Manufacturing method of short fiber reinforced prepreg sheet

Abstract

To provide a manufacturing method of a short fiber-reinforced prepreg sheet small in basis weight variation in a sheet width direction and small in a loss width relative to a production width by controlling the basis weight of an edge of the short fiber-reinforced prepreg sheet.SOLUTION: A manufacturing method of a short fiber-reinforced prepreg sheet comprises: after a cutting step of cutting a reinforcing fiber bundle into a specified bundle length to form a chopped fiber bundle, a spraying step for spraying the obtained chopped fiber bundle on a moving body that continuously moves in a downstream direction of a manufacturing process to obtain a chopped fiber bundle deposit, the spraying step is performed in a spraying area in which both ends in the width direction of the moving body were regulated by vertical walls, after completion of the spraying step, and a step of spreading and leveling chopped fiber bundles contained in high basis weight regions formed at both ends in the width direction of the chopped fiber bundle deposit.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing a short fiber reinforced prepreg sheet with small variation in basis weight in the sheet width direction and small sheet end loss. [Background technology]

[0002] A short fiber reinforced prepreg sheet is known in which chopped fiber bundles, which are reinforcing fiber bundles cut to a specified length, are scattered and randomly distributed on a chopped fiber bundle pile and impregnated with a matrix resin. Examples of the short fiber reinforced prepreg sheet include sheet molding compound (hereinafter, SMC) and stampable sheets.

[0003] A short fiber reinforced prepreg sheet containing chopped fiber bundles as reinforcing fibers has excellent shapeability during shaping and flowability during heat and pressure molding because the reinforcing fibers do not restrict the deformation of the base material, as in a prepreg sheet using continuous fibers as a reinforcing material. In addition, the number of intertwining points in the chopped fiber bundle deposit is smaller than that of a nonwoven fabric or its precursor web, which is made of single yarns or fiber bundles that are finely divided to a degree close to single yarns, so it does not have shape retention and has excellent shapeability during shaping and flowability during heat and pressure molding, compared to a short fiber reinforced prepreg sheet using nonwoven fabric or its precursor web as a reinforcing material.

[0004] A short fiber reinforced prepreg sheet containing chopped fiber bundles generally has a larger variation in basis weight compared to a prepreg sheet containing continuous fiber. This is mainly due to the variation in basis weight of the chopped fiber bundle deposit, and it is desirable to suppress the variation in basis weight of the chopped fiber bundle deposit in order to suppress the variation in basis weight of the short fiber reinforced prepreg sheet and the weight variation of the molded product.

[0005] When producing a chopped fiber bundle deposit, the chopped fiber bundle is cut and then scattered on a moving body that moves continuously in the downstream direction of the manufacturing process to produce a chopped fiber bundle deposit. At this time, the basis weight of the chopped fiber bundle deposit is determined by the amount of reinforcing fiber bundles supplied to the cutting device and the speed of the moving body.

[0006] The widthwise length of the chopped fiber bundle pile can be controlled by dispersing the chopped fiber bundles in a dispersing region having upright walls for regulating the dispersing width at both ends of the moving body in the widthwise direction.

[0007] The variation in basis weight in the width direction of the chopped fiber bundle deposit is adjusted by controlling the amount of chopped fiber bundles to be fed in the width direction of the moving body. For example, when a chopped fiber bundle deposit is produced by arranging a plurality of reinforcing fiber bundles in a line in the width direction of the moving body, cutting them, and scattering them, the variation in basis weight in the width direction of the moving body can be controlled by adjusting the position where the reinforcing fiber bundles are cut and scattered in the width direction of the moving body. When a plurality of reinforcing fiber bundles are not fed, for example, there is a method of cutting the reinforcing fiber bundles and traversing the position where the chopped carbon fiber bundles are fed in the width direction of the moving body, which suppresses the variation in basis weight in the width direction of the chopped fiber bundle deposit. In addition, it is also possible to introduce a dispersion mechanism to uniformly distribute the chopped fiber bundles, and further improve the variation in basis weight in the width direction of the chopped fiber bundle deposit.

[0008] Furthermore, in order to increase the randomness of the chopped fiber bundle dispersion and to disperse the chopped fiber bundles uniformly, the chopped fiber bundle pile may be produced multiple times on the moving body. For example, multiple chopped fiber bundle pile production devices may be installed in the direction of travel of the moving body, or the chopped fiber bundle pile may be layered using a cross-wrapping device.

[0009] When using the chopped fiber bundle deposit to produce a short fiber reinforced prepreg sheet, for example, the moving body is a release film, and the upper surface of the unwound release film is coated with a matrix resin and chopped fiber bundles are deposited on this to produce a chopped fiber bundle deposit. Then, a film similarly coated with matrix resin is placed from above with the matrix resin coated surface facing the chopped fiber bundle deposit, and pressure is applied from above and below to impregnate the chopped fiber bundle deposit with the matrix resin, thereby producing a short fiber reinforced prepreg sheet.

[0010] In Patent Document 1, the cut chopped fiber bundles are conveyed and then dispersed, improving the unevenness of the weight per unit area during dispersion. Patent Document 2 clearly shows a chopped fiber bundle deposit having a coefficient of variation of weight per unit area and bulkiness of less than 20%. Patent Document 3 shows that the weight per unit area of ​​the prepreg after impregnation is made more uniform by applying pressure to the prepreg after preparation while restricting the pressure in the width direction. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2014-210991 A [Patent Document 2] JP 2019-39124 A [Patent Document 3] Patent No. 5822033 Summary of the Invention [Problem to be solved by the invention]

[0012] In order to suppress the variation in basis weight of the short fiber reinforced prepreg sheet, in Patent Document 1, control is possible up until just before the spraying process, but unevenness in basis weight still occurs during spraying. In Patent Document 2, the variation in basis weight in the width direction cannot be controlled. In Patent Document 3, the basis weight, Wf, of the non-product part at the very end cannot be controlled, and the base material is actively made to flow after impregnation, which leads to twisting of the reinforcing fibers. As described above, in all of Patent Documents 1 to 3, there is room for improvement in the variation in basis weight in the width direction of the short fiber reinforced prepreg sheet, and no control is performed on the non-product part at the end in the width direction of the short fiber reinforced prepreg sheet.

[0013] As described above, the width direction length of the chopped fiber bundle pile can be controlled by spreading the chopped fiber bundles in a spreading area having a vertical wall that regulates the spreading width in the width direction of the moving body. However, if an attempt is made to maintain the basis weight of the ends of the chopped fiber bundle pile equal to that of the center, the chopped fiber bundles that come into contact with the vertical wall surface that regulates the spreading width during spreading will be piled up directly below the vertical wall, resulting in a region with a locally high basis weight.

[0014] This problem occurs when the scattering width of the chopped fiber bundle pile is restricted by providing a vertical wall surface in the width direction of the moving body, and also occurs when the scattered chopped fiber bundle is dispersed by a dispersion mechanism within the scattering area. Furthermore, when no vertical wall is provided to restrict the scattering width of the chopped fiber bundle pile in the width direction of the moving body, the chopped fiber bundle is scattered widely, and the non-product portion becomes extremely large. Thus, it has been difficult to control the non-product portion at the width direction end of the chopped fiber bundle pile in the conventional method.

