Polyamide composition and molded article

Abstract

To provide a polyamide composition allowing for molding a molded article having excellent heat dissipation properties, strength and moisture resistance and to provide a molded article having excellent heat dissipation properties, strength and moisture resistance.SOLUTION: There is a polyamide composition comprising a polyamide, a fibrous inorganic reinforcing material and a sintered body containing magnesium oxide, wherein the sintered body is coated with a silica film and the content of the sintered body is 35 mass% or more. Some fibrous inorganic reinforcing material can improve strength, specifically bending strength. Moreover, the sintered body containing magnesium oxide can improve heat dissipation properties, strength and moisture resistance compared to the case where non-sintered magnesium oxide particles, specifically, light burnt magnesia, is used. Furthermore, the sintered body is coated with a silica film, which further improves heat dissipation properties, strength, and moisture resistance. The heat dissipation properties can be further improved when the content of the sintered body is 35 mass% or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] It is known to compound an inorganic substance having high thermal conductivity (hereinafter sometimes referred to as a "thermally conductive inorganic filler") in order to impart thermal conductivity to a polyamide composition, that is, to impart heat dissipation properties.

[0003] Among thermally conductive inorganic fillers, magnesium oxide particles are particularly useful because they are inexpensive, have excellent thermal conductivity, and have low hardness, which has the advantage of reducing screw wear in extruders and molding machines when producing polyamide compositions and molded articles.

[0004] However, magnesium oxide particles (e.g., light-burned magnesia) reduce the strength of polyamide compositions. This is because the magnesium oxide particles have poor dispersibility in polyamide and poor adhesion to polyamide, resulting in embrittlement of the polyamide composition. Magnesium oxide particles also reduce the moisture resistance of polyamide compositions. This is because the magnesium oxide that constitutes the magnesium oxide particles reacts with moisture. The reduction in strength and moisture resistance is particularly noticeable when a large amount of magnesium oxide particles is incorporated.

[0005] As methods for improving such drawbacks of magnesium oxide particles, for example, a method of coating magnesium oxide particles with a fatty acid metal salt (see Patent Document 1) and a method of blending a maleic anhydride-modified ethylene-octene copolymer together with a thermally conductive inorganic filler (see Patent Document 2) have been proposed.In addition, a method of using a sintered body containing magnesium oxide, calcium oxide, and silicon oxide (see Patent Document 3) and a method of surface treating magnesium oxide particles with an oligomeric reactive siloxane (see Patent Document 4) have also been proposed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2018 / 180123 [Patent Document 2] Patent No. 6296197 [Patent Document 3] Patent No. 5993824 [Patent Document 4] Patent No. 5602650 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, with the demand for weight reduction and the spread of electric vehicles (EVs), there has been a demand for polyamide compositions that are excellent not only in heat dissipation properties but also in other physical properties (for example, strength and moisture resistance).

[0008] An object of the present invention is to provide a polyamide composition that can be molded into molded articles having excellent heat dissipation properties, strength, and moisture resistance.An object of the present invention is also to provide molded articles having excellent heat dissipation properties, strength, and moisture resistance. [Means for solving the problem]

[0009] In order to solve this problem, the present invention has the following configuration [1]. [1] Polyamide and a fibrous inorganic reinforcing material; and a sintered body containing magnesium oxide, the sintered body is coated with a silica film, The content of the sintered body is 35% by mass or more. Polyamide composition. Here, the "sintered body containing magnesium oxide" is a granular sintered body in which some particles containing magnesium oxide are bonded together.

[0010] According to [1], the strength, specifically the bending strength, can be improved by using fibrous inorganic reinforcing materials.

[0011] Furthermore, a sintered body containing magnesium oxide can improve heat dissipation and strength compared to the use of unsintered magnesium oxide particles, specifically light-burned magnesia. This is explained below. Magnesium oxide reacts with moisture to form magnesium hydroxide. The more this reaction progresses, the more the volume of the magnesium oxide expands. When this reaction occurs in a polyamide composition, voids form at the interface between the magnesium oxide and the resin (e.g., polyamide). In contrast, according to [1], a sintered body containing magnesium oxide can suppress this reaction, thereby suppressing the generation of voids and reducing the size of any voids that may form. This is thought to be because the sintering process used to produce the sintered body forms parts (i.e., necks) that bond the magnesium oxide-containing particles together, or some kind of layer, in the particles. Therefore, the deterioration of heat dissipation and strength that can be caused by voids can be suppressed. Therefore, a sintered body can improve heat dissipation and strength.

