Composition and method for producing the same, resin pellets, molded articles

Abstract

The objectives are to provide a composition that exhibits excellent processability by extrusion molding and good mechanical strength, and to provide a method for obtaining resin pellets using said composition. [Solution] The problem is solved by a composition using a thermoplastic resin and a carbon fiber bundle, wherein the average fiber length of the carbon fibers contained in the composition is 0.13 to 5.0 mm, and the content of the carbon fiber bundle is 5 to 70% by mass of 100% by mass of the composition.

Description

[Technical Field]

[0001] This invention relates to compositions, methods for producing the same, resin pellets, and molded articles. [Background technology]

[0002] It is generally known that fibrous fillers such as glass fibers and carbon fibers are used to improve the mechanical properties of thermoplastic resins. In particular, polycarbonate resins blended with carbon fibers exhibit high strength. A common method for blending fibrous fillers is to melt-knead the thermoplastic resin and fibers in an extruder. The mixture of molten thermoplastic resin and fibers is extruded into strands, and the resulting pellets are used as molding raw materials for injection molding and other processes.

[0003] Generally, when manufacturing resin pellets by kneading carbon fibers and thermoplastic resins, carbon fiber forms are used that facilitate handling and improve work efficiency. In particular, it is required that the supply of carbon fibers to extruders and other equipment be stable and smooth. Methods for achieving this include cutting continuous carbon fiber bundles obtained by treating them with sizing agents to create so-called chopped carbon fibers, or granulating the cut carbon fibers to form carbon fiber bundles.

[0004] As a method for manufacturing carbon fiber bundles, for example, Patent Document 1 discloses a method in which chopped carbon fibers are mixed with a sizing agent solution or suspension, granulated on an inclined rotating surface, and then dried. This yields carbon fiber bundles with high density and a streamlined shape, making it possible to stably and smoothly supply carbon fibers to extruders and the like.

[0005] On the other hand, when using thermally decomposed, cotton-like recycled carbon fibers as the raw material, the method described in Patent Document 1 cannot obtain sufficient feed efficiency. Patent Document 2 discloses a method for obtaining carbon fiber bundles using recycled carbon fibers, which involves cutting and / or crushing the recycled carbon fibers to a predetermined average length, mixing them with a solution or suspension in a mixer to form aggregates, and drying the aggregates to form spherical carbon fiber bundles.

[0006] Furthermore, Patent Document 3 discloses a method for improving the feed efficiency of carbon fibers, including recycled materials, by extruding and granulating a mixture of carbon fibers and an epoxy resin-based sizing agent to produce cylindrical carbon fiber aggregates. It also states that if the carbon fiber aggregates have a specific cylindrical shape, stable supply to an extruder using a feeder becomes possible. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 10-503812 [Patent Document 2] European Patent Application Publication No. 2902433 [Patent Document 3] Patent No. 7473127 [Overview of the project] [Problems that the invention aims to solve]

[0008] The technology disclosed in Patent Document 3 is a technique for crushing and compressing carbon fibers using an extrusion granulation method, resulting in a mass of short, broken carbon fibers. Therefore, when such carbon fibers are used as raw materials, there is a problem in that the carbon fibers are further broken during processing into pellets and molded articles, impairing the mechanical properties of the molded articles.

[0009] One of the objectives of the present invention is to provide a composition that exhibits excellent processability by extrusion molding and good mechanical strength, and a method for obtaining resin pellets using the composition. [Means for solving the problem]

[0010] The present invention includes the following embodiments. [1]: A composition using a thermoplastic resin and a carbon fiber bundle, The average fiber length of the carbon fibers contained in the above composition is 0.13 to 5.0 mm. The carbon fiber bundle content is 5 to 70% by mass of 100% by mass of the aforementioned composition. composition. [2]: The composition according to [1], wherein the thermoplastic resin is a polycarbonate resin. [3]: The average length of the carbon fiber bundle is 1.0 mm or more and less than 15 mm, The composition according to [1] or [2], wherein the average fiber length of the carbon fibers contained in the carbon fiber bundle is 0.20 to 12 mm. [4]: The carbon fiber bundle contains a sizing agent, The composition according to any one of [1] to [3], wherein the content of the sizing agent is 0.1 to 10 parts by mass per 100 parts by mass of the carbon fiber. [5]: The composition according to any one of [1] to [4], wherein the carbon fiber comprises recycled carbon fiber. [6]: Resin pellets comprising any of the compositions described in [1] to [5]. [7]:[6] A molded body manufactured using resin pellets. [8]: A method for producing a composition, comprising mixing a carbon fiber bundle containing carbon fibers and a sizing agent with a thermoplastic resin to obtain a composition, and extruding the composition using an extruder, The average length of the carbon fiber bundle is 1.0 mm or more and less than 15 mm. The average fiber length of the carbon fibers contained in the aforementioned carbon fiber bundle is 0.20 to 12 mm. A method for producing the composition, wherein the carbon fiber bundle content is 5 to 70% by mass relative to 100% by mass of the composition. [9]: The manufacturing method according to [8], wherein the extruder is equipped with two or more feeders, and the thermoplastic resin and the carbon fiber bundle are supplied from different feeders.

