Resin composition, pellet, molded article, and method for producing resin composition

Abstract

To provide a resin composition which enables provision of a molded article that is excellent in impact resistance and has high rigidity, a pellet, a molded article, and a method for producing a resin composition.SOLUTION: A resin composition contains a polyamide resin and a reinforcement fiber, wherein the ratio of the reinforcement fiber contained in the resin composition is 58 to 75 mass%, the reinforcement fiber contains a flat glass fiber and a PAN-based carbon fiber having average cut lengths of 500 μm to 10 mm, and the mass ratio of the PAN-based carbon fiber to the flat glass fiber is 0.02 to 0.40.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition, a pellet, a molded article, and a method for producing a resin composition, and in particular to a resin composition containing a polyamide resin as a main component. [Background technology]

[0002] Polyamide resins are widely used as various industrial materials because of their excellent processability, durability, heat resistance, mechanical properties, and the like. As such polyamide resins, aliphatic polyamide resins such as polyamide 6 and polyamide 66 have long been used. Furthermore, aromatic polyamide resins using aromatic dicarboxylic acids and / or aromatic diamines as raw materials for polyamide resins have also come to be used. Furthermore, in order to improve the mechanical strength of polyamide resins, reinforcing fibers are blended into the polyamide resins (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-067166 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, with recent technological innovations, there is a demand for polyamide resin compositions with even better mechanical strength, in particular, polyamide resin compositions that are excellent in impact resistance and capable of providing molded articles with high rigidity. The present invention aims to solve the above problems, and aims to provide a resin composition, pellets, a molded article, and a method for producing a resin composition that can provide a molded article having excellent impact resistance and high rigidity. [Means for solving the problem]

[0005] In light of the above-mentioned problems, the present inventors conducted research and found that the above-mentioned problems can be solved by increasing the proportion of reinforcing fibers compared to conventional methods and by using a combination of specified glass fibers and carbon fibers in a specified ratio. Specifically, the above problems were solved by the following means. <1> A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.40. Resin composition. <2> When the resin composition is molded into an ISO dumbbell test piece having a thickness of 4 mm, the flexural modulus measured in accordance with ISO178 is 28 GPa or more. <1> The resin composition according to claim 1. <3> The polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, and 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine. <1> or <2> The resin composition according to claim 1. <4> the polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms; <1> ~ <3> 10. The resin composition according to claim 9 . <5> Further, the release agent is a metal salt of a fatty acid having a carbon chain number of 20 to 40. <1> ~ <4> 10. The resin composition according to claim 9 . <6> Further comprising a nucleating agent, <1> ~ <5> 10. The resin composition according to claim 9 . <7> Further, carbon black is included. <1> ~ <6> 10. The resin composition according to claim 9 . <8> When the resin composition is molded into an ISO dumbbell test piece having a thickness of 4 mm, the flexural modulus measured in accordance with ISO 178 is 28 GPa or more; the polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms; Further, the release agent is a metal salt of a fatty acid having a carbon chain number of 20 to 40, Further comprising a nucleating agent, Further, carbon black is included. <1> ~ <7> 10. The resin composition according to claim 9 . <9> <1> ~ <8> 2. A pellet of the resin composition according to claim 1. <10> <1> ~ <8> 2. A molded article formed from the resin composition according to claim 1. <11> <9> A molded article formed from the pellets according to claim 1. <12> A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.40. A method for producing a resin composition, comprising: The method includes melt-kneading at least a polyamide resin and a reinforcing fiber using an extruder, The method for producing a resin composition includes simultaneously feeding the PAN-based carbon fiber from an upstream side screw and feeding the flat glass fiber from a downstream side screw out of two side screws of the extruder. <13> A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.40. A method for producing a resin composition, comprising: The method includes melt-kneading at least a polyamide resin and a reinforcing fiber using an extruder, A method for producing a resin composition comprising simultaneously feeding PAN-based carbon fibers and flat glass fibers through one side screw of an extruder. <14> A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.40. A method for producing a resin composition, comprising: The method includes melt-kneading at least a polyamide resin and a reinforcing fiber using an extruder, A method for producing a resin composition comprising simultaneously feeding PAN-based carbon fibers and flat glass fibers through one side screw of an extruder. <15> The resin composition comprises: <1> ~ <8> 13. A method for producing the resin composition according to claim 12, wherein the resin composition is any one of the above. <16> The resin composition comprises: <1> ~ <8> The resin composition according to any one of the above items. <13> A method for producing the resin composition according to claim 1. <17> The resin composition comprises: <1> ~ <8> The resin composition according to any one of the above items. <14> A method for producing the resin composition according to claim 1. Effect of the Invention

[0006] According to the present invention, it is possible to provide a resin composition, pellets, a molded article, and a method for producing a resin composition, which are capable of producing a molded article having excellent impact resistance and high rigidity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an embodiment of the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to the present embodiment. In this specification, the use of "to" means that the numerical values ​​before and after it are included as the lower limit and upper limit. In this specification, various physical properties and characteristic values ​​are those at 23° C. unless otherwise specified.

[0008] In this specification, unless otherwise specified, the number average molecular weight is a polystyrene equivalent value measured by GPC (gel permeation chromatography). Specifically, it can be measured according to the description in paragraph 0047 of JP2018-165298A, the contents of which are incorporated herein by reference.

