JP2009114612A - Method for producing chopped fiber bundle and molding material, molding material, and fiber-reinforced plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a chopped fiber bundle and a molding material, which has good impregnating ability, fluidity and followability in molding when used as a molding material, and exhibits excellent dynamic properties when formed into fiber-reinforced plastic, and to provide a molding material and fiber-reinforced plastics both obtained by using the chopped fiber bundle. <P>SOLUTION: The method for producing chopped fiber bundle and a molding material includes continuously supplying a fiber bundle at a predetermined angle between a pair of rollers, at least one of which rollers is in a direction parallel with the rotation axis of the one roller and has blades arranged at equal intervals in the circumferential direction of the one roller, and cutting the fiber bundle to have a predetermined fiber length by bringing the blades attached on the one roller into contact with the receiving part of the other roller of the roller, and the molding material and the fiber-reinforced plastic are obtained by using the chopped fiber bundle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention, when used as a molding material, has a good impregnation property, fluidity, molding followability, and when used as a fiber reinforced plastic, a chopped fiber bundle that exhibits excellent mechanical properties and a method for producing the molding material, In addition, the present invention relates to a molding material and fiber reinforced plastic obtained using the chopped fiber bundle.

  Fiber reinforced plastic consisting of reinforced fiber and matrix resin is attracting attention in industrial applications because it has high specific properties, high specific modulus, excellent mechanical properties, weather resistance, chemical resistance, etc. The demand is increasing year by year.

  As a molding method of fiber reinforced plastic having high functional properties, a semi-cured intermediate base material impregnated with matrix resin is laminated on continuous reinforcing fiber called prepreg, and heated and pressurized in a high temperature and high pressure kettle. Autoclave molding in which a matrix resin is cured and a fiber reinforced plastic is molded is most commonly performed. In recent years, for the purpose of improving production efficiency, RTM (resin transfer molding) molding in which a continuous fiber base material previously shaped into a member shape is impregnated with a matrix resin and cured has been performed. The fiber reinforced plastics obtained by these molding methods have excellent mechanical properties because they are continuous fibers. Further, since the continuous fibers are regularly arranged, it is possible to design the mechanical properties required by the arrangement of the base material, and the variation in the mechanical properties is small. However, on the other hand, it is difficult to form a complicated shape such as a three-dimensional shape because it is a continuous fiber, and it is mainly limited to members close to a planar shape.

  As a molding method suitable for a complicated shape such as a three-dimensional shape, there is a molding using an SMC (sheet molding compound) or a stampable sheet. An SMC molded product is a sheet in which a fiber bundle of reinforcing fibers is cut in a direction perpendicular to the fiber so that the fiber length is, for example, about 25 mm, and the chopped fiber bundle is impregnated with a matrix resin that is a thermosetting resin to be in a semi-cured state It is obtained by heating and pressurizing the shaped substrate (SMC) using a heating type press. A stampable sheet molded product is obtained by thermoplasticizing a sheet-like base material (stampable sheet) in which a thermoplastic resin is impregnated with a chopped fiber bundle cut to about 25 mm or a nonwoven mat made of continuous reinforcing fibers with an infrared heater. It is obtained by heating above the melting point of the resin, laminating on a mold at a predetermined temperature, and cooling and pressurizing.

  In many cases, the SMC or stampable sheet is cut smaller than the shape of the molded body before being pressed, placed on the mold, and stretched (flowed) into the shape of the molded body by pressing. Therefore, it is possible to follow a complicated shape such as a three-dimensional shape by the flow. However, in SMC and stampable sheets, uneven distribution and alignment unevenness of chopped fiber bundles and non-woven mats are inevitably generated in the sheeting process, so that mechanical properties are deteriorated or the variation of the values becomes large. End up. Further, due to the uneven distribution and uneven alignment, warpage, sink marks, and the like are likely to occur particularly in thin members.

  In order to fill the drawbacks of the above-mentioned materials, chopped fiber bundles with a reduced number of reinforcing fibers are applied to SMC, etc., and the entanglement between chopped fiber bundles is increased and densified to suppress crack generation and progress. A base material is disclosed (for example, Patent Document 1). However, in general, reducing the number of reinforcing fibers to be focused has a high cost in the process, and there is a problem that mechanical characteristics are easily lowered due to uneven distribution and uneven orientation.

On the other hand, there is a disclosure relating to a glass chop strand having a cut surface angle of 10 to 80 °, which is suitable for manufacturing glass paper (for example, Patent Document 2). In this disclosure, there is a description that by using glass chop strands having an oblique cut surface, the chop strands can be easily opened to single fibers when paper is made. However, this chop strand uses 4,000 thin glass fibers and is intended to improve the spreadability in papermaking. In addition, chop strands (fiber bundles) are not used as fiber reinforced plastics in the first place, and there are no descriptions regarding mechanical properties, fiber variability, warpage, sink marks, etc. as fiber reinforced plastics. There is no detailed disclosure regarding the manufacturing method.
JP-A-01-163218 JP 2003-165739 A

  In view of the background of the prior art, the present invention has excellent impregnation property, fluidity, molding followability when used as a molding material, and when it is used as a fiber reinforced plastic, chopped fiber that exhibits excellent mechanical properties. It is an object of the present invention to provide a method for producing a bundle and a molding material, and a molding material and a fiber reinforced plastic obtained by using the chopped fiber bundle.

  The present invention employs the following means in order to solve such problems. That is, a method for producing a chopped fiber bundle by cutting a fiber bundle in which reinforcing fibers are substantially aligned in one direction to obtain a chopped fiber bundle, wherein at least one roller is parallel to the rotation axis of the roller. And a blade attached to the roller by continuously supplying the fiber bundle between a pair of rollers which are rollers that are arranged in the circumferential direction of the roller and arranged at equal intervals. When the fiber bundle is cut by bringing the receiving portion of the other roller of the roller into contact with each other, the angle formed by the blade attached to the roller and the fiber orientation direction of the fiber bundle is in the range of 2 to 30 °. A fiber bundle is supplied, the fiber bundle is brought into contact with a blade attached to the roller, and the fiber bundle is cut so that the fiber length of reinforcing fibers constituting the fiber bundle is 5 to 100 mm. Method for producing de fiber bundle, and the molding material obtained by using the chopped fiber bundle is a fiber-reinforced plastic.

  Further, a chopped fiber bundle spreading step of spreading the chopped fiber bundle obtained by the manufacturing method so that the plurality of chopped fiber bundles are deposited in one layer or a plurality of layers on the molding substrate, and spreading on the molding substrate A chopped fiber bundle assembly forming step of forming a molding material composed of a chopped fiber bundle assembly by integrating a large number of chopped fiber bundles together to form a molding material manufacturing method.

  When the chopped fiber bundle produced according to the present invention is used as a molding material, it has good impregnation properties, fluidity, and molding followability, and can exhibit excellent mechanical properties when used as a fiber reinforced plastic. .

  In order to obtain a chopped fiber bundle having excellent impregnation property, fluidity and molding followability when used as a molding material and exhibiting excellent mechanical properties when used as a fiber reinforced plastic, the present inventors have earnestly By studying, producing a chopped fiber bundle by a specific cutting method for a fiber bundle in which continuous reinforcing fibers are aligned in one direction, and molding the chopped fiber bundle by integrating and molding it with a molding material, They sought to solve this problem all at once. In the present specification, unless otherwise specified, in the term including fiber or fiber (for example, “fiber direction” or the like), the fiber represents a reinforcing fiber. In the present specification, the continuous fiber refers to a reinforcing fiber having a fiber length longer than 100 mm.

  The method for producing a chopped fiber bundle according to the present invention is a method for producing a chopped fiber bundle, wherein a chopped fiber bundle is obtained by cutting a fiber bundle in which reinforcing fibers are substantially aligned in one direction. The fiber bundle is continuously supplied between a pair of rollers, the rollers being parallel to the rotation axis of the roller and having the blades arranged at equal intervals in the circumferential direction of the roller. When the fiber bundle is cut by bringing the blade attached to the roller into contact with the receiving portion of the other roller of the roller, the angle formed by the blade attached to the roller and the fiber orientation direction of the fiber bundle is 2 to 30 The fiber bundle is supplied in the range of °, the fiber bundle is brought into contact with a blade attached to a roller, and the fiber bundle is cut so that the fiber length of the reinforcing fibers constituting the fiber bundle is 5 to 100 mm.

