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

Abstract

To provide a resin composition that gives a molding having excellent mechanical strength, and has antistatic properties and also has excellent fluidity during melting, a molding formed from the resin composition and a method for producing the resin composition.SOLUTION: A resin composition contains a polyamide resin, reinforcements, and single-wall carbon nanotubes, the content of the single-wall carbon nanotubes being 0.01-1.0 mass% relative to the resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a molded article, and a method for producing a resin composition. [Background technology]

[0002] Polyamide resins are used in a variety of applications, taking advantage of their excellent heat resistance and mechanical properties. Here, blending of carbon nanotubes (CNTs) into polyamide resins has been investigated for various purposes. For example, Patent Document 1 discloses blending of CNTs into polyamide resins to impart electrical conductivity and antistatic properties to the polyamide resins. Patent Document 2 discloses blending of a carbon nanofiller such as CNTs into polyamide resins to increase the crystallization rate of the polyamide resins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-177862 [Patent Document 2] International Publication No. 2014 / 199045 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, a reinforcing material has been blended into a polyamide resin to increase the mechanical strength of molded articles obtained from the polyamide resin. It has been considered to blend CNTs into resin compositions obtained by blending a reinforcing material into a polyamide resin to impart antistatic properties. However, the inventors have conducted research and found that blending CNTs into a resin composition containing a polyamide resin and a reinforcing material can result in poor fluidity of the resin composition when melted. Poor fluidity can result in poor moldability during molding, such as injection molding, and can cause poor appearance of the resulting molded article. The present invention aims to solve the above problems, and has an object to provide a resin composition which produces a molded article having excellent mechanical strength and antistatic properties, and which also has excellent fluidity when melted, a molded article formed from the resin composition, and a method for producing the resin composition. [Means for solving the problem]

[0005] As a result of investigations conducted by the present inventors in light of the above-mentioned problems, it was found that the above-mentioned problems could be solved by using single-walled carbon nanotubes as CNTs. Specifically, the above-mentioned problems were solved by the following means. <1> A resin composition comprising a polyamide resin, a reinforcing material, and single-walled carbon nanotubes, wherein the content of the single-walled carbon nanotubes is 0.01 to 1.0% by mass relative to the resin composition. <2> 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> The resin composition according to claim 1. <3> 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 9 carbon atoms. <2> The resin composition according to claim 1. <4> 70 mol% or more of the xylylenediamine is meta-xylylenediamine, <2> or <3> The resin composition according to claim 1. <5> The reinforcing material includes at least one of glass fiber and carbon fiber. <1> ~ <4> The resin composition according to any one of the above. <6> The content of the reinforcing material is 15 to 60 mass% based on the resin composition. <1> ~ <5> The resin composition according to any one of the above. <7> The mass ratio of the content of the single-walled carbon nanotubes to the content of the reinforcing material, i.e., single-walled carbon nanotubes / reinforcing material, is 0.0015 to 0.0500. <1> ~ <6> The resin composition according to any one of the above. <8> The single-walled carbon nanotubes are derived from masterbatched single-walled carbon nanotubes. <1> ~ <7> The resin composition according to any one of the above. <9> The masterbatch single-walled carbon nanotubes are obtained by adding single-walled carbon nanotubes during synthesis of a polyamide resin. <8> The resin composition according to claim 1. <10> <1> ~ <9> A molded article formed from the resin composition according to any one of the above items. <11> <1> ~ <9> A method for producing the resin composition according to any one of the above, A method for producing a resin composition, comprising melt-kneading a polyamide resin, a reinforcing material, and masterbatched single-walled carbon nanotubes, wherein the content of the single-walled carbon nanotubes in the resin composition is 0.01 to 1.0 mass%. <12> and adding single-walled carbon nanotubes to the polyamide resin during synthesis thereof to prepare a masterbatch of single-walled carbon nanotubes. <11> A method for producing the resin composition described in claim 1. [Effects of the Invention]

[0006] The present invention makes it possible to provide a resin composition from which a molded article obtained has excellent mechanical strength and antistatic properties, and further has excellent fluidity when melted, as well as a molded article formed from the resin composition and a method for producing the resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment for carrying out 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 only this embodiment. In this specification, the symbol "to" is used to mean 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. If the standards shown in this specification differ depending on the year and the measurement method, etc., they will be based on the standards as of January 1, 2021, unless otherwise stated. In this specification, single-walled carbon nanotubes may be referred to as SWCNTs, multi-walled carbon nanotubes as MWCNTs, and carbon nanotubes as CNTs.

