Pellets, molded articles, and methods for manufacturing pellets

Abstract

Provided are: pellets capable of providing a molded article which comprises a polycarbonate resin and recycled carbon fibers and which has mechanical strength close to that of molded articles containing virgin carbon fibers in the same amount and has excellent flame retardancy; the molded article; and a method for producing the pellets. The pellets are ones formed from a composition comprising 100 parts by mass of a polycarbonate resin, 5-65 parts by mass of recycled carbon fibers obtained by heating a carbon-fiber-reinforced resin, and 0.01-0.30 parts by mass of a metal salt flame retardant.

Description

[Technical Field]

[0001] This invention relates to pellets, molded articles, and methods for manufacturing pellets. In particular, it relates to pellets that effectively utilize recycled carbon fibers. [Background technology]

[0002] Polycarbonate resin is widely used in many fields as a resin with excellent heat resistance, impact resistance, transparency, etc. In particular, polycarbonate resin compositions reinforced with inorganic fillers such as glass fibers and carbon fibers exhibit various excellent properties such as dimensional stability, mechanical strength, heat resistance, and electrical properties, and are therefore widely used in industrial fields such as cameras, office automation equipment, and electrical and electronic components (Patent Document 1). On the other hand, from the perspective of making effective use of limited resources, recycling carbon fiber is being considered. As an example of recycled carbon fiber, the one described in Patent Document 2 is known. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-063812 [Patent Document 2] International Publication No. 2018 / 212016 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, when recycled carbon fibers are blended into polycarbonate resin, the mechanical strength is inferior compared to when newly manufactured carbon fibers, i.e., virgin carbon fibers, are blended. If the mechanical strength of a composition containing polycarbonate resin and recycled carbon fibers can be made close to that of a composition containing virgin carbon fibers, an improvement in the carbon fiber recycling rate can be expected. On the other hand, flame retardancy is sometimes required for polycarbonate resin blended with such recycled carbon fibers. The present invention aims to solve the aforementioned problems and provides pellets, molded articles, and a method for manufacturing pellets that can provide molded articles containing polycarbonate resin and recycled carbon fiber, having mechanical strength close to that of articles containing the same amount of virgin carbon fiber, and exhibiting excellent flame retardancy. [Means for solving the problem]

[0005] Under the above challenges, the inventors conducted research and found that by using a metal salt-based flame retardant, it is possible to effectively suppress the decrease in mechanical strength and achieve excellent flame retardancy even when using recycled carbon fibers, thus completing the present invention. Specifically, the above problem was solved by the following means. <1> A pellet formed from a composition containing 100 parts by mass of polycarbonate resin, 5 to 65 parts by mass of recycled carbon fiber which is a heated product of carbon fiber reinforced resin, and 0.01 to 0.30 parts by mass of a metal salt-based flame retardant. <2> The polycarbonate resin has a terminal hydroxyl group content of 150 to 800 ppm. <1> The pellets described above. <3> The flexural strength measured according to ISO 178 using an ISO multipurpose test specimen molded from the aforementioned pellets is 85% or higher when compared to the flexural strength measured according to ISO 178 using an ISO multipurpose test specimen molded from a composition in which the polycarbonate resin contained in the pellets is replaced with a polycarbonate resin having an equal amount of terminal hydroxyl groups of 140 ppm, and the recycled carbon fibers are replaced with virgin carbon fibers having an equal amount of carbon fibers. <1> or <2> The pellets described above. <4> The aforementioned metal salt-based flame retardant includes an organosulfonic acid metal salt. <1> ~ <3> A pellet as described in one of the following. <5> The polycarbonate resin includes recycled polycarbonate resin. <1> ~ <4> A pellet as described in one of the following. <6> The above polycarbonate resin is further comprising 100 parts by mass of a fluid modifier, and 0.5 to 30 parts by mass of a fluid modifier. <1> ~ <5> A pellet as described in one of the following. <7> Furthermore, the polycarbonate resin contains a total of 0.1 to 10 parts by mass of at least one selected from a mold release agent and carbon black, per 100 parts by mass of the polycarbonate resin. <1> ~ <6> A pellet as described in one of the following. <8> The polycarbonate resin has a terminal hydroxyl group content of 150 to 800 ppm. When the bending strength measured according to ISO 178 using an ISO multipurpose test specimen molded from the aforementioned pellets is compared with the bending strength measured according to ISO 178 using an ISO multipurpose test specimen molded from a composition in which the polycarbonate resin contained in the aforementioned pellets is replaced with a polycarbonate resin having an equal amount of terminal hydroxyl groups of 140 ppm, and the recycled carbon fibers are replaced with virgin carbon fibers having an equal amount of carbon fibers, the retention rate is 85% or higher. The aforementioned metal salt-based flame retardant includes an organic sulfonic acid metal salt. The polycarbonate resin includes recycled polycarbonate resin. The above polycarbonate resin is further comprising 100 parts by mass of a fluid modifier, and 0.5 to 30 parts by mass of a fluid modifier. Furthermore, the pellet according to claim 1 further comprises, with respect to 100 parts by mass of polycarbonate resin, a total of 0.1 to 10 parts by mass of at least one selected from a mold release agent and carbon black. <9> <1> ~ <8> A molded product formed from any one of the pellets described in one of the following. <10> A method for producing pellets, comprising putting 100 parts by mass of polycarbonate resin, 5 to 65 parts by mass of recycled carbon fiber which is a heated product of carbon fiber reinforced resin, and 0.01 to 0.30 parts by mass of a metal salt-based flame retardant into an extruder and melt-kneading them together. [Effects of the Invention]

