Patent Application
20160303777
The present invention relates to a method for producing prepreg to be used as fiber-reinforced composite material. The present application is based upon and claims the benefit of priority to Japanese Patent Application No. 2013-219394, filed Oct. 22, 2013. The entire contents of the application are incorporated herein by reference.
Since fiber-reinforced composite material is lightweight and has excellent mechanical properties, it is widely used in structural applications such as aircraft, vehicles, ships and buildings as well as sporting goods applications such as golf shafts, fishing rods and tennis rackets.
To produce fiber-reinforced composite material, methods that use cloth prepreg and unidirectional prepreg are widely employed. Cloth prepreg is produced by impregnating a matrix resin composition into a cloth made by weaving reinforcing fiber bundles. Unidirectional prepreg is produced by aligning multiple fiber bundles in one direction to make a reinforcing fiber sheet and then impregnating a matrix resin composition into the reinforcing fiber sheet. Examples of matrix resin compositions are thermosetting and thermoplastic resins. Especially, thermosetting resins are often used.
At the time of producing prepreg, pressure impregnation methods are generally employed; such methods include hot melt extrusion, that is, where a matrix resin composition and a reinforcing fiber sheet are laminated, sandwiched and compressed by using pressure rolls, and heated.
A problem that may be observed first during prepreg production using a pressure impregnation method is that the matrix resin composition bulges out beyond the width of the reinforcing fiber sheet as a result of compressing the composition using pressure rolls. When the matrix resin composition has bulged out and an excessive amount adheres to both side edges of the prepreg, such a situation may lower the ease of handling of the prepreg while decreasing the strength of the resultant fiber-reinforced composite material.
A problem that may be observed second during the production of prepreg using a pressure impregnation method is that compression by using pressure rolls causes a reduction in the basis weight (weight per unit area) of reinforcing fiber on both side edges of a prepreg. Such a situation occurs when a reinforcing fiber sheet is compressed by pressure rolls and is spread out in a width direction, causing reinforcing fiber bundles to be moved sideways significantly at both edges of the reinforcing fiber sheet.
To solve the above first problem, Patent Publication 1 proposes a method for arranging a tape material having affinity with the matrix resin composition to be in touch with both side edges of a reinforcing fiber sheet. According to such a method, since the bulging matrix resin composition is removed along with the tape material that has affinity with the composition, the resultant prepreg will not include bulging portions of the composition.
However, the method described in Patent Publication 1 cannot prevent the matrix resin composition from bulging out. Thus, the bulging resin composition may still affect the stable production process of the prepreg.
In addition, using the production method described in Patent Publication 1, if the tape material arranged to be in touch with both side edges of the reinforcing fiber sheet is thinner than the prepreg, the prepreg flows out from between pressure rolls and the tape material, and the above second problem will occur. In addition, if the tape material is thicker than the prepreg, since the prepreg is not well compressed, the matrix resin composition will not be sufficiently impregnated into reinforcing fiber bundles. Furthermore, using a tape having affinity with the matrix resin composition as described in Patent Publication 1, an extra amount of the matrix resin composition needs to be used. Yet furthermore, once a matrix resin composition is adsorbed on the sheet, the sheet cannot be recycled, thus increasing the production cost.
Also, in the method of Patent Publication 2, protruding portions are arranged on the outer side of a release sheet so that the release sheet is bent to prevent the matrix resin composition from flowing out over the release sheet. Such a method is capable of preventing a matrix resin composition from flowing out over the release sheet. However, the method is incapable of suppressing a matrix resin composition from flowing out of the prepreg, and is not so effective in solving the above first problem, either.
Patent Publication 1: JP H6-170847A
Patent Publication 2: JP H6-200051A
The present invention was carried out to solve the aforementioned problems. Namely, an aspect of the present invention is a method for producing a prepreg as follows: when a reinforcing fiber sheet and a matrix resin composition are compressed to impregnate the resin into the fiber sheet, the matrix resin composition is prevented from bulging out and the reinforcing fiber sheet from spreading out in a width direction. Accordingly, the matrix resin composition is prevented from adhering excessively to both side edges of the prepreg, the ease of handling the prepreg will not diminish, and the strength of fiber-reinforced composite material will not decrease. In addition, since the reinforcing fiber sheet is prevented from spreading out to result in a greater width, the basis weight of the reinforcing fiber will not decrease on both side edges of prepreg.
