Polyamide resin composition and molded article

Abstract

To provide a polyamide resin composition that is processed thin to have excellent flame retardancy, extrusion processability, and molding workability, particularly excelling in flow characteristics and weld strength during molding.SOLUTION: A polyamide resin composition includes (A) polyamide of 20-70 mass%, (B) brominated polystyrene of 10-35 mass%, (C) flame-retardant aid of 1-15 mass%, and (D) inorganic filler of 10-60 mass%, wherein the (B) brominated polystyrene has a bromine content of 64-71 mass%, and the (B) brominated polystyrene comprises a component with a weight average molecular weight of 1000-5000 and a component with a weight average molecular weight of 150000-200000.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polyamides, such as polyamide 6 (hereinafter sometimes abbreviated as "PA6") and polyamide 66 (hereinafter sometimes abbreviated as "PA66"), are used in fields such as automotive parts, machine parts, and electrical and electronic parts due to their excellent mechanical strength and heat resistance. In particular, the requirements for flame retardancy in electrical and electronic parts are high, and even higher levels of flame retardancy are required than the self-extinguishing properties inherently possessed by polyamide resins. For this reason, numerous studies have been conducted to achieve compliance with the V-0 rating of the Underwriters Laboratories UL94 standard.

[0003] A typical example of such a flame-retardant polyamide resin is a flame-retardant polyamide material using brominated polystyrene. For example, Patent Document 1 discloses a polyamide resin composition that exhibits excellent heat resistance, flame retardancy, and flowability in a reflow soldering process, as well as good thermal stability during molding. Patent Document 2 discloses a polyamide resin composition that significantly reduces the amount of gas generated during molding and is extremely less corrosive to molds. Patent Document 3 discloses a polyamide resin composition that exhibits high flame retardancy, high weld strength, and toughness.

[0004] However, in recent years, due to the increasing complexity of the structures of electrical and electronic components, there has been a trend toward thinner walls, and in addition to the generally required flame retardancy and mechanical strength (tensile strength and impact strength), there is an increasing demand for materials that have excellent weld strength and molding fluidity, and the above-mentioned documents have not necessarily been satisfactory. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2006 / 123469 [Patent Document 2] Japanese Patent Application Publication No. 10-168307 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-291249 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a polyamide resin composition which is excellent in flame retardancy, extrusion processability and molding processability even when thin-walled, and in particular in flow properties and weld strength during molding. [Means for solving the problem]

[0007] The present invention has been made in view of the above circumstances, and aims to stably provide polyamide resin compositions and molded articles having excellent mechanical properties (particularly weld strength), molding flowability, flame retardancy, etc.

[0008] As a result of extensive research into solving the above problems, the present inventors have found that a polyamide resin composition containing a brominated polystyrene having a specific molecular weight can solve the above problems, and have thus completed the present invention.

[0009] That is, the present invention is as follows. (1) A polyamide resin composition comprising (A) 20 to 70% by mass of polyamide, (B) 10 to 35% by mass of brominated polystyrene, (C) 1 to 15% by mass of a flame retardant synergist, and (D) 10 to 60% by mass of an inorganic filler, wherein the bromine content of the (B) brominated polystyrene is 64 to 71% by mass, and the polyamide resin composition contains a component having a weight-average molecular weight of 1,000 to 5,000 and a component having a weight-average molecular weight of 150,000 to 200,000. (2) The polyamide resin composition according to (1), wherein, in 100% by mass of the (B) brominated polystyrene, the proportion of components having a weight-average molecular weight of 1,000 to 5,000 is 1% by mass or more and 50% by mass or less, and the proportion of components having a weight-average molecular weight of 150,000 to 200,000 is 50% by mass or more and 99% by mass or less. (3) The polyamide resin composition according to (1) or (2), wherein, in 100% by mass of the (B) brominated polystyrene, the proportion of components having a weight-average molecular weight of 1,000 to 5,000 is 1% by mass or more and 20% by mass or less, and the proportion of components having a weight-average molecular weight of 150,000 to 200,000 is 80% by mass or more and 99% by mass or less. (4) The polyamide resin composition according to any one of (1) to (3), wherein the (B) brominated polystyrene has a molecular weight distribution Mw / Mn of 1.0 to 2.0 for a component having a weight average molecular weight of 1,000 to 5,000 and a molecular weight distribution Mw / Mn of 1.1 to 3.0 for a component having a weight average molecular weight of 150,000 to 200,000. (5) The polyamide resin composition according to any one of (1) to (4), wherein the (C) flame retardant aid is at least one selected from the group consisting of antimony oxides, tin oxides, iron oxides, and metal borates. (6) The polyamide resin composition according to any one of (1) to (5), wherein the (C) flame retardant synergist is diantimony trioxide. (7) The polyamide resin composition according to any one of (1) to (6), further comprising a compatibilizer (E), which is at least one selected from the group consisting of a copolymer of an aromatic vinyl compound and an α,β-unsaturated dicarboxylic acid anhydride and a polymer modified with an α,β-unsaturated dicarboxylic acid anhydride. (8) The polyamide resin composition according to (7), wherein the compatibilizer (E) is at least one selected from the group consisting of styrene-maleic anhydride copolymers and polyphenylene ether resins modified with α,β-unsaturated dicarboxylic acid anhydrides. (9) A molded article obtained by molding the polyamide resin composition according to any one of (1) to (8). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a polyamide resin composition which is excellent in flame retardancy, extrusion processability and molding processability even when thin, and which is particularly excellent in flow properties and weld strength during molding. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and can be practiced with various modifications within the scope of the gist. Note that in this specification, "polyamide" means a polymer having an amide (-NHCO-) ​​group in the main chain.

