Apparatus for manufacturing carbon fiber prepreg and manufacturing method thereof

Abstract

An apparatus for manufacturing a carbon fiber prepreg according to an embodiment of the present invention comprises: a carbon fiber creel for continuously supplying carbon fibers to a water tank; a water tank having a medium to spread the carbon fibers by transmitting ultrasonic waves to the carbon fibers, supplied from the carbon fiber creel, through the medium; an ultrasonic wave generating device for transmitting ultrasonic waves into the water tank; and an impregnation unit for impregnating the spread carbon fibers with a resin, whereby the spreadability and uniformity of the carbon fibers are improved, so that a prepreg and a carbon fiber-reinforced plastic produced therefrom have excellent mechanical properties, and the molding into a thin prepreg can solve defects such as local flexure or bending.

Description

Carbon fiber prepreg manufacturing device and manufacturing method thereof

[0001] The present invention relates to a carbon fiber prepreg manufacturing device and a manufacturing method thereof, and more specifically, to a carbon fiber prepreg manufacturing device and a manufacturing method thereof capable of improving the spreadability and uniformity of carbon fiber tow by spreading carbon fibers using an ultrasonic cavitation effect.

[0002] In general, carbon fiber reinforced plastics (CFRP) are made of carbon fibers as reinforcing material and thermosetting or thermoplastic resin as base material, and have the characteristics of excellent mechanical properties while being lighter than materials such as metals. One method for manufacturing such carbon fiber reinforced plastics is to use a prepreg as an intermediate form. Carbon fiber prepreg is an intermediate material for manufacturing the final molded product, carbon fiber reinforced plastic, and is a sheet-like product in which carbon fibers are pre-impregnated with resin. Such prepregs are widely used in the manufacturing of carbon fiber reinforced plastics because they can easily increase the fiber content, which significantly affects the mechanical properties of carbon fiber reinforced plastics, or uniformly manage the target fiber content, and can reduce the occurrence of internal defects such as voids. They can also easily improve physical properties such as heat resistance and impact strength.

[0003] Meanwhile, carbon fiber prepreg is produced by spreading continuous carbon fibers to a desired width and impregnating the carbon fiber tow with resin. Carbon fibers are treated with a sizing agent to protect and concentrate the fibers. Conventional spreading methods, which apply energy through friction, vibration, or fluids to forcefully spread the fibers to the desired width, have been used. However, these methods have limitations in terms of scalability and uniformity.

[0004] If the carbon fibers lack the flexibility to spread to the desired width, gaps will occur when manufacturing thin prepregs with a fiber basis weight of less than 50 gsm, making prepreg manufacturing impossible. Furthermore, even if the carbon fibers are spread to the desired width, if the carbon fiber filament density is uneven, residual stress differences in the molded carbon fiber-reinforced plastic can occur, resulting in localized warping or bending.

[0005] The present invention has been made to solve the above problems and to meet the conventional requirements, and the problem to be solved by the present invention is to provide a carbon fiber prepreg manufacturing device and a manufacturing method thereof capable of manufacturing a carbon fiber prepreg through a carbon fiber spreading method using the ultrasonic cavitation effect in order to improve the spreadability of carbon fibers during the manufacturing of carbon fiber prepreg and to make the density of spread carbon fiber filaments uniform.

[0006] The above and other objects and advantages of the present invention will become apparent from the following description of preferred embodiments.

[0007] The above object is achieved by a carbon fiber prepreg manufacturing device including a carbon fiber creel that continuously supplies carbon fibers into a tank, a tank equipped with a medium that transmits ultrasonic waves through the medium to carbon fibers supplied from the carbon fiber creel to spread the carbon fibers, an ultrasonic generator that transmits ultrasonic waves into the tank, and an impregnation unit that impregnates the spread carbon fibers with resin.

[0008] Preferably, the frequency of the ultrasonic waves generated from the ultrasonic generator may be 30 to 180 kHz.

[0009] Preferably, the tank includes a first tank and a second tank, and the ultrasonic generator includes a first ultrasonic generator that transmits ultrasonic waves into the first tank and a second ultrasonic generator that transmits ultrasonic waves into the second tank, and the first ultrasonic generator generates ultrasonic waves of 30 to 180 kHz in the first tank to primarily spread carbon fibers supplied to the first tank, and the second ultrasonic generator generates ultrasonic waves of more than 180 kHz and less than 1 MHz in the second tank to primarily spread the carbon fibers.

[0010] Preferably, the output (Power) of the ultrasonic generator may be 8 to 50 watts per 1 L of medium in the tank.

[0011] Preferably, the medium may be water or an organic solvent at a temperature of 20 to 80°C.

[0012] Preferably, the organic solvent may include at least one of a ketone compound and an alcohol compound.

[0013] Preferably, it may further include nip rolls individually positioned at the front and rear ends of the tank to independently control the tension of the carbon fiber passing through the tank.

[0014] Preferably, the nip roll can be configured to control the tension applied to the carbon fiber within the tank to 50 to 200 gf / tow.

[0015] Preferably, the tank may further include a circulator for circulating the medium to filter the carbon fiber yarns.

[0016] Preferably, it may further include a drying oven for drying the carbon fibers spread in the tank.