[10] : The production method according to [8] or [9], wherein the carbon fiber contains recycled carbon fiber.

[11] : The production method according to any one of [8] to

[10] , wherein the bulk density of the carbon fiber bundle is 0.1 to 0.7 g / cm 3 And is the production method according to any one of [8] to

[10] .

[12] : The production method according to any one of [8] to

[11] , wherein the average fiber length of the carbon fiber contained in the composition is 0.13 to 5.0 mm.

[13] : The production method according to any one of [8] to

[12] , wherein the composition is a resin pellet. [Advantages of the Invention]

[0011] According to the present invention, it is possible to provide a composition having excellent processability by extrusion molding and good mechanical strength, and a method for obtaining resin pellets using the composition. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, the present invention will be described in detail. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value, and "A~B" means A or more and B or less.

[0013] [Composition] One embodiment of the present invention relates to a composition. The composition according to the embodiment uses a thermoplastic resin and a carbon fiber bundle, and the average fiber length of the carbon fiber contained in the composition is 0.13 to 5.0 mm. Further, among 100% by mass of the composition, the content of the carbon fiber bundle is 5 to 70% by mass.

[0014] The average fiber length of the carbon fiber contained in the composition is preferably 0.14 mm or more, more preferably 0.15 mm or more, still more preferably 0.18 mm or more, and particularly preferably 0.20 mm or more. When the average fiber length of the carbon fiber contained in the composition is above the above lower limit, a composition having excellent mechanical strength tends to be easily obtained. The upper limit of the average fiber length of the carbon fibers contained in the composition is not particularly limited, but is preferably 4.0 mm or less, more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and even more preferably 1.0 mm or less, and may be 0.50 mm or less. When the average fiber length of the carbon fibers contained in the composition is below the above upper limit, it is easier to obtain a composition that has excellent fluidity and moldability when melted and molded.

[0015] <Carbon fiber bundle> The carbon fiber bundle content in the composition is 5% by mass or more and 70% by mass or less per 100% by mass of the composition, preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and also preferably 60% by mass or less, even more preferably 50% by mass or less. This provides an effect of improving the strength and moldability of the molded article. The preferred lower and upper limits of the carbon fiber bundle can be arbitrarily combined, for example, 10 to 60% by mass is preferred, 15 to 60% by mass is more preferred, and 20 to 50% by mass is even more preferred.

[0016] Examples of carbon fibers used in carbon fiber bundles include PAN-based carbon fibers and pitch-based carbon fibers, with PAN-based carbon fibers being preferred from the viewpoint of mechanical properties. PAN-based carbon fibers are mainly composed of filament fibers made of virtually only carbon, which are produced by making fibers made of polyacrylonitrile resin polymerized with acrylonitrile as the main component infusible and then carbonizing them.

[0017] The carbon fibers included in the carbon fiber bundle may also include recycled carbon fibers. Preferred examples of recycled carbon fibers include carbon fibers recovered from scraps of unidirectional prepregs, carbon fibers recovered from waste CFRP (carbon fiber reinforced polymer) made by curing unidirectional prepregs, carbon fibers recovered from scraps of SMC (sheet molding compound), and carbon fibers recovered from waste CFRP made by curing SMC. For example, by dry distilling the above-mentioned scraps or waste materials at a temperature of preferably 600°C or higher, and then heating them in an oxidizing atmosphere at, for example, 550°C or higher, preferably 600°C or higher, the matrix resin is completely thermally decomposed, and cotton-like recycled carbon fibers are obtained.

[0018] Examples of carbon fiber forms include long fibers, chopped fibers, and milled fibers. The carbon fiber form may be one type or two or more types. Because it offers excellent feed stability and allows for easy control of the average fiber length, it is preferable to granulate carbon fibers using a stirring granulation method and use them as carbon fiber bundles.

[0019] The average length of the carbon fiber bundles is 1.0 mm or more, preferably 2.0 mm or more, and more preferably 3.0 mm or more. If the average length of the carbon fiber bundles is above the lower limit, it tends to be easier to obtain a composition with good mechanical strength. The average length of the carbon fiber bundles is less than 15 mm, preferably 14 mm or less, more preferably 13 mm or less, and even more preferably 12 mm or less. If the average length of the carbon fiber bundles is less than 15 mm, it has excellent processability by extrusion molding. The preferred lower and upper limits of the average length of the carbon fiber bundles can be arbitrarily combined, for example, 1.0 mm or more and less than 15 mm, or 3.0 mm or more and 12 mm or less. The average length of the carbon fiber bundle is measured according to the method described in the examples.