[0009] In this specification, the melting point (Tm) is a value measured according to differential scanning calorimetry (DSC) in accordance with ISO11357, unless otherwise specified. A differential scanning calorimeter is used, and the resin is placed in the measurement pan of the differential scanning calorimeter, heated to a temperature above the melting point at a heating rate of 10°C / min under a nitrogen atmosphere, and then rapidly cooled before measurement. The measurement conditions are a heating rate of 10°C / min, held at 280°C for 5 minutes, and then cooled down to 100°C at a cooling rate of -5°C / min to determine the melting point (Tm). As the differential scanning calorimeter, a "DSC-60" manufactured by SHIMADZU CORPORATION is used. If the measurement methods, etc. described in the standards shown in this specification vary from year to year, they will be based on the standards as of January 1, 2023, unless otherwise stated.

[0010] The resin composition of the present embodiment is a resin composition containing a polyamide resin and reinforcing fibers, characterized in that the proportion of reinforcing fibers contained in the resin composition is 58 to 75 mass %, the reinforcing fibers contain flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, and the mass ratio of PAN-based carbon fibers / flat glass fibers is 0.02 to 0.40. By adopting such a constitution, it is possible to provide a resin composition which is excellent in impact resistance and capable of producing a molded product with high rigidity. By increasing the proportion of reinforcing fibers in the resin composition, the rigidity of the resulting molded product tends to be increased. In particular, by blending PAN-based carbon fibers, the rigidity of the resulting molded product can be increased. However, as the content of PAN-based carbon fibers increases, the impact resistance tends to deteriorate. Therefore, in this embodiment, flat glass fibers having an average cut length of 500 μm to 10 mm are blended to improve the impact resistance. Then, by precisely adjusting the blending amount of the flat glass fibers and PAN-based carbon fibers, a resin composition capable of providing a molded product with a good balance between impact resistance and high rigidity has been successfully obtained. The details of this embodiment will be described below.

[0011] <Polyamide resin> The resin composition of the present embodiment contains a polyamide resin. The type of polyamide resin used in the present embodiment is not particularly limited, and may be an aliphatic polyamide resin or a semi-aromatic polyamide resin, but is more preferably a semi-aromatic polyamide resin.

[0012] Examples of aliphatic polyamide resins include polyamide 4, polyamide 46, polyamide 6, polyamide 66, polyamide 666, polyamide 610, polyamide 11, polyamide 12, and the like. As described above, the polyamide resin used in the present embodiment preferably contains a semi-aromatic polyamide resin. For example, it is more preferable that 90 mass % or more of the polyamide resin contained in the resin composition of the present embodiment is a semi-aromatic polyamide resin. Here, the semi-aromatic polyamide resin refers to a polyamide resin that is composed of a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, and 20 to 80 mol % (preferably 30 to 80 mol %, more preferably 40 to 70 mol %) of the total structural units of the diamine-derived structural unit and the dicarboxylic acid-derived structural unit contains an aromatic ring.

[0013] Examples of semi-aromatic polyamide resins include terephthalic acid-based polyamide resins (polyamide 6T, polyamide 9T, polyamide 10T) and xylylenediamine-based polyamide resins described below.

[0014] The polyamide resin used in this embodiment may be a recycled polyamide resin product (including recovered products, material recycled products, chemical recycled products, etc.), a rejected product, or scraps generated when molding a molded product from a resin composition.

[0015] In this embodiment, a polyamide resin containing diamine-derived structural units and dicarboxylic acid-derived structural units, in which 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine (hereinafter sometimes referred to as a "xylylenediamine-based polyamide resin") is preferred.

[0016] The diamine-derived constituent units of the xylylenediamine-based polyamide resin are more preferably 75 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, still more preferably 95 mol% or more, and particularly preferably 99 mol% or more, derived from xylylenediamine (preferably paraxylylenediamine and / or metaxylylenediamine).

[0017] The xylylenediamine is preferably paraxylylenediamine and / or metaxylylenediamine. The xylylenediamine preferably contains 0 to 100 mol% metaxylylenediamine and 100 to 0 mol% paraxylylenediamine (however, the sum of metaxylylenediamine and paraxylylenediamine does not exceed 100 mol%), more preferably contains 10 to 100 mol% metaxylylenediamine and 90 to 0 mol% paraxylylenediamine, even more preferably contains 20 to 100 mol% metaxylylenediamine and 80 to 0 mol% paraxylylenediamine, still more preferably contains 40 to 100 mol% metaxylylenediamine and 60 to 0 mol% paraxylylenediamine, even more preferably contains 60 to 100 mol% metaxylylenediamine and 40 to 0 mol% paraxylylenediamine, and even more preferably contains 90 to 100 mol% metaxylylenediamine and 10 to 0 mol% paraxylylenediamine. In the xylylenediamine-based polyamide resin, the total of the constitutional units derived from paraxylylenediamine and the constitutional units derived from metaxylylenediamine preferably accounts for 80 mol % or more, more preferably 85 mol % or more, even more preferably 90 mol % or more, still more preferably 95 mol % or more, still more preferably 98 mol % or more, and still more preferably 99 mol % or more of the constitutional units derived from diamine. The upper limit of the total of the constitutional units derived from paraxylylenediamine and the constitutional units derived from metaxylylenediamine is 100 mol %.