[0008] The resin composition of this embodiment is a resin composition containing a polyamide resin, a reinforcing material, and single-walled carbon nanotubes, and is characterized in that the content of SWCNTs in the resin composition is 0.01 to 1.0% by mass. By adopting such a constitution, it is possible to obtain a resin composition which produces a molded article having excellent mechanical strength and antistatic properties, and which also has excellent fluidity when melted. In order to increase the mechanical strength of molded articles obtained from polyamide resins, a reinforcing material is blended into the polyamide resin. However, blending CNTs to impart antistatic properties to a resin composition obtained by blending a reinforcing material into a polyamide resin may result in poor fluidity during melting (particularly fluidity during molding of a molded article). In this embodiment, it has been discovered that by using SWCNTs as the CNTs, a resin composition can be obtained that has high mechanical strength, excellent antistatic properties, and can maintain fluidity during melting. The reason for this is presumed to be as follows. That is, it was speculated that the decrease in fluidity due to the incorporation of CNTs was caused by the aggregation of CNTs in the resin composition. It was speculated that the use of SWCNTs as CNTs could suppress CNT aggregation and thus suppress the decrease in fluidity of the resin composition when melted. Furthermore, it was speculated that the use of SWCNTs could suppress CNT aggregation, i.e., increase the dispersibility of SWCNTs in the resin composition, thereby imparting sufficient antistatic properties even with a reduced amount of CNT in the resin composition. It was also speculated that the reduction in the amount of CNT in the resin composition could further suppress CNT aggregation and effectively suppress the decrease in fluidity. The resin composition of this embodiment will be described in detail below.

[0009] <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. Examples of aliphatic polyamide resins include polyamide 6, polyamide 11, polyamide 12, polyamide 46, polyamide 66, polyamide 666, polyamide 610, and polyamide 612, with polyamide 6 and polyamide 66 being preferred, and polyamide 66 being more preferred. The polyamide resin used in this embodiment preferably contains a semi-aromatic polyamide resin. For example, it is more preferable that 90% by mass or more of the polyamide resin contained in the resin composition is a semi-aromatic polyamide resin. Here, the semi-aromatic polyamide resin refers to a resin composed of diamine-derived structural units and dicarboxylic acid-derived structural units, in which 20 to 80 mol % (preferably 30 to 70 mol %, more preferably 40 to 60 mol %) of the total structural units of the diamine-derived structural units and the dicarboxylic acid-derived structural units contain aromatic rings. By using such a semi-aromatic polyamide resin, the mechanical strength of the resulting multilayer film can be improved. Examples of semi-aromatic polyamide resins include terephthalic acid-based polyamide resins (polyamide 6T, polyamide 9T, polyamide 10T) and the xylylenediamine-based polyamide resins described below. In addition to the above, for polyamide resins, reference can be made to, for example, paragraphs 0011 to 0013 of JP-A No. 2011-132550, the contents of which are incorporated herein by reference.

[0010] At least one of the polyamide resins used in this embodiment contains diamine-derived structural units and dicarboxylic acid-derived structural units, and preferably 70 mol% or more of the diamine-derived structural units are derived from xylylenediamine (preferably metaxylylenediamine). Hereinafter, such polyamide resins may be referred to as xylylenediamine-based polyamide resins. By using xylylenediamine-based polyamide resins, high rigidity can be achieved in the resulting molded articles. The diamine-derived structural units in the xylylenediamine-based polyamide resin are more preferably 75 mol% or more, even more preferably 80 mol% or more, even more preferably 85 mol% or more, still more preferably 90 mol% or more, and even more preferably 95 mol% or more derived from xylylenediamine (preferably metaxylylenediamine).

[0011] Diamines other than xylylenediamine that can be used as raw diamine components for xylylenediamine-based polyamide resins 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(aminomethyl)silane; Examples include alicyclic diamines such as 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; and these can be used alone or in combination of two or more.

