Polyamide composition and molded article

Abstract

The purpose is to provide a polyamide composition capable of avoiding an excessive decrease in adhesiveness (that is, adhesive force) between a molded article and an object on the molded article (for example, a gap filler) that can occur when the molded article is exposed to a high-temperature environment for a long period of time. The polyamide composition contains a polyamide, a fibrous inorganic reinforcing material, and a thermally conductive inorganic filler. The ratio of the peak area of 1750 cm-1 to 1700 cm-1 to the peak area of 1665 cm-1 to 1630 cm-1 in the infrared absorption spectrum when allowed to stand for 1000 hours in a 150°C environment is 0.10 or less. Here, the "infrared absorption spectrum" is the infrared absorption spectrum at a depth of 50 μm from the surface of the molded article when a molded article having an arithmetic average roughness (Ra) of 0.1 μm is molded using the polyamide composition and the molded article is allowed to stand for 1000 hours in a 150°C environment.

Description

Polyamide composition and molded article

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

[0002] Rapidly increasing demand for plastic electronic devices and light-emitting diodes (LEDs), miniaturization of components, and increasing the capacity and lifespan of batteries in battery electric vehicles (BEVs) have made efficient heat dissipation inside electronic devices an important issue.

[0003] One solution is to introduce a gap filler with high heat dissipation properties between heat-generating electrical and electronic components (such as batteries and motors) and housing components. By filling air pockets (i.e., spaces where air does not flow well) and gaps with the gap filler, the heat generated by the electrical and electronic components can be efficiently transferred to surrounding components (such as components around the battery), thereby efficiently dissipating the heat.

[0004] Resin molded products are often considered for battery peripheral components (such as battery cases and battery module base plates) from the perspectives of weight reduction, production cycle, and flexibility in shape. Engineering plastics, especially polyamides with high heat resistance, are often considered as resins.

[0005] Because battery peripheral components require high thermal conductivity, it is common to blend large amounts of inorganic materials with high heat dissipation properties (i.e., inorganic materials with high thermal conductivity) into polyamides. However, polyamide compositions containing a large amount of inorganic material may solidify during injection molding, leaving the inorganic material exposed on the surface. When the inorganic material is glass, this is called glass lift, a type of molding defect (see Patent Document 1 for details on inorganic material lift). This type of molding defect can easily cause gap fillers and other components to peel off when the battery is subjected to strong impact or vibration, potentially resulting in problems (e.g., problems such as misalignment between the battery and battery peripheral components). As a result, air pockets form between the battery and battery peripheral components, which can reduce heat dissipation and shorten the battery's lifespan. Similar concerns apply to peripheral components of electrical and electronic components other than batteries, such as motor peripheral components.

[0006] Patent No. 6518587 Patent No. 6249565 Patent No. 5993824

[0007] Molded articles used as peripheral components of electrical and electronic components (e.g., batteries and motors) in battery electric vehicles (BEVs) tend to be exposed to high-temperature environments for long periods of time. Therefore, molded articles used as peripheral components of electrical and electronic components are required to be able to dissipate heat through gap fillers not only before but also after long-term exposure to high-temperature environments. This requirement is becoming increasingly stronger as battery electric vehicles (BEVs) become more widespread and their performance improves.

[0008] An object of the present invention is to provide a polyamide composition that can prevent an excessive decrease in adhesion (i.e., adhesive strength) between a molded article and an object (e.g., a gap filler) placed on the molded article, which can occur when the molded article is exposed to a high-temperature environment for a long period of time.An object of the present invention is also to provide a molded article that can prevent an excessive decrease in adhesion (i.e., adhesive strength) between the molded article and an object (e.g., a gap filler) placed on the molded article, which can occur when the molded article is exposed to a high-temperature environment for a long period of time.

[0009] In order to solve this problem, the present invention has the following configuration [1]: [1] A polyamide, a fibrous inorganic reinforcing material, and a thermally conductive inorganic filler, which contains a polyamide, a fibrous inorganic reinforcing material, and a thermally conductive inorganic filler, and when left in a temperature environment of 150°C for 1000 hours, －１ ~1700cm －１ The peak area of ​​1665 cm －１ ~1630cm －１ A polyamide composition, wherein the ratio (hereinafter sometimes referred to as the "peak area ratio") of the area of ​​the peak A to the area of ​​the peak B (hereinafter sometimes referred to as "peak B") is 0.10 or less, and when left in a temperature environment of 150°C for 1000 hours, the absolute value of the difference in arithmetic mean roughness (Ra) before and after the polyamide composition is left in a temperature environment of 150°C is 1.5 μm or less. Here, the "infrared absorption spectrum" refers to the infrared absorption spectrum at a depth of 50 μm from the surface of a molded article obtained by molding a molded article having an arithmetic mean roughness (Ra) of 0.1 μm using the polyamide composition and then leaving the molded article in a temperature environment of 150°C for 1000 hours. The "difference in arithmetic mean roughness (Ra)" is determined by the following procedure: a flat molded article having an arithmetic mean roughness (Ra) of 0.1 μm is produced using the polyamide composition, and the arithmetic mean roughness (Ra) is measured after the flat molded article is left in a temperature environment of 150°C for 1000 hours.

[0010] According to [1], the strength of the molded product, specifically the bending strength of the molded product, can be improved by the fibrous inorganic reinforcing material.

[0011] Moreover, the thermally conductive inorganic filler can improve the thermal conductivity of the molded article, that is, the heat dissipation properties of the molded article.

[0012] Furthermore, by having a peak area ratio of 0.10 or less, excessive deterioration of the adhesion between the molded article and an object (for example, a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time, can be avoided. This is because it is possible to reduce the degree of deterioration of the polyamide when the molded article is exposed to a high-temperature environment for a long period of time. This will be explained. －１ ~1700cm －１The peak at 1665 cm (i.e., peak A) is a peak that increases due to degradation of polyamide. －１ ~1630cm －１ The peak (i.e., peak B) is a peak derived from the carbonyl group of the amide bond. Therefore, in the infrared absorption spectrum after standing for 1,000 hours in a 150°C temperature environment, the smaller the ratio of the peak A area to the peak B area (i.e., peak A area / peak B area), the smaller the degree of degradation of the polyamide. According to [1], since this ratio, i.e., the peak area ratio, is 0.10 or less, the degree of degradation of the polyamide on the surface or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time can be reduced. Therefore, detachment of the thermally conductive inorganic filler or fibrous inorganic reinforcing material and crack generation, which may occur when the molded article is exposed to a high-temperature environment for a long period of time, can be reduced. In other words, the degree of deterioration of the smoothness of the molded article when the molded article is exposed to a high-temperature environment for a long period of time can be reduced. As a result, excessive deterioration of the adhesion between the molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time, can be avoided.

[0013] Furthermore, the difference in arithmetic mean roughness (Ra) is 1.5 μm or less in absolute value, that is, the difference between the arithmetic mean roughness (Ra) after leaving it in a temperature environment of 150°C for 1000 hours and the arithmetic mean roughness (Ra) before leaving it in a temperature environment of 150°C for 1000 hours is 1.5 μm or less. This further prevents excessive deterioration in the adhesion between the molded article and an object on the molded article (for example, a gap filler), which can occur when the molded article is exposed to a high-temperature environment for a long period of time.

[0014] In the present invention, the following configurations [2] to

[13] are preferred.

[0015] [2] The polyamide composition according to [1], having a flexural strength of 120 MPa or more and a thermal conductivity of 0.60 W / m·K or more. Here, the flexural strength is a value measured after preparing a test piece using the polyamide composition. The thermal conductivity is a value measured after preparing a disk-shaped sample using the polyamide composition. According to [2], when the molded article is used as a peripheral part of an electric / electronic component (e.g., a battery, a motor), the molded article can have suitable mechanical properties and thermal conductivity.

[0016] [3] The polyamide composition according to [1] or [2], wherein the difference is 1.0 μm or less in absolute value. [3] This further prevents excessive deterioration in adhesion between a molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time.