A method for producing a prepreg according to an embodiment of the present invention includes the following: preparing a reinforcing fiber sheet containing multiple reinforcing fiber bundles, a matrix resin composition, first and second release sheets, and a pair of elastic members; forming a prepreg precursor by providing the matrix resin composition on the reinforcing fiber sheet; sandwiching the prepreg precursor between the first and second release sheets so that first surfaces of the first and second release sheets make contact with the prepreg precursor and that the first and second release sheets respectively include extended portions that protrude outward from both edges of the prepreg precursor in a width direction; positioning the paired elastic members to face the extended portions of the second release sheet and to make contact with the second surface of the second release sheet; and compressing the prepreg precursor, the first and second release sheets and the elastic members all at once in a thickness direction of the prepreg precursor.
The elastic members may be set to be continuous in a longitudinal direction of the prepreg precursor, or may be set to be annular.
The tension of the elastic members may be controlled.
The elastic members may be made of a foamed material.
Lubrication treatment may be conducted on the elastic members.
The second release sheet may be made of a thermoplastic resin film.
The reinforcing fiber sheet may be made of unidirectional reinforcing fiber bundles.
The reinforcing fiber sheet may be made of short reinforcing fiber bundles two-dimensionally deposited at random.
The reinforcing fiber sheet may be made up of a first reinforcing fiber sheet and a second reinforcing fiber sheet, and the method for producing a prepreg may further include a step for forming the prepreg precursor by coating a matrix resin composition on one surface of the first reinforcing fiber sheet, and by laminating the second reinforcing fiber sheet on the one surface of the first reinforcing fiber sheet.
According to the above embodiments of the present invention, a prepreg is obtained where the resin composition does not bulge out from both side edges of the prepreg, and the basis weight of the reinforcing fiber is not reduced on both side edges of the reinforcing fiber sheet.
Embodiments of the present invention are described below in detail with reference to the accompanying drawings.
In
In
Prepreg precursor (A) is sandwiched between first release sheet 2 and second release sheet 2′, which are pulled out through feed rolls 15 when second reinforcing fiber sheet 1′ is laminated on the matrix resin composition. First and second release sheets 2, 2′ each have a first surface that makes contact with prepreg precursor (A) and a second surface opposite the first surface. Namely, first and second release sheets 2, 2′ are laminated on prepreg precursor (A) so that first surface 2a of first release sheet 2 and first surface 2a′ of second release sheet 2′ are set to face prepreg precursor (A). Here, the size of first and second release sheets 2, 2′ in a width direction (direction perpendicular to the direction of travel) is set greater than the size of prepreg precursor (A) in a width direction, as shown in
Moreover, prepreg precursor (A) sandwiched between first and second release sheets 2, 2′ travels through a pair of nip guide rolls 8. Paired nip guide rolls 8 are positioned to have a predetermined space between them. Laminated first and second release sheets 2, 2′ and prepreg precursor (A) are compressed while they pass through the space.
Next, prepreg precursor (A) is heated by using hot plate 9 at a heating temperature of approximately 80˜120° C.
Then, prepreg precursor (A) sandwiched between first and second release sheets 2, 2′ is compressed in a thickness direction by a pair of pressure rolls 10. Multiple pairs of pressure rolls 10 are arranged in the direction of travel. When prepreg precursor (A) is compressed by multiple pairs of pressure rolls 10, the matrix resin composition in prepreg precursor (A) is gradually impregnated into reinforcing fiber sheets 1, 1′.
Next, prepreg precursor (A) is compressed when it passes between pressure rolls 10A, 10B positioned on the downstream side (rear side) in the direction of travel. Compression process by pressure rolls 10A, 10B is described with reference to
A pair of elastic members 5 set to be continuous in a longitudinal direction of prepreg precursor (A) is provided on pressure roll 10B, one of paired pressure rolls 10A, 10B. On portions of second release sheet 2′, which are on the outer sides of where prepreg precursor (A) is arranged (positions facing extended portions 2A, 2A′), elastic members 5 are respectively arranged parallel to each other. Pressure rolls 10A, 10B compress elastic members 5, prepreg precursor (A) and release sheets 2, 2′ all at once in a thickness direction of prepreg precursor (A).