[0012] On the other hand, the dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin are not particularly limited, and may include structural units derived from at least one of aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. Preferably, the xylylenediamine-based polyamide resin includes at least structural units derived from aliphatic dicarboxylic acids, more preferably structural units derived from an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and even more preferably structural units derived from an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 9 carbon atoms. Of the dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin, preferably 70 mol % or more, more preferably 75 mol % or more, even more preferably 80 mol % or more, still more preferably 90 mol % or more, and even more preferably 95 mol % or more are derived from an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms (preferably an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 9 carbon atoms). 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 xylylenediamine-based polyamide resins include succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid. These can be used alone or in combination of two or more. Of these, adipic acid or sebacic acid are more preferred, and adipic acid is even more preferred, as the melting point of the polyamide resin is within a range suitable for molding.

[0013] Examples of dicarboxylic acid components other than the above-mentioned α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms include phthalic acid compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and isomers of naphthalenedicarboxylic acid 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, and these can be used alone or in combination of two or more.

[0014] In the xylylenediamine-based polyamide resin of this embodiment, 0 to 100 mol % of the diamine-derived structural units are derived from paraxylylenediamine, 100 to 0 mol % are derived from metaxylylenediamine, and 70 mol % or more (preferably 80 mol % or more, more preferably 90 mol % or more) of the dicarboxylic acid-derived structural units are derived from sebacic acid and / or adipic acid (preferably adipic acid). A more preferred embodiment A of the xylylenediamine-based polyamide resin is one in which 70 mol % or more (preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more) of the diamine-derived structural units are derived from paraxylylenediamine, and 70 mol % or more (preferably 80 mol % or more, more preferably 90 mol % or more) of the dicarboxylic acid-derived structural units are derived from sebacic acid. Furthermore, a more preferred embodiment B of the xylylenediamine-based polyamide resin is a polyamide resin in which 30 to 90 mol % (preferably 60 to 80 mol %) of the diamine-derived structural units are derived from metaxylylenediamine, 70 to 10 mol % (preferably 40 to 20 mol %) are derived from paraxylylenediamine, and 70 mol % or more (preferably 80 mol % or more, more preferably 90 mol % or more) of the dicarboxylic acid-derived structural units are derived from sebacic acid. A more preferred embodiment C of the xylylenediamine-based polyamide resin is one in which 70 mol % or more (preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more) of the diamine-derived structural units are derived from metaxylylenediamine, and 70 mol % or more (preferably 80 mol % or more, more preferably 90 mol % or more) of the dicarboxylic acid-derived structural units are derived from adipic acid. In the resin composition, embodiment C is particularly preferred. In any of the above embodiments, the total amount of constitutional units derived from diamines does not exceed 100 mol %, and the total amount of constitutional units derived from dicarboxylic acids does not exceed 100 mol %.

[0015] In this embodiment, the semi-aromatic polyamide resin (preferably a xylylenediamine-based polyamide resin) is primarily composed of diamine-derived structural units and dicarboxylic acid-derived structural units. However, other structural units are not completely excluded, and it goes without saying that the semi-aromatic polyamide resin may contain structural units derived from lactams such as ε-caprolactam and laurolactam, and aliphatic aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid. Here, "primary component" refers to the structural units constituting the semi-aromatic polyamide resin in which the total number of diamine-derived structural units and dicarboxylic acid-derived structural units is the largest among all structural units. In this embodiment, the total of the diamine-derived structural units and dicarboxylic acid-derived structural units in the semi-aromatic polyamide resin preferably accounts for 90% or more of all structural units, more preferably 95% or more, and even more preferably 98% or more.

[0016] The melting point of the polyamide resin is preferably 150 to 350°C, more preferably 180 to 330°C, and even more preferably 200 to 300°C. The melting point can be measured by differential scanning calorimetry in accordance with JIS K7121 and K7122.

[0017] The polyamide resin preferably has a number average molecular weight (Mn) of 6,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, even more preferably 15,000 or more, even more preferably 20,000 or more, and even more preferably 22,000 or more. The upper limit of Mn is preferably 35,000 or less, more preferably 30,000 or less, even more preferably 28,000 or less, and even more preferably 26,000 or less. Within these ranges, the heat resistance, elastic modulus, dimensional stability, and moldability are improved.