[0020] The average fiber length of the carbon fibers in the carbon fiber bundle is 0.20 mm or more, preferably 0.30 mm or more, more preferably 0.40 mm or more, and even more preferably 0.50 mm or more. If the average fiber length of the carbon fibers is above the lower limit, the carbon fibers will be oriented in the flow direction during molding, improving the mechanical properties of the molded article in the flow direction. In particular, the elastic modulus of the molded article in the flow direction can be increased. The orientation of the carbon fibers can be confirmed by observation with a microscope. It is also possible to quantify the orientation of the carbon fibers by X-ray diffraction. Furthermore, even in molding methods in which the carbon fibers are not oriented, it is conceivable that a longer average fiber length of the carbon fibers will increase the interfacial adhesion strength between the carbon fibers and the resin, thereby improving the mechanical strength. The average fiber length of the carbon fibers is 12 mm or less, preferably 10 mm or less, and more preferably 8.0 mm or less. If the average fiber length of the carbon fibers is below the upper limit, a molded article with excellent moldability and a good appearance can be obtained. The preferred lower and upper limits of the average fiber length of the carbon fibers can be arbitrarily combined, for example, 0.20-12 mm, 0.30-10 mm, 0.40-8.0 mm, or 0.50-8.0 mm. The average fiber length of the carbon fibers is measured according to the method described in the examples.

[0021] <Focusing agent> The carbon fiber bundle may contain a sizing agent (binder) in addition to the carbon fibers. The sizing agent is not particularly limited and examples include acrylate-based sizing agents, polyurethane-based sizing agents, polyester-based sizing agents, and epoxy-based sizing agents. The sizing agent may be used alone or as a mixture of two or more types.

[0022] Examples of acrylate-based stimulants include ethylene glycidyl acrylate-based stimulants and polyester acrylate-based stimulants. Examples of acrylate-based stimulants include ethylene / glycidyl acrylate copolymers. Ethylene / glycidyl acrylate copolymers are copolymers having constituent units derived from ethylene and constituent units derived from glycidyl (meth)acrylate. Ethylene / glycidyl acrylate copolymers may also have constituent units derived from monomers other than ethylene and glycidyl (meth)acrylate. Other monomers include vinyl acetate, methyl acrylate, methyl methacrylate, and ethyl acrylate, for example. The proportion of ethylene-derived structural units in the ethylene / glycidyl acrylate copolymer is preferably 60 to 99% by mass relative to the total structural units.

[0023] The ethylene / glycidyl acrylate copolymer is not particularly limited and includes, for example, ethylene / glycidyl acrylate copolymer, ethylene / glycidyl acrylate / vinyl acetate copolymer, ethylene / glycidyl acrylate / methyl acrylate copolymer, ethylene / glycidyl acrylate / vinyl acetate / methyl acrylate copolymer, ethylene / glycidyl acrylate / methyl methacrylate copolymer, ethylene / glycidyl acrylate / vinyl acetate / methyl methacrylate copolymer, ethylene / glycidyl acrylate / ethyl acrylate copolymer, ethylene / glycidyl acrylate / vinyl acetate / ethyl acrylate copolymer, ethylene / glycidyl methacrylate copolymer, ethylene / glycidyl Examples include dil methacrylate / vinyl acetate copolymer, ethylene / glycidyl methacrylate / methyl acrylate copolymer, ethylene / glycidyl methacrylate / vinyl acetate / methyl acrylate copolymer, ethylene / glycidyl methacrylate / methyl methacrylate copolymer, ethylene / glycidyl methacrylate / vinyl acetate / methyl methacrylate copolymer, ethylene / glycidyl methacrylate / ethyl acrylate copolymer, ethylene / glycidyl methacrylate / vinyl acetate / ethyl acrylate copolymer, ethylene / glycidyl methacrylate / glycidyl methacrylate / vinyl acetate copolymer, and ethylene / glycidyl methacrylate / glycidyl methacrylate / methyl acrylate copolymer. These may be used individually or as a mixture of two or more.

[0024] The ethylene / glycidyl acrylate copolymer preferably includes at least one selected from ethylene / glycidyl acrylate copolymer, ethylene / glycidyl methacrylate copolymer, ethylene / glycidyl methacrylate / methyl acrylate copolymer, and ethylene / glycidyl methacrylate / vinyl acetate copolymer. This improves the interfacial adhesion strength between the carbon fibers and the resin, resulting in a molded article with excellent mechanical properties. Furthermore, these copolymers may have a flexible structure, thereby increasing the impact resistance of the molded article. Moreover, by designing their melting temperature and melt viscosity to be lower than that of the resin, it is possible to suppress fiber breakage in the carbon fiber reinforced pellets and molded articles, thereby maintaining high mechanical properties.

[0025] Examples of polyurethane-based sizing agents include urethane resins, which are commonly used as sizing agents for carbon fiber bundles.

[0026] The content of the sizing agent in the carbon fiber bundle is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, based on 100% by mass of the carbon fiber bundle. If the content of the sizing agent is above the lower limit, the adhesion to the carbon fibers is improved. The content of the sizing agent in the carbon fiber bundle is preferably 10 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 5.0 parts by mass or less, based on 100 parts by mass of carbon fibers. If the content of the sizing agent is below the upper limit, a molded article with excellent balance between mechanical properties and heat resistance (resistance to deformation at high temperatures) can be obtained. The preferred lower and upper limits of the sizing agent content can be arbitrarily combined, for example, 0.1 to 10 parts by mass is preferred, 0.1 to 8.0 parts by mass is more preferred, and 0.3 to 5.0 parts by mass is even more preferred.

