Polyamide resin composition and molded article

Abstract

To provide a polyamide resin composition which can suppress lowering of tensile strength of the polyamide resin composition while improving flowability in injection molding.SOLUTION: A polyamide resin composition contains a polyamide resin (A) having a melting point of 280°C or higher, 0.1-30 pts.mass of a fatty acid metal salt (B) with respect to 100 pts.mass of the polyamide resin (A), and 0.1-30 pts.mass of a lubricant (C). The polyamide resin (A) includes a constitutional unit derived from 20-100 mol% of a terephthalic acid, 0-80 mol% of a constitutional unit derived from an aromatic dicarboxylic acid other than the terephthalic acid, and a constitutional unit derived from aliphatic diamine or alicyclic diamine. The lubricant (C) contains aliphatic diamide (C1) obtained by reaction of a saturated aliphatic monocarboxylic acid having 10 to 30 carbon atoms in the main chain, and aliphatic diamine having 2 to 12 carbon atoms in the main chain.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polyamide resins have traditionally been widely used as materials for various parts in clothing, industrial materials, automobiles, electrical and electronic equipment, and other industrial applications due to their excellent moldability, mechanical properties, and chemical resistance.

[0003] In recent years, the use environment of such polyamide resins has tended to become mechanically severe. For example, polyamide resins used in automobile parts, etc., are required to have high mechanical strength, as they are used to replace metals for weight reduction. Furthermore, with the increase in the number of parts due to the introduction of hybridization and driving assistance systems, there is a demand for miniaturization of parts, and polyamide resins are also required to have high moldability. In other words, polyamide resins are required to have excellent moldability and excellent mechanical strength.

[0004] As a polyamide resin with improved mechanical strength, a semi-aromatic polyamide obtained by heat-extrusion of 50 mol % of a dicarboxylic acid mixture (containing 60 to 88 mass % of terephthalic acid and 12 to 40 mass % of isophthalic acid) and 50 mol % of hexamethylenediamine has been proposed (for example, Patent Document 1).

[0005] Furthermore, in order to improve the flowability during injection molding and improve moldability, a lubricant such as a fatty acid metal salt may be added to the polyamide resin composition. For example, a flame-retardant polyamide composition containing a semi-aromatic polyamide resin and a fatty acid metal salt is known (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2008 / 155271 [Patent Document 2] International Publication No. 2008 / 126381 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the addition of a fatty acid metal salt can improve the flowability during injection molding. However, the addition of a fatty acid metal salt can sometimes result in a decrease in the tensile strength of the polyamide resin composition. In particular, resin materials used in automotive parts are desired to have high tensile strength. That is, there is a demand for a high degree of both injection flowability and tensile strength.

[0008] In view of these circumstances, an object of the present disclosure is to provide a polyamide resin composition that can improve the flowability during injection molding while suppressing a decrease in the tensile strength of the polyamide resin composition, and a polyamide molded article containing the polyamide resin composition. [Means for solving the problem]

[0009] The polyamide resin composition of the present disclosure comprises: a polyamide resin (A) having a melting point of 280°C or higher as measured by differential scanning calorimetry (DSC); 0.1 to 30 parts by mass of a fatty acid metal salt (B) relative to 100 parts by mass of the polyamide resin (A); and 0.1 to 30 parts by mass of a lubricant (C) relative to 100 parts by mass of the polyamide resin (A); the polyamide resin (A) comprises a structural unit derived from a dicarboxylic acid and a structural unit derived from a diamine; and the structural unit derived from the dicarboxylic acid is a structural unit derived from the dicarboxylic acid. The lubricant (C) comprises 20 to 100 mol % of structural units derived from terephthalic acid and 0 to 80 mol % of structural units derived from an aromatic dicarboxylic acid other than terephthalic acid, based on the total number of moles of structural units, and the diamine-derived structural units comprise at least one of structural units derived from an aliphatic diamine and structural units derived from an alicyclic diamine, and the lubricant (C) comprises an aliphatic diamide (C1) obtained by reacting a saturated aliphatic monocarboxylic acid having 10 to 30 carbon atoms in its main chain with an aliphatic diamine having 2 to 12 carbon atoms in its main chain.

[0010] The molded article of the present disclosure contains the polyamide resin composition of the present disclosure. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a polyamide resin composition that can improve the flowability during injection molding while suppressing a decrease in the tensile strength of the polyamide resin composition, and a polyamide molded article containing the polyamide resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. Polyamide resin composition The polyamide resin composition of the present disclosure contains a polyamide resin (A), a fatty acid metal salt (B), and a lubricant (C).

[0013] 1-1. Polyamide resin (A) The polyamide resin (A) contains a structural unit (a1) derived from a dicarboxylic acid and a structural unit (a2) derived from a diamine.