[0017] [4] The polyamide composition according to any one of [1] to [3], further comprising an antioxidant and a stabilizer.

[0018] [5] The polyamide composition according to any one of [1] to [4], wherein the polyamide comprises a crystalline polyamide. According to [5], the mechanical properties of the polyamide composition can be improved.

[0019] [6] The polyamide composition according to any one of [1] to [5], wherein the polyamide has a relative viscosity of 2.0 or more and 3.6 or less. Here, the relative viscosity is a value measured in accordance with JIS K6920-2:2009 using 98% sulfuric acid, a sample (i.e., polyamide) of 1 g / dL, and at 25°C. According to [6], when the polyamide composition is melted and flowed for injection molding, the polyamide composition can exhibit flowability suitable for injection molding.

[0020] [7] The polyamide composition according to any one of [1] to [6], wherein the content of the thermally conductive inorganic filler is 35 mass% or more. According to [7], the thermal conductivity of a molded article, i.e., the heat dissipation property of the molded article, can be further improved.

[0021] [8] The polyamide composition according to any one of [1] to [7], wherein the thermally conductive inorganic filler is surface-treated. Regarding [8], the thermally conductive inorganic filler can be surface-treated, for example, with a compound reactive with carboxylic acid groups and / or carboxylic anhydride groups. Surface-treating the thermally conductive inorganic filler with a compound reactive with carboxylic acid groups and / or carboxylic anhydride groups allows the mechanical properties and thermal conductivity to be uniformly (i.e., evenly) exhibited in the polyamide composition or molded article, and further reduces the degree of deterioration in the smoothness of the molded article when exposed to a high-temperature environment for an extended period of time. This will be explained below. Surface-treating the thermally conductive inorganic filler with a compound reactive with carboxylic acid groups and / or carboxylic anhydride groups improves the affinity of the thermally conductive inorganic filler for polyamide, thereby improving the dispersibility and adhesion of the thermally conductive inorganic filler. Improved dispersibility contributes to the uniformly (i.e., evenly) exhibited mechanical properties and thermal conductivity in the polyamide composition or molded article. On the other hand, improved adhesion contributes to the interfacial strength between the thermally conductive inorganic filler and the polyamide, and therefore can reduce detachment of the thermally conductive inorganic filler that can occur when the molded article is exposed to a high-temperature environment for a long period of time, and therefore can further reduce the degree of deterioration in the smoothness of the molded article when the molded article is exposed to a high-temperature environment for a long period of time.

[0022] [9] The polyamide composition according to any one of [1] to [8], which is used as a raw material for a molded article to be provided with a gap filler.

[0023]

[10] The polyamide composition according to any one of [1] to [9], further comprising a phenolic antioxidant and a copper compound. According to

[10] , it is possible to effectively reduce the degree of degradation of the polyamide on or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time, thereby further preventing excessive deterioration in adhesion between the molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time. This is explained below. When a molded article is exposed to a high-temperature environment for a long period of time, radicals may be generated at a rate exceeding the radical scavenging rate of the phenolic antioxidant. That is, the amount of radicals generated per unit time may exceed the radical scavenging amount of the phenolic antioxidant per unit time. The use of a copper compound together with the phenolic antioxidant can stabilize the polyamide, thereby reducing oxidative degradation of the polyamide due to radicals not captured by the phenolic antioxidant. Therefore, it is possible to effectively reduce the degree of degradation of the polyamide on or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time, thereby further reducing the degree of deterioration in the smoothness of the molded article, and as a result, it is possible to further prevent excessive deterioration in the adhesion between the molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time.

[0024]

[11] The polyamide composition according to

[10] , wherein the phenolic antioxidant has a hindered structure, and the copper compound is at least one selected from the group consisting of copper acetate, copper iodide, and copper bromide. According to

[11] , the hindered structure of the phenolic antioxidant prevents excessively rapid reaction with radicals that cause oxidative degradation of the surface of molded articles, thereby allowing the phenolic antioxidant to exert its oxidative degradation inhibitory effect for a long period of time. The copper compound being at least one selected from the group consisting of copper acetate, copper iodide, and copper bromide further stabilizes the polyamide, thereby further reducing oxidative degradation of the polyamide caused by radicals not captured by the phenolic antioxidant.

[0025]

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

[11] , further comprising a mold release agent. According to

[12] , when the polyamide composition is molded in a mold (for example, when injection molding), it becomes easy to remove the molded article from the mold. Therefore, even if the molded article has a complex shape, it can be easily removed from the mold.

[0026]

[13] A molded article obtained by molding the polyamide composition according to any one of [1] to

[12] .

[0027] In order to solve the above-mentioned problems, the present invention may have the following configuration

[14] :

[14] A polyamide composition comprising a polyamide, a fibrous inorganic reinforcing material, a thermally conductive inorganic filler, a phenolic antioxidant, and a copper compound.

[0028] According to

[14] , the strength of the molded article, specifically the bending strength of the molded article, can be improved by using a fibrous inorganic reinforcing material.

[0029] Moreover, the thermally conductive inorganic filler can improve the thermal conductivity of the molded article, that is, the heat dissipation properties of the molded article.

[0030] Furthermore, the use of a phenolic antioxidant and a copper compound can prevent excessive deterioration in the adhesion between a molded article and an object (e.g., a gap filler) placed on the molded article, which can occur when the molded article is exposed to a high-temperature environment for a long period of time. This will be explained below. As described above, the use of a copper compound can stabilize the polyamide, thereby reducing oxidative degradation of the polyamide caused by radicals not captured by the phenolic antioxidant. Therefore, it is possible to effectively reduce the degree of degradation of the polyamide on or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time, thereby minimizing the deterioration of the smoothness of the molded article. As a result, it is possible to prevent excessive deterioration in the adhesion between the molded article and an object (e.g., a gap filler) placed on the molded article, which can occur when the molded article is exposed to a high-temperature environment for a long period of time.

[0031] The present invention preferably has the following configuration

[15] :

[15] A molded article obtained by molding the polyamide composition according to

[14] .

[0032] It is possible to provide a polyamide composition that can avoid an excessive decrease in adhesion (i.e., adhesive strength) between a molded article and an object (e.g., a gap filler) on the molded article, which can occur when the molded article is exposed to a high-temperature environment for a long period of time.It is also possible to provide a molded article that can avoid an excessive decrease in adhesion (i.e., adhesive strength) between the molded article and an object (e.g., a gap filler) on the molded article, which can occur when the molded article is exposed to a high-temperature environment for a long period of time.

[0033] 1 is a photograph taken when the surface of the flat plate molded product molded in Example 1 was observed under a microscope after being treated at 150° C. for 1000 hours. 2 is a photograph taken when the surface of the flat plate molded product molded in Comparative Example 2 was observed under a microscope after being treated at 150° C. for 1000 hours.

[0034] Hereinafter, embodiments of the present invention will be described in detail.

[0035] <1. Polyamide Composition> <1.1. Polyamide> The polyamide composition of the present embodiment contains a polyamide. Polyamide is a polymer having an amide bond (—NHCO—) in the main chain.

[0036] The polyamide is preferably a crystalline polyamide. By including a crystalline polyamide in the polyamide, the mechanical properties of the polyamide composition can be improved. In addition, the mechanical properties of the molded article when exposed to a high-temperature environment for a long period of time can also be improved. Examples of crystalline polyamides include polyamide 6 (PA6), polyamide 66 (PA66), polyamide 46 (PA46), polyamide 56 (PA56), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 510 (PA510), polyamide 610 (PA610), polyamide 612 (PA612), polymetaxylylene adipamide (PAMXD6), hexamethylenediamine-terephthalic acid polymer (PA6T), hexamethylenediamine-terephthalic acid, and adipic acid polymer. Examples of suitable polyamides include PA6T / 66, hexamethylenediamine-terephthalic acid and ε-caprolactam copolymer (PA6T / 6), trimethylhexamethylenediamine-terephthalic acid polymer (PATMD-T), metaxylylenediamine, adipic acid, and isophthalic acid copolymer (PAMXD6 / MXDI), trihexamethylenediamine, terephthalic acid, and ε-caprolactam copolymer (PATMDT / 6), and diaminodicyclohexylenemethane, isophthalic acid, and lauryllactam copolymer. These may be used alone or in combination of two or more. Furthermore, crystalline polyamides obtained by polymerization of plant-derived raw materials may also be used. Among these, polyamide 6 is preferred due to its excellent moldability, melt flowability, and mechanical properties.