As shown in
Elastic members 5 are provided in a loop to circulate from pressure roll 10B to elastic-member guide roll 17 as shown in
Prepreg 3, which is a compressed prepreg precursor (A), is cooled by cooling plate 11. Moreover, when going through haul-off rolls 12 and release guide rolls 13, first release sheet 2 laminated on the upper side is removed from prepreg 3, and prepreg 3 along with second release sheet 2′ is wound by winding device 14. First release sheet 2 is recovered by release-sheet winding device 18.
As shown in
Various inorganic or organic fibers may be used as reinforcing fiber in reinforcing fiber sheet 1. For example, carbon fibers, graphite fibers, aramid fibers, nylon fibers, high-strength polyester fibers, glass fibers, boron fibers, alumina fibers, silicon nitride fibers and the like may be used. Among them, carbon fibers and graphite fibers are preferred to be used as reinforcing fiber since they have properties such as flame retardancy, high specific strength and high specific elastic moduli. Depending on usage purposes, various carbon fibers or graphite fibers may be used. Especially preferred are carbon fibers with a tensile elongation of 1.5% or higher, more preferably carbon fibers with a tensile strength of 4.5 GPa or greater and a tensile elongation of 1.7% or higher, even more preferably carbon fibers with a tensile elongation of 1.9% or higher.
The basis weight of fiber in a reinforcing fiber sheet is adjusted according to the requirement of fiber-reinforced composite material. For example, when the total basis weight of reinforcing fiber sheet sandwiched by first and second release sheets 2, 2′ is 150 g/m2, more preferably 300 g/m2, the present invention is especially effective.
Since a matrix resin composition needs to be impregnated into reinforcing fiber sheet 1, it is preferred to use a liquid resin having a low viscosity that does not cause problems in handling. Examples of a matrix resin composition are thermosetting resins such as epoxy resins, vinyl ester resins, unsaturated polyester resins, phenolic resins, and maleimide resins.
When carbon fibers are used as reinforcing fiber, epoxy or vinyl ester resins are preferred since they exhibit excellent adhesiveness with carbon fibers.
Specific examples of epoxy resins are glycidyl ether epoxy resins, glycidyl amine epoxy resins, glycidyl ester epoxy resins, alicyclic epoxy resins and the like. If necessary, a curing agent, a curing aid, or other additives are mixed in to prepare a matrix resin composition.
The amount of matrix resin composition adhered to the fiber sheet is adjusted according to the requirements of a fiber-reinforced composite material; for example, the resin amount may be 20˜50 mass % of the weight of a prepreg.
Specific examples of first and second release sheets 2, 2′ are release papers or release films formed by coating a release agent such as a silicone resin on wood-based paper or film made of soft or hard crosslinked polymers.
Examples of wood-based papers are kraft paper, glassine paper or the like. Examples of soft crosslinked polymers that exhibit heat resistance higher than a processing temperature are polyethylene, polystyrene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polylactic acid, polyamide or the like. Examples of hard crosslinked polymers are polyethylene terephthalate and the like.
As for the material of second release sheet 2′ that makes contact with elastic members 5, if it is a wood-based paper or a film of a soft crosslinked polymer, the thickness is preferred to be 110 μm or less, preferably 80 μm or less, since such a thickness allows release sheet 2′ to deform along elastic members 5. If it is a film made of a hard crosslinked polymer, the thickness is preferred to be 75 μm or less, more preferably 25 μm or less. If it is a film made of a soft crosslinked polymer, its thickness is preferred to be 50 μm or greater, and if it is a film made of a hard crosslinked polymer, its thickness is preferred to be 15 μm or greater. Release papers and films satisfying the above thickness conditions are preferred, since they exhibit enough strength that does not cause breakage during the production process.
To form prepreg precursor (A) sandwiched between first and second release sheets 2, 2′, another method is to coat a matrix resin composition on first surfaces of first and second release sheets 2, 2′, and to sandwich reinforcing fiber sheet 1 between first and second release sheets 2, 2′ so that their respective first surfaces make contact with reinforcing fiber sheet 1. Yet another method for sandwiching reinforcing fiber sheet 1 by release sheets is to coat a matrix resin composition on a first surface of a release sheet, to laminate the coated release sheet on reinforcing fiber sheet 1 so that the first surface makes contact with one surface of reinforcing fiber sheet 1, and to laminate another release sheet, not coated with a matrix resin composition, on the other surface of reinforcing fiber sheet 1.