[0014] The dicarboxylic acid-derived structural units (a1) include structural units derived from terephthalic acid. The content of the structural units derived from terephthalic acid is preferably 20 to 100 mol%, more preferably 30 to 90 mol%, and even more preferably 60 to 80 mol%, relative to the total number of moles of the dicarboxylic acid-derived structural units (a1). When the content of the structural units derived from terephthalic acid is 30 mol% or more, the melting point (Tm) of the polyamide resin (A) can be sufficiently increased, and heat resistance and mechanical strength can easily be improved.

[0015] The dicarboxylic acid-derived structural unit (a1) may further contain a structural unit derived from a dicarboxylic acid other than terephthalic acid. Examples of dicarboxylic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, 2-methylterephthalic acid, and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as furandicarboxylic acid (e.g., 2,5-furandicarboxylic acid), 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid; and aliphatic dicarboxylic acids having 4 to 20 carbon atoms such as malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, 3,3-diethylsuccinic acid, azelaic acid, sebacic acid, and suberic acid. The structural unit derived from a dicarboxylic acid other than terephthalic acid may contain only one type, or two or more types. Among these, from the viewpoint of easily maintaining heat resistance and low water absorbency, the dicarboxylic acid constituent unit other than the terephthalic acid constituent unit is preferably a constituent unit derived from an aromatic dicarboxylic acid other than terephthalic acid, and from the viewpoint of easily adjusting the glass transition temperature Tg to a certain level or lower, it is more preferably a constituent unit derived from isophthalic acid.

[0016] The content of structural units derived from dicarboxylic acids other than terephthalic acid, preferably the content of structural units derived from aromatic dicarboxylic acids other than terephthalic acid, is preferably 0 to 80 mol%, more preferably 10 to 70 mol%, and even more preferably 20 to 40 mol%, relative to the total number of moles of structural units (a1) derived from dicarboxylic acids. When this content is greater than 0 mol%, the fluidity of the polyamide resin composition is more likely to be improved. When this content is 80 mol% or less, the heat resistance of the polyamide resin composition is less likely to be impaired.

[0017] The diamine-derived structural unit (a2) includes at least one of a structural unit derived from an aliphatic diamine and a structural unit derived from an alicyclic diamine, and preferably includes a structural unit derived from an aliphatic diamine.

[0018] The structural unit derived from an aliphatic diamine is preferably a structural unit derived from an aliphatic diamine having 4 to 15 carbon atoms, preferably 6 to 12 carbon atoms. Examples of aliphatic diamines include linear alkylenediamines such as 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane, and branched alkylenediamines such as 2-methyl-1,5-diaminopentane and 2-methyl-1,8-diaminooctane. The structural unit derived from an aliphatic diamine may be comprised of only one type, or two or more types. Among these, linear alkylenediamines are preferred, and 1,6-diaminohexane is more preferred.

[0019] The content of the structural units derived from aliphatic diamine is preferably 50 to 100 mol %, and more preferably 80 to 100 mol %, based on the total number of moles of the structural units (a2) derived from diamine. When the content of the structural units derived from aliphatic diamine is 50 mol % or more, the fluidity of the polyamide resin composition during molding is more likely to be improved.

[0020] The structural unit derived from an alicyclic diamine is preferably a structural unit derived from an alicyclic diamine having a carbon number of 4 to 20, preferably 4 to 15. Examples of the alicyclic diamine include 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(aminomethyl)cyclohexane, and the like.

[0021] The diamine-derived structural unit (a2) may further contain a structural unit derived from a diamine other than those mentioned above. Examples of the other diamines include aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-diaminonaphthalene, and 2,7-diaminonaphthalene.

[0022] Preferred examples of the polyamide resin (A) include polyamide resins in which the dicarboxylic acid-derived structural units (a1) are structural units derived from terephthalic acid and structural units derived from isophthalic acid, and the diamine-derived structural units (a2) are structural units derived from 1,6-hexanediamine.

[0023] The molecular ends of the polyamide resin (A) may be capped with a terminal capping agent.

[0024] Examples of the end-capping agent include monocarboxylic acids and monoamines. Examples of monocarboxylic acids include aliphatic monocarboxylic acids having 2 to 30 carbon atoms, such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and caprylic acid; alicyclic monocarboxylic acids, such as cyclohexanecarboxylic acid; and aromatic monocarboxylic acids, such as benzoic acid, toluic acid, naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid. Examples of monoamines include aliphatic monoamines, such as butylamine, amylamine, and hexylamine; and aromatic aliphatic monoamines, such as benzylamine and methylbenzylamine. Among these, since the molecular terminals of the polyamide resin (A) are often amino groups, it is preferable that the end-capping agent be a monocarboxylic acid.

[0025] The glass transition temperature (Tg) of the polyamide resin (A) measured by differential scanning calorimetry (DSC) is preferably 100 to 160°C, more preferably 120 to 145°C. When the Tg of the polyamide resin (A) is 100°C or higher, molecular motion at high temperatures is suppressed, and heat resistance is likely to be further improved. When the Tg of the polyamide resin (A) is 160°C or lower, the solidification rate when the molten polyamide resin composition is cooled is likely to be further increased, and the cycle time during injection molding can be further shortened.