[0037] Polyamide 6 is preferably a polyamide whose main raw material is ε-caprolactam. Polyamides whose main raw material is ε-caprolactam can be obtained by polycondensation. Polyamide 6 may be copolymerized with other monomers. Examples of such monomers include amino acids such as 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid; lactams such as ω-laurolactam; aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 2-methylpentamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine, and 5-methylnonamethylenediamine; aromatic diamines such as metaxylylenediamine and paraxylylenediamine; 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, and bis(4-aminocyclohexyl)cyclohexane. alicyclic diamines such as bis(3-methyl-4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine, and aminoethylpiperazine; aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodiumsulfoisophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 1,3-cyclopentanedicarboxylic acid. Two or more of these may be copolymerized.

[0038] Of the total 100 mol % of monomer units constituting polyamide 6, the units derived from ε-caprolactam are preferably 60 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and even more preferably 90 mol % or more. This may be 100 mol %.

[0039] The relative viscosity of the crystalline polyamide is preferably 1.5 or higher, more preferably 1.8 or higher, and even more preferably 2.0 or higher. A relative viscosity of 1.5 or higher can prevent an excessive increase in fluidity when the polyamide composition is melted and flowed. For example, when the polyamide composition is melted and flowed for injection molding, the polyamide composition can be prevented from exhibiting excessively high fluidity for injection molding. In addition, strength can be further improved. The relative viscosity of the crystalline polyamide is preferably 4.5 or lower, more preferably 4.0 or lower, and even more preferably 3.6 or lower. A relative viscosity of 4.5 or lower can prevent an excessive decrease in fluidity when the polyamide composition is melted and flowed. For example, when the polyamide composition is melted and flowed for injection molding, the polyamide composition can be prevented from exhibiting excessively low fluidity for injection molding. In addition, the dispersibility of the thermally conductive inorganic filler can be improved. The relative viscosity is a value measured at 25°C using 98% sulfuric acid at a sample (i.e., polyamide) concentration of 1 g / dL in accordance with JIS K6920-2:2009.

[0040] In the polyamide composition of the present embodiment, the content of the crystalline polyamide is preferably 80% by mass or more, or may be 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass, based on 100% by mass of the polyamide.

[0041] The polyamide composition of the present embodiment may contain an amorphous polyamide. When the polyamide composition contains an amorphous polyamide, transfer to a molded article (i.e., mold transfer) becomes easy when the polyamide composition is injection molded. The amorphous polyamide may be a polyamide that does not show a crystalline melting peak in a thermogram measured by differential scanning calorimetry (DSC). Examples of amorphous polyamides include polymers obtained by polycondensation of diamines such as 4,4'-diamino-3,3'-dimethyldicyclohexylmethane (CA), 4,4'-diaminodicyclohexylmethane (PACM), metaxylylenediamine (MXD), trimethylhexamethylenediamine (TMD), isophoronediamine (IA), 4,4'-diaminodicyclohexylpropane (PACP), and hexamethylenediamine with dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, and, if necessary, lactams such as caprolactam and lauryllactam. These may be used alone or in combination of two or more. Of course, other monomers may also be copolymerized into the amorphous polyamide.

[0042] In particular, the amorphous polyamide preferably contains an aromatic component, since crystallization is easily suppressed. As the amorphous polyamide containing an aromatic component, polyamide 6T / 6I made from terephthalic acid, isophthalic acid, and adipic acid as raw materials, and polyamide 6T / 66 made from terephthalic acid, adipic acid, and hexamethylenediamine as raw materials are preferred. Among them, polyamide 6T / 6I is more preferred in terms of moldability.

[0043] In the polyamide composition of the present embodiment, the polyamide content is preferably 25% by mass or more, more preferably 30% by mass or more, and even more preferably 38% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 42% by mass or less.

[0044] <1.2. Fibrous inorganic reinforcing material> The polyamide composition of the present embodiment contains a fibrous inorganic reinforcing material. The fibrous inorganic reinforcing material can improve strength, specifically bending strength. In addition, rigidity and heat resistance can also be improved.

[0045] Examples of fibrous inorganic reinforcing materials include glass fiber, carbon fiber, aramid fiber, alumina fiber, silicon carbide fiber, and zirconia fiber. Examples of fibrous inorganic reinforcing materials include whiskers such as aluminum borate and potassium titanate, acicular wollastonite, and milled fiber. Of these, glass fiber and carbon fiber are preferred. These may be used alone or in combination of two or more.

[0046] Examples of glass fibers include chopped strand glass fibers. The fiber length of the glass fibers is preferably 1 mm to 20 mm. The cross-sectional shape of the glass fibers may be circular or noncircular. Here, the "cross-sectional shape" refers to the shape of a cross section perpendicular to the longitudinal direction of the glass fibers. Examples of noncircular cross sections include a substantially elliptical cross section, a substantially oval cross section, and a substantially cocoon-shaped cross section. The flatness of glass fibers with noncircular cross sections is preferably 1.5 to 8. Here, the flatness refers to the ratio of the major axis to the minor axis (i.e., major axis / minor axis) when a rectangle with the smallest area circumscribing a cross section perpendicular to the longitudinal direction of the glass fiber is assumed, and the length of the long side of this rectangle is the major axis and the length of the short side is the minor axis. The minor axis of the glass fibers is preferably 1 μm to 20 μm. The major axis of the glass fibers is preferably 2 μm to 100 μm.

[0047] For the fibrous inorganic reinforcing material, the ratio of the average fiber length to the average fiber diameter is preferably at least 100, more preferably at least 200. This ratio is preferably at most 1000, more preferably at most 800. This ratio may be at most 500.

[0048] The fibrous inorganic reinforcing material is preferably treated with a coupling agent. This improves its affinity with polyamide, resulting in improved mechanical properties and improved appearance. Examples of coupling agents include organosilane compounds, organotitanium compounds, organoborane compounds, and epoxy compounds. Preferred coupling agents are those that readily react with carboxylic acid groups and / or carboxylic anhydride groups. Surface-treating the fibrous inorganic reinforcing material with a compound readily reactive with carboxylic acid groups and / or carboxylic anhydride groups allows the mechanical properties to be uniformly (i.e., evenly) expressed in polyamide compositions and molded articles, and further reduces the degree of deterioration in the smoothness of molded articles when exposed to high-temperature environments for long periods of time. This will be explained below. Surface-treating the fibrous inorganic reinforcing material with a compound readily reactive with carboxylic acid groups and / or carboxylic anhydride groups improves the affinity of the fibrous inorganic reinforcing material with polyamide, thereby improving the dispersibility and adhesion of the fibrous inorganic reinforcing material. Improved dispersibility contributes to the uniform (i.e., consistent) expression of mechanical properties in polyamide compositions and molded articles. On the other hand, improved adhesion contributes to the interfacial strength between the fibrous inorganic reinforcing material and polyamide, thereby reducing the detachment of the fibrous inorganic reinforcing material that can occur when a molded article is exposed to a high-temperature environment for a long period of time. Therefore, the degree of deterioration in the smoothness of the molded article when exposed to a high-temperature environment for a long period of time can be further reduced. Examples of coupling agents that can be used in a slightly different way include silane-based coupling agents, titanate-based coupling agents, and aluminum-based coupling agents. Among these, silane-based coupling agents such as aminosilane coupling agents and epoxysilane coupling agents are preferred. While it is preferable to treat the composition with a coupling agent beforehand, the coupling agent may also be added later.

