Carbon fiber particles and their manufacturing method

Abstract

This invention provides carbon fiber particles and a method for producing the same. [Solution] The carbon fiber particles comprise multiple reinforcing fibers and a resin material. The reinforcing fibers comprise multiple carbon fibers and a sizing agent composition. The sizing agent composition is a polyurethane resin modified with acrylate grafts. The polyurethane resin modified with acrylate grafts is graft-modified using multiple modified monomers, and the modified monomers are selected from at least one of alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer. The resin material comprises polypropylene resin and a modified ethylene propylene copolymer. The modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride. The weight ratio of the multiple reinforcing fibers to the resin material (total weight of reinforcing fibers: resin material) is 1:9 to 11:9.

Description

Technical Field

[0001] The present invention relates to carbon fiber reinforced composite materials, and particularly to carbon fiber particles and a method for manufacturing the same.

Background Art

[0002] In the manufacturing process of carbon fiber particles, by impregnating carbon fibers with a sizing agent, chemical bonds are formed on the surface of the carbon fibers, enhancing the adhesion between the carbon fibers and the resin material to form a carbon fiber reinforced composite material (carbon fiber reinforced polymer, CFRP), and further improving the mechanical properties (such as tensile strength) of the carbon fiber reinforced composite material.

[0003] In the prior art, many carbon fiber reinforced composite materials are obtained by treating carbon fibers with an epoxy resin type sizing agent. However, when using polypropylene (PP) resin as the resin material in carbon fiber reinforced composite materials, the epoxy resin type sizing agent has poor bonding properties with the polypropylene resin, and cannot effectively improve the adhesion between the carbon fibers and the resin material, resulting in the mechanical properties of the final products (such as carbon fiber particles and processed products) not meeting the application requirements.

[0004] Therefore, in view of the above-mentioned defects being improvable, the inventor of the present invention has conducted intensive research and combined theory and practice, and as a result, has arrived at the present invention as a method with a reasonable design and capable of effectively improving the above-mentioned defects.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technical problem to be solved by the present invention is to provide carbon fiber particles and a method for manufacturing the same in view of the deficiencies of the prior art.

Means for Solving the Problems

[0006] Embodiments of the present invention provide carbon fiber particles comprising a plurality of reinforcing fibers and a resin material covering the plurality of reinforcing fibers. The plurality of reinforcing fibers comprises a plurality of carbon fibers and a sizing agent composition containing a sizing agent which covers the plurality of carbon fibers and is a polyurethane resin modified with acrylate grafts, wherein the sizing agent is obtained by graft-modifying a polyurethane resin using a plurality of modified monomers, wherein the modified monomer is at least one selected from alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer, the resin material comprises a polypropylene resin and a modified ethylene propylene copolymer, wherein the modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride, the graft rate of maleic anhydride in the modified ethylene propylene copolymer is 0.5% to 5%, the first melt index of the polypropylene resin is 5 g / 10 min to 75 g / 10 min, and the second melt index of the modified ethylene propylene copolymer is 10 g / 10 min to 30 g / 10 min, and the first and second melt indices are defined in ASTM The results were measured at 190°C and under a load of 1.2 kg according to D1238, and the weight ratio of the multiple reinforcing fibers to the resin material (total weight of reinforcing fibers: resin material) was between 1:9 and 11:9.

[0007] Preferably, the content of the plurality of reinforcing fibers is 1 to 60 parts by weight, the content of the polypropylene resin is 10 to 90 parts by weight, and the content of the modified ethylene propylene copolymer is 2 to 25 parts by weight.

[0008] Preferably, in each of the reinforcing fibers, if the total weight of the multiple modified monomers is 100 wt%, the content of the hydroxyl group-containing (meth)acrylate is 4 wt% to 9 wt%.

[0009] Preferably, in each of the reinforcing fibers, if the total weight of the multiple modified monomers is 100 wt%, the content of the alkyl group-containing (meth)acrylate is 90 wt% to 95 wt%, and the content of the carboxyl group-containing vinyl monomer is 1 wt% to 5 wt%.

[0010] Preferably, the grafting rate of maleic anhydride in the modified ethylene propylene copolymer is 0.6 wt% to 1 wt%.

[0011] Preferably, the resin material comprises a first flame retardant and a second flame retardant, wherein the first flame retardant is at least one selected from piperazine pyrophosphate, piperazine polyphosphate, and 2-methylpiperazine monophosphate, and the second flame retardant is at least one selected from melamine phosphate and melamine pyrophosphate.

[0012] Preferably, the content of the first flame retardant is 5 to 25 parts by weight, and the content of the second flame retardant is 3 to 20 parts by weight.

[0013] Preferably, the average fiber length of the carbon fibers is 6 mm to 25 mm, and the average diameter of the carbon fibers is 5 μm to 8 μm.