[0027] <Thermoplastic resin> Examples of thermoplastic resins include polycarbonate resin, polyester resin, polyester carbonate resin, acrylic resin, cycloolefin polymer, polyoxymethylene, polyamide resin, polyolefin resin, styrene resin, polyetherketone resin, polyphenylene sulfide resin, and copolymers containing one or more monomer-derived structural units of these resins. Polycarbonate resin is preferred as the thermoplastic resin because it yields a higher-strength molded article. The thermoplastic resin may be used alone or in combination of two or more types.

[0028] Examples of polycarbonate resins include aromatic polycarbonate resins, aliphatic polycarbonate resins, and aromatic-aliphatic polycarbonate resins. From the viewpoint of the mechanical properties of the resulting resin pellets and carbon fiber reinforced resin molded articles, aromatic polycarbonate resins are preferred as the polycarbonate resin. One type of polycarbonate resin may be used alone, or two or more types may be used in combination.

[0029] Aromatic polycarbonate resins can be obtained, for example, by reacting an aromatic divalent phenol compound with phosgene or a diester carbonate. Examples of aromatic divalent phenol compounds include 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxy-3,5-diphenyl)butane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, and 1-phenyl-1,1-bis(4-hydroxyphenyl)ethane. These aromatic divalent phenol compounds may be used individually or in combination of two or more. Among the aromatic divalent phenol compounds, 2,2-bis(4-hydroxyphenyl)propane is preferred due to its excellent mechanical properties in the molded article.

[0030] The content of thermoplastic resin in the composition is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, based on the total mass of the composition. If the content of thermoplastic resin is above the lower limit, resin pellets and molded articles with excellent moldability can be obtained. The content of thermoplastic resin in the composition is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less, based on the total mass of the composition. If the content of thermoplastic resin is below the upper limit, the proportion of carbon fibers increases, and resin pellets and molded articles with excellent mechanical properties can be obtained. The preferred lower and upper limits of the thermoplastic resin content can be arbitrarily combined, for example, 30 to 95% by mass is preferred, 40 to 90% by mass is preferred, 40 to 85% by mass is even more preferred, and 50 to 80% by mass is particularly preferred.

[0031] <Other ingredients> The composition according to the embodiment may contain other components besides carbon fiber bundles and thermoplastic resins, as needed, as long as they do not significantly impair the desired physical properties. Other components include, for example, resin additives such as stabilizers, release agents, pigments, dyes, UV absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, and antibacterial agents. These other components may be used individually or in combination of two or more.

[0032] The composition according to the embodiment described above comprises a carbon fiber bundle of a specified average length, which includes carbon fibers having a specified average fiber length, and a thermoplastic resin, wherein the carbon fiber bundle content is controlled to a specific amount. As a result, the composition according to the embodiment can be used to obtain resin pellets and molded articles that have excellent moldability by extrusion molding and excellent mechanical properties.

[0033] [Method for producing the composition] One embodiment of the present invention relates to a method for producing a composition. The method according to the embodiment includes (i) to (ii) below. (i) To obtain a composition by mixing a carbon fiber bundle containing carbon fibers and a sizing agent with a polycarbonate resin. (ii) Extrude the composition using an extruder. However, the average length of the carbon fiber bundle is 1.0 mm or more and less than 15 mm, the average fiber length of the carbon fibers contained in the carbon fiber bundle is 0.20 to 12 mm, and the content of the carbon fiber bundle is 5 to 70% by mass per 100% by mass of the composition.

[0034] The carbon fiber bundle used in the method according to this embodiment can be produced by mixing carbon fibers and a sizing agent. Examples of carbon fibers include the same carbon fibers exemplified in the above-mentioned [Composition], and preferred embodiments are also the same. The carbon fibers may include recycled carbon fibers. Examples of recycled carbon fibers include those exemplified in the [Composition] above, and the preferred embodiments are also the same. The sizing agent is the same as the sizing agent exemplified in the [Composition] section above, and the preferred embodiment is also the same.

[0035] Carbon fiber bundles can be produced, for example, by stirring and granulating short carbon fibers and a sizing agent. Water may be added as needed during stirring and granulation. Short carbon fibers can be obtained, for example, by cutting the carbon fibers at predetermined intervals in the fiber direction using a rotary cutter or the like. By performing agitation granulation, even when carbon fibers include regenerated fibers, the fibers can be aligned while maintaining their length without cutting, and carbon fiber bundles of controlled size can be produced. This allows for a more stable supply of carbon fiber bundles to the extruder.

[0036] The agitator / granulator may be a type equipped only with agitator blades, or it may have a chopper attached. Furthermore, using a jacketed agitator / mixer allows for temperature control of the agitator by circulating a heat transfer medium inside the jacket.