[0049] In the polyamide composition of this embodiment, the content of the fibrous inorganic reinforcing material is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. If it is 5% by mass or more, the bending strength, i.e., strength, can be further improved. On the other hand, the content of the fibrous inorganic reinforcing material is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. If it is 50% by mass or less, it is possible to avoid difficulties in producing molded articles using the polyamide composition.

[0050] <1.3. Thermally conductive inorganic filler> The polyamide composition of this embodiment contains a thermally conductive inorganic filler. The thermally conductive inorganic filler can increase the thermal conductivity of a molded article, thereby improving the heat dissipation properties of the molded article. The term "thermally conductive inorganic filler" can refer to a filler that contains an inorganic compound and has a thermal conductivity of 1 W / m K or more.

[0051] Examples of inorganic compounds contained in the thermally conductive inorganic filler include boron nitride, alumina, silica, aluminum hydroxide, magnesium oxide, and aluminum nitride. These may be used alone or in combination of two or more. It is preferable that the thermally conductive inorganic filler has insulating properties.

[0052] Examples of thermally conductive inorganic fillers containing magnesium oxide include sintered bodies (i.e., sintered bodies containing magnesium oxide) and light-burned magnesia. Among these, sintered bodies are preferred. Here, the "sintered body", specifically the "sintered body containing magnesium oxide" is a granular sintered body in which some particles containing magnesium oxide are bonded together. The sintered body is a granular sintered body in which some particles containing magnesium oxide are bonded together. ２ The sintered body may further contain magnesium oxide, silicon oxide (SiO ２ ), calcium oxide (CaO), and compounds formed by reaction of these. ２ O ３ , Al ２ O ３ , Fe ２ O ３ , Na ２SO ４ It may also include the following.

[0053] The magnesium oxide content in the sintered body is preferably 85.0 mass% or more, more preferably 88.0 mass% or more, even more preferably 90.0 mass% or more, even more preferably 92.0 mass% or more, and even more preferably 94.0 mass% or more, based on 100 mass% of the sintered body. When it is 85.0 mass% or more, the thermal conductivity of the sintered body is excellent. On the other hand, the magnesium oxide content may be, for example, 99.7 mass% or less, based on 100 mass% of the sintered body.

[0054] The particle size, specifically the median diameter, of the thermally conductive inorganic filler is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 5 μm or more, and even more preferably 10 μm or more. When the particle size is 1 μm or more, an excessive decrease in fluidity can be suppressed when the polyamide composition is melted and flowed. The median diameter may be 30 μm or more, or may be 60 μm or more. On the other hand, the median diameter is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. When the median diameter is 200 μm or less, the thermal conductivity can be further improved. The median diameter may be 80 μm or less. Here, the median diameter is D50, which is specifically the particle size at 50% of the cumulative particle size distribution on a volume basis of the thermally conductive inorganic filler.

[0055] The shape (i.e., particle shape) of the thermally conductive inorganic filler can be, for example, plate-like, acicular, spherical, fibrous, or irregular. Of these, spherical and irregular shapes are preferred. A spherical shape can impart uniform heat dissipation properties to the molded article without bias in the flow direction, vertical direction, or thickness direction of the molded article.

[0056] The thermally conductive inorganic filler is preferably surface-treated, more preferably with a coupling agent. Examples of coupling agents include organosilane compounds, organotitanium compounds, organoborane compounds, and epoxy compounds. The preferred coupling agents are those that readily react with carboxylic acid groups and / or carboxylic anhydride groups. Surface-treating the thermally conductive inorganic filler with a compound readily reactive with carboxylic acid groups and / or carboxylic anhydride groups allows the mechanical properties and thermal conductivity to be uniformly (i.e., evenly) exhibited in polyamide compositions and molded articles, and further reduces the degree of deterioration in the smoothness of molded articles when exposed to high-temperature environments for long periods of time. This will be explained below. Surface-treating the thermally conductive inorganic filler with a compound readily reactive with carboxylic acid groups and / or carboxylic anhydride groups improves the affinity of the thermally conductive inorganic filler for polyamides, thereby improving the dispersibility and adhesion of the thermally conductive inorganic filler. Improved dispersibility contributes to the uniform (i.e., uniform) expression of mechanical properties and thermal conductivity in polyamide compositions and molded articles. On the other hand, improved adhesion contributes to the interfacial strength between the thermally conductive inorganic filler and polyamide, thereby reducing the detachment of the thermally conductive inorganic filler that can occur when a molded article is exposed to a high-temperature environment for a long period of time. Therefore, the degree of deterioration in the smoothness of the molded article when exposed to a high-temperature environment for a long period of time can be further reduced. It is also expected to reduce the degree of deterioration in the thermal conductivity of the molded article when exposed to a high-temperature environment for a long period of time. Examples of coupling agents from a slightly different perspective include silane-based coupling agents, titanate-based coupling agents, and aluminum-based coupling agents. Among these, silane-based coupling agents such as aminosilane coupling agents and epoxysilane coupling agents are preferred. While it is preferable to treat the material with a coupling agent beforehand, the coupling agent may also be added later.

[0057] In the polyamide composition of this embodiment, the content of the thermally conductive inorganic filler is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and even more preferably 35% by mass or more. When it is 20% by mass or more, heat dissipation properties can be further improved. The content of the thermally conductive inorganic filler may be 40% by mass or more, or may be 45% by mass or more. On the other hand, the content of the thermally conductive inorganic filler is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. When it is 60% by mass or less, an excessive decrease in fluidity can be suppressed when the polyamide composition is melted and flowed.

[0058] <1.4. Antioxidant and Stabilizer> The polyamide composition of the present embodiment preferably contains an antioxidant and / or a stabilizer, and more preferably contains both an antioxidant and a stabilizer. The antioxidant and / or stabilizer can suppress oxidative degradation of the polyamide.

[0059] Examples of antioxidants or stabilizers include phenolic antioxidants, copper compounds, alkali metal halides, hindered amine stabilizers (HALS), organophosphorus stabilizers, amine antioxidants, sulfur-based antioxidants, finely divided elemental iron, finely dispersed metal powders, and metal cyanide salts. Among these, phenolic antioxidants are preferred as antioxidants. Copper compounds and alkali metal halides are preferred as stabilizers. These may be used alone or in combination of two or more.

[0060] The phenolic antioxidant is preferably a hindered phenolic antioxidant, i.e., a phenolic antioxidant having a hindered structure. The hindered structure of the phenolic antioxidant makes it possible to prevent excessively rapid reaction with radicals that cause oxidative degradation of the surface of molded articles, thereby enabling the phenolic antioxidant to exert its oxidative degradation action for a long period of time. The hindered structure can be a structure in which at least one of the two carbon atoms in the ortho position of the carbon atom bearing a hydroxyl group, among the carbon atoms constituting the benzene ring contained in the aromatic hydrocarbon, has a bulky substituent. An example of a bulky substituent is a tert-butyl group. Examples of hindered phenol antioxidants include N,N'-hexamethylene-bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, bis(3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butanoic acid) glycol ester, 2,1'-thioethylbis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), and triethylene glycol-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate ("SONGNOX 2450", molecular weight 633). These may be used alone or in combination of two or more.

[0061] In the polyamide composition of this embodiment, the content of the phenolic antioxidant is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more. At 0.05% by mass or more, oxidative degradation of the polyamide composition can be further suppressed. On the other hand, the content of the phenolic antioxidant is preferably 1.0% by mass or less, more preferably 0.5% by mass or less. The content of the phenolic antioxidant may be 0.4% by mass or less, 0.3% by mass or less, or 0.25% by mass or less.

[0062] Copper compounds have the effect of preventing oxidative degradation of polyamides, which is thought to be because the copper ions of the copper compounds coordinate with the amide groups, thereby forming a chelate, which in turn stabilizes the polyamide.