[0026] The melting point (Tm) of the polyamide resin (A) measured by a differential scanning calorimeter (DSC) is preferably 280 to 340°C. When the melting point of the polyamide resin (A) is 280°C or higher, the mechanical strength and heat resistance of the polyamide resin composition can be easily and sufficiently increased, while when the melting point is 340°C or lower, the molding temperature does not need to be excessively high, thereby further suppressing thermal decomposition of the resin and other components during melt molding. The melting point of the polyamide resin (A) is more preferably 300 to 330°C.

[0027] The melting point (Tm) and glass transition temperature (Tg) of the polyamide resin (A) can be measured using a differential scanning calorimeter (for example, DSC220C model, manufactured by Seiko Instruments Inc.).

[0028] Specifically, approximately 5 mg of polyamide resin is sealed in a measurement aluminum pan and heated from room temperature to 350°C at 10°C / min. To completely melt the resin, it is held at 350°C for 3 minutes and then cooled to 30°C at 10°C / min. After leaving it at 30°C for 5 minutes, it is heated a second time to 350°C at 10°C / min. The temperature (°C) of the endothermic peak during this second heating is taken as the melting point (Tm) of the polyamide resin, and the inflection point corresponding to the glass transition is taken as the glass transition temperature (Tg).

[0029] The melting point and glass transition temperature of the polyamide resin (A) can be adjusted by the types of dicarboxylic acids and diamines constituting the polyamide resin (A). For example, increasing the content of structural units derived from terephthalic acid tends to increase the melting point and glass transition temperature of the polyamide resin (A).

[0030] The polyamide resin (A) preferably has an intrinsic viscosity [η] of 0.7 to 1.6 dL / g, more preferably 0.8 to 1.2 dL / g, as measured in 96.5% sulfuric acid at 25° C. When the polyamide resin (A) has an intrinsic viscosity [η] of 0.7 dL / g or more, the mechanical strength of the polyamide resin composition is easily increased, and when it is 1.6 dL / g or less, the flowability of the polyamide resin composition during molding is less likely to be impaired.

[0031] The intrinsic viscosity of polyamide resin (A) can be measured by the following method. First, approximately 0.5 g of polyamide resin (A) is dissolved in 50 ml of 96.5% concentrated sulfuric acid. Then, the flow time of the obtained solution at 25°C ± 0.05°C is measured using an Ubbelohde viscometer. The intrinsic viscosity is then calculated based on the following formula: [η]=ηSP / (C(1+0.205ηSP))

[0032] In the above formula, each algebra or variable represents the following: [η]: Intrinsic viscosity (dl / g) ηSP: Specific viscosity C: Sample concentration (g / dl)

[0033] The above ηSP is calculated by the following formula. ηSP=(t-t0) / t0 t: Number of seconds for sample solution to flow down (seconds) t0: Number of seconds the blank sulfuric acid flows (seconds)

[0034] The polyamide resin can be produced, for example, by polycondensing the above-mentioned dicarboxylic acid and diamine in a homogeneous solution. Specifically, the polyamide resin can be produced by heating the dicarboxylic acid and diamine in the presence of a catalyst to obtain a low-order condensate, as described in WO 03 / 085029, and then applying shear stress to a melt of the low-order condensate to polycondense it.

[0035] The aforementioned terminal blocking agent may be added to the reaction system from the viewpoint of adjusting the intrinsic viscosity of the polyamide resin. The intrinsic viscosity [η] (or molecular weight) of the polyamide resin can be adjusted by adjusting the amount of terminal blocking agent added.

[0036] The end-capping agent is added to the reaction system of the dicarboxylic acid and the diamine in an amount of preferably 0.07 mol or less, more preferably 0.05 mol or less, per mol of the total amount of the dicarboxylic acid.

[0037] The content of the polyamide resin (A) is preferably 25 to 90 mass %, more preferably 50 to 70 mass %, of the polyamide resin composition. When the content of the polyamide resin (A) is within the above range, the heat resistance of the polyamide resin composition can be sufficiently increased without impairing the moldability.

[0038] 1-2. Fatty acid metal salts (B) The fatty acid metal salt (B) is used for the purpose of improving the fluidity of the resin composition during injection molding.

[0039] The fatty acid constituting the fatty acid metal salt (B) is preferably a higher fatty acid. Examples of higher fatty acids include higher fatty acids having 15 to 30 carbon atoms, such as stearic acid, oleic acid, behenic acid, behenic acid, and montanic acid.

[0040] Examples of metals constituting the fatty acid metal salt (B) include calcium, magnesium, barium, lithium, aluminum, zinc, sodium, and potassium.