[0012] [(A) Polyamide] Examples of the polyamide (A) of this embodiment include polycondensates of dicarboxylic acids and diamines, ring-opening polymerization products of cyclic lactams, and polycondensates of aminocarboxylic acids. Specific examples include poly(caprolactam) (hereinafter abbreviated as polyamide 6), poly(hexamethylene adipamide) (hereinafter abbreviated as polyamide 66), poly(tetramethylene adipamide) (hereinafter abbreviated as polyamide 46), poly(hexamethylene sebacamide) (hereinafter abbreviated as polyamide 610), poly(hexamethylene dodecamide) (hereinafter abbreviated as polyamide 612), poly(undecamethylene adipamide) (hereinafter abbreviated as polyamide 116), poly(undecalactam) (hereinafter abbreviated as polyamide 11), and poly(dodecalactam) (hereinafter abbreviated as polyamide 12). Examples of suitable polyamides include aliphatic polyamides such as poly(metaxylylene adipamide) (hereinafter abbreviated as polyamide MXD6), poly(hexamethylene terephthalamide) (hereinafter abbreviated as polyamide 6T), poly(hexamethylene isophthalamide) (hereinafter abbreviated as polyamide 6I), poly(nonamethylene terephthalamide) (hereinafter abbreviated as polyamide 9T), poly(dodecamethylene terephthalamide) (hereinafter abbreviated as polyamide 12T), and poly(tetramethylene isophthalamide) (hereinafter abbreviated as polyamide 4I), as well as copolymers and mixtures of the above-mentioned aliphatic polyamides together, copolymers of polyamides containing aromatic components, and copolymers of aliphatic polyamides together and polyamides containing aromatic components.

[0013] If the melting point of the (A) polyamide is too high, the flame retardant will decompose during melt processing, increasing the amount of gas components, resulting in poor melt processability and a deterioration in flame retardant efficiency. On the other hand, if the melting point is too low, the heat resistance of the molded product, such as HDT (deflection temperature under load), will be reduced. Therefore, the melting point of the (A) polyamide used in this embodiment is preferably 240°C or higher and 270°C or lower. Examples of such (A) polyamides include polyamide 66, polyamide MXD6, 66 / 6I copolymer polyamide, 66 / 6 copolymer polyamide, 6I / 6T copolymer polyamide, 66 / 6I / 6T terpolymer polyamide, 66 / 6I / 6 terpolymer polyamide, and 6 / 6I / 6T terpolymer polyamide. Also included are polyamide resins having a melting point of 240°C or higher and 270°C or lower that are blended with these polyamides or low-melting-point polyamides such as polyamide 6.

[0014] More preferred are polyamide 66, 66 / 6 copolymer polyamide, and 66 / 6I copolymer polyamide, which have excellent moldability and physical properties, and also include polyamide resins having a melting point of 240° C. or higher and 270° C. or lower that are mixed with these polyamides, polyamide 6I, or polyamide 6. Most preferred is polyamide 66.

[0015] The molecular weight of the polyamide (A) of this embodiment may be within a moldable range. Polyamides with a relative viscosity (RV) of 10 to 70 as determined in accordance with ASTM D789 are particularly preferred, as they have good molding flowability and can maintain a high level of flame retardancy. The relative viscosity (RV) is more preferably in the range of 30 to 60, and most preferably 35 to 55. The relative viscosity (RV) is measured using 90% formic acid as a solvent, at a concentration of 3 g (polyamide) sample / 30 ml formic acid, at a temperature of 25°C.

[0016] (A) The terminal groups of polyamides generally contain amino groups or carboxy groups. The ratio of the amount of amino terminal groups to the total molar amount of the amount of amino terminal groups and the amount of carboxy terminal groups in the (A) polyamide [amount of amino terminal groups / (amount of amino terminal groups+amount of carboxy terminal groups)] is preferably 0.2 or more and less than 1.0, more preferably 0.1 or more and 0.5 or less, and even more preferably 0.2 or more and 0.4 or less. When the ratio of the amount of terminal groups is within the above range, molded articles obtained from the polyamide resin composition tend to have better color tone, mechanical strength, and flowability.

[0017] [(B) Brominated polystyrene] The brominated polystyrene (B) used in this embodiment is added to improve flame retardancy. In order to impart flame retardancy, flowability, and mechanical properties of welds to the polyamide resin composition of this embodiment, it is necessary to use a brominated polystyrene having a specific bromine content and a specific molecular weight.

[0018] (B) The method for producing brominated polystyrene is not particularly limited, and examples thereof include a method in which styrene monomers are polymerized to produce polystyrene, and then the benzene rings of the polystyrene are brominated, and a method in which brominated styrene monomers (bromostyrene, dibromostyrene, tribromostyrene, etc.) are polymerized to produce the brominated polystyrene.

[0019] The bromine content in (B) brominated polystyrene is preferably 64 to 71% by mass. By setting the bromine content to 64% by mass or more, the amount of bromine required for flame retardancy can be satisfied with a small amount of (B) brominated polystyrene blended, resulting in a polyamide resin composition that is excellent in heat resistance, flowability, toughness, low water absorption, and rigidity, as well as excellent flame retardancy, without impairing the properties of (A) polyamide. Furthermore, by setting the bromine content to 71% by mass or less, a polyamide resin composition that is less likely to undergo thermal decomposition during melt processing such as extrusion or molding, can be suppressed in gas generation, and also has excellent heat discoloration resistance can be obtained. Considering these balances, the bromine content is more preferably 65 to 69% by mass.

[0020] Furthermore, (B) brominated polystyrene preferably has a specific molecular weight, more preferably a first component having a high weight-average molecular weight and a second component having a low weight-average molecular weight, and may contain two components consisting of the first and second components. The weight-average molecular weight of the first component may be 150,000 to 200,000, and the weight-average molecular weight of the second component may be 1,000 to 5,000. The weight-average molecular weight in this specification can be determined by measurement using GPC (gel permeation chromatography). It is desirable for the first and second components to have sharp peaks. Even if the peaks overlap, the weight-average molecular weight and weight ratio can be calculated by separating the peaks assuming a Gaussian distribution. Generally, a small molecular weight distribution (Mw / Mn) tends to exhibit a sharp peak.

