JP2018122549A - Cover film sticking prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg so that tackiness of a surface of the prepreg is adjusted to make lamination workability good without changing a manufacturing condition.SOLUTION: There is provided a cover film sticking prepreg to which a cover film is stuck so that 40-70% of a surface area of the prepreg is brought into contact with at least one surface obtained by impregnating a reinforced-fiber sheet formed of a reinforcement fiber with a thermosetting resin composition, where a complex viscosity ηat a temperature of 40°C of the thermosetting resin composition is in a range of 1.0×10to 1.0×10Pa s.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cover film-attached prepreg that is used when manufacturing a fiber-reinforced composite molded article and is adjusted to have tackiness suitable for molding workability.

  Conventionally, fiber-reinforced composite materials made of carbon fiber, glass fiber, and other reinforcing fibers and epoxy resins, phenol resins, and other thermosetting resins are lightweight, yet have mechanical properties such as strength and rigidity, heat resistance, and corrosion resistance. It has been applied to many fields such as aviation / space, automobiles, rail cars, ships, civil engineering and sports equipment. Especially in applications where high performance is required, fiber reinforced composite materials using continuous reinforcing fibers are used, carbon fibers with excellent specific strength and specific elastic modulus are used as reinforcing fibers, and thermosetting is used as a matrix resin. Of these, many epoxy resins are used that are particularly excellent in adhesion to carbon fibers.

  In the production of a fiber-reinforced composite material, a prepreg, which is an intermediate substrate in which a reinforcing fiber is aligned in one direction, or a sheet-like material such as a woven fabric or a nonwoven fabric is impregnated with a thermosetting resin, is often used. When producing a molded product using a prepreg, the desired molded product is generally obtained by laminating an arbitrary number of prepregs on a mold and then curing and molding under pressure and heating. Particularly in the laminating process, the position of the prepreg surface is fixed by adhering the mold, the prepreg, and the prepregs by the adhesive force (hereinafter referred to as tack) on the prepreg surface. Is important.

  Tack is required in the prepreg lamination process, but if the tack strength is not optimized, workability during lamination may be affected. For example, if the tack of the prepreg is weak, the prepreg from the mold or the laminated prepregs may be easily peeled off during operation. Also, if the tack of the prepreg is strong, even if you try to peel off the prepreg once laminated to adjust the lamination position and re-lamination, it can not be peeled off because the prepregs are firmly attached to each other, forcibly removed However, the structure of the prepreg is deformed from the original shape, and re-stacking becomes impossible. Therefore, in order to improve the molding workability, it is necessary to appropriately adjust the tack of the prepreg surface.

  As a general method of adjusting the tack of the prepreg surface, which has already been determined by the reinforcing fiber and the resin composition, there is a method of adjusting the tack by adjusting the amount of resin remaining on the prepreg surface in the prepreg manufacturing stage. This is a method that utilizes the property that the prepreg tack becomes stronger as the amount of resin on the prepreg surface increases. However, since this method leaves the resin on the surface, the amount of the resin impregnated into the reinforcing fiber layer is reduced, fluffing occurs in the prepreg manufacturing stage, and voids are generated in the final molded product, causing deterioration of mechanical properties. There is a risk that.

  In this way, changing the prepreg manufacturing conditions to adjust the prepreg tackiness may affect the properties of the prepreg and the molded product, so the tack is adjusted without changing the prepreg manufacturing conditions. It is desirable.

  As a method of adjusting the tack of the prepreg surface in a state where the prepreg manufacturing conditions are established, a method of using a cover film is conceivable. Patent Document 1 describes that a resin is held (that is, a strong tack can be obtained) by attaching a cover film stretched at a constant tension to the prepreg surface and bringing the film and the prepreg into contact with each other (FIG. 1). This is the idea that the surface tension acts on the resin when the cover film and the resin come into contact with each other, and the resin is held. However, if the contact area between the cover film and the resin is adjusted as shown in FIG. It should be possible to adjust the amount of resin that is held, and thus to adjust the tack. Regarding such adjustment of the resin amount, in Patent Documents 2 and 3, the contact area between the resin and the film is changed by changing the area of the convex portion of the embossed film, and the resin amount held on the prepreg surface is adjusted. Yes.