[0018] The lower limit of the relative viscosity of the polyamide resin in this embodiment is preferably 1.9 or more, more preferably 2.0 or more, and even more preferably 2.1 or more, while the upper limit of the relative viscosity of the polyamide resin is preferably 4.0 or less, more preferably 3.9 or less, and even more preferably 3.8 or less. The relative viscosity of the polyamide resin is measured under the conditions of JIS K 69020-2.

[0019] The content of the polyamide resin in the resin composition is preferably 40.0% by mass or more, more preferably 45.0% by mass or more, and may be 55.0% by mass or more depending on the application. By making the content equal to or greater than the lower limit, the fluidity of the resin composition when melted tends to be further improved. The content of the polyamide resin in the resin composition is preferably 75.0% by mass or less, more preferably 70.0% by mass or less, and may further be 65.0% by mass or less or 60.0% by mass or less depending on the application. The resin composition 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.

[0020] <Reinforcement material> The resin composition of the present embodiment contains a reinforcing material, which can improve the mechanical strength of the resulting molded article. The reinforcing material that can be contained in the resin composition of this embodiment has the effect of improving the mechanical properties of the resulting resin composition when blended with the resin, and can be any commonly used reinforcing material for plastics. The reinforcing material can be either organic or inorganic, with inorganic materials being preferred. The reinforcing material is preferably a fibrous reinforcing material such as glass fiber, carbon fiber, basalt fiber, wollastonite, or potassium titanate fiber. Granular or amorphous reinforcing materials such as titanium oxide, feldspar minerals, clay, organoclay, or glass beads; or scaly reinforcing materials such as glass flakes or graphite can also be used. In this embodiment, among the above, from the viewpoints of mechanical strength, rigidity, and heat resistance, it is preferable to contain a fibrous reinforcing material, more preferably to contain at least one of glass fiber and carbon fiber, and even more preferably to contain glass fiber. As the fibrous reinforcing filler, either a round cross-sectional shape or an irregular cross-sectional shape can be used. It is more preferable to use a reinforcing material that has been surface-treated with a surface treatment agent such as a coupling agent. In particular, glass fibers with a surface treatment agent attached thereto are preferred because they have excellent durability, moist heat resistance, hydrolysis resistance, and heat shock resistance.

[0021] The glass fibers are made of glass compositions such as A-glass, C-glass, E-glass, S-glass, R-glass, M-glass, and D-glass, with E-glass (alkali-free glass) being particularly preferred. Glass fiber refers to a fiber whose cross section cut perpendicular to the length direction has a circular or polygonal shape and exhibits a fibrous appearance.

[0022] The glass fiber used in the resin composition of this embodiment may be a single fiber or a plurality of single fibers twisted together. The glass fiber may be in any form, such as a "glass roving" made by continuously winding a single fiber or a plurality of twisted single fibers, a "chopped strand" cut to a length of 1 to 10 mm, or a "milled fiber" pulverized to a length of 10 to 500 μm. Such glass fibers are readily available commercially from Asahi Fiber Glass Co., Ltd. under the trade names "Glaslon Chopped Strand" and "Glaslon Milled Fiber." Glass fibers of different forms can also be used in combination.

[0023] The glass fibers used in this embodiment may have a circular or non-circular cross section. By using glass fibers having a non-circular cross section, warpage of the resulting molded article can be more effectively suppressed. In this embodiment, warpage can also be effectively suppressed even when glass fibers having a circular cross section are used.

[0024] The content of the reinforcing material in the resin composition of this embodiment is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, and may be 35% by mass or more or 40% by mass or more. The upper limit is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 52% by mass or less, and may even be 48% by mass or less or 45% by mass or less. The content of the reinforcing material in the resin composition of this embodiment is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and may be 45 parts by mass or more, relative to 100 parts by mass of the polyamide resin. The upper limit is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, even more preferably 120 parts by mass or less, even more preferably 110 parts by mass or less, and may be 90 parts by mass or less, relative to 100 parts by mass of the polyamide resin. The resin composition of this embodiment may contain only one type of reinforcing material, or may contain two or more types. When two or more types are contained, the total amount falls within the above range. Note that the content of the reinforcing material in this embodiment is intended to include the amounts of the sizing agent and the surface treatment agent.

