Polyamide composition and molded body

Abstract

Provided is a polyamide composition which contains a crystalline polyamide (A), glass fibers (B) and an inorganic filler (C). The crystalline polyamide (A) includes diamine units. 60 mol% or more of the diamine units are diamine units having 7-13 carbon atoms. The content of the glass fibers (B) is not less than 37 mass% and less than 45 mass% of the polyamide composition. The glass fibers (B) include glass fibers (B-1) having an average aspect ratio Z1 of 1.1 or more. The content of the inorganic filler (C) is not more than 4 mass% of the polyamide composition. The density of a test piece comprising the polyamide composition is not more than 1.52 g / cm3.

Description

Polyamide composition and molded article

[0001] The present invention relates to a polyamide composition and a molded article made of the polyamide composition.

[0002] It is known that polyamides are used in automotive cooling parts, etc. For example, Patent Document 1 describes a heat exchanger for an intercooler that includes a resin part made of a glass fiber-reinforced resin material, characterized in that the resin part is made of a resin composition containing 1 to 250 parts by weight of glass fibers (B) per 100 parts by weight of thermoplastic resin (A), where the longest width in the cross section of the glass fiber is the major axis, the longest width in the direction perpendicular to the major axis is the minor axis, and the ratio of the long axis to the minor axis is the irregularity ratio. Patent Document 1 also describes a heat exchanger for an intercooler that contains 30 to 100 parts by weight of polyamide (a1) per 100 parts by weight of the thermoplastic resin (A).

[0003] Patent Document 2 describes a polyamide resin composition containing 45 to 120 parts by mass of an inorganic fibrous reinforcing material (B), 25 to 40 parts by mass of a specific phosphinate (C), and 2 to 15 parts by mass of a phosphite (D) relative to 100 parts by mass of polyamide (A), wherein the polyamide (A) contains dicarboxylic acid units and diamine units, the dicarboxylic acid units are mainly units derived from terephthalic acid, and the diamine units are mainly units derived from at least two aliphatic diamines having 8 to 12 carbon atoms, the inorganic fibrous reinforcing material (B) is at least one selected from glass fibers having a circular or non-circular cross section, the sum of the phosphinate (C) and the phosphite (D) is 16 to 25% by mass relative to the polyamide resin composition, and the mass ratio (C) / (D) of the phosphinate (C) to the phosphite (D) is 70 / 30 to 94 / 6.

[0004] JP 2011-137563 A International Publication No. 2021 / 106888

[0005] In recent years, more precise cooling control has been required than ever before to improve power consumption and fuel economy. Accordingly, high dimensional accuracy is also required for automotive cooling parts. Furthermore, because these parts are exposed to water, they are required to maintain their dimensions even when absorbing water, i.e., to exhibit high dimensional stability after water absorption. Furthermore, the increase in vehicle weight due to electrification has further increased the demand for weight reduction. When polyamides such as polyhexamethylene terephthalamide (PA6T) are used for automotive cooling parts, they have a low mold shrinkage rate but a large dimensional change rate upon water absorption. On the other hand, when crystalline polyamides containing a crystalline polyamide containing aliphatic diamine units having 7 to 13 carbon atoms or diamine units having 7 to 13 carbon atoms, such as metaxylenediamine, as the diamine are used as the main component, they exhibit high dimensional stability after water absorption due to their low water absorption, but have a relatively large mold shrinkage rate. Patent Documents 1 and 2 do not disclose specific techniques for solving this problem.

[0006] The present invention aims to provide a polyamide composition that is excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength and light weight, even when a crystalline polyamide containing a diamine unit having 7 to 13 carbon atoms is used as the diamine, and a molded article made of the polyamide composition.

[0007] As a result of intensive research to solve the above problems, the present inventors have conceived the following invention and found that the above problems can be solved.

[0008] [1] A polyamide composition containing a crystalline polyamide (A), a glass fiber (B), and an inorganic filler (C), wherein the crystalline polyamide (A) contains diamine units, and 60 mol% or more of the diamine units are diamine units having 7 to 13 carbon atoms, the content of the glass fiber (B) in the polyamide composition is 37 mass% or more and less than 45 mass%, the glass fiber (B) contains glass fiber (B-1) having an average deformation ratio Z1 of 1.1 or more in a cross section perpendicular to the longitudinal direction, the content of the inorganic filler (C) in the polyamide composition is 4 mass% or less, and a test piece made of the polyamide composition has a density of 1.52 g / cm ３a polyamide composition having an average irregularity ratio Z1 of 1.2 or more and 6 or less; [2] The polyamide composition according to the above item [1], wherein the glass fiber (B-1) has an average irregularity ratio Z1 of 1.2 or more and 6 or less; [3] The polyamide composition according to the above item [1] or [2], wherein the glass fiber (B) further comprises a glass fiber (B-2) having an average irregularity ratio Z2 of less than 1.1 in a cross section perpendicular to the longitudinal direction; [4] The polyamide composition according to the above item [3], wherein the glass fiber (B-2) has an average fiber diameter of 4 μm or more and 15 μm or less; [5] The polyamide composition according to the above item [3] or [4], wherein, when the polyamide composition contains m types of the glass fiber (B-1) and n types of the glass fiber (B-2), the glass fiber (B-1) and the glass fiber (B-2) satisfy the following relational expression (1): 0.03≦ΣM2i / Σ(M1k×Z1k)≦1.0 (1) [In the formula (1), M2i is the mass of the i-th glass fiber (B-2) among the glass fibers (B-2), M1k is the mass of the k-th glass fiber (B-1) among the glass fibers (B-1), Z1k is the average modification ratio Z1 of the k-th glass fiber (B-1) among the glass fibers (B-1), i is an integer of 1 or more and its maximum value is m, and k is an integer of 1 or more and its maximum value is n.] [6] The polyamide composition according to any one of the above [1] to [5], wherein the crystalline polyamide (A) contains dicarboxylic acid units, and 50 mol % or more of the dicarboxylic acid units are structural units derived from at least one selected from terephthalic acid and naphthalenedicarboxylic acid. [7] The polyamide composition according to any one of [1] to [6] above, wherein the diamine units comprise structural units derived from at least one aliphatic diamine compound selected from 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, and 1,12-dodecanediamine. [8] The polyamide composition according to [7] above, wherein the aliphatic diamine compound is at least one selected from 1,9-nonanediamine and 2-methyl-1,8-octanediamine.[9] The polyamide composition according to any one of [1] to [8] above, wherein a test piece made of the polyamide composition has a tensile strength of 190 MPa or more.

[10] The polyamide composition according to any one of [1] to [9] above, wherein a test piece made of the polyamide composition, measuring 60 mm wide, 60 mm deep, and 2 mm thick, has a sum (S(MD) + S(TD)) of the mold shrinkage in the machine direction S(MD) and the mold shrinkage in the transverse direction S(TD) of 0.9% or less.

[11] The polyamide composition according to any one of [1] to

[10] above, wherein a test piece made of the polyamide composition, measuring 60 mm wide, 60 mm deep, and 2 mm thick, has a sum (Si(MD) + Si(TD)) of the dimensional change in the machine direction Si(MD) and the dimensional change in the transverse direction Si(TD) of 0.4% or less before and after immersion in water at 80°C for 500 hours.

[12] The polyamide composition according to any one of the above [1] to

[11] , wherein a test piece made of the polyamide composition and having a width of 60 mm, a depth of 60 mm and a thickness of 2 mm has a mold shrinkage ratio S(TD) in the TD direction and a mold shrinkage ratio S(MD) in the MD direction of 0.45% or less (S(TD) - S(MD)).

[13] A molded article made of the polyamide composition according to any one of the above [1] to

[12] .

[0009] According to the present invention, even when a crystalline polyamide containing a diamine unit having 7 to 13 carbon atoms is used as the diamine, it is possible to provide a polyamide composition that is excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength and light weight, and a molded article made of the polyamide composition.

[0010] FIG. 1 is a diagram showing a typical example of the cross section of a typical glass fiber, in which FIG. 1( a) shows an example in which the outer shape of the cross section is cocoon-shaped, FIG. 1( b) shows an example in which the outer shape of the cross section is elliptical, and FIG. 1( c) shows an example in which the outer shape of the cross section is rectangular.