JP-A-9-254299 JP 2014-15567 A JP 2012-111957 A

  However, Patent Documents 2 and 3 aim at securing a deaeration path between the layers in vacuum bag molding, and the tack when satisfying the contact area shown in the claims is not specifically described. The controllability is only touched qualitatively. Further, there is no regulation on the resin viscosity that affects the strength of tack, and no consideration is given to the case where tack is not obtained even if the resin is held on the surface depending on the resin viscosity.

  The present invention has been made to solve such conventional problems, and in the prepregs for which the reinforcing fiber and the resin composition have already been determined, the prepreg surface tack is excellent without changing the production conditions. It is in providing the prepreg adjusted so that it may become.

The present invention employs the following means in order to solve such problems. That is, a cover film-attached prepreg in which a cover film in which 40 to 70% of the surface area of the prepreg is in contact with at least one surface of a prepreg obtained by impregnating a reinforcing fiber sheet made of reinforcing fibers with a thermosetting resin composition And it is a cover film sticking prepreg whose complex viscosity eta ^* in the temperature of 40 degreeC of a thermosetting resin composition is the range of 1.0 * 10 < ^{2 >} -1.0 * 10 < ^{4 >} Pa * s.

  Even a prepreg whose manufacturing conditions have already been established is that a prepreg with good molding workability can be obtained by placing the cover film for 12 hours under the conditions of a temperature of 23 ° C. and a relative humidity of 50%.

It is a schematic diagram which shows a mode that resin does not sink and is hold | maintained even if time passes by sticking of a cover film. It is a schematic diagram which shows a mode that the resin amount which remains on the surface was adjusted by adjusting the contact area of a cover film. It is a schematic diagram which shows the mode of the cross prepreg laminated | stacked and affixed on the aluminum flat plate. FIG. 4 is a schematic diagram showing a state where one of the two prepregs in FIG. 3 is peeled off. It is a schematic diagram which shows a mode when the prepreg peeled in FIG. 4 is affixed again.

  The reinforcing fibers constituting the reinforcing fiber sheet of the present invention are composed of continuous fibers, and various types can be used according to the purpose of use of the fiber-reinforced composite material. Examples include carbon fiber, graphite fiber, aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, glass fiber, etc. Among them, a fiber-reinforced composite material that is lightweight and has high performance and excellent mechanical properties can be obtained. Carbon fiber is desirable.

  Specific examples of the carbon fiber include acrylic, pitch, and rayon carbon fibers, and acrylic carbon fibers having a particularly high tensile strength are preferably used.

  Such an acrylic carbon fiber can be produced, for example, through the following steps. A spinning dope containing polyacrylonitrile obtained from a monomer containing acrylonitrile as a main component is spun by a wet spinning method, a dry wet spinning method, a dry spinning method, or a melt spinning method. The spun coagulated yarn can be made into a precursor through a spinning process, and then carbon fiber can be obtained through processes such as flame resistance and carbonization.

  Various forms of the reinforcing fiber sheet of the present invention can be used depending on the purpose of use of the fiber-reinforced composite material. For example, reinforced fibers arranged in one direction, woven fabrics, knits, braids and mats can be used. Among them, considering that the prepregs once laminated are peeled in order to correct the lamination position and are re-laminated, a fabric having a woven shape in which the prepreg is less likely to tear between the fibers even when a load is applied during peeling is desirable.

  As the thermosetting resin constituting the thermosetting resin composition of the present invention, various resins can be used depending on the purpose of use of the fiber reinforced composite material. For example, an epoxy resin, a polyester resin, a polyimide resin, a phenol resin, and the like can be given. Among them, an epoxy resin is desirable because of excellent mechanical properties and adhesiveness with reinforcing fibers. Here, the epoxy resin means a compound having two or more glycidyl groups in one molecule.

  Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, bisphenol type epoxy resins such as bisphenol S type epoxy resins, and brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether. , Epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, epoxy resins having a dicyclopentadiene skeleton, novolac epoxy resins such as phenol novolac epoxy resins and cresol novolac epoxy resins, N, N, O-triglycidyl -M-aminophenol, N, N, O-triglycidyl-p-aminophenol, N, N, O-triglycidyl-4-amino-3-methylphenol, N, N, N ' N′-tetraglycidyl-4,4′-methylenedianiline, N, N, N ′, N′-tetraglycidyl-2,2′-diethyl-4,4′-methylenedianiline, N, N, N ′ Glycidylamine type epoxy resins such as N, N'-tetraglycidyl-m-xylylenediamine, N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, resorcin diglycidyl ether, triglycidyl isocyanurate, etc. be able to. Among these, in the case of aviation, spacecraft applications, etc., it is preferable to include a glycidylamine type epoxy resin from which a cured product having a high glass transition temperature and elastic modulus can be obtained.

  These epoxy resins may be used alone or in combination as appropriate. Mixing an epoxy resin exhibiting fluidity at an arbitrary temperature and an epoxy resin not exhibiting fluidity at an arbitrary temperature is effective in controlling the fluidity of the matrix resin when the resulting prepreg is thermoset. For example, if the fluidity shown before the matrix resin is gelled at the time of thermosetting, the fiber volume content is predetermined due to disturbance in the orientation of the reinforcing fibers or the matrix resin flowing out of the system. As a result, the mechanical properties of the resulting fiber-reinforced composite material may be reduced. Further, combining a plurality of epoxy resins exhibiting various viscoelastic behaviors at an arbitrary temperature is also effective for making the tackiness and draping properties of the obtained prepreg appropriate.

  In the thermosetting resin composition of the present invention, a monoepoxy compound having only one epoxy group in one molecule or an alicyclic ring as long as the heat resistance and mechanical properties are not significantly reduced. A formula epoxy resin or the like can be appropriately blended.

  Curing agents that can cure these epoxy resins include aliphatic polyamines, aromatic polyamines, dicyandiamides, polycarboxylic acids, polycarboxylic acid hydrazides, acid anhydrides, polymercaptans, polyphenols, and the like compounds that undergo a quantitative reaction. , Imidazole, Lewis acid complex, and onium salts. When a compound that undergoes a stoichiometric reaction is used, a curing accelerator such as imidazole, Lewis acid complex, onium salt, phosphine, and the like may be blended. Aromatic polyamines are most suitable for the purpose of producing structural materials with excellent heat resistance. Among them, 3,3′-diaminodiphenyl sulfone and 4,4′-diaminodiphenyl sulfone are heat resistant and elastic. A cured product having an excellent rate can be obtained, and the linear expansion coefficient and the decrease in heat resistance due to moisture absorption are small, so that it can be preferably used.

  In the thermosetting resin composition of the present invention, a thermoplastic resin may be blended in the resin composition in order to impart viscosity control and toughness without impairing the heat resistance and elastic modulus of the resulting fiber-reinforced composite material. I can do it. As such thermoplastic resins, for example, resins belonging to so-called engineering plastics such as polyimide, polyetherimide, polysulfone, polyethersulfone, polyamide, polyamideimide, polyarylene oxide, polyetherketone, polyetherethersulfone are preferably used. It is done. These thermoplastic resins may be used alone or in combination as appropriate. Among these, polyethersulfone can be preferably used because it can impart toughness without deteriorating the heat resistance and mechanical properties of the resulting fiber-reinforced composite material.

  The thermosetting resin composition used in the present invention can be produced by various known methods. For example, the method of kneading each component with a kneader is mentioned. Moreover, you may knead | mix each component using a biaxial extruder.

