JP5569708B2 - Manufacturing method of sheet molding compound - Google Patents

Description

  The present invention relates to a method for manufacturing a sheet molding compound.

  When a sheet molding compound (hereinafter referred to as SMC) is heated and pressurized in a mold, the reinforcing fibers and the resin composition flow together to fill the cavity, so that the thickness is partially different. It is an intermediate material advantageous for obtaining molded products of various shapes such as those having ribs and bosses.

  On the other hand, the reinforcing fibers in SMC have a drawback that the mechanical strength cannot be increased because the fiber length is short and the orientation is random. Further, the mechanical strength has a drawback that the unevenness is large depending on the place.

  Non-Patent Document 1 shows that the strength and elastic modulus of the SMC molded product decrease as the number of filaments of the carbon fiber strand increases.

  Thus, studies have been made to use a thick strand divided into thin pieces. In Patent Document 1, a carbon fiber strand having the number of filaments of 48000 (48K) expressed as split tow, a spreading bar with a crown and a splitting bar with a groove are provided. An apparatus is disclosed in which it is divided into thin carbon fiber strands having a filament number of several thousand units.

  Patent Document 2 discloses a carbon fiber fiber in a widened state at the same time as or after widening the carbon fiber strand with a widening jig that is continuously run while applying tension to the continuous carbon fiber strand and arranged in the middle of running. A method for dividing a carbon fiber strand is disclosed in which a part of the carbon fiber filament is cut by a cutting blade that rotates the strand in parallel with the running direction of the carbon fiber strand.

  Usually, the positional relationship between the carbon fiber filaments in the carbon fiber strand is not constant. In other words, when one of the carbon fiber filaments in the carbon fiber strand is traced in the longitudinal direction, the carbon fiber strand can be seen outside the carbon fiber strand, or the carbon fiber strand can be seen from outside the inside, It also swings from side to side or spirals. For this reason, as in Patent Document 1, in the method of dividing a thick strand through a grooved rod / roll, if the strand length of the carbon fiber to be continuously processed is long, the carbon fiber strand gradually rotates, Twist accumulates and the carbon fiber strand cannot be wound up, or the carbon fiber strand is cut by the twist and cannot be divided. In order to remove the accumulated twist, there was a problem that the apparatus had to be stopped and continuous production was not possible.

  In addition, cutting some carbon fiber filaments with a cutting blade that rotates parallel to the running direction of the carbon fiber strands causes fluffing, fiber cutting, etc., resulting in a deterioration in the quality of the carbon fiber bundle, and the mechanical properties of the SMC molded product. There was a drawback that the strength decreased.

US Pat. No. 6,385,828 JP 2006-219780 A

N. Tsuchiyama, “The Mechanical Properties of Carbon Fiber SMC”, Proceedings of the Fourth International Materials (ICCM-IV), 1988. 497-503

  The present invention provides an SMC manufacturing method that can solve the above-described conventional problems and obtain an SMC at a level that satisfies the mechanical strength and the strength unevenness depending on the location.

  The first gist of the present invention is that a plurality of carbon fiber bundles are formed from a plurality of carbon fiber bundle wound bodies in which a plurality of carbon fiber bundles each imparted with convergence properties are wound around a single bobbin without being aligned. This is a method for producing a sheet molding compound that is pulled out, cut with a roving cutter, and simultaneously divided into carbon fiber bundles, and the cut carbon fiber bundles and a resin composition are mixed and sheeted.

  The second gist of the present invention is that a plurality of carbon fiber bundles each provided with convergence are arranged in parallel to each other and wound around a single bobbin. A method for producing a sheet molding compound in which a plurality of carbon fiber bundles are pulled out from a body, cut with a roving cutter and simultaneously divided into carbon fiber bundles, and the cut carbon fiber bundles and a resin composition are mixed and sheeted. is there.

  In these inventions, the carbon fiber bundles adjacent to each other are bonded with each other by a sizing agent, and as a roving cutter, a material to be cut is sandwiched between a rubber roll and a cutter roll having a cutter disposed on the peripheral surface. It is preferable to use a roving cutter.

