Carbon fiber particles and their manufacturing method

Abstract

The present invention provides carbon fiber particles and a method for producing the same. [Solution] The carbon fiber particles include a plurality of reinforcing fibers and a resin material. The reinforcing fibers include a plurality of carbon fibers and a sizing composition. The sizing composition is a sizing agent that is an acrylate-graft-modified polyurethane resin. The acrylate-graft-modified polyurethane resin is graft-modified using a plurality of modifying monomers, and the modifying monomers are selected from at least one of alkyl group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, and carboxyl group-containing vinyl monomers. The resin material includes a 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 plurality of 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 a carbon fiber reinforced composite material, and more particularly to carbon fiber particles and a method for producing the same. [Background technology]

[0002] In the carbon fiber particle manufacturing process, carbon fibers are impregnated with a sizing agent to form chemical bonds on the surface of the carbon fibers, increasing the adhesion between the carbon fibers and the resin material to form a carbon fiber reinforced polymer (CFRP), which in turn improves the mechanical properties (such as tensile strength) of the carbon fiber reinforced composite material.

[0003] In conventional carbon fiber reinforced composite materials, carbon fibers are often treated with epoxy resin sizing agents. However, when polypropylene (PP) resin is used as the resin material in carbon fiber reinforced composite materials, epoxy resin sizing agents have poor bonding properties with the polypropylene resin, and are unable to effectively improve the adhesion between the carbon fibers and the resin material, resulting in the mechanical properties of the final products (carbon fiber particles, processed products, etc.) not meeting the application requirements.

[0004] Therefore, in view of the fact that the above-mentioned defects can be improved, the inventors have conducted extensive research and applied scientific theory, and as a result have arrived at the present invention as a method that is rational in design and can effectively improve the above-mentioned defects. Summary of the Invention [Problem 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 producing the same in response to the shortcomings of the prior art. [Means for solving the problem]

[0006] An embodiment of the present invention provides a carbon fiber particle including a plurality of reinforcing fibers and a resin material covering the plurality of reinforcing fibers. the plurality of reinforcing fibers include a plurality of carbon fibers and a sizing agent composition covering the plurality of carbon fibers and containing a sizing agent which is a polyurethane resin modified with an acrylate graft, the sizing agent being obtained by graft-modifying a polyurethane resin with a plurality of modifying monomers, the modifying monomer being at least one selected from an alkyl group-containing (meth)acrylate, a hydroxyl group-containing (meth)acrylate, and a carboxyl group-containing vinyl monomer; the resin material includes a polypropylene resin and a modified ethylene propylene copolymer, the modified ethylene propylene copolymer being an ethylene propylene copolymer modified with maleic anhydride, a graft ratio of the maleic anhydride in the modified ethylene propylene copolymer being 0.5% to 5%, a first melt index of the polypropylene resin being 5 g / 10 min to 75 g / 10 min, and a second melt index of the modified ethylene propylene copolymer being 10 g / 10 min to 30 g / 10 min, the first melt index and the second melt index being in accordance with ASTM The results were measured in accordance with D1238 at 190° C. under a load of 1.2 kg, and the weight ratio of the plurality of reinforcing fibers to the resin material (total weight of reinforcing fibers:resin material) was 1:9 to 11:9.

[0007] Preferably, the content of the multiple 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, the content of the hydroxyl group-containing (meth)acrylate is 4 wt % to 9 wt % when the total weight of the plurality of modifying monomers is 100 wt %.

[0009] Preferably, in each of the reinforcing fibers, when 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 graft ratio of the maleic anhydride to the modified ethylene propylene copolymer is 0.6 wt % to 1 wt %.

[0011] Preferably, the resin material includes 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.

[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 carbon fibers have an average fiber length of 6 mm to 25 mm and an average diameter of 5 μm to 8 μm.

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

[0015] An embodiment of the present invention also provides a method for producing carbon fiber particles, which includes 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 composition to form a plurality of reinforcing fibers, the sizing composition containing a sizing agent that is a polyurethane resin modified with an acrylate graft, the sizing agent being obtained by graft-modifying a polyurethane resin with a plurality of modifying monomers, the modifying monomers being at least one selected from alkyl group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, and carboxyl group-containing vinyl monomers; an extrusion process for melting and extruding a resin material containing an ethylene propylene copolymer, wherein the modified ethylene propylene copolymer is an ethylene propylene copolymer modified with maleic anhydride, a graft ratio of the maleic anhydride in the modified ethylene propylene copolymer is 0.5% to 5%, a first melt index of the polypropylene resin is 5 g / 10 min to 75 g / 10 min, a second melt index of the modified ethylene propylene copolymer is 10 g / 10 min to 30 g / 10 min, and the first melt index and the second melt index are in accordance with ASTM D1238 at 190°C under a load of 1.2 kg; 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 pelletization step of cooling and cutting the carbon fiber reinforced composite material to obtain a plurality of carbon fiber particles.