[0017] Preferably, it may further include a trench roll located at the rear end of the drying furnace and configured to control the width and position of the spread carbon fibers dried in the drying furnace.

[0018] In addition, the above object is achieved by a method for manufacturing a carbon fiber prepreg, which comprises a first step of continuously supplying carbon fibers to a tank containing a medium, a second step of spreading the carbon fibers by applying ultrasonic waves to the supplied carbon fibers through the medium, a third step of passing the spread carbon fibers through the tank, and a fourth step of impregnating the inside of the spread carbon fibers passed through the tank with a resin.

[0019] Preferably, the ultrasound of the second stage may have a frequency of 30 to 180 kHz.

[0020] Preferably, the second step includes a first spreading step and a second spreading step in which ultrasonic waves having different frequencies are applied to the supplied carbon fibers to continuously spread the carbon fibers, and the ultrasonic waves of the first spreading step may have a frequency of 30 to 180 kHz, and the ultrasonic waves of the second spreading step may have a frequency of more than 180 kHz and less than or equal to 1 MHz.

[0021] Preferably, the second step may include a process of filtering carbon fiber single yarns by circulating the medium within the tank through a circulator including a filter.

[0022] Preferably, it may include a process of controlling the tension of the carbon fiber to 50 to 200 gf / tow through nip rolls independently driven at the front end of the tank during the first stage and at the back end of the tank after the third stage.

[0023] Preferably, it is performed after the third step, and may further include a drying step of drying the medium remaining in the carbon fiber through hot air from a drying furnace.

[0024] Preferably, the process may further include a controlling step for controlling the width and arrangement of the spread carbon fibers to be suitable for prepreg manufacturing, which is performed after the drying step.

[0025] Preferably, the medium may be water or an organic solvent at a temperature of 20 to 80°C.

[0026] In addition, the above object is achieved by a prepreg manufactured by the above-described carbon fiber prepreg manufacturing method.

[0027] According to the carbon fiber prepreg manufacturing device and manufacturing method according to the present invention, the spreadability of carbon fiber can be dramatically improved compared to the conventional spreading method. In order to manufacture a thin prepreg having a basis weight of less than 50 gsm using the commonly used T700 grade 12K carbon fiber, the width of the carbon fiber tow must be spread more than twice the initial width. However, if the width is spread more than twice with the conventional spreading technique, gaps often occur. On the other hand, according to the carbon fiber prepreg manufacturing device and manufacturing method according to the present invention, the width of the carbon fiber tow can be spread more widely, and at the same time, the width of the spread carbon fiber is also constant, so that gap defects do not occur and a thinner prepreg can be manufactured, etc.

[0028] In addition, the carbon fiber prepreg manufacturing device and manufacturing method according to the present invention have the advantage of being able to obtain a carbon fiber prepreg that is spread more uniformly than a carbon fiber prepreg spread using a conventional spreading method. When a prepreg and carbon fiber reinforced plastic are manufactured using carbon fibers spread uniformly in this manner, the mechanical properties are improved, and in particular, when formed into a thin prepreg, defects such as local warping or bending can be resolved.

[0029] However, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0030] Figure 1 is a configuration diagram of a carbon fiber prepreg manufacturing device according to one embodiment of the present invention.

[0031] Figure 2 is a configuration diagram of a carbon fiber prepreg manufacturing device according to another embodiment of the present invention.

[0032] Figure 3 is a flow chart of a method for manufacturing a carbon fiber prepreg according to one embodiment of the present invention.

[0033] Figure 4a is a cross-sectional schematic diagram of a prepreg manufactured using a conventional spreading method.

[0034] Figure 4b is a cross-sectional schematic diagram of a prepreg manufactured through a method for manufacturing a carbon fiber prepreg according to one embodiment of the present invention.

[0035] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0036] In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and the same reference numerals are added to the same or similar components throughout the specification. In addition, the thickness is shown in the drawings to clearly express various layers and regions. In addition, when it is mentioned in this specification that an element is disposed "on" or "over" another element, the element may be disposed directly on the other element, or there may be elements interposed between the elements. On the other hand, when it is mentioned that an element is disposed "directly on" or "directly above" another element, there may not be interposed elements.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of a conflict, the present specification, including its definitions, will govern. Furthermore, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0038] The term "including" in this specification means that other components may be included rather than excluding other components unless specifically stated to the contrary.

[0039] The term "combination of these" in this specification means a mixture or combination of one or more of the described components.

[0040] As used herein, the term "and / or" is meant to include any and all combinations of one or more of the items described herein. As used herein, the term "or" means "and / or." The expressions "at least one" or "one or more" preceding elements herein may supplement the entire list of elements and do not imply that they supplement individual elements described above.

[0041] In this specification, each component is a concept that includes both singular and plural.

[0042] Hereinafter, a preferred embodiment according to the present invention will be described in more detail with reference to the attached drawings.