[0063] Examples of copper compounds include fatty acid copper and copper halides. Examples of copper halides include copper chloride, copper bromide, copper iodide, and copper fluoride. Examples of fatty acid copper compounds include copper acetate, copper laurate, and copper stearate. Among these, copper bromide, copper iodide, and copper acetate are preferred, and copper bromide is more preferred. Of the copper bromides, cupric bromide is preferred. These compounds may be used alone or in combination of two or more.

[0064] The content of the copper compound is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, based on copper (i.e., copper element equivalent) per 100 parts by mass of the polyamide resin. At 0.001 parts by mass or more, oxidative degradation of the polyamide composition can be further suppressed. The content of the copper compound is preferably 1.0 part by mass or less, more preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.03 parts by mass or less, based on copper (i.e., copper element equivalent) per 100 parts by mass of the polyamide resin. At 1.0 part by mass or less, corrosion of molds, extruders, and molding machines (e.g., corrosion of screws, cylinders, etc.) that may be caused by copper compounds can be suppressed.

[0065] In the polyamide composition of this embodiment, the content of the copper compound is preferably 0.001% by mass or more, more preferably 0.003% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.007% by mass or more, and even more preferably 0.010% by mass or more. The content of the copper compound may be 0.015% by mass or more, or may be 0.020% by mass or more. On the other hand, the content of the copper compound is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.3% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.07% by mass or less, and even more preferably 0.05% by mass or less.

[0066] As the antioxidant, a phenolic antioxidant and a copper compound are preferably used in combination, and a hindered phenolic antioxidant and a copper compound are more preferably used in combination. By using these in combination, it is possible to effectively reduce the degree of degradation of the polyamide on or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time, thereby further preventing excessive deterioration in adhesion between the molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time. This will be explained below. When a molded article is exposed to a high-temperature environment for a long period of time, radicals may be generated at a rate that exceeds the radical scavenging rate of the phenolic antioxidant. That is, the amount of radicals generated per unit time may exceed the radical scavenging amount per unit time of the phenolic antioxidant. For example, when a molded article is exposed to 150°C for a long period of time, the amount of radicals generated per unit time may exceed the radical scavenging amount per unit time of the hindered phenolic antioxidant. The use of a copper compound together with a phenolic antioxidant can stabilize polyamides, thereby reducing oxidative degradation of the polyamide caused by radicals not captured by the phenolic antioxidant. This effectively reduces the degree of degradation of the polyamide on or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time, thereby further reducing the degree of deterioration in the smoothness of the molded article. As a result, excessive deterioration in adhesion between the molded article and objects (e.g., gap fillers) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time, can be further prevented. Other antioxidants (e.g., hindered amine stabilizers (HALS), organophosphorus stabilizers, amine-based antioxidants, sulfur-based antioxidants, finely divided elemental iron, finely dispersed metal powders, and metal cyanide salts) may also be used together with the phenolic antioxidant and copper compound.

[0067] In the polyamide composition of the present embodiment, the total content of the phenolic antioxidant and the copper compound is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 93% by mass or more, based on 100% by mass of the antioxidant. The total content of the phenolic antioxidant and the copper compound may be 95% by mass or more, 98% by mass or more, or even 100% by mass.

[0068] Alkali metal halides (i.e., alkali metal halide compounds) also have the effect of preventing oxidative degradation of polyamides. Examples of alkali metal halides include potassium halides such as potassium iodide and potassium bromide. When the polyamide composition of this embodiment contains a copper compound and an alkali metal halide, the alkali metal halide can also prevent copper precipitation.

[0069] In the polyamide composition of this embodiment, the content of the alkali metal halide is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.08% by mass or more, while the content of the alkali metal halide is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.4% by mass or less, even more preferably 0.3% by mass or less, and even more preferably 0.2% by mass or less.

[0070] In the polyamide composition of this embodiment, the content of the antioxidant is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more. On the other hand, the content of the antioxidant is preferably 1.0% by mass or less, more preferably 0.5% by mass or less. The content of the antioxidant may be 0.4% by mass or less, 0.3% by mass or less, or 0.25% by mass or less.

[0071] In the polyamide composition of this embodiment, the stabilizer content is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.015% by mass or more, while the stabilizer content is preferably 0.1% by mass or less, more preferably 0.07% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less.

[0072] In the polyamide composition of this embodiment, the total content of the antioxidant and stabilizer is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more. On the other hand, the total content of the antioxidant and stabilizer is preferably 1.0% by mass or less, more preferably 0.5% by mass or less. The total content may be 0.4% by mass or less, 0.3% by mass or less, or 0.25% by mass or less.

[0073] <1.5. Mold Release Agent> The polyamide composition of the present embodiment preferably contains a mold release agent. When the polyamide composition contains a mold release agent, when the polyamide composition is molded in a mold (for example, when injection molding), it becomes easy to remove the molded article from the mold. Therefore, even if the molded article has a complex shape, it can be easily removed from the mold.

[0074] Examples of the release agent include esters and metal salts of long-chain fatty acids. Examples of the release agent include amide compounds such as ethylene bisterephthalamide and methylene bisstearylamide. Examples of the release agent include waxes such as aliphatic hydrocarbons and polyethylenes, and polysiloxane silicone oils. Of these, fatty acid metal salt-based release agents and fatty acid ester-based release agents are preferred. That is, fatty acid metal salts and fatty acid ester-based compounds (i.e., fatty acid esters) are preferred. These may be used alone or in combination of two or more.

[0075] Examples of fatty acid metal salts include metal salts of fatty acids having 12 to 40 carbon atoms, such as stearic acid, palmitic acid, behenic acid, erucic acid, oleic acid, lauric acid, and montanic acid. Of these, metal salts of aliphatic carboxylic acids having 22 to 30 carbon atoms are preferred. In particular, alkali metal or alkaline earth metal salts of behenic acid, lignoceric acid, and montanic acid are more preferred in terms of mold releasability. Examples of alkali metal or alkaline earth metal salts include lithium, sodium, magnesium, and calcium.

[0076] Examples of fatty acid ester compounds include higher fatty acid ester compounds, such as a mixture containing myricyl palmitate as a main component, stearyl stearate, behenyl behenate, stearyl behenate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, and pentaerythritol tetrastearate.

[0077] In the polyamide composition of this embodiment, the content of the mold release agent is preferably 0.01% by mass or more, more preferably 0.1% by mass or more. If the content is 0.01% by mass or more, when the polyamide composition is injected into a mold, it is possible to prevent the polyamide composition from sticking to the mold and to prevent wrinkles that may occur on the surface of the molded product upon mold release. On the other hand, the content of the mold release agent is preferably 1.0% by mass or less, more preferably 0.5% by mass or less.

[0078] <1.6. Other Additives, etc.> The polyamide composition of the present embodiment may contain, for example, carbon black, copper oxide, a light stabilizer, a crystal nucleating agent, an antistatic agent, a pigment, a dye, an electromagnetic wave inhibitor, etc. Of course, the polyamide composition of the present embodiment may contain a resin other than polyamide.

[0079] In the polyamide composition of this embodiment, the total content of the fibrous inorganic reinforcing material and the thermally conductive inorganic filler is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 58% by mass or more, while the total content of the fibrous inorganic reinforcing material and the thermally conductive inorganic filler is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 62% by mass or less.

[0080] <1.7. Physical Properties> The higher the flexural strength of the polyamide composition of this embodiment, the better. The flexural strength is preferably 120 MPa or more, more preferably 150 MPa or more, even more preferably 160 MPa or more, and even more preferably 170 MPa or more. If the flexural strength is 120 MPa or more, the molded article can have suitable mechanical properties when used as a peripheral part of an electric or electronic component (e.g., a battery or a motor). The flexural strength may be 230 MPa or less, 220 MPa or less, or 215 MPa or less. The flexural strength of the polyamide composition is a value measured after preparing a test piece using the polyamide composition. Specifically, the flexural strength of the polyamide composition is a value measured by the method described in the examples.