[0015] In response to the above problems, the present invention provides a method for manufacturing a short-fiber-reinforced prepreg sheet by controlling the basis weight at the ends of the short-fiber-reinforced prepreg sheet, thereby minimizing variation in basis weight in the sheet width direction and minimizing loss width relative to the product width. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention employs the following means. [1 ]A method for producing a short fiber reinforced prepreg sheet, comprising a cutting step in which reinforcing fiber bundles are cut to a specified bundle length to form chopped fiber bundles, and then a spreading step in which the obtained chopped fiber bundles are spread onto a moving body that moves continuously in a downstream direction of the production process to obtain a chopped fiber bundle deposit, wherein the spreading step is carried out within a spreading area defined by vertical walls at both widthwise ends of the moving body, and the spreading step has a section in which the distance between the vertical walls gradually increases downstream of the production process. [ 2]A method for producing a short fiber reinforced prepreg sheet, which includes a cutting step in which reinforcing fiber bundles are cut to a specified bundle length to form chopped fiber bundles, and a spreading step in which the obtained chopped fiber bundles are spread onto a moving body which moves continuously in a downstream direction of the manufacturing process to obtain a chopped fiber bundle deposit, wherein the spreading step is carried out within a spreading area defined by vertical walls at both widthwise ends of the moving body, and an obstacle is provided on the inside of the vertical wall to prevent the chopped fiber bundles from colliding with the vertical wall. Effect of the Invention

[0017] By the method for producing a short fiber reinforced prepreg sheet of the present invention, the basis weight of the ends of the short fiber reinforced prepreg sheet is controlled, and a short fiber reinforced prepreg sheet can be provided in which the basis weight variation in the width direction of the short fiber reinforced prepreg sheet is small and the loss width relative to the product width is small. [Brief description of the drawings]

[0018] [Figure 1] The bundle length of the chopped fiber bundle is shown. [Diagram 2] An example of a method for producing a short fiber reinforced prepreg sheet will be described. [Diagram 3] The width of the short fiber reinforced prepreg sheet is shown. [Figure 4] 1 shows the width of the chopped fiber bundle pile. [Diagram 5] 1A and 1B show an example of a means for spreading and leveling chopped fiber bundles contained in high basis weight regions at both ends of a chopped fiber bundle pile outward in the width direction ((a) top view, (b) side view). [Figure 6] An example of the case where there is a section in which the distance between the standing walls gradually increases toward the downstream of the manufacturing process will be described. [Figure 7] 13 shows an example of an obstacle provided inside the standing wall to prevent the chopped fiber bundles from colliding with the standing wall. [Figure 8] FIG. 2 is an explanatory diagram showing a measurement area for basis weight Wf. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention has the above-mentioned characteristics, and the embodiments for carrying out the invention will be described in detail below.

[0020] The present invention provides a method for producing a short fiber reinforced prepreg sheet, which includes a cutting step in which reinforcing fiber bundles are cut to a specified bundle length to form chopped fiber bundles, followed by a spreading step in which the obtained chopped fiber bundles are spread onto a moving body that moves continuously in a downstream direction of the manufacturing process to obtain a chopped fiber bundle deposit, the spreading step being carried out within a spreading area in which both widthwise ends of the moving body are restricted by vertical walls, and after completion of the spreading step, the chopped fiber bundles included in the high basis weight areas formed at both widthwise ends of the chopped fiber bundle deposit are spread outward in the width direction to be even.

[0021] Examples of the reinforcing fibers used in the present invention include organic fibers such as aramid fibers, polyethylene fibers, and polyparaphenylene benzoxazole (PBO) fibers; inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, Tyranno fibers, basalt fibers, and ceramic fibers; metal fibers such as stainless steel fibers and steel fibers; and boron fibers, natural fibers, and modified natural fibers. These reinforcing fibers are often handled in the form of reinforcing fiber bundles consisting of a large number of monofilaments arranged in one direction converged together.

[0022] The reinforcing fiber bundle may be a strand that has been subjected to partial fiber splitting. Here, the partial fiber splitting is a process in which the fiber splitting process is performed intermittently along the orientation direction of the monofilaments that constitute the strand. When the ends of the strands that have been subjected to partial fiber splitting are joined to form a joined strand, and the overlapping portion of the joined strand is also a chopped strand, the strand can be continuously supplied while maintaining the handleability when the partial fiber splitting process is performed.

[0023] The number of monofilaments contained in the reinforcing fiber bundle is not particularly limited, but is preferably 1,000 to 100,000, and more preferably 1,000 to 50,000. With such a number of monofilaments, productivity is good.

[0024] These reinforcing fibers can be impregnated with a matrix resin and used as reinforcing materials for fiber-reinforced composite materials. Among these, carbon fibers (especially PAN-based carbon fibers) are lightweight among these reinforcing fibers, and have particularly excellent properties in terms of specific strength and specific elastic modulus, as well as excellent heat resistance and chemical resistance, making them suitable for fiber-reinforced composite materials.

[0025] Furthermore, when the reinforcing fiber is carbon fiber, the specific gravity of the carbon fiber is light, so that the chopped fiber bundles are easily spread over a wider area. As a result, the chopped fiber bundles come into contact with a vertical wall that restricts the spreading width in the width direction of the moving body when spread, making it difficult to control the basis weight at the end of the chopped fiber bundle pile. On the other hand, higher strength and lower variation are often required, so it is preferable that the reinforcing fiber is carbon fiber.

[0026] The chopped fiber bundle is the reinforcing fiber bundle cut to a specified length. An example of the bundle length 101 of the chopped fiber bundle is shown in Fig. 1, and the bundle length of the chopped fiber bundle is defined as the length in the monofilament direction of the two most protruding points in the orientation direction 102 of the monofilaments constituting the chopped fiber bundle.

[0027] The average bundle length of the chopped fiber bundles is a value obtained by randomly extracting 100 chopped fiber bundles, measuring the bundle length of each chopped fiber bundle by the above-mentioned method, and then calculating the arithmetic mean value of the bundle lengths of the 100 chopped fiber bundles measured.

[0028] The number of monofilaments in the chopped fiber bundle is not particularly limited, but is preferably 1,000 to 50,000, more preferably 1,000 to 24,000, and even more preferably 1,000 to 4000. With such a number of monofilaments, high mechanical properties can be exhibited.

[0029] In addition, if the average bundle length of the chopped fiber bundle is short, it is difficult to obtain a reinforcing effect, but if the average bundle length of the chopped fiber bundle is long, the fluidity and shapeability are reduced. Therefore, the average bundle length of the chopped fiber bundle is preferably 5 mm or more and 100 mm or less, and more preferably 10 mm or more and 30 mm or less.

[0030] As the matrix resin, a thermosetting resin or a thermoplastic resin can be suitably used. For example, as the thermosetting resin, there can be mentioned thermosetting resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, epoxy acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, cyanate resin, etc. In particular, when an epoxy resin, an unsaturated polyester resin, or a vinyl ester resin is used, it is suitable because it exhibits excellent interfacial adhesion to the reinforcing fiber. As the thermosetting resin, one type may be used alone, or two or more types may be used in combination.

[0031] Examples of the thermoplastic resin include polyolefin resins such as polyethylene resin and polypropylene resin, polyamide resins such as nylon 6 resin and nylon 6,6 resin, polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, polyphenylene sulfide resin, polyether ketone resin, polyether sulfone resin, aromatic polyamide resin, etc. As the thermoplastic resin, one type may be used alone, or two or more types may be used in combination.

[0032] A prepreg sheet is a sheet-handleable form of reinforcing fibers impregnated with a matrix resin and then semi-cured or thickened. The reinforcing fibers used in the prepreg sheet include continuous fibers and short fibers. The present invention relates to a short fiber-reinforced prepreg sheet using short fibers.