[0037] The resulting carbon fiber bundle is preferably dried to evaporate any contained solvents such as water. This allows the sizing agent to adhere sufficiently to the carbon fibers, making it easy to maintain the shape of the carbon fiber bundle. Drying can be done by natural drying or by using a hot air dryer. Using a hot air dryer is preferable from the viewpoint of strengthening the carbon fiber bundle through fusion of the carbon fibers.

[0038] The carbon fiber bundle is preferably an ellipsoidal bundle. This allows for a more stable supply of the carbon fiber bundle to the extruder. For example, by adjusting the rotational speed of the stirring blades and chopper of a stirring granulator, an ellipsoidal bundle of carbon fiber can be obtained.

[0039] The average length of the carbon fiber bundles can be the same as the average length of the carbon fiber bundles used in the "composition" described above, and the preferred embodiment is the same.

[0040] The average fiber length of the carbon fibers contained in the carbon fiber bundle can be the same as the average fiber length of the carbon fibers contained in the carbon fiber bundle used in the "composition" described above, and the preferred embodiment is also the same. For example, by adjusting the spacing of the cutter blades that cut the carbon fibers to a fixed length, a carbon fiber bundle containing carbon fibers having an average fiber length within the above range can be obtained. In recycled carbon fibers, the fiber length after thermal decomposition can be adjusted by crushing the CFRP before thermal decomposition and passing it through a sieve with an adjusted mesh size. In stirring granulation, the carbon fibers can be kept long by controlling the rotation speed of the stirring blades and choppers to a low level without reducing production efficiency. It is also important not to provide sharp surfaces on the stirring blades and choppers. The average fiber length of the carbon fibers is measured according to the method described in the examples.

[0041] Because the carbon fiber bundles can be supplied to the extruder more stably, the bulk density of the carbon fiber bundles is 0.1 g / cm³. 3 The above is preferable, 0.2 g / cm³ 3 The above is more preferable. Since the carbon fiber bundles can be prevented from clumping together in a block-like manner, the bulk density of the carbon fiber bundles is 0.7 g / cm³.3 The following is preferable: 0.5 g / cm³ 3 The following is more preferable. The preferred lower and upper limits of the bulk density of the carbon fiber bundle can be any combination, for example, 0.1 to 0.7 g / cm³. 3 Preferably, 0.2 to 0.5 g / cm³ 3 This is more preferable. For example, by adjusting the amount, viscosity, and wettability of the liquid used in stirring granulation, a carbon fiber bundle having the bulk density within the aforementioned range can be obtained. It is also important to increase the stirring time as long as it does not reduce production efficiency. It is also important to ensure that the bulk density of the carbon fibers used as raw materials is within the above range. The bulk density of the carbon fiber bundle is measured according to the method described in the examples.

[0042] To ensure a more stable supply of carbon fiber bundles to the extruder, the angle of repose of the carbon fiber bundles is preferably 60° or less, more preferably 50° or less, and even more preferably 40° or less. The lower limit of the angle of repose of the carbon fiber bundles is not particularly limited and may be, for example, 10° or more. For example, by adjusting the amount, viscosity, and wettability of the liquid used in stirring granulation, carbon fiber bundles having an angle of repose within the above range can be obtained. It is also important to increase the stirring time as long as it does not reduce production efficiency. It is also important to ensure that the angle of repose of the carbon fibers used as raw materials is within the above range. The angle of repose of the carbon fiber bundle is measured according to the method described in the examples.

[0043] For example, a carbon fiber bundle and a thermoplastic resin are supplied to an extruder, kneaded in the extruder, and then extruded to produce a composition. The thermoplastic resin is the same as that exemplified in the [Composition] above, and the preferred embodiment is also the same.

[0044] In the production of the composition, for example, the carbon fiber bundle and thermoplastic resin may be dry-blended and then melt-kneaded, or the carbon fiber bundle may be supplied to a molten thermoplastic resin and kneaded. Among these methods, the method of supplying the carbon fiber bundle to a molten thermoplastic resin and kneading is preferred because it can suppress carbon fiber breakage and control the average fiber length, and the carbon fiber dispersibility is excellent.

[0045] In the method according to the embodiment, it is preferable to use an extruder equipped with two or more feeders, and to supply the thermoplastic resin and the carbon fiber bundle from different feeders. For example, an extruder equipped with a main raw material feeder and a side feeder can be used. In this case, thermoplastic resin can be supplied and melted from the main raw material feeder installed upstream of the extruder, and carbon fiber bundles can be supplied and kneaded from the side feeder installed downstream of the extruder. Furthermore, an extruder equipped with three or more feeders may be used. In this case, the thermoplastic resin may be supplied from only one location or from two or more locations. Similarly, the carbon fiber bundle may be supplied from only one location or from two or more locations.

[0046] Examples of extruders include single-screw extruders and twin-screw extruders, with twin-screw extruders being preferred. In the case of a twin-screw extruder, the screw rotation speed of the extruder is preferably 100 rpm or higher from the viewpoint of dispersing the carbon fiber bundle. Furthermore, from the viewpoint of suppressing the breakage of carbon fibers contained in the carbon fiber bundle, the screw rotation speed of the extruder is preferably 500 rpm or lower.