[0012] The use of a sintered body containing magnesium oxide can also improve moisture resistance compared to the use of unsintered magnesium oxide particles (specifically, light-burned magnesia). Specifically, it can suppress a decrease in tensile strength in a high-humidity environment. This will be explained below. Magnesium oxide reacts with moisture to form magnesium hydroxide. The more this reaction progresses, the more the volume of the magnesium oxide expands. If this reaction progresses in a polyamide composition, the tensile strength of the polyamide composition decreases. In contrast, according to [1], the use of a sintered body containing magnesium oxide can suppress this reaction. This is thought to be because the sintering process during production of the sintered body forms parts that bond the magnesium oxide-containing particles together (i.e., necks) or some kind of layer on the particles. Therefore, it is possible to suppress a decrease in tensile strength that could be caused by this reaction (i.e., the reaction between magnesium oxide and moisture). Therefore, the use of a sintered body can suppress a decrease in tensile strength in a high-humidity environment, i.e., improve moisture resistance.

[0013] Furthermore, since the sintered body is coated with a silica film, the sintered body has even better moisture resistance, which can further improve the heat dissipation properties, strength, and moisture resistance of the polyamide composition.

[0014] Furthermore, by making the content of the sintered body 35% by mass or more, the heat dissipation property can be further improved.

[0015] In the present invention, the following configurations [2] to [9] are preferred.

[0016] [2] The polyamide composition according to [1], wherein the content of the fibrous inorganic reinforcing material is 10% by mass or more. According to [2], the strength can be further improved by setting the content of the fibrous inorganic reinforcing material to 10 mass % or more.

[0017] [3] The polyamide composition according to [1] or [2], wherein the polyamide is a crystalline polyamide. According to [3], crystalline polyamides can improve mechanical properties.

[0018] [4] The polyamide composition according to [3], wherein the relative viscosity of the crystalline polyamide is 2.0 or more and 3.6 or less. Here, the relative viscosity is a value measured at 25°C using 98% sulfuric acid and 1 g / dL of a sample (i.e., polyamide) in accordance with JIS K6920-2:2009.

[0019] [5] The polyamide composition according to any one of [1] to [4], further comprising an antioxidant. According to [5], the antioxidant can suppress oxidative degradation of the polyamide composition.

[0020] [6] The polyamide composition according to any one of [1] to [5], further comprising a hindered phenol-based antioxidant.

[0021] [7] The polyamide composition according to any one of [1] to [6], further comprising a mold release agent. According to [7], when the polyamide composition contains a mold release agent, when the polyamide composition is molded in a mold, it becomes easy to remove the molded product from the mold.

[0022] [8] The polyamide composition according to [7], wherein the release agent is a higher fatty acid ester compound.

[0023] [9] The bending strength is 120 MPa or more, The thermal conductivity is 0.60 W / m K or more. The tensile strength retention rate after high humidity treatment, i.e., leaving the specimen standing for 168 hours in an environment of 80°C and a relative humidity of 95%RH, is 40% or more, and the tensile strength retention rate is a value calculated by the following formula: Tensile strength retention rate = (tensile strength of polyamide composition test piece subjected to high humidity treatment / tensile strength of polyamide composition test piece not subjected to high humidity treatment) × 100 The polyamide composition according to any one of [1] to [8].

[0024]

[10] A molded article comprising the polyamide composition according to any one of [1] to [9]. [Effects of the Invention]

[0025] According to the present invention, a polyamide composition capable of being molded into a molded article having excellent heat dissipation properties, strength, and moisture resistance can be provided. According to the present invention, a molded article having excellent heat dissipation properties, strength, and moisture resistance can also be provided. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described in detail.

[0027] <1. Polyamide composition> <1.1. Polyamide> The polyamide composition of the present embodiment contains a polyamide, which is a polymer having an amide bond (—NHCO—) in the main chain.

[0028] The polyamide is preferably a crystalline polyamide because it can improve the mechanical properties of the polyamide composition. Examples of the crystalline polyamide include polyamide 6 (PA6), polyamide 66 (PA66), polyamide 46 (PA46), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 610 (PA610), polyamide 612 (PA612), polymetaxylylene adipamide (PAMXD6), hexamethylenediamine-terephthalic acid polymer (PA6T), hexamethylenediamine-terephthalic acid and adipic acid polymer (PA6T / 6 ... Examples include diamine-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. Among these, polyamide 6 is preferred because of its excellent moldability, melt flowability, and mechanical properties.