[0033] The form of the short fiber reinforced base material used in the short fiber reinforced prepreg sheet can be nonwoven fabric, its precursor web, or chopped strand deposit. When producing a chopped fiber bundle deposit, chopped fiber bundles are cut and then spread on a moving body moving in the downstream direction of the manufacturing process to produce a chopped fiber bundle deposit. On the other hand, nonwoven fabrics are produced by dry method, wet method, spunbond method, meltblown method, airlaid method, etc., and methods for bonding webs to form nonwoven fabrics include dipping method, spray method, thermal bond method, needle punch method, and hydroentanglement method. The number of entanglement points of chopped fiber bundle deposits is smaller than that of nonwoven fabrics composed of single yarns or fiber bundles divided to a degree close to single yarns, and their precursor webs, so they do not have shape retention, and are superior in shape forming during shaping and flowability during heating and pressure molding compared to short fiber reinforced prepreg sheets using nonwoven fabrics or their precursor webs as reinforcement materials. The present invention relates to a method for producing a short fiber reinforced prepreg sheet using chopped fiber bundles.

[0034] The basis weight is the mass per unit area. The basis weight of a short fiber reinforced prepreg sheet or a pile of chopped fiber bundles can be measured by placing a cutout mold of a predetermined size on the short fiber reinforced prepreg sheet to cut out a sample, or by measuring the weight of a sample cut to a predetermined size with a roller cutter, and dividing the sample weight by the sample area.

[0035] When the average weight per unit area of ​​the short fiber reinforced prepreg sheet in the entire width direction is high, molded products can be produced efficiently, but if it is too high, problems such as poor impregnation can occur. Therefore, it is recommended that the average weight per unit area of ​​the short fiber reinforced prepreg sheet in the entire width direction be 1000 g / m 2 ~4000g / m2 It is preferable that:

[0036] The representative value of the weight of a short fiber reinforced prepreg sheet is the average weight of the entire width of the short fiber reinforced prepreg sheet in the width direction. This weight is calculated by cutting the short fiber reinforced prepreg sheet perpendicular to the longitudinal direction so that the length is 300 mm or more in the longitudinal direction of the short fiber reinforced prepreg sheet, cutting the sheet in a straight line that defines the width of the short fiber reinforced prepreg sheet, measuring the weight of the obtained sample, and dividing the measured weight by the area calculated from the width direction length of the sample (prepreg sheet width) and the longitudinal direction length of the sample short fiber reinforced prepreg sheet.

[0037] In addition, Wf is the mass ratio of the reinforcing fibers contained in the short fiber reinforced prepreg sheet, and if Wf is small, the reinforcing effect of the reinforcing fibers is small, and if Wf is large, impregnation failure occurs, and there is a risk of forming defects when the molded product is made. Therefore, the Wf of the short fiber reinforced prepreg sheet is preferably 40% or more and 65% or less, more preferably 45% or more and 65% or less, and even more preferably 50% or more and 65% or less.

[0038] The method for measuring Wf is to take a sample from the short fiber reinforced prepreg sheet, and then measure it according to, for example, the combustion method, nitric acid and sulfuric acid decomposition method described in JISK7075 Carbon fiber reinforced plastic fiber content and void content test method, or JISK7052 Long glass fiber reinforced plastic - Prepreg, molding material and molded product - Long glass fiber and inorganic filler content determination method - Firing method. If the sample size is large, divide it into smaller pieces and measure the Wf of the divided samples.

[0039] The Wf of a short fiber reinforced prepreg sheet can be taken as the average Wf of the entire width in the width direction of the short fiber reinforced prepreg sheet, and this Wf is a value obtained by cutting the short fiber reinforced prepreg sheet perpendicular to the longitudinal direction so that the length is 300 mm or more in the longitudinal direction of the short fiber reinforced prepreg sheet, and then cutting the short fiber reinforced prepreg sheet in a straight line defining the width of the short fiber reinforced prepreg sheet, and measuring the obtained sample using the above-mentioned Wf measuring method.

[0040] An example of a method for producing a short fiber reinforced prepreg sheet containing chopped fiber bundles is shown below. The short fiber reinforced prepreg sheet containing chopped fiber bundles of the present invention is produced, for example, by using an apparatus shown in Fig. 2, which performs the following resin sheet preparation step, cutting / spraying step, and impregnation step.

[0041] <Resin sheet preparation process> In the resin sheet preparation process, a first release film 202 is pulled out from a first sheet roll 201 and supplied to a first conveyor 221, and a predetermined amount of matrix resin paste is applied to the upper surface of the first release film 202 from a first resin bath 203 by a doctor blade to a predetermined thickness to form a first resin sheet 204.

[0042] Further, a long second release film 212 is pulled out from the second sheet roll 211 and supplied to a second conveyor 222. A predetermined amount of matrix resin paste is applied to the upper surface of the second release film 212 in a predetermined thickness by a doctor blade in a second resin bath 213, thereby forming a second resin sheet 214.

[0043] <Cutting and spraying process> In the cutting and scattering process, a reinforcing fiber bundle 232 is drawn from a bobbin 231 on which the continuous reinforcing fiber bundle is wound, and after passing through a nip roll 233, the reinforcing fiber bundle 232 is continuously cut to a predetermined length in a cutter 234 and scattered on the first resin sheet 204. When cutting, the continuous reinforcing fiber bundle may be cut at a predetermined angle in the range of 0°<θ≦90°. Here, the cut angle is the smaller angle between the fiber orientation direction and the cutting line, and is in the range of 0°<θ≦90°. Examples of a method for cutting the continuous reinforcing fiber bundle at a predetermined angle include a case where an angle is given when the yarn is conveyed to the cutter 105, and a case where an angle is given to the cutter 234 with respect to the yarn. There are no particular limitations on the cutter 234 as long as it does not impede the object of the present invention, and examples thereof include a guillotine blade type and a rotary cutter type. As described above, the direction of the blade for cutting is not particularly limited with respect to the direction in which the reinforcing fiber strand is transported, and may be angled in the same manner as the mechanism for transporting the reinforcing fiber strand. As a method for obtaining discontinuous reinforcing fiber bundles with different bundle lengths, a method in which a plurality of cutters 234 are prepared and discontinuous reinforcing fiber bundles with different bundle lengths are obtained, for example.

[0044] Furthermore, when the cut chopped fiber bundles 241 are dispersed, the dispersion can be performed within a dispersion region in which both widthwise ends of the moving body are restricted by standing walls 242. A distributor 243 may be disposed within the dispersion region to disperse the chopped fiber bundles.

[0045] In this manner, a chopped fiber bundle deposit 244 is continuously formed on the traveling first resin sheet 204.

[0046] <Impregnation process> In the impregnation step, the second resin sheet 214 is run, and the matrix resin-coated surface of the second resin sheet 214 is laminated on the chopped fiber bundle deposit 244. This continuously forms a short fiber reinforced prepreg sheet precursor 251 in which the chopped fiber bundle deposit is sandwiched between the matrix resin-coated surface of the first resin sheet 204 and the matrix resin-coated surface of the second resin sheet 214. The short fiber reinforced prepreg sheet precursor 251 is pressurized from both sides by the pressurizing mechanism 252, and the chopped fiber bundle deposit is impregnated with the matrix resins of the first resin sheet and the second resin sheet, thereby forming a short fiber reinforced prepreg sheet 253.

