JP7622499B2 - Manufacturing method of short fiber reinforced prepreg sheet - Google Patents

Description

The present invention relates to a method for manufacturing short fiber reinforced prepreg sheets with small variation in basis weight in the sheet width direction and small sheet end loss.

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.

A short fiber reinforced prepreg sheet containing chopped fiber bundles as reinforcing fibers has excellent formability during shaping and flowability during heat and pressure molding because the reinforcing fibers do not restrict the deformation of the base material, as in prepreg sheets using continuous fibers as reinforcing materials. In addition, the number of intertwining points in the chopped fiber bundle deposit is smaller than that of nonwoven fabrics and their precursor webs, which are made of single yarns or fiber bundles that are broken down to a level close to single yarns, and therefore does not retain its shape. Compared to short fiber reinforced prepreg sheets using nonwoven fabrics and their precursor webs as reinforcing materials, the formability during shaping and flowability during heat and pressure molding are excellent.

Short fiber reinforced prepreg sheets containing chopped fiber bundles generally have greater variation in basis weight compared to prepreg sheets containing continuous fiber. This is mainly due to the variation in basis weight of the chopped fiber bundle pile, and it is desirable to suppress the variation in basis weight of the chopped fiber bundle pile in order to suppress the variation in basis weight of the short fiber reinforced prepreg sheet and suppress the weight variation of the molded product.

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

The widthwise length of the chopped fiber bundle pile can be controlled by dispersing the chopped fiber bundles in a dispersion area having vertical walls at both ends of the moving body in the widthwise direction that regulate the dispersion width.

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 fed in the width direction of the moving body. For example, when multiple reinforcing fiber bundles are lined up in a row in the width direction of the moving body, cut, and then scattered to produce a chopped fiber bundle deposit, it is possible to control the variation in basis weight in the width direction of the moving body by adjusting the position at which the reinforcing fiber bundles are cut and scattered in the width direction of the moving body. When multiple reinforcing fiber bundles are not fed, for example, there is a method in which the reinforcing fiber bundles are cut and the position at which the chopped carbon fiber bundles are fed is traversed 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. 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.

Furthermore, in order to increase the randomness of the chopped fiber bundle dispersion and to distribute it evenly, chopped fiber bundle piles may be created multiple times on the moving body. For example, multiple chopped fiber bundle pile manufacturing devices may be installed in the direction of travel of the moving body, or the chopped fiber bundle piles may be layered using a cross-wrapping device.

When using a chopped fiber bundle pile to produce a short fiber reinforced prepreg sheet, for example, the moving body is a release film, the upper surface of the unrolled release film is coated with matrix resin, and chopped fiber bundles are piled on the film to produce a chopped fiber bundle pile. After that, a film similarly coated with matrix resin is placed from above with the matrix resin coated surface facing the chopped fiber bundle pile, and pressure is applied from above and below to impregnate the chopped fiber bundle pile with matrix resin, producing a short fiber reinforced prepreg sheet.

In Patent Document 1, the cut chopped fiber bundles are transported and then dispersed, improving the unevenness of the weight per unit area during dispersion. Patent Document 2 clearly shows a chopped fiber bundle deposit with a coefficient of variation of weight per unit area and bulkiness of less than 20%. In Patent Document 3, the prepreg after preparation is pressurized in a state where it is restricted in the width direction, thereby further uniformizing the weight per unit area of the prepreg after impregnation.

JP 2014-210991 A JP 2019-39124 A Patent No. 5822033

In order to suppress variations in basis weight of short fiber reinforced prepreg sheets, 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, variations 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 implemented for the non-product part at the end in the width direction of the short fiber reinforced prepreg sheet.

As mentioned above, the width of the chopped fiber bundle pile can be controlled by spreading the chopped fiber bundle in a spreading area having a vertical wall that regulates the spreading width in the width direction of the moving body. However, if one tries 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 pile up directly below the vertical wall, resulting in an area with a locally high basis weight.