  In the present invention, “substantially aligned in one direction” means that 90% or more of the reinforcing fiber group existing within a radius of 5 mm is included in the fiber bundle when attention is paid to a part of the fiber bundle. The orientation is within ± 10 ° from a certain fiber angle. In the present invention, the “rotation axis parallel direction” refers to a direction in which an angle formed between the direction and the rotation axis is within ± 5 °. In the present invention, the “receiving portion” refers to the surface of the other roller against which the fiber bundle is pressed by a blade attached to the roller. In the present invention, the “angle formed by the blade and the fiber orientation direction of the fiber bundle” means that the ridge line direction of the blade edge when the fiber bundle is pressed against the blade and the fiber orientation direction of the fiber bundle. It means the absolute value of the angle formed.

  Conventionally, as shown in FIG. 1, a chopped fiber bundle is substantially unidirectional between a pair of rollers of a roller 2 to which a blade 1 is attached in advance and another roller 3 paired therewith. The fiber bundle 4 in which the reinforcing fibers are aligned is cut in the fiber orthogonal direction by inserting the fiber bundle 4 so that the ridge line direction 6 of the blade edge of the blade 1 and the fiber orientation direction of the fiber bundle 4 are orthogonal to each other, A chopped fiber bundle 5 was obtained. The conventional chopped fiber bundle 5 thus obtained has a rectangular shape.

  However, it has been known that fiber reinforced plastics molded using conventional chopped fiber bundles have extremely low strength. Therefore, the present inventors have identified the cause of low strength by conducting a detailed study on the fracture process of the reinforced plastic. Most of the load applied to the fiber reinforced plastic is handled by the reinforced fiber, but the chopped fiber bundle is a form in which the reinforced fiber is cut, so the load borne by the reinforced fiber must be transferred to the surrounding reinforced fiber via the resin. I have to hand it over. As shown in FIG. 2, in the conventional chopped fiber bundle 5, all the reinforcing fibers 10 are cut at the same position in the fiber orientation direction 9, and the end portion of the chopped fiber bundle in the fiber orientation direction is subjected to the load that the reinforcing fiber 10 has taken. 11 has to be handed over to the surroundings at a stretch, causing stress concentration. Therefore, even if the load is low, the end portion 11 of the chopped fiber bundle in the fiber orientation direction is broken due to stress concentration and cracks are generated, and these cracks are connected to each other to break the entire fiber reinforced plastic.

  In order to improve the strength of the fiber reinforced plastic, it is conceivable to reduce the number of reinforcing fibers contained in the chopped fiber bundle. Since the load delivered to the periphery at the end portion of the chopped fiber bundle is reduced, the influence range of the stress concentration is small, and even if a crack occurs, the cracks are not easily connected to each other, resulting in an improvement in strength. Ultimately, it is presumed that the strength is most improved by dispersing at the reinforcing fiber single yarn level. However, it is very difficult to reduce the number of reinforcing fibers contained in the chopped fiber bundle industrially. In order to improve the strength of glass fiber, etc., it can be manufactured by dividing the fiber bundle and dividing the number of reinforcing fibers into pieces, and then cutting it, but the cost is increased by adding a fiber separation process. . In addition, when fiber bundles are split into carbon fibers, fluff is generated, and the number of reinforcing fibers cannot be subdivided substantially stably. Also, when trying to disperse the reinforcing fibers at the single yarn level, it is very difficult to disperse each reinforcing fiber while maintaining the straightness of the reinforcing fibers, and the reinforcing fibers are aggregated and eventually Since the strength is lowered, there is a problem that it is difficult to go through an industrial molding material manufacturing process.

  Further, the shape of the conventional chopped fiber bundle 5 is a rectangular shape as shown in FIG. 2, whereas the shape of the chopped fiber bundle 12 of the present invention is a parallelogram shape as shown in FIG. Comparing the aggregates (cut ends) 11 at the ends of the two reinforcing fibers, the chopped fiber bundle 12 of the present invention shown in FIG. 8 has a clearly longer cut end 11. Due to the long cut end 11, when producing a molding material using a chopped fiber bundle, when the chopped fiber bundle is impregnated with a matrix resin, it is expected to show extremely good impregnation properties compared to the conventional one. It was also one of the features of the present invention that an outside effect was obtained. In this respect, it is clearly different from Japanese Patent Laid-Open No. 2003-165739 (Patent Document 2).

  Therefore, the inventors insert the fiber bundle 4 so that the angle formed by the ridge line direction 6 of the blade edge of the blade 1 and the fiber orientation direction of the fiber bundle 4 is 2 to 30 ° as shown in FIG. A new method for producing a chopped fiber bundle was found. The schematic of the manufacturing method seen from the rotating shaft direction of the roller is shown to Fig.4 (a)-(d). Moreover, the schematic of the manufacturing method seen from the roller 2 with which the blade 1 was attached to the roller 3 direction used as a pair is shown to Fig.5 (a)-(d).

  In the manufacturing method according to the present invention, first, as shown in FIG. 4A and FIG. 5A, the edge line of the blade edge of the blade 1 between the roller 2 to which the blade 1 is attached and the other roller 3. The fiber bundle 4 is inserted so that the angle formed by the direction 6 and the fiber orientation direction of the fiber bundle 4 is 2 to 30 °, and the fiber bundle 4 is cut while being pressed against the receiving portion of the roller 3. At this time, the fiber bundle 4 is temporarily held by the blade 1 and the receiving part of the roller 3. Next, as shown in FIGS. 4B and 5B, the fiber bundle 4 held by the receiving portion of the blade 1 and the roller 3 is released with the rotation of the roller 2 and the roller 3. In the meantime, the fiber bundle 4 is sent in the traveling direction 14. Furthermore, if the said roller 2 and the roller 3 rotate with progress of time, as shown in FIG.4 (c), FIG.5 (c), the receiving part of the blade 1 and the roller 3 will contact again, and the fiber bundle 4 is accompanying with it. Is cut. By repeating this operation, a chopped fiber bundle 12 can be obtained as shown in FIGS. 4 (d) and 5 (d). As shown in FIG. 8, the chopped fiber bundle produced according to the present invention has a parallelogram shape, and the insertion length 18 in the fiber orientation direction is larger than the fiber length. It is. Note that, as described above, in the present invention, the rotation axis parallel direction is defined as a direction in which the angle between the direction and the rotation axis is within ± 5 ° which is a range that does not impair the object of the present invention. Strictly speaking, the geometrical parallelogram may not be obtained, but the angle formed by the cut portion of the chopped fiber bundle (the end portion 11 in the fiber orientation direction of the chopped fiber bundle) produced by the present invention is ± 5 °. If it is within the range, it may be a parallelogram shape.

  3 to 5, the blade is attached to only one roller, but the present invention may be attached to only one of a pair of rollers, Blades may be attached to both. If a blade is attached to only one of a pair of rollers, the other roller will only serve as a receiving part, and both have a blade attached to both of the two rollers. The roller will play both the role of the blade and the role of the receiving part.

  The chopped fiber bundle thus obtained has a section in which the number of fibers changes from the center portion of the chopped fiber bundle to the end portion in the fiber orientation direction. Therefore, fiber reinforced plastics molded using chopped fiber bundles are responsible for the largest chopped fiber bundle at the center of the chopped fiber bundle by continuously changing the number of chopped fiber bundles within the chopped fiber bundle. The load can be released little by little from the ends of the reinforcing fibers that continuously exist toward the end of the chopped fiber bundle, and stress concentration is unlikely to occur. Therefore, the strength is improved in a stepwise manner as compared with a configuration in which all the reinforcing fibers are cut at one place as in a conventional chopped fiber bundle. Not only that, stress concentration is difficult to occur, so initial damage is unlikely to occur, and cracks do not occur until just before failure. Among the applications of fiber reinforced plastics, there are some applications that cannot be applied because sound is generated due to initial damage and anxiety is caused, and fiber reinforced plastics can be applied to such applications. In addition, although initial damage greatly affects fatigue strength, in the present invention, since initial damage is small, not only static strength but also fatigue strength is greatly improved. Furthermore, not only the mechanical properties of the fiber reinforced plastic as described above, but also in the manufacturing process of the molding material for obtaining the fiber reinforced plastic, when the chopped fiber bundle is impregnated with the matrix resin, compared with the conventional one. Since the impregnating property is extremely good, an unexpected effect that the molding material can be reliably produced in a short time using a simple facility is obtained. From another viewpoint, the reliable impregnation of the matrix resin described above minimizes the generation of voids (unimpregnated portions) that cause a decrease in strength in the fiber-reinforced plastic obtained from the molding material as a result. It is possible to obtain stable mechanical characteristics with less variation. In this respect, it is clearly different from Japanese Patent Laid-Open No. 2003-165739 (Patent Document 2).