[0011] The following describes an example of an embodiment of the present invention (hereinafter, sometimes referred to as "this embodiment"). However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. Furthermore, although preferred embodiments are shown in this specification, combinations of two or more of the individual preferred embodiments are also preferred. For matters indicated as numerical ranges, when there are several numerical ranges, the lower and upper limits can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." Furthermore, in this specification, "units" (where "~" indicates a monomer) mean "structural units derived from ~," for example, "dicarboxylic acid units" mean "structural units derived from dicarboxylic acids," and "diamine units" mean "structural units derived from diamines."

[0012] [Polyamide composition] The polyamide composition according to this embodiment is a polyamide composition containing a crystalline polyamide (A), a glass fiber (B), and an inorganic filler (C), wherein the crystalline polyamide (A) contains diamine units, and 60 mol% or more of the diamine units are diamine units having 7 to 13 carbon atoms, the content of the glass fiber (B) in the polyamide composition is 37 mass% or more and less than 45 mass%, the glass fiber (B) contains glass fiber (B-1) having an average deformation ratio Z1 of 1.1 or more in a cross section perpendicular to the longitudinal direction, the content of the inorganic filler (C) in the polyamide composition is 4 mass% or less, and a density of a test piece made of the polyamide composition is 1.52 g / cm ３ The polyamide composition is as follows:

[0013] The polyamide composition according to this embodiment has excellent dimensional accuracy and dimensional stability after water absorption, as well as excellent strength and light weight, even when a crystalline polyamide containing a diamine unit having 7 to 13 carbon atoms is used as the diamine. Although the details of the reason for this are unknown, it is thought that the magnitude of the molding shrinkage rate derived from the crystalline polyamide (A) may be suppressed by blending a specific glass fiber (B-1) and an inorganic filler (C) in an optimal ratio.

[0014] <Crystalline Polyamide (A)> The crystalline polyamide (A) according to this embodiment is a crystalline polyamide containing diamine units, of which 60 mol % or more are diamine units having 7 to 13 carbon atoms.

[0015] The crystalline polyamide (A) according to this embodiment is crystalline, resulting in a polyamide composition with low water absorption and therefore high dimensional stability after water absorption. Furthermore, the crystalline polyamide (A) according to this embodiment has at least 60 mol% of its total diamine units being diamine units having 7 to 13 carbon atoms, resulting in a polyamide composition with excellent heat resistance, chemical resistance, and light weight. Here, "crystalline" means that the heat of fusion (ΔH) measured by differential scanning calorimetry (DSC) at a heating rate of 10°C / min is 10 to 90 J / g. When the heat of fusion (ΔH) of the crystalline polyamide (A) is 10 J / g or more, the water absorption is low, thereby preventing a decrease in dimensional stability after water absorption. Furthermore, when the heat of fusion (ΔH) is greater than 90 J / g, difficulties in melt molding are prevented. From this viewpoint, the heat of fusion (ΔH) is preferably 20 to 85 J / g, more preferably 30 to 80 J / g, even more preferably 40 to 75 J / g, and still more preferably 42 to 75 J / g. Specifically, the heat of fusion (ΔH) is preferably obtained by the method described in the Examples.

[0016] (Dicarboxylic Acid Unit) The crystalline polyamide (A) according to this embodiment contains a dicarboxylic acid unit. Examples of the dicarboxylic acid unit include aromatic dicarboxylic acid units such as terephthalic acid units, naphthalenedicarboxylic acid units, isophthalic acid units, 1,4-phenylenedioxydiacetic acid units, 1,3-phenylenedioxydiacetic acid units, diphenic acid units, diphenylmethane-4,4'-dicarboxylic acid units, diphenylsulfone-4,4'-dicarboxylic acid units, and 4,4'-biphenyldicarboxylic acid units. Examples of the naphthalenedicarboxylic acid unit include units derived from 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid, with the 2,6-naphthalenedicarboxylic acid unit being preferred.

[0017] Examples of the dicarboxylic acid unit include units derived from aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, dimethylmalonic acid, 2,2-diethylsuccinic acid, 2,2-dimethylglutaric acid, 2-methyladipic acid, trimethyladipic acid, and dimer acid; and alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, cycloheptanedicarboxylic acid, cyclooctanedicarboxylic acid, and cyclodecanedicarboxylic acid. Only one type of unit derived from these dicarboxylic acids may be contained, or two or more types may be contained.

[0018] The crystalline polyamide (A) according to this embodiment preferably contains at least one selected from terephthalic acid units and naphthalenedicarboxylic acid units in an amount of 50 mol% or more relative to the total dicarboxylic acid units. In addition, from the viewpoint of obtaining a polyamide with good chemical resistance and heat resistance, the polyamide used in the present invention preferably contains at least one selected from terephthalic acid units and naphthalenedicarboxylic acid units in an amount of 75 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% relative to the total dicarboxylic acid units.

[0019] The crystalline polyamide (A) according to this embodiment preferably contains 50 mol% or more of terephthalic acid units relative to the total dicarboxylic acid units. In order to obtain a polyamide with good chemical resistance and heat resistance, the polyamide used in the present invention preferably contains 75 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% of terephthalic acid units relative to the total dicarboxylic acid units.

[0020] (Diamine Unit) The crystalline polyamide (A) according to this embodiment contains a diamine unit. Examples of the diamine unit include units derived from linear aliphatic diamines such as 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, and 1,13-tridecanediamine; branched aliphatic diamines such as 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, 2-methyl-1,8-octanediamine, and 5-methyl-1,9-nonanediamine; alicyclic diamines such as methylcyclohexanediamine and isophoronediamine; and aromatic diamines such as p-phenylenediamine, m-phenylenediamine, xylylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl ether. It can contain one or more of these.

[0021] In the crystalline polyamide (A) according to this embodiment, 60 mol % or more of the diamine units are diamine units having 7 to 13 carbon atoms. The diamine units described above can be used as the diamine units having 7 to 13 carbon atoms. When 60 mol % or more of the diamine units are diamine units having 7 to 13 carbon atoms, a polyamide composition having excellent heat resistance, chemical resistance, and light weight can be obtained. In the crystalline polyamide (A) according to this embodiment, the content of diamine units having 7 to 13 carbon atoms relative to the total diamine units is more preferably 75 mol % or more, even more preferably 90 mol % or more, and even more preferably 100 mol %. Here, the diamine units having 7 to 13 carbon atoms are preferably aliphatic diamine units or metaxylylenediamine units having 7 to 13 carbon atoms. Examples of the aliphatic diamine units having 7 to 13 carbon atoms include the linear aliphatic diamines and branched aliphatic diamines described above.

[0022] The crystalline polyamide (A) according to this embodiment preferably contains 60 mol% or more of aliphatic diamine units or metaxylylenediamine units having 7 to 13 carbon atoms relative to the total diamine units. Using a crystalline polyamide (A) containing the above-mentioned proportions of aliphatic diamine units or metaxylylenediamine units having 7 to 13 carbon atoms results in a polyamide composition with excellent heat resistance, chemical resistance, and light weight. The crystalline polyamide (A) according to this embodiment preferably contains 75 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% of aliphatic diamine units having 7 to 13 carbon atoms relative to the total diamine units. The crystalline polyamide (A) according to this embodiment preferably contains 60 mol% or more, more preferably 75 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% of aliphatic diamine units having 7 to 13 carbon atoms relative to the total diamine units.

[0023] The aliphatic diamine unit having 7 to 13 carbon atoms is more preferably a unit derived from at least one aliphatic diamine selected from the group consisting of 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, and 1,12-dodecanediamine. Since a polyamide composition having even more excellent heat resistance, low water absorbency, and chemical resistance can be obtained, the aliphatic diamine units having 7 to 13 carbon atoms are more preferably units derived from at least one aliphatic diamine selected from the group consisting of 1,9-nonanediamine, 2-methyl-1,8-octanediamine, and 1,10-decanediamine, even more preferably units derived from at least one aliphatic diamine selected from 1,9-nonanediamine and 2-methyl-1,8-octanediamine, and even more preferably 1,9-nonanediamine units and 2-methyl-1,8-octanediamine units. When the aliphatic diamine units contain both 1,9-nonanediamine units and 2-methyl-1,8-octanediamine units, the molar ratio of 1,9-nonanediamine units to 2-methyl-1,8-octanediamine units, 1,9-nonanediamine units / 2-methyl-1,8-octanediamine units, is preferably in the range of 95 / 5 to 5 / 95, more preferably 90 / 10 to 10 / 90, and even more preferably 85 / 15 to 15 / 85.