This is a problem that occurs when a vertical wall surface is provided to restrict the spreading width of the chopped fiber bundle pile in the width direction of the moving body, and also occurs when the scattered chopped fiber bundles are dispersed within the spreading area by a dispersion mechanism. Furthermore, if no vertical wall is provided to restrict the spreading width of the chopped fiber bundle pile in the width direction of the moving body, the chopped fiber bundles are spread widely, and the non-product portion becomes extremely large. Thus, it has previously been difficult to control the non-product portion at the widthwise end of the chopped fiber bundle pile.

In response to the above problems, the present invention provides a method for manufacturing a short fiber reinforced prepreg sheet that controls the weight of the ends of the short fiber reinforced prepreg sheet, reduces variation in weight across the sheet width, and reduces the loss width relative to the product width.

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 of cutting reinforcing fiber bundles to a specified bundle length to form chopped fiber bundles; and a spreading step of spreading the obtained chopped fiber bundles onto a moving body that moves continuously in a downstream direction of a 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.
[ 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; and a spreading step of spreading the obtained chopped fiber bundles onto a moving body moving continuously in a downstream direction of the production process to obtain a chopped fiber bundle deposit; 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.

The method for producing a short fiber reinforced prepreg sheet of the present invention controls the basis weight of the ends of the short fiber reinforced prepreg sheet, 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.

The bundle length of the chopped fiber bundle is shown. An example of a method for producing a short fiber reinforced prepreg sheet will be described. The width of the short fiber reinforced prepreg sheet is shown. 1 shows the width of the chopped fiber bundle pile. 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) is a top view, (b) is a side view). 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. 13 shows an example of an obstacle provided inside the standing wall to prevent the chopped fiber bundles from colliding with the standing wall. FIG. 2 is an explanatory diagram showing a measurement area of basis weight/Wf.

The present invention has the above characteristics, and the details of the embodiment of the invention are described below.

The present invention provides a method for producing short fiber reinforced prepreg sheets, 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 on 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 in which both widthwise ends of the moving body are restricted by vertical walls, and after the spreading step is completed, 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 uniform.

The reinforcing fibers used in the present invention include, for example, 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 and converged.

The reinforcing fiber bundle may be a strand that has been subjected to partial splitting. Here, partial splitting refers to a process in which the splitting process is performed intermittently along the orientation direction of the monofilaments that make up the strand. When the ends of the strands that have been subjected to partial 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 of the strand that has been subjected to partial splitting.

There is no particular limit to the number of monofilaments contained in the reinforcing fiber bundle, but it is preferable that the number be 1,000 to 100,000, and more preferably 1,000 to 50,000. This number of monofilaments results in good productivity.

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 the lightest of the reinforcing fibers, and have particularly excellent properties in terms of specific strength and specific elastic modulus. They also have excellent heat resistance and chemical resistance, making them ideal for fiber-reinforced composite materials.

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 dispersed over a wider area. As a result, the chopped fiber bundles come into contact with the vertical wall that regulates the dispersion width in the width direction of the moving body when dispersed, making it difficult to control the basis weight of the ends 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.

A chopped fiber bundle is a reinforcing fiber bundle cut to a specified length. Figure 1 shows an example of the bundle length 101 of a chopped fiber bundle, and the bundle length of the chopped fiber bundle is defined as the monofilament direction length of the two most protruding points in the orientation direction 102 of the monofilaments that make up the chopped fiber bundle.

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

There is no particular restriction on the number of monofilaments in the chopped fiber bundle, but it is preferably 1,000 to 50,000, more preferably 1,000 to 24,000, and even more preferably 1,000 to 4,000. With this number of monofilaments, high mechanical properties can be achieved.

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 decrease. 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.

As the matrix resin, a thermosetting resin or a thermoplastic resin can be suitably used. For example, examples of thermosetting resins include thermosetting resins such as epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, epoxy acrylate resins, phenoxy resins, alkyd resins, urethane resins, maleimide resins, and cyanate resins. In particular, epoxy resins, unsaturated polyester resins, and vinyl ester resins are suitable because they exhibit excellent interfacial adhesion to the reinforcing fibers. As the thermosetting resin, one type may be used alone, or two or more types may be used in combination.

Examples of thermoplastic resins 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. Thermoplastic resins may be used alone or in combination of two or more types.