[0014] Preferably, the number-average molecular weight of the polyurethane resin is 8,000 to 65,000.

[0015] Embodiments of the present invention also provide a method for producing carbon fiber particles. The method for producing carbon fiber particles is a pretreatment step of separating a plurality of carbon fibers in a carbon fiber bundle from each other and impregnating the plurality of carbon fibers with a sizing agent composition to form a plurality of reinforcing fibers, wherein the sizing agent composition contains a sizing agent which is a polyurethane resin modified with acrylate grafts, and the sizing agent is obtained by graft-modifying a polyurethane resin using a plurality of modified monomers, wherein the modified monomer is at least one selected from alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer, and a polypropylene resin and modified ethyl An extrusion process in which a resin material containing a ethylenepropylene copolymer is melted and extruded, wherein the modified ethylenepropylene copolymer is an ethylenepropylene copolymer modified with maleic anhydride, the graft rate of maleic anhydride in the modified ethylenepropylene copolymer is 0.5% to 5%, the first melt index of the polypropylene resin is 5 g / 10 min to 75 g / 10 min, the second melt index of the modified ethylenepropylene copolymer is 10 g / 10 min to 30 g / 10 min, and the first and second melt indices are defined in ASTM The process includes: a step of measuring the result at 190°C and a load of 1.2 kg according to D1238; an impregnation step of forming a carbon fiber reinforced composite material by impregnating a plurality of the reinforcing fibers with the resin material, wherein the weight ratio of the plurality of reinforcing fibers to the resin material (total weight of reinforcing fibers: resin material) is 1:9 to 11:9; and a pelletizing step of obtaining a plurality of carbon fiber particles by cooling and cutting the carbon fiber reinforced composite material.

[0016] Preferably, the resin material further comprises a first flame retardant and a second flame retardant, wherein the first flame retardant is at least one selected from piperazine pyrophosphate, piperazine polyphosphate, and 2-methylpiperazine monophosphate, and the second flame retardant is at least one selected from melamine phosphate and melamine pyrophosphate.

[0017] Preferably, the content of the plurality of reinforcing fibers is 1 to 60 parts by weight, the content of the polypropylene resin is 10 to 90 parts by weight, the content of the modified ethylene propylene copolymer is 2 to 25 parts by weight, the content of the first flame retardant is 5 to 25 parts by weight, and the content of the second flame retardant is 3 to 20 parts by weight.

[0018] Preferably, in each of the reinforcing fibers, if the total weight of the multiple modified monomers is 100 wt%, the content of the hydroxyl group-containing (meth)acrylate is 4 wt% to 9 wt%.

[0019] Preferably, in each of the reinforcing fibers, if the total weight of the multiple modified monomers is 100 wt%, the content of the alkyl group-containing (meth)acrylate is 90 wt% to 95 wt%, and the content of the carboxyl group-containing vinyl monomer is 1 wt% to 5 wt%.

[0020] Preferably, the average fiber length of the carbon fibers is 6 mm to 25 mm, and the average diameter of the carbon fibers is 5 μm to 8 μm.

[0021] Preferably, the number-average molecular weight of the polyurethane resin is 8,000 to 65,000. [Effects of the Invention]

[0022] As described above, the carbon fiber particles and the method for producing the same according to the embodiment of the present invention provide the carbon fiber particles with excellent mechanical properties (such as tensile strength) by improving the adhesion between the multiple reinforcing fibers and the resin material through technical features such as "the multiple reinforcing fibers comprise multiple carbon fibers and a sizing agent composition containing a sizing agent which is a polyurethane resin modified with an acrylate graft that covers the multiple carbon fibers" and "the resin material comprises a polypropylene resin and a modified ethylene propylene copolymer that covers the multiple reinforcing fibers". [Brief explanation of the drawing]

[0023] [Figure 1] It is a three-dimensional schematic view showing carbon fiber particles according to an embodiment of the present invention. [Figure 2] It is a perspective view of FIG. 1. [Figure 3] It is a side view of FIG. 1. [Figure 4] It is a cross-sectional view of FIG. 1. [Figure 5] It is a flowchart of a method for manufacturing carbon fiber particles according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0024] For a better understanding of the features and technical content of the present invention, reference is made to the following detailed description and drawings related to the present invention. However, the provided description and drawings are for reference and explanation purposes only, and the present invention is not limited thereby.

[0025] Hereinafter, the implementation mode of "carbon fiber particles and a method for manufacturing the same" according to the present invention will be described according to a predetermined specific embodiment, and those skilled in the art can understand the advantages and effects of the present invention based on the content disclosed in this specification. The present invention can be implemented or applied by other different specific embodiments, and for each detail in this specification, various modifications and changes can be made based on different viewpoints and uses without departing from the concept of the present invention. It is pre-explained that the attached drawings of the present invention are simple schematic explanations and are not drawn based on actual sizes. The technical content related to the present invention will be described in more detail based on the following embodiments, but the protection scope of the present invention is not limited by the disclosed content.