[0041] Among these, calcium stearate, magnesium stearate, barium stearate, calcium behenate, sodium montanate, calcium montanate, etc. are preferred, and from the viewpoint of heat resistance, sodium montanate is more preferred.

[0042] The content of the fatty acid metal salt (B) is not particularly limited, but is preferably 0.1 to 30 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the polyamide resin (A). When the content is 0.1 part by mass or more, the fluidity during molding tends to be further improved. When the content is 30 parts by mass or less, aggregation of the fatty acid metal salt (B) can be further suppressed when the molten polyamide resin composition is solidified, thereby further suppressing a decrease in tensile strength.

[0043] 1-3.Lubricant (C) The lubricant (C) can be used for the purpose of suppressing aggregation or precipitation of the fatty acid metal salt (B) when the resin composition is cooled after molding. Note that the lubricant (C) is different from the fatty acid metal salt (B). The lubricant (C) contains an aliphatic diamide (C1).

[0044] As described above, the fatty acid metal salt (B) is in a liquid state when thermally melted, which facilitates reducing the viscosity of the polyamide resin composition and improving its flowability. However, when the molten polyamide resin composition cools and solidifies, the polyamide resin (A) and the fatty acid metal salt (B) solidify at different times, which can lead to aggregation of the fatty acid metal salt (B), resulting in a decrease in the tensile strength of the polyamide resin composition. This phenomenon is particularly likely to occur when the amount of fatty acid metal salt (B) is large.

[0045] In contrast, in the present disclosure, the addition of an aliphatic diamide (C1) can suppress a decrease in the tensile strength of a polyamide resin composition. While the reason for this is unclear, the aliphatic diamide (C1) has an amide bond and therefore has high affinity with the polyamide resin (A). Furthermore, the aliphatic diamide (C1) also has an aliphatic chain and therefore has high affinity with the fatty acid metal salt (B). That is, the aliphatic diamide can function as a compatibilizer between the polyamide resin (A) and the fatty acid metal salt (B). This improves the dispersibility of the fatty acid metal salt (B), which is thought to suppress a decrease in the tensile strength of the polyamide resin composition. Furthermore, the aliphatic diamide (C1) has a larger number of aliphatic chains and amide bonds than, for example, aliphatic monoamides. Therefore, it is particularly likely to function as a compatibilizer between the polyamide resin (A) and the fatty acid metal salt (B), and to suppress bleeding of the aliphatic diamide (C1).

[0046] 1-3-1. Aliphatic diamide (C1) The aliphatic diamide (C1) is a diamide compound obtained by reacting a saturated aliphatic monocarboxylic acid with an aliphatic diamine.

[0047] The saturated aliphatic monocarboxylic acid constituting the aliphatic diamide (C1) does not have an unsaturated structure, and therefore is unlikely to react or interact with, for example, the aromatic ring of the polyamide resin (A), which is thought to promote improvement in fluidity. The saturated aliphatic monocarboxylic acid is preferably a higher saturated fatty acid. The number of carbon atoms in the main chain of the saturated aliphatic monocarboxylic acid is preferably 10 to 30, more preferably 15 to 20. Such aliphatic monocarboxylic acids have a similar structure to the fatty acids constituting the fatty acid metal salt (B), and therefore have good affinity. Examples of saturated aliphatic monocarboxylic acids include lauric acid (C12), stearic acid (C18), behenic acid (C22), and montanic acid (C28).

[0048] The number of carbon atoms in the main chain of the aliphatic diamine constituting the aliphatic diamide (C1) is preferably 2 to 12, more preferably 2 to 9. Examples of the aliphatic diamine (C1) include ethylenediamine, butanediamine, hexanediamine, etc.

[0049] Examples of the aliphatic diamide (C1) include ethylene bisstearamide, ethylene bislaurylamide, ethylene bisbehenylamide, butylene bisstearamide, etc., and ethylene bisstearamide is preferred. These may be used alone or in combination of two or more.

[0050] The content of the aliphatic diamide (C1) is preferably 10 to 100 parts by mass, and more preferably 10 to 79.5 parts by mass, per 100 parts by mass of the lubricant (C). When the content is 10 parts by mass or more, aggregation and precipitation of the fatty acid metal salt (B) can be suppressed when the polyamide resin composition is cooled after molding.

[0051] From the viewpoint of achieving both high fluidity and high tensile strength, the content ratio (C1 / B) of the aliphatic diamide (C1) and the fatty acid metal salt (B) is preferably 0.01 to 10 (mass ratio), and more preferably 0.1 to 5 (mass ratio). When C1 / B is equal to or greater than the lower limit, the decrease in tensile strength of the polyamide resin composition is more easily suppressed, and when it is equal to or less than the upper limit, the fluidity of the polyamide resin composition is more easily increased.