A prepreg sheet is a sheet made by impregnating reinforcing fibers with a matrix resin, semi-curing or thickening the resin, and then treating the resin so that it can be handled as a sheet. Reinforcing fibers used in prepreg sheets include continuous fibers and short fibers. The present invention relates to a short fiber reinforced prepreg sheet that uses short fibers.

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, the chopped fiber bundle is cut and then spread on a moving body moving in the downstream direction of the manufacturing process to produce the chopped fiber bundle deposit. On the other hand, nonwoven fabrics are produced by dry methods, wet methods, spunbonding methods, meltblown methods, airlaid methods, etc., and methods for bonding webs to produce nonwoven fabrics include dipping methods, spraying methods, thermal bonding methods, needle punching methods, and hydroentanglement methods. The number of entanglement points in 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, or 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 reinforcing materials. The present invention relates to a method for manufacturing short fiber reinforced prepreg sheets using chopped fiber bundles.

The basis weight is the mass per unit area. The basis weight of short fiber reinforced prepreg sheets or chopped fiber bundle piles can be measured by placing a cutout mold of a specified size on the short fiber reinforced prepreg sheet to cut out a sample, or by measuring the weight of a sample cut to a specified size with a roller cutter, and then dividing the sample weight by the sample area.

When the average weight per unit area of the short fiber reinforced prepreg sheet in the entire width direction is high, a molded product can be produced efficiently, but if it is too high, problems such as poor impregnation occur. Therefore, it is preferable that the average weight per unit area of the short fiber reinforced prepreg sheet in the entire width direction is 1000 g/m ² to 4000 g/m ² .

The representative value of the basis weight of a short fiber reinforced prepreg sheet is the average basis weight across the entire width of the short fiber reinforced prepreg sheet. This basis 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 along a straight line that defines the width of the short fiber reinforced prepreg sheet, measuring the weight of the resulting sample, and dividing the measured weight by the area calculated from the widthwise length of the sample (prepreg sheet width) and the longitudinal length of the sample short fiber reinforced prepreg sheet.

Wf is the mass ratio of reinforcing fibers contained in the short fiber reinforced prepreg sheet. If Wf is small, the reinforcing effect of the reinforcing fibers is small, and if Wf is large, impregnation failure may occur, resulting in the formation of defects when the product is molded. 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.

To measure Wf, a sample is taken from the short fiber reinforced prepreg sheet, and then it can be measured, for example, according to the combustion method, nitric acid and sulfuric acid decomposition method described in JIS K7075 Test method for fiber content and void content of carbon fiber reinforced plastics, or JIS K7052 Long glass fiber reinforced plastics - Prepregs, molding materials and molded products - Determination of long glass fiber and inorganic filler content - Firing method. If the sample size is large, it is divided into smaller pieces and the Wf of each divided sample is measured.

The representative value of Wf for a short fiber reinforced prepreg sheet is the average Wf of the entire width of the short fiber reinforced prepreg sheet in the width direction. This Wf is measured 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, then cutting the sheet in a straight line that defines the width of the short fiber reinforced prepreg sheet, and measuring the resulting sample using the above-mentioned Wf measurement method.

An example of a method for manufacturing 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 manufactured, for example, using the device shown in Figure 2, which performs the following resin sheet preparation process, cutting/spraying process, and impregnation process.

<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.

A long second release film 212 is pulled out from the second sheet roll 211 and fed to the second conveyor 222. A doctor blade applies a predetermined amount of matrix resin paste to the upper surface of the second release film 212 in a predetermined thickness using a second resin bath 213, forming a second resin sheet 214.

<Cutting and spraying process>
In the cutting and scattering process, the reinforcing fiber bundle 232 supplied from the bobbin 231 on which the continuous reinforcing fiber bundle is wound is pulled out, passed through a nip roll 233, and then 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 which the cut angle θ is within the range of 0°<θ≦90°. Here, the cut angle is the smaller of the angles formed by the fiber orientation direction and the cutting line, and is within 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 hinder the object of the present invention, and examples thereof include a guillotine blade type and a rotary cutter type. As described above, the orientation 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 having different bundle lengths, a method in which a plurality of cutters 234 are prepared and discontinuous reinforcing fiber bundles having different bundle lengths are obtained, for example.