  In the present invention, the angle at which the fiber bundle is inserted needs to be 2 to 30 ° with respect to the blade in which the fiber orientation direction of the fiber bundle is attached to the roller. For example, a continuous fiber bundle is drawn out in one direction, and a preferred chopped fiber bundle is obtained by cutting the fiber length of the reinforcing fiber into an angle of 2 to 30 ° with respect to the fiber orientation direction so that the fiber length is in the range of 5 to 100 mm. be able to. The conventional chopped fiber bundle was cut and manufactured in a direction orthogonal to the fiber orientation direction, and it was cut at an angle of 2 to 30 ° with the fiber orientation direction. Furthermore, a chopped fiber bundle that can improve the impregnation property can be obtained. When the end of the chopped fiber bundle is at a smaller angle with respect to the fiber orientation direction, the fiber reinforced plastic is expected to increase the strength and facilitate impregnation when producing the molding material, particularly at 30 ° or less. Although the effect is remarkable, the handleability of the chopped fiber bundle itself is reduced, and in the cutting process, the smaller the angle between the fiber orientation direction and the blade to be cut, the less stable it is, so an angle of 2 ° or more is preferable. . More preferably, the end of the chopped fiber bundle has an angle of 3 to 25 ° with the fiber orientation direction, and preferably 5 to 20 ° in view of the balance between high strength as a fiber-reinforced plastic and processability.

  In the present invention, a blade is attached to at least one of the pair of rollers, but the blade needs to be arranged in a direction parallel to the rotation axis of the roller to which the blade is attached. In addition, as mentioned above, the rotation axis parallel direction referred to here indicates a direction in which an angle formed between the direction and the rotation axis is within ± 5 °. Although it is possible to incline the blade with respect to the rotation axis of the roller to which the blade is attached, the more the blade is inclined, the longer the fiber bundle is held by the blade and the receiving portion of the other roller. . Along with this, there is a problem that the insertion direction of the fiber bundle immediately after cutting is deviated from the insertion direction of the fiber bundle immediately before cutting. On the other hand, by arranging the blades in the direction parallel to the rotation axis of the roller to which the blades are attached, it is possible to shorten the time during which the fiber bundle is held by the blades and the receiving portions of the rollers as a pair. Thereby, the fluctuation | variation of the fiber insertion angle at the time of cutting becomes small, and it is possible to manufacture the chopped fiber bundle of the same shape stably. In addition, when the rotation axis of the roller to which the blade is attached and the blade are completely parallel, the number of fibers contacting the blade at the same time when cutting the fiber bundle increases, and the force pulling the fiber bundle is directly transmitted to the blade. The blade is likely to deteriorate. Considering the durability of the blade, it is more preferable to attach the blade at an angle of, for example, about 0.5 to 15 ° (absolute value) without attaching it in parallel.

  In the method according to the present invention, by setting the fiber lengths of the reinforcing fibers contained in the chopped fiber bundle obtained by cutting the fiber bundle to 100 mm or less, a molding material that is an aggregate of the chopped fiber bundles is obtained. A molding material having a complicated shape and excellent molding followability can be obtained. In the case of a molding material in which the fiber length of the reinforcing fiber is larger than 100 mm, it is difficult to flow in the fiber orientation direction, so it is difficult to form a complex shape unless it is shaped in advance along the design shape. When the fiber length is less than 5 mm, the fluidity is further improved, but high mechanical properties cannot be obtained even if other requirements are satisfied. Considering the relationship between fluidity and mechanical properties, it is more preferably in the range of 10 to 50 mm. In the method according to the present invention, the chopped fiber bundle obtained by cutting the fiber bundle should have fewer reinforcing fibers of less than 5 mm. Preferably, the number of fibers of less than 5 mm is included in the chopped fiber bundle. It should be less than 5% of the total number of fibers produced. That is, in the present invention, the fiber length of the reinforcing fibers contained in the fiber bundle is in the range of 5 to 100 mm means that the number of fibers having a fiber length of less than 5 mm is the total number of fibers contained in the chopped fiber bundle. It means 5% and all the fiber length is 100 mm or less.

  Furthermore, it is preferable that the fiber lengths of the reinforcing fibers included in the chopped fiber bundle are substantially the same. By making the lengths of the fibers contained in the chopped fiber bundles the same, the fiber bundles are integrated into a molding material to facilitate flow control when molding. As a means for realizing this, it is effective to keep the angle between the arrangement direction of the blades and the fiber orientation direction of the fiber bundle substantially constant. In the present invention, the fact that the fiber lengths are substantially the same means that 95% of the reinforcing fibers are included within a range of ± 5% from the average value of the fiber lengths of the reinforcing fibers included in the chopped fiber bundle. Point to. In addition, with respect to the angle formed by the blade and the fiber orientation direction of the fiber bundle, 95% of the reinforcing fibers are included within a range of ± 5% from the average value of the fiber lengths of the reinforcing fibers contained in the chopped fiber bundle. As long as possible, there may be a slight fluctuation range, and in this case, the angle formed by the blade and the fiber orientation direction of the fiber bundle may be considered to be substantially constant.

  As described above, a fiber bundle is temporarily gripped by a blade and a receiving portion that is paired with the blade during cutting, while the fiber bundle is held between a pair of rollers while the fiber bundle is not gripped. You only need to send it in. At this time, if the gap between the blade attached to the roller and the receiving roller is not sufficient, the movement of the fiber bundle is hindered by friction with the blade or the receiving roller, and the fiber bundle may be arranged at an appropriate position. Can not. On the other hand, if this gap is too wide, the fibers are likely to meander and cut errors frequently occur. Therefore, in the roller in which the blades are arranged and attached, when the maximum radius of the roller is R and the arrangement interval between adjacent blades on the roller is an angle Θ, the blade attached to the roller and the receiver The maximum value R (1-cos [Θ / 2]) of the gap (the length indicated by 22 in FIG. 12) with the roller is preferably 0.5 to 10 mm. More preferably, the maximum value R (1-cos [Θ / 2]) of the gap is 1 to 5 mm. In the present invention, the maximum radius R of the roller in which the blades are arranged and attached refers to the distance from the rotation axis of the roller to the blade edge of the blade attached to the roller.

  In the present invention, the mechanism for positioning the fiber bundle is preferably provided within 30 cm in the upstream direction from the cutting position where the fiber bundle and the blade attached to the roller contact. In the present invention, since the fiber bundle is inserted from the oblique direction with respect to the blade, the reinforcing fiber easily escapes from the blade when the fiber bundle is cut, and the insertion position of the fiber bundle is also easily changed. Therefore, in the present invention, it is possible to perform stable production by providing a mechanism for positioning the fiber bundle immediately before the cutting position where the fiber bundle and the blade attached to the roller are in contact with each other.

  Examples of the positioning mechanism include a roller guide, a comb guide, a cylindrical guide, and a nip roller. If a roller-shaped guide is used, the frictional force between the fiber bundle and the guide can be reduced, and the fiber bundle can always be fed to a fixed position. In addition, when the number of fiber bundles to be cut simultaneously is large and the roller guides cannot be arranged by the number of fiber bundles, it is convenient to use a comb-shaped guide. Furthermore, if a cylindrical guide such as a straw is used, it is less affected by slack in the fiber bundle, and the position where the fiber bundle is fed becomes more stable. The positioning of the positioning mechanism is more effective when it is closer to the cutting position, and it is better to bring the positioning mechanism closer to the shortest distance that can be physically arranged, but it should be positioned within 30 cm from the cutting position. In this case, the positioning effect can be sufficiently expected. More preferably, it is within 20 cm, more preferably within 15 cm. In the present invention, the front side (arrow 8 side in FIG. 3) is upstream from the contact portion between the blade and its receiving portion, and the back side (arrow 7 side in FIG. 3) is from the contact portion between the blade and its receiving portion. To the downstream.

  In the present invention, the distance from the cutting position at which the fiber bundle and the blade attached to the roller contact to the mechanism for positioning is determined by the contact portion between the fiber bundle and the blade attached to the roller, and the fiber bundle. Of the line segments connecting the contact portions with the mechanism, the length is calculated as the length of the line segment having the shortest length.