To compress prepreg precursor (A), any known method using pressure rolls 10 may be employed. At that time, using a device having a mechanism to adjust temperatures, prepreg precursor (A) is compressed under desired temperature conditions. As a result, conditions for impregnating a matrix resin composition into reinforcing fiber sheet 1 is more accurately controlled. Any known device may be used for such compression process. For example, they may be pressure rolls having an inner structure capable of holding a thermal medium such as hot water, pressure rolls having an induction heater on its surface, or the like. It is preferred to use pressure rolls capable of exerting strong compression for a prepreg precursor (A) that includes a sheet made of multiple unidirectional reinforcing fiber bundles. However, that is not the only option. Various compression methods suitable for the structure of a prepreg may be employed as long as elastic members are provided therein.
In addition, if pressure rolls with a small diameter are used, a reverse flow of a matrix resin may occur due to a sudden rise in pressure. Therefore, the diameter of pressure rolls for exerting high pressure is preferred to be at least 300 mm, more preferably 400 mm or greater, even more preferably 500 mm or greater.
The force of pressure rolls may be set differently depending on the width and weight of prepreg 3, the percentage of a matrix resin to be contained, the viscosity of a matrix resin composition, and the elastic modulus, thickness and width of elastic member 5. Therefore, the pressing force is determined through arithmetic calculations and experiments based on such parameters as listed above. In the present embodiment, it is preferred to set a predetermined clearance between paired pressure rolls facing each other, and to compress the pressure rolls by exerting a sufficient load onto a clearance setting mechanism (not shown). The clearance of pressure rolls is gradually reduced from upstream pressure rolls toward downstream pressure rolls by setting the lower limit at the value obtained by adding the thickness reflecting the fiber weight/fiber density of a prepreg, the thickness reflecting the resin weight/resin density of the prepreg, and the thicknesses of first and second release sheets.
In the present embodiment, elastic members 5 cause extended portions 2A, 2A′ of first and second release sheets 2, 2′ to abut each other as described above so that prepreg precursor (A) is encapsulated in its width direction. Accordingly, reinforcing fiber of prepreg precursor (A) is prevented from spreading in a width direction when flowing out with the matrix resin composition. As a result, the basis weight of reinforcing fiber is suppressed from decreasing toward both edges of the prepreg in a width direction.
When prepreg precursor (A) is nipped by pressure rolls 10A, 10B, due to the pressure caused by pressure rolls 10A, 10B, the matrix resin composition flows backward relative to the direction of travel of reinforcing fiber sheet 1 (toward the upstream side, in a reverse direction from the entry side of pressure rolls 10A, 10B). In such a case, to achieve the aforementioned effects of the present embodiment, both edges of prepreg precursor (A) in a width direction need to be encapsulated within a range of a resin reservoir formed by the flow of the matrix resin composition described above. Thus, elastic members 5 need to have a thickness that is 1˜10 times greater than the final thickness of a prepreg sheet prior to the compression process, and also to have a thickness equal to the thickness of the prepreg sheet when being compressed. Furthermore, elastic members 5 need to have resistance to deformation against the pressure coming from the matrix resin so that first and second release sheets 2, 2′ stay in contact with each other.
Therefore, as the material for elastic members 5, it is preferred to use material having an elongation at break of 100% or greater and a Young's modulus of 0.01˜40 MPa, more preferably, a material having an elongation at break of 200% or greater and a Young's modulus of 0.1˜5 MPa. Examples of the material for elastic members 5 are elastomers and foamed elastomers. Examples of elastomers are natural rubbers, synthetic rubbers such as butadiene rubbers, nitrile rubbers and acrylic rubbers, urethane rubbers, olefin-based elastomers such as EPM and EPDM, silicone rubbers and the like. Foamed elastomers are preferred, since their allowable compressibility is higher. Either closed-cell foams or open-cell foams are preferred to be used. Moreover, since heat resistance is excellent and permanent compression distortion at high temperature is minimal when silicone-foam rubbers are used, they are preferred because the elastic members can be used repeatedly.
The cross-sectional shape of an elastic member perpendicular to the direction of travel is not limited specifically as long as it is in a shape capable of preventing reinforcing fiber from spreading sideways when flowing out along with the resin composition. Circles, ellipses, squares, rectangles or the like may be employed.