[0047] The extruder screw is preferably equipped with one or more kneading zones before and after the supply of carbon fiber bundles. Specifically, it is preferable to sufficiently melt the thermoplastic resin in the kneading zone before the supply of carbon fiber bundles, and to knead the molten thermoplastic resin and carbon fiber bundles in the kneading zone after the supply of carbon fiber bundles. This suppresses the breakage of carbon fibers contained in the carbon fiber bundles, makes it easier to control the average fiber length, and allows for the production of a composition with excellent carbon fiber dispersibility.

[0048] The temperature at which the thermoplastic resin is melted should be above the glass transition temperature of the thermoplastic resin, and is preferably between 220°C and 320°C. The mixing temperature of the thermoplastic resin and carbon fiber bundle should be above the glass transition temperature of the thermoplastic resin, and preferably between 220°C and 320°C. The temperature at which the thermoplastic resin is brought to a melt state and the temperature at which the thermoplastic resin and carbon fiber bundle are mixed may be the same or different.

[0049] In this embodiment, the average fiber length of the carbon fibers contained in the resulting composition can be the same as the average fiber length of the carbon fibers contained in the "composition" described above, and the same applies to the preferred embodiment.

[0050] [Resin pellets] One embodiment of the present invention relates to a resin pellet. The resin pellet according to the embodiment is a pellet made of the composition according to the above embodiment. The requirements and preferred embodiments for the carbon fiber bundles and thermoplastic resin in the resin pellets are the same as those for the composition. The resin pellets according to this embodiment can be manufactured by cutting strands of an extruded composition at predetermined intervals.

[0051] [Molded body] One embodiment of the present invention relates to a molded article. The molded article according to the embodiment is a molded article using the above-mentioned resin pellets. That is, the molded article according to the embodiment can be manufactured by molding using the above-mentioned resin pellets.

[0052] The average fiber length of the carbon fibers contained in the molded article can be the same as the average fiber length of the carbon fibers contained in the "composition" described above, and the preferred form is also the same.

[0053] The carbon fiber bundle content in the molded article is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, even more preferably 15 to 60% by mass, and particularly preferably 20 to 50% by mass, relative to the total mass of the molded article. When the carbon fiber content is within the above range, a molded article with excellent moldability and good appearance can be obtained. The content of thermoplastic resin in the molded article is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, even more preferably 40 to 85% by mass, and particularly preferably 50 to 80% by mass, based on the total mass of the molded article. If the content of thermoplastic resin is within the above range, a molded article with excellent mechanical properties at high temperatures can be obtained.

[0054] The bending strength of the molded article measured at 23°C is preferably 100 MPa or higher, more preferably 110 MPa or higher, and even more preferably 150 MPa or higher, as this yields a molded article that is less prone to cracking. The upper limit of the bending strength of the molded article measured at 23°C is not particularly limited, but may be, for example, 500 MPa or lower. The bending strength was measured in accordance with ISO 178. The test specimen used for measuring bending strength was a dumbbell-shaped tensile test specimen type A1 as described in ISO 20753. This test specimen can be formed by injection molding.

[0055] The flexural modulus of the molded article measured at 23°C is preferably 8,500 MPa or higher, more preferably 9,000 MPa or higher, even more preferably 10,000 MPa or higher, particularly preferably 11,000 MPa or higher, and most preferably 12,000 MPa or higher, as this allows for thinner walls when designing for rigidity. The upper limit of the flexural modulus of the molded article measured at 23°C is not particularly limited, but may be, for example, 40,000 MPa or lower. The flexural modulus was measured in accordance with ISO 178. The test specimen used for measuring the flexural modulus was a dumbbell-shaped tensile test specimen type A1 as described in ISO 20753. This test specimen can be formed by injection molding.

[0056] The tensile fracture stress of the molded article is preferably 75 MPa or higher, more preferably 80 MPa or higher, even more preferably 100 MPa or higher, particularly preferably 100 MPa or higher, especially preferably 130 MPa or higher, and most preferably 150 MPa or higher. The upper limit of the tensile fracture stress of the molded article is not particularly limited, but may be, for example, 500 MPa or lower. The tensile fracture stress was measured by conducting a tensile test in accordance with ISO 527-1 and ISO 527-2.

[0057] The tensile fracture strain of the molded article is preferably 0.5% or more, more preferably 0.8% or more, and even more preferably 1.0% or more. There is no particular upper limit, but it may be, for example, 50% or less, 20% or less, 10% or less, 5.0% or less, etc. The tensile fracture strain was measured by performing a tensile test in accordance with ISO 527-1 and ISO 527-2.

[0058] The molded article according to this embodiment has excellent bending properties and can therefore be suitably used in mechanical components, electrical and electronic components, automotive parts, and the like. Furthermore, it is particularly suitable for automotive parts due to its excellent bending retention rate.

[0059] [Method for manufacturing molded products] The molded article according to the embodiment can be manufactured by molding the resin pellets described above.