  In the manufacturing method of the chopped fiber in this invention, it is preferable to provide the drive mechanism which sends a fiber bundle within 50 cm from the cutting position where the fiber bundle and the blade attached to the roller contact. In the present invention, as described above, the fiber bundle is temporarily gripped by the blade and the receiving portion that is paired with the blade during cutting, while the fiber bundle is held between the pair of rollers while the fiber bundle is not gripped. It is necessary to feed a certain length. Several mechanisms for feeding the fiber bundle are conceivable, but in consideration of continuous productivity, a nip roller is preferable. In addition, as a place where the driving mechanism is arranged, in consideration of supplying the fiber bundle in a certain place and in a certain direction, the closer the cutting position, the greater the effect, and the shortest distance at which the driving mechanism can be physically arranged However, if the mechanism is arranged within 50 cm, preferably within 30 cm, a sufficient effect can be expected.

  In the present invention, the positioning mechanism and the driving mechanism described above exhibit their effects even when used alone, but more stable production can be performed by combining both mechanisms. Moreover, as a position which arrange | positions a drive mechanism, it is preferable to arrange | position upstream from the said positioning mechanism. In particular, the nip roller can be expected to have an effect of positioning the fiber bundle on itself.

  In the present invention, the distance from the cutting position where the fiber bundle and the blade are in contact to the drive mechanism that sends out the fiber bundle is the contact between the contact portion between the fiber bundle and the blade and the drive mechanism that sends out the fiber bundle and the fiber bundle. It is calculated as the length of the line segment whose length is the shortest among the line segments connecting to the part.

  In the present invention, the fiber bundle is cut while being in contact with each other while forming an acute angle (2 to 30 °) with the blade. For this reason, as described above, the fiber bundle is separated at the time of cutting, and the fibers easily escape from the blade and are difficult to stably cut as compared with the conventional method for producing chopped fibers. Therefore, as shown in FIG. 6, it is preferable that the friction material 17 is disposed only in the receiving portion where the blade 1 contacts the pair of rollers 3. By doing in this way, the escape of the fiber at the time of cutting can be prevented. In the present invention, the blade contacts the friction material. However, in order to prevent the rotation of the roller from being hindered, the friction material needs to be deformed to some extent as the blade contacts the friction material. However, if the deformation is too large, the blade pressure necessary for cutting the fiber bundle cannot be obtained. Therefore, as a candidate for the friction material, a material having an elastic modulus of about 10 MPa to 1000 MPa is preferable. For example, various rubbers such as styrene / butadiene rubber, natural rubber, nitrile rubber, and silicon rubber are effective. The reason why the friction material is disposed only in the receiving portion that is paired with the blade is that when the chopped fiber bundle is manufactured according to the present invention, the blade 1 and the pair of rollers 3 receive it while the fiber bundle 4 is sent out. It is required that the fiber bundle 4 is not gripped by the portion. In such a situation, if the friction material is arranged in the entire area of the roller 3, there is a possibility that the fiber bundle 4 and the friction material are strongly in contact with each other and the fiber bundle cannot be sent to an appropriate cutting position. Because there is.

  Further, as shown in FIG. 7, it is also effective to place the friction material only on the roller 2 to which the blade 1 is attached and at a portion adjacent to the blade as shown in FIG. 7. By doing in this way, escape of the fiber bundle at the time of cutting can be prevented.

  Examples of the reinforcing fibers of the present invention include organic fibers such as aramid fibers, polyethylene fibers, polyparaphenylene benzoxador (PBO) fibers, glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, tyrano fibers, basalt fibers, Examples thereof include inorganic fibers such as ceramic fibers, metal fibers such as stainless fibers and steel fibers, and other reinforcing fibers using boron fibers, natural fibers, modified natural fibers and the like as fibers. Among these, carbon fibers are particularly lightweight among these reinforcing fibers and have particularly excellent properties in specific strength and specific elastic modulus. Furthermore, since it is excellent in heat resistance and chemical resistance, it is suitable for a member such as an automobile panel for which weight reduction is desired.

  Furthermore, the number of filaments in a fiber bundle of carbon fibers used for general purposes is generally larger than that of other reinforcing fibers. Since carbon fiber is manufactured by applying heat treatment at a very high temperature over time, it is effective to increase the number of filaments contained in the fiber bundle if it is to be manufactured at low cost. For example, glass fiber is most frequently used as a chopped fiber bundle, and the number of filaments in the fiber bundle is generally 100 to 10,000. In comparison, the number of filaments in the fiber bundle of carbon fibers is generally 10,000 to 1,000,000, and the number of filaments in the fiber bundle is larger than that of the glass fiber. Here, the greater the number of filaments in the fiber bundle, the greater the stress concentration at the end of the chopped fiber bundle, and the lower the strength. In the present invention, stress concentration can be alleviated by making the shape of the chopped fiber bundle a parallelogram, so that the greater the number of filaments in the fiber bundle, the greater the strength improvement effect can be expected. In addition, since it can be easily impregnated even in a fiber bundle having a large number of filaments that is difficult to be impregnated with a matrix resin, it is possible to manufacture a molding material in a short time and reliably using simple equipment. Can be expected. In particular, the number of carbon fibers that can be expected to improve strength and impregnation is 15,000 to 500,000. Further, the number of reinforcing fibers that can be increased in strength and easily impregnated at low cost is preferably 20,000 to 200,000.

  Furthermore, the shape of the fiber bundle is preferably flat. When the fiber bundle is not flat and the number of reinforcing fibers contained in the fiber bundle is large, many reinforcing fibers are cut in a narrow region, so that the wear of the blade also becomes severe. Therefore, if the shape of the fiber bundle is made flat and the carbon fiber is cut in a wide range, the burden on the blade can be reduced and the wear of the blade can be suppressed. In addition, by making the shape of the fiber bundle flat, the thickness of the chopped fiber bundle is also reduced, so stress concentration at the short part of the fiber bundle can be alleviated, and high strength can be achieved when a fiber reinforced plastic is used. . The ratio (W / t) between the width W and the thickness t of the fiber bundle is preferably 10 to 1,000. If the ratio (W / t) is less than 10, the load applied to the blade increases, and the blade is likely to deteriorate. On the other hand, if it is larger than 1,000, the rigidity of the fiber bundle will decrease, and the fiber bundle will be bent or the fiber bundle will be cracked due to slight contact with the roller or blade. Becomes difficult. Furthermore, if it is going to produce a chopped fiber bundle stably, it is good that a ratio (W / t) is the range of 20-500. In the present invention, a flat carbon fiber may be used in advance, or the carbon fiber fiber bundle is preliminarily flattened using a guide roller, a nip roller, a minute vibration roller, or the like in a pre-process for cutting the fiber bundle. It may be opened.

  In the present invention, it is preferable to use a fiber bundle that is substantially untwisted. In the conventional technique, the shape of the chopped fiber bundle does not change greatly even if the fiber bundle includes a twist. However, in the present invention, since the blade is applied obliquely with respect to the traveling direction of the fiber bundle, when the fiber bundle is twisted, the shape of the obtained chopped fiber bundle tends to be distorted. In the fiber reinforced plastic, if the chopped fiber bundle having such an irregular shape is slightly included, the mechanical properties are not affected so much, but if the contained amount increases, the physical properties may be decreased. In order to make the shape of the obtained chopped fiber bundle uniform and to stabilize the mechanical properties in the case of a fiber reinforced plastic, it is preferable that the fiber bundle is substantially untwisted. In the present invention, “substantially no twist” means that the number of twists per 1 m is less than 2.

  Furthermore, the sizing agent is adhered to the reinforcing fiber, and the sizing agent may be in the range of 0.1 to 10% by mass based on the mass of the entire chopped fiber bundle. When cutting a continuous fiber bundle, in order to cut the reinforcing fiber into a predetermined shape without being separated, the reinforcing fibers are in close contact with each other and have a certain amount of binding force, and are integrated as a fiber bundle. It is important that Then, the manufacturing process property of a chopped fiber bundle improves dramatically by making 0.1-10 mass% sizing agent of a chopped fiber bundle adhere to a reinforced fiber. Moreover, the handleability at the time of manufacturing a molding material by integrating a chopped fiber bundle can also be improved. For example, by applying a sizing agent dissolved or dispersed in a solvent to the drawn fiber bundle within a range of 0.1 to 10% by mass, cutting the continuous fiber bundle, and then heating to dry the solvent. The chopped fiber bundle of the present invention can be obtained. As the sizing agent, for example, an epoxy resin, a phenol resin, an unsaturated polyester resin, a vinyl ester resin, a polyamide resin, a urethane resin, or a mixed resin thereof can be used, and these are diluted with water or a solvent to reinforce the fiber. It can be dried by being brought into contact with and attached.