[0006] The present invention provides pellets, molded articles, and a method for manufacturing pellets that contain polycarbonate resin and recycled carbon fiber, and have mechanical strength close to that of an article containing the same amount of virgin carbon fiber, as well as excellent flame retardancy. [Modes for carrying out the invention]

[0007] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). Note that the following embodiment is illustrative for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, "~" is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In this specification, all physical properties and characteristic values ​​shall be those at 23°C unless otherwise specified. In this specification, ppm means mass ppm. If the measurement methods, etc., described in the standards shown herein differ from year to year, unless otherwise specified, the standards as of January 1, 2021 shall apply.

[0008] The pellets of this embodiment are formed from a composition containing 100 parts by mass of polycarbonate resin, 5 to 65 parts by mass of recycled carbon fiber which is a heated product of carbon fiber reinforced resin, and 0.01 to 0.30 parts by mass of a metal salt-based flame retardant. Molded products formed from these pellets possess mechanical strength comparable to that of products containing the same amount of virgin carbon fiber, and also offer excellent flame retardancy. In particular, despite using recycled carbon fiber, a high flexural strength retention rate can be achieved. Furthermore, remarkably, the impact resistance of the molded products is significantly improved by incorporating a metal salt-based flame retardant. The reason for this is that recycled carbon fibers typically have no sizing agents on their surface, or only very small amounts. Under these circumstances, it is presumed that when a metal salt-based flame retardant is added, the metal salt-based flame retardant functions as a sizing agent, improving the retention of flexural strength and impact resistance. The improvement of these mechanical properties by adding a flame retardant is a remarkable effect. Furthermore, by using polycarbonate resin with a terminal hydroxyl group content of 150-800 ppm, an even higher retention rate of flexural strength was achieved. This is presumed to be because setting the terminal hydroxyl group content of the polycarbonate resin to 150-800 ppm improved the adhesion between the carbon fiber surface and the polycarbonate resin, thereby improving mechanical strength. The details of the pellets in this embodiment will be described below.

[0009] <Polycarbonate resin> The composition used in this embodiment contains a polycarbonate resin. The type of polycarbonate resin is not particularly specified, but usually its main component is an aromatic polycarbonate resin, more preferably a bisphenol-type polycarbonate resin, and even more preferably a bisphenol A-type polycarbonate resin. Here, the main component refers to the component that accounts for 80% by mass or more (preferably 90% by mass or more, more preferably 95% by mass or more) of the polycarbonate resin contained in the composition.

[0010] The polycarbonate resin may be a polycarbonate resin obtained by a melt polymerization method or a polycarbonate resin obtained by an interfacial polymerization method, and it is preferably a polycarbonate resin obtained by a melt polymerization method. Further, it may be a mixture of a polycarbonate resin obtained by a melt polymerization method and a polycarbonate resin obtained by an interfacial polymerization method. More specifically, the polycarbonate resin used in this embodiment is preferably an aromatic polycarbonate resin, and for example, it can be produced by a melt transesterification method using an aromatic dihydroxy compound and a carbonic acid diester as raw materials.

[0011] Examples of the aromatic dihydroxy compound include bis(4-hydroxydiphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 4,4-bis(4-hydroxyphenyl)heptane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4'-dihydroxybiphenyl, 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ketone, and the like. These aromatic dihydroxy compounds can be used alone or in combination of two or more. Among these, 2,2-bis(4-hydroxyphenyl)propane is preferred.

[0012] Examples of the carbonic acid diesters include substituted diphenyl carbonates typified by diphenyl carbonate, ditolyl carbonate, etc., and dialkyl carbonates typified by dimethyl carbonate, diethyl carbonate, di-t-butyl carbonate, etc. These carbonic acid diesters can be used alone or in combination of two or more. Among these, diphenyl carbonate and substituted diphenyl carbonate are preferred. Further, up to 50 mol%, more preferably up to 30 mol% of the above carbonic acid diester may be substituted with a dicarboxylic acid or a dicarboxylic acid ester. Representative dicarboxylic acids or dicarboxylic acid esters include terephthalic acid, isophthalic acid, diphenyl terephthalate, diphenyl isophthalate, etc. When substituted with such a dicarboxylic acid or a dicarboxylic acid ester, a polyester carbonate resin can be obtained.

[0013] These carbonic acid diesters (including the above-substituted dicarboxylic acids or esters of dicarboxylic acids) are usually used in excess with respect to the aromatic dihydroxy compound. That is, they are used in a molar amount within the range of 1.001 to 1.3 times, preferably 1.01 to  1.2 times, that of the aromatic dihydroxy compound.

