% when evaluated by a water absorption method. 2. The reinforced fiber base material is a multiaxial stitch base material in which two or more layers in which carbon fiber bundles are arranged in parallel in a sheet shape are laminated, and these layers are integrated by stitch yarns. The partially impregnated prepreg as described. The thermosetting resin sheet comprises a liquid epoxy resin (A) having a viscosity of 100 Pa · S or higher at 25 ° C., an epoxy resin (B) that is solid at 25 ° C., and a dicyandiamide curing agent (C). The partially impregnated prepreg according to claim 1, comprising an epoxy resin composition contained as an essential component. Overlapping a thermosetting resin sheet on both surfaces of the reinforcing fiber substrate placed, then claim a reinforcing fiber base and the resin sheet by applying uneven pressure Ru allowed unevenly resin-impregnated reinforcing fiber substrate A method for producing the partially impregnated prepreg according to 1 . When pressurizing the reinforcing fiber base and the thermosetting resin sheet, the reinforcing fiber base is pressed using a base having an unevenness of 0.02 to 0.1 mm in the thickness direction. 4. The method for producing a partially impregnated prepreg according to 4. The partial impregnation according to claim 4, wherein when the reinforcing fiber base and the thermosetting resin sheet are pressed, the surface is pressed non-uniformly using a slit roller having an unevenness of 0.02 to 0.1 mm on the surface. Prepreg manufacturing method. The thermosetting resin sheet comprises a liquid epoxy resin (A) having a viscosity of 100 Pa · S or higher at 25 ° C., an epoxy resin (B) that is solid at 25 ° C., and a dicyandiamide curing agent (C). The method for producing a partially impregnated prepreg according to claim 4, comprising an epoxy resin composition contained as an essential component. A plurality of partially impregnated prepregs according to claim 1 are laminated to form a laminated body, and the obtained laminated body is covered with a back material, and then the inside thereof is decompressed at a temperature of 25 ° C. or lower, and then the decompression is maintained. A method for producing a fiber-reinforced composite material, wherein the thermosetting resin is impregnated into the inside of the reinforcing fiber base and heated by heating from the outside. The thermosetting resin sheet comprises a liquid epoxy resin (A) having a viscosity of 100 Pa · S or higher at 25 ° C., an epoxy resin (B) that is solid at 25 ° C., and a dicyandiamide curing agent (C). The method for producing a fiber-reinforced composite material according to claim 8, comprising an epoxy resin composition contained as an essential component. The fiber according to claim 9, wherein the pressure reduction is performed in a range where the viscosity of the epoxy resin composition is 5 × 10 ⁵ Pa · S or more, 15 minutes or more, and a vacuum degree is −0.09 MPa or less. A method for producing a reinforced composite material. The fiber according to claim 9 or 10, wherein the heating is performed by a step curing method in which the heating is held for 10 hours at a temperature lower by 10 to 25 ° C than the curing start temperature of the epoxy resin composition and then raised to the curing temperature. A method for producing a reinforced composite material.