When scattering the cut chopped fiber bundles 241, scattering can be performed within a scattering area in which both widthwise ends of the moving body are restricted by vertical walls 242. A distributor 243 may be disposed within the scattering area to disperse the chopped fiber bundles.

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

<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.

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 of the sheet where the ratio of the areas where chopped fiber bundles are present to the areas where they are not present is 50% when the short fiber reinforced prepreg sheet is viewed from above as shown in Figure 3, and the short fiber reinforced prepreg sheet end refers to the straight lines. When short fiber reinforced prepreg sheets can be produced stably, 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.

The width of the chopped fiber bundle pile is the distance between two straight lines parallel to the longitudinal direction of the chopped fiber bundle pile at which the ratio of areas where chopped fiber bundles are present to areas where they are not present is 50% when the chopped fiber bundle pile is viewed from above as shown in Figure 4. When chopped fiber bundle piles can be produced stably, the sheet width is stable when calculated from a section of at least 300 mm in the longitudinal direction of the prepreg sheet, so the sheet width is calculated from a section of at least 300 mm in the longitudinal direction of the prepreg sheet.

It is desirable to carry out the scattering of chopped fiber bundles in a scattering area having a vertical wall that regulates the scattering width in the width direction of the moving body. By carrying out scattering in such a scattering area, the width of the chopped fiber bundle deposit can be controlled. It is also preferable to set the width of the chopped fiber bundle deposit 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 during the impregnation process, and leakage of matrix resin from the ends can be suppressed.

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 ends of the chopped fiber bundle pile is to be maintained equal to that of the center, the chopped fiber bundles that come into contact with the vertical wall surface that regulates the spray width during spraying will accumulate 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 that includes a step of spreading and leveling outward in the width direction the chopped fiber bundles contained in the high weight regions formed at both ends of the chopped fiber bundle pile. This method eliminates the locally high weight regions caused by the chopped fiber bundles that accumulate directly below the vertical wall of the chopped fiber bundle pile, making it possible to produce chopped fiber bundles with a uniform weight up to the ends, and controlling the weight of the ends of the short fiber reinforced prepreg sheet, thereby making it possible to provide a short fiber reinforced prepreg sheet with small weight fluctuations in the width direction of the short fiber reinforced prepreg sheet and small loss width relative to the product width.

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

As illustrated in FIG. 5 ((a) top view, (b) side view), a baffle plate or roll is provided downstream of the chopped fiber bundle spraying area so as to extend outward in the downstream direction, eliminating areas with locally high basis weight that occur when 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 directly below the vertical wall, thereby controlling the basis weight at the ends of the short fiber reinforced prepreg sheet, and providing 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.

The material of the baffle plate or roll is not particularly limited, but it is preferable that the surface is smooth and non-static. Such a material can prevent the chopped fiber bundles from adhering to the surface of the baffle plate or roll when it comes into contact with the chopped fiber bundle pile.

When viewed from the vertical top surface of the moving body, the angle between the baffle plate or roll and the width direction of the moving body can be a value between 0° and 90°, but it is preferable to set it to 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.

The dimensions of the baffle plate or roll are not particularly limited, but it is preferable that when installed, the baffle plate or roll has a height that can regulate the height of the chopped fiber bundle pile from the area with a locally high basis weight directly below the vertical wall to the area where the chopped fiber bundle is moved. If it 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.

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 caused by the chopped fiber bundles accumulated directly below the vertical wall. At such a height, the chopped fiber bundles in the area with locally high basis weight can be continuously moved to the outside of the chopped fiber bundles.

In addition, multiple baffles or rolls may be provided so that the height of the lowest end gradually decreases in the downstream direction. By installing multiple baffles or rolls in this way, the chopped fiber bundle can be gradually moved toward the end.

The height of the baffle plate or the diameter of the roll should 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 directly below the vertical wall and the height of the target basis weight area, and is preferably at least twice the height difference.