[0024] (Aminocarboxylic acid unit and / or lactam unit) The crystalline polyamide (A) according to this embodiment may contain an aminocarboxylic acid unit and / or a lactam unit. Examples of the aminocarboxylic acid unit include units derived from 11-aminoundecanoic acid, 12-aminododecanoic acid, etc. Two or more types of aminocarboxylic acid units may be contained. The content of aminocarboxylic acid units in the polyamide is preferably 50 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, relative to 100 mol% of all monomer units constituting the polyamide.

[0025] Examples of the lactam units include units derived from ε-caprolactam, enantholactam, undecane lactam, lauryllactam, α-pyrrolidone, α-piperidone, etc., and two or more types of lactam units may be contained. The content of lactam units in the polyamide is preferably 50 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, relative to 100 mol% of all monomer units constituting the polyamide.

[0026] (Types of Crystalline Polyamide (A)) In this embodiment, the crystalline polyamide (A) is preferably a semi-aromatic polyamide containing dicarboxylic acid units primarily composed of aromatic dicarboxylic acid units and diamine units primarily composed of aliphatic diamine units having 7 to 13 carbon atoms. In this specification, "primarily composed" refers to 50 to 100 mol%, preferably 60 to 100 mol%, and more preferably 80 to 100 mol% of all units. "Dicarboxylic acid units primarily composed of aromatic dicarboxylic acid units" refers to 50 to 100 mol%, preferably 60 to 100 mol%, and more preferably 80 to 100 mol% of aromatic dicarboxylic acid units in all dicarboxylic acid units. "Diamine units primarily composed of aliphatic diamine units having 7 to 13 carbon atoms" refers to 50 to 100 mol%, preferably 60 to 100 mol%, and more preferably 80 to 100 mol% of aliphatic diamine units having 7 to 13 carbon atoms in all diamine units.

[0027] Representative semi-aromatic polyamides include polynonamethylene terephthalamide (polyamide 9T), poly(2-methyloctamethylene) terephthalamide (polyamide M8T), polynonamethylene terephthalamide / poly(2-methyloctamethylene) terephthalamide copolymer (polyamide 9T / M8T), polynonamethylene naphthalene dicarboxamide (polyamide 9N), polynonamethylene naphthalene dicarboxamide / poly(2-methyloctamethylene) naphthalene dicarboxamide copolymer (polyamide 9N / M8N), polydecamethylene terephthalamide (polyamide 10T), and copolymers of polyamide 10T and polyundecaneamide (polyamide 11) (polyamide 10T / 11), and polydodecamethylene terephthalamide (polyamide 12).

[0028] Among these, at least one selected from the group consisting of polyamide 10T / 11, polynonamethylenenaphthalenedicarboxamide (polyamide 9N), polynonamethylenenaphthalenedicarboxamide / poly(2-methyloctamethylene)naphthalenedicarboxamide copolymer (polyamide 9N / M8N), polynonamethyleneterephthalamide (polyamide 9T), polynonamethyleneterephthalamide / poly(2-methyloctamethylene)terephthalamide copolymer (polyamide 9T / M8T), and polydecamethyleneterephthalamide (polyamide 10T) is preferred, and polynonamethyleneterephthalamide (polyamide 9T), polynonamethylene At least one selected from the group consisting of naphthalene dicarboxamide / poly(2-methyloctamethylene)naphthalene dicarboxamide copolymer (polyamide 9N / M8N), polynonamethylene terephthalamide / poly(2-methyloctamethylene)terephthalamide copolymer (polyamide 9T / M8T), and polyamide 10T is more preferred, and at least one selected from the group consisting of polynonamethylene terephthalamide (polyamide 9T), polynonamethylene terephthalamide / poly(2-methyloctamethylene)terephthalamide copolymer (polyamide 9T / M8T), and polydecamethylene terephthalamide (polyamide 10T) is preferred. From the viewpoints of ensuring moldability and rigidity at high temperatures, polynonamethylene terephthalamide / poly(2-methyloctamethylene)terephthalamide copolymer (polyamide 9T / M8T) is even more preferred.

[0029] The crystalline polyamide (A) may also be a semi-aromatic polyamide containing dicarboxylic acid units primarily composed of aliphatic dicarboxylic acid units and diamine units primarily composed of aromatic diamine units. Examples of the aliphatic dicarboxylic acid units include units derived from the aforementioned aliphatic dicarboxylic acids, and one or more of these may be included. Examples of the aromatic diamine units include units derived from the aforementioned aromatic diamines, and one or more of these may be included. Other units may also be included within the scope of the present invention, provided that they do not impair the effects of the present invention. Representative semi-aromatic polyamides containing dicarboxylic acid units primarily composed of aliphatic dicarboxylic acid units and diamine units primarily composed of aromatic diamine units include polymetaxylylene adipamide (MXD6) and polyparaxylylene sebacamide (PXD10).

[0030] Alternatively, an aliphatic polyamide may be used as the crystalline polyamide (A). Examples of the aliphatic polyamide include polynonamethylene sebacamide (polyamide 910), polynonamethylene dodecamide (polyamide 912), polydecamethylene sebacamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydodecamethylene sebacamide (polyamide 1210), and polydodecamethylene dodecamide (polyamide 1212).

[0031] (End-capping agent) The crystalline polyamide (A) according to this embodiment preferably has 10% or more of the terminal groups of its molecular chain blocked with a terminal-capping agent. Using a crystalline polyamide (A) with a terminal-capping rate of 10% or more results in a polyamide composition with excellent melt stability and excellent strength even after molding. From this perspective, the terminal-capping rate is more preferably 30% or more, even more preferably 50% or more, and even more preferably 55% or more. Furthermore, from the perspective of ensuring compatibility with various compounding agents such as glass fiber, the terminal-capping rate is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, even more preferably 80% or less, even more preferably 75% or less, and even more preferably 70% or less. The terminal-capping rate can be calculated by measuring the number of carboxy groups, amino groups, and structural units derived from the terminal-capping agent that constitute the structural units at the end of the polyamide molecular chain, and then calculating it according to the following formula. The number of each structural unit constituting the end of the polyamide molecule can be calculated, for example, by １ It can be determined based on the integral value of the characteristic signal corresponding to each structural unit calculated by H-NMR.

[0032] Terminal sealing rate (%) = [(Y-Z) / Y] x 100

[0033] [In the formula, Y represents the total number of molecular chain ends of the polyamide, and Z represents the total number of carboxy groups and amino groups. The total number of molecular chain ends of the polyamide, Y, can be calculated, for example, by measuring the molecular weight of the polyamide and multiplying the number of molecular chains derived therefrom. Alternatively, it can be calculated as the total number of constituent units derived from carboxy groups, amino groups, and end-capping agents.] Specifically, the end-capping rate is preferably obtained by the method described in the Examples.

[0034] As the terminal blocking agent, a monofunctional compound reactive with a terminal amino group or a terminal carboxyl group can be used. Specific examples include monocarboxylic acids, acid anhydrides, monoisocyanates, monoacid halides, monoesters, monoalcohols, and monoamines. From the viewpoints of reactivity and the stability of the blocked terminals, monocarboxylic acids are preferred as terminal blocking agents for terminal amino groups, and monoamines are preferred as terminal blocking agents for terminal carboxyl groups. From the viewpoints of ease of handling, monocarboxylic acids are more preferred as terminal blocking agents.

[0035] The monocarboxylic acid used as the terminal blocking agent is not particularly limited as long as it is reactive with an amino group. Examples of the monocarboxylic acid include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclopentanecarboxylic acid and cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid; and mixtures thereof. Among these, at least one selected from acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, and benzoic acid is preferred from the standpoints of reactivity, stability of the blocked terminal, and cost.