[0047] The above is an example of the process, and here, the short fiber reinforced prepreg sheet width is the distance between two straight lines at both ends of the short fiber reinforced prepreg sheet parallel to the longitudinal direction thereof, where the ratio of the areas where the chopped fiber bundles are present and the areas where they are not present is 50% when the short fiber reinforced prepreg sheet is viewed from above, as shown in Fig. 3, and the short fiber reinforced prepreg sheet end refers to the straight line. When the short fiber reinforced prepreg sheet can be stably produced, the short fiber reinforced prepreg sheet width is stable when calculated from a section of at least 300 mm in the longitudinal direction of the short fiber reinforced prepreg sheet, so the short fiber reinforced prepreg sheet width is the short fiber reinforced prepreg sheet width calculated from a section of at least 300 mm in the longitudinal direction of the prepreg sheet.

[0048] The width of the chopped fiber bundle deposit is the distance between two straight lines at both ends of the chopped fiber bundle deposit parallel to the longitudinal direction of the chopped fiber bundle deposit where the ratio of areas where chopped fiber bundles are present to areas where they are not present is 50% when the chopped fiber bundle deposit is viewed from above, as shown in Fig. 4. When chopped fiber bundle deposits can be stably produced, the sheet width is stable when calculated from a section of at least 300 mm in the longitudinal direction of the prepreg sheet, and therefore the sheet width is calculated from a section of at least 300 mm in the longitudinal direction of the prepreg sheet.

[0049] The chopped fiber bundles are preferably dispersed in a dispersion area having a vertical wall that regulates the dispersion width in the width direction of the moving body. Dispersion in such a dispersion area allows the width of the chopped fiber bundle deposit to be controlled. It is also preferable that the width of the chopped fiber bundle deposit is set narrower than the desired width of the short fiber reinforced prepreg sheet and wider than the application width of the matrix resin. By setting the chopped fiber bundle deposit width in this way, the desired short fiber reinforced prepreg sheet width can be achieved when pressure is applied from above and below in the impregnation step, and leakage of the matrix resin from the ends can be suppressed.

[0050] On the other hand, when chopped fiber bundles are sprayed in a spraying area having a vertical wall that regulates the spray width in the width direction of the moving body, if the weight of the end of the chopped fiber bundle pile is to be kept the same as that of the center, the chopped fiber bundles that come into contact with the vertical wall surface that regulates the spray width during spraying are deposited directly below the vertical wall, resulting in a region with a locally high weight. In response to this problem, the present invention provides a method for producing a short fiber reinforced prepreg sheet, which includes a step of spreading and leveling the chopped fiber bundles contained in the high weight regions formed at both ends of the chopped fiber bundle pile in the width direction outward in the width direction. The above method can eliminate the locally high weight region caused by the chopped fiber bundles deposited directly below the vertical wall of the chopped fiber bundle pile, and produce a chopped fiber bundle with a uniform weight up to the end, and the weight of the end of the short fiber reinforced prepreg sheet can be controlled, and a short fiber reinforced prepreg sheet with a small weight variation in the width direction of the short fiber reinforced prepreg sheet and a small loss width relative to the product width can be provided.

[0051] The present invention also provides a method for producing a short fiber reinforced prepreg sheet, in which the chopped fiber bundles in the high basis weight regions at both ends are spread outward in the width direction and leveled by a baffle plate or roll installed downstream of the spraying region so as to spread outward in the downstream direction.

[0052] As illustrated in Figure 5 ((a) top view, (b) side view), a baffle plate or roll is provided on the downstream side of the chopped fiber bundle spraying area so as to spread outward in the downstream direction, eliminating areas with locally high basis weight that occur when the chopped fiber bundles come into contact with the vertical wall surface that regulates the spray width during spraying at both ends of the chopped fiber bundle pile and accumulate just below the vertical wall, thereby controlling the basis weight at the ends of the short fiber reinforced prepreg sheet, and a short fiber reinforced prepreg sheet can be provided with little variation in basis weight in the width direction of the short fiber reinforced prepreg sheet and little loss width relative to the product width.

[0053] The material of the baffle plate or roll is not particularly limited, but it is preferable that the surface is smooth and non-static. If such a material is used, the chopped fiber bundles can be prevented from adhering to the surface of the baffle plate or roll when it comes into contact with the chopped fiber bundle deposit.

[0054] When viewed from the vertical upper surface of the moving body, the angle between the baffle plate or roll and the moving body in the width direction can be 0° to 90°, but is preferably 10° or more and less than 80°. By attaching it at such an angle, the chopped fiber bundle in the area with locally high basis weight can be continuously moved to the outside of the chopped fiber bundle.

[0055] The dimensions of the baffle plate or roll are not particularly limited, but it is preferable that the baffle plate or roll has a height capable of regulating the chopped fiber bundle pile height from the area with a locally high basis weight directly below the vertical wall to the area where the chopped fiber bundle is moved when the baffle plate or roll is attached. If the baffle plate or roll has such a width, the chopped fiber bundle in the area with a locally high basis weight can be continuously moved to the outside of the chopped fiber bundle.

[0056] The height at which the baffle plate or roll is attached is preferably such that the lower end of the baffle plate or roll is equal to or higher than the height of the target area, and is preferably lower than the height of the area with locally high basis weight due to the chopped fiber bundle accumulated just below the vertical wall. If the height is such, the chopped fiber bundle in the area with locally high basis weight can be continuously moved to the outside of the chopped fiber bundle.

[0057] In addition, a plurality of the baffles or rolls may be provided so that the height of the lowest end gradually decreases in the downstream direction. By providing a plurality of baffles or rolls in this manner, the chopped fiber bundle can be gradually moved toward the end portion.

[0058] The height of the baffle plate or the diameter of the roll may be sufficiently higher than the difference between the height of the area with a locally high basis weight due to the chopped fiber bundles accumulated immediately below the vertical wall and the height of the target basis weight area, and is preferably at least twice the height difference.

[0059] The present invention also provides a method for producing a short fiber reinforced prepreg sheet, which includes a cutting step in which reinforcing fiber bundles are cut to a specified bundle length to form chopped fiber bundles, and then a spreading step in which the obtained chopped fiber bundles are spread onto a moving body that moves continuously in a downstream direction of the production process to obtain a chopped fiber bundle deposit, wherein the spreading step is performed within a spreading area in which both widthwise ends of the moving body are restricted by standing walls, and the method has a section in which the distance between the standing walls gradually increases downstream of the production process.

[0060] As illustrated in FIG. 6, the spraying process is carried out within a spraying area in which both widthwise ends of the moving body are restricted by vertical walls, and the distance between the vertical walls has a section in which it gradually increases downstream in the manufacturing process. This makes it possible to prevent the occurrence of areas with locally high basis weight at the ends of the chopped fiber bundles by contacting the vertical wall surfaces that restrict the spray width during spraying of both ends of the chopped fiber bundle pile and depositing them in the width direction of the fiber bundle pile, thereby controlling the basis weight at the ends of the short fiber reinforced prepreg sheet, and making it possible to provide a short fiber reinforced prepreg sheet with small basis weight variation in the width direction of the short fiber reinforced prepreg sheet and small loss width relative to the product width.

[0061] Although there is no particular restriction on the length of the gradually increasing section in the moving body direction, it is preferable that there is no gradually increasing section at the moving body downstream end of the scattering region, and that there is a section in which the vertical wall is parallel to the moving body downstream direction for 3% or more of the moving body direction length of the scattering region at the moving body downstream end of the scattering region. By adopting such a configuration, the basis weight of the chopped fiber bundle pile end is stabilized.

[0062] There is no particular restriction on the gradual increase in the distance between the standing walls, but if it is 10% to 500% of the average bundle length of the chopped fiber bundles, the basis weight of the ends of the chopped fiber bundle pile will be stable.