[0060] Methods for molding resin pellets include injection molding, extrusion molding, press molding, blow molding, rotational molding, and additive manufacturing. Among these molding methods, injection molding is preferred due to its superior productivity of molded products. From the viewpoint of suppressing voids, the molding temperature is preferably 220°C to 320°C for injection molding. Furthermore, from the viewpoint of improving the surface appearance of the molded product, the mold temperature is preferably 60°C to 100°C. Furthermore, from the perspective of improving the dimensional accuracy of the molded product, the injection pressure should be 300-2000 kgf / cm². 2 This is preferable. Furthermore, from the viewpoint of improving the surface appearance of the molded product, the mold temperature is preferably 60°C to 150°C.

[0061] The average fiber length of the carbon fibers, the carbon fiber content, and the thermoplastic resin content of the molded article produced by the manufacturing method according to the embodiment are as described above in the section on [resin pellets], and the preferred embodiment is the same. [Examples]

[0062] The present invention will be described in more detail below based on examples, but the present invention is not limited in any way by the following examples.

[0063] [Raw materials] The abbreviations for the raw materials used in this example are shown below. (Thermoplastic resin (A)) • A-1: ​​Polycarbonate resin (product name "XANTAR7022J", manufactured by Mitsubishi Chemical Corporation)

[0064] (Stimulant) • Acrylate-based: Ethylene glycidyl acrylate copolymer (product name "Seporjon G515", manufactured by Sumitomo Seika Co., Ltd., emulsion liquid, solid content 40% by mass) • Polyester acrylate type: Polyester acrylate binder solution with a solid content of 40% by mass. • Polyurethane-based: Polyurethane-based binder solution with a solid content of 40% by mass.

[0065] (Carbon fiber bundle (B)) • B-1: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 6.0 mm produced by thermal decomposition and a polyurethane-based sizing agent. • B-2: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 6.0 mm produced by thermal decomposition and an ethylene glycidyl acrylate-based sizing agent. • B-3: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 0.1 mm produced by thermal decomposition and a polyester acrylate-based sizing agent. • B-4: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 0.5 mm produced by thermal decomposition and a polyester acrylate-based sizing agent. • B-5: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 1.0 mm produced by thermal decomposition and a polyester acrylate-based sizing agent. • B-6: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 1.0 mm produced by thermal decomposition and an ethylene glycidyl acrylate-based sizing agent. • B-7: Carbon fiber bundle obtained by stirring and granulating recycled carbon fibers with a number average fiber length of 6.0 mm produced by thermal decomposition and an ethylene glycidyl acrylate-based sizing agent. • B-8: PAN-based recycled carbon fiber (product name "T8S103CD0R", manufactured by CFRI Co., Ltd.) • B-9: PAN-based recycled carbon fiber (product name "T8S103CD0E", manufactured by CFRI Co., Ltd.)

[0066] [Agitator / mixer] A stirring granulator (product name "Intensive Mixer R08W," manufactured by Nippon Eirich Co., Ltd.) was used to manufacture the carbon fiber bundles.

[0067] [Measurement of the average length of carbon fiber bundles] The average length of carbon fiber bundles was measured as follows: Carbon fiber bundles were placed on a white plate, and images were taken from a vertical direction opposite to the white plate. The resulting images were binarized using the image analysis software ImageJ (Wayne Rasband), and the maximum ferret diameter of the carbon fiber bundles was measured. The average length of the carbon fiber bundles was calculated by averaging the maximum ferret diameters of 60 or more carbon fiber bundles.

[0068] [Measurement of average fiber length of carbon fibers] The average fiber length of carbon fibers in a carbon fiber bundle is calculated by spreading carbon fibers, from which the sizing agent has been removed by thermal decomposition or solvent, onto a flat surface, extracting 300 or more carbon fibers with a length of 50 μm or more, measuring their lengths, and calculating the weighted average fiber length. Alternatively, the fiber length can be calculated by binarizing images captured by microscopic observation using image processing software such as ImageJ. Furthermore, the average fiber length of carbon fibers contained in resin pellets and the average fiber length of carbon fibers contained in molded products can be measured using the same procedure.

[0069] [Measurement of bulk density of carbon fiber] The bulk density of carbon fiber bundles was determined by placing 100 mL of multiple fiber bundles into a φ50 mm container, tapping it 10 times from a height of 3 cm to deposit the fiber aggregates, and then calculating the bulk density from the volume and weight. The measurement was performed in accordance with JIS Z 2512 and JIS R 1628.

[0070] [Measuring the angle of repose of carbon fibers] The angle of repose of a fiber bundle can be determined by dropping a 200g fiber bundle from a height of 100mm onto a horizontally held disk of diameter φ95mm, measuring the height of the piled-up fiber bundle after 10 seconds, and using the formula θ = tan-1(T / R), where R is the radius of the disk and T is the piled-up height.

[0071] The measurement results for each carbon fiber bundle are shown in Table 1.

[0072] [Table 1]

[0073] [Extruder] TEX44αII manufactured by Japan Steel Works was used for the production of resin pellets. For the extruder feeders, a main raw material feeder and a side feeder were installed from upstream. The extruder had two kneading zones: one between the main raw material feeder and the side feeder, and another between the side feeder and the die. The cylinder temperature was set between 60 and 320°C.