[0014] The polycarbonate resin used in this embodiment preferably has a terminal hydroxyl group content of 150 to 800 ppm. By using a polycarbonate resin having a terminal hydroxyl group content of 150 to 800 ppm, the adhesion to the surface of recycled carbon fiber can be improved, and the mechanical strength can be maintained higher compared to the case where a polycarbonate resin having a terminal hydroxyl group content of less than 150 ppm is blended. In particular, the flexural strength can be maintained high. The amount of terminal hydroxyl groups is preferably 200 ppm or more, more preferably 250 ppm or more, even more preferably 300 ppm or more, even more preferably 350 ppm or more, even more preferably 400 ppm or more, even more preferably 450 ppm or more, especially more preferably 500 ppm or more, and may be 550 ppm or more. Setting it above the lower limit improves the adhesion between the carbon fiber surface and the polycarbonate resin, speeds up the transesterification reaction rate, makes it easier to obtain a polycarbonate resin with the desired molecular weight, reduces the amount of residual carbonate ester in the polycarbonate resin, and tends to more effectively suppress odor during molding and when the molded product is made. Furthermore, the amount of terminal hydroxyl groups is preferably 750 ppm or less, more preferably 700 ppm or less, even more preferably 650 ppm or less, even more preferably 640 ppm or less, and may be 610 ppm or less. By keeping the value below the aforementioned upper limit, the thermal stability of the polycarbonate resin tends to improve further. The amount of terminal hydroxyl groups is measured according to the example described below. If the composition used in this embodiment contains two or more polycarbonate resins, the amount of terminal hydroxyl groups of the polycarbonate resin mixture is used.

[0015] Details of polycarbonate resins having a terminal hydroxyl group content of 150 to 800 ppm can be found in Japanese Patent Publication No. 2003-026911, which is incorporated herein by reference.

[0016] The polycarbonate resin used in this embodiment (or a mixture of polycarbonate resins if two or more types are included) also has a melt volume rate (MVR) of 1 cm 3 Preferably 10 min or more, 5 cm 3 / 10 min or more is more preferable, 8cm 3 It is even more preferable that it be 10 min or longer, and also 40 cm 3 Preferably 10 min or less, and 30 cm 3It is more preferable that it be less than or equal to 10 min. By setting it to be above the lower limit, in particular, 5 cm 3 Setting the flow rate to 10 min or more tends to result in higher flowability and superior moldability, while setting it below the upper limit tends to maintain high impact resistance and heat resistance. MVR is measured according to JIS K 7210. The viscosity-average molecular weight of the polycarbonate resin (or a mixture of polycarbonate resins if two or more types are included) used in this embodiment is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 14,000 or more, and preferably 50,000 or less. Using a polycarbonate resin with a viscosity-average molecular weight of 5,000 or more tends to improve the mechanical strength of the resulting molded product. Using a polycarbonate resin with a viscosity-average molecular weight of 50,000 or less tends to improve the fluidity of the molten pellets and further improve moldability. The viscosity-average molecular weight of polycarbonate resin is calculated from the solution viscosity [Mv] measured at 25°C using methylene chloride as the solvent.

[0017] The polycarbonate resin used in this embodiment may be recycled polycarbonate resin. By using recycled polycarbonate resin, it becomes possible to provide pellets with reduced environmental impact. Recycled polycarbonate resin can be derived from bottles, discs, pachinko machines, sheets, semiconductor transport containers, etc. It is preferable that the recycled polycarbonate resin is recycled aromatic polycarbonate resin.

[0018] In the composition used in this embodiment, the polycarbonate resin content is preferably 60 to 95% by mass. Furthermore, the polycarbonate resin content in the resin component contained in the composition used in this embodiment is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97% by mass or more, and even more preferably 99% by mass or more. The composition used in this embodiment may contain only one type of polycarbonate resin, or it may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0019] <Recycled carbon fiber> The composition used in this embodiment contains 5 to 65 parts by mass of recycled carbon fiber, which is a heated product of carbon fiber reinforced resin, per 100 parts by mass of polycarbonate resin. By using such recycled carbon fiber together with a metal salt-based flame retardant, it is possible to maintain high mechanical strength compared to compositions that combine virgin carbon fiber with polycarbonate resin. Recycled carbon fiber usually has substantially no treatment agents such as surface treatment agents or consolidators, which can make it difficult to achieve sufficient melt mixing with polycarbonate resin. However, in this embodiment, by using a heated product of carbon fiber reinforced resin as recycled carbon fiber, it is presumed that the carbides, which are residues derived from the resin, act as a treatment agent for the carbon fiber, enabling stable melt mixing with the polycarbonate resin. Here, recycled carbon fiber refers to carbon fiber recovered from, for example, used carbon fiber reinforced polymer (aircraft, vehicles, electrical and electronic equipment, etc.) or from scraps of intermediate carbon fiber reinforced polymer (prepreg) generated during the manufacturing process of carbon fiber reinforced polymer. In contrast, virgin carbon fiber generally refers to new carbon fiber that is not recycled carbon fiber, such as carbon fiber sold commercially.