[0063] The present invention also provides a method for producing a short fiber reinforced prepreg sheet, which includes a cutting step in which reinforcing fiber bundles are cut to a specified bundle length to form chopped fiber bundles, followed by a spreading step in which the obtained chopped fiber bundles are spread onto a moving body that moves continuously in the downstream direction of the manufacturing process to obtain a chopped fiber bundle deposit, the spreading step being carried out within a spreading area defined by vertical walls at both widthwise ends of the moving body, and an obstacle is provided on the inside of the vertical wall to prevent the chopped fiber bundles from colliding with the vertical wall.

[0064] As illustrated in FIG. 7, an obstacle is provided on the inside of the vertical wall to prevent the chopped fiber bundles from colliding with the vertical wall, and at least some of the chopped fiber bundles that were scheduled to contact the vertical wall do not contact the vertical wall due to the obstacle, and do not fall directly below the vertical wall. This makes it possible to suppress the occurrence of areas with locally high basis weight at the ends of the chopped fiber bundle pile, controls the basis weight at the ends of the short fiber reinforced prepreg sheet, and provides a short fiber reinforced prepreg sheet with small basis weight variation in the width direction of the short fiber reinforced prepreg sheet and small loss width relative to the product width.

[0065] There are no particular limitations on the obstacle as long as it prevents at least some of the chopped fiber bundles that were scheduled to contact the standing wall from contacting the standing wall, but it is preferable for the obstacle to have a smooth surface that is not charged, and it is preferable for the obstacle to have a slope so that the chopped fiber bundles do not accumulate.

[0066] The shape of the obstacle is not particularly limited, but examples include a cylindrical or flat plate shape that protrudes diagonally downward from the vertical wall, a cylindrical shape that extends horizontally downstream of the moving body and is provided near the vertical wall within the spraying area, or a flat plate angled so that the accumulated chopped fiber bundles are sprayed widthwise inward of the moving body.

[0067] In addition, the protruding amount of the obstacle from the vertical wall surface in the width direction of the moving body is preferably 500% or less of the average bundle length, and within the above range, the basis weight of the chopped fiber bundle pile end is stable. In addition, when multiple obstacles are installed, the protruding amount of each obstacle can be changed within the above range, so that the position where the chopped fiber bundle is scattered at the width direction end can be finely controlled. EXAMPLES

[0068] The present invention will now be described more specifically with reference to examples.

[0069] Example 1 A polypropylene release film was unwound from a roll, and a matrix resin was applied uniformly to the upper surface of the film using a doctor blade, adjusting the amount and width of the resin applied to produce two resin sheets. 2 The coating width was 1490 mm.

[0070] Matrix Resin: A resin prepared by mixing 100 parts by weight of vinyl ester resin (VE) resin (Dow Chemical Company, "Delaken 790" (registered trademark)), 1 part by weight of tert-butyl peroxybenzoate (NOF Corporation, "Perbutyl Z" (registered trademark)), 2 parts by weight of zinc stearate (Sakai Chemical Industry Co., Ltd., SZ-2000), and 4 parts by weight of magnesium oxide (Kyowa Chemical Industry Co., Ltd., MgO#40) was used.

[0071] Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as a reinforcing fiber bundle. The reinforcing fiber bundle was cut perpendicular to the longitudinal direction of the reinforcing fiber bundle using a cutter so that the length of the chopped fiber bundle was 12.7 mm, to obtain a chopped fiber bundle.

[0072] The chopped fiber bundles were sprayed onto the matrix resin of the first release film, which was continuously drawn out while the matrix resin was applied to the upper surface of the moving body, in a spraying area having a vertical wall that restricted the spray width in the width direction of the moving body, thereby forming a chopped fiber bundle deposit on the moving body.

[0073] The spraying area was a space with a maximum wall-to-wall distance of 1,495 mm, a downstream direction of 1,000 mm, and a height of 1,000 mm.

[0074] At this time, the chopped fiber bundles were cut from the reinforcing fiber bundles that had been fed in at equal intervals in a row in the width direction of the moving body, and were then spread. Therefore, the position where the chopped fiber bundles started to be spread was also in a row in the width direction of the moving body and at equal intervals. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g / m 2 It was.

[0075] In the spraying area, the chopped fiber bundles were dispersed by a distributor and dropped onto the matrix resin of the first release film to continuously form a chopped fiber bundle deposit in which the fiber bundles were randomly oriented. The distributor had a shape in which 16 wires were installed at equal intervals on a circle of Φ200 mm centered on the rotation axis, and the wires extended across the width of the spraying area. The distributor was installed directly below the reinforcing fiber bundle cutter, with the rotation axis of the distributor horizontal and in the width direction of the moving body, and when the rotation direction of the distributor was viewed from the upstream side of the moving body and viewed from the right hand side, the chopped fiber bundles were rotated at a speed of 400 rpm in a clockwise direction relative to the rotation axis of the distributor to be dispersed within the spraying area.

[0076] In addition, the vertical wall that regulates the dispersion width in the width direction of the moving body in the dispersion region had, from the upstream to downstream direction, a parallel section of 200 mm, a gradually increasing section of 300 mm, and a parallel section of 500 mm, and the gradual increase in the gradually increasing section was 25 mm. The gradually increasing section of the vertical wall was set as described above, and the chopped fiber bundles that came into contact with the vertical wall surface and accumulated immediately below the vertical wall surface were set to be dispersed in the width direction of the moving body.

[0077] The width of the chopped fiber bundle pile obtained in the above manner was 1495 mm. The chopped fiber bundle pile obtained did not have a high basis weight region due to the chopped fiber bundles that were in contact with the vertical wall surface and piled up immediately below the vertical wall surface.

[0078] Next, the second release film was placed on top of the chopped fiber bundle pile with the matrix resin-coated surface facing vertically downward, and the chopped fiber bundle pile was sandwiched between the first release film and the second release film from above and below. The chopped fiber bundle pile was then impregnated with the matrix resin using a compaction roll, wound up on a paper tube, and allowed to thicken at 40°C for 24 hours to obtain an SMC. The width of the obtained SMC was 1500 mm.

[0079] As shown in FIG. 8, 15 100 mm squares were cut out in the width direction of the obtained SMC from the width direction end of the SMC, and the coefficient of variation CVa of basis weight over the entire width in the width direction of the short fiber reinforced prepreg sheet was calculated to be 4.8%.

[0080] The obtained SMC was cut in the width direction so as to have a length of 300 mm in the longitudinal direction, and the average basis weight and average Wf of the entire width direction of the SMC were calculated, which was 2000 g / m 2 and Wf was 57%.

[0081] As shown in FIG. 8, a boundary line was set 6.35 mm inward from the end of the width direction of the obtained SMC, and a rectangular region of Lb=24.79 mm in the width direction of the SMC and 200 mm in the longitudinal direction was provided on the inner side of the short fiber reinforced prepreg sheet with respect to the boundary line so that the long side of the rectangular region overlapped with the boundary line. The basis weight and Wf of the rectangular region were calculated, and the basis weight was 1920 g / m 2 , which was 96% of the average basis weight of the entire width of the SMC in the width direction, and Wf was 56%, which was 98% of the average Wf of the entire width of the SMC in the width direction.

[0082] Furthermore, as shown in FIG. 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% or more and 120% or less in all rectangular regions.

[0083] Furthermore, as shown in FIG. 8, when two adjacent rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC from the boundary line toward the center in the SMC width direction, the basis weight of the outermost end was lower than that of the region one step further inward.

[0084] Example 2 A polypropylene release film was unwound from a roll, and a matrix resin was applied uniformly to the upper surface of the film using a doctor blade, adjusting the amount and width of the resin applied to produce two resin sheets. 2 The coating width was 1490 mm.