[0026] It should be understood that while this specification may use terms such as “first,” “second,” and “third” to describe various elements or signals, these elements or signals are not limited by these terms. These terms are primarily used to distinguish one element from another, or one signal from another. Furthermore, the term “or” as used herein may, depending on the context, include any one or more of the items listed in relation to the subject.

[0027] [Carbon fiber particles] As shown in Figures 1 to 4, this embodiment discloses carbon fiber particles 100, which are a long fiber reinforced thermoplastic composite (LFT). Here, the carbon fiber particles 100 include a plurality of reinforcing fibers 1 and a resin material 2 that covers the plurality of reinforcing fibers 1.

[0028] As shown in Figures 1 and 2, the plurality of reinforcing fibers 1 comprise a plurality of carbon fibers 11 and a sizing agent composition 12 covering the plurality of carbon fibers 11. Further explanation: In this embodiment, each of the reinforcing fibers 1 comprises a corresponding single carbon fiber 11, but the present invention is not limited thereto.

[0029] Here, the average fiber length of the carbon fiber 11 is 6 mm to 25 mm, and the average diameter of the carbon fiber 11 is 5 μm to 8 μm. In this embodiment, the plurality of carbon fibers 11 are untwisted (i.e., have no twists), and the plurality of carbon fibers 11 may be cylindrical or elliptical cylindrical in shape, but the present invention is not limited thereto.

[0030] Furthermore, as shown in Figures 2 to 4, in this embodiment, the sizing agent composition 12 covers the outer surface of each carbon fiber 11 but does not cover the end faces of the carbon fibers 11 (i.e., the upper and lower surfaces of the carbon fibers 11), but the present invention is not limited thereto.

[0031] Here, the sizing agent composition 12 contains a sizing agent, which is a polyurethane resin modified with an acrylate graft. Specifically, the sizing agent is obtained by graft-modifying a polyurethane resin using a plurality of modified monomers, and the modified monomer may be at least one selected from alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer.

[0032] Furthermore, the grafting rate of the alkyl group-containing (meth)acrylate in the polyurethane resin is 1% to 5%, the grafting rate of the hydroxyl group-containing (meth)acrylate in the polyurethane resin is 0% to 5%, and the grafting rate of the carboxyl group-containing vinyl monomer in the polyurethane resin is 0% to 5%. The number-average molecular weight of the polyurethane resin may also be 8,000 to 65,000.

[0033] More specifically, the alkyl group-containing (meth)acrylate is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, methoxyethyl (meth)acrylate, and ethoxymethyl (meth)acrylate, either alone or in combination of two or more.

[0034] The hydroxyl group-containing (meth)acrylate is at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl chloroacrylate, diethylene glycol mono(meth)acrylate, and allyl alcohol. The carboxyl group-containing vinyl monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and maleic anhydride.

[0035] Specifically, assuming the total weight of the multiple modified monomers is 100 wt%, the content of the alkyl group-containing (meth)acrylate is 90 wt% to 95 wt%, the content of the hydroxyl group-containing (meth)acrylate is 4 wt% to 9 wt%, and the content of the carboxyl group-containing vinyl monomer is 1 wt% to 5 wt%.

[0036] With the above-described configuration, the sizing agent composition 12 can form chemical bonds on the surfaces of the multiple carbon fibers 11, thereby promoting the bonding between the multiple reinforcing fibers 1 and the resin material 2. In this way, the adhesion between the multiple reinforcing fibers 1 and the resin material 2 is improved, and the overall performance (e.g., mechanical properties) of the carbon fiber particles 100 is enhanced. Furthermore, since the sizing agent composition 12 can further enhance the wettability of the carbon fibers 11 to the resin material 2, the operability of the reinforcing fibers 1 (such as bundling ability and reduction of fuzzing) is improved, and subsequent processing becomes easier.

[0037] In one embodiment of the present invention, the sizing agent composition 12 may further contain a crosslinking agent, but the present invention is not limited thereto. The crosslinking agent may be at least one selected from the group consisting of melamine crosslinking agents, methylol-modified melamine derivative crosslinking agents, isocyanate crosslinking agents, aziridine crosslinking agents, oxazoline crosslinking agents, and carbodiimide crosslinking agents. Furthermore, the content of the crosslinking agent is preferably 0.5 wt% to 6 wt%.

[0038] In one embodiment of the present invention, the sizing agent composition 12 includes a surface modifier, but the present invention is not limited thereto. The surface modifier may be at least one selected from the group consisting of vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinylsilane coupling agents, methacryloxysilane coupling agents, acryloxysilane coupling agents, and isocyanurate silane coupling agents. Furthermore, the content of the surface modifier is preferably 0.5 wt% to 3 wt%.