[0021] (B) Brominated polystyrene preferably contains a component having a weight-average molecular weight of 1000 to 5000 to improve fluidity, and also contains a component having a weight-average molecular weight of 150,000 to 200,000 from the viewpoints of flame retardancy and the physical properties of welds. It is more preferable that the proportion of the component having a weight-average molecular weight of 1000 to 5000 is 1% by mass to 50% by mass and the proportion of the component having a weight-average molecular weight of 150,000 to 200,000 is 50% by mass to 99% by mass. From the viewpoint of suppressing mold deposits, it is even more preferable that the proportion of the component having a weight-average molecular weight of 1000 to 5000 is 1% by mass to 20% by mass and the proportion of the component having a weight-average molecular weight of 150,000 to 200,000 is 80% by mass to 99% by mass. If (B) brominated polystyrene contains only components with a weight-average molecular weight of 5,000 or less, it will have poor compatibility with (A) polyamide, causing noticeable fuzzing in the strands during extrusion and making them more likely to break midway, resulting in reduced productivity, and (D) poor interfacial adhesion with the inorganic filler, resulting in reduced strength. If (B) brominated polystyrene is composed only of components with a weight-average molecular weight exceeding 150,000, it will have an extremely high melt viscosity, which will increase torque during extrusion, reducing productivity, and will also tend to reduce fluidity during molding.

[0022] The component of (B) brominated polystyrene having a weight-average molecular weight of 1,000 to 5,000 preferably has a molecular weight distribution (Mw / Mn) of 1.0 to 2.0, more preferably 1.05 to 1.30. The component of (B) brominated polystyrene having a weight-average molecular weight of 150,000 to 200,000 preferably has a molecular weight distribution (Mw / Mn) of 1.1 to 3.0, more preferably 1.5 to 2.5. By satisfying the above molecular weight distribution, higher fluidity during molding and mechanical properties of the welds can be obtained.

[0023] [(C) Flame retardant synergist] The polyamide resin composition of the present embodiment further contains a flame retardant aid (C), which allows the polyamide resin composition to have even more excellent flame retardancy.

[0024] The flame retardant aid (C) used in this embodiment is not particularly limited, and examples thereof include antimony oxides such as diantimony trioxide, diantimony tetroxide, diantimony pentoxide, and sodium antimonate; tin oxides such as tin monoxide and tin dioxide; iron oxides such as ferric oxide and γ-iron oxide; metal oxides such as zinc oxide, calcium oxide, zirconium oxide, manganese oxide, molybdenum oxide, cobalt oxide, bismuth oxide, chromium oxide, nickel oxide, copper oxide, and tungsten oxide; metal hydroxides such as magnesium hydroxide and aluminum hydroxide; metal borates such as zinc borate, magnesium borate, calcium borate, and aluminum borate; and silicones. These flame retardant aids (C) may be used alone or in combination of two or more.

[0025] The flame retardant aid (C) used in this embodiment is preferably at least one selected from antimony oxides, tin oxides, iron oxides, and metal borates, from the viewpoint of flame retardancy effect, more preferably antimony oxides, and particularly preferably diantimony trioxide.

[0026] To improve the flame retardancy, it is preferable to use a flame retardant auxiliary (C) having an average particle size of 0.01 to 10 μm. The average particle size can be measured using a laser diffraction scattering particle size distribution analyzer or a precision particle size distribution analyzer.

[0027] [(D) Inorganic filler] The polyamide resin composition of the present embodiment further contains (D) an inorganic filler, which allows the polyamide resin composition to have even more excellent mechanical properties such as toughness and rigidity.

[0028] The (D) inorganic filler used in the present embodiment is not particularly limited, and examples thereof include glass fibers, carbon fibers, calcium silicate fibers, potassium titanate fibers, glass flakes, talc, kaolin, mica, hydrotalcite, calcium carbonate, zinc carbonate, calcium hydrogen phosphate, wollastonite, silica, zeolite, alumina, boehmite, titanium oxide, silicon oxide, magnesium oxide, calcium silicate, sodium aluminosilicate, magnesium silicate, ketjen black, acetylene black, furnace black, carbon nanotubes, graphite, brass, copper, silver, aluminum, nickel, iron, calcium fluoride, montmorillonite, swellable fluoromica, and apatite. The (D) inorganic filler may be used alone or in combination of two or more.

[0029] As the (D) inorganic filler, from the viewpoints of rigidity and strength, glass fiber, carbon fiber, glass flake, talc, kaolin, mica, calcium carbonate, calcium hydrogen phosphate, wollastonite, silica, carbon nanotubes, graphite, calcium fluoride, montmorillonite, swellable fluoromica, apatite, and the like are preferred.

[0030] As the (D) inorganic filler, glass fiber and carbon fiber are more preferred, and among glass fiber and carbon fiber, those having a number average fiber diameter of 3 to 30 μm, a weight average fiber length of 100 to 750 μm, and an aspect ratio (L / D) of the weight average fiber length (L) to the number average fiber diameter (D) of 10 to 100 are more preferably used from the viewpoint of exhibiting high properties.

[0031] Furthermore, as the (D) inorganic filler, glass fibers are more preferred, and among glass fibers, those having a number average fiber diameter of 3 to 30 μm, a weight average fiber length of 10 to 500 μm, and an aspect ratio (L / D) of 3 to 100 are even more preferably used.

[0032] The number-average fiber diameter and weight-average fiber length of (D) the inorganic filler can be measured by dissolving a molded product of the polyamide resin composition in a solvent in which polyamide is soluble, such as formic acid, and then arbitrarily selecting, for example, 100 or more inorganic fillers from the resulting insoluble components and observing them with an optical microscope, a scanning electron microscope, or the like.