[0025] <Single-walled carbon nanotubes (SWCNTs)> The resin composition of this embodiment contains single-walled carbon nanotubes (SWCNTs). The inclusion of SWCNTs makes it possible to impart antistatic properties to the resulting molded article. Furthermore, the use of SWCNTs more effectively prevents a decrease in the fluidity of the resin composition when melted, compared to the use of MWCNTs. SWCNTs, for example, are seamless cylindrical materials formed from a single layer of graphene, and are distinguished from MWCNTs, which are made up of multiple concentrically stacked tubes of rolled graphene. Examples of SWCNTs include zigzag type, armchair type, and chiral type, and any type may be used. The SWCNTs used in this embodiment are commercially available products, and examples thereof include SWCNTs available from Zeon Corporation and OCSiAl Corp. In addition to the name carbon nanotubes, CNTs are also called graphite fibrils, carbon fibrils, etc. The diameter (number average fiber diameter) of the carbon nanotubes is preferably 0.5 to 30 nm, more preferably 1 to 10 nm.The aspect ratio is preferably 300 to 5,000, more preferably 1,000 to 5,000, and even more preferably 2,000 to 5,000.

[0026] In this embodiment, the SWCNTs are preferably derived from masterbatched single-walled carbon nanotubes. By using masterbatched SWCNTs, aggregation of CNTs in the resulting resin composition can be effectively suppressed. For details on masterbatching, please refer to the items described below in the section on the manufacturing method.

[0027] The content of SWCNTs in the resin composition is 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.10% by mass or more, even more preferably 0.15% by mass or more, and may be 0.25% by mass or more. By ensuring that the content is equal to or greater than the lower limit, antistatic properties are effectively exhibited. Furthermore, the content of SWCNTs in the resin composition is 1.0% by mass or less, preferably 0.9% by mass or less, more preferably 0.7% by mass or less, even more preferably 0.6% by mass or less, even more preferably 0.45% by mass or less, and may be 0.35% by mass or less. By ensuring that the content is equal to or less than the upper limit, a decrease in the fluidity of the resin composition when melted can be suppressed. In this embodiment, the resin composition may contain only one type of SWCNT, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0028] The resin composition preferably contains substantially no conductive materials other than SWCNTs. This configuration makes it possible to more effectively prevent a decrease in the fluidity of the resin composition when melted. "Substantially containing no conductive materials other than SWCNTs" means, for example, that the content of conductive materials other than SWCNTs in the resin composition is 10% by mass or less of the SWCNT content, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. The resin composition is also preferably substantially free of MWCNTs, which means, for example, that the content of MWCNTs in the resin composition is 10% by mass or less of the content of SWCNTs, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0029] In the resin composition of this embodiment, the mass ratio of the SWCNT content to the reinforcing material, SWCNT / reinforcing material, is preferably 0.0015 to 0.0500. By making the ratio equal to or greater than the lower limit, antistatic properties tend to be further improved. Meanwhile, by making the ratio equal to or less than the upper limit, fluidity during melting tends to be further improved. The SWCNT / reinforcement ratio is preferably 0.0030 or more, more preferably 0.0045 or more, even more preferably 0.0050 or more, and even more preferably 0.0060 or more. The SWCNT / reinforcement ratio is preferably 0.0400 or less, more preferably 0.0300 or less, even more preferably 0.0200 or less, and even more preferably 0.0150 or less.

[0030] <Other additives> The resin composition of this embodiment may contain other components in addition to those described above. Examples of other components include thermoplastic resins other than polyamide resins, light stabilizers, heat stabilizers, mold release agents, alkalis, elastomers, titanium oxide, antioxidants, hydrolysis resistance improvers, delustering agents, UV absorbers, nucleating agents, plasticizers, dispersants, antistatic agents, coloring inhibitors, antigelling agents, flame retardants, and colorants. For details, see paragraphs

[0130] to

[0155] of Japanese Patent No. 4,894,982, the contents of which are incorporated herein by reference. The total amount of these components is preferably 20% by mass or less of the resin composition, more preferably 10% by mass or less, and even more preferably 5% by mass or less. Each of these components may be used alone, or two or more may be used in combination. The contents of the polyamide resin, reinforcing material, SWCNTs, and other additives added as needed are adjusted so that the total of each component in the resin composition is 100% by mass. The total of the polyamide resin, reinforcing material, and SWCNTs in the resin composition preferably accounts for 90% by mass or more of the resin composition, more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0031] <Method of manufacturing resin composition> As a method for producing the resin composition of the present embodiment, any method can be adopted. In one embodiment of the method for producing the resin composition of the present embodiment, SWCNTs, a reinforcing material, and other components that are added as needed are preferably blended with a polyamide resin and kneaded together. An example of such a resin composition is pellets. Specifically, the polyamide resin, SWCNTs, and reinforcing material, as well as other components added as needed, are premixed using a mixer such as a tumbler or a Henschel mixer, and then melt-kneaded using a mixer such as a Banbury mixer, a roll, a Brabender mixer, a single-screw kneading extruder, a twin-screw kneading extruder, or a kneader. The reinforcing material is preferably side-fed.