[0039] Notably, the sizing agent composition 12, by introducing the crosslinking agent, can form further chemical bonds on the surfaces of the multiple carbon fibers 11, thereby improving the adhesion between the multiple reinforcing fibers 1 and the resin material 2. Furthermore, the sizing agent composition 12 can also change the chemical properties (polarity, hydrophilicity, lipophilicity, etc.) of the surface of the carbon fibers 11 by introducing the surface modifier, thereby improving the bonding (i.e., compatibility) between the carbon fibers 11 and the resin material 2, and improving the adhesion between the multiple reinforcing fibers 1 and the resin material 2.

[0040] Specifically, in this embodiment, the resin material 2 covers (for example, adheres to) the outer surface of each reinforcing fiber 1, allowing multiple reinforcing fibers 1 to adhere to each other. In addition, in this embodiment, the end faces of multiple reinforcing fibers 1 (i.e., the end faces of each carbon fiber 11) are exposed from the resin material 2.

[0041] The resin material 2 comprises a polypropylene (PP) resin and a modified ethylene propylene copolymer. First, it should be noted that the polypropylene (PP) resin has good compatibility with polyurethane resin modified with acrylate grafts (i.e., the sizing agent). Therefore, the adhesion between the multiple carbon fibers 11 and the resin material 2 can be greatly improved via the sizing agent composition 12.

[0042] Furthermore, the modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride (MAH). Specifically, the maleic anhydride can be modified onto the ethylene propylene copolymer by, for example, grafting (such as melt grafting). Here, melt grafting can be carried out using, for example, a single-screw extruder, a twin-screw extruder, or a torque rheometer, and is preferably carried out using a twin-screw extruder, but the present invention is not limited thereto. More specifically, the grafting ratio of the maleic anhydride in the modified ethylene propylene copolymer is 0.5% to 5%.

[0043] In other words, if the total weight of the modified ethylene propylene copolymer is 100 wt%, then the content of maleic anhydride in the modified ethylene propylene copolymer is 0.5 wt% to 5 wt%, and the content of ethylene propylene copolymer in the modified ethylene propylene copolymer is 95 wt% to 99.5 wt%.

[0044] Of particular note is that, in this embodiment, the grafting rate of maleic anhydride in the modified ethylene propylene copolymer is preferably 0.6% to 1%. That is, if the total weight of the modified ethylene propylene copolymer is 100 wt%, the content of maleic anhydride in the modified ethylene propylene copolymer is preferably 0.6 wt% to 1 wt%, and the content of ethylene propylene copolymer in the modified ethylene propylene copolymer is preferably 99 wt% to 99.4 wt%. Furthermore, by limiting the grafting rate of maleic anhydride to the above range, the compatibility with different resin materials (for example, the modified ethylene propylene copolymer and the polypropylene resin) can be effectively improved, and the adhesion between the resin material 2 and the plurality of reinforcing fibers 1 can also be improved.

[0045] Notably, the modified ethylene propylene copolymer can be used to reduce the interfacial tension between different materials (for example, the polypropylene resin and the reinforcing fiber 1), thereby improving the adhesion between the resin material 2 and the reinforcing fiber 1.

[0046] The polypropylene resin has a first melt flow index (MI), which is preferably 5 g / 10 min to 75 g / 10 min. The modified ethylene propylene copolymer has a second melt index, which is preferably 10 g / 10 min to 30 g / 10 min. It should be explained separately that in this specification, the melt index refers to the weight of the polyolefin copolymer passing through the standard opening of a melt flow meter every 10 minutes, and its unit is g / 10 min. The melt index indicates the fluidity in the molten state. The larger the melt index, the smaller the molecular weight and the better the fluidity. Conversely, the larger the molecular weight, the less the molecular chains move, resulting in a smaller melt index and poorer fluidity. In this embodiment, the first and second melt indices are the results of measurements taken at 190°C and a load of 1.2 kg based on ASTM D1238.

[0047] Furthermore, if the first melt index exceeds 75 g / 10 min, the molecular weight of the resin becomes too small, resulting in a decrease in the strength and physical properties of the product. If the first melt index falls below 5 g / 10 min, the processing fluidity is poor, the fiber impregnation effect decreases, and injection molding becomes difficult. Moreover, if the second melt index exceeds 30 g / 10 min, the strength and physical properties decrease, and if the second melt index falls below 10 g / 10 min, the fiber impregnation effect decreases.