The complex viscosity η ^* of the thermosetting resin composition used in the prepreg of the present invention is 1.0 × 10 ^{2 to} 1.0 × 10 ⁴ Pa · s at a temperature of 40 ° C., preferably 1 The range is from 5 × 10 ^{2 to} 7.5 × 10 ³ , particularly preferably from 2.0 × 10 ^{2 to} 5.0 × 10 ³ . If the value is larger than this range, the thermosetting resin composition becomes too hard, so that the tackiness of the prepreg becomes almost zero at the time of production, and the moldability is lowered and the moldability is deteriorated. On the other hand, if the value is smaller than this range, the tack of the prepreg becomes large, it becomes difficult to peel off the prepreg, and the tack is lowered in a short time when left at room temperature. The complex viscosity η ^* of the thermosetting resin composition at a temperature of 40 ° C. is obtained by using a dynamic viscoelastic device ARES-2KFRTN1-FCO-STD (manufactured by TA Instruments). Using a parallel plate of 40 mm in diameter as the measurement jig, set the thermosetting resin composition so that the distance between the upper and lower jigs is 1 mm, and then measure the temperature in torsion mode (measurement frequency: 0.5 Hz). It is a value obtained by measuring the range of 30 to 140 ° C. at a temperature rising rate of 1.5 ° C./min.

  The prepreg of the present invention can be produced by various known methods. For example, the matrix resin is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, methanol, and the like to lower the viscosity, and the wet method in which the reinforcing fiber is impregnated, or the matrix resin is heated to lower the viscosity without using the organic solvent, A prepreg can be produced by a method such as a hot melt method for impregnating reinforcing fibers.

  In the wet method, the reinforced fiber is pulled up after being immersed in a liquid containing a matrix resin, and an organic solvent is evaporated using an oven or the like to obtain a prepreg.

  In the hot melt method, a matrix resin whose viscosity has been reduced by heating is impregnated directly into a reinforcing fiber, or a release paper sheet with a resin film once coated with a matrix resin on a release paper (hereinafter referred to as “resin”). The film may be referred to as “film” first), then a resin film is laminated on the reinforcing fiber side from both sides or one side of the reinforcing fiber, and the reinforcing fiber is impregnated with the matrix resin by heating and pressing. .

  The method for producing the prepreg of the present invention is preferably a hot melt method in which the reinforcing fibers are impregnated with a matrix resin without using an organic solvent, since substantially no organic solvent remains in the prepreg.

  In the prepreg of the present invention, the content of the thermosetting resin composition in the prepreg is preferably 20 to 50% by mass, more preferably 30 to 50% by mass, and particularly preferably 35 to 45%. Range. By adjusting to this range, a prepreg having a light weight and appropriate tack can be obtained. When the resin content falls below this range, the surface resin amount decreases, and the tack value at the production stage becomes almost zero. On the other hand, when this range is exceeded, the mass of the material itself increases, and the value of the prepreg that is required to be lightweight decreases.

  The material of the cover film used for the prepreg of the present invention is not particularly limited, but a synthetic resin film is desirable. For example, polyethylene, polypropylene, polyvinyl chloride, polyester and the like. Among these, polyethylene is preferably used because it is excellent in releasability and processability and is inexpensive.

  The surface shape of the cover film includes a flat surface with no irregularities on the surface and an embossed shape with irregularities on the surface, which are appropriately selected and used depending on the purpose of use. In the prepreg of the present invention, the contact area between the prepreg surface and the cover film is controlled, and the contact area varies depending on the pressing pressure and the unevenness of the cover film. In particular, when the unevenness of the cover film is used, it is possible to preliminarily specify the upper limit value of the contact area, which is suitable for keeping the contact area within the scope of this project. preferable.

  Although there is no restriction | limiting in particular in the thickness of a cover film, 20 micrometers or more are desirable. When the thickness is less than 20 μm, the strength of the cover film is lowered, and there is a concern that the cover film may be broken during handling of the prepreg.