[0085] Matrix Resin: A resin prepared by mixing 100 parts by weight of vinyl ester resin (VE) resin (Dow Chemical Company, "Delaken 790" (registered trademark)), 1 part by weight of tert-butyl peroxybenzoate (NOF Corporation, "Perbutyl Z" (registered trademark)), 2 parts by weight of zinc stearate (Sakai Chemical Industry Co., Ltd., SZ-2000), and 4 parts by weight of magnesium oxide (Kyowa Chemical Industry Co., Ltd., MgO#40) was used.

[0086] Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as a reinforcing fiber bundle. The reinforcing fiber bundle was cut perpendicular to the longitudinal direction of the reinforcing fiber bundle using a cutter so that the length of the chopped fiber bundle was 12.7 mm, to obtain a chopped fiber bundle.

[0087] The chopped fiber bundles were sprayed onto the matrix resin of the first release film, which was continuously drawn out while the matrix resin was applied to the upper surface of the moving body, in a spraying area having a vertical wall that restricted the spray width in the width direction of the moving body, thereby forming a chopped fiber bundle deposit on the moving body.

[0088] At this time, the chopped fiber bundles were cut and scattered from the reinforcing fiber bundles that had been fed in a line at equal intervals in the width direction of the moving body, so the position where the chopped fiber bundles started to be scattered was also at equal intervals in a line in the width direction of the moving body. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g / m 2 It was.

[0089] In the spraying area, the chopped fiber bundles were dispersed by a distributor and dropped onto the matrix resin of the first release film to continuously form a chopped fiber bundle deposit in which the fiber bundles were randomly oriented. The distributor had a shape in which 16 wires were installed at equal intervals on a circle of Φ200 mm centered on the rotation axis, and the wires extended across the width of the spraying area. The distributor was installed directly below the reinforcing fiber bundle cutter, with the rotation axis of the distributor horizontal and in the width direction of the moving body, and when the rotation direction of the distributor was viewed from the right hand side as seen from the upstream of the moving body, the chopped fiber bundles were rotated at a speed of 400 rpm in a clockwise direction relative to the rotation axis of the distributor to be dispersed within the spraying area.

[0090] The spraying area was a space with a wall-to-wall distance of 1,495 mm, a downstream direction of 1,000 mm, and a height of 1,000 mm.

[0091] In addition, the vertical walls that regulate the spreading width in the width direction of the moving body in the spreading region did not have a section in which the distance between the vertical walls gradually increased in parallel to the downstream direction of the moving body. The chopped fiber bundle deposit obtained had a high basis weight region at the end of the chopped fiber bundle deposit due to the chopped fiber bundles that contacted the vertical wall surface and were piled up just below the vertical wall surface. The height of the high basis weight region of the chopped fiber bundle deposit was 20 mm, and the height of the other region was 15 mm.

[0092] Next, the chopped fiber bundles contained in the high basis weight region of the obtained chopped fiber bundle pile were moved to the end side of the chopped fiber bundle pile by using a baffle plate. The baffle plate was a stainless steel flat plate with a thickness of 2 mm, a width of 150 mm, and a height of 70 mm, and was attached so that the lower end in the height direction was 16 mm high. In addition, the angle formed by the baffle plate or roll and the moving body in the width direction at this time was 45°. In addition, the width direction center position of the baffle plate and the center of the upright wall were on a straight line in the downstream direction of the moving body. The chopped fiber bundles contained in the high basis weight region of the chopped fiber bundle pile were moved to the end side of the chopped fiber bundle pile by the baffle plate, and the high basis weight region became equivalent to the normal basis weight.

[0093] The width of the pile of chopped fiber bundles obtained in this manner was 1495 mm.

[0094] Next, the second release film was placed on top of the chopped fiber bundle pile with the matrix resin-coated surface facing vertically downward, and the chopped fiber bundle pile was sandwiched between the first release film and the second release film from above and below. The chopped fiber bundle pile was then impregnated with the matrix resin using a compaction roll, wound up on a paper tube, and allowed to thicken at 40°C for 24 hours to obtain an SMC. The width of the obtained SMC was 1500 mm.

[0095] As shown in FIG. 8, 15 100 mm squares were cut out in the width direction of the obtained SMC from the width direction end of the SMC, and the coefficient of variation CVa of basis weight over the entire width in the width direction of the short fiber reinforced prepreg sheet was calculated to be 5.2%.

[0096] The obtained SMC was cut in the width direction so as to have a length of 300 mm in the longitudinal direction, and the average basis weight and average Wf of the entire width direction of the SMC were calculated, which was 2000 g / m 2 and Wf was 57%.

[0097] As shown in FIG. 8, a boundary line was set 6.35 mm inward from the end of the width direction of the obtained SMC, and a rectangular region of Lb=24.79 mm in the width direction of the SMC and 200 mm in the longitudinal direction was provided on the inner side of the short fiber reinforced prepreg sheet with respect to the boundary line so that the long side of the rectangular region overlapped with the boundary line. The basis weight and Wf of the rectangular region were calculated, and the basis weight was 1912 g / m 2 , which was 96% of the average basis weight of the entire width of the SMC in the width direction, and Wf was 56%, which was 98% of the average Wf of the entire width of the SMC in the width direction.

[0098] Furthermore, as shown in FIG. 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% or more and 120% or less in all rectangular regions.

[0099] Furthermore, as shown in FIG. 8, when two adjacent rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC from the boundary line toward the center in the SMC width direction, the basis weight of the outermost end was lower than that of the region one step further inward.

[0100] Example 3 A polypropylene release film was unwound from a roll, and a matrix resin was applied uniformly to the upper surface of the film using a doctor blade, adjusting the amount and width of the resin applied to produce two resin sheets. 2 The coating width was 1490 mm.

[0101] Matrix Resin: A resin prepared by mixing 100 parts by weight of vinyl ester resin (VE) resin (Dow Chemical Company, "Delaken 790" (registered trademark)), 1 part by weight of tert-butyl peroxybenzoate (NOF Corporation, "Perbutyl Z" (registered trademark)), 2 parts by weight of zinc stearate (Sakai Chemical Industry Co., Ltd., SZ-2000), and 4 parts by weight of magnesium oxide (Kyowa Chemical Industry Co., Ltd., MgO#40) was used.

[0102] Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as a reinforcing fiber bundle. The reinforcing fiber bundle was cut perpendicular to the longitudinal direction of the reinforcing fiber bundle using a cutter so that the length of the chopped fiber bundle was 12.7 mm, to obtain a chopped fiber bundle.

[0103] The chopped fiber bundles were sprayed onto the matrix resin of the first release film, which was continuously drawn out while the matrix resin was applied to the upper surface of the moving body, in a spraying area having a wall that restricted the spraying width in the width direction of the moving body, thereby forming a chopped fiber bundle deposit on the moving body.

[0104] The spraying area was a space with a wall-to-wall distance of 1,495 mm, a downstream direction of 1,000 mm, and a height of 1,000 mm.

[0105] At this time, the chopped fiber bundles were cut and scattered from the reinforcing fiber bundles that had been fed in a line at equal intervals in the width direction of the moving body, so the position where the chopped fiber bundles started to be scattered was also at equal intervals in a line in the width direction of the moving body. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g / m 2 It was.