[0018] Diamines other than metaxylylenediamine and paraxylylenediamine that can be used as the raw diamine component of the xylylenediamine-based polyamide resin include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine, 1,3-bis( Examples of the diamines include alicyclic diamines such as bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring such as bis(4-aminophenyl)ether, paraphenylenediamine, and bis(aminomethyl)naphthalene. These can be used alone or in combination of two or more.

[0019] On the other hand, the dicarboxylic acid-derived structural units of the xylylenediamine-based polyamide resin are preferably derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms (preferably adipic acid) for 70 mol % or more, more preferably 75 mol % or more, even more preferably 80 mol % or more, even more preferably 90 mol % or more, still more preferably 95 mol % or more, and particularly preferably 99 mol % or more.

[0020] Examples of α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms that are suitable for use as the raw dicarboxylic acid component of the xylylenediamine-based polyamide resin include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, and 1,12-dodecanedioic acid. One or a mixture of two or more types can be used. Among these, at least one of adipic acid, sebacic acid, and 1,12-dodecanedioic acid is preferred, as the melting point of the polyamide resin falls within a range suitable for molding. Adipic acid and / or sebacic acid is more preferred, and adipic acid is even more preferred.

[0021] Examples of dicarboxylic acid components other than those mentioned above include phthalic acid compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and isomers of naphthalenedicarboxylic acids such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. These can be used alone or in combination of two or more kinds.

[0022] In addition, the xylylenediamine-based polyamide resin is mainly composed of diamine-derived structural units and dicarboxylic acid-derived structural units, but does not completely exclude other structural units, and may contain lactams such as ε-caprolactam and laurolactam, and aliphatic aminocarboxylic acid-derived structural units such as aminocaproic acid and aminoundecanoic acid. Here, the main component means that the total number of diamine-derived structural units and dicarboxylic acid-derived structural units is the largest among all structural units among the structural units constituting the xylylenediamine-based polyamide resin. In this embodiment, the total of diamine-derived structural units and dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin preferably accounts for 90% by mass or more of all structural units, more preferably accounts for 95% by mass or more, even more preferably accounts for 97% by mass or more, and even more preferably accounts for 99% by mass or more.

[0023] It is also preferable to use a polyamide resin produced using a biomass raw material (biomass polyamide resin) as the xylylenediamine-based polyamide resin. By using a biomass polyamide resin, it is possible to reduce the environmental load. For xylylenediamine-based polyamide resins, bio-adipic acid can be used as a biomass raw material. Mass balance certified (ISCC PLUS) adipic acid can also be used. Mass balance certification means that the amount of renewable raw materials and bio-raw materials used at each factory or production facility and the amount of products produced or shipped are quantified and guaranteed along with their quality.

[0024] The content of the xylylenediamine-based polyamide resin in 100 parts by mass of the polyamide resin in the resin composition of this embodiment is preferably 70 parts by mass or more, more preferably 75 parts by mass or more, and even more preferably 80 parts by mass or more, and may be 100 parts by mass or less. The polyamide resin used in the resin composition of the present embodiment is particularly preferably a blend of a xylylenediamine-based polyamide resin and polyamide 66.

[0025] The melting point of the polyamide resin is preferably 150°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher, and is preferably 350°C or lower, more preferably 330°C or lower, and even more preferably 300°C.

[0026] The lower limit of the number average molecular weight (Mn) of the polyamide resin is preferably 6,000 or more, more preferably 8,000 or more, and even more preferably 10,000 or more, and is preferably 100,000 or less, and more preferably 50,000 or less. Within such ranges, the heat resistance, elastic modulus, dimensional stability, and moldability are improved.

[0027] The content of the polyamide resin in the resin composition of this embodiment is preferably 25% by mass or more, more preferably 30% by mass or more, and even more preferably 32% by mass or more, based on 100% by mass of the resin composition. By making it equal to or more than the lower limit, the blending ratio of the reinforcing fiber can be suppressed to a certain extent, and the flow balance of the resin composition tends to be easily adjusted. In addition, the content of the polyamide resin in the resin composition of this embodiment is 42% by mass or less, preferably 40% by mass or less, and more preferably 38% by mass or less, based on the resin composition. By making it equal to or less than the upper limit, the blending ratio of the reinforcing fiber increases, and high physical properties in terms of rigidity and strength tend to be easily obtained. The resin composition of the present embodiment may contain only one type of polyamide resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0028] <Reinforced fiber> The resin composition of the present embodiment contains reinforcing fibers. By containing reinforcing fibers, a resin composition capable of providing a molded article having excellent mechanical strength can be obtained. The resin composition of the present embodiment contains flat glass fibers having an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, and the mass ratio of PAN-based carbon fibers / flat glass fibers is 0.02 to 0.40. By making the mass ratio equal to or more than the lower limit, a molded product having high rigidity tends to be obtained, and by making the mass ratio equal to or less than the upper limit, a molded product having excellent impact resistance tends to be obtained. The mass ratio of the PAN-based carbon fiber / flat glass fiber is preferably 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, even more preferably 0.06 or more, even more preferably 0.07 or more, and may be 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more depending on the application, etc. The mass ratio of the PAN-based carbon fiber / flat glass fiber is preferably 0.35 or less, more preferably 0.29 or less, even more preferably 0.27 or less, even more preferably 0.25 or less, even more preferably 0.23 or less, even more preferably 0.21 or less, even more preferably 0.20 or less, and may be 0.17 or less, 0.15 or less, 0.13 or less, 0.11 or less, or 0.09 or less depending on the application, etc. The resin composition of the present embodiment may contain only one type of flat glass fiber and one type of PAN-based carbon fiber having an average cut length of 500 μm to 10 mm, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0029] In addition, the ratio of the reinforcing fibers in the resin composition of this embodiment is 58% by mass or more, preferably 59% by mass or more, more preferably 60% by mass or more, even more preferably 62% by mass or more, even more preferably 63% by mass or more, even more preferably 64% by mass or more, and 75% by mass or less, preferably 74% by mass or less, more preferably 72% by mass or less, even more preferably 70% by mass or less, even more preferably 68% by mass or less, and even more preferably 66% by mass or less, based on 100% by mass of the resin composition. By making it equal to or more than the lower limit, a molded product having excellent mechanical strength can be obtained. Also, by making it equal to or less than the upper limit, there is a tendency that production stability during extrusion kneading and flowability during injection molding can be ensured.