[0043] Referring to FIG. 1, which is a configuration diagram of a carbon fiber prepreg manufacturing apparatus according to an embodiment of the present invention, the carbon fiber prepreg manufacturing apparatus according to an embodiment of the present invention includes a carbon fiber creel (1) that continuously supplies carbon fibers to a tank, a tank (4) equipped with a medium that transmits ultrasonic waves to carbon fibers supplied from the carbon fiber creel through the medium to spread the carbon fibers, an ultrasonic generator (5, 6) that transmits ultrasonic waves into the tank, and an impregnation unit (10) that impregnates the spread carbon fibers with resin, and may further include nip rolls (2, 3), a circulator (7), a drying furnace (8), and a trench roll (9).

[0044] First, in order to spread carbon fibers, a carbon fiber creel (1) continuously supplies carbon fiber tows to a tank (4) filled with a medium, and the supplied carbon fibers are immersed in the tank, spread, and then pass through the tank.

[0045] In one embodiment, the medium filled in the tank (4) is preferably water or an organic solvent, and the organic solvent preferably includes at least one of a ketone compound and an alcohol compound. In addition, the temperature of the medium filled in the tank (4) is preferably 20 to 80°C. When an organic solvent is used as a medium, the spreading effect can be increased by dissolving and removing the sizing agent coated on the fiber surface for focusing the carbon fiber tow, but since the organic solvent must be removed after spreading, it can cause environmental problems. On the other hand, when water is used as a medium, no environmental problems occur, and effective spreading is possible because water has a higher surface tension and stronger cavitation intensity than organic solvents. At this time, when the temperature of the water is maintained at a level of 20 to 80°C higher than room temperature, the cavitation intensity can be maintained at a level that is not excessive, and the cavitation density increases, enabling effective spreading.

[0046] In addition, the ultrasonic generator (5, 6) is composed of an ultrasonic generator and a vibrator, and is placed in the tank (4), and transmits ultrasonic waves generated from the ultrasonic generator to carbon fibers (carbon fiber tow) continuously supplied to the tank (4) through the medium in the tank (4), thereby spreading the carbon fibers. More specifically, the ultrasonic waves applied to the medium in the tank through the ultrasonic generator (5, 6) transmit physical impact energy to the carbon fibers that are focused by cavitation and particle acceleration phenomena, thereby spreading the carbon fiber tow.

[0047] The frequency of the ultrasonic waves generated from these ultrasonic generators (5, 6) is preferably 30 to 180 kHz. The lower the frequency of the ultrasonic waves, the greater the intensity of cavitation and the less the density of cavitation. Therefore, when the ultrasonic wave frequency is set to less than 30 kHz, the carbon fiber spreading effect increases, making it possible to spread the carbon fibers to a width suitable for manufacturing thin prepregs, but the uniformity of precise dispersion of each filament deteriorates and the carbon fiber single yarn increases. On the other hand, when the ultrasonic wave frequency exceeds 180 kHz, the intensity of cavitation decreases, making it difficult to spread the carbon fibers to a desired width.

[0048] As described above, the carbon fiber prepreg manufacturing device according to one embodiment of the present invention can be used not only to apply ultrasonic waves through an ultrasonic generator (5, 6) in a single tank (4), but also to apply a multi-tank system in which two tanks can apply ultrasonic waves of different frequencies. A configuration applying such a multi-tank system will be described again in Fig. 2.

[0049] In addition, it is preferable that the output (Power) of the ultrasonic generator (5, 6) applied to the tank (4) is 8 to 50 watts per 1 L of medium in the tank (8 to 50 Watt / L). If the output of the ultrasonic generator (5, 6) is less than 8 Watt / L, the intensity of the ultrasonic waves is insufficient, so that the spreading effect of the carbon fibers is reduced, and it is impossible to spread the carbon fibers to the desired width. On the other hand, if the output of the ultrasonic generator (5, 6) exceeds 50 Watt / L, the intensity of the ultrasonic waves is high, so that the spreading of the carbon fibers is sufficient, but excessive energy is transmitted to the carbon fibers, so that the occurrence of single fibers in the carbon fibers increases, resulting in a deterioration in surface quality.

[0050] In addition, when the tension of the carbon fiber tow passing through the tank (4) is high, even if sufficient energy is applied by ultrasonic waves, the spreading effect of the carbon fiber is significantly reduced. Therefore, it is important to keep the tension of the carbon fiber tow running in the tank low. To this end, it is desirable to install independently driveable nip rolls (2, 3) at the front and rear of the tank to independently control the tension of the carbon fiber tow passing through the tank and increase the spreading effect of the carbon fiber. The tension applied to the carbon fiber in the tank (4) can be implemented by configuring a closed circuit that maintains the tension of the carbon fiber at a desired level by automatically controlling the speed of the independently drive nip roll by reading the value and using a load cell that can measure the tension of the carbon fiber tow.

[0051] In particular, it is preferable to adjust the tension applied to the carbon fiber in the tank (4) to 50 to 200 gf / tow using the nip roll (2) at the front end of the tank and the nip roll (3) at the rear end of the tank. When the tension of the carbon fiber tow is less than 50 gf / tow, that is, when the tension actually applied is less than 50 gf / tow, almost no tension is applied to the carbon fiber, so the straightness of the fiber is not maintained, and interference and tangling between the tows occur, making it difficult to manufacture the prepreg. In addition, when the tension exceeds 200 gf / tow, the spread carbon fiber tow may shrink again, narrowing the width, so that the spreading effect may be significantly reduced.