[0048] In one embodiment of the present invention, the resin material 2 further comprises a first flame retardant and a second flame retardant, but the present invention is not limited thereto. Here, the first flame retardant is at least one selected from piperazine pyrophosphate, piperazine polyphosphate, and 2-methylpiperazine monophosphate, and the second flame retardant is at least one selected from melamine phosphate and melamine pyrophosphate. Specifically, by introducing the first flame retardant and the second flame retardant into the resin material 2, good flame retardancy can be achieved after bonding the reinforcing fiber 1 and the resin material 2 to form the carbon fiber particles 100.

[0049] For example, in one embodiment of the present invention, the first flame retardant is piperazine pyrophosphate (PAPP), and the second flame retardant is melamine polyphosphate (MPP). Here, the interaction between PAPP and MPP (e.g., synergistic effect, jointly forming a synergistic flame retardant) promotes the formation of a surface carbon layer, which blocks heat and flame (i.e., functions as a barrier), thus further improving fire resistance and thermal stability. Thus, by combining the first flame retardant (e.g., PAPP) and the second flame retardant (e.g., MPP), the fire resistance and thermal stability of the carbon fiber particles 100 are greatly improved, but the present invention is not limited thereto.

[0050] The relationship between the various components in the carbon fiber particles 100 and their combinations has been explained above. Specifically, in the carbon fiber particles 100, the weight ratio of the multiple reinforcing fibers 1 to the resin material 2 (total weight of reinforcing fibers: resin material) is 1:9 to 11:9.

[0051] From another perspective, the components contained in each carbon fiber particle 100 can also be calculated by taking the total weight of each carbon fiber particle 100 as 100 parts by weight, but the present invention is not limited thereto. Here, the content of the reinforcing fiber 1 is 1 to 60 parts by weight, the content of the polypropylene resin is 10 to 90 parts by weight, the content of the modified ethylene propylene copolymer is 2 to 25 parts by weight, the content of the first flame retardant is 5 to 25 parts by weight, and the content of the second flame retardant is 3 to 20 parts by weight.

[0052] Furthermore, the content of the reinforcing fiber 1 is preferably 10 to 55 parts by weight, the content of the polypropylene resin is preferably 10 to 87.5 parts by weight, the content of the modified ethylene propylene copolymer is preferably 2.5 to 10 parts by weight, the content of the first flame retardant is preferably 10 to 20 parts by weight, and the content of the second flame retardant is preferably 5 to 15 parts by weight.

[0053] According to the above configuration, the resin material 2 uniformly covers each of the reinforcing fibers 1, and by stably adhering to each of the reinforcing fibers 1, the carbon fiber particles 100 that are ultimately formed have good mechanical properties (e.g., tensile strength, bending strength, impact strength, etc.).

[0054] [Method for manufacturing carbon fiber particles] As shown in Figures 1 to 5, the present invention further provides a method for manufacturing carbon fiber particles in an embodiment, and while this method can produce the carbon fiber particles 100 described above, the present invention is not limited thereto. Here, as shown in Figure 4, the method for manufacturing carbon fiber particles includes steps S110 to S140, which consist of a pretreatment step S110 (for example, a step of impregnating carbon fibers with a sizing agent), an extrusion step S120, an impregnation step S130 (for example, a step of impregnating with polypropylene resin), and a pelletizing step S140. It should be noted that the order and operation method of each step in this embodiment can be adjusted as needed and is not limited thereto. The manufacturing method according to the present invention may provide other operations before, between, or after each step, and some of the operations described can also be replaced, deleted, or rearranged to carry out the manufacturing method in a different manner.

[0055] The aforementioned pretreatment step S110 includes separating a plurality of carbon fibers 11 in a carbon fiber bundle from each other and impregnating the plurality of carbon fibers 11 with a sizing agent composition 12 to form a plurality of reinforcing fibers 1.

[0056] Furthermore, the sizing agent composition 12 covers each of the carbon fibers 11, thereby improving the overall performance of the multiple reinforcing fibers 1 (such as improved fuzziness and reduced fluffing). At this time, the multiple reinforcing fibers 1 are separated from each other and not in contact with each other (i.e., not yet fuzzed).

[0057] Furthermore, the sizing agent composition 12 contains a sizing agent, which is a polyurethane resin modified with an acrylate graft. The sizing agent is obtained by graft-modifying a polyurethane resin using a plurality of modified monomers, and the modified monomer can be selected from at least one of alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer. In addition, the number-average molecular weight of the polyurethane resin may be 8,000 to 65,000.

[0058] In one embodiment of the present invention, the extrusion step S120 is performed by adjusting the tension and temperature of a wheel-shaped yarn spreading device to sufficiently spread the carbon fiber bundle, thereby separating each of the carbon fibers 11 in the carbon fiber bundle from each other and preventing them from coming into contact with one another. However, the method of spreading the yarn of the carbon fiber bundle can be adjusted and modified as necessary for the design, and the present invention is not limited thereto.