The present invention also provides a method for producing short fiber reinforced prepreg sheets, which includes a cutting step in which reinforcing fiber bundles are cut to a specified bundle length to produce chopped fiber bundles, followed by a spreading step in which the resulting chopped fiber bundles are spread on a moving body that moves continuously in the downstream direction of the production process to obtain a chopped fiber bundle deposit, and the spreading step is carried out within a spreading area in which both ends of the moving body in the width direction are restricted by standing walls, and the method includes a section in which the distance between the standing walls gradually increases downstream of the production process.

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 allows the locations where the chopped fiber bundles are deposited in contact with the vertical wall surfaces that restrict the spray width during spraying of both ends of the chopped fiber bundle pile to be distributed in the width direction of the fiber bundle pile, preventing the occurrence of areas with locally high basis weight at the ends of the chopped fiber bundles. This controls the basis weight at the ends of the short fiber reinforced prepreg sheet, and allows the provision of 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.

There is no particular restriction on the length of the gradual increase section in the direction of the moving body, but it is preferable that there is no gradual increase section at the downstream end of the moving body of the dispersion area, and that there is a section at the downstream end of the moving body where the vertical wall is parallel to the downstream direction of the moving body for 3% or more of the length of the dispersion area in the direction of the moving body. This configuration stabilizes the basis weight at the end of the chopped fiber bundle pile.

There is no particular limit to the gradual increase in the distance between the vertical walls, but if it is 10% or more and 500% or less of the average bundle length of the chopped fiber bundles, the basis weight of the end of the chopped fiber bundle pile will be stable.

The present invention also provides a method for producing short fiber reinforced prepreg sheets, which includes a cutting process in which reinforcing fiber bundles are cut to a specified bundle length to produce chopped fiber bundles, followed by a spreading process in which the resulting chopped fiber bundles are spread on a moving body that moves continuously in the downstream direction of the production process to obtain a chopped fiber bundle deposit, and the spreading process is carried out within a spreading area in which both ends of the moving body in the width direction are restricted by vertical walls, and an obstacle is provided on the inside of the vertical wall to prevent the chopped fiber bundles from colliding with the vertical wall.

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 prevents the occurrence of areas with locally high basis weight at the end of the chopped fiber bundle pile, controls the basis weight at the end 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.

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 come into contact with the standing wall from coming into contact with the wall, but it is preferable for the obstacle to have a smooth surface that is not electrostatically charged, and it is preferable for the obstacle to have a slope so that the chopped fiber bundles do not accumulate.

There are no particular limitations on the shape of the obstacle, 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 inward in the width direction of the moving body.

The amount of protrusion 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 if it is within this range, the basis weight of the chopped fiber bundle pile end will be stable. Furthermore, if multiple obstacles are installed, the protrusion amount of each can be varied within the above range, allowing for fine control of the position at which the chopped fiber bundles are scattered at the width direction end.

The present invention will be explained in more detail below with reference to the following examples.

Example 1
A polypropylene release film was unwound from a roll, and a matrix resin was uniformly applied to the upper surface of the film using a doctor blade, adjusting the amount and width of application to produce two resin sheets. At this time, the coating weight of each resin was 430 g/ ^m2 , and the coating width was 1490 mm.

Matrix Resin:
A resin obtained 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.

Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as the 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.

The chopped fiber bundles are spread on the matrix resin of the first release film, which is continuously drawn out while the matrix resin is applied to the upper surface of the moving body, in a spreading area having a vertical wall that restricts the spreading width in the width direction of the moving body, forming a chopped fiber bundle deposit on the moving body.

The spray 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.

At this time, the chopped fiber bundles were scattered while cutting 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 a line at equal intervals in the width direction of the moving body. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g/ ^m2 .

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 from the right hand side, it rotated at a speed of 400 rpm in a clockwise direction with respect to the rotation axis of the distributor to disperse the scattered chopped fiber bundles within the spraying area.

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

The width of the chopped fiber bundle pile obtained in this manner was 1,495 mm. The chopped fiber bundle pile obtained did not produce a high basis weight area due to chopped fiber bundles that had been deposited in contact with the vertical wall surface and directly below the vertical wall surface.

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 resulting SMC was 1500 mm.