[0030] The resin composition of the present embodiment may or may not contain reinforcing fibers other than flat glass fibers having an average cut length of 500 μm to 10 mm and PAN-based carbon fibers. In the present embodiment, it is preferable that the resin composition does not substantially contain reinforcing fibers other than flat glass fibers having an average cut length of 500 μm to 10 mm and PAN-based carbon fibers. "Substantially not containing" means that the content of reinforcing fibers other than flat glass fibers having an average cut length of 500 μm to 10 mm and PAN-based carbon fibers in the resin composition is less than 5% by mass of the resin composition, preferably less than 3% by mass, and more preferably less than 1% by mass.

[0031] <<Flat glass fiber with average cut length of 500μm~10mm>> The resin composition of the present embodiment contains flat glass fibers having an average cut length of 500 μm to 10 mm. By containing such flat glass fibers, the impact resistance of the obtained molded article can be further improved. The flat glass fiber used in the present embodiment has a noncircular cross section. The flat glass fiber has an aspect ratio, which is the long diameter / short diameter ratio of the cross section perpendicular to the longitudinal direction of the fiber, of preferably 1.1 or more, more preferably 1.5 or more, even more preferably 2 or more, even more preferably 2.5 or more, even more preferably 3 or more, even more preferably 3.5 or more, and preferably 10 or less, even more preferably 8 or less, even more preferably 6 or less, and even more preferably 5 or less. The average cut length of the flat glass is 500 μm or more, preferably 700 μm or more, more preferably 1 mm or more, and preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 5 mm or less. By making it equal to or more than the lower limit, impact resistance tends to be improved. By making it equal to or less than the upper limit, supplyability during extrusion kneading tends to be stable.

[0032] The flat glass fiber preferably has a number average fiber diameter of 1 to 25 μm, more preferably 5 to 17 μm, of the single fiber. By making the number average fiber diameter 1 μm or more, the molding processability of the resin composition tends to be improved. By making the number average fiber diameter 25 μm or less, the appearance of the obtained structure tends to be improved, and the reinforcing effect also tends to be improved. The flat glass fiber may be a single fiber or a plurality of single fibers twisted together. The cut length and cross-sectional flatness of flat glass fibers can be measured by observation using a scanning electron microscope (SEM) or other similar device. 50 or more fibers are randomly selected, their lengths are measured, and the number average value is calculated. The average diameter of the cross-section of glass fibers refers to the average diameter when converted into a circle of the same area.

[0033] The flat glass fibers used in this embodiment are preferably chopped strands.

[0034] The flat glass fiber is selected from glass compositions such as A glass, C glass, E glass, R glass, D glass, M glass, and S glass. In particular, E glass (alkali-free glass) is preferred. The flat glass fiber may be surface-treated with, for example, a silane-based compound, an epoxy-based compound, a urethane-based compound, etc., or oxidized, as long as it does not significantly impair the properties of the resin composition in this embodiment, in order to improve the affinity with the resin component. These sizing agents are preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on the flat glass fiber. As the lower limit when used, 0.1% by mass or more is preferred, more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more.

[0035] <<PAN-based carbon fiber>> The resin composition of this embodiment contains PAN-based carbon fiber. PAN-based carbon fiber is a carbon fiber composed of polyacrylonitrile. By including PAN-based carbon fiber, the rigidity of the resulting molded product can be improved. The average fiber diameter of the PAN-based carbon fiber used in this embodiment is preferably 1 to 100 μm, more preferably 3 to 50 μm, even more preferably 4 to 20 μm, and particularly preferably 5 to 10 μm. The average fiber diameter of the PAN-based carbon fiber can be measured by observation using a scanning electron microscope (SEM) or the like. Fifty or more fibers are randomly selected and the length is measured, and the number-average average fiber diameter is calculated.