[0020] In this embodiment, heated carbon fiber reinforced resin is used as recycled carbon fiber. When the carbon fiber reinforced resin is heated, the resin turns into carbides, which are present on the surface of the carbon fibers. The carbon fiber reinforced resin in this embodiment includes carbon fibers and a matrix resin. There are no specific requirements regarding the type of carbon fiber, but PAN-based carbon fiber is preferred. The matrix resin may be a thermosetting resin or a thermoplastic resin. The thermosetting resin may be uncured or cured. Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, cyanate resins, and polyimide resins. Examples of thermoplastic resins include polyamides, polyolefins, polyesters, polycarbonates, acrylic resins, acrylonitrile-butadiene-styrene copolymers, polyetheretherketones, and polyphenylene sulfide. The matrix resin may contain additives as needed. Examples of additives include curing agents, curing aids, internal mold release agents, antioxidants, light stabilizers, UV absorbers, and colorants. The heating temperature for the carbon fiber reinforced resin is not particularly specified as long as it is the temperature at which the matrix resin carbonizes, but 300 to 700°C is preferred, 400 to 700°C is more preferred, and 500 to 700°C is even more preferred. Details regarding recycled carbon fibers, which are heated materials for carbon fiber reinforced resins, can be found in International Publication No. 2018 / 212016, and these contents are incorporated herein by reference.

[0021] The resin residue content in recycled carbon fibers is preferably 5% by mass or more, preferably 10% by mass or more, preferably 20% by mass or less, and more preferably 15% by mass or less.

[0022] As described above, recycled carbon fibers typically have virtually no treatment agents (sizing agents, consolidators, surface treatment agents, etc.) on their surface. "Virtually no" means that the amount of treatment agents is, for example, less than 1.0% by mass of the total amount of recycled carbon fibers, more specifically less than 0.1% by mass, more particularly less than 0.01% by mass, and even more particularly less than 0.001% by mass.

[0023] The number-average fiber diameter of the recycled carbon fibers is more preferably 3 μm or larger, and even more preferably 4 μm or larger. It is also preferably 10 μm or smaller, and more preferably 8 μm or smaller. Having the number-average fiber diameter of the recycled carbon fibers within this range makes it easier to obtain pellets with improved mechanical properties, particularly strength and elastic modulus.

[0024] In the composition used in this embodiment, the content of recycled carbon fibers, which are heated carbon fiber reinforced resins, is 5 parts by mass or more, preferably 8 parts by mass or more, and may be 10 parts by mass or more, 13 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, per 100 parts by mass of polycarbonate resin. Setting it above the lower limit tends to yield a composition with superior mechanical strength. Furthermore, the content of recycled carbon fibers is 65 parts by mass or less, preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and may be 50 parts by mass or less, or 45 parts by mass or less, per 100 parts by mass of polycarbonate resin. Setting it below the upper limit tends to yield a composition with superior mechanical strength and moldability. Furthermore, the composition used in this embodiment preferably contains recycled carbon fibers, which are heated carbon fiber reinforced resins, in a proportion of 5% by mass or more, more preferably 10% by mass, even more preferably 15% by mass or more, more preferably 45% by mass or less, and even more preferably 40% by mass or less, in terms of the actual amount of carbon fibers in the composition. The composition used in this embodiment may contain only one type of recycled carbon fiber, which is a heated carbon fiber reinforced resin, or it may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0025] The composition used in this embodiment preferably contains a total amount of polycarbonate resin (preferably a polycarbonate resin with a terminal hydroxyl group content of 150 to 800 ppm), recycled carbon fiber, and metal salt-based flame retardant that accounts for 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more. The upper limit of the total amount is 100% by mass.

[0026] The composition used in this embodiment may or may not contain virgin carbon fibers. One example of the composition used in this embodiment is one in which virgin carbon fibers are contained in a proportion of 5 to 50% by mass (preferably 5 to 30% by mass) of the recycled carbon fiber content. Another example of the composition used in this embodiment is one in which the virgin carbon fiber content is less than 5% by mass (preferably less than 3% by mass, more preferably less than 1% by mass) of the recycled carbon fiber content.

[0027] <Metal salt-based flame retardants> The composition used in this embodiment contains 0.01 to 0.30 parts by mass of a metal salt-based flame retardant per 100 parts by mass of polycarbonate resin. By including a metal salt-based flame retardant, the mechanical properties of the resulting molded product can be improved. In particular, the retention rate of bending strength and impact resistance can be improved.

[0028] As for metal salt-based flame retardants, organometallic salt-based flame retardants are preferred, and organoalkali metal salt compounds are more preferred. Examples of organometallic salt-based flame retardants include metal sulfonic acid salts, metal carboxylate salts, metal borate salts, and metal phosphate salts, but from the viewpoint of thermal stability, organosulfonic acid metal salts are preferred.

[0029] Examples of metals that make up alkali metal salts include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), with sodium, potassium, and cesium being particularly preferred.