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

In addition, 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 of the SMC in the width direction were calculated to be 2000 g/ ^m2 and Wf 57%, respectively.

Furthermore, as shown in FIG. 8 , a boundary line was set 6.35 mm inward from the end of the obtained SMC in the width direction, and a rectangular region measuring Lb = 24.79 mm in the SMC width direction and 200 mm in the longitudinal direction was provided on the inside 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, and the weight per unit area and Wf of the rectangular region were calculated. The weight per unit area was 1920 g/ ^m2 , which was 96% of the average weight per unit area of the SMC in the width direction, and Wf was 56%, which was 98% of the average Wf of the SMC in the width direction.

As shown in Figure 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC length direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% to 120% in all rectangular regions.

As shown in Figure 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 of the SMC width direction, the basis weight at the outermost end was lower than that of the region one step inside.

Example 2
A polypropylene release film was unwound from a roll, and a matrix resin was uniformly applied to the upper surface of the film using a doctor blade, adjusting the amount and width of application to produce two resin sheets. At this time, the coating weight of each resin was 430 g/ ^m2 , and the coating width was 1490 mm.

Matrix Resin:
A resin obtained 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.

Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as the 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.

The chopped fiber bundles are spread on the matrix resin of the first release film, which is continuously drawn out while the matrix resin is applied to the upper surface of the moving body, in a spreading area having a vertical wall that restricts the spreading width in the width direction of the moving body, forming a chopped fiber bundle deposit on the moving body.

At this time, the chopped fiber bundles were scattered while cutting the reinforcing fiber bundles that had been fed at equal intervals in a row 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 row in the width direction of the moving body. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g/ ^m2 .

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, it rotated at a speed of 400 rpm in a clockwise direction with respect to the rotation axis of the distributor to disperse the scattered chopped fiber bundles within the spraying area.

The spray 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.

In addition, the vertical walls that regulate the dispersion width in the width direction of the moving body in the dispersion region did not have a section parallel to the downstream direction of the moving body where the distance between the vertical walls gradually increased. The resulting chopped fiber bundle deposit had a high basis weight region at the end of the chopped fiber bundle deposit due to chopped fiber bundles that had contacted the vertical wall surface and accumulated 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.

The chopped fiber bundles contained in the high basis weight region of the resulting chopped fiber bundle pile were then moved to the end side of the chopped fiber bundle pile using a baffle plate. The baffle plate was a stainless steel flat plate with a thickness of 2 mm, width of 150 mm, and height of 70 mm, and was attached so that its lower end in the height direction was 16 mm high. The angle formed by the baffle plate or roll and the moving body in the width direction at this time was 45°. The widthwise center position of the baffle plate and the center of the vertical 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.

The width of the chopped fiber bundle pile obtained in this manner was 1,495 mm.

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 resulting SMC was 1500 mm.

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

In addition, 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 of the SMC in the width direction were calculated to be 2000 g/ ^m2 and Wf 57%, respectively.

Furthermore, as shown in FIG. 8 , a boundary line was set 6.35 mm inward from the end of the obtained SMC in the width direction, and a rectangular region measuring Lb = 24.79 mm in the SMC width direction and 200 mm in the longitudinal direction was provided on the inside 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, and the weight per unit area and Wf of the rectangular region were calculated. The weight per unit area was 1912 g/ ^m2 , which was 96% of the average weight per unit area of the SMC in the width direction, and Wf was 56%, which was 98% of the average Wf of the SMC in the width direction.

As shown in Figure 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC length direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% to 120% in all rectangular regions.

As shown in Figure 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 of the SMC width direction, the basis weight at the outermost end was lower than that of the region one step inside.

Example 3
A polypropylene release film was unwound from a roll, and a matrix resin was uniformly applied to the upper surface of the film using a doctor blade, adjusting the amount and width of application to produce two resin sheets. At this time, the coating weight of each resin was 430 g/ ^m2 , and the coating width was 1490 mm.

Matrix Resin:
A resin obtained 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.

Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as the 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.

The chopped fiber bundles were spread on 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 spreading area having a wall that restricted the spreading width in the width direction of the moving body, forming a chopped fiber bundle deposit on the moving body.

The spray 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.