[0081] The higher the thermal conductivity of the polyamide composition of this embodiment, the better. A thermal conductivity of 0.60 W / m·K or higher is preferred, more preferably 0.65 W / m·K or higher, and even more preferably 0.70 W / m·K or higher. A thermal conductivity of 0.60 W / m·K or higher allows the molded article to have suitable thermal conductivity when used as a peripheral component for electrical and electronic components (e.g., batteries, motors). The thermal conductivity of the polyamide composition may be 1.20 W / m·K or lower, 1.10 W / m·K or lower, or even 1.00 W / m·K or lower. The thermal conductivity of the polyamide composition is a value measured after preparing a disk-shaped sample using the polyamide composition. Specifically, the thermal conductivity of the polyamide composition is a value measured by the method described in the Examples.

[0082] Regarding the polyamide composition of this embodiment, when it is left in a temperature environment of 150°C for 1000 hours, the infrared absorption spectrum of －１ ~1700cm －１ The peak area of ​​1665 cm (i.e., peak A) －１ ~1630cm －１It is preferable that the ratio (i.e., peak area ratio) of the peak area of ​​1750 cm to the peak area of ​​peak B (i.e., peak B) is 0.10 or less. Here, the "infrared absorption spectrum" refers to the infrared absorption spectrum at a depth of 50 μm from the surface of a molded article obtained by molding a polyamide composition into a molded article having an arithmetic mean roughness (Ra) of 0.1 μm and then leaving the molded article in a temperature environment of 150°C for 1000 hours. By having a peak area ratio of 0.10 or less, excessive deterioration of the adhesion between the molded article and an object on the molded article (e.g., a gap filler) that can occur when the molded article is exposed to a high-temperature environment for a long period of time can be avoided. This is because it is possible to further reduce the degree of degradation of the polyamide when the molded article is exposed to a high-temperature environment for a long period of time. This will be explained below. 1750 cm －１ ~1700cm －１ The peak at 1665 cm (i.e., peak A) is a peak that increases due to degradation of polyamide. －１ ~1630cm －１The peak (i.e., peak B) is a peak derived from the carbonyl group of the amide bond. Therefore, in the infrared absorption spectrum after standing for 1,000 hours in a 150°C temperature environment, the smaller the ratio of the area of ​​Peak A to the area of ​​Peak B (i.e., Peak A area / Peak B area), the smaller the degree of degradation of the polyamide. According to the polyamide composition of this embodiment, this ratio, i.e., the peak area ratio, is 0.10 or less, so the degree of degradation of the polyamide on the surface or near the surface of a molded article when the molded article is exposed to a high-temperature environment for a long period of time can be further reduced. Therefore, detachment of the thermally conductive inorganic filler or fibrous inorganic reinforcing material and crack generation, which may occur when the molded article is exposed to a high-temperature environment for a long period of time, can be reduced. In other words, the degree of deterioration of the smoothness of the molded article when the molded article is exposed to a high-temperature environment for a long period of time can be reduced. As a result, excessive deterioration of the adhesion between the molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time, can be avoided. The peak area ratio is more preferably 0.09 or less, even more preferably 0.08 or less, even more preferably 0.06 or less, even more preferably 0.05 or less, and even more preferably 0.04 or less. The peak area ratio may be 0.03 or less, or may be 0.02 or less. The peak area ratio is specifically a value measured by the method described in the Examples.

[0083] The polyamide composition of this embodiment preferably has an arithmetic mean roughness (Ra) (hereinafter sometimes referred to as "post-treatment roughness") of 3.0 μm or less, more preferably 2.5 μm or less, and even more preferably 2.0 μm or less, after being left in a 150°C temperature environment for 1000 hours. A value of 2.0 μm or less further prevents excessive deterioration in adhesion between the molded article and an object (e.g., a gap filler) on the molded article, which may occur when the molded article is exposed to a high-temperature environment for a long period of time. The arithmetic mean roughness (Ra) may be 1.5 μm or less, 1.2 μm or less, or even 1.0 μm or less. The post-treatment roughness of the polyamide composition is measured after a flat molded article having an arithmetic mean roughness (Ra) of 0.1 μm is produced using the polyamide composition and then left in a 150°C temperature environment for 1000 hours. Specifically, the post-treatment roughness is measured by the method described in the Examples.

[0084] With regard to the polyamide composition of this embodiment, when left in a temperature environment of 150°C for 1000 hours, the difference in arithmetic mean roughness (Ra) before and after leaving is preferably 1.5 μm or less in absolute value. That is, the difference between the arithmetic mean roughness (Ra) after leaving in a temperature environment of 150°C for 1000 hours (i.e., post-treatment roughness) and the arithmetic mean roughness (Ra) before leaving in a temperature environment of 150°C for 1000 hours (hereinafter sometimes referred to as "pre-treatment roughness") is preferably 1.5 μm or less. If it is 1.5 μm or less, excessive deterioration in adhesion between the molded article and an object on the molded article (e.g., a gap filler) that may occur when the molded article is exposed to a high-temperature environment for a long period of time can be further avoided. This difference is more preferably 1.3 μm or less, even more preferably 1.0 μm or less, even more preferably 0.8 μm or less, and even more preferably 0.6 μm or less.

[0085] <1.8. Production Method and Use> The polyamide composition of this embodiment can be produced by kneading at least polyamide, a fibrous inorganic reinforcing material, a thermally conductive inorganic filler, and, if necessary, an antioxidant and / or a stabilizer in a kneading device. For kneading, an extruder (e.g., a single-screw extruder or a twin-screw extruder), a pressure kneader, or the like can be used. Of these, an extruder is preferred, and a twin-screw extruder is more preferred. The kneading temperature can be 220°C to 300°C. The kneading time can be, for example, about 2 minutes to 15 minutes.

[0086] For example, the polyamide composition of the present embodiment can be produced by a method in which at least polyamide, a fibrous inorganic reinforcing material, a thermally conductive inorganic filler, and, if necessary, an antioxidant and / or a stabilizer are melt-kneaded in a twin-screw extruder, and then strands are extruded, if necessary, cooled, and if necessary, cut.

[0087] When at least a copper compound is used as a stabilizer, a masterbatch containing the copper compound may be blended with polyamide, a fibrous inorganic reinforcing material, a thermally conductive inorganic filler, etc., and then kneaded. On the other hand, the copper compound may be added at any stage in the production of polyamide. For example, it may be added to an aqueous solution of raw material salts of polyamide, or it may be added by injection into molten polyamide during melt polymerization.

[0088] The shape of the polyamide composition of the present embodiment can be appropriately set. The polyamide composition of the present embodiment may be, for example, in the form of pellets, strands, or powder, or may be molded into any shape. Among these, the pellet shape is preferred.

[0089] The polyamide composition of this embodiment can be used as a raw material for various molded products. In particular, it is suitable for use as a raw material for electrical and electronic components requiring high thermal conductivity, automotive components (e.g., electric vehicle components), industrial components, and the like. Examples of such components include lamp sockets, electrical components, heat sinks, semiconductor package components, cooling fan components, connectors, switches, case housings, battery cases, components used around battery cases, and components used inside battery cases (e.g., base plates of battery modules). Here, the battery case may be the housing of a battery pack. In particular, it can be suitable for use in the manufacture of peripheral components (e.g., battery cases, components used around battery cases, and components used inside battery cases) of electrical and electronic components (e.g., batteries) that generate high Joule heat. It is particularly suitable for use in the manufacture of battery cases. Here, the use of a polyamide composition for the manufacture of a battery case refers to the use of the polyamide composition for the manufacture of at least one of the components when the battery case includes multiple components.