[0030] Examples of preferred alkali metal salts of organic sulfonic acids include alkali metal salts of fluorine-containing aliphatic sulfonic acids and aromatic sulfonic acids. Specific examples of preferred alkali metal salts of fluorine-containing aliphatic sulfonic acids having at least one CF bond in the molecule, such as potassium perfluorobutanesulfonate, lithium perfluorobutanesulfonate, sodium perfluorobutanesulfonate, cesium perfluorobutanesulfonate, potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, sodium trifluoromethanesulfonate, and cesium trifluoromethanesulfonate; dipotassium diphenylsulfon-3,3'-disulfonate, potassium diphenylsulfon-3,3'-disulfonate, sodium benzenesulfonate, and sodium (poly)styrenesulfonate. Examples include alkali metal salts of aromatic sulfonic acids having at least one aromatic group in their molecule, such as sodium p-toluenesulfonate, sodium (branched) dodecylbenzenesulfonate, sodium trichlorobenzenesulfonate, potassium benzenesulfonate, potassium styrenesulfonate, potassium (poly)styrenesulfonate, potassium p-toluenesulfonate, potassium (branched) dodecylbenzenesulfonate, potassium trichlorobenzenesulfonate, cesium benzenesulfonate, cesium (poly)styrenesulfonate, cesium p-toluenesulfonate, cesium (branched) dodecylbenzenesulfonate, and cesium trichlorobenzenesulfonate.

[0031] Among the examples mentioned above, alkali metal salts of fluorine-containing aliphatic sulfonic acids are particularly preferred, and alkali metal salts of perfluoroalkanesulfonic acids are even more preferred. Specifically, potassium perfluorobutanesulfonate and sodium trifluoromethanesulfonate are particularly preferred.

[0032] Examples of alkali metal salts containing fluorine organic sulfonates include DIC Corporation's Megafac F114P, Lanxess Corporation's Biowet C4, and Insight High Technology Corporation's IHT-FR21.

[0033] The content of the metal salt-based flame retardant in the composition used in this embodiment is preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.04 parts by mass or more, and even more preferably 0.05 parts by mass or more, per 100 parts by mass of polycarbonate resin. Setting the content above the lower limit tends to increase the flame retardancy of the resulting molded product and improve the retention rate of mechanical strength. Furthermore, the upper limit of the content of the metal salt-based flame retardant is preferably 0.20 parts by mass or less, and more preferably 0.10 parts by mass or less, per 100 parts by mass of polycarbonate resin. Setting the content below the upper limit tends to further improve the appearance and mechanical strength of the resulting molded product. The composition used in this embodiment may contain only one type of metal salt-based flame retardant, or it may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0034] The pellets of this embodiment may or may not contain flame retardants other than metal salt-based flame retardants. Other flame retardants besides metal salt-based flame retardants include halogen-based flame retardants, phosphorus-based flame retardants, and nitrogen-based flame retardants (such as melamine cyanurate). The pellets of this embodiment preferably contain substantially no flame retardants other than metal salt-based flame retardants. Substantially no means that the content of flame retardants other than metal salt-based flame retardants in the composition is 10% by mass or less of the content of metal salt-based flame retardants, preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less.

[0035] <Drip-preventing agent> The composition used in this embodiment may contain an anti-dripping agent. Including an anti-dripping agent can further improve the flame retardancy of the resulting molded product. As an anti-dripping agent, polytetrafluoroethylene (PTFE) is preferred, as it has fibril-forming ability, readily disperses in polycarbonate resin, and tends to bond resins together to form fibrous materials. Specific examples of polytetrafluoroethylene include, for example, the trade names "Teflon® 6J" or "Teflon® 30J" commercially available from Mitsui DuPont Fluorochemicals, "Polyflon" commercially available from Daikin Chemical Industries, or "Fluon" commercially available from Asahi Glass.

[0036] If the composition used in this embodiment contains an anti-dripping agent, its content is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.08 parts by mass or more, per 100 parts by mass of polycarbonate resin. Setting the content above the lower limit tends to further improve flame retardancy. Furthermore, the upper limit of the anti-dripping agent content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of polycarbonate resin. Setting the content below the upper limit tends to further improve the mechanical strength of the resulting molded product. The composition used in this embodiment may contain only one type of drip-preventing agent, or it may contain two or more types. If it contains two or more types, it is preferable that the total amount is within the above range.

[0037] <Flow modifier> The composition used in this embodiment preferably contains 0.5 to 30 parts by mass of a flow modifier per 100 parts by mass of polycarbonate resin. By including a flow modifier, the fluidity of the polycarbonate resin can be improved while maintaining excellent flexural strength.

[0038] The fluid modifier used in this embodiment can be any known substance, and may be a low molecular weight or oligomer (number average molecular weight less than 2000) or a high molecular weight (number average molecular weight of 2000 or more). In this embodiment, for example, an oligomer with a number average molecular weight of 1000 or more and less than 2000 can be used. The number average molecular weight here is the polystyrene equivalent value measured by GPC (gel permeation chromatography). Specifically, examples include polyester oligomers, polycarbonate oligomers, polycaprolactones, low molecular weight acrylic copolymers, and aliphatic rubber-polyester block copolymers, with polycarbonate oligomers being preferred. The fluid modifier may be described in paragraphs 0050 to 0056 of Japanese Patent No. 4736260 and paragraphs 0059 to 0070 of Japanese Unexamined Patent Publication No. 2011-063812, the contents of which are incorporated herein by reference.