[0033] [(E) Compatibilizer] The polyamide resin composition of the present embodiment preferably further contains a compatibilizer (E), which can provide a polyamide resin composition with even more excellent flame retardancy and mechanical properties such as toughness and rigidity.

[0034] The compatibilizer (E) used in this embodiment is preferably a polymer containing an α,β-unsaturated dicarboxylic acid anhydride, and examples thereof include a polymer containing an α,β-unsaturated dicarboxylic acid anhydride as a copolymerization component and a polymer modified with an α,β-unsaturated dicarboxylic acid anhydride, and is preferably at least one selected from a copolymer of an aromatic vinyl compound and an α,β-unsaturated dicarboxylic acid anhydride and a polymer modified with an α,β-unsaturated dicarboxylic acid anhydride.

[0035] Examples of the α,β-unsaturated dicarboxylic acid anhydride include compounds represented by the following general formula (1).

[0036] [ka]

[0037] In general formula (1), R 1 and R 2 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0038] Examples of the α,β-unsaturated dicarboxylic acid anhydride include maleic anhydride and methylmaleic anhydride, with maleic anhydride being preferred. Examples of the polymer containing an α,β-unsaturated dicarboxylic acid anhydride as a copolymerization component include copolymers of aromatic vinyl compounds and α,β-unsaturated dicarboxylic acid anhydrides.

[0039] Examples of polymers modified with an α,β-unsaturated dicarboxylic acid anhydride include polyphenylene ether resins and polypropylene resins modified with an α,β-unsaturated dicarboxylic acid anhydride.

[0040] As the polymer containing an α,β-unsaturated dicarboxylic acid anhydride, a copolymer of an aromatic vinyl compound and an α,β-unsaturated dicarboxylic acid anhydride is preferred from the viewpoint of efficiency in improving flame retardancy (which is achieved even with a small amount added).

[0041] Examples of the aromatic vinyl compound used in this embodiment include compounds represented by the following general formula (2).

[0042] [ka]

[0043] In general formula (2), R 3 and R 4 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and k is an integer of 1 to 5.

[0044] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, and p-methylstyrene, with styrene being preferred. In this embodiment, when the polymer containing an α,β-unsaturated dicarboxylic acid anhydride contains an aromatic vinyl compound component, it is believed that the aromatic vinyl compound component has affinity with the brominated polystyrene (B), and the α,β-unsaturated dicarboxylic acid anhydride portion has affinity with or reacts with the polyamide (A), thereby helping to disperse and finely disperse the brominated polystyrene (B) in the polyamide matrix.

[0045] In terms of flame retardancy, flowability, thermal decomposition resistance, etc., the proportions of the aromatic vinyl compound component and the α,β-unsaturated dicarboxylic acid anhydride component in the copolymer of an aromatic vinyl compound and an α,β-unsaturated dicarboxylic acid anhydride are preferably 50 to 99 mass% for the aromatic vinyl compound component and 1 to 50 mass% for the α,β-unsaturated dicarboxylic acid anhydride component, more preferably 5 to 20 mass%, and even more preferably 8 to 15 mass%. By adjusting the proportion of the α,β-unsaturated dicarboxylic acid anhydride component in the copolymer to 1% by mass or more, a polyamide resin composition having excellent mechanical properties such as toughness and rigidity and excellent flame retardancy can be obtained. Furthermore, by adjusting the proportion of the α,β-unsaturated dicarboxylic acid anhydride component in the copolymer to 50% by mass or less, deterioration of the polyamide resin composition due to the α,β-unsaturated dicarboxylic acid anhydride can be prevented.

[0046] The compatibilizer (E) is preferably at least one selected from the group consisting of styrene-maleic anhydride copolymers and polyphenylene ether resins modified with α,β-unsaturated dicarboxylic acid anhydrides.

[0047] (Content of each ingredient) The content of the (A) polyamide in the polyamide composition of this embodiment can be 20% by mass or more and 70% by mass or less, for example, 23% by mass or more and 65% by mass or less, for example, 25% by mass or more and 60% by mass or less, relative to 100% by mass of the polyamide resin composition.

[0048] In the polyamide resin composition of the present embodiment, the content of the (B) brominated polystyrene is preferably 10 to 35 mass %, more preferably 15 to 30 mass %, and even more preferably 17 to 25 mass %, relative to 100 mass % of the polyamide resin composition. By setting the content of (B) brominated polystyrene to 10% by mass or more, a polyamide resin composition with excellent flame retardancy can be obtained. Furthermore, by setting the content of (B) brominated polystyrene to 35% by mass or less, it is possible to suppress the generation of decomposition gases during melt-kneading, the decrease in fluidity during molding, and the adhesion of contaminants to molding dies. Furthermore, it is possible to suppress the deterioration of mechanical properties such as toughness and rigidity, and the appearance of molded products.

[0049] The content of the (C) flame retardant aid in the polyamide resin composition is preferably 1 to 15 mass %, more preferably 2 to 10 mass %, based on 100 mass % of the polyamide resin composition. By including the (C) flame retardant aid in this range, a polyamide resin composition with even better flame retardancy can be obtained. Furthermore, by setting the content of the (C) flame retardant aid to 15 mass % or less, the viscosity during melt processing can be controlled within an appropriate range, thereby suppressing an increase in torque during extrusion, a decrease in moldability during molding, and a decrease in the appearance of molded products. Furthermore, a polyamide resin composition with excellent toughness and other properties can be obtained without impairing the properties of the polyamide resin composition, which already have excellent mechanical properties such as toughness and rigidity.

[0050] The content of the (D) inorganic filler in the polyamide resin composition is preferably 10 to 60 mass %, more preferably 13 to 50 mass %, and even more preferably 15 to 40 mass %, based on 100 mass % of the polyamide resin composition. By including 10% by mass or more of (D) inorganic filler, the mechanical properties such as strength and rigidity of the polyamide resin composition are improved favorably, and by setting the content of inorganic filler to 60% by mass or less, a polyamide resin composition having excellent extrusion processability and moldability can be obtained.