  The prepreg of the present invention has a cover film attached to at least one surface. For example, a cover film may be attached to one surface of one side and the other surface may be a prepreg only, but the surface on which tack is adjusted is limited to the surface where the cover film and the prepreg are in contact. This is because the tack is held by the surface tension of the resin in contact with the film, and the tack can be adjusted by adjusting the contact area between the cover film and the prepreg.

  In the prepreg of the present invention, the contact area between the surface of the prepreg and the cover film is adjusted to 40 to 70% of the surface area of the prepreg, preferably in the range of 45 to 65%, particularly preferably in the range of 50 to 60%. It has been adjusted. By adjusting to this range, the surface resin amount suitable for molding workability can be maintained. The contact area between the prepreg surface and the cover film is determined by the pressing pressure of the film. The contact area increases with increasing film pressing pressure. Further, if the surface shape of the film is uneven, the film surface that comes into contact with the prepreg becomes a convex portion of the cover film, so that the contact area can be changed by changing the convex portion area of the film.

  The prepreg of the present invention is excellent in molding workability, particularly sticking property and re-lamination property, 12 hours after the cover film is pasted. Specifically, after applying a linear pressure of 0.5 kgf / cm from the top of the two prepregs stacked on the metal flat plate and pasting the metal flat plate, the prepreg and the prepregs, the metal flat plate is made parallel to the direction of gravity. Even if left for 10 minutes, the prepreg has a sticking property that does not peel off from the metal flat plate due to its own weight, and the fiber orientation in the in-plane direction of the prepreg and the prepreg attachment after the two prepregs are peeled off The fiber orientation angle difference in the in-plane direction before application is within 3 ° and can be peeled off without causing defects that did not exist in the prepreg before application. It is a prepreg that does not occur. The fiber orientation angle difference here is a value indicating how many degrees the fiber orientation angle after the prepregs are peeled off when the fiber orientation angle before application is set as a reference (0 °). It is. If the fiber orientation angle is within 3 °, there will be no difference in the physical properties of the molded product. In addition, the term “defect” as used herein refers to a visually observable prepreg component that did not exist but was generated in the prepreg by an external force. The gap formed between the fibers, the fiber tearing, the prepreg surface Such as ridges and irregularities. It is assumed that wrinkles at the time of re-lamination will occur when the prepreg is extended by forcefully peeling off the bonded prepreg, even though the prepreg is peeled off. When is suitable, the prepreg does not stretch and wrinkles do not occur.

  The prepreg of the present invention is a prepreg in which the surface tack is adjusted without changing the production conditions, and therefore, an improvement effect of molding workability can be obtained without affecting the quality and physical properties of the prepreg. , Primary structural members such as tail and floor beams, secondary structural members such as flaps, ailerons, cowls, fairings and interior materials, rocket motor cases and satellite structure materials, automobiles, ships and railway vehicles It can be suitably used for a wide range of applications such as a computer structure such as a structural material of a moving body such as a building material, a blade of a windmill, an IC tray or a casing (housing) of a notebook computer.

  Hereinafter, specific examples and comparative examples of the present invention will be described.

(Manufacture of prepreg)
The reinforcing fiber sheet used for the prepreg is a plain woven fabric made of carbon fiber “TORAYCA (registered trademark)” T400HB-6K manufactured by Toray Industries, Inc. The thermosetting resin composition used was an epoxy resin in which tetraglycidyldiaminodiphenylmethane, bisphenol A type epoxy resin, bisphenol F type epoxy resin were mixed, polyethersulfone as a thermoplastic resin, and 4,4 as a curing agent. A resin composition mixed with '-diaminodiphenylsulfone was used. At this time, two types of resin compositions (resin composition 1 and resin composition 2) having different viscosities were produced by changing the blending ratio of the epoxy resin, the curing agent, and the thermoplastic resin.