[0039] In the composition used in this embodiment, the content of the fluid modifier is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of polycarbonate resin. Setting it above the lower limit tends to further improve the fluidity of the polycarbonate resin. The content of the fluid modifier is also preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 17 parts by mass or less, and even more preferably 16 parts by mass or less. Setting it below the upper limit tends to further improve the fluidity of the polycarbonate resin without reducing heat resistance and impact resistance. The composition used in this embodiment may contain only one type of fluid modifier, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0040] <Other ingredients> The composition used in this embodiment may contain other components besides those mentioned above. Examples include thermoplastic resins other than polycarbonate resin, dyes, pigments, impact modifiers, antistatic agents, slip agents, antiblocking agents, mold release agents, antifogging agents, natural oils, synthetic oils, waxes, organic fillers, and the like. The total amount of these components may be, for example, 0.1 to 10% by mass of the composition. The composition used in this embodiment is exemplified by containing, for example, 0.1 to 10 parts by mass (preferably 0.5 to 5 parts by mass) of at least one selected from a mold release agent and carbon black, per 100 parts by mass of polycarbonate resin. As for release agents, reference can be given to paragraphs 0054 to 0064 of Japanese Patent Publication No. 2021-031633 and paragraphs 0038 to 0044 of Japanese Patent Publication No. 2019-056035, and this information is incorporated herein by reference. For carbon black, refer to the descriptions in paragraphs 0065-0068 of Japanese Patent Publication No. 2021-031633 and paragraphs 0014-0025 of Japanese Patent Publication No. 2019-056035, which are incorporated herein by reference.

[0041] <Physical properties> It is preferable that the molded article obtained from the pellets of this embodiment has a high bending strength similar to that obtained when virgin carbon fibers are blended with polycarbonate resin. It is preferable that the retention rate is 85% or higher when comparing the bending strength measured according to ISO 178 using an ISO multipurpose test specimen molded from the pellets of this embodiment with the bending strength measured according to ISO 178 using an ISO multipurpose test specimen molded from pellets in which the polycarbonate resin contained in the pellets is replaced with a polycarbonate resin having an equal amount of terminal hydroxyl groups of 140 ppm, and the recycled carbon fibers are replaced with virgin carbon fibers having an equal amount of carbon fibers. The ISO multipurpose test specimen is a flat test specimen with a thickness of 80 mm × 10 mm × 4 mm (for example, a flat test specimen with a thickness of 80 mm × 10 mm × 4 mm cut from an ISO multipurpose test specimen). Furthermore, it is more preferable that the retention rate is 86% or higher, even more preferable that it is 88% or higher, even more preferable that it is 90% or higher, even more preferable that it is 95% or higher, even more preferable that it is 98% or higher, and especially even more preferable that it is over 100%. The upper limit of the above value is practically 110% or less. Such high retention rates are achieved by incorporating metal salt-based flame retardants. These high retention rates are even more effectively achieved by using polycarbonate resins with terminal hydroxyl group content of 150-800 ppm.

[0042] It is preferable that the molded article obtained from the pellets of this embodiment has excellent flame retardancy. Specifically, it is preferable that the pellets of this embodiment are formed into UL test pieces with a thickness of 1.5 mm and that the flame retardancy when subjected to UL94 testing satisfies V-0.

[0043] <Method for manufacturing pellets> The pellets used in this embodiment can be manufactured by a conventional method for manufacturing pellets containing polycarbonate resin. For example, the pellets used in this embodiment are manufactured by a method that includes putting 100 parts by mass of polycarbonate resin (preferably polycarbonate resin with a terminal hydroxyl group content of 150 to 800 ppm), 5 to 65 parts by mass of recycled carbon fiber which is a heated product of carbon fiber reinforced resin, and 0.01 to 0.30 parts by mass of a metal salt-based flame retardant into an extruder and melt-kneading them. Recycled carbon fiber may not have surface treatment agents or consolidators attached to its surface, but in this embodiment, by using a heated product of carbon fiber reinforced resin as the recycled carbon fiber, the resin-derived residue acts as a surface treatment agent, etc., making it possible to melt-knead it into an extruder. Therefore, it can be made into pellets. The components may be pre-mixed and supplied to the extruder all at once, or they may be supplied to the extruder using a feeder, either without pre-mixing them or with only some of them pre-mixed. The extruder may be a single-screw extruder or a twin-screw extruder. Alternatively, some components of the dye or pigment (e.g., carbon black) may be melt-kneaded with the resin components to prepare a masterbatch, and then the remaining components may be added and melt-kneaded to it. Furthermore, it is also preferable to supply the carbon fibers from a side feeder located midway through the extruder cylinder. The heating temperature during melting and kneading can usually be appropriately selected from the range of 250 to 350°C.

[0044] The molded article of this embodiment is formed from the pellets of this embodiment. Because the molded product of this embodiment has good mechanical strength, it can be applied to various uses, such as various storage containers, electrical and electronic equipment components, office automation (OA) equipment components, home appliance components, mechanical mechanism components, and vehicle mechanism components.