[0036] The monoamine used as the terminal blocking agent is not particularly limited as long as it is reactive with a carboxyl group. Examples of the monoamine include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine; and any mixtures thereof. Among these, at least one selected from butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline is preferred in terms of reactivity, high boiling point, stability of the blocked terminal, and cost.

[0037] The content of the dicarboxylic acid unit, diamine unit, and end-capping agent unit in the crystalline polyamide (A) according to this embodiment is preferably 80 to 100 mol%, more preferably 80 to 100 mol%, even more preferably 80 to 100 mol%, and still more preferably 80 to 100 mol%, from the viewpoint of obtaining a polyamide composition that is excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength and lightness.

[0038] <Glass fiber (B)> The polyamide composition according to this embodiment contains glass fiber (B). The glass fiber (B) comprises glass fiber (B-1) having an average irregularity ratio Z1 of 1.1 or more in a cross section perpendicular to the longitudinal direction. Preferably, the glass fiber (B) comprises, together with the glass fiber (B-1), glass fiber (B-2) having an average irregularity ratio Z1 of less than 1.1 in a cross section perpendicular to the longitudinal direction. Next, the glass fiber (B-1) and the glass fiber (B-2) will be described in order.

[0039] (Glass fiber (B-1)) The glass fiber (B-1) is a glass fiber having an average irregularity ratio Z1 of 1.1 or more. The polyamide composition according to this embodiment contains the glass fiber (B-1) having an average irregularity ratio Z1 of 1.1 or more, and therefore has excellent dimensional accuracy, dimensional stability after water absorption, and low warpage.

[0040] The average irregularity ratio in the cross section perpendicular to the longitudinal direction here means the ratio of the major axis to the minor axis (major axis / minor axis) in the cross section perpendicular to the longitudinal direction of the glass fiber. Here, the minor axis means the minimum distance (minimum Feret diameter) between two parallel lines when the cross section is sandwiched from various directions. Here, the major axis means the distance between two parallel lines when the cross section is sandwiched between two parallel lines perpendicular to the minor axis.

[0041] The cross-sectional shape of the glass fiber (B-1) is not particularly limited as long as the average irregularity ratio Z1 of the cross section is 1.1 or more. Examples include an ellipse, a cocoon shape (a shape in which two circles or ellipses are joined via a neck), and a flat (e.g., a rectangle). From the viewpoints of fluidity, mechanical properties, and low warpage, the cocoon shape and the rectangle are preferred. Figure 1 is a diagram schematically showing an example of the cross section of a general glass fiber, where Figure 1(a) shows an example in which the outer shape of the cross section is cocoon-shaped, Figure 1(b) shows an example in which the outer shape of the cross section is elliptical, and Figure 1(c) shows an example in which the outer shape of the cross section is rectangular.

[0042] From the viewpoints of low warpage and mechanical properties, the average irregularity ratio is preferably 1.2 to 10, more preferably 1.2 to 6, even more preferably 1.5 to 6, and even more preferably 1.5 to 4.5. The average irregularity ratio of the glass fiber (B-1) is determined by observing the glass fiber (B-1) with an electron microscope, obtaining a cross-sectional image, and analyzing this image. In the obtained image, the major axis and minor axis of 400 glass fibers (B-1) are identified as shown in FIG. 1. The irregularity ratio is determined by calculating the ratio (major axis / minor axis) from the identified major axis and minor axis. The average irregularity ratio of the 400 fibers is taken as the average irregularity ratio of the glass fiber (B-1). In the case of glass fiber (B-1) contained in a polyamide composition, the polyamide composition is dissolved in an organic solvent to extract the glass fiber (B-1), and the average irregularity ratio of the glass fiber (B-1) can be measured in the same manner as above. The average irregularity ratio of glass fiber (B-2) other than glass fiber (B-1) can also be determined in the same manner. Specifically, the average deformation ratio is preferably obtained by the method described in the Examples.

[0043] From the viewpoints of low warpage and mechanical properties, the average fiber diameter of the glass fiber (B-1) is preferably 15 to 35 μm, more preferably 18 to 32 μm, and even more preferably 19 to 30 μm. Here, the average fiber diameter refers to the major axis. Furthermore, from the viewpoint of compound productivity, the average fiber length of the glass fiber (B-1) is preferably 1 to 10 mm. From this viewpoint, the average fiber length of the glass fiber (B-1) is more preferably 2 to 5 mm, and even more preferably 2.5 to 4 mm. The average fiber length of the glass fiber (B-1) is the average value of the fiber lengths measured for 400 pieces of glass fiber (B-1) observed under an optical microscope. The aspect ratio (L / D) of the average fiber length to the average fiber diameter is usually 50 or more, preferably 60 to 500, more preferably 80 to 200, and even more preferably 100 to 175. The average fiber diameter, average fiber length, and aspect ratio (L / D) of the glass fiber (B-1) are preferably determined by the method described in the Examples.

[0044] (Glass Fiber (B-2)) The glass fiber (B-2) preferably contains, together with the glass fiber (B-1), a glass fiber (B-2) having an average irregularity ratio Z1 of less than 1.1 in a cross section perpendicular to the longitudinal direction. The polyamide composition according to this embodiment contains both the glass fiber (B-1) and the glass fiber (B-2), which makes it less expensive and lighter than a composition containing only the glass fiber (B-1). It also maintains strength, and is excellent in dimensional accuracy, dimensional stability after water absorption, and low warpage. The average fiber diameter of the glass fiber (B-2) is usually about 0.5 to 250 μm. However, from the viewpoint of increasing the contact area with the crystalline polyamide (A) and thereby suppressing a decrease in the mechanical strength of the molded article, it is preferably 3 to 100 μm, more preferably 3 to 30 μm, even more preferably 4 to 15 μm, even more preferably 7 to 15 μm, and particularly preferably 9 to 12 μm. The average fiber length of the glass fiber (B-2) is usually about 0.1 to 10 mm, but from the viewpoint of the high-temperature strength, heat resistance, and mechanical strength of the polyamide composition, it is preferably 0.5 to 5 mm, more preferably 1 to 5 mm, and even more preferably 2 to 4 mm. The aspect ratio (L / D) of the average fiber length to the average fiber diameter is usually 50 or more, preferably 60 to 500, more preferably 80 to 350, even more preferably 100 to 350, and even more preferably 150 to 300. Glass fiber (B-2) having a combination of two or more of these preferred average fiber diameters, average fiber lengths, and aspect ratios is more preferred from the viewpoint of excellent high-temperature strength, heat resistance, mechanical strength, etc. of the polyamide composition. The average fiber diameter and average fiber length of the glass fiber (B-2) can be observed and measured by the same method as for the glass fiber (B-1). The average fiber diameter, average fiber length, and aspect ratio (L / D) of the glass fiber (B-2) are preferably determined specifically by the methods described in the Examples.

[0045] (Ratio of Glass Fiber (B-1) and Glass Fiber (B-2)) When the polyamide composition according to this embodiment contains m types of the glass fiber (B-1) and n types of the glass fiber (B-2), it is preferable that the glass fiber (B-1) and the glass fiber (B-2) satisfy the following relational formula (1). (Hereinafter, "ΣM2i / Σ(M1k×Z1k)" may be expressed as "index 1.") Here, m types and n types are each an integer of 1 or more. Furthermore, m types means the number of types of the glass fiber (B-1). Similarly, n types means the number of types of the glass fiber (B-2). The glass fiber (B-1) and the glass fiber (B-2) are distinguished by their irregularity ratio, and the types of each glass fiber are distinguished by differences in material, size, etc. 0.03≦ΣM2i / Σ(M1k×Z1k)≦1.0 (1) [In the formula (1), M2i is the mass of the i-th glass fiber (B-2) among the glass fibers (B-2), M1k is the mass of the k-th glass fiber (B-1) among the glass fibers (B-1), Z1k is the average irregularity ratio Z1 of the k-th glass fiber (B-1) among the glass fibers (B-1), i is an integer of 1 or greater, with its maximum value being m, and k is an integer of 1 or greater, with its maximum value being n.] This allows for the production of a polyamide composition that exhibits excellent dimensional accuracy and dimensional stability after water absorption, as well as excellent strength and light weight. Furthermore, the index 1 is more preferably 0.05 to 1.0, even more preferably 0.05 to 0.9, and even more preferably 0.05 to 0.8.