  By selecting a specific multi-carbon fiber bundle wound body according to the present invention, it is possible to separate the fibers simultaneously with cutting from the multi-carbon fiber bundle to each carbon fiber bundle. As a result, a plurality of carbon fiber bundles obtained by firing a plurality of carbon fiber precursor fiber bundles can be wound as they are on a single bobbin, and new winders, bobbins and the like for winding a carbon fiber bundle can be obtained. Not only is capital investment unnecessary, but the number of creel during SMC production can be reduced.

  In particular, by using the winding body of the carbon fiber precursor fiber bundle described in Japanese Patent Application Laid-Open Nos. 2002-20037 and 2002-255448 related to the application of the present applicant, “winding on a single bobbin” In order to form a series of flow of “precursor fiber bundle → firing step → carbon fiber bundle wound around a single bobbin”, a conventional firing apparatus can be used as it is.

  In addition, since a large number of carbon fiber bundles can be pulled out from a single bobbin at an arbitrary speed and used as they are, it is not necessary to separately prepare a carbon fiber splitting device and split the carbon fiber bundle. Omission and reduction of equipment costs can be achieved. Even when a separate carbon fiber splitting device is used, splitting can be performed at high speed. Therefore, it is possible to split efficiently by using several splitting devices effectively. Furthermore, since the number of steps can be reduced as a whole, quality improvement of the carbon fiber bundle can be expected.

Furthermore, the SMC obtained by the present invention has a level that can satisfy the mechanical strength and the unevenness in strength depending on the location.

Conceptual diagram of a plurality of carbon fiber bundle wound bodies in which a plurality of carbon fiber bundles each having a converging property are wound around a single bobbin without being aligned. Conceptual diagram of a plurality of carbon fiber bundle wound bodies in which a plurality of carbon fiber bundles each having a converging property are wound around a single bobbin without being aligned. FIG. 2 is an enlarged view of a plurality of carbon fibers wound up. Conceptual diagram of sheet molding compound (SMC) manufacturing equipment Conceptual diagram of roving cutter device

Hereinafter, the present invention will be described in detail.
<Multi-carbon fiber bundle winder>
In the present invention, it is important to use a plurality of carbon fiber bundle wound bodies in which a plurality of carbon fiber bundles each having a converging property are wound around a single bobbin without being aligned.

  As this multiple carbon fiber bundle wound body, the multiple carbon fiber bundle wound body described in Japanese Patent Application Laid-Open No. 2002-255448 related to the applicant's application can be used.

  An embodiment of a multiple carbon fiber bundle wound body used in the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the multiple carbon fiber bundle wound body 1 in the present embodiment is obtained by winding a carbon fiber bundle 4 around a single bobbin 2.

  The carbon fiber bundle 4 is composed of 500 to 24000, preferably 1000 to 8000 carbon fiber filaments. As the carbon fiber bundle in the present invention, an existing carbon fiber bundle obtained by firing a carbon fiber precursor bundle such as polyacrylonitrile, pitch and cellulose can be used. Furthermore, the carbon fiber bundle 4 of this embodiment is provided with convergence. Here, “convergence is imparted” refers to a state in which the carbon fiber bundles are gathered without being scattered for each number of the carbon fiber bundles. For example, by giving convergence to 3000 carbon fibers, one unitary fiber form is formed.

  By imparting convergence, there is an advantage that generation of fluff, winding around a roll, and the like are prevented, and the passage through the firing process and the passage through the separation process described later are improved. As means for imparting convergence, for example, known means such as means for entanglement of filaments such as gas entanglement treatment and needle punch treatment, and means by false twisting can be used. Preferably, performing the gas entanglement treatment at a gas pressure of 80 to 650 kPa is suitable for imparting sufficient convergence and preventing the fluff generation of the carbon fiber bundle.