[0052] In addition, when impact energy is transmitted to the carbon fiber by ultrasonic waves within the tank (4) and the carbon fiber filaments are broken during the spreading process, carbon fiber single fibers are generated. The single fibers generated at this time remain on the surface of the prepreg and cause defects on the surface of the prepreg and the surface of the molded product to which the same is applied. Therefore, in order to effectively remove single fibers, a circulator (7) including a filter may be positioned within the tank (4). The circulator (7) positioned within the tank (4) circulates the medium within the tank (4) to filter and remove single fibers floating within the medium.

[0053] In addition, since the carbon fibers that have passed through the spreader (4) contain water or organic solvents used as a medium, a drying process is required. For this purpose, a drying furnace (8) for drying the carbon fibers spread in the spreader (4) may be positioned after the spreader (4) and the rear nip roll (3). The drying furnace (8) can remove water or organic solvents contained in the carbon fibers through heating by infrared rays or a convection oven, and a floating type drying furnace having upper and lower nozzles that spray hot air is particularly effective. Since the carbon fiber tow passes in a fluid state between the upper and lower nozzles that spray hot air, an additional spreading effect is provided by the pressure difference of the fluid, and it is possible to maintain the width of the spread carbon fibers and the density of the filaments uniformly.

[0054] In addition, the spread carbon fibers that have passed through the drying furnace (8) require precise tow arrangement or fine adjustment of the width of the tows to ensure they are suitable for prepreg manufacturing. If the carbon fiber tows are not positioned correctly or the width of the spread tows is not consistent, gap defects may occur on the surface of the prepreg. Therefore, it is desirable to manufacture prepregs without gap defects by passing the carbon fibers through a bar roll or trench roll (9) that can provide friction after the drying furnace.

[0055] In addition, carbon fibers spread to be suitable for prepreg manufacturing can be subjected to an impregnation process through an impregnation unit (10) to manufacture prepregs. At this time, the impregnation process of the impregnation unit (10) can use a conventional general impregnation process. Conventional impregnation processes may include a hot melt process for laminating a thermosetting resin film to carbon fibers, a process for scattering a thermoplastic resin or laminating a thermoplastic film, or a solvent process for dipping carbon fibers in a tank in which a resin is dissolved in a solvent and then drying them. Through this impregnation process, it is possible to manufacture a prepreg without internal pores by infiltrating the resin into the carbon fiber tow.

[0056] Alternatively, it is possible to attach a binder to the spread carbon fibers to fix them in a spread state, and the carbon fibers bound in this way can be used for weaving carbon fiber fabrics such as spread tow fabrics.

[0057] A carbon fiber prepreg manufacturing apparatus according to another embodiment of the present invention will be described with reference to FIG. 2, which is a schematic diagram of a carbon fiber prepreg manufacturing apparatus according to another embodiment of the present invention. However, any description overlapping with that of FIG. 1, which is a carbon fiber prepreg manufacturing apparatus according to one embodiment of the present invention, will be omitted.

[0058] Referring to FIG. 2, a carbon fiber prepreg manufacturing device according to another embodiment of the present invention applies a multi-tank system, and unlike FIG. 1, it has two tanks, a first tank (4-1) and a second tank (4-2), and may have a first ultrasonic generator (5-1, 6-1), a second ultrasonic generator (5-2, 6-2), and first and second circulators (7-1, 7-2) corresponding to the two tanks (4-1, 4-2). In this specification, a carbon fiber prepreg manufacturing device using two tanks among the multi-tank systems is described as an example, but a carbon fiber prepreg manufacturing device using three or more tanks also falls within the scope of the present invention.

[0059] Unlike the carbon fiber prepreg manufacturing device according to Fig. 1, which has one ultrasonic generator (5, 6) in one tank (4) and spreads carbon fibers at an ultrasonic frequency of 30 to 180 kHz, it is preferable that the carbon fiber prepreg manufacturing device according to Fig. 2 performs two-stage spreading at different ultrasonic frequencies in the first tank (4-1) at the front end and the second tank (4-2) at the rear end.

[0060] More specifically, carbon fibers continuously supplied from a carbon fiber creel (1) are first spread by ultrasonic waves generated by a first ultrasonic generator (5-1, 6-1) as they pass through a first tank (4-1) filled with a medium, and the carbon fibers first spread in the first tank (4-1) are secondarily spread by ultrasonic waves generated by a second ultrasonic generator (5-2, 6-2) as they pass through a second tank (4-2).

[0061] In one embodiment, it is preferable that the frequency of the ultrasonic waves generated from the first ultrasonic generator (5-1, 6-1) is lower than the frequency of the ultrasonic waves generated from the second ultrasonic generator (5-2, 6-2). Accordingly, it is more preferable that the frequency of the ultrasonic waves generated from the first ultrasonic generator (5-1, 6-1) is 30 to 180 kHz, and the frequency of the ultrasonic waves generated from the second ultrasonic generator (5-2, 6-2) is more preferably more than 180 kHz and 1 MHz or less. In this way, through two spreading processes having different ultrasonic frequencies, it is possible to precisely disperse the carbon fiber filaments while minimizing the occurrence of single fibers in the carbon fibers. That is, through the first spreading, the carbon fibers can be spread to a desired spreading width, and through the second spreading, the carbon fiber filaments can be finely and precisely dispersed once more while minimizing the occurrence of single fibers in the carbon fibers.