[0106] In the spraying area, the chopped fiber bundles were dispersed by a distributor and dropped onto the matrix resin of the first release film to continuously form a chopped fiber bundle deposit in which the fiber bundles were randomly oriented. The distributor had a shape in which 16 wires were installed at equal intervals on a circle of Φ200 mm centered on the rotation axis, and the wires extended across the width of the spraying area. The distributor was installed directly below the reinforcing fiber bundle cutter, with the rotation axis of the distributor horizontal and in the width direction of the moving body, and when the rotation direction of the distributor was viewed from the right hand side as seen from the upstream of the moving body, the chopped fiber bundles were rotated at a speed of 400 rpm in a clockwise direction relative to the rotation axis of the distributor to be dispersed within the spraying area.

[0107] In addition, the vertical walls that regulate the spreading width in the width direction of the moving body in the spreading region were parallel to the downstream direction of the moving body and did not have a section where the distance between the vertical walls gradually increased. The obtained chopped fiber bundle deposit had a high basis weight region at the end of the chopped fiber bundle deposit due to the chopped fiber bundles that contacted the vertical wall surface and were piled up just below the vertical wall surface. The height of the high basis weight region of the chopped fiber bundle deposit was 20 mm, and the height of the other region was 15 mm.

[0108] In addition, in the vertical wall that limits the spray width in the width direction of the moving body in the spraying area, 20 cylindrical shapes protruding diagonally downward from the side of the vertical wall are installed at equal intervals on each wall. The dimensions of the cylindrical shapes are Φ20 mm, the protruding length is 100 mm, and the angle between the cylindrical shapes and the vertical downward is 60°.

[0109] The width of the chopped fiber bundle pile obtained in the above manner was 1495 mm. The chopped fiber bundle pile obtained did not have a high basis weight region due to the chopped fiber bundles that were in contact with the vertical wall surface and piled up immediately below the vertical wall surface.

[0110] Next, the second release film was placed on top of the chopped fiber bundle pile with the matrix resin-coated surface facing vertically downward, and the chopped fiber bundle pile was sandwiched between the first release film and the second release film from above and below. The chopped fiber bundle pile was then impregnated with the matrix resin using a compaction roll, wound up on a paper tube, and allowed to thicken at 40°C for 24 hours to obtain an SMC. The width of the obtained SMC was 1500 mm.

[0111] As shown in FIG. 8, 15 100 mm squares were cut out in the width direction of the obtained SMC from the width direction end of the SMC, and the coefficient of variation CVa of basis weight over the entire width in the width direction of the short fiber reinforced prepreg sheet was calculated to be 6.1%.

[0112] The obtained SMC was cut in the width direction so as to have a length of 300 mm in the longitudinal direction, and the average basis weight and average Wf of the entire width direction of the SMC were calculated, which was 2000 g / m 2 and Wf was 57%.

[0113] As shown in FIG. 8, a boundary line was set 6.35 mm inward from the end in the width direction of the obtained SMC, and a rectangular region of Lb=24.79 mm in the width direction of the SMC and 200 mm in the longitudinal direction was provided on the inner side of the short fiber reinforced prepreg sheet with respect to the boundary line so that the long side of the rectangular region overlapped with the boundary line. The basis weight and Wf of the rectangular region were calculated, and the basis weight was 1940 g / m 2 , which was 97% of the average basis weight of the entire width of the SMC in the width direction, and Wf was 56%, which was 98% of the average Wf of the entire width of the SMC in the width direction.

[0114] Furthermore, as shown in FIG. 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% or more and 120% or less in all rectangular regions.

[0115] Furthermore, as shown in FIG. 8, when two adjacent rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC from the boundary line toward the center in the SMC width direction, the basis weight of the outermost end was lower than that of the region one step further inward.

[0116] Example 4 A polypropylene release film was unwound from a roll, and a matrix resin was applied uniformly to the upper surface of the film using a doctor blade, adjusting the amount and width of the resin applied to produce two resin sheets. 2 The coating width was 1490 mm.

[0117] Matrix Resin: A resin prepared by mixing 100 parts by weight of vinyl ester resin (VE) resin (Dow Chemical Company, "Delaken 790" (registered trademark)), 1 part by weight of tert-butyl peroxybenzoate (NOF Corporation, "Perbutyl Z" (registered trademark)), 2 parts by weight of zinc stearate (Sakai Chemical Industry Co., Ltd., SZ-2000), and 4 parts by weight of magnesium oxide (Kyowa Chemical Industry Co., Ltd., MgO#40) was used.

[0118] Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as a reinforcing fiber bundle. The reinforcing fiber bundle was cut perpendicular to the longitudinal direction of the reinforcing fiber bundle using a cutter so that the length of the chopped fiber bundle was 12.7 mm, to obtain a chopped fiber bundle.

[0119] The chopped fiber bundles were sprayed onto the matrix resin of a first release film, which was being continuously drawn out as a moving body while the matrix resin was being applied to its upper surface, in a spraying area having a vertical wall that restricted the spraying width in the width direction of the moving body, forming a chopped fiber bundle deposit on the moving body.

[0120] At this time, the chopped fiber bundles cut from the reinforcing fiber bundles fed at equal intervals in a row in the width direction of the moving body were scattered, so the scattering start positions of the chopped fiber bundles were also at equal intervals in a row in the width direction of the moving body. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g / m 2 It was.

[0121] In the spraying area, the chopped fiber bundles were dispersed by a distributor and dropped onto the matrix resin of the first release film to continuously form a chopped fiber bundle deposit in which the fiber bundles were randomly oriented. The distributor had a shape in which 16 wires were installed at equal intervals on a circle with a diameter of 200 mm centered on the rotation axis, and a shape in which the wires extended across the width of the spraying area was used. The distributor was installed directly below the reinforcing fiber bundle cutter, with the rotation axis of the distributor horizontal and in the width direction of the moving body, and when the rotation direction of the distributor was viewed from the right hand side as seen from the upstream of the moving body, the chopped fiber bundles were rotated at a speed of 400 rpm in a clockwise direction with respect to the rotation axis of the distributor to be dispersed within the spraying area.

[0122] The spraying area was a space with a wall-to-wall distance of 1,495 mm, a downstream direction of 1,000 mm, and a height of 1,000 mm.

[0123] In addition, the vertical walls that regulate the spray width in the width direction of the moving body in the spraying region did not have a section in which the distance between the vertical walls gradually increased parallel to the downstream direction of the moving body. In order to prevent the chopped fiber bundles from colliding with the vertical walls and accumulating directly below the vertical wall surface, four flat plates 100 mm wide and 100 mm long were installed on the vertical wall surface at an angle of 60° so as to protrude downward from the vertical wall.

[0124] The width of the chopped fiber bundle pile obtained in the above manner was 1495 mm. The chopped fiber bundle pile obtained did not have a high basis weight region due to the chopped fiber bundles that were in contact with the vertical wall surface and piled up immediately below the vertical wall surface.

[0125] Next, the second release film was placed on top of the chopped fiber bundle pile with the matrix resin-coated surface facing vertically downward, and the chopped fiber bundle pile was sandwiched between the first release film and the second release film from above and below. The chopped fiber bundle pile was then impregnated with the matrix resin using a compaction roll, wound up on a paper tube, and allowed to thicken at 40°C for 24 hours to obtain an SMC. The width of the obtained SMC was 1500 mm.

[0126] As shown in FIG. 8, 15 100 mm squares were cut out in the width direction of the obtained SMC from the width direction end of the SMC, and the coefficient of variation CVa of basis weight over the entire width in the width direction of the short fiber reinforced prepreg sheet was calculated to be 3.8%.

[0127] The obtained SMC was cut in the width direction so as to have a length of 300 mm in the longitudinal direction, and the average basis weight and average Wf of the entire width direction of the SMC were calculated, which was 2000 g / m 2 and Wf was 57%.