[0046] (Inorganic Filler (C)) The inorganic filler (C) is not particularly limited, and known fillers can be used as long as the effects of the present invention are not impaired. Examples of inorganic fillers (C) include glass flakes, talc, kaolin, mica, silicon nitride, hydrotalcite, calcium carbonate, zinc carbonate, titanium oxide, calcium hydrogen phosphate, wollastonite, silica, zeolite, alumina, boehmite, aluminum hydroxide, calcium silicate, sodium aluminosilicate, magnesium silicate, ketjen black, acetylene black, furnace black, carbon nanotubes, graphite, graphene, brass, copper, silver, aluminum, nickel, iron, calcium fluoride, montmorillonite, swellable fluoromica, and apatite. Among the inorganic fillers (C), talc, wollastonite, and calcium carbonate are preferred, and talc is more preferred. These inorganic fillers (C) may be used alone or in combination of two or more.

[0047] (Other Additives) The polyamide composition according to this embodiment may contain other additives as needed in addition to the crystalline polyamide (A), glass fiber (B), and inorganic filler (C). Examples of other additives include stabilizers such as copper compounds; antioxidants such as hindered phenol antioxidants, hindered amine antioxidants, phosphorus antioxidants, and thiol antioxidants; colorants such as carbon black; ultraviolet absorbers; light stabilizers; antistatic agents; flame retardants such as brominated polymers, antimony oxide, metal hydroxides, and phosphinates; flame retardant aids; plasticizers; lubricants; dispersants; oxygen absorbers; hydrogen sulfide adsorbents; mold release agents; organic fibrous fillers such as wholly aromatic polyamide fibers; and impact modifiers such as α-olefin copolymers and rubber.

[0048] (Content of Each Component) The crystalline polyamide (A) is preferably 30 to 63 mass% in the polyamide composition. Within this range, a polyamide composition can be obtained that is excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength and lightness. From this viewpoint, the content of crystalline polyamide (A) in the polyamide composition is more preferably 40 to 63 mass%, even more preferably 50 to 63 mass%, and even more preferably more than 55 mass% but not more than 63 mass%.

[0049] The polyamide composition may contain a crystalline polyamide other than the crystalline polyamide (A), but from the viewpoint of favorably exhibiting the effects of the present invention, it is preferable that the polyamide composition does not contain a crystalline polyamide other than the crystalline polyamide (A). The content of the crystalline polyamide other than the crystalline polyamide (A) in the polyamide composition is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0% by mass.

[0050] The polyamide composition may contain an amorphous polyamide, but from the viewpoint of favorably exhibiting the effects of the present invention, it is preferable that the polyamide composition does not contain an amorphous polyamide. The content of the amorphous polyamide in the polyamide composition is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and still more preferably 0% by mass.

[0051] The content of glass fiber (B) in the polyamide composition is 37% by mass or more but less than 45% by mass. Within this range, a polyamide composition can be obtained that is excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength and light weight. From this viewpoint, the content of glass fiber (B) in the polyamide composition is more preferably 38 to 44% by mass, even more preferably 38 to 43% by mass, and even more preferably 38 to 42% by mass.

[0052] The inorganic filler (C) is contained in the polyamide composition at 4% by mass or less. A content of 4% by mass or less allows for the production of a polyamide composition that exhibits excellent dimensional accuracy and dimensional stability after water absorption, as well as excellent strength and light weight. Furthermore, in order to effectively achieve the effects of the present invention, the inorganic filler (C) is preferably contained in the polyamide composition at 0.01% by mass or more. From these viewpoints, the content of the inorganic filler (C) in the polyamide composition is more preferably 0.01 to 4% by mass, even more preferably 0.02 to 3% by mass, even more preferably 0.04 to 2% by mass, particularly preferably 0.04 to 1% by mass, and even more particularly preferably 0.04 to 0.1% by mass.

[0053] The content of the above-mentioned other additives is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 0.02 to 200 parts by mass, more preferably 0.03 to 100 parts by mass, even more preferably 0.1 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, relative to 100 parts by mass of the crystalline polyamide (A).

[0054] When a flame retardant is included as another additive, the content of the flame retardant in the polyamide composition is preferably 5% by mass or less. At 5% by mass or less, a decrease in the strength of the polyamide composition can be suppressed. From this viewpoint, the content of the flame retardant in the polyamide composition is more preferably 4% by mass or less, even more preferably 3% by mass or less, and even more preferably 1% by mass or less, and may even be 0% by mass.

[0055] The total content of the inorganic filler (C) and the flame retardant in the polyamide composition is preferably 5% by mass or less. At 5% by mass or less, a polyamide composition can be obtained that exhibits excellent dimensional accuracy and dimensional stability after water absorption, as well as excellent strength and light weight. Furthermore, from the viewpoint of effectively achieving the effects of the present invention, the total content of the inorganic filler (C) and the flame retardant in the polyamide composition is preferably 0.01% by mass or more. From these viewpoints, the total content of the inorganic filler (C) and the flame retardant in the polyamide composition is more preferably 0.01 to 4% by mass, even more preferably 0.02 to 3% by mass, even more preferably 0.04 to 2% by mass, particularly preferably 0.04 to 1% by mass, and even more particularly preferably 0.04 to 0.1% by mass.

[0056] The total content of the inorganic filler (C) and other additives in the polyamide composition is preferably 5% by mass or less. At 5% by mass or less, a polyamide composition can be obtained that exhibits excellent dimensional accuracy and dimensional stability after water absorption, as well as excellent strength and light weight. Furthermore, from the viewpoint of effectively achieving the effects of the present invention, the total content of the inorganic filler (C) and other additives in the polyamide composition is preferably 0.01% by mass or more. From these viewpoints, the total content of the inorganic filler (C) and other additives in the polyamide composition is more preferably 0.01 to 5% by mass, even more preferably 0.01 to 4% by mass, even more preferably 0.02 to 2% by mass, and even more preferably 0.04 to 1% by mass.

[0057] (Physical properties of polyamide composition) [Density] The density of a test piece made of the polyamide composition was 1.52 g / cm ３or less. This reduces the weight of the polyamide composition. Reducing the content of glass fiber (B) in the polyamide composition tends to reduce the weight of the polyamide composition. The density is preferably measured in accordance with Method A of ISO1183:2019. The density is preferably greater than 1.41. If the density is greater than 1.41, the content of glass fiber (B), which has a higher density than crystalline polyamide (A), can be increased, and a polyamide composition can be obtained that is excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength, impact resistance, and low warpage. From these viewpoints, the density is preferably 1.41 g / cm ３ Super 1.52g / cm ３ More preferably, it is 1.42 g / cm or less. ３ Super 1.52g / cm ３ or less, and more preferably 1.43 to 1.50 g / cm ３ or less, and even more preferably 1.45 to 1.49 g / cm ３ The test specimen can be obtained by injection molding a polyamide composition. For example, a dumbbell-shaped tensile test specimen (Type A1) prepared in accordance with JIS K7139 (2009) can be used as the test specimen. The test specimen can also be obtained by cutting it out from a polyamide molded product. Specifically, the test specimen is preferably obtained by the method described in the Examples.