[0062] A method for manufacturing a carbon fiber prepreg according to an embodiment of the present invention will be described with reference to FIG. 3, which is a flowchart of a method for manufacturing a carbon fiber prepreg according to an embodiment of the present invention. However, any description that overlaps with the contents of FIGS. 1 and 2 will be omitted.

[0063] Referring to FIG. 3, a method for manufacturing a carbon fiber prepreg according to one embodiment of the present invention includes a first step (S301) of continuously supplying carbon fibers to a tank containing a medium, a second step (S302) of spreading the carbon fibers by applying ultrasonic waves to the supplied carbon fibers through the medium, a third step (S303) of passing the spread carbon fibers through the tank, and a fourth step (S304) of impregnating the inside of the spread carbon fibers passed through the tank with a resin.

[0064] First, the first step (S301) is a step of continuously supplying carbon fibers to a tank containing a medium, and is a step of continuously supplying carbon fibers (carbon fiber tow) from a carbon fiber creel (1) to a tank (4) filled with a medium.

[0065] Next, the second step (S302) is a step of spreading the carbon fibers by applying ultrasonic waves through a medium to the carbon fibers supplied in the first step.

[0066] In one embodiment, in the second step (S302) of spreading carbon fibers by applying ultrasonic waves to the supplied carbon fibers through a medium, spreading is possible using a multi-tank method using one tank or two or more tanks.

[0067] Among these, when the second step (S302) is performed using one tank, ultrasonic waves of 30 to 180 kHz can be generated to spread carbon fibers through the medium of the tank.

[0068] In addition, when performing the second step (S302) using two tanks among the multi-tank methods, it may include a first spreading step and a second spreading step in which ultrasonic waves having different frequencies are applied to the supplied carbon fibers to continuously spread the carbon fibers. More specifically, the carbon fibers may be spread through a two-step spreading step including a first spreading step in which ultrasonic waves of 30 to 180 kHz are generated to spread the carbon fibers, and a second spreading step in which ultrasonic waves of more than 180 kHz and less than 1 MHz are generated to spread the carbon fibers that have been spread in the first step. In this way, through the two spreading processes with different ultrasonic frequencies, the carbon fiber filaments can be precisely dispersed while minimizing the occurrence of single fibers in the carbon fibers. That is, the desired spreading width of the carbon fiber can be secured through the first spreading, and the carbon fiber filaments can be dispersed finely and precisely once again through the second spreading, thereby minimizing the occurrence of single fibers in the carbon fiber.

[0069] In addition, the second step (S302) may include a process of filtering carbon fiber single yarns by circulating the medium within the tank through a circulator including a filter. Some carbon fiber filaments are broken by ultrasonic waves transmitted within the tank, generating carbon fiber single yarns. The single yarns generated at this time remain on the surface of the prepreg, causing defects on the surface of the prepreg and the surface of the molded article to which the same is applied. Therefore, it is preferable to circulate the solvent within the tank through a circulator including a filter to filter and remove single yarns floating within the medium through the filter.

[0070] Next, the third step (S303) is a step of passing the carbon fibers spread in the second step (S302) through a tank.

[0071] In addition, the process may include controlling the tension of the carbon fiber to 50 to 200 gf / tow through independently driven nip rolls at the front of the tank during the first stage and at the rear of the tank after the third stage. If the tension of the carbon fiber tow passing through the tank is high, the spreading effect of the carbon fiber is significantly reduced even if sufficient ultrasonic energy is applied. Therefore, it is important to maintain a low tension of the carbon fiber tow traveling within the tank. To this end, it is preferable to install independently driven nip rolls at the front and rear of the tank to control the tension.

[0072] Additionally, a drying step, performed after the third step, may include drying the remaining medium on the carbon fibers using hot air from a drying furnace. Since the carbon fibers, spread and passed through the tank, contain the water or organic solvent used as the medium, a drying process is necessary. A floating drying furnace, with vertical nozzles that spray hot air, is particularly effective for this purpose.

[0073] In addition, after drying the spread carbon fibers through the drying step, an adjustment step may be further included to adjust the width and arrangement of the spread carbon fibers to be suitable for prepreg manufacturing by arranging rolls or trench rolls.

[0074] Finally, the fourth step (S304) manufactures a prepreg by impregnating the inside of the spread carbon fibers passed through the tank with a resin. The resin used here may be a composition generally including an epoxy resin in the art, and the epoxy resin may include at least one of a bisphenol A type epoxy, a bisphenol F type epoxy, a multifunctional epoxy, a novolac epoxy, a flame retardant epoxy, a cyclic aliphatic epoxy, and a rubber-modified epoxy.

[0075] As described above, according to the carbon fiber prepreg manufacturing apparatus and manufacturing method according to the present invention, a carbon fiber prepreg that is spread very uniformly can be obtained compared to a carbon fiber prepreg spread by a conventional technique, thereby making it possible to dramatically improve the spreadability and uniformity. Here, uniform spreading means that the carbon fiber filaments are distributed at a uniform density per a certain width or area, and after curing the prepreg, the number of carbon fiber filaments included in a certain area can be measured in a cross-section observed under a microscope by cutting it in the vertical direction of the fibers, and the standard deviation and coefficient of variation between samples can be evaluated.