[0074] [Examples 1-6, Comparative Examples 1-3] We attempted to manufacture resin pellets by mixing thermoplastic resin A-1 (polycarbonate resin, manufactured by Mitsubishi Chemical Corporation, product name "XANTAR7022J") and carbon fiber bundles at the mixing ratios shown in Table 2. The results are shown in Table 2.

[0075] [Table 2]

[0076] When the average length of the carbon fiber bundles was 15 mm as in Comparative Examples 1 and 2, the extrudability of the composition decreased and pellets could not be obtained efficiently. However, when the average length of the carbon fiber bundles was less than 15 mm as in Comparative Example 3 and each of the Examples, the extrudability improved and pellets could be obtained efficiently. From these results, it can be seen that a composition with good processability can be obtained when the average length of the carbon fiber bundles is less than 15 mm.

[0077] [Injection molding machine] For the production of test pieces, an NEX80V type injection molding machine manufactured by Nissei Plastic Industrial Co., Ltd. was used. The cylinder set temperature was 300 °C and the mold temperature was 100 °C.

[0078] [Production of test pieces] After drying the resin pellets obtained above at 120 °C for 7 hours, injection molding was performed using an injection molding machine to produce ISO multipurpose test pieces (4 mm thick).

[0079] [Flexural test] Using the ISO multipurpose test pieces obtained above, flat test pieces with dimensions of 80 mm × 10 mm × 4 mm thick were produced, and in accordance with ISO178, the flexural strength and flexural modulus of the test pieces were measured. The unit was shown in MPa.

[0080] [Tensile properties] Using the ISO multipurpose test pieces obtained above, in accordance with ISO527-1 and ISO527-2, the tensile fracture stress (unit: MPa) and tensile fracture strain (unit: %) were measured.

[0081] [Charpy impact strength] Using the ISO multipurpose test pieces obtained above, in accordance with ISO179-1 and ISO179-2, the Charpy impact strength (with notch and without notch) at 23 °C was measured. The unit was shown in kJ / m 2 as indicated.

[0082] [Heat deflection temperature under load] Using the ISO multipurpose test specimens obtained above, the temperature of deflection under load was measured in accordance with ISO 75-1 and ISO 75-2 under conditions of 23°C and a load of 1.80 MPa (Method A). The unit is shown in °C.

[0083] Table 3 shows the measurement results of test specimens obtained using the resin pellets of Comparative Example 3 and Examples 1-6.

[0084] [Table 3]

[0085] As shown in Tables 1-3, when carbon fibers with a short average fiber length were used as raw materials, as in Comparative Example 3, good mechanical strength could not be obtained. However, when carbon fibers with an average fiber length of 0.13 mm or more were used, as in Examples 1-6, compositions with good mechanical strength could be obtained.

[0086] As described above, the present invention provides a composition that exhibits excellent processability by extrusion molding and good mechanical strength, and a method for obtaining resin pellets using the composition.

Claims

1. A composition using a thermoplastic resin and a carbon fiber bundle, The average fiber length of the carbon fibers contained in the composition is 0.13 to 5.0 mm. The carbon fiber bundle content is 5 to 70% by mass of 100% by mass of the composition. composition.

2. The composition according to claim 1, wherein the thermoplastic resin is a polycarbonate resin.

3. The average length of the carbon fiber bundle is 1.0 mm or more and less than 15 mm. The composition according to claim 1, wherein the average fiber length of the carbon fibers contained in the carbon fiber bundle is 0.20 to 12 mm.

4. The carbon fiber bundle contains a sizing agent, The composition according to claim 1, wherein the content of the sizing agent is 0.1 to 10 parts by mass per 100 parts by mass of carbon fibers.

5. The composition according to claim 1, wherein the carbon fibers include recycled carbon fibers.

6. A resin pellet comprising the composition according to any one of claims 1 to 5.

7. A molded article manufactured using the resin pellets of claim 6.

8. A method for producing a composition, comprising mixing a carbon fiber bundle containing carbon fibers and a sizing agent with a thermoplastic resin to obtain a composition, and extruding the composition using an extruder, The average length of the carbon fiber bundle is 1.0 mm or more and less than 15 mm. The average fiber length of the carbon fibers contained in the carbon fiber bundle is 0.20 to 12 mm. A method for producing the composition, wherein the carbon fiber bundle content is 5 to 70% by mass relative to 100% by mass of the composition.

9. The manufacturing method according to claim 8, wherein the extruder is equipped with two or more feeders, and the thermoplastic resin and the carbon fiber bundle are supplied from different feeders, respectively.

10. The manufacturing method according to claim 8, wherein the carbon fibers include recycled carbon fibers.

11. The bulk density of the carbon fiber bundle is 0.1 to 0.7 g / cm³. ３ The manufacturing method according to claim 8.

12. The manufacturing method according to claim 8, wherein the average fiber length of the carbon fibers contained in the composition is 0.13 to 5.0 mm.

13. The manufacturing method according to claim 8, wherein the composition is a resin pellet.

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