A hot melt method was used for producing the prepreg. First, a thermosetting resin composition was coated on a release paper to prepare a resin film having a predetermined resin basis weight. This resin film was layered from both sides of the reinforcing fiber and impregnated with the resin composition while being heated and pressed to prepare a prepreg. The resin content of the prepared prepreg is 40% by mass, and the basis weight of the prepreg is 475 g / m ² . A white polyethylene embossed film having a substrate thickness of 50 μm was attached to the prepreg while applying a pressing pressure of 1 to 5 kgf / cm ² .

(Measurement method of complex viscosity of resin)
For measuring the complex viscosity η ^* of the resin composition, a dynamic viscoelastic device ARES-2KFRTN1-FCO-STD (manufactured by TA Instruments) was used. A constant viscosity (65%) was applied to the resin composition, and the complex viscosity was measured when the temperature was increased from 40 ° C. to 130 ° C. at 1.5 ° C./min while applying torque at a cycle of 3.14 rad / s. . The complex viscosity of the resin composition at 40 ° C. was 2.0 × 10 ² Pa · s for the resin composition 1 and 3.6 × 10 ³ Pa · s for the resin composition 2.

(Calculation of contact area)
The contact area between the resin on the prepreg surface and the embossed film was determined by image analysis. First, a portion of 10 cm in the width direction and 10 cm in the longitudinal direction was cut out from the manufactured prepreg sheet to obtain a sample. The surface of the sample with the embossed film attached is scanned with a copier (Canon C5250F) at a resolution of 300 x 300 dpi, converted into a digital image (extension: JPEG), and image analysis software (free software) After importing into “JTrim”), for the 3 cm long and 3 cm wide area in the center of the sample, the area where the embossed film and prepreg are attached is black, and the area where it is not attached is white, with a threshold value of 150-170. The black area was calculated in the software. In the black and white image, the ratio of the black area to the total area of the prepreg was calculated as the contact area by the following formula (1).

Contact area (%) = (black part area) / (total prepreg area) × 100 Formula (1)
(Evaluation of molding workability)
The molding workability was evaluated by the prepreg attachment property and the relaminating property 12 hours after the embossing film was applied. Two prepreg samples 10 cm long and 10 cm wide were cut out from the manufactured prepreg at room temperature of 25 ° C. and 50% relative humidity, placed on an aluminum flat plate, and then 5 kg of an iron cylindrical mandrel was placed on the prepreg. By making it reciprocate 4 times, it stuck so that two prepregs might be laminated | stacked on the aluminum flat plate. A straight line was drawn with an oil-based pen along the unbent yarn bundle at a position of 5 cm in length of the prepreg (FIG. 3). At this time, a straight line was drawn up to the aluminum flat plate outside the sample. Here, a line written on the surface of the prepreg was defined as a line A. The aluminum flat plate was set up vertically with respect to the floor surface, and was left for 10 minutes so that the flat plate was parallel to the direction of gravity, and it was examined whether it peeled off. Thereafter, the two bonded prepregs are peeled off from the aluminum flat plate by hand, one side parallel to the line A between the prepregs is peeled off by 1 cm by hand, and then each peeled prepreg end portion is a universal testing machine manufactured by Orientec Co., Ltd. Fixed with a Tensilon RTE-1210 ”chuck and peeled off at a displacement rate of 150 mm / min until the sticking part was 1 cm (high sticking ability required to peel off as much as necessary) (In this case, the prepreg expands and the line A is distorted from a straight line to a curved line). Then, it bonded again by the above-mentioned method (FIGS. 4 and 5). At this time, bonding was performed so that the straight line written on the aluminum flat plate and the line A were connected. A straight line was written on the surface of the prepreg bonded again so as to connect the straight line written on the aluminum flat plate (here, the straight line written on the prepreg surface was defined as line B), and the deviation from the line A was observed. The point on line A where the deviation from line B is the largest and the end point of line B closer to that point are connected by a straight line (this is defined as line C), and the acute angle formed by line B and line C is measured with a protractor. . The difference in fiber orientation angle before and after peeling this angle was defined as θ (FIG. 5). Further, it was examined whether wrinkles were generated on the prepreg surface when pasted again.