[0016] Preferably, the resin material further includes 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.

[0017] Preferably, the content of the multiple 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, the content of the hydroxyl group-containing (meth)acrylate is 4 wt % to 9 wt % when the total weight of the plurality of modifying monomers is 100 wt %.

[0019] Preferably, in each of the reinforcing fibers, when 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 carbon fibers have an average fiber length of 6 mm to 25 mm and an average diameter of 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 manufacturing method thereof according to the embodiment of the present invention have the technical features that "the plurality of reinforcing fibers include a plurality of carbon fibers and a sizing agent composition that covers the plurality of carbon fibers and contains a sizing agent that is a polyurethane resin modified with an acrylate graft" and "the resin material covers the plurality of reinforcing fibers and includes a polypropylene resin and a modified ethylene propylene copolymer," thereby improving the adhesion between the plurality of reinforcing fibers and the resin material, thereby imparting excellent mechanical properties (such as tensile strength) to the carbon fiber particles. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a three-dimensional schematic diagram showing a carbon fiber particle according to an embodiment of the present invention. [Figure 2] This is a perspective view of Figure 1. [Figure 3] FIG. 2 is a side view of FIG. [Figure 4] FIG. 2 is a cross-sectional view of FIG. 1. [Figure 5] 1 is a flowchart of a method for producing carbon fiber particles according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] In order to better understand the features and technical contents of the present invention, reference is made to the following detailed description and drawings of the present invention. However, the provided description and drawings are for reference and explanation purposes only and do not limit the present invention.

[0025] Hereinafter, the implementation of the "carbon fiber particles and manufacturing method thereof" according to the present invention will be described in detail with reference to certain specific embodiments, and those skilled in the art will be able to understand the advantages and effects of the present invention based on the content disclosed herein. The present invention can be implemented or applied in other different specific embodiments, and various modifications and changes can be made to the details herein based on different perspectives and applications without departing from the concept of the present invention. It should be noted in advance that the accompanying drawings of the present invention are for simple schematic illustrations and are not drawn to actual size. The technical content of the present invention will be described in more detail based on the following embodiments, but the scope of protection of the present invention is not limited by the disclosed content.

[0026] It should be understood that although the present 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 element or one signal from another signal. Furthermore, the term "or" used in the present specification may include any one or more combinations of the associated listed items, depending on the actual situation.

[0027] [Carbon fiber particles] 1 to 4, this embodiment discloses a carbon fiber particle 100 that is a long fiber reinforced thermoplastic composite (LFT). Here, the carbon fiber particle 100 includes a plurality of reinforcing fibers 1 and a resin material 2 that covers the plurality of reinforcing fibers 1.

[0028] 1 and 2, the plurality of reinforcing fibers 1 include a plurality of carbon fibers 11 and a sizing composition 12 that covers the plurality of carbon fibers 11. To further explain, in this embodiment, each of the reinforcing fibers 1 includes one corresponding carbon fiber 11, but the present invention is not limited thereto.

[0029] Here, the carbon fibers 11 have an average fiber length of 6 mm to 25 mm and an average diameter of 5 μm to 8 μm. In this embodiment, the carbon fibers 11 are non-twisted yarns (i.e., no twist count) and may have a cylindrical or elliptical cylindrical 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 of the carbon fibers 11 but does not cover the end surfaces of the carbon fibers 11 (i.e., the upper and lower surfaces of the carbon fibers 11), but the present invention is not limited to this.

[0031] Here, the sizing 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 with a plurality of modifying monomers, and the modifying monomer may be at least one selected from an alkyl group-containing (meth)acrylate, a hydroxyl group-containing (meth)acrylate, and a carboxyl group-containing vinyl monomer.

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

[0033] More specifically, the alkyl group-containing (meth)acrylate is one 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, used 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, and 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, 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%, 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 composition 12 forms chemical bonds on the surfaces of the plurality of carbon fibers 11, thereby promoting bonding between the plurality of reinforcing fibers 1 and the resin material 2. In this way, the adhesion between the plurality of 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 improved. Furthermore, the sizing composition 12 can further increase the wettability of the carbon fibers 11 with the resin material 2, thereby improving the operability of the reinforcing fibers 1 (such as bundling ability and reduced fuzzing) and facilitating subsequent processing.