[0029] 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, and 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.

[0030] 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, and may be 100 mol%.

[0031] 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 further improve strength. 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 excessive loss of fluidity when the polyamide composition is melted and allowed to flow, and can improve the dispersibility of the sintered body. The relative viscosity is a value measured in accordance with JIS K6920-2:2009 using 98% sulfuric acid, 1 g / dL of sample (i.e., polyamide), and 25°C.

[0032] In the polyamide composition of the present embodiment, the content of 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 polyamide.

[0033] The polyamide composition of the present embodiment may further 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 for which no crystalline melting peak is observed 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.

[0034] In particular, the amorphous polyamide preferably contains an aromatic component, since crystallization is easily suppressed. Preferred amorphous polyamides containing an aromatic component include polyamide 6T / 6I, which is made from terephthalic acid, isophthalic acid, and adipic acid, and polyamide 6T / 66, which is made from terephthalic acid, adipic acid, and hexamethylenediamine. Of these, polyamide 6T / 6I is more preferred from the viewpoint of moldability.

[0035] 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.

[0036] <1.2. Fibrous inorganic reinforcing materials> The polyamide composition of the present embodiment contains a fibrous inorganic reinforcing material. The fibrous inorganic reinforcing material can improve strength, specifically bending strength, as well as rigidity and heat resistance.

[0037] 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.

[0038] 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 the 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.

[0039] 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.

[0040] The fibrous inorganic reinforcing material is preferably treated with a coupling agent. This improves its affinity with polyamide and its mechanical properties. It also improves its 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. Examples of coupling agents that vary slightly include silane coupling agents, titanate coupling agents, and aluminum coupling agents. Among these, silane coupling agents such as aminosilane coupling agents and epoxysilane coupling agents are preferred. While pretreatment with a coupling agent is preferred, the coupling agent may also be added later.

[0041] 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 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. If it is 40% by mass or less, it is possible to avoid difficulties in producing molded articles using the polyamide composition.

[0042] <1.3. Sintered body> The polyamide composition of the present embodiment includes a sintered body containing magnesium oxide. Here, the "sintered body containing magnesium oxide" is a granular sintered body in which some particles containing magnesium oxide are bonded together. Since the sintered body contains magnesium oxide, it has high thermal conductivity.

[0043] A sintered body containing magnesium oxide can improve heat dissipation and strength compared to the use of unsintered magnesium oxide particles, specifically light-burned magnesia. This is explained below. Magnesium oxide reacts with moisture to form magnesium hydroxide. The more this reaction progresses, the more the volume of the magnesium oxide expands. When this reaction occurs in a polyamide composition, voids form at the interface between the magnesium oxide and the resin (e.g., polyamide). In contrast, according to [1], a sintered body containing magnesium oxide can suppress this reaction, thereby suppressing the generation of voids and reducing the size of any voids that may form. This is thought to be because the sintering process during production of the sintered body forms parts (i.e., necks) that bond the magnesium oxide-containing particles together, or some kind of layer, in the particles. Therefore, the deterioration of heat dissipation and strength that can be caused by voids can be suppressed. Therefore, a sintered body can improve heat dissipation and strength.

[0044] The use of a sintered body containing magnesium oxide can also improve moisture resistance compared to the use of unsintered magnesium oxide particles (specifically, light-burned magnesia). Specifically, it can suppress a decrease in tensile strength in a high-humidity environment. This will be explained below. Magnesium oxide reacts with moisture to form magnesium hydroxide. The more this reaction progresses, the more the volume of the magnesium oxide expands. If this reaction progresses in a polyamide composition, the tensile strength of the polyamide composition decreases. In contrast, according to [1], the use of a sintered body containing magnesium oxide can suppress this reaction. This is thought to be because the sintering process during production of the sintered body forms parts that bond the magnesium oxide-containing particles together (i.e., necks) or some kind of layer on the particles. Therefore, it is possible to suppress a decrease in tensile strength that could be caused by this reaction (i.e., the reaction between magnesium oxide and moisture). Therefore, the use of a sintered body can suppress a decrease in tensile strength in a high-humidity environment, i.e., improve moisture resistance.