  Furthermore, the matrix resin which comprises a matrix in fiber reinforced plastics is good to have adhered to the reinforced fiber. The amount of the matrix resin attached is preferably in the range of 20 to 75% by mass based on the mass of the entire chopped fiber bundle. If the reinforcing fibers are impregnated in advance with the reinforcing fibers, the chopped fiber bundles can be stably manufactured in a predetermined shape without the reinforcing fibers being separated at the time of cutting. Moreover, the handleability at the time of manufacturing a molding material by integrating a chopped fiber bundle can also be improved.

  In producing a fiber reinforced plastic using such a chopped fiber bundle, in order to improve the handleability and to produce a molding material suitable for pressure molding such as press molding and vacuum molding, the chopped fiber of the present invention as shown in FIG. It is preferable to integrate the bundle assembly into a molding material. For example, after the chopped fiber bundle of the present invention is spread on a sheet-like matrix resin, it is sandwiched by another sheet-like matrix resin, and the chopped fiber bundle and the matrix resin are integrated, so as to be called SMC or stampable sheet Good molding material. Further, the chopped fiber bundles may be dispersed and integrated in a sheet form. At this time, if the chopped fiber bundle is impregnated with the matrix resin in advance as described above, it can be integrated without being impregnated with the resin again. On the other hand, even if the chopped fiber bundle is not impregnated with the matrix resin, RTM (resin transfer molding) molding in which the resin is injected into the molding material made of the aggregate of the chopped fiber bundle may be performed to obtain the fiber reinforced plastic.

  The method for producing a molding material of the present invention comprises: (a) spreading a large number of chopped fiber bundles obtained by the production method of the present invention on the molding substrate so that the plurality of chopped fiber bundles are deposited in one or more layers. A chopped fiber bundle spraying step, and (b) a chopped fiber bundle in which a large number of chopped fiber bundles dispersed on the molding substrate are integrated together to form a molding material composed of a chopped fiber bundle aggregate. It is preferable to consist of an aggregate formation process. Here, the molding substrate refers to a substrate for forming a molding material on which the chopped fiber bundles to be dispersed are deposited. For example, when used for the production of a molding material containing a matrix resin used when producing a fiber reinforced plastic, the matrix resin is formed on the surface of a support such as a resin sheet, a resin film, or a release film formed of the matrix resin. Examples thereof include a resin film with a support coated with bismuth. In addition, when used in the production of a molding material that does not contain a matrix resin, a shaping mold (screen) for forming a preform that is not yet impregnated with a matrix resin having a three-dimensional shape can be given as an example. .

  In the method for producing a molding material of the present invention, in the chopped fiber bundle spreading step of (a), the molding base has a flat surface, and an array of reinforcing fibers of each of the multiple chopped fiber bundles on the flat surface. The chopped fiber bundles are spread on the flat surface so that the directions are the same, and the chopped fiber bundle sheet composed of the multiple chopped fiber bundles is formed on the flat surface. In the bundle assembly forming step, it is more preferable that a molding material composed of the chopped fiber bundle sheet formed of the plurality of chopped fiber bundles is formed.

  The arrangement direction of the reinforcing fibers of the multiple chopped fiber bundles on the flat surface may be substantially the same. Here, the arrangement direction of the reinforcing fibers in each chopped fiber bundle is substantially the same, and the average value in the arrangement direction of each reinforcing fiber included in the chopped fiber bundle is a representative of the reinforcing fibers representing the chopped fiber bundle. As the arrangement direction, the chopped fiber bundle in which the representative arrangement direction of each chopped fiber bundle in the chopped fiber bundle aggregate is within ± 10% is 90% or more of the total chopped fiber bundle in the chopped fiber bundle aggregate. .

  In the method for producing a molding material of the present invention, after the chopped fiber bundle sheet is formed, the arrangement directions of the reinforcing fibers of the multiple chopped fiber bundles on the formed chopped fiber bundle sheet are the same. In addition, the chopped fiber bundle sheet is further different from the arrangement direction of the reinforcing fibers of the chopped fiber bundle, and the chopped fiber bundle sheet is further formed of the chopped fiber bundle sheet. More preferably, the chopped fiber bundle is dispersed on the formed chopped fiber bundle sheet so that a fiber bundle sheet is formed, and a molding material composed of a laminate of the chopped fiber bundle sheets is formed. The array direction of the reinforcing fibers of the multiple chopped fiber bundles on the formed chopped fiber bundle sheet may be substantially the same. Here, the arrangement direction of the reinforcing fibers in each chopped fiber bundle is substantially the same, and the average value in the arrangement direction of each reinforcing fiber included in the chopped fiber bundle is a representative of the reinforcing fibers representing the chopped fiber bundle. As the arrangement direction, the chopped fiber bundle in which the representative arrangement direction of each chopped fiber bundle in the chopped fiber bundle aggregate is within ± 10% is 90% or more of the total chopped fiber bundle in the chopped fiber bundle aggregate. .

  Further, in the method for producing a molding material of the present invention, the chopped fiber bundles are dispersed on the molding base so that the arrangement directions of the reinforcing fibers of the many chopped fiber bundles on the molding base are random. May be.

  Furthermore, in the method for producing a molding material according to the present invention, the molding substrate is a resin with a support in which the surface of the support such as a resin sheet, a resin film, or a release film formed of a matrix resin is coated with the matrix resin. A film is preferred.

  In the method for producing a molding material of the present invention, the chopped fiber bundle spreading step (a) includes: (a) the molding base has a three-dimensional shape surface, and the plurality of chopped fiber bundles on the three-dimensional shape surface. A first chopped fiber bundle layer composed of a large number of chopped fiber bundles is formed by spreading the chopped fiber bundles on the three-dimensional shape surface so that the arrangement directions of the respective reinforcing fibers are the same. A layer forming step, and (b) an arrangement direction of the reinforcing fibers of the multiple chopped fiber bundles on the first chopped fiber bundle layer formed in the first layer forming step is the same. And in the first chopped fiber bundle layer, the first chopped fiber bundle layer has a reinforced fiber arrangement direction different from the reinforced fiber arrangement direction of the chopped fiber bundle. The chopped fiber bundle may be made from the second layer forming step of forming a second chopped fiber bundle layer comprising a large number of chopped fiber bundle was sprayed in.

  The arrangement direction of the reinforcing fibers of the multiple chopped fiber bundles may be substantially the same. Here, the arrangement direction of the reinforcing fibers in each chopped fiber bundle is substantially the same, and the average value in the arrangement direction of each reinforcing fiber included in the chopped fiber bundle is a representative of the reinforcing fibers representing the chopped fiber bundle. As the arrangement direction, the chopped fiber bundle in which the representative arrangement direction of each chopped fiber bundle in the chopped fiber bundle aggregate is within ± 10% is 90% or more of the total chopped fiber bundle in the chopped fiber bundle aggregate. .

  In another aspect of the method for producing a molding material of the present invention, (a) the first chopped fiber bundle of the present invention is formed by a matrix resin used in producing a resin molded body containing reinforcing fibers. A chopped fiber bundle spraying step for spraying on a molded substrate made of a resin sheet, (b) the multiple chopped fiber bundles of the first resin sheet having the multiple chopped fiber bundles obtained in the chopped fiber bundle spraying step A resin sheet laminating step of laminating the second resin sheet made of the matrix resin, and (c) the plurality of chopped fiber bundles obtained in the resin sheet laminating step and the first and second By pressing and / or heating a laminate composed of a resin sheet, the multiple chopped fiber bundles and the first and second resin sheets Integrated, and a chopped fiber bundle aggregate forming step of forming a chopped fiber bundle aggregate.

  Still another aspect of the method for producing a molding material of the present invention is a kneading step in which a large number of chopped fiber bundles of the present invention and a thermoplastic resin are kneaded, and a kneaded product of the chopped fiber bundle and the thermoplastic resin is prepared, The kneaded material prepared in the kneading step is continuously extruded into a rod-like or sheet-like shape, and a molding step for forming a rod-like or sheet-like continuous molded product, and a continuous molded product obtained by the molding step, in its longitudinal direction And a pelletizing step of forming pellets for injection molding.