[0051] The content of the (E) compatibilizer in the polyamide resin composition is preferably 0.1 to 20 mass%, more preferably 0.5 to 20 mass%, even more preferably 1 to 15 mass%, and particularly preferably 2 to 10 mass%, based on 100 mass% of the polyamide resin composition. By including the (E) compatibilizer in this range, the effect of finely dispersing the (B) brominated polystyrene in the polyamide resin composition due to compatibilization can be enhanced, resulting in a polyamide resin composition with excellent flame retardancy and strength. Furthermore, by keeping the content of the (E) compatibilizer at 20 mass% or less, a polyamide resin composition with excellent strength can be obtained without impairing the properties of the polyamide resin composition, which have excellent mechanical properties such as toughness and rigidity.

[0052] In this embodiment, the total amount of (B) brominated polystyrene, (C) flame retardant aid, (D) inorganic filler, and (E) compatibilizer is 30 to 80 mass %, preferably 40 to 80 mass %, relative to 100 mass % of the polyamide resin composition. By making the total amount of (B) to (E) 30 mass % or more, it is possible to obtain a polyamide resin composition that is excellent in strength, rigidity, flame retardancy, etc., and also has an appropriate melt viscosity and excellent processability.

[0053] (Moldability improver) If necessary, a moldability improver may be added to the polyamide resin composition of the present embodiment, within a range that does not impair the object of the present embodiment. The moldability improver is not particularly limited, but examples thereof include higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, and higher fatty acid amides.

[0054] Examples of the higher fatty acids include saturated or unsaturated, straight-chain or branched aliphatic monocarboxylic acids having 8 to 40 carbon atoms, such as stearic acid, palmitic acid, behenic acid, erucic acid, oleic acid, lauric acid, and montanic acid. Among these, stearic acid and montanic acid are preferred.

[0055] The higher fatty acid metal salt is a metal salt of the higher fatty acid. As the metal element of the metal salt, elements of Groups 1, 2 and 3 of the periodic table, zinc, aluminum, etc. are preferred, and elements of Groups 1 and 2 such as calcium, sodium, potassium and magnesium, and aluminum, etc. are more preferred. Examples of higher fatty acid metal salts include calcium stearate, aluminum stearate, zinc stearate, magnesium stearate, calcium montanate, sodium montanate, calcium palmitate, and the like. Among these, metal salts of montanic acid and metal salts of stearic acid are preferred.

[0056] The higher fatty acid ester is an ester of the higher fatty acid and an alcohol. Esters of aliphatic carboxylic acids having 8 to 40 carbon atoms and aliphatic alcohols having 8 to 40 carbon atoms are preferred. Examples of fatty alcohols include stearyl alcohol, behenyl alcohol, and lauryl alcohol. Examples of higher fatty acid esters include stearyl stearate and behenyl behenate.

[0057] The higher fatty acid amide is an amide compound of the higher fatty acid. Examples of higher fatty acid amides include stearic acid amide, oleic acid amide, erucic acid amide, ethylene bisstearylamide, ethylene bisoleylamide, N-stearylstearylamide, and N-stearylerucic acid amide. Preferred higher fatty acid amides are stearic acid amide, erucic acid amide, ethylene bisstearylamide, and N-stearyl erucic acid amide, and more preferred are ethylene bisstearylamide and N-stearyl erucic acid amide.

[0058] These higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, and higher fatty acid amides may be used singly or in combination of two or more.

[0059] (deterioration inhibitor) If necessary, a degradation inhibitor may be added to the polyamide resin composition of the present embodiment, within a range that does not impair the object of the present embodiment, for the purpose of preventing thermal degradation and discoloration when heated, improving heat aging resistance, and weather resistance.

[0060] The deterioration inhibitor is not particularly limited, but examples thereof include copper compounds such as copper acetate and copper iodide; phenolic stabilizers such as hindered phenol compounds; phosphite stabilizers; hindered amine stabilizers; triazine stabilizers; and sulfur stabilizers. These deterioration inhibitors may be used alone or in combination of two or more.

[0061] (Other resins) If necessary, other resins may be added to the polyamide resin composition of the present embodiment, as long as the object of the present embodiment is not impaired. Such resins are not particularly limited, but include thermoplastic resins and rubber components, which will be described later.

[0062] Examples of the thermoplastic resin include polystyrene-based resins such as atactic polystyrene, isotactic polystyrene, syndiotactic polystyrene, AS resin, and ABS resin; polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; other polyamides (polyamides other than the polyamide used in this embodiment) such as nylon 6, 66, and 612; polyether-based resins such as polycarbonate, polyphenylene ether, polysulfone, and polyethersulfone; condensation-based resins such as polyphenylene sulfide and polyoxymethylene; acrylic-based resins such as polyacrylic acid, polyacrylic acid ester, and polymethyl methacrylate; polyolefin-based resins such as polyethylene, polypropylene, polybutene, and ethylene-propylene copolymer; halogen-containing vinyl compound-based resins such as polyvinyl chloride and polyvinylidene chloride; phenolic resins; and epoxy resins. These thermoplastic resins may be used singly or in combination of two or more.

[0063] Examples of the rubber component include natural rubber, polybutadiene, polyisoprene, polyisobutylene, neoprene, polysulfide rubber, thiokol rubber, acrylic rubber, urethane rubber, silicone rubber, epichlorohydrin rubber, styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), styrene-isoprene block copolymer (SIR), hydrogenated styrene-isoprene block copolymer (SEP), styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), styrene-butadiene random copolymer, hydrogenated styrene-butadiene random copolymer, and styrene-ethylene-propylene random copolymer. , styrene-ethylene-butylene random copolymer, ethylene-propylene copolymer (EPR), ethylene-(1-butene) copolymer, ethylene-(1-hexene) copolymer, ethylene-(1-octene) copolymer, ethylene-propylene-diene copolymer (EPDM), as well as core-shell types such as butadiene-acrylonitrile-styrene-core-shell rubber (ABS), methyl methacrylate-butadiene-styrene-core-shell rubber (MBS), methyl methacrylate-butyl acrylate-styrene-core-shell rubber (MAS), octyl acrylate-butadiene-styrene-core-shell rubber (MABS), alkyl acrylate-butadiene-acrylonitrile-styrene-core-shell rubber (AABS), butadiene-styrene-core-shell rubber (SBR), and siloxane-containing core-shell rubbers such as methyl methacrylate-butyl acrylate siloxane. These rubber components may be used singly or in combination of two or more.