In addition, when elastic members 5 are nipped and compressed between pressure roll 10B and second release sheet 2′, elastic members 5 elongate toward the upstream side. Thus, elastic members 5 are preferred to slide smoothly between second release sheet 2′ and pressure roll 10B. For that matter, it is preferred to employ any of the following treatments in advance: to conduct lubrication or low-friction treatment by coating silicone oil or fluorine resin on second surface 2b′ of second release sheet 2′ and on the surface of pressure roll 10B; to coat silicone oil or fluorine resin on elastic members 5; to provide a solid lubricant such as talc on elastic members 5; or to provide a generally used lubricating oil on elastic members 5, second release sheet 2′ and pressure roll 10B.
A predetermined space provided between elastic member 5 and an edge of prepreg precursor (A) may vary depending on the width of prepreg 3, the width and basis weight of reinforcing fiber sheet 1, the basis weight of a matrix resin composition, the thickness of compression space, compression force, the elastic modulus of elastic member 5, and the shape of elastic member 5. Thus, the size of a space between elastic member 5 and the edges of prepreg precursor (A) may be determined through arithmetic calculations and experiments based on such parameters listed above.
The method for providing elastic members 5 is not limited specifically. As shown in
In addition, as shown in
In the example shown in
In the example shown in
A method for producing a prepreg according to a second embodiment of the present invention is described with reference to
The present embodiment describes a method for producing a prepreg as a sheet molding compound (SMC) by using reinforcing fiber sheet 21, which is made of short reinforcing fiber bundles deposited two-dimensionally at random.
As shown in
In the present embodiment, the same as in the first embodiment, the measurement of first and second release sheets 22, 22′ in a width direction (direction perpendicular to the direction of travel) is set greater than that of prepreg precursor (B) in a width direction. As shown in
Next, prepreg precursor (B) is passed between second mesh belt conveyor 43 and third mesh belt conveyer 44 positioned to keep a predetermined space and be parallel to each other in a longitudinal direction. Moreover, compaction roll 38′ is appropriately lowered into the space between second and third mesh belt conveyors 43, 44 so that prepreg precursor (B) is compressed and the matrix resin composition is impregnated into reinforcing fiber sheet 21.
Compared with the compression exerted by pressure rolls 10, 10A, 10B in the first embodiment, compression exerted by mesh belt conveyors 43, 44 is sufficiently small. The viscosity of the matrix resin composition contained in SMC prepreg precursor (B) is significantly lower than the viscosity of the matrix resin composition contained in prepreg precursor (A) formed with unidirectional multiple reinforcing fiber bundles. Thus, if prepreg precursor (B) is compressed by employing a method for nipping the precursor between paired pressure rolls, the compression is too strong, and an excessive flow of resin is caused to the point that it may be difficult to maintain the sheet shape. To exert compression with sufficiently low force on prepreg precursor (B) containing reinforcing fiber bundles cut into a predetermined length, it is preferred to exert pressure using vertically positioned mesh belt conveyors along with alternately positioned compaction rolls 38′, 38 arranged vertically. In such a pressure device, compression is generated by the tension and curvature radius of mesh belts passing separately away from compaction rolls 38′, 38. However, that is not the only option in the present embodiment, and various compression methods may also be employed according to the structure of a prepreg as long as elastic members are provided therein.
In
As shown in
In
Prepreg precursor (B) after passing through second and third mesh belt conveyors 43, 44 is recovered by a recovery device (not shown). Then, prepreg precursor (B) is set aside at a predetermined temperature for a certain duration to increase the viscosity of the matrix resin composition. Accordingly, prepreg (SMC) is obtained.
Since a matrix resin composition needs to be impregnated into reinforcing fiber bundles of reinforcing fiber sheet 21, it is preferred to use a liquid resin with a low viscosity within a range that does not lower the ease of handling the matrix resin composition. Examples of a material for forming a matrix resin composition are thermosetting resins such as vinyl ester resins, unsaturated polyester resins, epoxy resins, phenolic resins and maleimide resins.
When carbon fibers are used for reinforcing fiber, it is preferred to use vinyl ester resins or epoxy resins since they exhibit excellent adhesiveness with carbon fibers.
A matrix resin composition is prepared by mixing a curing agent, a curing aid, or other additives to the above resin if necessary.
The amount of a matrix resin composition adhered to the fiber sheet is adjusted depending on the requirement of a fiber-reinforced composite material. For example, it is set at 30˜70 mass % of the prepreg mass.