[0032] In this embodiment, the SWCNTs are preferably derived from masterbatched single-walled carbon nanotubes, i.e., in this embodiment, the SWCNTs are preferably blended in the form of a masterbatch. The thermoplastic resin to be used for making the masterbatch is preferably a polyamide resin, and more preferably the same resin as the polyamide resin contained in the resin composition in the largest amount. The concentration of the thermoplastic resin in the masterbatch is preferably 99.9% by mass or less, and more preferably 99.5% by mass or less, and is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 75% by mass or more. By adjusting the concentration within the above range of the upper limit or less and the lower limit or more, the dispersibility of the SWCNTs in the thermoplastic resin tends to be further improved.

[0033] The resin composition may be prepared by adding SWCNTs to the polyamide resin during synthesis. This allows the SWCNTs to be dispersed more effectively in the polyamide resin. When SWCNTs are added during synthesis of the polyamide resin, the resulting SWCNT-containing polyamide resin may be used as is as the resin composition of this embodiment, or the resulting SWCNT-containing polyamide resin may be used as a masterbatch of SWCNTs and then melt-kneaded with the polyamide resin or the like. That is, an example of a method for producing the resin composition of this embodiment is a method that includes melt-kneading a polyamide resin, a reinforcing material, and masterbatched SWCNTs, and the content of the single-walled carbon nanotubes in the resin composition is 0.01 to 1.0 mass%. Furthermore, the method for producing the resin composition of this embodiment preferably includes adding SWCNTs during the synthesis of the polyamide resin to produce a masterbatch of single-walled carbon nanotubes.

[0034] <Physical properties of resin composition> The resin composition of this embodiment is preferably used as an antistatic material. Specifically, when the resin composition of this embodiment is molded into a dumbbell piece in accordance with ISO 527, the surface resistivity is 1.0×10 10 Ω / sq. or less is preferable, and 1.0×10 9 Ω / sq. or less is more preferable, and 1.0×10 8 The lower limit of the surface resistivity is preferably 1.0×10 2 It is preferable that the surface roughness is 1.0×10 Ω / sq. or more. In particular, for antistatic films, it is preferable that the surface roughness is 1.0×10 5 It is preferable that the resistance is Ω / sq. or more. The surface resistivity is measured as described in the Examples section below.

[0035] <Molded products> The molded article of this embodiment is formed from the resin composition of this embodiment. The method for producing the molded article of this embodiment is not particularly limited. For example, the molded product of this embodiment may be obtained by melt-kneading the components and then directly molding them using various molding methods, or by melt-kneading the components and pelletizing them, then melting them again and molding them using various molding methods.

[0036] The method for molding the molded article 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, blow molding, gas-assisted blow molding, blow molding, extrusion blow molding, IMC (in-mold coating molding), rotational molding, multilayer molding, two-color molding, insert molding, sandwich molding, foam molding, pressure molding, etc. The resin composition of this embodiment is particularly suitable for molding methods that use a mold, such as injection molding.

[0037] The shape of the molded article of the present embodiment is not particularly limited and can be appropriately selected depending on the use and purpose of the molded article. Examples include plate-like, plate-like, rod-like, sheet-like, film-like, cylindrical, ring-like, circular, elliptical, gear-like, polygonal, irregular-shaped, hollow, frame-like, box-like, and panel-like shapes.

[0038] The application fields of the molded product of this embodiment are not particularly limited, and it can be widely used in automobile and other transportation vehicle parts, general machine parts, precision machine parts, electronic and electrical equipment parts, office automation equipment parts, building materials and housing related parts, medical devices, leisure and sporting goods, play equipment, medical supplies, daily commodities such as food packaging films, defense and aerospace products, etc. The molded article of this embodiment is preferably used as an antistatic film. [Example]

[0039] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, 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.