[0045] The sintered body can be produced, for example, by mixing purified magnesium hydroxide (Mg(OH)2), silicon oxide (SiO2), and calcium oxide (CaO) and heating the mixture at a high temperature. The silicon oxide and calcium oxide can promote sintering. Heating can be carried out, for example, using a rotary kiln at about 1800°C for about 30 minutes. The sintered body obtained by heating may be sieved and classified as needed. The sintered body may also be surface-treated as needed.

[0046] The sintered body preferably contains silicon oxide (SiO2), and more preferably silicon oxide (SiO2) and calcium oxide (CaO). This is because the strength and moisture resistance of the sintered body can be controlled by adjusting the molar ratio of calcium oxide to silicon oxide (hereinafter sometimes referred to as the "Ca / Si ratio") (see Japanese Patent No. 5993824). Here, the number of moles of silicon oxide refers to the number of moles (MSi) of silicon element contained in the sintered body converted to silicon oxide (SiO2). The number of moles of calcium oxide refers to the number of moles (MCa) of calcium element contained in the sintered body converted to calcium oxide (CaO). Therefore, the Ca / Si ratio is a value expressed as MCa / MSi. The number of moles, molar ratio, mass % and other values ​​of each oxide contained in the sintered body can be measured by methods such as the ICP method using an inductively coupled plasma (ICP) optical emission spectrometer or chelometric titration using a chelating agent such as EDTA.

[0047] The Ca / Si ratio is preferably 0.1 or more, more preferably 0.4 or more, and even more preferably 0.8 or more. If it is 0.1 or more, the strength of the sintered body can be improved. On the other hand, the Ca / Si ratio is preferably less than 2.0, more preferably 1.5 or less, and even more preferably 1.2 or less. If it is less than 2.0, the moisture resistance of the sintered body can be improved.

[0048] The sintered body may contain magnesium oxide, silicon oxide (SiO2), calcium oxide (CaO), or a compound formed by reaction of these. The sintered body may also contain, for example, B2O3, Al2O3, Fe2O3, Na2SO4, etc.

[0049] The magnesium oxide content in the sintered body is preferably 85.0% by mass or more, more preferably 88.0% by mass or more, even more preferably 90.0% by mass or more, even more preferably 92.0% by mass or more, and even more preferably 94.0% by mass or more, based on 100% by mass of the sintered body. When the content is 85.0% by mass or more, the sintered body has excellent thermal conductivity. On the other hand, the magnesium oxide content is preferably 99.7% by mass or less, based on 100% by mass of the sintered body. When the content is 99.7% by mass or less, the sintered body contains a certain amount of other components, thereby improving moisture resistance.

[0050] The particle size of the sintered body, specifically the median diameter, 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, moisture resistance can be further improved. In addition, excessive decrease in fluidity when the polyamide composition is melted and flowed can be suppressed. The median diameter may be 30 μm or more, or 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 particle size is 200 μm or less, thermal conductivity can be further improved. The median diameter may be 80 μm or less. Here, the median diameter is D50, specifically the particle size at 50% of the cumulative particle size distribution on a volume basis in the sintered body.

[0051] The sintered body is preferably coated with a silica film, i.e., an organosilicon compound layer. That is, the sintered body preferably includes a silica film. By coating the sintered body with a silica film, the sintered body has even better moisture resistance, and the heat dissipation property, strength, and moisture resistance of the polyamide composition can be further improved.

[0052] To form the silica film, for example, an oligomeric reactive siloxane or a silane coupling agent can be used, with oligomeric reactive siloxane being preferred.

[0053] The oligomeric reactive siloxane is preferably a polymer containing a silane coupling agent. Specifically, the oligomeric reactive siloxane is preferably a polymer containing an alkoxysilane having a reactive group. The oligomeric reactive siloxane contains a reactive group. Specifically, the silane coupling agent contained in the oligomeric reactive siloxane contains a reactive group. Examples of the reactive group include a vinyl group, an amino group, an epoxy group, a methacryloxy group, an acryloxy group, and a mercapto group. Among these, a vinyl group, an amino group, and an epoxy group are preferred, and a vinyl group and an amino group are more preferred.

[0054] The oligomeric reactive siloxane may be a copolymer of a silane coupling agent and an alkoxysilane having no reactive group. Examples of alkoxysilanes having no reactive group include alkyltrialkoxysilanes, alkylmethyldialkoxysilanes, phenyltrialkoxysilanes, phenylmethyldialkoxysilanes, and tetraalkoxysilanes. Among these, alkyltrialkoxysilanes are preferred. The alkyl group of the alkyltrialkoxysilane or alkylmethyldialkoxysilane preferably has 1 to 18 carbon atoms. The alkyl group may be linear, branched, or cyclic. The oligomeric reactive siloxane may also be a homopolymer of the silane coupling agent. Examples of commercially available oligomeric reactive siloxanes include Dynasylan 6490 and Dynasylan 1146.