[0036] Also, the average fiber length (cut length) of the PAN-based carbon fiber used in this embodiment is preferably 0.01 mm or more, more preferably 0.02 mm or more, even more preferably 0.1 mm or more, and particularly preferably 1 mm or more, and is preferably 10 mm or less. By setting it to the above lower limit value or more, the flexural modulus of the resulting molded product tends to be further improved. The average fiber length of the PAN-based carbon fiber can be measured by observation using a scanning electron microscope (SEM) or the like. Fifty or more fibers are randomly selected and the length is measured, and the number-average average fiber length is calculated.

[0037] The PAN-based carbon fiber used in this embodiment may have a surface treatment agent and / or a sizing agent on its surface. The surface treatment agent and / or the sizing agent is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on the carbon fiber. When used, the lower limit is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more. As the surface treatment agent and / or the sizing agent, preferred examples include epoxy compounds, acrylic compounds, silane compounds, titanate compounds, alkylene glycol compounds, carboxylic acid compounds, hydroxide compounds, isocyanate compounds, aldehyde compounds, unsaturated fatty acids, saturated fatty acids, and nylon. More specifically, the description in paragraphs 0050 to 0062 of JP2016-043526A can be referred to, and the contents thereof are incorporated herein by reference.

[0038] <Release agent> The resin composition of the present embodiment may contain a release agent. Examples of the release agent include aliphatic carboxylic acids, fatty acid metal salts, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds having a number average molecular weight of 200 to 15,000, polysiloxane-based silicone oils, ketone waxes, and light amides. Of these, aliphatic carboxylic acids, fatty acid metal salts, and esters of aliphatic carboxylic acids and alcohols are preferred, and aliphatic fatty acid metal salts are more preferred.

[0039] The fatty acid metal salt is preferably a fatty acid metal salt having a carbon chain number of 20 to 40. The fatty acid constituting the fatty acid metal salt is preferably a fatty acid having a carbon chain number of 21 or more, more preferably a fatty acid having a carbon chain number of 22 to 35, and even more preferably a fatty acid having a carbon chain number of 25 to 30. Specific examples of the fatty acid constituting the fatty acid metal salt include stearic acid, 12-hydroxystearic acid, behenic acid, montanic acid, and ricinoleic acid, with montanic acid being preferred. Examples of metals constituting the fatty acid metal salts include calcium, magnesium, zinc, aluminum, barium, and lithium, with calcium being preferred. For details of the release agent, in addition to the above, the descriptions in paragraphs 0055 to 0061 of JP2018-095706A can be referred to, the contents of which are incorporated herein by reference.

[0040] The content of the mold release agent (preferably a fatty acid metal salt having a carbon chain number of 20 to 40) in the resin composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polyamide resin. By making it equal to or more than the lower limit, the mold release resistance at the time of mold release can be reduced, and the ejection deformation of the molded product can be effectively suppressed. In addition, the content of the mold release agent (preferably a fatty acid metal salt having a carbon chain number of 20 to 40) in the resin composition of this embodiment is preferably 2.0 parts by mass or less, more preferably 1.4 parts by mass or less, even more preferably 1.1 parts by mass or less, and even more preferably 0.9 parts by mass or less, relative to 100 parts by mass of the polyamide resin. By making it equal to or less than the upper limit, bleeding out of the fatty acid metal salt and gas during molding can be effectively suppressed. The resin composition of the present embodiment may contain only one type of release agent (preferably a fatty acid metal salt having a carbon chain number of 20 to 40), or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0041] <Nucleating agent> The resin composition of the present embodiment may contain a nucleating agent, which can increase the crystallization rate.

[0042] The nucleating agent is not particularly limited as long as it is unmelted during melt processing and can become a crystal nucleus during the cooling process, and may be either an organic nucleating agent or an inorganic nucleating agent, with an inorganic nucleating agent being preferred. Examples of inorganic nucleating agents include graphite, molybdenum disulfide, barium sulfate, talc, calcium carbonate, sodium phosphate, mica and kaolin, and at least one selected from talc and calcium carbonate is more preferable, with talc being even more preferable. The organic nucleating agent is not particularly limited, and any known nucleating agent can be used. For example, the nucleating agent is preferably at least one selected from dibenzylidene sorbitol-based nucleating agents, nonitol-based nucleating agents, phosphate ester salt-based nucleating agents, rosin-based nucleating agents, and metal benzoate salt-based nucleating agents. The number average particle size of the nucleating agent has a lower limit of preferably 0.1 μm or more. The number average particle size of the nucleating agent has an upper limit of preferably 40 μm or less, more preferably 30 μm or less, even more preferably 28 μm or less, even more preferably 15 μm or less, and even more preferably 10 μm or less. By making the number average particle size 40 μm or less, the number of nucleating agents that become nuclei increases compared to the amount of nucleating agent blended, so that the crystal structure tends to be more stable.