[0052] 1-3-2. Low-density polyethylene (C2) The lubricant (C) preferably further contains a low-density polyethylene (C2), which can be used for the purposes of further increasing the fluidity of the polyamide resin composition and facilitating dispersion of the aliphatic diamide (C1) in the vicinity of the fatty acid metal salt (B).

[0053] The low-density polyethylene (C2) is preferably an ethylene homopolymer, but may also be a copolymer of ethylene and a small amount of an α-olefin having 3 to 12 carbon atoms (such as propylene). The content of structural units derived from ethylene in the copolymer is preferably 90.0 to 99.9 mass%, more preferably 93.0 to 99.9 mass%. Meanwhile, the amount of structural units derived from an α-olefin having 3 to 12 carbon atoms is preferably 0.1 to 10.0 mass%, preferably 0.1 to 7.0 mass%.

[0054] The low-density polyethylene (C2) may be a high-pressure low-density polyethylene. High-pressure low-density polyethylene is generally obtained by radical polymerization of ethylene under high temperature and high pressure. The production method is not particularly limited, but examples thereof include a radical polymerization method in which radical polymerization is carried out under conditions of 500 to 2000 atmospheres and 150 to 300°C. Examples of the polymerization initiator include organic peroxides.

[0055] The density of the low-density polyethylene (C2) measured in accordance with ASTM D1505 is preferably 900 to 925 kg / m 3 and more preferably 910 to 925 kg / m 3 is.

[0056] The melt flow rate (MFR) of the low-density polyethylene (C2) measured in accordance with ASTM D1238 at 190°C under a load of 2.16 kg is preferably 0.1 to 50 g / 10 min, more preferably 1 to 20 g / 10 min.

[0057] The content of the low-density polyethylene (C2) is preferably 0 to 90 parts by mass, and more preferably 10 to 79.5 parts by mass, per 100 parts by mass of the lubricant (C). When the content is 10 parts by mass or more, the fluidity during molding is likely to be further improved. When the content is 79.5 parts by mass or less, decomposition gas derived from the low-density polyethylene (C2) is sufficiently suppressed, and poor appearance during molding can be suppressed.

[0058] 1-3-2. Copolymer (C3) Preferably, the lubricant (C) further contains a copolymer (C3) having structural units derived from an olefin and structural units derived from an α,β-unsaturated carboxylic acid ester. The copolymer (C3) can further suppress aggregation of the fatty acid metal salt (B) when the polyamide resin composition is cooled and solidified, thereby further suppressing a decrease in tensile strength.

[0059] The reason for this is not clear, but is thought to be as follows: Since the copolymer (C3) has structural units derived from an olefin, it has high affinity with the fatty acid metal salt (B) and the low-density polyethylene (C2). Furthermore, since the copolymer (C3) has polar moieties derived from an α,β-unsaturated carboxylic acid ester, it has high affinity with the polyamide resin (A) and the aliphatic diamide (C1). As a result, the copolymer (C3) is thought to function as a compatibilizer between the polyamide resin (A) and the fatty acid metal salt (B), and between the aliphatic diamide (C1) and the low-density polyethylene (C2). Furthermore, the copolymer (C3) is thought to easily reduce the crystallization rate and melt viscosity of the polyamide resin composition when heated and melted.

[0060] Examples of the olefin-derived structural units constituting the copolymer (C3) include structural units derived from ethylene, propylene, 1-butene, 1-hexene, 1-octene, and 1-decene, etc. Of these, structural units derived from ethylene are preferred.

[0061] Examples of structural units derived from α,β-unsaturated carboxylic acid esters constituting the copolymer (C3) include structural units derived from acrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, and methacrylic acid esters such as methyl methacrylate and ethyl methacrylate. Of these, structural units derived from C1-C10 alkyl acrylates such as methyl acrylate and n-butyl acrylate are preferred from the viewpoint of heat resistance, and structural units derived from C4-C10 alkyl acrylates are more preferred, with n-butyl acrylate being even more preferred, from the viewpoint of further improving compatibility with the low-density polyethylene (C2). The content of structural units derived from α,β-unsaturated carboxylic acid esters is preferably 5 to 70% by mass, more preferably 10 to 50% by mass, of the total of structural units derived from olefins and structural units derived from α,β-unsaturated carboxylic acid esters.

[0062] The copolymer (C3) may further contain other structural units in addition to the above structural units. Examples of the other structural units include structural units derived from α,β-unsaturated carboxylic acid glycidyl esters such as acrylic acid glycidyl ester and methacrylic acid glycidyl ester; α,β-unsaturated glycidyl ethers such as allyl glycidyl ether and 2-methylallyl glycidyl ether; aromatic vinyl compounds such as styrene, α-methylstyrene, 4-methylstyrene, 4-methoxystyrene, chlorostyrene, and 2,4-dimethylstyrene; and unsaturated vinyl esters such as vinyl acetate and vinyl propionate.