[0076] FIG. 4a is a cross-sectional schematic diagram of a prepreg manufactured through a conventional spreading method, and FIG. 4b is a cross-sectional schematic diagram of a prepreg manufactured through a carbon fiber prepreg manufacturing method according to one embodiment of the present invention.

[0077] First, referring to Fig. 4a, the carbon fiber (401) before spreading is a carbon fiber before performing the spreading process, and represents a carbon fiber (401) with a tow width of 6 mm. In order to manufacture a thin prepreg having a basis weight of less than 50 gsm by applying a commonly used high-strength carbon fiber (T700SC-12000, Toray Advanced Materials), the width of the carbon fiber tow must be spread out to at least 2.7 times the initial width. However, when the carbon fiber is spread out to at least 2.7 times using a conventional spreading technique, the carbon fiber tow often does not spread out to the desired width, or the spread width is not uniform, resulting in gaps on the surface of the prepreg. For example, in the case of a carbon fiber prepreg (402) in which carbon fibers (carbon fibers before spreading, 401) having a tow width of 6 mm are spread to a tow width of 30 mm through a conventional spreading method that forcibly spreads them by applying energy through friction, vibration, fluid, etc., the spreadability and uniformity are reduced during the process in which the carbon fibers are forcibly spread, and the coefficient of variation of the number of carbon fiber filaments (filament density) between samples is 10% or more, showing an uneven distribution (density) of the number of carbon fiber filaments.

[0078] In contrast, when spreading carbon fibers using the method for manufacturing a carbon fiber prepreg according to an embodiment of the present invention as described above, as shown in FIG. 4b, it is possible to spread the carbon fibers 2 to 6 times the initial width, and since the width of the spread carbon fibers is constant, it is possible to manufacture a thinner prepreg without causing gap defects. For example, in the case of a carbon fiber prepreg (403) in which carbon fibers (401) having a tow width of 6 mm are spread to have a tow width of 30 mm through the present invention, the prepreg can achieve a coefficient of variation of 10% or less, more preferably 5% or less, and thus, compared to carbon fibers (402) spread using a conventional method, a uniform distribution (density) of the number of carbon fiber filaments can be achieved.

[0079] Meanwhile, the method for manufacturing a carbon fiber prepreg comprises a process of spreading carbon fibers to a desired width and a process of impregnating resin into the carbon fiber tow. As described above, when a prepreg and carbon fiber reinforced plastic are manufactured using uniformly spread carbon fibers, mechanical properties can be improved, and in particular, when molded into a thin prepreg, defects such as local warping or bending can be resolved.

[0080] Hereinafter, the composition and resulting effects of the present invention will be described in more detail through examples and comparative examples. However, these examples are intended to more specifically illustrate the present invention, and the scope of the present invention is not limited to these examples.

[0081] [Example]

[0082] [Examples 1 to 3]

[0083] Carbon fibers (Toray T700 12K product, 6 mm tow width) of carbon fiber creel were passed through a 100 liter tank containing 25°C water, and ultrasonic waves were generated by an ultrasonic generator installed in the tank to spread the carbon fibers. During this process, the tension applied to the carbon fibers within the tank was controlled by nip rolls installed at the front and rear of the tank. The detailed conditions for the carbon fiber spreading process are shown in Table 1.

[0084] Next, the spread carbon fibers were impregnated with a compounded epoxy resin to produce a FAW 25gsm prepreg and then cured. The epoxy resin used here includes 45 wt% of a liquid bisphenol A type epoxy resin (Kukdo Chemical, YD-128), 45 wt% of a solid bisphenol A type epoxy resin (Kukdo Chemical, YD-012), 5 wt% of a dicyandiamide curing agent (Air Products, CG-1400), and 5 wt% of a dichlorophenyl dimethylurea curing accelerator (Lanxess, Diuron).

[0085] [Examples 4 and 5]

[0086] Carbon fiber (T700SC-12000, Toray Advanced Materials) with a tow width of 6 mm was passed through the first tank containing 100 liters of water at 25℃, and 40 kHz ultrasonic waves were generated using an ultrasonic generator installed in the tank to perform the primary spreading of the carbon fiber.

[0087] Next, the carbon fibers, which had been initially spread, were passed through a second tank containing the same medium, generating ultrasonic waves at 200 kHz to perform a second spreading process. During this process, the tension applied to the carbon fibers within the tank was controlled through nip rolls installed at the front and rear ends of the tank. Detailed conditions for the carbon fiber spreading process are shown in Table 1.

[0088] Next, the spread carbon fibers were impregnated with a compounded epoxy resin to produce a prepreg of FAW 25gsm and cured. The epoxy resin used here is the same as in Example 1.

[0089] [Comparative example]

[0090] [Comparative Examples 1 to 4]

[0091] Except that the detailed conditions for the carbon fiber spreading process were as shown in Table 2, spreading was performed in the same manner as in Example 1, and a prepreg was manufactured and cured.