[0037] In one embodiment of the present invention, the sizing 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. The content of the crosslinking agent is preferably 0.5 wt% to 6 wt%.

[0038] In one embodiment of the present invention, the sizing 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, a vinylsilane coupling agent, a methacryloxysilane coupling agent, an acryloxysilane coupling agent, and an isocyanurate silane coupling agent. The content of the surface modifier is preferably 0.5 wt% to 3 wt%.

[0039] It is worth noting that the introduction of the crosslinking agent into the sizing composition 12 forms additional chemical bonds on the surfaces of the plurality of carbon fibers 11, thereby improving the adhesion between the plurality of reinforcing fibers 1 and the resin material 2. The introduction of the surface modifier into the sizing composition 12 can also change the chemical properties (polarity, hydrophilicity, lipophilicity, etc.) of the surfaces of the carbon fibers 11, thereby improving the bonding (i.e., compatibility) between the carbon fibers 11 and the resin material 2 and improving the adhesive strength between the plurality of 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 the reinforcing fibers 1 to be bonded together. Also, in this embodiment, the end faces of the reinforcing fibers 1 (i.e., the end faces of each of the carbon fibers 11) are exposed from the resin material 2.

[0041] The resin material 2 includes polypropylene (PP) resin, a modified ethylene-propylene copolymer. It should be noted that polypropylene (PP) resin has good compatibility with acrylate-grafted polyurethane resin (i.e., the sizing agent). Therefore, the carbon fibers 11 can significantly improve the adhesion between the reinforcing fibers 1 and the resin material 2 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 (e.g., melt grafting). Here, the melt grafting can be performed, for example, using a single-screw extruder, a twin-screw extruder, or a torque rheometer. A twin-screw extruder is preferred, but the present invention is not limited thereto. More specifically, the grafting ratio of the maleic anhydride to the modified ethylene-propylene copolymer is 0.5% to 5%.

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

[0044] It is worth noting that in this embodiment, the graft ratio of maleic anhydride in the modified ethylene-propylene copolymer is preferably 0.6% to 1%. That is, when the total weight of the modified ethylene-propylene copolymer is taken as 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 graft ratio of maleic anhydride to the above range, compatibility between different resin materials (e.g., the modified ethylene-propylene copolymer and the polypropylene resin) can be effectively improved, and adhesion between the resin material 2 and the plurality of reinforcing fibers 1 can also be improved.

[0045] It is worth noting that the modified ethylene propylene copolymer can be used to reduce the interfacial tension between different materials (e.g., 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 preferably has a first melt index (MI) of 5 g / 10 min to 75 g / 10 min. The modified ethylene-propylene copolymer preferably has a second melt index of 10 g / 10 min to 30 g / 10 min. It should be noted that the melt index in this specification refers to the weight of a polyolefin copolymer passing through a standard opening of a melt flow meter every 10 minutes, and its unit is g / 10 min. The melt index indicates the fluidity in a molten state. The higher the melt index, the smaller the molecular weight and the better the fluidity. Conversely, the higher the molecular weight, the less mobility of the molecular chains, resulting in a smaller melt index and poorer fluidity. In this embodiment, the first melt index and the second melt index are measured at 190°C and a load of 1.2 kg according to ASTM D1238.

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

[0048] In one embodiment of the present invention, the resin material 2 further includes 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, the reinforcing fibers 1 and the resin material 2 can be bonded to form the carbon fiber particles 100, thereby providing good flame retardancy.

[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., a synergistic effect, forming a synergistic flame retardant together) promotes the formation of a surface carbon layer that blocks heat and flame (i.e., functions as a barrier), thereby 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 significantly improved, but the present invention is not limited thereto.

[0050] The relationship between the various components and their combinations in the carbon fiber particle 100 has been explained above. Specifically, in the carbon fiber particle 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 be calculated assuming that the total weight of each carbon fiber particle 100 is 100 parts by weight, but the present invention is not limited to this. 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 finally formed have good mechanical properties (e.g., tensile strength, bending strength, impact strength, etc.).

[0054] [Method of manufacturing carbon fiber particles] As shown in FIGS. 1 to 5, an embodiment of the present invention further provides a method for producing carbon fiber particles, which can produce the above-described carbon fiber particles 100, but the present invention is not limited thereto. Here, as shown in FIG. 4, the method for producing carbon fiber particles includes steps S110 to S140, namely, a pretreatment step S110 (e.g., a step of impregnating carbon fiber with a sizing agent), an extrusion step S120, an impregnation step S130 (e.g., a step of impregnating polypropylene resin), and a pelletization 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. In the production method according to the present invention, other operations may be performed before, between, or after each step, and some of the operations described can be replaced, deleted, or rearranged to carry out the production method in a different manner.