  Examples of the fiber reinforced plastic matrix resin used in the present invention include, for example, epoxy resins, unsaturated polyester resins, vinyl ester resins, phenol resins, epoxy acrylate resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, maleimide resins, Thermosetting resins such as cyanate resin, polyamide, polyacetal, polyacrylate, polysulfone, ABS, polyester, acrylic, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene, polypropylene, polyphenylene sulfide (PPS), Fluorine resins such as polyetheretherketone (PEEK), liquid crystal polymer, vinyl chloride, polytetrafluoroethylene, and thermoplastic resins such as silicone. It is. Among these, thermosetting resins generally have a high elastic modulus and excellent shape stability because they have a crosslinked structure. Even when a fiber reinforced plastic is used, a high elastic modulus can be exhibited, and a highly reliable fiber reinforced plastic can be obtained from the viewpoint of dimensional stability. Since the viscosity of the resin can be adjusted to a low viscosity, the resin can be easily impregnated into the chopped fiber bundle, so that the matrix resin can be applied in any process of manufacturing the fiber reinforced plastic. In addition, since it can be designed to have tackiness at room temperature, it is excellent in handleability such as being integrated by simply pressing when molding materials are laminated.

More preferably, among the thermosetting resins, an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a phenol resin, an acrylic resin, or a mixed resin thereof is preferable. The resin viscosity at normal temperature (25 ° C.) of these resins is preferably 1 × 10 ⁶ Pa · s or less, and if within this range, a molding material having tackiness and draping properties satisfying the present invention is obtained. be able to.

  Moreover, since the thermoplastic resin mentioned as another preferable matrix resin generally has high toughness, it can suppress the connection of the cracks which are the weak points of a short fiber reinforced plastic, and an intensity | strength improves. In particular, in applications in which impact characteristics are regarded as important, it is preferable to use a thermoplastic resin as the matrix resin.

  Moreover, it can be set as a fiber reinforced plastic by solidifying the molding material (meaning hardening when the matrix resin is a thermosetting resin). Only after the resin is solidified, can it be used as various parts, exhibiting high mechanical strength. Examples of the method for solidifying the resin, that is, the method for molding the fiber reinforced plastic include press molding, autoclave molding, RTM molding and the like. Of these, press molding is preferable in consideration of production efficiency. The chopped fiber bundle of the present invention and the fiber reinforced plastic using the same are used for bicycle parts, automobile parts such as doors and seat frames, and machine parts such as robot arms that require strength, rigidity, and lightness. There is. In particular, the present invention can be preferably applied to automobile parts such as seat panels and seat frames that require molding followability of complicated shapes in addition to strength and light weight.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the inventions described in the examples.

<Mechanical property evaluation method>
A tensile strength test piece having a length of 250 ± 1 mm and a width of 25 ± 0.2 mm was cut out from a flat fiber-reinforced plastic obtained by the method described in each example. According to the test method specified in JIS K-7073 (1998), the tensile strength and the tensile modulus were measured at a crosshead speed of 2.0 mm / min with a distance between the gauge points of 150 mm. In this example, an Instron (registered trademark) universal testing machine 4208 type was used as a testing machine. The number of test specimens measured was n = 5, and the average values were tensile strength and tensile modulus.

Example 1
An SMC sheet was prepared using the method for producing a chopped fiber bundle of the present invention and molded to obtain flat plate properties.

  A continuous fiber bundle of substantially untwisted unsized carbon fibers (reinforced fiber single yarn diameter 7 μm, 12,000 filaments, tensile strength 5.0 GPa, tensile modulus 240 GPa), resin component 2.0% by weight Reactive urethane resin emulsion (Daiichi Kogyo Seiyaku Co., Ltd., Superflex-R5000) is continuously immersed in a sizing agent mother liquor diluted with purified water to give a sizing agent to the carbon fiber and dried. Under a tension of 600 g / dtex, moisture was removed by drying with a 150 ° C. hot roller and a 200 ° C. drying furnace. The sizing agent adhesion amount was 1.2% by weight based on the mass of the entire chopped fiber bundle. Further, when the width W and the thickness t of the fiber bundle are measured 10 times for each 1 m with a micrometer, and the ratio (W / t) between the width W and the thickness t of the fiber bundle is obtained from the average value, The ratio was 120. Furthermore, the operation of dividing the fiber bundle into 1 m pieces and counting the number of twists was repeated 10 times, and the average value was taken as the number of twists, and the number of twists was 0.8 times / m.

  The continuous fiber bundle was cut using a cutting device to obtain a chopped fiber bundle. As the roller, two iron rollers having a diameter of 10 cm were used, and a blade was attached to one of the rollers in parallel with the rotation axis at intervals of 5 mm in the circumferential direction. At this time, the protrusion amount of the blade from the roller surface was 1.7 mm, and the maximum value R (1-cos [Θ / 2]) between the blade attached to the roller and the receiving roller was 0.06 mm. It was. The other roller was provided with a rubber friction material having a thickness of 3 mm so as to cover the periphery of the roller.

  A guide was attached as a mechanism for positioning 5 cm before the cutting position where the fiber bundle and the blade attached to the roller contacted, and a nip roller was attached as a drive mechanism 20 cm before that. While rotating this pair of rollers, the above-mentioned fiber bundle was inserted between the rollers at an angle of 12 ° to form a blade, thereby producing a chopped fiber bundle. In rare cases, the fiber bundle may be cut without reaching a predetermined position during cutting, and a chopped fiber bundle having a slightly desired shape may be produced, but the yarn path of the fiber bundle is stable. The fiber bundle was cut at approximately the same angle.

  In the chopped fiber bundle thus obtained, the end of the chopped fiber bundle has a linear shape at an angle of 12 ° with the fiber orientation direction of the chopped fiber bundle, and the fiber length of the reinforcing fiber is the same in the chopped fiber bundle. However, there was a variation of about 3%, but it was 25 mm. The chopped fiber bundles produced were all parallelograms and had almost the same shape. Moreover, although a chopped fiber bundle of about 5 kg was cut, there was no uncut portion, and it was possible to produce a chopped fiber bundle stably.

On the other hand, 100 parts by weight of vinyl ester resin (manufactured by Dow Chemical Co., Ltd., Delaken 790) as the matrix resin, 1 part by weight of tert-butyl peroxybenzoate (Nippon Yushi Co., Ltd., Perbutyl Z) as the curing agent, 2 parts by weight of zinc stearate (manufactured by Sakai Chemical Industry Co., Ltd., SZ-2000) is used as an internal mold release agent, and 4 parts by weight of magnesium oxide (Kyowa Chemical Industry Co., Ltd., MgO # 40) is used as a thickener. Then, they were sufficiently mixed and stirred to obtain a resin paste. The resin paste was applied onto a polypropylene release film using a doctor blade. From above, the chopped fiber bundle was dropped and dispersed uniformly so that the weight per unit area was 500 g / m ² . Further, it was sandwiched between the other polypropylene film coated with the resin paste with the resin paste side inward. The volume content of carbon fiber with respect to the SMC sheet was 40%. The obtained sheet was allowed to stand at 40 ° C. for 24 hours to sufficiently thicken the resin paste, and an SMC sheet as a molding material as shown in FIG. 9 was obtained. At this time, when the chopped fiber bundle was impregnated with the matrix resin paste, it could be impregnated more easily and in about half the time than that of Comparative Example 1, and good impregnation properties were exhibited.

  This SMC sheet was cut into 250 × 250 mm, and after four layers were stacked, the SMC sheet was placed at the approximate center on a flat plate mold having a 300 × 300 mm cavity (corresponding to a charge rate of 70%), and then a heating press molding machine Was cured under conditions of 150 ° C. × 5 minutes under a pressure of 6 MPa to obtain a plate-like fiber-reinforced plastic of 300 × 300 mm.

  The mold cavity was filled with fiber reinforced plastic, and the flowability of the molding material was good. Only when the fiber reinforced plastic was placed on a flat test table, the molded body was in contact with the entire surface of the test table, and it was judged that there was no warpage. The thickness of the fiber reinforced plastic was 2.8 mm.

  According to the result of the tensile test, the tensile modulus was very high as 33 GPa, and the tensile strength was as high as 330 MPa. Even compared with Comparative Example 1, the mechanical properties were 35% or more in terms of elastic modulus and twice or more in strength. Further, when the obtained fiber reinforced plastic is cut out and the cut surface is observed, the chopped fiber bundle becomes thinner as it goes from the center to the end as shown in FIG. 10, and in particular, the chopped fiber bundle that runs parallel to the cut surface is also included. As the distance from the center decreases toward the end, it can be seen that the number of fibers is decreasing and the load transmission efficiency is improved, so that not only the tensile strength but also the elastic modulus is improved. It was speculated.