[0058] [Tensile Strength] A test specimen made of the polyamide composition preferably has a tensile strength of 190 MPa or more. The polyamide composition has high strength. By including specific amounts of a specific glass fiber (B) and an inorganic filler (C) in the polyamide composition, the reinforcing effects of the glass fiber and the inorganic filler are appropriately exhibited, tending to improve the tensile strength of the polyamide composition. The tensile strength is preferably measured in accordance with ISO 527-1:2019. The tensile strength is preferably 200 MPa or more, more preferably 205 MPa or more, even more preferably 208 MPa or more, and even more preferably 209 MPa or more. The test specimen can be obtained by injection molding the polyamide composition. For example, a dumbbell-shaped tensile test specimen (Type A1) prepared in accordance with JIS K7139 (2009) can be used as the test specimen. The test specimen can also be obtained by cutting out a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0059] [Sum of Mold Shrinkage] The sum (S(MD) + S(TD)) of the mold shrinkage S(MD) in the parallel direction (hereinafter also referred to as MD) and the mold shrinkage S(TD) in the perpendicular direction (hereinafter also referred to as TD) of a test piece made of a polyamide composition, measuring 60 mm wide, 60 mm deep, and 2 mm thick, is preferably 0.9% or less. This polyamide composition has high dimensional accuracy. The inclusion of glass fiber (B) in the polyamide composition tends to reduce this sum (S(MD) + S(TD)). The MD and SD directions of the test piece can be determined from the position of the resin flow, known as the gate of the test piece. The mold shrinkage in each direction can be calculated using the following formula: Mold shrinkage in the parallel direction (MD) S(MD) = (mold dimensions - dimension of test piece in MD) ÷ mold inner dimensions × 100; Mold shrinkage in the perpendicular direction (TD) S(TD) = (mold dimensions - dimension of test piece in TD) ÷ mold inner dimensions × 100. The mold shrinkage in the MD direction S(MD), the mold shrinkage in the TD direction S(TD), and their sum (S(MD) + S(TD)) are preferably measured in accordance with ISO 294-4:2018. Furthermore, this sum (S(MD) + S(TD)) is preferably 0.87% or less, more preferably 0.85% or less, even more preferably 0.83% or less, and even more preferably 0.80% or less. The test piece can be obtained by injection molding a polyamide composition. The test piece can also be obtained by cutting it out of a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0060] [Sum of dimensional change rates after water immersion] For a test piece made of a polyamide composition, 60 mm wide, 60 mm deep, and 2 mm thick, before and after immersion in water at 80°C for 500 hours, the sum of the dimensional change rate in the machine direction Si(MD) and the dimensional change rate in the transverse direction Si(TD) (Si(MD) + Si(TD)) is preferably 0.4% or less. The polyamide composition has high dimensional accuracy after water immersion. By including glass fiber (B) in the polyamide composition, the sum (Si(MD) + Si(TD)) tends to be smaller. The dimensional change rate in each direction can be calculated using the following formula: Dimensional change rate in the MD direction Si(MD) = (MD dimension of the test piece after immersion - MD dimension of the test piece before immersion) ÷ MD dimension of the test piece before immersion × 100 Dimensional change rate in the TD direction Si(TD) = (TD dimension of the test piece after immersion - TD dimension of the test piece before immersion) ÷ TD dimension of the test piece before immersion × 100 The dimensional change rate in the MD direction Si(MD), the dimensional change rate in the TD direction Si(TD), and their sum (Si(MD) + Si(TD)) are preferably measured in accordance with ISO294-4:2018. Furthermore, the sum (Si(MD) + Si(TD)) is preferably 0.35% or less, more preferably 0.32% or less, even more preferably 0.30% or less, and even more preferably 0.29% or less. The test piece can be obtained by injection molding a polyamide composition. Alternatively, the test piece can be obtained by cutting out a polyamide molded article. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0061] [Difference in Mold Shrinkage] The difference (S(TD) - S(MD)) between the mold shrinkage in the TD direction S(TD) and the mold shrinkage in the MD direction S(MD) of a test piece made of a polyamide composition having a width of 60 mm, a depth of 60 mm, and a thickness of 2 mm is preferably 0.45% or less. The polyamide composition has excellent low warpage properties. By including glass fiber (B) in the polyamide composition, the difference (S(TD) - S(MD)) tends to be smaller. The mold shrinkage in each direction can be calculated using the above-mentioned formula. The mold shrinkage in the TD direction S(TD), the mold shrinkage in the MD direction S(MD), and the difference therebetween (S(TD) - S(MD)) are preferably measured in accordance with ISO294-4:2018. The difference (S(TD)-S(MD)) is preferably 0.44% or less, more preferably 0.43% or less, even more preferably 0.42% or less, and even more preferably 0.39% or less. The test piece can be obtained by injection molding the polyamide composition. The test piece can also be obtained by cutting out a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0062] [Charpy impact strength (-40°C)] The Charpy impact strength at -40°C of a test piece (4 mm thick, 80 mm long, 10 mm wide, notched) made of a polyamide composition was 8.0 kJ / m ２ The polyamide composition has excellent impact resistance. By including specific amounts of glass fiber (B) and inorganic filler (C) in the polyamide composition, the impact resistance tends to be improved. The Charpy impact strength at -40°C is preferably measured in accordance with ISO179-1:2010. The Charpy impact strength is preferably 9.0 kJ / m ２ or more, more preferably 10.0 kJ / m ２ or more, more preferably 11.0 kJ / m ２ or more, and even more preferably 11.5 kJ / m ２That's all. The test piece can be obtained by injection molding a polyamide composition. For example, a test piece can be obtained by cutting a dumbbell-shaped tensile test piece (Type A1) prepared in accordance with JIS K7139 (2009) into a length of 80 mm, a width of 10 mm, a thickness of 4 mm, and a notch. Alternatively, the test piece can be obtained by cutting it out from a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0063] [Charpy impact strength (23°C)] The Charpy impact strength of the test piece made of the polyamide composition at 23°C was 12.0 kJ / m ２ The polyamide composition has excellent impact resistance. The impact resistance tends to be improved by including glass fiber (B) in the polyamide composition. The Charpy impact strength at 23°C is preferably measured in accordance with ISO179-1:2010. The Charpy impact strength is preferably 12.3 kJ / m or more. ２ More preferably, 12.5 kJ / m or more. ２ More preferably, it is 12.7 kJ / m or more. ２ or more, and even more preferably 13.0 kJ / m ２ That's all. The test piece can be obtained by injection molding a polyamide composition. For example, a test piece can be obtained by cutting a dumbbell-shaped tensile test piece (Type A1) prepared in accordance with JIS K7139 (2009) into a length of 80 mm, a width of 10 mm, a thickness of 4 mm, and a notch. Alternatively, the test piece can be obtained by cutting it out from a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0064] [Tensile Breaking Elongation] The tensile breaking elongation of a test piece made of a polyamide composition at 23°C, measured in accordance with ISO 527-1:2019, is preferably 1.0 to 300%. A tensile breaking elongation of 1.0% or more results in excellent toughness. The tensile breaking elongation tends to be increased by, for example, adjusting the content of inorganic filler (C) to a range of 0.01 to 4 mass%. Furthermore, the tensile breaking elongation is preferably 1.0 to 200%, more preferably 1.5 to 100%, even more preferably 1.9 to 50%, and even more preferably 2.0 to 30%. The test piece can be obtained by injection molding the polyamide composition. For example, a dumbbell-shaped tensile test piece (Type A1) prepared in accordance with JIS K7139 (2009) can be used. The test piece can also be obtained by cutting it out of a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0065] [Tensile Modulus] The tensile modulus of a test piece made of the polyamide composition, measured in accordance with ISO 527-1:2019 at 23°C, is preferably 9 to 50 GPa. A modulus of 9 GPa or higher can result in a molded product with excellent rigidity. The inclusion of glass fiber (B) or the like tends to increase the tensile modulus. The tensile modulus is preferably 9 to 45 GPa, more preferably 10 to 40 GPa, even more preferably 11 to 35 GPa, and even more preferably 11.5 to 30 GPa. The test piece can be obtained by injection molding the polyamide composition. For example, a dumbbell-shaped tensile test piece (Type A1) prepared in accordance with JIS K7139 (2009) can be used. The test piece can also be obtained by cutting it out of a polyamide molded product. Specifically, the test piece is preferably obtained by the method described in the Examples.

[0066] [Molded Article] The molded article according to this embodiment is made of the polyamide composition according to this embodiment. The molded article can be obtained by molding the polyamide composition according to this embodiment using various molding methods such as injection molding, blow molding, extrusion molding, compression molding, stretch molding, vacuum molding, and foam molding. Furthermore, the molded article according to this embodiment can also be obtained by composite molding of the polyamide composition according to this embodiment with other polymers, etc.