[0040] 1. Raw materials MXD6: Polyamide resin obtained by polycondensation of metaxylylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, Inc., S6007 PA66: Polyamide 66, manufactured by Toray Industries, Inc., product number: 3001-N SWCNT: Single-walled carbon nanotube, Zeon Corporation, SG101 MWCNT: Multi-walled carbon nanotubes, manufactured by Arkema, Graphistrength GF: Glass fiber, Nippon Electric Glass Co., Ltd., T-275H

[0041] 2. Preparation of masterbatch <Adjustment of Masterbatch MB-1> A 3L reactor equipped with a stirrer, nitrogen gas inlet, and condensation water outlet was charged with 730.8g of adipic acid, 0.6322g of sodium hypophosphite monohydrate, and 0.4404g of sodium acetate. After thoroughly purging the atmosphere with nitrogen, the mixture was melted at 170°C while supplying nitrogen gas at 20ml / min. The temperature was gradually raised to 250°C, and a diamine mixture containing 681.0g of metaxylylenediamine (MXDA) (Mitsubishi Gas Chemical Company, Inc.) and 14.1g of SWCNTs was added dropwise. Polymerization was continued for approximately 2 hours to obtain Masterbatch MB-1 (SWCNT content 1.0% by mass). The resulting polyamide had a relative viscosity (ηr) of 2.2 and a melting point (Tm) of 237.4°C.

[0042] <Adjustment of Masterbatch MB-2> MXD6 (Mitsubishi Gas Chemical Company, Inc., S6007) was dry-blended with SWCNT at a mass ratio of 99:1, and then the mixture was fed into a twin-screw extruder (Shibaura Machine Co., Ltd., TEM26SS) from the base of the screws using a twin-screw cassette weighing feeder (Kubota Corporation, CE-W-1-MP) and melt-kneaded to obtain masterbatch MB-2 (MXD6 / SWCNT content 1.0 mass%). The extruder temperature was set to 260°C.

[0043] <Adjustment of Masterbatch MB-3> MXD6 (Mitsubishi Gas Chemical Company, Inc., S6007) was dry-blended with MWCNT at a mass ratio of 80:20, and then the mixture was added to the base of the screws of a twin-screw extruder (Shibaura Machine Co., Ltd., TEM26SS) using a twin-screw cassette weighing feeder (Kubota Corporation, CE-W-1-MP) and melt-kneaded to obtain masterbatch MB-3 (MXD6 / MWCNT content 20% by mass). The extruder temperature was set to 260°C.

[0044] <Adjustment of Masterbatch MB-4> PA66 (Toray Industries, Inc., 3001-N) was dry-blended with SWCNTs at a mass ratio of 99:1, then the mixture was added to a twin-screw extruder (Shibaura Machine Co., Ltd., TEM26SS) at the base of the screws using a twin-screw cassette weighing feeder (Kubota, CE-W-1-MP) and melt-kneaded to obtain masterbatch MB-4 (PA66 / SWCNT content 1.0 mass%). The extruder temperature was set to 280°C.

[0045] <Adjustment of Masterbatch MB-5> PA66 (Toray Industries, Inc., 3001-N) was dry-blended with MWCNT in a mass ratio of 80:20, then the mixture was added to the base of the screws of a twin-screw extruder (Shibaura Machine Co., Ltd., TEM26SS) using a twin-screw cassette weighing feeder (Kubota, CE-W-1-MP) and melt-kneaded to obtain masterbatch MB-5 (PA66 / MWCNT content 20% by mass). The extruder temperature was set to 280°C.

[0046] 3. Examples 1 to 7, Comparative Examples 1 to 8, Reference Examples 1 to 3 <Compound> The components other than the reinforcing material (glass fiber) were weighed and dry-blended to obtain the compositions shown in Tables 1 to 3 below. The components were then fed into a twin-screw extruder (Shibaura Machine Co., Ltd., TEM26SS) from the base of the screw using a twin-screw cassette weighing feeder (Kubota Corporation, CE-W-1-MP). The glass fiber was fed into the twin-screw extruder from the side using a vibrating cassette weighing feeder (Kubota Corporation, CE-V-1B-MP). The glass fiber was melt-kneaded with the resin components and other ingredients to obtain resin composition pellets. The extruder temperature was set to 280°C when MXD6 was used as the polyamide resin, and 280°C when PA66 was used as the polyamide resin.