[0064] [Method for producing polyamide resin composition] The method for producing the polyamide resin composition of the present embodiment is not particularly limited as long as it is a method of mixing (A) polyamide, (B) brominated polystyrene, (C) flame retardant aid, and (D) inorganic filler.

[0065] Examples of methods for mixing (A) polyamide, (B) brominated polystyrene, (C) flame retardant aid, and (D) inorganic filler include a method in which at least one selected from the group consisting of (A) polyamide, (B) brominated polystyrene, (C) flame retardant aid, and (D) inorganic filler is mixed using a Henschel mixer or the like, and the mixture is fed to a melt kneader and kneaded; and a method in which (A) polyamide, (B) brominated polystyrene, (C) flame retardant aid, (D) inorganic filler, and optionally (E) compatibilizer are mixed in advance using a Henschel mixer or the like in a single-screw or twin-screw extruder, and the mixture is fed to a melt kneader and kneaded, and then the (D) inorganic filler is optionally added from a side feeder.

[0066] The components constituting the polyamide resin composition may be supplied to the melt kneader by supplying all of the components to the same supply port at once, or by supplying each component from a different supply port.

[0067] The melt-kneading temperature is preferably about 1 to 100° C. higher than the melting point of the (A) polyamide, and more preferably about 10 to 50° C. higher. The shear rate in the mixer is 100 sec -1 The average residence time during kneading is preferably about 0.5 to 5 minutes. As the apparatus for melt-kneading, known apparatuses, for example, melt-kneaders such as a single-screw or twin-screw extruder, a Banbury mixer, and a mixing roll, are preferably used.

[0068] The amount of each component blended when producing the polyamide resin composition of the present embodiment is the same as the content of each component in the polyamide resin composition described above.

[0069] [Molded Article of Polyamide Resin Composition] By molding the polyamide resin composition of the present embodiment, a predetermined molded article can be obtained. The method for obtaining the molded product is not particularly limited, and any known molding method can be used. Examples of molding methods include extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, other material molding, gas-assisted injection molding, foam injection molding, low-pressure molding, ultra-thin-wall injection molding (ultra-high-speed injection molding), and in-mold composite molding (insert molding, outsert molding).

[0070] [Application] The molded article of the present embodiment contains the polyamide resin composition described above, and exhibits excellent surface appearance stability under severe molding conditions, excellent mechanical properties of welds, and excellent flame retardancy, making it suitable for a variety of applications, including automotive, electrical and electronic, mechanical and industrial, office equipment, and aerospace. [Example]

[0071] The present invention will be described in detail below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples.

[0072] First, the components of polyamide, the methods for measuring the physical properties, and the methods for evaluating the characteristics are shown below.

[0073] [Measurement method] <Viscosity RV of polyamide in formic acid solution> The polyamide was dissolved in formic acid and measured according to ASTM D789.

[0074] <Polyamide end ratio> Amino terminal amount ([NH2]) In the polyamides obtained in the Examples and Comparative Examples, the amount of amino terminals bound to the polymer terminals was measured by neutralization titration as follows. 3.0 g of polyamide was dissolved in 100 mL of 90% by mass aqueous phenol solution, and the resulting solution was titrated with 0.025 N hydrochloric acid to determine the amount of amino terminals (μequivalents / g). The endpoint was determined from the indicated value of the pH meter.

[0075] Carboxyl terminal amount ([COOH]) In the polyamides obtained in the Examples and Comparative Examples, the amount of carboxyl terminals bonded to the polymer terminals was measured by neutralization titration as follows. 4.0 g of polyamide was dissolved in 50 mL of benzyl alcohol, and the resulting solution was titrated with 0.1 N NaOH to determine the amount of carboxyl terminals (μequivalents / g). The endpoint was determined from the color change of the phenolphthalein indicator.

[0076] The measured amounts of amino terminals ([NH2]) and carboxyl terminals ([COOH]) were used to calculate the total amount of active terminals ([NH2] + [COOH]) and the ratio of the amount of amino terminals to the total amount of active terminals ([NH2] / ([NH2] + [COOH])).

[0077] <Molecular weight measurement of brominated polystyrene> GPC measurement conditions GPC device: HLC-8320GPC (Tosoh) Column: TSKgel GMHHR-H (7.8 mm I.D. x 30 cm) x 2 (Tosoh) Eluent: Chloroform (Fujifilm Wako Pure Chemical Industries, Ltd., HPLC grade amylene additive) Detector: Differential refractometer (RI detector), polarity = (+) Flow rate: 1.0mL / min. Column temperature: 40℃ Sample concentration: 2 mg / mL Sample injection volume: 100 μL Sample pretreatment: The sample was weighed, a predetermined amount of eluent was added, and the sample was left to stand overnight at room temperature, then heated and dissolved at 50°C for 1 hour. After that, the sample was gently shaken and filtered through a 0.45 μm PTFE cartridge filter. Furthermore, no undissolved matter was found in any of the samples when the sample solution was visually inspected. Calibration curve: A cubic approximation curve using standard polystyrene (PS) (manufactured by Tosoh Corporation) was used. Therefore, the obtained value is the molecular weight converted into PS.