[0043] The content of the nucleating agent in the resin composition of the present embodiment is more than 0.01 parts by mass, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polyamide resin. By making it equal to or more than the lower limit, the crystalline state of the resin composition can be more sufficiently stabilized. In addition, the content of the nucleating agent in the resin composition of the present embodiment is 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and may be 2 parts by mass or less, relative to 100 parts by mass of the polyamide resin. When the resin composition of the present embodiment contains a nucleating agent, it may contain only one type of nucleating agent, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0044] <Coloring agent> The resin composition of the present embodiment may contain a colorant. By containing a colorant, it is possible to impart color to the obtained molded article. The colorant may be a pigment or a dye, but is preferably a pigment. The colorant may be an achromatic colorant or a chromatic colorant, with an achromatic colorant being preferred. A black colorant composed of two or more chromatic colorants is also preferred. In this embodiment, preferred examples of the colorant include a black colorant (preferably a black pigment) and / or a white colorant (preferably a white pigment). An example of a black pigment is carbon black. An example of the white pigment is titanium oxide. It is preferable to use a pigment such as carbon black in the form of a masterbatch made with a thermoplastic resin (preferably a polyamide resin).

[0045] The content of the colorant (preferably carbon black) in the resin composition of this embodiment is preferably 0.0005 parts by mass or more, more preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, even more preferably 0.01 parts by mass or more, even more preferably 0.05 parts by mass or more, and even more preferably 0.10 parts by mass or more, relative to 100 parts by mass of the polyamide resin. By making it equal to or more than the lower limit, color development can be fully exhibited. In addition, the content of the colorant in the resin composition of this embodiment is preferably 10.00 parts by mass or less, more preferably 5.00 parts by mass or less, even more preferably 3.00 parts by mass or less, even more preferably 1.00 parts by mass or less, and even more preferably 0.50 parts by mass or less, relative to 100 parts by mass of the polyamide resin. By making it equal to or less than the upper limit, problems such as mold contamination during injection molding can be effectively suppressed. The resin composition of the present embodiment may contain only one type of colorant, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0046] <Other ingredients> The resin composition of the present embodiment may contain other components other than those described above. As other components, additives such as thermoplastic resins other than polyamide resins, antioxidants such as heat stabilizers and weather stabilizers, flame retardants, flame retardant assistants, anti-dripping agents, matting agents, ultraviolet absorbers, plasticizers, antistatic agents, coloring inhibitors, and gelling inhibitors may be added as necessary. Each of these additives may be one type or two or more types. Details of these components can be blended with the additives described in paragraphs 0047 to 0103 of International Publication No. 2021 / 241471, the contents of which are incorporated herein by reference. The total amount of these components in the resin composition of this embodiment is preferably less than 5 mass %, more preferably less than 3 mass %, and even more preferably less than 1 mass % of the resin composition.

[0047] <Physical properties of resin composition> The resin composition of the present embodiment preferably has high rigidity. Specifically, when the resin composition of the present embodiment is molded into an ISO dumbbell test piece having a thickness of 4 mm, the flexural modulus measured in accordance with ISO 178 is preferably 28 GPa or more. The upper limit of the flexural modulus is not particularly specified, but for example, 50 GPa or less, or even 40 GPa or less, sufficiently satisfies the required performance.

[0048] The resin composition of the present embodiment preferably has excellent impact resistance. Specifically, when the resin composition of the present embodiment is molded into an ISO dumbbell test piece having a thickness of 4 mm, the notched Charpy impact strength measured in accordance with ISO179-1,2 is 14 kJ / m 2 It is preferable that the concentration is 16 kJ / m or more. 2 The upper limit of the notched Charpy impact strength is not particularly limited, but is preferably 40 kJ / m 2 Below 35kJ / m 2 Even if it is less than this, it will be sufficient to meet the required performance. In addition, when the resin composition of this embodiment is molded into an ISO dumbbell test piece having a thickness of 4 mm, the unnotched Charpy impact strength measured in accordance with ISO179-1,2 is 31 kJ / m 2 It is preferable that the concentration is 34 kJ / m or more. 2 More preferably, it is 36 kJ / m or more. 2 More preferably, it is 38 kJ / m or more. 2 The upper limit of the Charpy notched impact strength is not particularly limited, but is preferably 60 kJ / m 2 Below 55kJ / m 2 Even if it is less than this, it will be sufficient to meet the required performance. In particular, it is preferable that the resin composition of the present embodiment satisfies both the flexural modulus and the Charpy impact strength above. The flexural modulus and Charpy impact strength are measured according to the description in the examples given below.

[0049] <Method of producing resin composition> In the present embodiment, the method for producing the resin composition is not particularly specified, and a wide variety of known methods for producing thermoplastic resin compositions can be used. Specifically, the resin composition can be produced by mixing the components in advance using various mixers such as a tumbler or a Henschel mixer, and then melt-kneading the components using a Banbury mixer, a roll, a Brabender, a single-screw extruder, a twin-screw extruder, a kneader, or the like.

[0050] Also, for example, the resin composition can be produced by not mixing the components in advance, or by mixing only some of the components in advance, feeding the mixture to an extruder using a feeder, and melt-kneading the mixture. Furthermore, for example, some of the components such as a colorant may be mixed in advance, fed to an extruder, and melt-kneaded to obtain a masterbatch composition, which may then be mixed again with the remaining components and melt-kneaded to produce pellets. In addition, the reinforcing fibers are preferably side-fed.