[0067] [Examples of Applications] Examples of the molded articles include gears, cams, various housings, water pumps, thermostat housings, valves, rollers, impellers, bearing retainers, spring holders, clutch parts, chain tensioners, tanks, wheels, connectors, switches, sensors, sockets, capacitors, hard disk components, jacks, fuse holders, relays, coil bobbins, resistors, IC housings, and LED reflectors. In particular, the polyamide composition according to this embodiment is suitable for use in molded articles for automotive applications requiring high chemical resistance, dimensional accuracy, and heat resistance, such as automobile interior and exterior parts, engine compartment parts, cooling system parts, sliding parts, and electrical components. Additionally, the polyamide composition according to this embodiment can be used to form electrical and electronic components, as well as molded articles requiring heat resistance suitable for surface mounting processes. Such molded articles can be suitable for use in surface-mounted connectors, sockets, camera modules, power supply parts, switches, sensors, capacitor base plates, hard disk components, relays, resistors, fuse holders, coil bobbins, IC housings, and other surface-mounted components.

[0068] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0069] The evaluations in the examples and comparative examples were carried out according to the methods shown below.

[0070] 1. Density Measurement (Test Specimen Preparation) Dumbbell-shaped tensile test specimens (Type A1) were prepared in accordance with JIS K 7139 (2009) and used as test specimens. Specifically, using an injection molding machine (clamping force: 100 tons, screw diameter: φ32 mm) manufactured by Sumitomo Heavy Industries, Ltd., a cylinder temperature of 320°C, an actual mold temperature of 140°C, and a T-runner mold at an injection speed of 130 mm / sec, dumbbell-shaped tensile test specimens (Type A1) (4 mm thick, total length 170 mm, parallel portion length 80 mm, parallel portion width 10 mm) were prepared from the resin compositions (pellets) obtained in the Examples and Comparative Examples. (Density Measurement) Test specimens (4 mm thick, total length 80 mm, width 10 mm) were prepared by cutting from the dumbbell-shaped tensile test specimens (Type A1) prepared by the above method. The density of this test piece was measured in accordance with ISO1183:2019A method using an electronic hydrometer (ED-120T, manufactured by Alpha Mirage Co., Ltd.) with water as the immersion liquid.

[0071] 2. Injection Molding Pressure When molding the above dumbbell-shaped tensile test piece (Type A1), the peak filling pressure when molding was performed at an injection speed of 130 mm / sec was measured and this was taken as the injection molding pressure.

[0072] 3. Measurement of Tensile Properties Using the dumbbell-shaped tensile test specimen (Type A1) prepared by the above method, the tensile properties were measured in accordance with ISO 527-1: 2019. Specifically, the tensile properties at 23°C, including tensile strength, tensile elongation at break, and tensile modulus, were measured using an autograph (Instron Corporation, Universal Testing Machine 5969, video extensometer used).

[0073] 4. Impact Resistance Test Test pieces (4 mm thick, 80 mm long, 10 mm wide, notched) were cut from the dumbbell-shaped tensile test pieces (Type A1) prepared by the above method, and tests were carried out in accordance with ISO179-1:2010. Specifically, notched Charpy impact strengths (kJ / m) were measured at 23°C and -40°C using an impact tester (manufactured by Toyo Seiki Seisakusho). ２ ) was measured.

[0074] 5. Measurement of mold shrinkage Using an injection molding machine (clamping force: 100 tons, screw diameter: φ32 mm) manufactured by Sumitomo Heavy Industries, Ltd., in accordance with ISO294-3:2002, a cylinder temperature of 320 ° C., an actual mold temperature of 140 ° C., and an injection speed of 120 mm / sec, the resin compositions (pellets) obtained in the examples and comparative examples were molded into flat plates with a width of 60 mm, a depth of 60 mm, and a height of 2 mm to prepare test specimens. In accordance with ISO294-4:2018, a three-dimensional measuring machine (ZEISS, O-INSPECT322) was used to measure the dimensions in the direction perpendicular to the flow (TD) and the direction parallel to the flow (MD), and each mold shrinkage was calculated. Each mold shrinkage was calculated using the following formula: - Mold shrinkage in each direction = (mold dimension - dimension of each direction of the flat plate) ÷ mold dimension × 100

[0075] 6. Dimensional Change After Water Absorption The flat plate used to measure mold shrinkage was immersed in pure water in a pressure vessel and left to stand in a thermostatic bath set at 80°C for 500 hours. After 500 hours, the flat plate was removed from the pressure vessel and the dimensions in the direction perpendicular to the flow (TD) and the direction parallel to the flow (MD) were measured using a three-dimensional dimension measuring machine, as in the measurement of mold shrinkage, and the dimensional change rates before and after immersion were evaluated using the following formula: Dimensional change rate in each direction (%) = 100 x (flat plate dimension in each direction after 500 hours - flat plate dimension in each direction before immersion) / dimension in each direction before immersion

[0076] 7. Crystallinity of Polyamide The heat of fusion (ΔH) of the polyamide obtained in the Production Examples was measured using a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science Corporation). The heat of fusion (ΔH) was measured in accordance with the method for measuring melting points in ISO 11357-3 (2011, 2nd edition). Specifically, under a nitrogen atmosphere, a sample (polyamide) was heated from 30°C to 340°C at a rate of 10°C / min, held at 340°C for 5 minutes to completely melt the sample, then cooled to 50°C at a rate of 10°C / min and held at 50°C for 5 minutes. The area of ​​the melting peak that appeared when the temperature was again raised to 340°C at a rate of 10°C / min was taken as the heat of fusion (ΔH).

[0077] 8. Terminal Capping Rate of Polyamide The terminal capping rate of polyamide was calculated by measuring the number of carboxyl groups, amino groups, and structural units derived from the terminal capping agent that constitute the structural units at the ends of the polyamide molecular chain, and then calculating it according to the following formula. The number of each structural unit that constitutes the end of the polyamide molecule is: １ The terminal capping rate was determined based on the integrated value of the characteristic signal corresponding to each structural unit calculated by H-NMR: Terminal capping rate (%) = [(Y - Z) / Y] x 100 (where Y represents the total number of molecular chain terminals of the polyamide, and Z represents the total number of carboxyl groups and amino groups).

[0078] <Production Example 1> (Preparation of Crystalline Polyamide A-1) 8091.0 g (48.70 mol) of terephthalic acid, 7969.4 g (50.35 mol) of a mixture of 1,9-nonanediamine and 2-methyl-1,8-octanediamine [former / latter = 80 / 20 (molar ratio)], 354.1 g (2.90 mol) of benzoic acid, 16.2 g of sodium hypophosphite monohydrate (0.1% by mass relative to the total mass of the raw materials), and 8.3 L of distilled water were placed in a 40 L autoclave and purged with nitrogen. The mixture was stirred at 100°C for 30 minutes, and the temperature inside the autoclave was raised to 220°C over 2 hours. At this time, the pressure inside the autoclave rose to 2 MPa. Heating was continued for 5 hours while maintaining the pressure at 2 MPa, and the reaction was allowed to proceed while gradually releasing water vapor. Next, the pressure was reduced to 1.3 MPa over 30 minutes, and the reaction was continued for another hour to obtain a prepolymer. The obtained prepolymer was dried at 100°C under reduced pressure for 12 hours and pulverized to a particle size of 2 mm or less. This was subjected to solid-state polymerization at 230°C and 13 Pa (0.1 mmHg) for 10 hours to obtain a polyamide. The end-capping rate was 63%. This polyamide is abbreviated as "Crystalline Polyamide A-1."

[0079] <Production Example 2> (Preparation of Crystalline Polyamide A'-1) A polyamide was obtained by polymerization in the same manner as for Polyamide A-1, except that 5,850.7 g (50.35 mol) of a mixture of 1,6-hexamethylenediamine and 2-methyl-1,5-pentanediamine [former / latter = 50 / 50 (molar ratio)] was used as the diamine component. The end-capping rate was 65%. This polyamide is abbreviated as "Crystalline Polyamide A'-1".