[0078] <Tensile strength> The equipment used was an "FN3000" manufactured by Nissei Plastic Industrial Co., Ltd. Each polyamide composition was molded under injection molding conditions of a cylinder temperature of 290°C, a mold temperature of 80°C, and a 10-second injection and 10-second cooling time, to obtain molded articles (ISO test pieces). Tensile strength was measured using the ISO test pieces in accordance with ISO 527. The measured values ​​were expressed as the average of n = 6.

[0079] <Weld strength> A test specimen was obtained by molding using an injection molding machine (PS40E, manufactured by Nissei Plastic Industrial Co., Ltd.) equipped with a mold that allowed molten resin to flow from both longitudinal ends of a shape measuring 127 mm in length, 12.7 mm in width, and 1.6 mm in thickness, forming a weld in the center in the longitudinal direction. Tensile tests were conducted on these molded test specimens according to a method in accordance with ISO 527, except that the chuck distance was 50 mm and the tensile speed was 50 mm / min, and the tensile strength was determined. The measured value was the average of n = 6.

[0080] <Flame retardancy evaluation> Measurements were carried out using the UL94 method (a standard established by Underwriters Laboratories Inc., USA). Test specimens (127 mm long, 12.7 mm wide, and 0.75 mm or 0.3 mm thick) were prepared by attaching a UL test specimen mold (mold temperature = 80°C) to an injection molding machine (PS40E, manufactured by Nissei Kogyo Co., Ltd.) and molding the polyamide resin composition at a cylinder temperature of 300°C. The injection pressure was set to 2% of the full filling pressure used to mold the UL test specimen. Flame retardancy ratings were determined in accordance with the UL94 standard (vertical flame test).

[0081] As an index for the V-0 rating criteria, the test specimen with the shortest total flaming burning time (t1 + t2) after the end of two flame applications (total of 10 applications) for each of the five test specimens, and with no flame reaching the clamps that secure the test specimens, was evaluated as having excellent flame retardancy. Note that to obtain a V-0 rating under UL94, the total flaming burning time must be 50 seconds or less, and no flame must reach the clamps.

[0082] <Liquidity> The polyamide resin composition was injection molded under the following conditions, and the flow length (spiral flow value) was measured by measuring the length of the molded piece. Before measuring the spiral flow value, the pellets were dried at 100°C for 16 to 24 hours, and the moisture content of the pellets was confirmed to be less than 300 ppm, and then the measurement was performed under the following conditions.

[0083] Injection molding machine: Toshiba Machine Co., Ltd. EC75S Measurement mold: Spiral mold with inner groove width (cavity) of 10 mm and thickness of 1 mm Mold temperature: 80℃ Set temperature: 285℃ Injection pressure: 60 MPa (injection speed is controlled by pressure at the maximum setting) Injection time: 10 seconds Cooling time: 10 seconds

[0084] [Raw materials] <(A) Polyamide resin> Using a 40 L autoclave, polyamide 66 with the end group concentrations shown in (A-1) and (A-2) below was polymerized. The end groups were adjusted by the type and amount of end group modifier added, and the melt-polymerized polyamide was taken out in the form of strands from the bottom nozzle to obtain polyamide pellets.

[0085] (A-1) Polyamide 66: Formic acid relative viscosity (RV) = 41, terminal amino group ratio = 75.5 meq / kg (59%), terminal carboxyl group = 52.1 meq / kg (41%) (A-2) Polyamide 66: Formic acid relative viscosity (RV) = 36, terminal amino group ratio = 38 milliequivalents / kg (30%), terminal carboxyl group = 90 milliequivalents / kg (70%). Other than that, it is the same as Polyamide 1. (A-3) Polyamide 6 (manufactured by Ube Industries, model number: SF1013A, formic acid relative viscosity (RV) = 36.0) (A-4): Polyamide 6I (formic acid relative viscosity RV: 14.0)

[0086] The polymerization reaction of polyamide 66 was carried out by the "hot melt polymerization method" as follows. 1500 g of an equimolar salt of isophthalic acid and hexamethylenediamine and 1.5 mol % excess adipic acid relative to the total equimolar salt components were dissolved in 1500 g of distilled water to prepare a 50 mass % equimolar homogeneous aqueous solution of raw material monomers. The mixture was concentrated by gradually releasing steam to a solution concentration of 70% by mass while stirring at a temperature of 110 to 150°C. The internal temperature was then raised to 220°C. At this time, the autoclave was pressurized to 1.8 MPa. The reaction was continued for 1 hour while maintaining the pressure at 1.8 MPa by gradually releasing steam until the internal temperature reached 245°C. The pressure was then reduced over 30 minutes, and the autoclave was then maintained at a reduced pressure of 650 torr for 10 minutes using a vacuum device, with the final internal temperature of the polymerization reaching 265°C. Thereafter, the mixture was pressurized with nitrogen and formed into strands from the lower spinneret (nozzle), cooled with water, cut, and discharged in pellet form. The pellets were dried at 100°C in a nitrogen atmosphere for 12 hours to obtain polyamide 66.

[0087] <(B) Brominated polystyrene> (B-1) Brominated polystyrene (manufactured by Shandong Sunris New Materials, trade name SR-7010 (first component: Mw = 178551, Mn = 103616, Mw / Mn = 1.72, content 92%), second component: Mw = 4443, Mn = 4078, Mw / Mn = 1.09, content 8%) (B-2) Brominated polystyrene (manufactured by GBR SVEN INDUSTRIAL, trade name BPS-7010, first component: Mw=167640, Mn=94629, Mw / Mn=1.77, content 53%, second component: Mw=3808, Mn=2844, Mw / Mn=1.34, content 47%) (B-3) Brominated polystyrene (manufactured by ALBEMARLE CORPORATION, trade name SAYTEX (registered trademark) HP-7010G (Mw=147109, Mn=55982, Mw / Mn=2.63) (B-4) Brominated polystyrene (manufactured by ALBEMARLECORPORATION, trade name SAYTEX (registered trademark) HP-3010PST (Mw=3557, Mn=2978, Mw / Mn=1.16)