[0059] Next, the resin material 2 is melted and extruded. Specifically, in the extrusion step S120 of this embodiment, the resin material 2 is supplied into the extruder, heated and melted, and extruded into the impregnation die. In one embodiment of the present invention, the extruder may be, for example, a twin-screw extruder, but the present invention is not limited thereto.

[0060] Here, the resin material 2 comprises a polypropylene resin and a modified ethylene propylene copolymer. Furthermore, the modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride, and the grafting rate of maleic anhydride in the modified ethylene propylene copolymer is 0.5% to 5%.

[0061] More specifically, the first melt index of the polypropylene resin was 5 g / 10 min to 75 g / 10 min, and the second melt index of the modified ethylene propylene copolymer was 10 g / 10 min to 30 g / 10 min. The first and second melt indices were measured at 190°C and under a load of 1.2 kg according to ASTM D1238.

[0062] The impregnation step S130 includes forming a carbon fiber reinforced polymer (CFRP) by impregnating a plurality of the reinforcing fibers 1 with the resin material 2. Furthermore, by introducing the fiber bundle into the impregnation die head after the pretreatment step S110, the plurality of reinforcing fibers 1 can be sufficiently impregnated with the resin material 2 while being separated from each other and not in contact with each other, and the resin material 2 can be uniformly attached to each of the reinforcing fibers 1.

[0063] Subsequently, after each of the reinforcing fibers 1 has been sufficiently impregnated with the resin material 2, it passes through the impregnation die head (and its opening diameter) to be focused and output, thereby forming the carbon fiber reinforced composite material.

[0064] Furthermore, the weight ratio of the multiple reinforcing fibers 1 to the resin material 2 (total weight of reinforcing fibers: resin material) is preferably 1:9 to 11:9.

[0065] As shown in Figures 1 to 4, the pelletizing step S140 includes obtaining a plurality of carbon fiber particles 100 by cooling and cutting the carbon fiber reinforced composite material. Specifically, the pelletizing step S140 is a step of cooling the carbon fiber reinforced composite material with a solution (e.g., water), and the temperature of the solution is preferably 30°C to 50°C, but the present invention is not limited thereto.

[0066] As should be explained separately, with reference to Figures 3 and 4, each of the carbon fibers 11 may be exposed from the sizing agent composition 12 and the resin material 2, but the present invention is not limited thereto.

[0067] With the configuration described above, in this embodiment, the components contained in each carbon fiber particle 100 can be calculated by taking the total weight of each carbon fiber particle 100 as 100 parts by weight, but the present invention is not limited thereto. Here, the content of the reinforcing fiber 1 is 1 to 60 parts by weight, the content of the polypropylene resin is 10 to 90 parts by weight, the content of the modified ethylene propylene copolymer is 2 to 25 parts by weight, the content of the first flame retardant is 5 to 25 parts by weight, and the content of the second flame retardant is 3 to 20 parts by weight.

[0068] [Experimental data and results] To demonstrate the technical effectiveness of the carbon fiber particles and their manufacturing method according to this invention, experimental data and results will be used to explain them below. However, the examples and comparative examples described below are for understanding the present invention, and the scope of protection of the present invention is not limited to these examples.

[0069] Examples 1 to 8: First, multiple carbon fibers were impregnated with a sizing agent composition (for example, a sizing agent containing polyurethane resin modified with acrylate grafts, and optionally a crosslinking agent and a surface modifier) ​​to form multiple reinforcing fibers. A resin material (for example, containing polypropylene resin and modified ethylene propylene copolymer, optionally combined with a first flame retardant and a second flame retardant) was supplied into a twin-screw extruder, heated and melted, and extruded into an impregnation die head. Multiple reinforcing fibers were then introduced into the impregnation die head to be impregnated with the resin material. After that, each of the reinforcing fibers was sufficiently impregnated with the resin material, passed through the impregnation die head, was bundled and output, and formed a carbon fiber reinforced composite material. Finally, the carbon fiber reinforced composite material was cooled and cut to obtain multiple carbon fiber particles. In the examples, piperazine pyrophosphate (PAPP) was used as the first flame retardant, and melamine polyphosphate (MPP) was used as the second flame retardant.

[0070] Comparative Examples 1 and 2: The difference from the above-described examples is that the sizing agent compositions of Comparative Examples 1 and 2 both use an epoxy resin type sizing agent to coat multiple carbon fibers.

[0071] Next, carbon fiber plastic particles, such as industrial plastic particles (carbon fiber particles) produced in the above examples and comparative examples, were subjected to tests including collision resistance, tensile strength, bending strength, impact strength, and UL94 combustion test (flame retardancy grade based on a plate thickness of 1.5 mm, burn-through time based on a plate thickness of 3 mm).