(Example 2)
When a continuous fiber bundle similar to Example 1 is cut to obtain a chopped fiber bundle, the distance between the blades attached to the rollers is set to 12.5 mm in the circumferential direction, and the fibers are continuous at an angle of 30 ° with respect to the blade. A bundle was inserted. During cutting, the yarn path of the fiber bundle was stable and the fiber bundle was cut at approximately the same angle. In the chopped fiber bundle thus obtained, the end of the chopped fiber bundle has a linear form at an angle of 30 ° with the fiber orientation direction of the chopped fiber bundle, and the fiber length of the reinforcing fiber is the same in the chopped fiber bundle. However, although there was a variation of about 2%, it was 25 mm. The chopped fiber bundles produced were all parallelograms and had almost the same shape.

  An SMC sheet was prepared and molded using the chopped fiber bundle thus obtained as a molding material in the same manner as in Example 1. The mold cavity was filled with fiber reinforced plastic, and the flowability of the molding material was good. Only when the fiber reinforced plastic was placed on a flat test table, the molded body was in contact with the entire surface of the test table, and it was judged that there was no warpage. The thickness of the fiber reinforced plastic was 2.8 mm.

  Next, a tensile test was carried out in the same manner as in Example 1. The tensile modulus was as high as 29 GPa, and the tensile strength was as high as 250 MPa. Even when compared with Comparative Example 1, the mechanical properties were higher by about 20% in elastic modulus and about 70% in strength. Further, when the obtained fiber reinforced plastic is cut out and the cut surface is observed, the chopped fiber bundle becomes thinner from the center to the end as shown in FIG. 7, and the chopped fiber bundle running in parallel with the cut surface is also particularly As the distance from the center decreases toward the end, it can be seen that the number of fibers is decreasing and the load transmission efficiency is improved, so that not only the tensile strength but also the elastic modulus is improved. It was speculated.

(Example 3)
A chopped fiber was produced by the same apparatus as in Example 1 except that a guide was provided as a positioning mechanism, and the distance from the cutting position where the fiber bundle and the blade attached to the roller contacted to the guide was 30 cm. During cutting, the yarn path of the fiber bundle was stable and the fiber bundle was cut at approximately the same angle. When the finished chopped fiber bundle was observed, its shape was slightly uneven, but the fiber length of a chopped fiber bundle was about 20% variation even within the same chopped fiber bundle, and could be applied well as a molding material Met.

Example 4
Chopped fibers were produced by the same apparatus as in Example 1 except that the distance from the contact portion between the blade and the receiving roller to the guide was 50 cm. During cutting, the fiber bundle moved in a direction avoiding the blades, and on the other hand, the fiber bundle insertion position varied slightly as it returned to its original insertion position due to the elasticity of the reinforcing fibers themselves. When the finished chopped fiber bundle was observed, its shape was slightly uneven, but the fiber length of a certain chopped fiber bundle had a variation of about 50% within the same chopped fiber bundle, but the fiber orientation of the fiber bundle It was cut at an angle of 30 ° or less with respect to the direction, and was applicable well as a molding material.

(Example 5)
An SMC sheet was prepared and molded in the same manner as in Example 1 except that the number of filaments in the fiber bundle was 24,000, and flat plate properties were obtained. At this time, when the ratio (W / t) between the width W and the thickness t of the fiber bundle was obtained as in Example 1, the ratio was 300.

  The obtained fiber reinforced plastic had no warpage and good surface quality. Moreover, according to the result of the tensile test, the tensile modulus is very high as 30 GPa, and the tensile strength is as high as 270 MPa, which is 2.5 times higher than that in Comparative Example 4. It was. This strength improvement rate was larger than the case where the number of filaments was 12,000 (Example 1, Comparative Example 1), and it was confirmed that the greater the number of filaments, the greater the effect of the present invention.

(Example 6)
A chopped fiber bundle was produced in the same manner as in Example 2, except that a fiber bundle having a ratio (W / t) of the width W to the thickness t of the fiber bundle was 7.

  Since about 3 kg of chopped fiber bundles were cut, some fibers were not cut and some chopped fiber bundles were connected to each other. Moreover, when the surface of the blade after cutting was observed, a portion where the blade edge was missing was confirmed. Although the present invention can be carried out even if the ratio (W / t) between the width W and the thickness t of the fiber bundle is small, in view of the durability of the blade, the fiber bundle with a slightly larger ratio (W / t). It was considered better to cut. Regarding the mechanical properties, the tensile elastic modulus was 28 GPa and the tensile strength was 220 MPa, which was far superior to Comparative Example 1, but was slightly inferior to Example 2. Although the effect of the present invention can be confirmed even when the ratio (W / t) between the width W and the thickness t of the fiber bundle is small, the concentration of stress at the end of the fiber bundle is greater when a fiber bundle having a larger ratio is used. It was thought that the strength could be reduced and the strength would be higher.

(Example 7)
A chopped fiber bundle was produced in the same manner as in Example 1 except that the blade spacing was 16.2 mm. At this time, the maximum value R (1-cos [Θ / 2]) of the gap between the blade attached to the roller and the receiving roller was 0.63 mm.

  During cutting, the yarn path of the fiber bundle was stable and the fiber bundle was cut at approximately the same angle. In the obtained chopped fiber bundle, the end of the chopped fiber bundle has a linear form at an angle of 12 ° with the fiber orientation direction of the chopped fiber bundle, and the fiber length of the reinforcing fiber is within the same chopped fiber bundle. Although there was a variation of about 2%, it was 25 mm. The chopped fiber bundles produced were all parallelograms and had almost the same shape. In Example 1, the fiber bundle was rarely cut without reaching a predetermined position. However, in this example, such a phenomenon was not confirmed. By setting the maximum value R (1-cos [Θ / 2]) of the gap to 0.5 mm or more, the influence of the friction generated between the blade and the fiber bundle is reduced, so that the fiber bundle is more stable. It was thought that was able to cut.

(Comparative Example 1)
The mechanical properties of SMC using a chopped fiber bundle cut in the 90 ° direction, which is a conventional technique, are obtained and used as a comparative example.

  The fiber bundle to be used is the same as in Example 1, and the apparatus used for cutting is the same as the apparatus described in Example 1 except that the interval between the blades attached to the rollers is 25 mm in the circumferential direction. A continuous fiber bundle was inserted at an angle of 90 °. The chopped fiber bundle thus obtained had a fiber length of the reinforcing fiber of 25 mm, and the end of the chopped fiber bundle had a linear form at an angle of 90 ° with the fiber orientation direction of the chopped fiber bundle.

  An SMC sheet was prepared and molded in the same manner as in Example 1.

  The mold cavity was filled with fiber reinforced plastic, and the flowability of the molding material was good. There was no warp and the thickness of the fiber reinforced plastic was 2.8 mm.

  According to the results of the tensile test, the tensile modulus was 24 GPa and the tensile strength was 150 MPa. Further, when the obtained fiber reinforced plastic is cut out and the cut surface is observed, the chopped fiber bundle running in parallel with the cut surface as shown in FIG. 11 is cut at the end portion 11 perpendicular to the thickness direction. The resin reservoir 21 was generated at the tip of 11. Some of the resin reservoirs 21 had voids.

(Comparative Example 2)
The mechanical characteristics of SMC using a chopped fiber bundle having a fiber length longer than that of Comparative Example 1 and having a cut length L = 50 mm equivalent to that of Example 1 is obtained as a comparative example.

  Using a continuous fiber bundle similar to that of Example 1, the interval between the blades attached to the rollers is set to 50 mm in the circumferential direction, and the blades are provided at intervals of 50 mm in the circumferential direction of the rotary cutter. A continuous fiber bundle was inserted. The chopped fiber bundle thus obtained had a fiber length of the reinforcing fiber of 50 mm, and the end of the chopped fiber bundle had a linear form at an angle of 90 ° with the fiber orientation direction of the chopped fiber bundle.

  An SMC sheet was prepared and molded in the same manner as in Example 1.

  The mold cavity was filled with fiber reinforced plastic, and the flowability of the molding material was good. There was no warp and the thickness of the fiber reinforced plastic was 2.8 mm. Further, according to the results of the tensile test, the tensile elastic modulus was 26 GPa and the tensile strength was 160 MPa, which were substantially the same mechanical properties as those of Comparative Example 1. It has been found that conventional SMC hardly contributes to the improvement of mechanical properties even if the fiber length is increased.