[0088] <(C) Flame retardant synergist> (C) Antimony trioxide: manufactured by Campine, trade name: Antimony trioxide

[0089] <(D) Inorganic filler> (D) Glass fiber (GF) (manufactured by PFG, product name HP3540, average fiber diameter 10 μmφ, cut length 3 mm)

[0090] <(E) Compatibilizer> (E) Styrene and maleic anhydride copolymer (Polyscope, trade name SZ15170, Mw=170,000, copolymer of 85% by mass of styrene and 15% by mass of maleic anhydride)

[0091] [Method of producing the composition] <Production of Polyamide Resin Composition> [Examples 1 to 7 and Comparative Examples 1 to 7] (Production of Polyamide Resin Compositions PA-a1 to PA-a7 and PA-b1 to PA-b7) Each polyamide resin composition was produced using the following method, except that the raw materials were blended to obtain the compositions shown in Tables 1 and 2.

[0092] The polyamide resin composition was produced using a twin-screw extruder (ZSK-26MC, manufactured by Coperion, Germany) with an L / D (extruder cylinder length / extruder cylinder diameter) of 48 (number of barrels: 12) and an upstream feed port on the first barrel from the upstream side of the extruder, a downstream feed port on the fourth barrel, and a vacuum devolatilization port on the eleventh barrel. The temperature from the upstream feed port to the die was set at 280°C, the screw rotation speed was 300 rpm, and the output rate was 25 kg / h. (A) Polyamide resin, (B) Brominated polystyrene, (C) Flame retardant aid, and (E) Compatibilizer were fed through the upstream feed port, and (D) Inorganic filler (glass fiber) was fed through the downstream feed port. The mixture was melt-kneaded under reduced pressure through the vacuum devolatilization port to produce pellets of the polyamide resin composition.

[0093] Specifically, the polymer was discharged in the form of strands from the nozzle at the tip of the extruder, and after measuring the resin temperature, the polymer was cooled with water and cut to obtain pellets of the polyamide resin composition. Furthermore, molded articles were produced using the obtained polyamide resin compositions by the methods described above, and the moldability during molding, weld strength, and flame retardancy were evaluated. The evaluation results are shown in Tables 1 and 2 below.

[0094] [Table 1]

[0095] [Table 2]

[0096] As shown in Table 1, in Examples 1 to 7, which contained components (A) to (D) and satisfied the prescribed ranges, the flowability, flame retardancy, tensile properties, and weld strength were all good.

[0097] On the other hand, as shown in Table 2, in Comparative Examples 1 to 7, when the proportion of the weight-average molecular weight of (B) brominated polystyrene was outside the range or when the proportions of components (A) to (D) did not satisfy the specified ranges, no products were obtained that were good in all of the fluidity, flame retardancy, tensile properties, and weld strength. [Industrial Applicability]

[0098] The polyamide resin composition of the present embodiment can stably provide polyamide compositions and molded articles that are excellent in mechanical properties, molding flowability, flame retardancy, etc. In particular, the polyamide resin composition has excellent flame retardancy and weld strength despite its thin wall, and is therefore more suitable for use in electrical and electronic parts with a dense structure.

Claims

1. A polyamide resin composition comprising: (A) 20 to 70 mass% of polyamide; (B) 10 to 35 mass% of brominated polystyrene; (C) 1 to 15 mass% of a flame retardant aid; and (D) 10 to 60 mass% of an inorganic filler, The melting point of the polyamide (A) is 240°C or higher and 270°C or lower, The polyamide resin composition contains (B) a brominated polystyrene having a bromine content of 64 to 71 mass %, and contains a component having a weight average molecular weight of 1,000 to 5,000 and a component having a weight average molecular weight of 150,000 to 200,000.

2. 2. The polyamide resin composition according to claim 1, wherein, in 100% by mass of the (B) brominated polystyrene, a proportion of components having a weight-average molecular weight of 1,000 to 5,000 is 1% by mass or more and 50% by mass or less, and a proportion of components having a weight-average molecular weight of 150,000 to 200,000 is 50% by mass or more and 99% by mass or less.

3. 3. The polyamide resin composition according to claim 1, wherein, in 100% by mass of the brominated polystyrene (B), a proportion of components having a weight-average molecular weight of 1,000 to 5,000 is 1% by mass or more and 20% by mass or less, and a proportion of components having a weight-average molecular weight of 150,000 to 200,000 is 80% by mass or more and 99% by mass or less.

4. The polyamide resin composition according to any one of claims 1 to 3, wherein, in the (B) brominated polystyrene, a component having a weight average molecular weight of 1,000 to 5,000 has a molecular weight distribution Mw / Mn of 1.0 to 2.0, and a component having a weight average molecular weight of 150,000 to 200,000 has a molecular weight distribution Mw / Mn of 1.1 to 3.

0.

5. The polyamide resin composition according to any one of claims 1 to 4, wherein the (C) flame retardant aid is at least one selected from the group consisting of antimony oxides, tin oxides, iron oxides, and metal borates.

6. The polyamide resin composition according to any one of claims 1 to 5, wherein the (C) flame retardant synergist is diantimony trioxide.

7. The polyamide resin composition according to any one of claims 1 to 6, further comprising a compatibilizer (E), wherein the compatibilizer (E) is at least one selected from the group consisting of a copolymer of an aromatic vinyl compound and an α,β-unsaturated dicarboxylic acid anhydride, and a polymer modified with an α,β-unsaturated dicarboxylic acid anhydride.

8. The polyamide resin composition according to claim 7, wherein the compatibilizer (E) is at least one selected from the group consisting of styrene-maleic anhydride copolymers and polyphenylene ether resins modified with α,β-unsaturated dicarboxylic acid anhydrides.

9. A molded article obtained by molding the polyamide resin composition according to any one of claims 1 to 8.

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