At this time, the chopped fiber bundles were scattered while cutting the reinforcing fiber bundles that had been fed at equal intervals in a row 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 row in the width direction of the moving body. In addition, the basis weight of the chopped fiber bundle deposit was 1140 g/ ^m2 .

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, it rotated at a speed of 400 rpm in a clockwise direction with respect to the rotation axis of the distributor to disperse the scattered chopped fiber bundles within the spraying area.

In addition, the vertical walls that regulate the dispersion width in the width direction of the moving body in the dispersion region are parallel to the downstream direction of the moving body, and do not have a section where the distance between the vertical walls gradually increases. The resulting chopped fiber bundle deposit had high basis weight areas at the ends of the chopped fiber bundle deposit due to chopped fiber bundles that contacted the vertical wall surfaces and accumulated directly below the vertical wall surfaces. The height of the high basis weight areas of the chopped fiber bundle deposit was 20 mm, and the height of the other areas was 15 mm.

In addition, the vertical walls that regulate the spray width in the width direction of the moving body in the spraying area have 20 cylindrical shapes protruding diagonally downward from the side of the vertical wall, 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 cylinders and the vertical downward is 60°.

The width of the chopped fiber bundle pile obtained in this manner was 1,495 mm. The chopped fiber bundle pile obtained did not produce a high basis weight area due to chopped fiber bundles that had been deposited in contact with the vertical wall surface and directly below the vertical wall surface.

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 resulting SMC was 1500 mm.

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

In addition, 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 of the SMC in the width direction were calculated to be 2000 g/ ^m2 and Wf 57%, respectively.

As shown in FIG. 8 , a boundary line was set 6.35 mm inward from the end of the obtained SMC in the width direction, and a rectangular region measuring Lb = 24.79 mm in the SMC width direction and 200 mm in the longitudinal direction was provided on the inside 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 weight per unit area and Wf of the rectangular region were calculated to be 1940 g/ ^m2 , which was 97% of the average weight per unit area of the SMC in the width direction, and Wf was 56%, which was 98% of the average Wf of the SMC in the width direction.

As shown in Figure 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC length direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% to 120% in all rectangular regions.

As shown in Figure 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 of the SMC width direction, the basis weight at the outermost end was lower than that of the region one step inside.

Example 4
A polypropylene release film was unwound from a roll, and a matrix resin was uniformly applied to the upper surface of the film using a doctor blade, adjusting the amount and width of application to produce two resin sheets. At this time, the coating weight of each resin was 430 g/ ^m2 , and the coating width was 1490 mm.

Matrix Resin:
A resin obtained 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.

Next, a continuous carbon fiber strand with 50,000 filaments (manufactured by ZOLTEK, product name: "ZOLTEK (registered trademark)" PX35-50K) was used as the 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.

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

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/ ^m2 .

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 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, it rotated at a speed of 400 rpm in a clockwise direction with respect to the rotation axis of the distributor to disperse the scattered chopped fiber bundles within the spraying area.

The spray 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.

In addition, the vertical walls that regulate the spray width in the width direction of the moving body in the spraying area did not have a section that was parallel to the downstream direction of the moving body and in which the distance between the vertical walls gradually increased. 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 so as to protrude downward from the vertical wall at an angle of 60°.

The width of the chopped fiber bundle pile obtained in this manner was 1,495 mm. The chopped fiber bundle pile obtained did not produce a high basis weight area due to chopped fiber bundles that had been deposited in contact with the vertical wall surface and directly below the vertical wall surface.

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 resulting SMC was 1500 mm.

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

In addition, 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 of the SMC in the width direction were calculated to be 2000 g/ ^m2 and Wf 57%, respectively.

As shown in FIG. 8 , a boundary line was set 6.35 mm inward from the end of the obtained SMC in the width direction, and the short fiber reinforced prepreg sheet was provided on the inner side of the boundary line so that the long side of a rectangular region measuring Lb = 24.79 mm in the SMC width direction and 200 mm in the longitudinal direction overlapped with the boundary line. The weight per unit area and Wf of the rectangular region were calculated to be 2010 g/ ^m2 , which was 101% of the average weight per unit area of the SMC in the width direction, and Wf was 57%, which was 100% of the average Wf of the SMC in the width direction.