  As an embodiment of the multiple carbon fiber bundle wound body in the present invention, as shown in FIG. 1, a single bobbin 2 without aligning at least two, preferably 2 to 6 carbon fiber bundles 4. It may be wound around. Here, “without aligning” means that the carbon fiber bundles do not overlap each other and exist independently in parallel as shown in FIG. Therefore, what is referred to as “synthetic yarn”, in which a plurality of carbon fiber bundles are stacked in parallel or vertically and are arbitrarily twisted or entangled to make these carbon fiber bundles into a single carbon fiber yarn. It is a different state.

  By winding a plurality of carbon fiber bundles in this way, when dividing into carbon fiber bundles by a separating apparatus described later, the carbon fiber bundles can be divided at an arbitrary speed while suppressing fuzz and fiber cutting. Moreover, as embodiment of the multiple carbon fiber winding body in this invention, as shown in FIG. 2, the state which has arrange | positioned the carbon fiber bundle 4 of at least 2 pieces, Preferably 2-6 pieces in parallel mutually is maintained. It may be wound around a single bobbin 2 as it is. Here, “arranged in parallel with each other” means that the carbon fiber bundles are adjacent to each other in parallel without overlapping each other, as shown in FIG. For example, the two carbon fiber bundles 4 are arranged in parallel with no gap between each other without overlapping each other. By winding a plurality of carbon fiber bundles in this way, when cutting to a desired length with a roving cutter described later, it is possible to cut and split at a normal roving cutter operating speed while suppressing fuzz and fiber breakage. it can.

  Further, as shown in FIG. 3 which is an enlarged view of the front end portion of the plurality of carbon fiber bundles 3 in FIG. 2, the carbon fiber bundles 4 are bonded to each other by adjoining surfaces 5 with a sizing agent. It is preferable. This is because simply winding a plurality of carbon fiber bundles causes the carbon fiber bundles wound around the plurality of carbon fiber bundle winding bodies to be scattered, which is inconvenient to handle. Bonding with the sizing agent is performed by, for example, firing two carbon fiber bundle precursors arranged in parallel to each other and drying, and maintaining the obtained two carbon fiber bundles arranged in parallel. It is carried out by immersing in a sizing solution while being dried. Thereby, the filaments contained in the carbon fiber bundle 4 are bonded to each other by the sizing agent, and the adjacent carbon fiber bundles 4 are also bonded to each other on the adjacent surface 5. The sizing agent used here is not particularly limited, but for example, those mainly composed of epoxy, urethane, ester and mixed systems thereof can be used. When preparing a sizing agent solution composed of a compound insoluble in water, it is preferable to use a surfactant for dispersion stability. As the surfactant used here, any of nonionic, cationic, anionic and the like can be used. Further, by blending a softener such as an adduct of fatty acid ethylene oxide, it is possible to obtain a carbon fiber that is more excellent in terms of fineness. In addition, as a softening agent added at this time, it is preferable to select a water-soluble type. The multiple carbon fiber bundle wound body 1 according to an embodiment of the present invention is obtained by winding the multiple carbon fiber bundles 3 around the bobbin 2 while maintaining the state in which the multiple carbon fiber bundles 3 are arranged in parallel.

  As a winding method around the bobbin 2, for example, a known winding method such as so-called cheese winding, parn winding, cone winding or the like can be used. The bobbin 2 may be formed of any material, but is preferably paper, plastic, or metal. The shape of the bobbin 2 may be any known shape as long as it is suitable for winding the carbon fiber bundle 4. For example, a bobbin shaped like a cylinder may be used. For example, in the case of a cylindrical bobbin, the size of the bobbin 2 is 60 to 210 mm in outer diameter, 50 to 200 mm in inner diameter, and 150 to 1000 mm in length. A plurality of carbon fiber bundles are wound on such a bobbin, for example, 500 to 20000 m, preferably 800 to 12000 m. The size of the obtained multiple carbon fiber bundle wound body is, for example, 70 to 1000 mm in diameter and 150 to 1000 mm in width, although it depends on the number of windings and the shape of the bobbin.