[0063] Examples of the copolymer (C3) include ethylene-n-butyl acrylate copolymer, ethylene-methyl acrylate copolymer, and ethylene-ethyl acrylate copolymer, and preferably ethylene-n-butyl acrylate copolymer, which may be used alone or in combination of two or more.

[0064] The melting point of the copolymer (C3) measured by differential scanning calorimetry (DSC) is preferably 40 to 120° C., more preferably 50 to 110° C. When the melting point of the copolymer (C3) is within this range, the flowability of the polyamide resin composition during molding can be further improved.

[0065] The melt flow rate (MFR) of the copolymer (C3), measured in accordance with ASTM D1238 at 190°C under a load of 2.16 kg, is preferably 1 to 400 g / 10 min, more preferably 10 to 100 g / 10 min.

[0066] The content of copolymer (C3) is preferably 0 to 80 parts by mass, more preferably 10 to 79.5 parts by mass, per 100 parts by mass of lubricant (C). When the content is 10 parts by mass or more, aggregation and precipitation of fatty acid metal salt (B) can be further suppressed when the polyamide resin composition is cooled after molding. When the content is 79.5 parts by mass or less, surface roughness of the molded article caused by gas generation due to thermal decomposition of copolymer (C3) can be further suppressed.

[0067] 1-3-4. Aromatic carboxylic acid compounds (C4) The lubricant (C) preferably further contains an aromatic carboxylic acid compound (C4), which can further increase the fluidity of the polyamide resin composition.

[0068] The reason for this is unclear, but it is thought that the aromatic carboxylic acid compound attacks the amide bond site of the polyamide resin (A), cleaving the bond and causing a reaction in which the aromatic carboxylic acid compound is incorporated into the bond. In other words, a reaction similar to hydrolysis occurs, which is thought to moderately lower the molecular weight of the polyamide resin (A).

[0069] The aromatic carboxylic acid compound (C4) is an aromatic carboxylic acid, its anhydride, or its alkyl (C1 to C3) ester, preferably an aromatic carboxylic acid. The aromatic carboxylic acid has, for example, 7 to 15 carbon atoms.

[0070] Examples of the aromatic carboxylic acid compound (C4) include benzoic acid, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and anhydrides and alkyl C1-3 esters thereof, with terephthalic acid and isophthalic acid being preferred, and terephthalic acid being more preferred. These may be used alone or in combination of two or more.

[0071] The content of the aromatic carboxylic acid compound (C4) is preferably 0 to 80 parts by mass, more preferably 0.5 to 20 parts by mass, per 100 parts by mass of the lubricant (C). When the content is 0.5 parts by mass or more, the fluidity during molding is likely to be further improved. When the content is 20 parts by mass or less, a decrease in mechanical strength due to excessive decomposition of the polyamide resin (A) can be sufficiently suppressed.

[0072] 1-3-5. Common matters The lubricant (C) may consist solely of an aliphatic diamide (C1), or may be a combination of the aliphatic diamide (C1) with one or more of a low-density polyethylene (C2), a copolymer (C3), and an aromatic carboxylic acid compound (C4). From the viewpoint of achieving a higher compatibility between the fluidity and tensile strength of the polyamide resin composition, the lubricant (C) preferably contains a low-density polyethylene (C2) or a copolymer (C3); more preferably contains an aliphatic diamide (C1), a low-density polyethylene (C2), and a copolymer (C3); and even more preferably contains an aliphatic diamide (C1), a low-density polyethylene (C2), a copolymer (C3), and an aromatic carboxylic acid compound (C4).

[0073] That is, the lubricant (C) preferably contains, per 100 parts by mass of the lubricant (C), 10 to 79.5 parts by mass of an aliphatic diamide (C1), 10 to 79.5 parts by mass of a low-density polyethylene (C2), 10 to 79.5 parts by mass of a copolymer (C3), and 0.5 to 20 parts by mass of an aromatic carboxylic acid compound (C4).

[0074] The content ratio (C2 / C1) of the low-density polyethylene (C2) to the aliphatic diamide (C1) is, for example, preferably 0.1 to 10, more preferably 0.2 to 1. When the content ratio is equal to or greater than the lower limit, the polyamide resin composition is more likely to have improved fluidity during injection molding while suppressing a decrease in toughness. When the content ratio is equal to or less than the upper limit, the polyamide resin composition is more likely to have improved toughness.

[0075] The content ratio (C3 / (C1+C2)) of the copolymer (C3) to the total amount of the aliphatic diamide (C1) and the low-density polyethylene (C2) is, for example, preferably 0.1 to 10, more preferably 0.2 to 5. When the content ratio is equal to or greater than the lower limit, the aliphatic diamide (C1) and the low-density polyethylene (C2) are easily compatible with each other, and the functions of each component are more easily exhibited. When the content ratio is equal to or less than the upper limit, thickening due to excessive reaction between the copolymer (C3) and the polyamide resin (A) during melting is easily suppressed.