As shown in Figure 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC length direction were cut from the boundary line from the obtained SMC, the average basis weight was 98% or more and 103% or less in all rectangular regions.

As shown in Figure 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 of the SMC width direction, the basis weight at the outermost end was lower than that of the region one step inside.

(Comparative Example 1)
An SMC was produced in the same manner as in Example 1, except that the chopped fiber bundles were dispersed in a dispersion region in which the vertical wall that restricted the dispersion 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 accumulated 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.

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

In addition, 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 of the SMC in the width direction were calculated to be 2000 g/ ^m2 and Wf 57%, respectively.

Furthermore, as shown in FIG. 8 , a boundary line was set 6.35 mm inward from the end of the obtained SMC in the width direction, and a rectangular region measuring Lb = 24.79 mm in the SMC width direction and 200 mm in the longitudinal direction was provided on the inside 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, and the weight per unit area and Wf of the rectangular region were calculated. The weight per unit area was 2120 g/ ^m2 , which was 106% of the average weight per unit area of the SMC in the width direction, and Wf was 60%, which was 105% of the average Wf of the SMC in the width direction.

As shown in Figure 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC length direction were cut out from the obtained SMC along the boundary line, the average basis weight was 80% to 120% in all rectangular regions.

As shown in Figure 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 of the SMC width direction, the basis weight of the outermost end was higher than that of the region one step inside.

(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 reinforcement fiber bundles were fed during cutting was narrowed to the center. 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.

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

In addition, 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 of the SMC in the width direction were calculated to be 2000 g/ ^m2 and Wf 57%, respectively.

Furthermore, as shown in FIG. 8 , a boundary line was set 6.35 mm inward from the end of the obtained SMC in the width direction, and the short fiber reinforced prepreg sheet was provided on the inner side of the boundary line so that the long side of a rectangular region measuring Lb = 24.79 mm in the SMC width direction and 200 mm in the longitudinal direction overlapped the boundary line, and the weight per unit area and Wf of the rectangular region were calculated. The weight per unit area was 1560 g/ ^m2 , which was 78% of the average weight per unit area of the SMC in the width direction, and Wf was 45%, which was 79% of the average Wf of the SMC in the width direction.

As shown in Figure 8, when 60 rectangular regions measuring 24.79 mm in the SMC width direction × 200 mm in the SMC length direction were cut from the boundary line from the obtained SMC, the average basis weight was 80% to 120% in all rectangular regions.

As shown in Figure 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 of the SMC width direction, the basis weight of the outermost end was higher than that of the region one step inside.

Molded products using short fiber reinforced prepreg sheets produced by the manufacturing method of the present invention can be suitably used in automobiles and other transportation equipment.

101: bundle length 102: orientation direction 201: first sheet roll 202: first release film 203: first resin bath 204: first resin sheet 211: second sheet roll 212: second release film 213: second resin bath 214: second resin sheet 221: first conveyor 222: second conveyor 231: bobbin 232: reinforcing fiber bundle 233: nip roll 234: cutter 241: chopped fiber bundle 242: standing wall 243: distributor 244: chopped fiber bundle deposit 251 : Short fiber reinforced prepreg sheet precursor 252: Pressurizing 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 body moving direction 601: Standing wall 602: Gradual increase section 603: Moving body moving direction 701: Obstacle 702: Chopped fiber bundle 703: Standing wall 801: Boundary line 802: Moving body moving direction

Claims (2)

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 a spreading step in which the obtained chopped fiber bundles are spread onto a moving body that moves continuously in a downstream direction of a production process to obtain a chopped fiber bundle deposit; the spreading step is carried out within a spreading area in which both widthwise ends of the moving body are restricted by standing walls, and the spreading step has a section in which the distance between the standing walls gradually increases downstream of the production process. A method for manufacturing short fiber reinforced prepreg sheets, which includes a cutting process in which reinforced fiber bundles are cut to a specified bundle length to form chopped fiber bundles, followed by a spreading process in which the resulting 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 process being carried out within a spreading area that is restricted 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.

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