[0128] As shown in FIG. 8, a boundary line was set 6.35 mm inward from the end in the width direction of the obtained SMC, and a rectangular region of Lb=24.79 mm in the width direction of the SMC and 200 mm in the longitudinal direction was provided on the inner side of the short fiber reinforced prepreg sheet with respect to the boundary line so that the long side of the rectangular region overlapped the boundary line. The basis weight and Wf of the rectangular region were calculated, and the basis weight was 2010 g / m 2 , which was 101% of the average basis weight of the entire width of the SMC in the width direction, and Wf was 57%, which was 100% of the average Wf of the entire width of the SMC in the width direction.

[0129] Furthermore, as shown in FIG. 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the resulting SMC along the boundary line, the average basis weight in all rectangular regions was 98% or more and 103% or less.

[0130] Furthermore, as shown in FIG. 8, when two adjacent rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC from the boundary line toward the center in the SMC width direction, the basis weight of the outermost end was lower than that of the region one step further inward.

[0131] Comparative Example 1 An SMC was produced in the same manner as in Example 1, except that the chopped fiber bundles were sprayed in a spraying region in which the vertical wall that restricted the spray width in the width direction of the moving body was parallel to the downstream direction of the moving body. The obtained chopped fiber bundle deposit had a high basis weight region at the end of the chopped fiber bundle deposit due to the chopped fiber bundles that had contacted the vertical wall surface and been deposited directly below the vertical wall surface. The height of the high basis weight region of the chopped fiber bundle deposit was 20 mm, and the height of the other region was 15 mm.

[0132] As shown in FIG. 8, 15 100 mm squares were cut out in the width direction of the obtained SMC from the width direction end of the SMC, and the coefficient of variation CVa of basis weight over the entire width in the width direction of the short fiber reinforced prepreg sheet was calculated to be 7.8%.

[0133] The obtained SMC was cut in the width direction so as to have a length of 300 mm in the longitudinal direction, and the average basis weight and average Wf of the entire width direction of the SMC were calculated, which was 2000 g / m 2 and Wf was 57%.

[0134] As shown in FIG. 8, a boundary line was set 6.35 mm inward from the end in the width direction of the obtained SMC, and a rectangular region of Lb=24.79 mm in the width direction of the SMC and 200 mm in the longitudinal direction was provided on the inner side of the short fiber reinforced prepreg sheet with respect to the boundary line so that the long side of the rectangular region overlapped with the boundary line. The basis weight and Wf of the rectangular region were calculated, and the basis weight was 2120 g / m 2 , which was 106% of the average basis weight of the entire width of the SMC in the width direction, and Wf was 60%, which was 105% of the average Wf of the entire width of the SMC in the width direction.

[0135] Furthermore, as shown in FIG. 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% or more and 120% or less in all rectangular regions.

[0136] Furthermore, as shown in FIG. 8, when two adjacent rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC from the boundary line toward the center in the SMC width direction, the basis weight of the outermost end was higher than that of the region one step further inward.

[0137] Comparative Example 2 The chopped fiber bundles were sprayed in a spraying region where the vertical wall that regulates the spray width in the width direction of the moving body was parallel to the downstream direction of the moving body, and the interval at which the reinforcing fiber bundles were fed during cutting was narrowed to the center, except that an SMC was produced in the same manner as in Example 1. The chopped fiber bundle deposit obtained had a region at the end of the chopped fiber bundle deposit that was higher in basis weight than the vicinity thereof due to the chopped fiber bundles that had contacted the vertical wall surface and were deposited directly below the vertical wall surface. The height of the high basis weight region of the chopped fiber bundle deposit was 12 mm, and the height of the other region was 15 mm.

[0138] As shown in FIG. 8, 15 100 mm squares were cut out in the width direction of the obtained SMC from the width direction end of the SMC, and the coefficient of variation CVa of basis weight over the entire width in the width direction of the short fiber reinforced prepreg sheet was calculated to be 7.8%.

[0139] The obtained SMC was cut in the width direction so as to have a length of 300 mm in the longitudinal direction, and the average basis weight and average Wf of the entire width direction of the SMC were calculated, which was 2000 g / m 2 and Wf was 57%.

[0140] As shown in FIG. 8, a boundary line was set 6.35 mm inward from the end in the width direction of the obtained SMC, and the rectangular region of Lb=24.79 mm in the width direction of the SMC and 200 mm in the longitudinal direction was set on the inner side of the short fiber reinforced prepreg sheet with respect to the boundary line so that the long side of the rectangular region overlapped the boundary line. The basis weight and Wf of the rectangular region were calculated, and the basis weight was 1560 g / m 2 , which was 78% of the average basis weight of the entire width of the SMC in the width direction, and Wf was 45%, which was 79% of the average Wf of the entire width of the SMC in the width direction.

[0141] Furthermore, as shown in FIG. 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the boundary line from the obtained SMC, the average basis weight was 80% or more and 120% or less in all rectangular regions.

[0142] Furthermore, as shown in FIG. 8, when two adjacent rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC longitudinal direction were cut out from the obtained SMC from the boundary line toward the center in the SMC width direction, the basis weight of the outermost end was higher than that of the region one step further inward. [Industrial Applicability]

[0143] Molded articles using the short fiber reinforced prepreg sheet produced by the production method of the present invention can be suitably used in automobiles and other transportation equipment. [Explanation of symbols]

[0144] 101: Bundle length 102: Orientation direction 201: First sheet roll 202: First release film 203: 1st resin bath 204: First resin sheet 211: 2nd sheet roll 212: Second release film 213: 2nd resin bath 214: Second resin sheet 221: First conveyor 222: Second conveyor 231: Bobbin 232: Reinforced fiber bundle 233: Nip roll 234: Cutter 241: Chopped fiber bundle 242: Standing Wall 243: Distributor 244: Chopped fiber bundle pile 251: Short fiber reinforced prepreg sheet precursor 252: Pressure mechanism 253: Short fiber reinforced prepreg sheet 301: Short fiber reinforced prepreg sheet end 302: Short fiber reinforced prepreg sheet width 401: Chopped fiber bundle pile end 402: Chopped fiber bundle pile width 501: Baffle plate or roll 502: Angle 503: Moving direction of moving object 601: Standing wall 602: Gradual increase section 603: Moving direction of moving object 701: Obstacle 702: Chopped fiber bundle 703: Standing wall 801: Border 802: Moving direction of moving object

Claims

1. A method for manufacturing a short fiber reinforced prepreg sheet, comprising a cutting process in which reinforcing fiber bundles are cut to a specified bundle length to form chopped fiber bundles, followed by a spreading process in which the obtained chopped fiber bundles are spread onto a moving body that moves continuously in a downstream direction of the manufacturing process to obtain a chopped fiber bundle deposit, wherein the spreading process is carried out within a spreading area defined by vertical walls at both widthwise ends of the moving body, and wherein the distance between the vertical walls has a section in which it gradually increases downstream in the manufacturing process.

2. A method for producing a short fiber reinforced prepreg sheet, comprising a cutting step of cutting reinforcing fiber bundles to a specified bundle length to form chopped fiber bundles, followed by a spreading step of spreading the obtained chopped fiber bundles onto a moving body that moves continuously in a downstream direction of the manufacturing process to obtain a chopped fiber bundle deposit, wherein the spreading step is carried out within a spreading area defined by vertical walls at both widthwise ends of the moving body, and an obstacle is provided on the inside of the vertical wall to prevent the chopped fiber bundles from colliding with the vertical wall.

Images