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

[0056] Furthermore, the sizing composition 12 covers each of the carbon fibers 11, thereby improving the overall performance (such as bundling ability and reduced fuzzing) of the plurality of reinforcing fibers 1. At this time, the plurality of reinforcing fibers 1 are separated from each other and are not in contact with each other (i.e., not yet bundled).

[0057] Furthermore, the sizing agent composition 12 includes a sizing agent, and the sizing agent is a polyurethane resin modified with an acrylate graft. Furthermore, the sizing agent is obtained by graft-modifying a polyurethane resin with a plurality of modifying monomers, and the modifying monomers can be selected from at least one of alkyl group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, and carboxyl group-containing vinyl monomers. 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 process S120 can be performed by adjusting the tension and temperature using a wheel-shaped yarn spreading device to sufficiently spread the carbon fiber bundle so that the carbon fibers 11 in the carbon fiber bundle are separated from each other and do not come into contact with each other, but the method of spreading the yarn of the carbon fiber bundle can be adjusted and changed according to design needs, 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 an extruder, heated and melted, and extruded into an 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 includes 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 graft ratio of the maleic anhydride in the modified ethylene-propylene copolymer is 0.5% to 5%.

[0061] More specifically, 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 melt index and the second melt index are results measured at 190°C and a load of 1.2 kg according to ASTM D1238.

[0062] The impregnation step S130 includes forming a carbon fiber reinforced composite material (carbon fiber reinforced polymer, CFRP) by impregnating the resin material 2 into the plurality of reinforcing fibers 1. Furthermore, by introducing the fiber bundle into an 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 one another and not in contact with one another, and the resin material 2 can be uniformly attached to each of the reinforcing fibers 1.

[0063] Thereafter, each of the reinforcing fibers 1 is sufficiently impregnated with the resin material 2, and then passes through (the opening diameter of) the impregnation die head, whereupon it is bundled and output to form the carbon fiber reinforced composite material.

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

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

[0066] It should be further explained that, 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] Due to the above-mentioned configuration, in this embodiment, the components contained in each carbon fiber particle 100 can be calculated assuming that the total weight of each carbon fiber particle 100 is 100 parts by weight, but the present invention is not limited to this. 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] In order to demonstrate the technical effects of the carbon fiber particles and the manufacturing method thereof of the present invention, the following description will be given using experimental data and results, however, the following examples and comparative examples are provided for the purpose of 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 (e.g., a sizing agent containing an acrylate-graft-modified polyurethane resin and, optionally, a crosslinker and a surface modifier) ​​to form multiple reinforcing fibers. A resin material (e.g., a material containing a polypropylene resin and a modified ethylene-propylene copolymer, optionally combined with a first flame retardant and a second flame retardant) was fed into a twin-screw extruder, heated and melted, and extruded through an impregnation die head. Multiple reinforcing fibers were then introduced into the impregnation die head and impregnated with the resin material. Each reinforcing fiber was then sufficiently impregnated with the resin material, passed through the impregnation die head, and bundled and output to form 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-mentioned 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, the carbon fiber plastic particles such as the industrial plastic particles (carbon fiber particles) produced in the above examples and comparative examples were subjected to tests such as 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-off time based on a plate thickness of 3 mm).

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

[0073] [Table 1] TIFF0007791375000003.tif175164

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

[0075] Furthermore, in Examples 3 and 6, a first flame retardant and a second flame retardant were further added to the resin material, and compared to Comparative Examples 1 and 2, the resin material exhibited superior flame retardancy in terms of physical property test results (for example, according to the UL94 combustion test, Examples 3 and 6 had a flame retardancy grade of V0 based on a 1.5 mm plate thickness and a burn-off time of over 1,200 seconds based on a 3 mm plate thickness; whereas the Comparative Example had a flame retardancy grade of HB based on a 1.5 mm plate thickness and a burn-off time of 110 to 192 seconds based on a 3 mm plate thickness). 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 Embodiments] As described above, the carbon fiber particles and the manufacturing method thereof according to the embodiment of the present invention have the technical features that "the plurality of reinforcing fibers include a plurality of carbon fibers and a sizing composition that covers the plurality of carbon fibers and contains a sizing agent that is a polyurethane resin modified with an acrylate graft" and "the resin material covers the plurality of reinforcing fibers and includes a polypropylene resin and a modified ethylene propylene copolymer," thereby improving the adhesion between the plurality of reinforcing fibers and the resin material, thereby imparting excellent mechanical properties (such as tensile strength) to the carbon fiber particles.