[0092] [Comparative Example 5]

[0093] Carbon fibers (Toray T700 12K product, Tow width 6 mm) of carbon fiber creel were spread by passing them crosswise up and down five spreading bars arranged to have a wrapping angle of 90 degrees at a traveling speed of 10 m / min.

[0094] The physical properties of carbon fibers spread according to Examples 1 to 5 and Comparative Examples 1 to 5 were measured through the following experimental examples, and the results are shown in Tables 1 and 2 below.

[0095] [Experimental Example]

[0096] 1. Measurement of carbon fiber expansion rate

[0097] According to the examples and comparative examples, the final tow width of the spread carbon fiber (Toray T700 12K product, tow width 6 mm) was measured, and then the measured final tow width was divided by the initial tow width (6 mm) to calculate the carbon fiber expansion ratio. In the case of this carbon fiber expansion ratio, a high expansion ratio is required to manufacture a thin prepreg. In particular, a 2.7-fold expansion ratio is required to manufacture a prepreg with FAW 50 gsm, and a 6.7-fold expansion ratio is required to manufacture a prepreg with FAW 20 gsm.

[0098] 2. Carbon fiber filament density variation coefficient

[0099] The prepregs manufactured according to the examples and comparative examples were cut in the vertical direction of the fibers and cross-sections were observed under a microscope. The number of filaments per 100 ㎛ in width (filament density) was measured, and the carbon fiber filament density variation coefficient was calculated from this. Meanwhile, if the carbon fiber filament density variation coefficient exceeds 10%, slight warping occurs in the cured prepreg.

[0100] 3. Evaluation of the occurrence of carbon fiber filament single yarn (furrow)

[0101] In Examples 1 to 5 and Comparative Examples 1 to 4, prepregs were manufactured without operating the circulator during the spreading process, and then cut into 50 cm x 50 cm pieces, and the number of single yarns visually observed on the surface was evaluated based on the following criteria. However, in Comparative Example 5, the manufactured prepreg was cut into 50 cm x 50 cm pieces and then evaluated based on the same criteria as above.

[0102] 1: 1 or less carbon fiber filament single yarn

[0103] 2: More than 2 but not more than 5 carbon fiber filaments

[0104] 3: More than 5 but less than 10 carbon fiber filaments

[0105] 4: More than 10 carbon fiber filaments

[0106] 5: Excessive single-shot generation makes normal prepreg manufacturing impossible (no commercial value)

[0107] ClassificationExample 1Example 2Example 3Example 4Example 5Spreading methodUltrasonic, single tank ultrasonic, single tank ultrasonic, single tank ultrasonic, multi tank ultrasonic, multi tank ultrasonic Frequency (kHz) 40408040 + 20040 + 200Residence time in tank (min) 111Each 0.5Each 0.5Ultrasonic Power (Watt / L) 1020202040Carbon fiber tension (gf / tow) 100±30100±30100±30100±30Carbon fiber spread ratio (fold) 4.55.52.75.56.0Carbon fiber filament density variation coefficient (%) 1081065Carbon fiber filament single yarn (mow) occurrence 23213

[0108] ClassificationComparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5Spreading MethodUltrasonic, Single TankUltrasonic, Single TankUltrasonic, Single TankExisting Bar Spreading (Friction)Ultrasonic Frequency (kHz)272004040-Residence Time in Tank (min)1111-Ultrasonic Power (Watt / L)2020520-Carbon Fiber Tension (gf / tow)100±30100±30100±30300±60-Carbon Fiber Spreading Ratio (fold)6.01.53.51.54.5Carbon Fiber Filament Density Variation Coefficient (%)1020304045Carbon Fiber Filament Single Yarn (Mou) Occurrence52245

[0109] As described in Table 1 above, the carbon fibers spread through the configuration of the present invention and the prepreg manufactured therefrom have a carbon fiber spread ratio of 2.7 times or more, a carbon fiber filament density variation coefficient of 10% or less, and a low occurrence of carbon fiber filament single yarns. In addition, in the case of Examples 4 and 5 using two tanks instead of a single tank, the carbon fiber filament density variation coefficient is lower, and thus it can be confirmed that the distribution (density) of the number of carbon fiber filaments is uniform.

[0110] On the other hand, as can be seen in Table 2 above, when the ultrasonic frequency in the tank is excessively low, as in Comparative Example 1, the occurrence of filament single-stranded particles increases significantly, and when the ultrasonic frequency is excessively high, as in Comparative Example 2, the cavitation intensity decreases, which reduces the cavitation rate.

[0111] In addition, it can be seen that when the ultrasonic power is weak, as in Comparative Example 3, the spread rate decreases and the filament density variation coefficient increases, and when the carbon fiber tension in the tank is excessively high, as in Comparative Example 4, the spread rate decreases and the filament density variation coefficient increases.

[0112] In addition, in Comparative Example 5, unlike Comparative Examples 1 to 4, carbon fibers were spread using conventional bar spreading using friction rather than using ultrasonic waves. It can be seen that when the spreading rate is increased using the conventional bar spreading method, the coefficient of variation of carbon fiber filament density increases and the occurrence of carbon fiber filament single yarns increases significantly.