[0076] The content of the lubricant (C) is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the polyamide resin (A). When the content is 0.1 part by mass or more, aggregation and precipitation of the fatty acid metal salt (B) can be suppressed when the polyamide resin composition is cooled after molding. When the content is 30 parts by mass or less, a decrease in the tensile strength of the polyamide resin composition due to the lubricant (C) itself becoming a foreign matter can be further suppressed.

[0077] Furthermore, from the viewpoint of achieving a high degree of both fluidity and strength, the content ratio (C / B) of the lubricant (C) to the fatty acid metal salt (B) is preferably 0.1 to 10 (mass ratio), more preferably 0.2 to 7 (mass ratio), and even more preferably 0.5 to 5 (mass ratio). When C / B is equal to or greater than the lower limit, the decrease in tensile strength of the polyamide resin composition is more easily suppressed, and when it is equal to or less than the upper limit, the fluidity of the polyamide resin composition is more easily increased.

[0078] 1-4.Other ingredients The polyamide resin composition of the present disclosure may further contain other components in addition to those described above, provided that the effects of the present disclosure are not impaired. Examples of such other components include reinforcing agents, crystal nucleating agents, flame retardants, corrosion resistance improvers, anti-drip agents, ion scavengers, elastomers (rubbers), antistatic agents, mold release agents, antioxidants (phenols, amines, sulfur compounds, phosphorus compounds, etc.), heat stabilizers (lactone compounds, vitamin E compounds, hydroquinones, copper halides, iodine compounds, etc.), light stabilizers (benzotriazoles, triazines, benzophenones, benzoates, hindered amines, oxanilides, etc.), and other polymers (polyolefins, olefin copolymers such as ethylene-propylene copolymers and ethylene-1-butene copolymers, olefin copolymers such as propylene-1-butene copolymers, polystyrene, polyamides, polycarbonates, polyacetals, polysulfones, polyphenylene oxides, fluororesins, silicone resins, and LCPs).

[0079] The reinforcing material (D) can impart high mechanical strength to the polyamide resin composition. Examples of the reinforcing material (D) include fibrous reinforcing materials such as glass fiber, wollastonite, potassium titanate whiskers, calcium carbonate whiskers, aluminum borate whiskers, magnesium sulfate whiskers, zinc oxide whiskers, milled fiber, and cut fiber, as well as granular reinforcing materials. One of these may be used alone, or two or more may be used in combination. Among these, from the viewpoint of easily increasing the mechanical strength of the polyamide resin composition, fibrous reinforcing materials such as wollastonite, glass fiber, and potassium titanate whiskers are preferred, and wollastonite or glass fiber is more preferred.

[0080] The average fiber length of the fibrous reinforcing material may be, for example, 1 μm to 20 mm, preferably 5 μm to 10 mm, from the viewpoints of moldability, mechanical strength, and heat resistance of the polyamide resin composition, and the aspect ratio of the fibrous reinforcing material may be, for example, 5 to 2000, preferably 30 to 600.

[0081] The average fiber length and average fiber diameter of the fibrous reinforcing material can be measured by the following method. 1) The resin composition is dissolved in a hexafluoroisopropanol / chloroform solution (0.1 / 0.9% by volume), and then filtered to obtain a filtrate. 2) The filtered material obtained in 1) is dispersed in water, and the fiber length (Li) and fiber diameter (di) of each of 300 randomly selected fibers are measured using an optical microscope (magnification: 50x). The number of fibers with fiber length Li is defined as qi, and the weight-average length (Lw) is calculated using the following formula, which is the average fiber length of the fibrous reinforcing material. Weight average length (Lw) = (Σqi × Li 2 ) / (Σqi×Li) Similarly, the number of fibers with a fiber diameter Di is taken as ri, and the weight average diameter (Dw) is calculated based on the following formula, and this is taken as the average fiber diameter of the fibrous reinforcing material. Weight average diameter (Dw)=(Σri×Di 2 ) / (Σri×Di)

[0082] The content of the reinforcing material (D) is not particularly limited, but is preferably 1 to 300 parts by mass, and more preferably 15 to 100 parts by mass, per 100 parts by mass of the polyamide resin (A). When the content is within the above range, the mechanical strength of the polyamide resin composition can be further increased while ensuring flowability during injection molding.

[0083] 1-5.Physical properties As described above, the polyamide resin composition of the present disclosure can maintain good tensile strength. The tensile strength of the polyamide resin composition measured in accordance with ASTM D638 varies depending on the composition, but is preferably 205 MPa or more, and more preferably 205 to 300 MPa.

[0084] Specifically, the tensile strength can be measured by the following method. First, prepare an ASTM dumbbell-shaped test piece Type I with a thickness of 3.2 mm by injection molding under the following conditions. Molding machine cylinder temperature: Melting point (Tm) of polyamide resin composition + 10°C Mold temperature: 120℃ Injection setting speed: 60mm / sec The obtained test piece is then left to stand in a nitrogen atmosphere at a temperature of 23°C for 24 hours, and then subjected to a tensile test in accordance with ASTM D638 in an atmosphere at a temperature of 23°C and a relative humidity of 50% to measure the tensile strength.