[0055] One method for surface treatment with an oligomeric reactive siloxane is to add the oligomeric reactive siloxane to the sintered body while stirring it before surface treatment, and then heat it (see Japanese Patent No. 5602650). At this time, heating may be achieved by frictional heat generated by high-speed stirring, by external heat supply, or by a combination of these.

[0056] A sintered body coated with a silica film (i.e., a sintered body including a silica film) can also be purchased. An example of a commercially available sintered body is "RF-50-AC" manufactured by Ube Material Industries, Ltd.

[0057] In the polyamide composition of this embodiment, the content of the sintered body is 35% by mass or more. By having a content of 35% by mass or more, heat dissipation properties can be further improved. The content of the sintered body is preferably 37% by mass or more, more preferably 38% by mass or more, and even more preferably 39% by mass or more. On the other hand, the content of the sintered body is preferably 55% by mass or less, more preferably 50% by mass or less, even more preferably 47% by mass or less, and even more preferably 45% by mass or less.

[0058] <1.4. Antioxidants> The polyamide composition of the present embodiment preferably contains an antioxidant, which can suppress oxidative degradation of the polyamide composition.

[0059] The antioxidant is preferably a hindered phenol-based antioxidant. Examples of the hindered phenol-based antioxidant 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 ("SONGNOX2450", molecular weight 633). These may be used alone or in combination of two or more.

[0060] In the polyamide composition of this embodiment, the content of the antioxidant is preferably 0.01% by mass or more, more preferably 0.1% by mass or more. When the content is 0.01% by mass or more, oxidative degradation of the polyamide composition over time can be prevented. 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.

[0061] <1.5. 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, it becomes easy to remove the molded product from the mold.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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. When 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.

[0066] <1.6. Other additives> The polyamide composition of the present embodiment may contain, for example, carbon black, copper oxide, alkali metal halide, light stabilizer, heat stabilizer, crystal nucleating agent, antistatic agent, pigment, dye, coupling agent, light-burned magnesia, etc. Of course, the polyamide composition of the present embodiment may contain a resin other than polyamide.

[0067] In the polyamide composition of this embodiment, the total content of the fibrous inorganic reinforcing material and the sintered body 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 sintered body is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 62% by mass or less.

[0068] <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. 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.

[0069] The higher the thermal conductivity of the polyamide composition of this embodiment, the better. The thermal conductivity is preferably 0.60 W / m·K or higher, more preferably 0.65 W / m·K or higher, and even more preferably 0.70 W / m·K or higher. 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.

[0070] The polyamide composition of this embodiment preferably has a higher tensile strength retention rate when subjected to high-humidity treatment. Specifically, the higher the tensile strength retention rate of a test piece made using the polyamide composition, i.e., a polyamide composition test piece, when left to stand for 168 hours in an environment of 80°C and a relative humidity of 95% RH (i.e., when subjected to high-humidity treatment), the more preferable it is. This is because the higher the tensile strength retention rate, the more likely it is that a molded article made using the polyamide composition will be prevented from losing rigidity or becoming embrittled when exposed to a high-humidity environment. Here, the tensile strength retention rate is calculated using the following formula. Tensile strength retention rate = (tensile strength of polyamide composition test piece subjected to high humidity treatment / tensile strength of polyamide composition test piece not subjected to high humidity treatment) × 100 The tensile strength retention is preferably 40% or more, more preferably 42% or more, and even more preferably 45% or more. The tensile strength retention may be 60% or less, 55% or less, 52% or less, or 50% or less. The tensile strength retention is a value measured by the method described in the Examples.

[0071] <1.8. Manufacturing method and applications> The polyamide composition of this embodiment can be produced by kneading at least polyamide, a fibrous inorganic reinforcing material, and a sintered body containing magnesium oxide 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. Among 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 to 15 minutes.

[0072] 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, and a sintered body containing magnesium oxide are melt-kneaded in a twin-screw extruder, and then strands are extruded, and the strands are cooled as needed, and cut as needed.

[0073] 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.