Example 1
In the manufacture of a prepreg using the resin composition 1, a prepreg having a contact area between the embossed film and the prepreg adjusted to 70% was prepared by attaching the embossed film at a pressing pressure of 5 kgf / cm ² . When the prepreg was evaluated for the prepreg 12 hours after the embossing film was stuck, the prepreg was not peeled off from the aluminum flat plate and showed good stickiness. Moreover, when the re-lamination property was evaluated, the difference θ between the fiber orientation angles in the in-plane direction before and after peeling was 2 °, no defect was generated, and no wrinkles were generated when pasted again. Restackability was demonstrated.

(Example 2)
A prepreg was prepared in the same manner as in Example 1 except that the embossed film was attached at a pressing pressure of 2 kgf / cm ² , and the contact area between the embossed film and the prepreg was adjusted to 40%. When the stickiness was evaluated for the prepreg 12 hours after the embossing film was stuck, the prepreg was not peeled off from the aluminum flat plate in the same manner as in Example 1 and showed good stickiness. Further, when the re-lamination property was evaluated, the prepregs can be peeled off more easily than in Example 1, the difference θ between the fiber orientation angles in the in-plane direction before and after peeling is 1 °, and no defects have occurred. In addition, it showed a good re-lamination property with no wrinkles when bonded again.

(Example 3)
In the production of the prepreg using the resin composition 2, the contact area between the embossed film and the prepreg was adjusted to 70% by attaching the embossed film at a pressing pressure of 5 kgf / cm ² . When the prepreg was evaluated for the prepreg 12 hours after the embossing film was stuck, the prepreg was not peeled off from the aluminum flat plate and showed good stickiness. Moreover, when the re-lamination property was evaluated, the difference θ between the fiber orientation angles in the in-plane direction before and after peeling was 1 °, no defects were generated, and no wrinkles were generated when pasted again. Restackability was demonstrated.

Example 4
A prepreg was prepared in the same manner as in Example 3 except that the embossed film was attached at a pressing pressure of 2 kgf / cm ² , and the contact area between the embossed film and the prepreg was adjusted to 40%. When the stickiness was evaluated for the prepreg 12 hours after the embossing film was stuck, the prepreg was not peeled off from the aluminum flat plate as in Example 3, and showed good stickiness. Moreover, when the re-lamination property was evaluated, the prepregs can be peeled off more easily than in Example 3, and the difference θ between the fiber orientation angles in the in-plane direction before and after peeling is 0.5 °, and defects are generated. It showed good re-lamination properties without wrinkling when it was bonded again.

(Comparative Example 1)
A prepreg was prepared in the same manner as in Example 1 except that the embossed film was attached at a pressing pressure of 1 kgf / cm ² , and the contact area between the embossed film and the prepreg was adjusted to 10%. When the sticking property of this prepreg was evaluated, the end portion of the prepreg started to peel from the aluminum flat plate after 5 minutes, and the prepreg completely peeled off after 8 minutes.

(Comparative Example 2)
In the production of the prepreg using the resin composition 1, the contact area was adjusted to 80% by attaching a polyethylene film having no irregularities in place of the embossed film at a pressing pressure of 3 kgf / cm ² . When stickability was evaluated about this prepreg, the prepreg was not peeled off from the aluminum flat plate similarly to Examples 1-4, and showed favorable stickability. On the other hand, when the restackability was evaluated, it was difficult to peel the prepregs from Example 1, and the fiber orientation angle difference in the in-plane direction before and after peeling was 5 °. occured.

(Comparative Example 3)
A prepreg was prepared in the same manner as in Example 3 except that the embossed film was attached at a pressing pressure of 1 kgf / cm ² , and the contact area between the embossed film and the prepreg was adjusted to 10%. When the sticking property of this prepreg was evaluated, the end of the prepreg started to peel from the aluminum flat plate after 3 minutes, and the prepreg was completely peeled off after 6 minutes.