<Sheet molding compound manufacturing equipment>
An embodiment of a sheet molding compound manufacturing apparatus that can be suitably used in the present invention will be described with reference to FIG. The sheet molding compound manufacturing apparatus 100 includes:
A creel (not shown) for rotatably holding a plurality of carbon fiber bundle winding bodies,
A roving cutter 31 for cutting the drawn multiple carbon fiber bundles 1 to a desired fiber length;
Unwinder 21 for unwinding upper and lower films,
A daughter blade 12 for applying a resin composition 11 on a film with a desired thickness;
Roller group 24 for applying pressure to impregnate the carbon fiber bundle with the resin composition,
It comprises a mesh belt 22 for transferring the sheet molding compound in the middle of impregnation, and a winder 25 for winding up the sheet molding compound that has been impregnated.

<Roving cutter>
An embodiment of a roving cutter used in the present invention will be described with reference to the drawings. As shown in FIGS. 4 and 5, the roving cutter 31 of this embodiment includes a rubber roller 32 and a cutter roller 33. Further, the cutter roller is provided with a blade 34 on its peripheral surface separated by a desired cut length.

In the method for producing a sheet molding compound of the present invention, a plurality of carbon fiber bundles each provided with convergence properties are wound as a carbon fiber bundle on a single bobbin without being aligned. By pulling out a plurality of carbon fiber bundles from the body, the carbon fiber bundles can be easily separated at the same time as being cut with a roving cutter, and the carbon fiber bundles can be divided smoothly and continuously.
(Example)
Hereinafter, the effects of the present invention will be specifically described with reference to examples.

<Multi-carbon fiber bundle wound body 1>
Convergence was imparted to 3000 polyacrylonitrile-based carbon fiber precursors using an air entanglement processor to obtain a carbon fiber precursor bundle.

  This carbon fiber precursor bundle was subjected to a flameproofing treatment in air at 230 to 270 ° C. for 45 minutes, and subsequently subjected to a carbonization treatment at 1400 ° C. for 1 minute. The obtained carbon fiber bundle was immersed in an epoxy sizing agent solution obtained by emulsifying 80 parts of an epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., jER828) with 20 parts of a nonionic emulsifier, and then dried.

  The basis weight of this carbon fiber bundle was 2000 dtex. A plurality of carbon fiber bundles are wound around a cylindrical bobbin having an inner diameter of 76 mm, an outer diameter of 82 mm, and a length of 280 mm while simultaneously pulling out the four obtained carbon fiber bundles independently and at the same speed (100 m / s). Winding body 1 was obtained.

<Multi-carbon fiber bundle wound body 2>
Other than changing 3000 polyacrylonitrile-based carbon fiber precursors to 6000, the same operation as in <multiple carbon fiber bundle wound body 1> was carried out independently, and the obtained two carbon fiber bundles were independently arranged. And while drawing simultaneously at the same speed (100 m / s), it wound around the cylindrical bobbin of inner diameter 76mm, outer diameter 82mm, and length 280mm, and obtained the multiple carbon fiber bundle winding body 2.

<Multi-carbon fiber bundle wound body 3>
A plurality of carbon fiber bundles were operated in the same manner as in <multiple carbon fiber bundle wound body 2> except that the obtained eight carbon fiber bundles were pulled out independently and at the same speed (100 m / s) at the same time. A bundle wound body 3 was obtained.

<Resin composition>
Resins and the like shown in Table 1 were added at the blending amounts, mixed and stirred to obtain a resin composition.

<Formation of flat molded plate>
SMC was charged into a molding die at a charge rate of 65% (ratio of SMC area to mold area) and cured by heating and pressing for 2 minutes under the conditions of a mold temperature of 145 ° C. and a pressure of 8 Mpa, and a thickness of 2 mm. A 300 mm square flat plate was obtained.