As for the material for elastic members 25, it is preferred to use material having an elongation at break of 100% or greater and a Young's modulus of 0.01˜40 MPa, or it is especially preferred to use a material having an elongation at break of 200% or greater and a Young's modulus of 0.1˜5 MPa. Examples of the material for elastic members 25 are elastomers and foamed elastomers. Examples of elastomers are natural rubbers, synthetic rubbers such as butadiene rubbers, nitrile rubbers and acrylic rubbers, urethane rubbers, olefin-based elastomers such as EPM and EPDM, silicone rubbers and the like. Foamed elastomers and tubes may be used for elastic members 25. Foamed elastomers are preferred, since allowable compressibility is higher. Either closed-cell foams or open-cell foams are preferred to be used.
The cross-sectional shape of an elastic member perpendicular to the direction of travel is not limited specifically as long as it is in a shape capable of preventing reinforcing fiber from spreading sideways when flowing out with the resin composition. Circles, ellipses, squares, rectangles or the like may be employed. They may be solid or hollow. When an elastic member having a hollow cross section is used, the elastic member is preferred to have an apparent compression modulus of 0.01˜40 MPa, more preferably 0.1˜5 MPa, relative to the maximum width of a cross section when no load is exerted thereon. Regarding a minimum compressibility rate that causes permanent distortion, the elastic member is preferred to have a compressibility rate of 30% or greater relative to the maximum height of a cross section when no load is exerted thereon. The apparent compression modulus of an elastic member having a hollow cross section may be set in a preferred range by adjusting the pressure of fluid such as compressed air encapsulated in the hollow portion of the elastic member.
In addition, when elastic members 25 are nipped and compressed between second mesh belt conveyor 43 and second release sheet 22′, elastic members 25 elongate toward the upstream side. Thus, elastic members 25 are preferred to slide smoothly between second release sheet 22′ and second mesh belt conveyor 43. For that matter, the same treatments listed in the first embodiment may also be employed.
As for reinforcing sheet 21 and first and second release sheets 22, 22′, the same materials listed for reinforcing fiber sheet 1 and first and second release sheets 2, 2′ used in the first embodiment may also be used.
In
In
Also, in
An example of the first embodiment is described below.
Materials used in the present example are listed in the following.
First, 8.3 parts by mass of epoxy resin A, 1 part by mass of the curing agent, and 4.1 parts by mass of the curing aid were measured, stirred and mixed. The mixture was further finely mixed by using a three-roll mill to prepare a curing agent masterbatch. Separately, 75.7 parts by mass of epoxy resin A and 16 parts by mass of epoxy resin B were placed in a glass flask and heated to 130° C. by using an oil bath. Then, the mixture of epoxy resins A and B was cooled to approximately 60° C. To the cooled mixture 13.4 parts by mass of the curing agent masterbatch was added, stirred and mixed. Accordingly, a matrix resin composition was obtained. When the viscosity of the matrix resin composition is measured at 30° C. under the following conditions, it was 50 Pa·s.
Device: viscoelasticity measuring device (brand name “VAR-100” made by Reologica Instruments AB)
Plate: 40φ parallel plates
Gap betw. plates: 0.5 mm
Measuring frequency: 1.59 Hz
Heating rate: 2° C./min.
A silicone sponge rubber having a porosity of 50% and an Asker C hardness of 35 degrees was processed to have a natural thickness of 2 mm and natural width of 20 mm. Then, two elastic members 5 were obtained, each having a circumferential length of 1800 mm under no tension. Surface lubrication treatment was conducted on the elastic members by coating silicone oil (brand name “Silicone Lube Spray” made by Kure Engineering, Ltd.)
Using a production apparatus shown in
When visually observed, first and second release sheets 2, 2′ were adhered to each other by elastic members 5, and no resin was observed flowing out of the adhered portions of first and second release sheets 2, 2′. The obtained prepreg 3 was cooled by using cooling plate 11 and was passed between haul-off rolls 12 so that first release sheet 2 was removed by peeling-guide rolls 13, and prepreg 3, along with second release sheet 2′, was wound by winding device 14.