(Comparative Example 3)
The mechanical properties of SMC using chopped fiber bundles cut in the 45 ° direction are obtained and used as a comparative example.

  The same continuous fiber bundle as in Example 1 was used, and it was cut into a straight line at a 45 ° angle with respect to the fiber with scissors. Using this chopped fiber bundle, an SMC sheet was prepared and molded in the same manner as in Example 1.

  The mold cavity was filled with fiber reinforced plastic, and the flowability of the molding material was good. There was no warp and the thickness of the fiber reinforced plastic was 2.8 mm. Moreover, according to the result of the tensile test, the tensile elastic modulus was 25 GPa and the tensile strength was 200 MPa. Compared with Comparative Example 1, although the strength is high, no significant improvement is observed. Further, almost no improvement was observed in the elastic modulus.

(Comparative Example 4)
An SMC sheet was prepared and molded in the same manner as in Comparative Example 1 except that the number of filaments of the carbon fiber bundle was 24,000, and flat plate properties were obtained.

  According to the results of the tensile test, the tensile modulus was 22 GPa and the tensile strength was 110 MPa, which was lower than that of Comparative Example 1. As the number of filaments increased, the stress concentration at the end of the fiber bundle became intense and the strength was thought to have decreased.

It is a perspective view which shows an example of the manufacturing method of the conventional chopped fiber bundle. It is a top view which shows an example of the conventional chopped fiber bundle. It is a perspective view which shows an example of the manufacturing method of the chopped fiber bundle of this invention. It is a top view which shows an example of the manufacturing process of the chopped fiber bundle of this invention. It is a perspective view which shows an example of the manufacture process of the chopped fiber bundle of this invention. It is a top view which shows an example of the roller of this invention. It is a top view which shows an example of the roller of this invention. It is a top view which shows an example of the chopped fiber bundle of this invention. It is a top view which shows an example of the SMC sheet using the chopped fiber bundle of this invention. It is sectional drawing which shows an example of the fiber reinforced plastics of this invention. It is sectional drawing which shows an example of the conventional fiber reinforced plastic. It is a top view which shows an example of the manufacturing process of the chopped fiber bundle of this invention.

Explanation of symbols

1: Blade 2: Roller with blade attached 3: Roller to be paired with roller 2 with blade attached
4: Fiber bundle
5: Conventional chopped fiber bundle 6: Edge direction of blade edge of blade 1 7: Downstream direction 8: Upstream direction 9: Fiber orientation direction 10: Reinforcing fiber 11: Aggregation of end portions of reinforcing fiber 12: Chopped fiber of the present invention Bundle 13: Angle formed by the edge line direction of the blade edge of the blade in contact with the fiber bundle and the fiber orientation direction of the fiber bundle 14: Travel direction of the fiber bundle 15: The blade edge of the blade in contact with the roller 3 is transferred to the roller 3 Projected line 16: Projected line of the blade tip of the blade not contacting the roller 3 onto the roller 3 17: Friction material 18: Cutting length 19: Angle formed by the orthogonal direction of the fiber and the end of the chopped fiber bundle 20: Cut-out cross section of chopped fiber bundle 21: Resin pool 22: Gap

Claims (20)

A method for producing a chopped fiber bundle, which is obtained by cutting a fiber bundle in which reinforcing fibers are substantially aligned in one direction to obtain a chopped fiber bundle, wherein at least one of the rollers is parallel to the rotation axis of the roller. And a blade attached to the roller by continuously supplying the fiber bundle between a pair of rollers, which are rollers mounted by arranging the blades at equal intervals in the circumferential direction of the roller, and the roller When the fiber bundle is cut by bringing the receiving part of the other roller into contact with each other, the angle between the blade attached to the roller and the fiber orientation direction of the fiber bundle is in the range of 2 to 30 °. The chopped fiber bundle is cut by bringing the fiber bundle into contact with a blade attached to the roller, and cutting the fiber bundle so that the fiber length of the reinforcing fibers constituting the fiber bundle is 5 to 100 mm. Manufacturing method. 2. The chopped fiber according to claim 1, wherein a fiber length of the reinforcing fiber is made substantially constant by making an angle formed by a blade attached to the roller and a fiber orientation direction of the fiber bundle substantially constant. A method of manufacturing a bundle. In the roller in which the blades are arranged and mounted, when the maximum radius of the roller is R, and the arrangement interval between adjacent blades on the roller is an angle Θ, the blade attached to the roller and the receiving roller The method for producing a chopped fiber bundle according to claim 1 or 2, wherein a maximum value R (1-cos [Θ / 2]) of the gap is 0.5 to 10 mm. The manufacturing method of the chopped fiber in any one of Claims 1-3 in which the said fiber bundle consists of 10,000-1,000,000 carbon fibers. The manufacturing method of the chopped fiber bundle of Claims 1-4 whose ratio (W / t) of the width W of the said fiber bundle and thickness t exists in the range of 10-1,000. The method for producing a chopped fiber bundle according to claim 1, wherein the fiber bundle is substantially untwisted. The chopped fiber bundle according to claim 1, wherein a sizing agent is attached to the reinforcing fibers, and the sizing agent is in a range of 0.1 to 10% by mass based on the mass of the entire chopped fiber bundle. Manufacturing method. The chopped fiber according to any one of claims 1 to 7, further comprising a mechanism for positioning the fiber bundle within 30 cm in an upstream direction from a cutting position where the fiber bundle and a blade attached to the roller are in contact with each other. Production method. The chopped fiber production according to any one of claims 1 to 8, further comprising a drive mechanism for feeding the fiber bundle within 50 cm in an upstream direction from a cutting position where the fiber bundle and a blade attached to the roller are in contact with each other. Method. The chopped fiber manufacturing method according to claim 9, wherein the driving mechanism is a nip roller. The manufacturing method of the chopped fiber bundle in any one of Claims 1-10 with which the friction material was arrange | positioned only at the receiving part of the said roller. The chopped fiber bundle according to any one of claims 1 to 11, wherein the friction material is disposed only on a portion where the blade attached to the roller is disposed and adjacent to the blade attached to the roller. Manufacturing method. A chopped fiber bundle spraying step of spraying the chopped fiber bundle obtained by the production method according to any one of claims 1 to 12 so that the plurality of chopped fiber bundles are deposited in a single layer or a plurality of layers on a molded substrate. And a chopped fiber bundle assembly forming step in which a large number of chopped fiber bundles dispersed on the molding substrate are integrated together to form a molding material composed of a chopped fiber bundle assembly. Material manufacturing method. In the chopped fiber bundle spreading step, the molding base has a flat surface, and the arrangement direction of the reinforcing fibers of the multiple chopped fiber bundles on the flat surface is the same, and on the flat surface The chopped fiber bundles are dispersed on the flat surface so that a chopped fiber bundle sheet composed of the multiple chopped fiber bundles is formed, and in the chopped fiber bundle assembly forming step, The manufacturing method of the molding material of Claim 13 in which the molding material which consists of a chopped fiber bundle sheet formed in this way is formed. After the chopped fiber bundle sheet is formed, the chopped fibers are formed such that the arrangement directions of the reinforcing fibers of the multiple chopped fiber bundles on the formed chopped fiber bundle sheet are the same. Different from the arrangement direction of the reinforcing fibers of the chopped fiber bundle in the bundle sheet, and further, another chopped fiber bundle sheet composed of the multiple chopped fiber bundles is formed on the formed chopped fiber bundle sheet. The manufacturing method of the molding material of Claim 13 with which the said chopped fiber bundle is spread | dispersed on the formed chopped fiber bundle sheet | seat, and the molding material which consists of a laminated body of a chopped fiber bundle sheet | seat is formed. The manufacturing of the molding material according to claim 13, wherein the chopped fiber bundles are dispersed on the molding substrate such that the arrangement directions of the reinforcing fibers of the plurality of chopped fiber bundles on the molding substrate are random. Method. The method for producing a molding material according to any one of claims 13 to 15, wherein the molding substrate is a resin sheet formed of a matrix resin used when a resin molding including reinforcing fibers is produced. A molding material integrated using at least the chopped fiber bundle produced by the method according to claim 1. The molding material according to claim 18, comprising a matrix resin made of a thermosetting resin. 20. A fiber-reinforced plastic molded using at least the molding material according to claim 18 or 19.

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