[0074] The polyamide composition of this embodiment can be used as a raw material for various molded products. In particular, it can be suitably used 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, components used around battery cases, and components used inside battery cases. In particular, it can be suitably used for producing peripheral components (e.g., components used around battery cases and components used inside battery cases) of electrical and electronic components (e.g., batteries) that generate high Joule heat (e.g., components used around battery cases and components used inside battery cases).

[0075] <2. Molded products> 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. [Example]

[0076] 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".

[0077] <1. Raw materials> The following raw materials were used: <1.1. Polyamide> A1: MEIDA's "M2000" (Polyamide 6, relative viscosity 2.0, melting point 225°C) A2: ZISAMIDE TP4208 (polyamide 6, relative viscosity 2.5, melting point 225°C) manufactured by Shusei Co., Ltd. A3: ZISAMIDE TP6603 (polyamide 6, relative viscosity 3.6, melting point 225°C) manufactured by Shusei Co., Ltd.

[0078] <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 Industries Co., Ltd.

[0079] <1.3. Thermally conductive inorganic filler> C1: RF-50-AC manufactured by Ube Material Industries, Ltd. (Surface-treated magnesium oxide sintered compact with a particle size of 50 μm. This sintered compact contains magnesium oxide, calcium oxide, and silicon oxide.) C2: Surface-treated sintered magnesium oxide with a particle size of 100 μm (details will be described later). C3: Surface-treated sintered magnesium oxide with a particle size of 10 μm (details will be described later). C4: "Starmag P" manufactured by Konoshima Chemical Co., Ltd. (light-burned magnesia with a particle size of 10 μm, no surface treatment) C5: Magnesium oxide sintered body with a particle size of 70 μm (details will be described later). C6: Surface-treated light-burned magnesia with a particle size of 50 μm (details will be described later).

[0080] Thermally conductive inorganic filler C2 A thermally conductive inorganic filler that is a magnesium oxide sintered body with a particle size of 100 μm (the sintered body contains magnesium oxide, calcium oxide, and silicon oxide) manufactured in accordance with Patent No. 5993824, and has been subjected to the same surface treatment as thermally conductive inorganic filler C1 (i.e., "RF-50-AC").

[0081] Thermally conductive inorganic filler C3 A thermally conductive inorganic filler in which a magnesium oxide sintered body with a particle size of 10 μm (the sintered body contains magnesium oxide, calcium oxide, and silicon oxide) manufactured in accordance with Patent No. 5993824 has been subjected to the same surface treatment as thermally conductive inorganic filler C1 (i.e., "RF-50-AC").

[0082] Thermally conductive inorganic filler C5 Magnesium oxide sintered body with a particle size of 70 μm, manufactured in accordance with Japanese Patent No. 5993824 (this sintered body contains magnesium oxide, calcium oxide and silicon oxide).

[0083] Thermally conductive inorganic filler C6 Light-burned magnesia with a particle size of 50 μm, which has been subjected to the same surface treatment as thermally conductive inorganic filler C1 (i.e., "RF-50-AC").

[0084] <1.4. Antioxidants> D...BASF's "SONGNOX 2450" (hindered phenolic antioxidant)

[0085] <1.5. Release Agent> E1: "Recorb WE-40" (aliphatic ester) manufactured by Clariant Japan Co., Ltd. E2: "NP1500-S" (magnesium stearate) manufactured by Tannan Chemical Industry Co., Ltd.

[0086] 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.

[0087] <3. Evaluation Method> 3.1. Relative viscosity of polyamide (98% sulfuric acid solution method) The relative viscosity of the polyamide was measured at 1 g / dL at 25°C using an Ubbelohde viscometer and 98% sulfuric acid according to JIS K6920-2:2009.

[0088] 3.2. Melting point of polyamide Using a differential scanning calorimeter ("EXSTAR 6000" manufactured by Seiko Instruments Inc.), measurements were carried out at a temperature rise rate of 20°C / min to determine the endothermic peak temperature.

[0089] 3.3. Flexural strength The pellets were molded into test specimens in the 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.