[0045] <Method for manufacturing molded products> The method for manufacturing the molded article of this embodiment is not particularly limited, and any molding method commonly used for compositions or pellets containing polycarbonate resin can be arbitrarily employed. Examples include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding using insulated molds, molding using rapidly heated molds, foam molding (including supercritical fluids), insert molding, IMC (in-mold coating) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, blow molding, etc., with injection molding being preferred among them. Details of injection molding can be found in paragraphs 0113 to 0116 of Japanese Patent No. 6183822, which are incorporated herein by reference. [Examples]

[0046] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0047] 1.Raw materials The raw material components used in the following examples and comparative examples are as shown in Tables 1 and 2 below.

[0048] [Table 1]

[0049] [Table 2]

[0050] <Amount of residue> The residue of recycled carbon fibers in Table 2 indicates the amount of carbides in the recycled carbon fibers. In other words, since the recycled carbon fibers used in this embodiment are fired composites of resin (e.g., epoxy resin) and carbon fibers, the recycled carbon fibers contain residue (carbides) derived from the resin (e.g., epoxy resin). The amount of resin residue is calculated from the carbon fiber content of the carbon fiber reinforced resin before heat treatment and obtained from formula (X). The unit is expressed in mass %. [B - (A × C) / (B)] × 100 formula (X) A: Mass of carbon fiber reinforced resin before heat treatment B: Mass of the heat-treated object C: Carbon fiber content of carbon fiber reinforced resin before heat treatment

[0051] <Amount of terminal hydroxyl groups in polycarbonate resin> The amount of terminal hydroxyl groups in polycarbonate resin (PC resin) represents the total amount of terminal hydroxyl groups shown below, and is expressed in ppm as the ratio of the mass of terminal hydroxyl groups to the total mass of polycarbonate resin. The measurement method was the colorimetric determination method using titanium tetrachloride / acetic acid (as described in Macromol. Chem. 88 215 (1965)). [ka] In the above formula, R 5 R is a group selected from halogen atoms, nitro groups, cyano groups, C1-C20 alkyl groups, C2-C20 alkoxycarbonyl groups, C4-C20 cycloalkyl groups, and C6-C20 aryl groups, where r represents an integer from 0 to 2. When r is 2, there are two R 5 These may be the same or different. The wavy lines indicate the bonding positions with the main chain of the polycarbonate resin.

[0052] 2. Examples 1-11 and Comparative Examples 1-7 <Compound> Each raw material listed in Tables 4-7 was weighed to the content (all parts by mass) as indicated in the tables. Using a twin-screw extruder equipped with one vent, the raw materials other than carbon fiber were fed into the extruder from the barrel upstream of the extruder, and the carbon fiber was side-fed. The mixture was kneaded under the conditions of a screw rotation speed of 300 rpm, a discharge rate of 200 kg / hour, and a barrel temperature of 280-310°C. The molten pellets extruded in strand form were rapidly cooled in a water bath and pelletized using a pelletizer to obtain pellets.

[0053] <Forming of test specimens> The obtained pellets were dried at 120°C for 5 hours, and then injection molded using an injection molding machine (Japan Steel Works "J85AD") under the conditions of cylinder temperature 300°C, mold temperature 100°C, and molding cycle of 50 seconds to produce ISO multipurpose test specimens (4 mm thick).

[0054] <Tensile strength, tensile modulus, and tensile strain> Using the ISO multipurpose test specimens obtained above, tensile tests were conducted according to ISO 527-1 and ISO 527-2 to determine the tensile strength, tensile modulus, and tensile strain. Tensile strength and tensile modulus are expressed in units of MPa. Tensile strain is expressed in units of %.

[0055] <Bending strength, retention rate of bending strength, and bending modulus of elasticity> Using the ISO multipurpose test specimens obtained above, flat test specimens measuring 80 mm × 10 mm × 4 mm in thickness were prepared, and the bending strength and bending modulus of elasticity of the specimens were measured according to ISO 178. The retention rate of bending strength was also calculated. The units for bending strength and bending modulus are given in MPa. The unit for the retention rate of bending strength is given in %.

[0056] The retention rates of bending strength are shown as relative values ​​for Comparative Examples 1-4 and Examples 1-6, with the bending strength of Comparative Example 1 set to 100%; for Comparative Example 5, Examples 7 and 8, with the bending strength of Comparative Example 5 set to 100%; and for Comparative Examples 6 and 7, Examples 9-11, with the bending strength of Comparative Example 6 set to 100%.

[0057] <Izod impact strength without notch> Using the ISO multi-purpose test specimens obtained above, the Izod impact strength (without notch) at 23°C was measured in accordance with ISO 179-1 and ISO 179-2. The unit is kJ / m 2 as shown.