[0051] In this embodiment, a method for producing a resin composition comprising a polyamide resin and reinforcing fibers, in which the proportion of reinforcing fibers contained in the resin composition is 58 to 75 mass%, the reinforcing fibers include flat glass fibers and PAN-based carbon fibers having an average cut length of 500 μm to 10 mm, and the mass ratio of PAN-based carbon fibers / flat glass fibers is 0.02 to 0.40, is disclosed, which includes melt-kneading at least the polyamide resin and the reinforcing fibers using an extruder, and simultaneously supplying the PAN-based carbon fibers from the upstream side screw and the flat glass fibers from the downstream side screw of two side screws of the extruder. In this way, by simultaneously feeding the PAN-based carbon fiber from the upstream side screw and the flat glass fiber from the downstream side screw, the flat glass fiber becomes less likely to break, and the fiber length of the flat glass fiber can be maintained longer in the obtained molded product. As a result, a resin composition capable of providing a molded product with excellent impact resistance and high rigidity is obtained. In addition, in this embodiment, there is disclosed a method for producing a resin composition comprising a polyamide resin and reinforcing fibers, wherein the proportion of reinforcing fibers contained in the resin composition is 58 to 75 mass%, the reinforcing fibers include flat glass fibers and PAN-based carbon fibers having an average cut length of 500 μm to 10 mm, and the mass ratio of PAN-based carbon fibers / flat glass fibers is 0.02 to 0.40, the method comprising melt-kneading at least the polyamide resin and the reinforcing fibers using an extruder, and simultaneously supplying the PAN-based carbon fibers and the flat glass fibers from one side screw of the extruder. Further, in this embodiment, a resin composition containing a polyamide resin and a reinforcing fiber, the ratio of the reinforcing fiber contained in the resin composition is 58 to 75 mass%, the reinforcing fiber contains flat glass fiber having an average cut length of 500 μm to 10 mm and PAN-based carbon fiber, and the mass ratio of PAN-based carbon fiber / flat glass fiber is 0.02 to 0.40. The method for producing the resin composition includes melt-kneading at least the polyamide resin and the reinforcing fiber using an extruder, and includes simultaneously feeding the flat glass fiber from the upstream side screw and the PAN-based carbon fiber from the downstream side screw of two side screws of the extruder. The molded article formed from the resin composition obtained by such a method tends to have improved mechanical properties. The resin composition obtained by the above-mentioned method for producing a resin composition is preferably the resin composition of the present embodiment described above, and the preferred ranges thereof are also the same.

[0052] <Applications of resin compositions and molded products> The molded article of the present embodiment is formed from the resin composition or pellets of the present embodiment. The method for producing the molded article of the present embodiment is not particularly limited. As an example, an injection molded article molded by injection molding is exemplified. For example, the molded product of this embodiment may be produced by melt-kneading the components and then directly molding the components using various molding methods, or by melt-kneading the components and pelletizing them, and then melting them again and molding them using various molding methods.

[0053] The method for molding the molded product is not particularly limited, and any conventionally known molding method can be used, such as injection molding, injection compression molding, extrusion molding, profile extrusion, transfer molding, hollow molding, gas-assisted hollow molding, blow molding, extrusion blow molding, IMC (in-mold coating molding), rotational molding, multi-layer molding, two-color molding, insert molding, sandwich molding, foam molding, and pressure molding.

[0054] The shape of the molded product of the present embodiment is not particularly limited and can be appropriately selected depending on the application and purpose of the molded product. Examples of the shape include plate-like, plate-like, rod-like, sheet-like, film-like, cylindrical, annular, circular, elliptical, gear-like, polygonal, irregularly shaped, hollow, frame-like, box-like, and panel-like shapes.

[0055] The fields of use of the resin composition, pellets, and molded articles of this embodiment are not particularly limited, and they are widely used in automobile and other transportation vehicle parts, general machine parts, precision machine parts, electronic and electrical device parts, office automation device parts, building materials and housing related parts, medical devices, leisure sports goods, game machines, play equipment, medical products, daily necessities such as food packaging films, defense and aerospace products, etc. In particular, it is preferably used for the frames, back covers, or stands of smartphones, tablets, notebook computers, and other displays. EXAMPLES

[0056] The present invention will be described in more detail below with reference to examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing 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 the like, measurements can be made using other instruments with equivalent performance.

[0057] 1. Raw materials The raw materials shown in Table 1 below were used. [Table 1]

[0058] 2. Examples 1 to 3 and Comparative Examples 1 to 5 <Compound> The components shown in Table 1 were weighed out as shown in Table 2 or Table 3 (each component is expressed in parts by mass), and the components other than the carbon fiber and glass fiber were blended in a tumbler, and the blend was added to the base of a twin-screw extruder (Shibaura Machine Co., Ltd., TEM26SS) and melted. Then, the carbon fiber was fed from the upstream side screw and the glass fiber was fed from the downstream side screw at the same time to prepare pellets of the resin composition. The temperature of the twin-screw extruder was set to 280°C.

[0059] <Flexural strength and flexural modulus> The thermoplastic resin pellets obtained by the above-mentioned manufacturing method were dried at 80°C for 12 hours, and then injection-molded into ISO dumbbell test pieces (4 mm thick) using an injection molding machine (Nissei Plastic Industrial Co., Ltd., "NEX140III") under conditions of a cylinder temperature of 290°C, a mold temperature of 130°C, and a molding cycle of 50 seconds. The flexural strength (unit: MPa) and flexural modulus (unit: GPa) were measured in an environment of 23°C and 50% humidity using the above ISO dumbbell test pieces (4 mm thick) in accordance with ISO 178. The results are shown in Table 2 or Table 3.