<Measurement of mechanical properties of molded plate>
A bending strength test piece having a length of 60 mm and a width of 25 mm was cut out from the molded plate. Using a 5 kN Instron universal testing machine, a three-point bending test was performed at L / D = 16 and a crosshead speed of 2.6 mm / min, and the bending strength was measured. The number of test pieces measured was n = 6, and the average value was the bending strength. Further, the coefficient of variation (CV (%)) was obtained by dividing the standard deviation by the average value.

  Using the SMC manufacturing apparatus shown in FIG. 4, a sheet molding compound was manufactured using the multiple carbon fiber bundle wound body 1 and the resin composition.

At this time, the weight of the resin composition on the upper and lower films is adjusted to 600 g / m ² , and the multiple carbon fiber bundle wound body 1 is placed on a roving cutter (cut length: 25 mm) per 1 cm width. The number was adjusted so that the basis weight of the carbon fiber bundle was 1350 g / m ² . The obtained SMC (carbon fiber content 53 mass%) was allowed to stand at 23 ° C. for 24 hours, and then molded under the above conditions to obtain a flat molded plate. The evaluation results are shown in Table 2.

  SMC and a flat molded plate were obtained in the same manner as in Example 1 except that the multiple carbon fiber bundle wound body was replaced with the multiple carbon fiber bundle wound body 2. The evaluation results are shown in Table 2.

An SMC and a flat molded plate were obtained in the same manner as in Example 1 except that the multiple carbon fiber bundle wound body was changed to the multiple carbon fiber bundle wound body 3. The evaluation results are shown in Table 2.
(Comparative Example 1)

SMC and a flat molded plate were obtained in the same manner as in Example 1 except that a single carbon fiber bundle wound body having 48,000 filaments (48K) was used. The evaluation results are shown in Table 2.
(Comparative Example 2)

SMC and a flat molded plate were obtained in the same manner as in Example 1 except that a single carbon fiber bundle wound body having 12,000 filaments was used. The evaluation results are shown in Table 2.
(Comparative Example 3)

  An SMC and a flat molded plate were obtained in the same manner as in Example 1 except that a single carbon fiber bundle wound body having 3000 filaments (3K) was used. The evaluation results are shown in Table 2.

  In the present invention, when heated and pressed in a mold, the reinforcing fiber and the resin composition flow as one body and fill the cavity, so that the thickness is partially different, the rib has a boss, etc. The present invention relates to a method for producing SMC, which is an intermediate material advantageous for obtaining molded products of various shapes.

DESCRIPTION OF SYMBOLS 1 Multiple carbon fiber bundle winding body 2 Bobbin 3 Multiple carbon fiber bundle 4 Carbon fiber bundle 11 Resin composition 12 Doctor blade 21 Film unwinding machine 22 Mesh belt 24 Roller group 25 SMC
31 Roving cutter 32 Rubber roller 33 Cutter roller 34 Blade

Claims (4)

  A plurality of carbon fiber bundles, each of which has been imparted with convergence, are drawn out from a wound body of a plurality of carbon fiber bundles wound around a single bobbin without being aligned, and cut with a roving cutter. At the same time, a method for producing a sheet molding compound, in which a carbon fiber bundle divided and cut into carbon fiber bundles and a resin composition are mixed and formed into a sheet.   A plurality of carbon fiber bundles each provided with convergence properties are arranged in parallel to each other, and a plurality of carbon fiber bundles are drawn from a plurality of carbon fiber bundle wound bodies wound around a single bobbin, A method for producing a sheet molding compound in which a carbon fiber bundle that has been cut with a roving cutter and divided into carbon fiber bundles at the same time is mixed and sheeted.   The method for producing a sheet molding compound according to claim 2, wherein the carbon fiber bundles adjacent to each other are bonded together by a sizing agent.   The manufacturing method of the sheet molding compound of any one of Claims 1-3 using the roving cutter which pinches | interrupts a to-be-cut object between a rubber roll and the cutter roll which has arranged the cutter on the surrounding surface as a roving cutter.

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