Accordingly, 179 mm-wide unidirectional prepreg was obtained. When the unidirectional prepreg was observed visually, no bulging of resin was observed on either edge of the prepreg, and the prepreg was easily peeled from second release sheet 2′ to exhibit ease of handling. In addition, the prepreg was cut into 20 mm-wide (29 mm wide at edges) and 200 mm-long strips. The matrix resin was removed from each strip by using a sufficient amount of acetone, and the dry weight of the reinforcing fiber was measured. The basis weights in fiber strips and the variation coefficient (hereinafter referred to as the variation coefficient of the basis weights in fiber strips) were calculated from the above measured values. The variation coefficient of the basis weights in fiber strips was 2.5%. The prepreg was found to have a uniform basis weight.
As Comparative Example 1, a prepreg was produced under the same conditions as in Example 1 except that elastic members 5 were not used, and 195 mm-wide unidirectional prepreg was obtained. Bulging resin was observed continuously on side edges of the unidirectional prepreg. Because of bulging matrix resin, it was necessary to pay special attention when the unidirectional prepreg was peeled from second release sheet 2′. In addition, when the variation coefficient of the basis weight in fiber strips was calculated the same as in Example 1 (at edges, the prepreg was cut into 26 mm-wide and 29 mm-wide strips), it was 4.7%.
The above results were listed in Table 1. Here, when the variation coefficient of the basis weights in fiber strips was less than 4%, it was evaluated as “good” and when the variation coefficient was 4% or greater, it was evaluated as “bad.” In addition, when no adhesion of resin was observed on both edges in a width direction, it was evaluated as “good” and when resin was adhered continuously, it was evaluated as “bad.”
From the results above, prepreg in Example 1 produced by the production method as described in the first embodiment was found to be a unidirectional prepreg where no resin bulges on the edges and the basis weight of fiber is uniform.
An example of the second embodiment is described below.
Materials used in the present example are listed in the following.
A resin composition was obtained by mixing the above listed resin, curing agent, inner release agent, thickener, and stabilizer at a ratio of 100.0:10.0:3.0:15.3:0.02. When the viscosity of the resin composition was measured the same as in Example 1, it was 0.3 Pa·s.
Chloroprene sponge rubber (Neoprene®) having a porosity of 80% and an Asker C hardness of 25 degrees was processed to produce two annular elastic members 25 with a natural thickness of 5 mm and a natural width of 15 mm.
Using a production apparatus shown in
By using a doctor blade method, the matrix resin composition was homogenously coated on a first surface of first release sheet 22 (polyethylene film: a 50 μm-thick poly sheet made by Tokuza K.K.) at a basis weight of 740 g/m2. Next, on the matrix resin coated surface (first surface) of first release sheet 22, reinforcing fiber cut into 25 mm pieces by using cutter 41 was uniformly dispersed and deposited. Moreover, by using a doctor blade method, the matrix resin composition was homogenously coated on a first surface of second release sheet 22′ (a 50 μm-thick poly sheet made by Tokuza) at a basis weight of 740 g/m2. Next, the first surface of second release sheet 22′ was laminated to be in contact with reinforcing fiber sheet 21 on first release sheet 22. Then, reinforcing fiber sheet 21 was compressed by first mesh belt conveyor 42, and prepreg precursor (B) was obtained.
Prepreg precursor (B) was passed through second and third mesh belt conveyors 43, 44 arranged parallel to each other in a longitudinal direction. Accordingly, prepreg precursor (B) was compressed and the matrix resin composition was impregnated into reinforcing fiber sheet 21. In addition, the targeted width of a final prepreg was set by aligning the inner edges of elastic members 25 at positions 5 mm outward respectively from both edges of the resin to be coated to have a width of 620 mm, and by providing the elastic members continuously on the second-surface 22b′ side of second release sheet 22′.
After that, prepreg precursor (B) was recovered by using a recovery device and was kept standing for a predetermined time to increase the viscosity of the matrix resin composition in prepreg precursor (B). Finally, prepreg (SMC) was obtained.
The width of the obtained SMC is shown in
As Comparative Example 2, an SMC was obtained under the same conditions as in Example 2 except that elastic members 25 were not used. The width of the obtained SMC is shown in
As shown in
Also, as shown in
By contrast, in Example 2 shown in
The variation coefficient of the basis weights was 10.3% in Comparative Example 2, whereas it was 5.1% in Example 2. It was found that products in Example 2 exhibited uniform quality.
The production method in Example 2 is capable of mass producing products at a higher yield than the method in Comparative Example 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-219394 | Oct 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/077945 | 10/21/2014 | WO | 00 |