(Comparative Example 4)
In the production of the prepreg using the resin composition 2, the contact area was adjusted to 80% by attaching a polyethylene film without unevenness in place of the embossed film at a pressing pressure of 3 kgf / cm ² . When stickability was evaluated about this prepreg, the prepreg was not peeled off from the aluminum flat plate similarly to Examples 1-4, and showed favorable stickability. On the other hand, when the restackability was evaluated, the prepregs were more difficult to peel off than Example 3, and the fiber orientation angle difference in the in-plane direction before and after peeling was 4 °. occured.

(Comparative Example 5)
A resin composition described in Example 1 of Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-15567) was prepared as a resin composition. The complex viscosity of the resin composition at 40 ° C. of this resin composition was 2.5 × 10 ⁴ Pa · s. Using this resin composition, a prepreg was produced in the same manner as in Example 1, and the contact area between the embossed film and the prepreg was adjusted to 70%. When the prepreg 12 hours after sticking the embossed film was evaluated for stickability, the end of the prepreg started to peel off from the aluminum flat plate immediately after sticking, and the prepreg was completely peeled off after 1 minute.

(Comparative Example 6)
As a resin composition, a resin composition of composition A described in Examples of Patent Document 3 (Japanese Patent Laid-Open No. 2012-111957) was prepared. The complex viscosity of the resin composition at 40 ° C. of this resin composition was 5.6 × 10 ¹ Pa · s. Using this resin composition, a prepreg was produced in the same manner as in Example 2, and the contact area between the embossed film and the prepreg was adjusted to 40%. When the prepreg was evaluated for prepregs 12 hours after sticking the embossed film, the prepreg was not peeled off from the aluminum flat plate and showed good stickiness, but when evaluating the re-lamination property, the prepregs were carried out. It was more difficult to peel off than Example 1, and the fiber orientation angle difference in the in-plane direction before and after peeling was 5 °, and wrinkles were generated when pasted again.

According to the present invention, in a prepreg obtained by impregnating a reinforcing fiber sheet composed of reinforcing fibers with a resin composition composed of a thermosetting resin, a cover film is attached to at least one surface, and the surface of the prepreg Is a cover film-attached prepreg in which the contact area of the cover film is in the range of 40 to 70% of the surface area of the prepreg, and the complex viscosity η ^{* at} a temperature of 40 ° C. of the resin composition constituting the prepreg is 1.0 × 10 ^2. With the prepreg in the range of ˜1.0 × 10 ⁴ Pa · s, a prepreg having good molding workability (sticking property, re-lamination property) is obtained 12 hours after the cover film is pasted.

DESCRIPTION OF SYMBOLS 1 ... Prepreg layer 2 ... Resin of prepreg surface 3 ... Cover film 4 ... Contact surface of resin of prepreg surface and cover film 5 ... By resin of prepreg surface and cover film not contacting Resulting space 6 ... Aluminum flat plate 7 ... Two prepregs bonded together 8 ... Line A before peeling
9 ... one prepreg peeled off 10 ... line A after peeling
11 ... Two prepregs bonded together 12 ... Line B
13 ... Line C

Claims (4)

This is a cover film-attached prepreg in which a cover film that contacts 40 to 70% of the surface area of the prepreg is attached to at least one surface of a prepreg obtained by impregnating a reinforcing fiber sheet made of reinforcing fibers with a thermosetting resin composition. A cover film-attached prepreg having a complex viscosity η ^{* at} a temperature of 40 ° C. of the thermosetting resin composition in the range of 1.0 × 10 ^{2 to} 1.0 × 10 ⁴ Pa · s.   The cover film sticking prepreg according to claim 1, wherein the content of the thermosetting resin composition in the prepreg is 20 to 50% by mass.   The cover film sticking prepreg according to claim 1 or 2, wherein the reinforcing fibers include carbon fibers.   The cover film sticking prepreg according to any one of claims 1 to 3, wherein the reinforcing fiber sheet includes a woven material.