[0072] Furthermore, the impact resistance of the industrial plastic particles (i.e., carbon fiber particles) was analyzed based on a 1-minute centrifugation test, the tensile strength was analyzed according to ASTM D-628, the flexural strength was analyzed according to ASTM D-628, and the impact strength (J / m) was analyzed according to ASTM D-256. The relevant measurement results are shown in Table 1.

[0073] [Table 1] TIFF2026121333000003.tif175164

[0074] [Results and Analysis] According to the experimental results described above, Examples 1 to 9 exhibit superior mechanical properties compared to Comparative Examples 1 to 2 in terms of physical property test results for industrial plastic particles (i.e., the carbon fiber particles), including impact resistance (no cracking was observed in Examples 1 to 9, but cracking was observed in Comparative Examples 1 to 2), tensile strength (according to ASTM D-628, Examples were 105 MPa to 255 MPa, while Comparative Examples were 52 MPa to 100 MPa), flexural strength (according to ASTM D-790, Examples were 201 MPa to 345 MPa, while Comparative Examples were 112 MPa to 121 MPa), and impact strength (according to ASTM D-256, Examples were 80 J / m to 146 J / m, while Comparative Examples were 57 J / m to 61 J / m).

[0075] Furthermore, in Examples 3 and 6, the first and second flame retardants were further added to the resin material, resulting in superior flame retardancy in terms of physical properties test results compared to Comparative Examples 1 and 2 (for example, according to the UL94 combustion test, Examples 3 and 6 achieved a flame retardancy grade of V0 based on a plate thickness of 1.5 mm and a burn-out time of over 1200 seconds based on a plate thickness of 3 mm. The comparative examples had a flame retardancy grade of HB based on a plate thickness of 1.5 mm and burn-out times of 110 to 192 seconds based on a plate thickness of 3 mm). Therefore, the carbon fiber particles according to the embodiments of the present invention can be used more widely in fields such as automobiles.

[0076] [Advantageous effects of the embodiment] As described above, the carbon fiber particles and the method for producing the same according to the embodiment of the present invention have technical features such as "the plurality of reinforcing fibers comprises a plurality of carbon fibers and a sizing agent composition containing a sizing agent which is a polyurethane resin modified with acrylate grafts that covers the plurality of carbon fibers" and "the resin material covers the plurality of reinforcing fibers and comprises a polypropylene resin and a modified ethylene propylene copolymer," thereby improving the adhesion between the plurality of reinforcing fibers and the resin material and giving the carbon fiber particles excellent mechanical properties (such as tensile strength).

[0077] Furthermore, the carbon fiber particles and their manufacturing method according to the embodiment of the present invention have technical features such as "containing the resin material, the first flame retardant, and the second flame retardant," which allows the carbon fiber plastic particles (carbon fiber particles) to have excellent flame retardant effects, achieving a flame retardancy grade of V0 at a plate thickness of 1.5 mm and a burn time of over 1200 seconds at a plate thickness of 3 mm.

[0078] The information disclosed above represents only preferred and feasible embodiments of the present invention, and the claims of the present invention are not limited thereto. Therefore, all equivalent technical modifications made using the specification of the present invention are included within the scope of the claims of the present invention. [Explanation of symbols]

[0079] 100...Carbon fiber particles 1...Reinforced fiber 11...Carbon fiber 12... Sizing agent composition 2... Resin materials S110...Pre-treatment process S120...Extrusion process S130...Impregnation process S140...Pelletization process

Claims

1. Carbon fiber particles comprising a plurality of reinforcing fibers and a resin material covering the plurality of reinforcing fibers, The plurality of reinforcing fibers comprises a plurality of carbon fibers and a sizing agent composition containing a sizing agent which is a polyurethane resin modified with an acrylate graft and covers the plurality of carbon fibers, wherein the sizing agent is obtained by graft-modifying a polyurethane resin using a plurality of modified monomers, and the modified monomer is at least one selected from alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer. The resin material comprises a polypropylene resin and a modified ethylene propylene copolymer, wherein the modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride, the grafting rate of maleic anhydride in the modified ethylene propylene copolymer is 0.5% to 5%, the first melt index of the polypropylene resin is 5 g / 10 min to 75 g / 10 min, and the second melt index of the modified ethylene propylene copolymer is 10 g / 10 min to 30 g / 10 min, the first and second melt indices being measured at 190°C and under a load of 1.2 kg according to ASTM D1238. Carbon fiber particles characterized in that the weight ratio of a plurality of the reinforcing fibers to the resin material (total weight of reinforcing fibers: resin material) is 1:9 to 11:

9.

2. The carbon fiber particles according to claim 1, wherein the content of the plurality of reinforcing fibers is 1 to 60 parts by weight, the content of the polypropylene resin is 10 to 90 parts by weight, and the content of the modified ethylene propylene copolymer is 2 to 25 parts by weight.