[0090] The polyamide composition of this embodiment can be suitably used as a raw material for a molded article to which a gap filler is applied. In other words, the polyamide composition of this embodiment can be suitably used for producing a molded article to which a gap filler is applied. To provide the gap filler on a molded article, the gap filler may be applied to the molded article. Alternatively, the gap filler may be applied to something (e.g., a component constituting a battery or motor) and then attached to the molded article with the gap filler, resulting in the formation of the gap filler on the molded article. The gap filler may contain a thermally conductive inorganic filler. A description of the thermally conductive inorganic filler in the gap filler will be omitted because it overlaps with the above description (i.e., the description of the thermally conductive inorganic filler in the polyamide composition of this embodiment). Therefore, the description of the thermally conductive inorganic filler in the polyamide composition of this embodiment can also be used as a description of the thermally conductive inorganic filler in the gap filler. The gap filler can further contain a polymer. Examples of polymers include silicone and polyurethane. These may be used alone or in combination of two or more. The polymer may be an oligomer. The thermally conductive inorganic filler may further contain a curing agent. The thermally conductive inorganic filler may contain other additives. The thermally conductive inorganic filler is preferably curable. Note that the object provided in the molded article may be an object other than the gap filler.

[0091] <2. Molded Article> The molded article of this embodiment can be obtained by molding the polyamide composition of this embodiment described above. That is, the molded article of this embodiment can be obtained from the polyamide composition of this embodiment described above. Examples of molding methods include injection molding, extrusion molding, and blow molding. Among these, injection molding is preferred because it can achieve complex shapes.

[0092] The present invention will be described in more detail below with reference to examples and comparative examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0093] <1. Raw Materials> The following raw materials were used. <1.1. Polyamide> A1: "M2000" manufactured by MEIDA (polyamide 6, relative viscosity 2.0, melting point 225°C) A2: "ZISAMIDE TP4208" manufactured by Shuseisha (polyamide 6, relative viscosity 2.5, melting point 225°C) A3: "ZISAMIDE TP6603" manufactured by Shuseisha (polyamide 6, relative viscosity 3.6, melting point 225°C)

[0094] <1.2. Fibrous inorganic reinforcing materials> B1: "ECS301HP-3-H" (glass fiber) manufactured by Chongqing International Composite Materials Co., Ltd. (CPIC) B2: "CFUW-MC" (carbon fiber) manufactured by Japan Polymer Sangyo Co., Ltd.

[0095] <1.3. Thermally conductive inorganic fillers> C1: "RF-50-AC" manufactured by Ube Material Industries, Ltd. (surface-treated magnesium oxide sintered body with a particle size of 50 μm. This sintered body contains magnesium oxide, calcium oxide, and silicon oxide.) C2: "HF-10" manufactured by Tokuyama Corporation (aluminum nitride with a particle size of 10 μm. No surface treatment.) C3: surface-treated magnesium oxide sintered body with a particle size of 10 μm (details will be described later.) C4: surface-treated magnesium oxide sintered body with a particle size of 100 μm (details will be described later.)

[0096] Thermally conductive inorganic filler C3: A thermally conductive inorganic filler in which a magnesium oxide sintered body having a particle size of 10 μm (this sintered body contains magnesium oxide, calcium oxide, and silicon oxide) produced in accordance with Japanese Patent No. 5,993,824 has been subjected to the same surface treatment as thermally conductive inorganic filler C1 (i.e., "RF-50-AC").

[0097] Thermally conductive inorganic filler C4: A thermally conductive inorganic filler in which a magnesium oxide sintered body having a particle size of 100 μm (this sintered body contains magnesium oxide, calcium oxide, and silicon oxide) produced in accordance with Japanese Patent No. 5,993,824 has been subjected to the same surface treatment as thermally conductive inorganic filler C1 (i.e., "RF-50-AC").

[0098] <1.4. Antioxidants or stabilizers> D1: "SONGNOX 2450" (hindered phenol-based antioxidant) manufactured by SONGWON Co., Ltd. D2: Cupric bromide manufactured by Nippon Chemical Industry Co., Ltd. D3: Potassium iodide manufactured by Godo Shigen Co., Ltd.

[0099] <1.5. Mold Release Agent> E1: "Recorb WE-40" (aliphatic ester) manufactured by Clariant Japan Co., Ltd. E2: "N.P.1500-S" (magnesium stearate) manufactured by Tannan Chemical Industry Co., Ltd.

[0100] <1.6. Coupling Agent> F: "KBE-903" (3-aminopropyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

[0101] 2. Preparation of pellets The raw materials were weighed and mixed in a tumbler according to the blending ratios shown in Tables 1 and 2, and then charged into a twin-screw extruder to obtain pellets. The twin-screw extruder was set at a temperature of 250°C to 300°C, and the kneading time was 5 to 10 minutes.

[0102] 3. Evaluation Methods 3.1. Relative Viscosity of Polyamide (98% Sulfuric Acid Solution Method) Using an Ubbelohde viscosity tube, the relative viscosity of the polyamide was measured at 1 g / dL and 25° C. using 98% sulfuric acid according to JIS K6920-2:2009.

[0103] 3.2. Melting Point of Polyamide The melting point of polyamide was measured using a differential scanning calorimeter (EXSTAR 6000 manufactured by Seiko Instruments Inc.) at a temperature rise rate of 20° C. / min to determine the endothermic peak temperature.

[0104] 3.3. Arithmetic mean roughness (Ra) The pellets were molded into a plate having a thickness of 2 mm, a length of 100 mm, and a width of 100 mm using an injection molding machine with a cylinder temperature of 260°C and a mold temperature of 90°C. The arithmetic mean height of the profile curve elements on the surface of the plate, specifically the arithmetic mean roughness (Ra), was measured using a method in accordance with JIS B 0601:2013. The plate was also treated at 150°C for 1,000 hours, and the arithmetic mean roughness (Ra) was measured using the same method, i.e., the method in accordance with JIS B 0601:2013.

[0105] 3.4. Spectral Peak Area Ratio The pellets were molded into a plate with a thickness of 2 mm, length of 100 mm, and width of 100 mm, with an arithmetic mean roughness (Ra) of 0.1 μm, using an injection molding machine with a cylinder temperature of 260°C and a mold temperature of 90°C. The plate was treated at 150°C for 1000 hours, and then a sample was cut out from the plate. The sample was embedded in epoxy resin, and the embedded sample was cut along a plane perpendicular to the surface of the sample. The cross section revealed by this cutting was polished smoothly using a rotary polisher with abrasive paper attached. The polished cross section sample was subjected to microscopic infrared measurement using a reflection method (apparatus used: Agilent Technologies, Inc., Cary 670 FTIR / Cary 620 FTIR microscope). A 64x64 MCTFPA detector was used, with a resolution of 8 cm. －１ The measurement was performed with an accumulation of 256 times. The polished cross-section sample was positioned so that the y-axis of the measurement surface and the cross-section edge were parallel, and the cross-section edge was included in the range of x = 1 to 10 of the measurement range (specifically, 350 μm square. The measurement points were x = 0 to 63, y = 0 to 63, 4096 points). The spectral data obtained by the microscopic infrared measurement was subjected to Kramers-Kronig transformation using the attached analysis software. The spectrum of each measurement point was confirmed from the left end of the measurement range, and the main peak derived from the embedding resin (approximately 1510 cm because an epoxy resin, specifically bisphenol A epoxy, was used as the embedding resin in this case) was found. －１ The measurement point at a depth of 50 μm from the surface of the sample was determined to be the value of x (the edge of the sample surface) at which the number of points where the main peak (appearing in the figure) was detected first fell below half, plus 9. This is because the length between measurement points was approximately 5.5 μm. From the 64 measurement points at a depth of 50 μm from the surface of the sample, a distance of 1665 cm －１ ~1630cm －１ Eight measurement points were selected in descending order of peak area, and the average spectrum of these eight points was taken as the spectrum at a depth of 50 μm from the surface of the sample. Since the ratio of inorganic filler was high at the surface of the sample and a spectrum with sufficient intensity could not be obtained, a spectrum at a depth of 50 μm from the surface of the sample was obtained using the above procedure. In the spectrum at a depth of 50 μm from the surface of the sample, －１ ~1700cm－１ and the peak area of ​​1665 cm －１ ~1630cm －１ The peak area of ​​1750 cm －１ ~1700cm －１ The peak at 1665 cm is a carbonyl group peak that increases with the degradation of polyamide. －１ ~1630cm －１ The peak at 1800 cm is a peak derived from the carbonyl group of the amide bond. －１ ~1780cm －１ and the average absorbance at 1600 cm －１ ~1580cm －１ The line connecting the average absorbance of 1750 cm and 1750 cm was set as the baseline, and the peak areas were calculated. －１ ~1700cm －１ The peak area of ​​1665 cm －１ ~1630cm －１ The ratio of the peak area of ​​1750 cm －１ ~1700cm －１ Peak area / 1665 cm －１ ~1630cm －１ The peak areas (i.e., peak area ratios) were calculated.