[0080] Example 1 (Preparation of Polyamide Composition) 60 parts by mass (59.5% by mass) of crystalline polyamide shown in Table 1, 0.06 parts by mass (0.06% by mass) of inorganic filler (C), 0.18 parts by mass (0.18% by mass) of antioxidant, 0.18 parts by mass (0.18% by mass) of release agent, and 0.48 parts by mass (0.48% by mass) of colorant were pre-mixed and fed from the upstream hopper of a twin-screw extruder (twin-screw extruder manufactured by the Plastics Engineering Research Institute, screw diameter φ30 mm, L / D = 32, rotation speed 150 rpm, output rate 10 kg / h), and 40 parts by mass (39.6% by mass) of glass fiber (B) were fed from the downstream side feed port of the extruder. The mixture was melt-kneaded and extruded under conditions of a cylinder temperature of 320 ° C, and then cooled and cut to produce a pellet-shaped resin composition.

[0081] Examples 2 to 12 and Comparative Examples 1 to 8 (Preparation of Polyamide Compositions) A crystalline polyamide, an inorganic filler (C), an antioxidant, a release agent, and a colorant were premixed in the proportions shown in Tables 1 to 3 and fed from the upstream hopper of a twin-screw extruder (twin-screw extruder manufactured by the Plastics Engineering Research Institute, screw diameter φ30 mm, L / D=32, rotation speed 150 rpm, output rate 10 kg / h), and glass fiber (B) was fed from the side feed port on the downstream side of the extruder in the proportions shown in Tables 1 to 3. When multiple types of glass fiber (B) were used, they were premixed and similarly fed from the side feed port. The mixture was melt-kneaded and extruded at a cylinder temperature of 320°C, and then cooled and cut to produce pellet-shaped resin compositions.

[0082] The resin compositions thus obtained were subjected to the above-described evaluations. The value of Index 1 was also calculated. The results are shown in Tables 1 to 3.

[0083] The components shown in Tables 1 to 3 are as follows: [Polyamide (A)] A-1: ​​Polyamide A-1 obtained in Production Example 1 (heat of fusion: 50 J / g) A'-1: Polyamide A'-1 obtained in Production Example 2 (heat of fusion: 39 J / g)

[0084] [Glass fiber (B-1)] B-1-1: Manufactured by Nitto Boseki Co., Ltd., trade name "CSH3PA-870", average irregularity ratio 2.0, non-circular cross-sectional shape (cocoon type), average fiber length: 3 mm, average fiber diameter: 20 μm, aspect ratio: 150 B-1-2: Manufactured by Nitto Boseki Co., Ltd., trade name "CSG3PA-820", average irregularity ratio 4.0, non-circular cross-sectional shape (rectangle), average fiber length: 3 mm, average fiber diameter: 28 μm, aspect ratio: 107 [Glass fiber (B-2)] B-2: Manufactured by Nippon Electric Glass Co., Ltd., trade name "ECS03T-251H", average irregularity ratio 1.0, circular cross-sectional shape, average fiber length: 3 mm, average fiber diameter: 10.5 μm, aspect ratio: 286 The average irregularity ratio, average fiber length, and average fiber diameter of the glass fiber were calculated by the following methods. First, glass fibers were dispersed in water in a petri dish. The average fiber length was determined by observing the glass fibers dispersed in water with an optical microscope to obtain images, and then calculating the average fiber length from the obtained images using image processing software. The average irregularity ratio and average fiber diameter were determined by observing the glass fibers dispersed in water with an electron microscope to obtain cross-sectional images, and then calculating the average irregularity ratio and average fiber diameter from the obtained images using image processing software. Each result was calculated using the average value of 400 fibers.

[0085] [Inorganic filler (C)] Talc: manufactured by Fuji Talc Co., Ltd., trade name "TALC ML112"

[0086] [Antioxidant] Hindered phenol-based antioxidant: manufactured by Sumitomo Chemical Co., Ltd., trade name "SUMILIZER GA-80"

[0087] [Release agent] Release agent: Clariant Chemicals Co., Ltd., product name "LICOWAX OP"

[0088] [Coloring agent] Carbon black: Mitsubishi Chemical Corporation, product name "#980B"

[0089]

[0090]

[0091]

[0092] As is clear from Tables 1 to 3, the polyamide compositions according to the Examples are excellent in dimensional accuracy and dimensional stability after water absorption, as well as in strength and light weight. On the other hand, the polyamide compositions according to the Comparative Examples are inferior in at least one of dimensional accuracy, dimensional stability after water absorption, strength, and light weight.

Claims

1. A polyamide composition containing a crystalline polyamide (A), a glass fiber (B) and an inorganic filler (C), wherein the crystalline polyamide (A) contains a diamine unit, and 60 mol % or more of the diamine unit is a diamine unit having 7 to 13 carbon atoms, the content of the glass fiber (B) in the polyamide composition is 37 mass % or more and less than 45 mass %, the glass fiber (B) contains a glass fiber (B-1) having an average irregularity ratio Z1 of 1.1 or more in a cross section perpendicular to the longitudinal direction, the content of the inorganic filler (C) in the polyamide composition is 4 mass % or less, and a density of a test piece made of the polyamide composition is 1.52 g / cm ３ 1. A polyamide composition, comprising:

2. The polyamide composition according to claim 1, wherein the glass fiber (B-1) has an average irregular shape ratio Z1 of 1.2 or more and 6 or less.

3. The polyamide composition according to claim 1 or 2, wherein the glass fiber (B) further comprises glass fiber (B-2) having an average irregular shape ratio Z2 in a cross section perpendicular to the longitudinal direction of less than 1.

1.

4. The polyamide composition according to claim 3, wherein the average fiber diameter of the glass fibers (B-2) is 4 μm or more and 15 μm or less.

5. The polyamide composition according to claim 3 or 4, wherein, when the polyamide composition contains m types of the glass fiber (B-1) and n types of the glass fiber (B-2), the glass fiber (B-1) and the glass fiber (B-2) satisfy the following relational formula (1): 0.03≦ΣM2i / Σ(M1k×Z1k)≦1.0 (1) (In the formula (1), M2i is the mass of the i-th type of glass fiber (B-2) among the glass fibers (B-2), M1k is the mass of the k-th type of glass fiber (B-1) among the glass fibers (B-1), Z1k is the average irregular shape ratio Z1 of the k-th type of glass fiber (B-1) among the glass fibers (B-1), i is an integer of 1 or more and has a maximum value of m, and k is an integer of 1 or more and has a maximum value of n.) 6. The polyamide composition according to any one of claims 1 to 5, wherein the crystalline polyamide (A) contains dicarboxylic acid units, and 50 mol % or more of the dicarboxylic acid units are structural units derived from at least one selected from terephthalic acid and naphthalenedicarboxylic acid.

7. The polyamide composition according to any one of claims 1 to 6, wherein the diamine units include structural units derived from at least one aliphatic diamine compound selected from 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, and 1,12-dodecanediamine.

8. The polyamide composition according to claim 7, wherein the aliphatic diamine compound is at least one selected from the group consisting of 1,9-nonanediamine and 2-methyl-1,8-octanediamine.

9. The polyamide composition according to any one of claims 1 to 8, wherein a test piece made of the polyamide composition has a tensile strength of 190 MPa or more.

10. The polyamide composition according to any one of claims 1 to 9, wherein the sum of the molding shrinkage rate S(MD) in the MD direction and the molding shrinkage rate S(TD) in the TD direction of a test piece made of the polyamide composition and having a width of 60 mm, a depth of 60 mm and a thickness of 2 mm, (S(MD) + S(TD)), is 0.9% or less.

11. The polyamide composition according to any one of claims 1 to 10, wherein a test piece made of the polyamide composition and having a width of 60 mm, a depth of 60 mm and a thickness of 2 mm has a sum (Si(MD) + Si(TD)) of the dimensional change in the MD direction Si(MD) and the dimensional change in the TD direction Si(TD) of the test piece before and after immersion in water at 80°C for 500 hours of 0.4% or less.

12. The polyamide composition according to any one of claims 1 to 11, wherein a test piece made of the polyamide composition and having a width of 60 mm, a depth of 60 mm and a thickness of 2 mm has a difference (S(TD) - S(MD)) between the mold shrinkage rate S(TD) in the TD direction and the mold shrinkage rate S(MD) in the MD direction of 0.45% or less.

13. A molded article comprising the polyamide composition according to any one of claims 1 to 12.

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