[0090] 3.4. Thermal conductivity The pellets were molded into flat plates measuring 2 mm thick, 100 mm long, and 100 mm wide using an injection molding machine with a cylinder temperature of 260°C and a mold temperature of 90°C. The center of each flat plate was cut into a disk approximately 10 mm wide. The thermal diffusivity, density, and specific heat of the disk samples were measured. The thermal diffusivity 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:

number

[0091] 3.5. Tensile strength retention The pellets were molded into test specimens in the shape specified in JIS K 7139:2009, Section A1, using an injection molding machine with a cylinder temperature of 260°C and a mold temperature of 80°C. These test specimens were then left to stand for 168 hours in an environment of 80°C and 95% relative humidity. In other words, these test specimens underwent high-humidity treatment. Tensile tests were then conducted in accordance with ISO 527-1:2012 to determine the tensile strength (i.e., the first maximum stress observed during the tensile test). The tensile tests were conducted at room temperature, with a test speed of 5 mm / min and a grip distance of 115 mm. Test specimens that were not subjected to high-humidity treatment were also subjected to tensile tests to determine the tensile strength. The tensile strength retention was then calculated using the following equation: Tensile strength retention rate = (tensile strength of test piece treated with high humidity / tensile strength of test piece not treated with high humidity) x 100 In all the examples and comparative examples, neither the test specimens that had been subjected to high humidity treatment nor the test specimens that had not been subjected to high humidity treatment broke before yielding.

[0092] <4.Results> A table containing the results is shown below. [Table 1] [Table 2]

[0093] When thermally conductive inorganic filler C3 (i.e., surface-treated magnesium oxide sintered body with a particle size of 10 μm) was used, the retention rate of tensile strength, bending strength, and thermal conductivity were superior to when thermally conductive inorganic filler C4 (i.e., light-burned magnesia with a particle size of 10 μm without surface treatment) was used (see Example 6 and Comparative Example 1).

[0094] When thermally conductive inorganic filler C1 (i.e., surface-treated magnesium oxide sintered body with a particle size of 50 μm) was used, the tensile strength retention rate, bending strength, and thermal conductivity were superior to when thermally conductive inorganic filler C6 (i.e., surface-treated light-burned magnesia with a particle size of 50 μm) was used (see Example 1 and Comparative Example 6).

[0095] When thermally conductive inorganic fillers C1, C2, and C3 were used, the tensile strength retention rate, bending strength, and thermal conductivity were superior to when thermally conductive inorganic filler C5 (i.e., magnesium oxide sintered body with a particle size of 70 μm and no surface treatment) was used (see Examples 1, 5, and 6, and Comparative Example 5).

[0096] For the thermally conductive inorganic fillers C1, C2, and C3, the smaller the particle size, the better the bending strength and thermal conductivity (see Examples 1, 5, and 6). On the other hand, the smaller the particle size, the lower the retention rate of tensile strength (see Examples 1, 5, and 6).

[0097] The more fibrous inorganic reinforcement, the better the flexural strength (see Examples 1, 10 and 12).

[0098] The higher the relative viscosity of the polyamide, the better the flexural strength but the lower the thermal conductivity (see Examples 1, 2 and 3). [Industrial Applicability]

[0099] INDUSTRIAL APPLICABILITY The present invention can provide polyamide compositions and molded articles, and is therefore industrially applicable.

Claims

1. Polyamide and a fibrous inorganic reinforcing material; and a sintered body containing magnesium oxide, the sintered body is coated with a silica film, The content of the sintered body is 35% by mass or more, In the sintered body, the molar ratio of CaO to SiO 2 is 0.1 or more and less than 2.

0. Polyamide composition.

2. The polyamide composition according to claim 1, wherein the content of the fibrous inorganic reinforcing material is 10% by mass or more.

3. The polyamide composition of claim 1 , wherein the polyamide is a crystalline polyamide.

4. The polyamide composition according to claim 3, wherein the crystalline polyamide has a relative viscosity of 2.0 or more and 3.6 or less.

5. The polyamide composition of claim 1 further comprising an antioxidant.

6. 10. The polyamide composition of claim 1, further comprising a hindered phenolic antioxidant.

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

8. The polyamide composition according to claim 7, wherein the release agent is a higher fatty acid ester compound.

9. The bending strength is 120 MPa or more and 230 MPa or less, The tensile strength retention rate after high humidity treatment, in which the sample is left standing for 168 hours in an environment of 80°C and a relative humidity of 95% RH, is 40% or more, and the tensile strength retention rate is a value calculated by the following formula: Tensile strength retention rate=(tensile strength of test piece of polyamide composition treated with high humidity / tensile strength of test piece of polyamide composition not treated with high humidity)×100 The polyamide composition of claim 1.

10. A molded article comprising the polyamide composition according to any one of claims 1 to 9.

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