[0047] <Flexural strength and flexural modulus> The pellets obtained by the above manufacturing method were dried at 120°C for 4 hours, and then injection-molded into ISO tensile test specimens (4 mm thick) using an injection molding machine (Shibaura Machine Co., Ltd., "EC75SX") under conditions of a cylinder temperature of 300°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 at a temperature of 23°C in accordance with ISO178.

[0048] <Tensile modulus and tensile strength> The pellets obtained by the above manufacturing method were dried at 120°C for 4 hours, and then injection-molded into dumbbell pieces in accordance with ISO 527 using an injection molding machine (Shibaura Machine Co., Ltd., "EC75SX") under conditions of a cylinder temperature of 300°C, a mold temperature of 130°C, and a molding cycle of 50 seconds. In accordance with ISO527, the tensile modulus (unit: GPa) and tensile breaking strength (unit: MPa) were measured using the above dumbbell specimens.

[0049] <Antistatic property evaluation> The surface resistance value (unit: Ω / sq.) was measured using the dumbbell specimen obtained above. For the measurement, a surface resistance meter ST-4 manufactured by SIMCO was used.

[0050] <Spiral flow length> Using a mold (1 mm thick, 6 mm wide), molding was performed under conditions of a cylinder temperature of 250°C, a mold temperature of 80°C, and an injection pressure of 168 MPa. The flow length was measured when molding was performed under these conditions. To evaluate fluidity, the spiral flow length (unit: mm) of the resin composition was measured using an injection molding machine (Japan Steel Works, Ltd., "J55-60H"). Specifically, the pellets obtained above were dried at 120°C for at least 4 hours, and then the following conditions were used: injection pressure of 98 MPa, injection speed of 40 mm / sec, cylinder temperature of 270°C, injection time of 7 sec, intermediate time of 3 sec, cooling time of 18 sec, mold temperature of 130°C, weight of 60 mm, and screw rotation speed of 100 rpm. The mold used had a resin injection port at the center, and a spiral curved groove of Archimedean spiral with a constant groove spacing starting from the injection port. The larger the spiral flow length (unit: mm), the better the fluidity.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] As is clear from the above results, the resin composition of the present invention has high mechanical strength when molded into a molded article, has excellent antistatic properties, and can effectively suppress a decrease in fluidity when melted.

Claims

1. A resin composition comprising a polyamide resin, a reinforcing material, and single-walled carbon nanotubes, The content of the single-walled carbon nanotubes is 0.01 to 1.0% by mass relative to the resin composition, 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; A resin composition in which 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 9 carbon atoms.

2. 2. The resin composition according to claim 1, wherein 70 mol % or more of the xylylenediamine is metaxylylenediamine.

3. The resin composition according to claim 1 or 2, wherein the reinforcing material comprises at least one of glass fiber and carbon fiber.

4. The resin composition according to any one of claims 1 to 3, wherein the content of the reinforcing material in the resin composition is 15 to 60 mass%.

5. The mass ratio of the content of the single-walled carbon nanotubes to the content of the reinforcing material, single-walled carbon nanotubes / reinforcing material, is 0.0015 to 0.0500. The resin composition according to any one of claims 1 to 4.

6. The resin composition according to any one of claims 1 to 5, wherein the single-walled carbon nanotubes are derived from masterbatched single-walled carbon nanotubes.

7. 7. The resin composition according to claim 6, wherein the masterbatch of single-walled carbon nanotubes is obtained by adding single-walled carbon nanotubes to a polyamide resin during synthesis thereof.

8. A molded article formed from the resin composition according to any one of claims 1 to 7.

9. A method for producing the resin composition according to any one of claims 1 to 7, A method for producing a resin composition, comprising melt-kneading a polyamide resin, a reinforcing material, and masterbatched single-walled carbon nanotubes, wherein the content of the single-walled carbon nanotubes in the resin composition is 0.01 to 1.0 mass%.

10. The method for producing a resin composition according to claim 9, comprising adding single-walled carbon nanotubes during synthesis of the polyamide resin to produce a masterbatch of single-walled carbon nanotubes.

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