[0060] <Charpy impact strength> In accordance with ISO179-1 and 2, the unnotched Charpy impact strength was measured using the above ISO dumbbell test pieces (4 mm thick) in an environment of a temperature of 23° C. and a humidity of 50%. In addition, in accordance with ISO179-1 and 2, the above ISO tensile test pieces (4 mm thick) were used to measure the notched Charpy impact strength (unit: kJ / m) using a 1J hammer under conditions of 23°C temperature and 50% humidity. 2 The results are shown in Table 2 or Table 3.

[0061] <Deflection temperature under load (DTUL)> In accordance with ISO75-1 and 2, the deflection temperature under load (unit: °C) was measured using the above ISO dumbbell test piece (thickness: 4 mm) under a bending stress of 1.80 MPa.

[0062] 3. Example 4 In Example 1, the composition was changed as shown in Table 3, but the rest was the same.

[0063] 4. Example 4 The same procedure was carried out as in Example 1, except that during <compounding>, glass fibers were fed simultaneously from the upstream side screw and carbon fibers were fed simultaneously from the downstream side screw.

[0064] [Table 2]

[0065] [Table 3]

[0066] As is clear from the above results, the resin composition of the present embodiment had high bending strength and bending modulus, and further had high Charpy impact strength and high deflection temperature under load (Examples 1 to 5). In addition, by simultaneously feeding glass fiber from the upstream side screw and carbon fiber from the downstream side screw, the mechanical strength of the obtained molded product was further improved (Example 5). In contrast, when no carbon fiber was included (Comparative Example 1), the flexural modulus was low. In addition, even when PAN-based carbon fiber and a specified flat glass fiber were included, when the ratio of the two was outside the range of the present invention (Comparative Example 2), the impact resistance was low. In addition, when round glass fiber was blended instead of the flat glass fiber (Comparative Example 3), the impact resistance was low. Furthermore, even when PAN-based carbon fiber and a specified flat glass fiber were included, when the total amount of these was small (Comparative Example 4), both the flexural modulus and impact resistance were poor. In addition, when PICTH-based carbon fiber was used instead of PAN-based carbon fiber (Comparative Example 5), the bending properties and impact resistance were poor.

Claims

1. A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.

40. Resin composition.

2. The resin composition according to claim 1, wherein the resin composition has a flexural modulus of 28 GPa or more when molded into an ISO dumbbell test piece having a thickness of 4 mm, as measured in accordance with ISO 178.

3. 3. The resin composition according to claim 1, wherein the polyamide resin contains a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, and 70 mol % or more of the diamine-derived structural unit is derived from xylylenediamine.

4. The polyamide resin comprises a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, and 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. The resin composition according to claim 1 or 2.

5. 3. The resin composition according to claim 1, further comprising a release agent, the release agent being a metal salt of a fatty acid having a carbon chain number of 20 to 40.

6. The resin composition according to claim 1 or 2, further comprising a nucleating agent.

7. The resin composition according to claim 1 or 2, further comprising carbon black.

8. When the resin composition is molded into an ISO dumbbell test piece having a thickness of 4 mm, the flexural modulus measured in accordance with ISO 178 is 28 GPa or more; the polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms; Further, the release agent is a metal salt of a fatty acid having a carbon chain number of 20 to 40, Further comprising a nucleating agent, The resin composition according to claim 1 , further comprising carbon black.

9. A pellet of the resin composition according to claim 1, 2 or 8.

10. A molded article formed from the resin composition according to claim 1, 2 or 8.

11. A molded article formed from the pellets of claim 9.

12. A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.

40. A method for producing a resin composition, comprising: The method includes melt-kneading at least a polyamide resin and a reinforcing fiber using an extruder, The method for producing a resin composition includes simultaneously supplying PAN-based carbon fibers from an upstream side screw and flat glass fibers from a downstream side screw of two side screws of the extruder.

13. A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.

40. A method for producing a resin composition, comprising: A method for producing a resin composition, comprising melt-kneading at least a polyamide resin and reinforcing fibers using an extruder, and simultaneously supplying flat glass fibers from an upstream side screw and PAN-based carbon fibers from a downstream side screw of two side screws of the extruder.

14. A resin composition comprising a polyamide resin and a reinforcing fiber, The ratio of reinforcing fibers contained in the resin composition is 58 to 75% by mass, The reinforcing fibers include flat glass fibers with an average cut length of 500 μm to 10 mm and PAN-based carbon fibers, The mass ratio of PAN-based carbon fiber to flat glass fiber is 0.02 to 0.

40. A method for producing a resin composition, comprising: The method includes melt-kneading at least a polyamide resin and a reinforcing fiber using an extruder, A method for producing a resin composition comprising simultaneously feeding PAN-based carbon fibers and flat glass fibers through one side screw of an extruder.

15. The method for producing a resin composition according to claim 12, wherein the resin composition is the resin composition according to claim 1, 2 or 8.

16. The method for producing a resin composition according to claim 13, wherein the resin composition is the resin composition according to claim 1, 2 or 8.

17. The method for producing a resin composition according to claim 14, wherein the resin composition is the resin composition according to claim 1, 2 or 8.

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