[0106] 3.5. Bending Strength The pellets were molded into test specimens having a shape specified in JIS K 7139:2009, A1, using an injection molding machine with a cylinder temperature of 260°C and a mold temperature of 80°C. A bending test was conducted on these test specimens in accordance with ISO 178:2010 to measure their bending strength (i.e., the maximum bending stress that the test specimen could withstand during the bending test). The bending test was conducted using Method A, with a support distance of 64 mm, a test speed of 2 mm / min, and no change in strain rate during the test.

[0107] <3.6. Thermal Conductivity> The pellets were molded into a plate with a thickness of 2 mm, a length of 100 mm, and a width of 100 mm using an injection molding machine with a cylinder temperature of 260°C and a mold temperature of 90°C. The center of the plate was cut into a disk with a width of approximately 10 mm. The thermal diffusion coefficient, density, and specific heat of the disk-shaped sample were measured. The thermal diffusion coefficient was measured using the laser flash method in accordance with ASTM E1461. The density was measured using the immersion method in accordance with ISO 1183:1987. The specific heat was measured using a method in accordance with JIS K 7123:1987. The thermal conductivity was then calculated using the following formula. The thermal conductivity of the molded flat plate after treatment at 150° C. for 1000 hours was also determined using the same procedure.

[0108] 3.7. Adhesion to Gap Filler Two plate-shaped molded articles were molded using the pellets, each having an arithmetic mean roughness (Ra) of 0.1 μm and measuring 3 mm in thickness, 55 mm in length, and 15 mm in width. The gap filler was applied to the longitudinal end of one of the two surfaces of the first molded article, so that the gap filler was 15 mm square and 1 mm thick. The gap filler was sandwiched and bonded to the longitudinal end of one of the two surfaces of the second molded article. This resulted in an object consisting of the first molded article, the second molded article, and the gap filler bonding them together. A test piece measuring 95 mm in length and 15 mm in width was cut from this object. The test piece was left in an environment of 130°C for 1,000 hours (i.e., after undergoing accelerated aging treatment), and then subjected to a tensile test. In the tensile test, the first molded part of the test piece was gripped with a first gripper, and the second molded part of the test piece was gripped with a second gripper, and the test piece was then pulled in the longitudinal direction of the test piece. In this tensile test, if the shear bond strength (i.e., the stress calculated by dividing the load by the bond area) when peeling occurred between the first molded part or the second molded part and the gap filler was less than 0.1 MPa, it was judged as ×. On the other hand, if the shear bond strength when peeling occurred was 0.1 MPa or more, it was judged as ○.

[0109] 4. Results The table containing the results is shown below. In these tables, the properties marked "after thermal degradation" refer to the properties after treatment at 150°C for 1000 hours.

[0110] The smaller the peak area ratio and the smaller the difference in arithmetic mean roughness (Ra) before and after treatment at 150° C. for 1000 hours, the better the adhesion to the gap filler (see Examples 1 to 15 and Comparative Examples 1 to 6).

[0111] The flat molded product of Example 1, which had a peak area ratio of 0.03, and the flat molded product of Comparative Example 2, which had a peak area ratio of 0.14, were treated at 150°C for 1,000 hours, and the surfaces were observed. The surface of the flat molded product of Example 1 was found to be smoother than the surface of the flat molded product of Comparative Example 2 (see Figures 1 and 2). On the surface of the flat molded product of Comparative Example 2, there were many exposed areas of the thermally conductive inorganic filler and fibrous inorganic reinforcing material, and there were also many cracks in the areas where the resin (i.e., polyamide) was present.

[0112] The combined use of a hindered phenolic antioxidant and cupric bromide synergistically reduced the peak area ratio. In this regard, the peak area ratio was reduced by 0.03 when 0.2 parts by mass of the hindered phenolic antioxidant was used (see Comparative Examples 1 and 2). The peak area ratio was reduced by 0.02 parts by mass of cupric bromide (see Comparative Examples 1 and 6). On the other hand, the combined use of 0.2 parts by mass of the hindered phenolic antioxidant and 0.02 parts by mass of cupric bromide reduced the peak area ratio by 0.14 (see Comparative Example 1 and Example 2).

[0113] The combined use of a hindered phenolic antioxidant and cupric bromide synergistically reduced the degree of deterioration in arithmetic mean roughness after 1000 hours of treatment at 150°C. In this regard, 0.2 parts by mass of a hindered phenolic antioxidant reduced the arithmetic mean roughness by 0.8 μm after 1000 hours of treatment at 150°C (see Comparative Examples 1 and 2). 0.02 parts by mass of cupric bromide reduced the arithmetic mean roughness by 2.1 μm after 1000 hours of treatment at 150°C (see Comparative Examples 1 and 6). On the other hand, the combined use of 0.2 parts by mass of a hindered phenolic antioxidant and 0.02 parts by mass of cupric bromide reduced the arithmetic mean roughness by 3.8 μm after 1000 hours of treatment at 150°C (see Comparative Example 1 and Example 2).

[0114] When no thermally conductive inorganic filler was used, the thermal conductivity of the molded article was excessively low (see Comparative Example 4).When no fibrous inorganic reinforcing material was used, the bending strength of the molded article was excessively low (see Comparative Example 5).

[0115] INDUSTRIAL APPLICABILITY The present invention can provide polyamide compositions and molded articles, and is therefore industrially applicable.

Claims

1. A composition containing polyamide, a fibrous inorganic reinforcing material, and a thermally conductive inorganic filler, which exhibits a peak at 1750 cm in the infrared absorption spectrum when left in a temperature environment of 150 °C for 1000 hours. －１ ~1700cm －１ The peak area of ​​1665 cm －１ ~1630cm －１ and when the polyamide composition is left in a temperature environment of 150° C. for 1,000 hours, the difference in arithmetic average roughness (Ra) before and after the composition is left in such a temperature environment is 1.5 μm or less in absolute value.

2. The polyamide composition according to claim 1, having a bending strength of 120 MPa or more and a thermal conductivity of 0.60 W / m·K or more.

3. The polyamide composition according to claim 1, wherein the difference is 1.0 μm or less in absolute value.

4. The polyamide composition of claim 1, further comprising an antioxidant and a stabilizer.

5. The polyamide composition of claim 1, wherein the polyamide comprises a crystalline polyamide.

6. The polyamide composition according to claim 1, wherein the polyamide has a relative viscosity of 2.0 or more and 3.6 or less.

7. The polyamide composition according to claim 1, wherein the content of the thermally conductive inorganic filler is 35 mass% or more.

8. The polyamide composition according to claim 1, wherein the thermally conductive inorganic filler is surface treated.

9. The polyamide composition according to claim 1, which is used as a raw material for a molded article provided with a gap filler.

10. The polyamide composition of claim 1, further comprising a phenolic antioxidant and a copper compound.

11. The polyamide composition according to claim 10, wherein the phenolic antioxidant has a hindered structure, and the copper compound is at least one selected from the group consisting of copper acetate, copper iodide, and copper bromide.

12. The polyamide composition of claim 1, further comprising a mold release agent.

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

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