[0113] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0114] (Explanation of symbols)

[0115] 1: Carbon fiber creel

[0116] 2, 3: Niproll

[0117] 4: Tank

[0118] 4-1: Tank 1

[0119] 4-2: Tank 2

[0120] 5, 6: Ultrasonic generator

[0121] 5-1, 6-1: First ultrasonic generator

[0122] 5-2, 6-2: Second ultrasonic generator

[0123] 7: Circulator

[0124] 7-1: 1st Circulator

[0125] 7-2: Second Circulator

[0126] 8: Drying oven

[0127] 9: Trench Roll

[0128] 10: Impregnation

Claims

1. Carbon fiber krill that continuously supplies carbon fiber into a tank; A tank equipped with a medium that transmits ultrasonic waves through the medium to carbon fibers supplied from the above carbon fiber krill to spread the carbon fibers; An ultrasonic generator that transmits ultrasonic waves into the tank; and An impregnation section for impregnating the above-mentioned spread carbon fiber with resin; A carbon fiber prepreg manufacturing device comprising:

2. In paragraph 1, A carbon fiber prepreg manufacturing device, wherein the frequency of ultrasonic waves generated from the above ultrasonic generator is 30 to 180 kHz.

3. In paragraph 1, The above tank includes a first tank and a second tank, and the ultrasonic generator includes a first ultrasonic generator that transmits ultrasonic waves into the first tank and a second ultrasonic generator that transmits ultrasonic waves into the second tank. A carbon fiber prepreg manufacturing device, wherein the first ultrasonic generator generates ultrasonic waves of 30 to 180 kHz in the first tank to perform primary spreading of carbon fibers supplied to the first tank, and the second ultrasonic generator generates ultrasonic waves of more than 180 kHz and less than 1 MHz in the second tank to perform secondary spreading of the primary spread carbon fibers.

4. In paragraph 1, A carbon fiber prepreg manufacturing device, wherein the output (Power) of the above ultrasonic generator is 8 to 50 watts per 1 L of medium in the above tank.

5. In paragraph 1, A carbon fiber prepreg manufacturing device, wherein the medium is water or an organic solvent at a temperature of 20 to 80°C.

6. In paragraph 5, A carbon fiber prepreg manufacturing device, wherein the organic solvent comprises at least one of a ketone compound and an alcohol compound.

7. In paragraph 1, A carbon fiber prepreg manufacturing device further comprising nip rolls individually positioned at the front and rear ends of the tank to independently control the tension of carbon fibers passing through the tank.

8. In paragraph 7, The above nip roll is a carbon fiber prepreg manufacturing device that controls the tension applied to the carbon fiber within the tank to 50 to 200 gf / tow.

9. In paragraph 1, The above tank is a circulator that circulates a medium to filter carbon fiber single yarns; A carbon fiber prepreg manufacturing device further comprising:

10. In paragraph 1, A drying oven for drying carbon fibers spread in the above tank; A carbon fiber prepreg manufacturing device further comprising:

11. In paragraph 10, A trench roll located at the rear end of the above drying furnace and controlling the width and position of the spread carbon fiber dried in the above drying furnace; A carbon fiber prepreg manufacturing device further comprising:

12. The first step is to continuously supply carbon fibers to a tank containing a medium; A second step of spreading the carbon fibers by applying ultrasonic waves through a medium to the supplied carbon fibers; A third step of passing the spread carbon fiber through a tank; and A fourth step of impregnating the inside of the spread carbon fiber passed through the above tank with resin; A method for manufacturing a carbon fiber prepreg, comprising:

13. In paragraph 12, A method for manufacturing a carbon fiber prepreg, wherein the ultrasonic waves of the second step have a frequency of 30 to 180 kHz.

14. In paragraph 12, The second step includes a first spreading step and a second spreading step in which ultrasonic waves having different frequencies are applied to the supplied carbon fibers to continuously spread the carbon fibers. The ultrasound of the first spreading stage has a frequency of 30 to 180 kHz, A method for manufacturing a carbon fiber prepreg, wherein the ultrasonic waves of the second spreading step have a frequency of more than 180 kHz and less than 1 MHz.

15. In paragraph 12, A method for manufacturing a carbon fiber prepreg, wherein the second step includes a process of filtering carbon fiber single yarn by circulating a medium in a tank through a circulator including a filter.

16. In paragraph 12, A method for manufacturing a carbon fiber prepreg, comprising a process of controlling the tension of carbon fiber to 50 to 200 gf / tow through nip rolls independently driven at the front end of the tank during the first step and at the rear end of the tank after the third step.

17. In paragraph 12, A method for manufacturing a carbon fiber prepreg, which is performed after the third step and further includes a drying step of drying a medium remaining in the carbon fiber through hot air from a drying furnace.

18. In paragraph 17, A method for manufacturing a carbon fiber prepreg, which is performed after the above drying step and further includes a controlling step for controlling the width and arrangement of spread carbon fibers to be suitable for manufacturing a prepreg.

19. In paragraph 12, A method for manufacturing a carbon fiber prepreg, wherein the medium is water or an organic solvent at a temperature of 20 to 80°C.

20. A prepreg manufactured by a method for manufacturing a carbon fiber prepreg according to Article 12.

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