3. The carbon fiber particle according to claim 2, wherein in each of the reinforcing fibers, if the total weight of the plurality of modified monomers is 100 wt%, the content of the hydroxyl group-containing (meth)acrylate is 4 wt% to 9 wt%.

4. The carbon fiber particle according to claim 3, wherein in each of the reinforcing fibers, if the total weight of the plurality of modified monomers is 100 wt%, the content of the alkyl group-containing (meth)acrylate is 90 wt% to 95 wt%, and the content of the carboxyl group-containing vinyl monomer is 1 wt% to 5 wt%.

5. The carbon fiber particles according to claim 1, wherein the grafting rate of maleic anhydride in the modified ethylene propylene copolymer is 0.6 wt% to 1 wt%.

6. The carbon fiber particles according to claim 1, wherein the resin material further comprises a first flame retardant and a second flame retardant, the first flame retardant being at least one selected from piperazine pyrophosphate, piperazine polyphosphate, and 2-methylpiperazine monophosphate, and the second flame retardant being at least one selected from melamine phosphate and melamine pyrophosphate.

7. The carbon fiber particles according to claim 6, wherein the content of the first flame retardant is 5 to 25 parts by weight, and the content of the second flame retardant is 3 to 20 parts by weight.

8. The carbon fiber particle according to claim 1, wherein the average fiber length of the carbon fiber is 6 mm to 25 mm, and the average diameter of the carbon fiber is 5 μm to 8 μm.

9. The carbon fiber particles according to claim 1, wherein the number average molecular weight of the polyurethane resin is 8,000 to 65,000.

10. A pretreatment step to form multiple reinforcing fibers by separating multiple carbon fibers in a carbon fiber bundle from each other and impregnating the multiple carbon fibers with a sizing agent composition, wherein the sizing agent composition contains a sizing agent which is a polyurethane resin modified with an acrylate graft, and the sizing agent is obtained by graft-modifying a polyurethane resin using multiple modified monomers, and the modified monomer is at least one selected from alkyl group-containing (meth)acrylate, hydroxyl group-containing (meth)acrylate, and carboxyl group-containing vinyl monomer, An extrusion process comprising melting and extruding a resin material containing polypropylene resin and a modified ethylene propylene copolymer, wherein the modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride, the graft rate of maleic anhydride in the modified ethylene propylene copolymer is 0.5% to 5%, the first melt index of the polypropylene resin is 5 g / 10 min to 75 g / 10 min, the second melt index of the modified ethylene propylene copolymer is 10 g / 10 min to 30 g / 10 min, and the first and second melt indices are the results obtained by measuring at 190°C and a load of 1.2 kg according to ASTM D1238. An impregnation step in which a carbon fiber reinforced composite material is formed by impregnating a plurality of the reinforcing fibers with the resin material, wherein the weight ratio of the plurality of reinforcing fibers to the resin material (total weight of reinforcing fibers: resin material) is 1:9 to 11:9, A method for producing carbon fiber particles, characterized by including a pelletizing step of obtaining a plurality of carbon fiber particles by cooling and cutting the carbon fiber reinforced composite material.

11. The method for producing carbon fiber particles according to claim 10, wherein the resin material further comprises a first flame retardant and a second flame retardant, the first flame retardant being at least one selected from piperazine pyrophosphate, piperazine polyphosphate, and 2-methylpiperazine monophosphate, and the second flame retardant being at least one selected from melamine phosphate and melamine pyrophosphate.

12. A method for producing carbon fiber particles according to claim 11, wherein in each of the carbon fiber particles, the content of the plurality of reinforcing fibers is 1 to 60 parts by weight, the content of the polypropylene resin is 10 to 90 parts by weight, the content of the modified ethylene propylene copolymer is 2 to 25 parts by weight, the content of the first flame retardant is 5 to 25 parts by weight, and the content of the second flame retardant is 3 to 20 parts by weight.

13. The method for producing carbon fiber particles according to claim 10, wherein, in each of the reinforcing fibers, when the total weight sum of the plurality of modified monomers is 100 wt%, the content of the hydroxyl group-containing (meth)acrylate is 4 wt% to 9 wt%.

14. The method for producing carbon fiber particles according to claim 13, wherein, in each of the reinforcing fibers, if the total weight sum of the plurality of modified monomers is 100 wt%, the content of the alkyl group-containing (meth)acrylate is 90 wt% to 95 wt%, and the content of the carboxyl group-containing vinyl monomer is 1 wt% to 5 wt%.

15. The method for producing carbon fiber particles according to claim 10, wherein the average fiber length of the carbon fiber is 6 mm to 25 mm, and the average diameter of the carbon fiber is 5 μm to 8 μm.

16. The method for producing carbon fiber particles according to claim 10, wherein the number average molecular weight of the polyurethane resin is 8,000 to 65,000.

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