[0058] <Flame retardancy> For the pellets obtained above, injection molding was carried out using an injection molding machine ("SE50DUZ" manufactured by Sumitomo Heavy Industries, Ltd.) under the conditions of a resin temperature of 290°C and a mold temperature of 80°C to obtain UL test specimens with a length of 127 mm, a width of 12.7 mm, and a wall thickness of 1.5 mm. The obtained UL test specimens were conditioned in a constant temperature chamber at 23°C and a relative humidity of 50% for 48 hours, and the test was carried out in accordance with the UL94 test (combustion test for plastic materials for parts of equipment) defined by Underwriters Laboratories (UL) of the United States. The UL94 test is a method for evaluating flame retardancy from the afterflame time and dripping property after a burner flame is applied to a vertically held test specimen for 10 seconds. In order to have a flame retardancy of V-0, V-1, and V-2, it is necessary to meet the criteria shown in Table 3 below. Non-conformance means that it does not fall under any of V-0 to V-2.

[0059]

Table 3

[0060] In Comparative Examples 1 to 3, Examples 1 to 4, and 6, the pellets (compositions) are formulated so that the amount of substantial carbon fiber is the same. That is, since the recycled carbon fiber used in the present invention is a heated product of a carbon fiber reinforced resin, the carbon fiber contains a resin-derived residue (resin residue). By adjusting so that the amount of carbon fiber excluding this resin residue is the same, a direct comparison of mechanical strength becomes possible. The same applies to the amount of carbon fiber in Comparative Example 5, Examples 7 and 8, and the amount of carbon fiber in Comparative Examples 6 and 7, Examples 9 to 11.

[0061] [Table 4]

[0062] [Table 5]

[0063] [Table 6]

[0064] [Table 7]

[0065] As is clear from the results above, the molded articles formed from the pellets of this embodiment achieved mechanical strength close to that of articles made from virgin carbon fibers, despite using recycled carbon fibers, and also exhibited excellent flame retardancy (Examples 1-11). In particular, the retention rate of flexural strength was dramatically improved by using a metal salt-based flame retardant (comparison of Comparative Example 3 and Example 1, and comparison of Comparative Example 7 and Example 9). Furthermore, the retention rate of flexural strength was dramatically improved by using a polycarbonate resin having a predetermined end group concentration (comparison of Example 1 and Example 2, comparison of Example 7 and Example 8, and comparison of Example 9 and Example 10). Furthermore, the use of a metal salt-based flame retardant significantly improved the notch-free Charpy impact strength (comparison between Comparative Example 3 and Example 1, and comparison between Comparative Example 7 and Example 9).

Claims

1. A pellet formed from a composition containing 100 parts by mass of polycarbonate resin, 5 to 65 parts by mass of recycled carbon fiber which is a heated product of carbon fiber reinforced resin, and 0.01 to 0.30 parts by mass of a metal salt-based flame retardant.

2. The pellet according to claim 1, wherein the amount of terminal hydroxyl groups in the polycarbonate resin is 150 to 800 ppm.

3. The pellet according to claim 1 or 2, wherein the flexural strength measured in accordance with ISO 178 using an ISO multipurpose test specimen molded from the pellet is 85% or more when compared with the flexural strength measured in accordance with ISO 178 using an ISO multipurpose test specimen molded from a composition in which the polycarbonate resin contained in the pellet is replaced with a polycarbonate resin having an equal amount of terminal hydroxyl groups of 140 ppm, and the recycled carbon fibers are replaced with virgin carbon fibers having an equal amount of carbon fibers.

4. The pellet according to claim 1 or 2, wherein the metal salt-based flame retardant comprises an organosulfonic acid metal salt.

5. The pellet according to claim 1 or 2, wherein the polycarbonate resin includes recycled polycarbonate resin.

6. The pellet according to claim 1 or 2, further comprising 0.5 to 30 parts by mass of a fluid modifier per 100 parts by mass of the polycarbonate resin.

7. Furthermore, the pellet according to claim 1 or 2 further comprises, with respect to 100 parts by mass of the polycarbonate resin, a total of 0.1 to 10 parts by mass of at least one selected from a mold release agent and carbon black.

8. The polycarbonate resin has a terminal hydroxyl group content of 150 to 800 ppm. The flexural strength measured according to ISO 178 using an ISO multipurpose test specimen molded from the aforementioned pellets is 85% or higher when compared to the flexural strength measured according to ISO 178 using an ISO multipurpose test specimen molded from a composition in which the polycarbonate resin contained in the aforementioned pellets is replaced with a polycarbonate resin having an equal amount of terminal hydroxyl groups of 140 ppm, and the recycled carbon fibers are replaced with virgin carbon fibers having an equal amount of carbon fibers. The aforementioned metal salt-based flame retardant includes an organic sulfonic acid metal salt. The polycarbonate resin includes recycled polycarbonate resin. The above polycarbonate resin is further comprising 100 parts by mass of a fluid modifier, and 0.5 to 30 parts by mass of a fluid modifier. Furthermore, the pellet according to claim 1 further comprises, with respect to 100 parts by mass of the polycarbonate resin, a total of 0.1 to 10 parts by mass of at least one selected from a mold release agent and carbon black.

9. A molded article formed from pellets according to any one of claims 1, 2, and 8.

10. A method for producing pellets, comprising putting 100 parts by mass of polycarbonate resin, 5 to 65 parts by mass of recycled carbon fiber which is a heated product of carbon fiber reinforced resin, and 0.01 to 0.30 parts by mass of a metal salt-based flame retardant into an extruder and melt-kneading them together.

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