[0077] In addition, the carbon fiber particles and the manufacturing method thereof according to the embodiment of the present invention have the technical feature of "comprising the resin material, the first flame retardant, and the second flame retardant," and as a result, the carbon fiber plastic particles (carbon fiber particles) have excellent flame retardancy, achieving flame retardancy grade V0 for a plate thickness of 1.5 mm and a burn-off time of over 1,200 seconds for a plate thickness of 3 mm.

[0078] The above disclosure is merely a preferred embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. Therefore, all equivalent technical modifications made using the specification of the present invention are included in 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 composition 2...Resin material S110....Pretreatment process S120...Extrusion process S130...Impregnation process S140...Pelletizing 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 include a plurality of carbon fibers and a sizing agent composition covering the plurality of carbon fibers and containing a sizing agent which is a polyurethane resin modified with an acrylate graft, the sizing agent being obtained by graft-modifying a polyurethane resin with a plurality of modifying monomers, the modifying monomer being at least one selected from an alkyl group-containing (meth)acrylate, a hydroxyl group-containing (meth)acrylate, and a carboxyl group-containing vinyl monomer; the resin material includes a polypropylene resin and a modified ethylene-propylene copolymer, the modified ethylene-propylene copolymer being an ethylene-propylene copolymer modified with maleic anhydride, a graft ratio of the maleic anhydride to the modified ethylene-propylene copolymer being 0.5% to 5%, a first melt index of the polypropylene resin being 5 g / 10 min to 75 g / 10 min, and a second melt index of the modified ethylene-propylene copolymer being 10 g / 10 min to 30 g / 10 min, and the first melt index and the second melt index being results measured in accordance with ASTM D1238 at 190°C under a load of 1.2 kg; Carbon fiber particles, characterized in that 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.

2. 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. 3. The carbon fiber particles according to claim 2, wherein in each of the reinforcing fibers, when 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. 4. The carbon fiber particles according to claim 3, wherein, in each of the reinforcing fibers, when 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. 2. The carbon fiber particles according to claim 1, wherein the grafting rate of the maleic anhydride with the modified ethylene propylene copolymer is 0.6 wt % to 1 wt %.

6. 2. The carbon fiber particles according to claim 1, wherein the resin material further includes 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. 7. The carbon fiber particles according to claim 6, wherein the content of the first flame retardant is 5 parts by weight to 25 parts by weight, and the content of the second flame retardant is 3 parts by weight to 20 parts by weight.

8. 2. The carbon fiber particles according to claim 1, wherein the carbon fibers have an average fiber length of 6 mm to 25 mm and an average diameter of 5 μm to 8 μm.

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

10. a pretreatment step of separating a plurality of carbon fibers in a carbon fiber bundle from one another and impregnating the plurality of carbon fibers with a sizing composition to form a plurality of reinforcing fibers, the sizing composition containing a sizing agent which is an acrylate-graft-modified polyurethane resin, the sizing agent being obtained by graft-modifying a polyurethane resin with a plurality of modifying monomers, the modifying monomer being at least one selected from an alkyl group-containing (meth)acrylate, a hydroxyl group-containing (meth)acrylate, and a carboxyl group-containing vinyl monomer; an extrusion step of melting and extruding a resin material containing a polypropylene resin and a modified ethylene-propylene copolymer, wherein the modified ethylene-propylene copolymer is an ethylene-propylene copolymer modified with maleic anhydride, a graft ratio of the maleic anhydride to the modified ethylene-propylene copolymer is 0.5% to 5%, a first melt index of the polypropylene resin is 5 g / 10 min to 75 g / 10 min, and a second melt index of the modified ethylene-propylene copolymer is 10 g / 10 min to 30 g / 10 min, and the first melt index and the second melt index are results measured in accordance with ASTM D1238 at 190°C under a load of 1.2 kg; an impregnation step of forming a carbon fiber reinforced composite material by impregnating a plurality of the reinforcing fibers with the resin material, wherein a weight ratio of the plurality of reinforcing fibers to the resin material (total weight of the reinforcing fibers:resin material) is 1:9 to 11:9; a pelletizing step of cooling and cutting the carbon fiber reinforced composite material to obtain a plurality of carbon fiber particles.

11. 11. The method for producing carbon fiber particles according to claim 10, wherein the resin material further includes 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. 12. The 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. 11. The method for producing carbon fiber particles according to claim 10, wherein in each of the reinforcing fibers, when 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%.

14. 14. The method for producing carbon fiber particles according to claim 13, wherein, in each of the reinforcing fibers, when 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%.

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

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

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