[0085] The tensile strength of the polyamide resin composition can be adjusted by adjusting the composition. For example, by including a fatty acid metal salt (B) and a lubricant (C), the decrease in tensile strength can be further reduced.

[0086] The polyamide resin composition has high melt fluidity while maintaining excellent heat resistance and high tensile strength, and is therefore particularly suitable for use in automotive parts, preferably automotive cooling parts.

[0087] 1-6. Manufacturing method The polyamide resin composition can be produced by a known resin kneading method, for example, by mixing the polyamide resin (A), the fatty acid metal salt (B), the lubricant (C), and other components as necessary using a Henschel mixer, a V-blender, a ribbon blender, or a tumbler blender, or by mixing and then melt-kneading the mixture using a single-screw extruder, a multi-screw extruder, a kneader, or a Banbury mixer, followed by granulation or pulverization.

[0088] When the lubricant (C) is composed of a plurality of components, the plurality of components may be directly melt-kneaded with other components other than the lubricant (C), or the plurality of components may be melt-kneaded in advance and pelletized, and then the pellets may be melt-kneaded with other components. In particular, from the viewpoint of facilitating dispersion of the aliphatic diamide (C1), it is preferred to melt-knead the plurality of components in advance and pelletize, and then melt-knead them with other components other than the lubricant (C).

[0089] 2. Molded body The polyamide composition can be molded into various molded articles by known molding methods such as compression molding, injection molding, and extrusion molding.

[0090] Molded articles of the polyamide composition can be used in various applications. Among these, the polyamide resin composition of the present disclosure is particularly suitable for automotive parts due to its high heat resistance and tensile strength. Examples of automotive parts include automotive cooling system parts such as radiator tank parts, coolant reservoir tanks, water inlet pipes, water outlet pipes, water pump housings, water pump impellers, water valves, and other water pump parts. [Example]

[0091] The present disclosure will be described in more detail below with reference to examples, but the scope of the present disclosure is not limited to the descriptions of the examples.

[0092] 1. Resin composition materials 1-1. Polyamide resin (A) (Preparation of Polyamide Resin 1) 2774 g (16.7 mol) of terephthalic acid, 1196 g (7.2 mol) of isophthalic acid, 2800 g (24.3 mol) of 1,6-hexanediamine, 36.6 g (0.3 mol) of benzoic acid, 5.7 g of sodium hypophosphite monohydrate, and 545 g of distilled water were placed in a 13.6 L autoclave and purged with nitrogen. Stirring was initiated at 190°C, and the internal temperature was raised to 250°C over 3 hours. At this time, the internal pressure of the autoclave was increased to 3.03 MPa. After the reaction was continued for 1 hour, a low condensation polymer was discharged into the atmosphere through a spray nozzle installed at the bottom of the autoclave and extracted. The low condensation polymer was then cooled to room temperature, pulverized in a pulverizer to a particle size of 1.5 mm or less, and dried at 110°C for 24 hours. The water content of the obtained low condensation product was 4100 ppm, and the intrinsic viscosity [η] was 0.15 dl / g.

[0093] Next, this low condensate was placed in a tray-type solid-state polymerization reactor, purged with nitrogen, and heated to 180°C over approximately 1 hour and 30 minutes. The reaction was then allowed to proceed for 1 hour and 30 minutes, and the temperature was then lowered to room temperature. The intrinsic viscosity [η] of the resulting prepolymer was 0.20 dL / g. The prepolymer was then melt-polymerized in a twin-screw extruder with a screw diameter of 30 mm and L / D = 36 at a barrel setting temperature of 330°C, a screw rotation speed of 200 rpm, and a resin feed rate of 6 kg / h to prepare polyamide resin (a-1). The melting point (Tm) of the resulting polyamide resin was 330°C, and the glass transition temperature (Tg) was 125°C.

[0094] The melting point, glass transition temperature and intrinsic viscosity [η] of the polyamide resin were measured by the following methods.

[0095] (Melting point Tm, glass transition temperature Tg) The melting point (Tm) and glass transition temperature (Tg) of the polyamide resin were measured using a differential scanning calorimeter, Model DSC220C, manufactured by Seiko Instruments Inc. Specifically, approximately 5 mg of polyamide resin was sealed in a measurement aluminum pan and heated from room temperature to 350°C at 10°C / min. To completely melt the resin, the pan was held at 350°C for 3 minutes and then cooled to 30°C at 10°C / min. After leaving the pan at 30°C for 5 minutes, the pan was heated a second time to 350°C at 10°C / min. The temperature (°C) of the endothermic peak during this second heating was taken as the melting point (Tm) of the polyamide resin, and the inflection point corresponding to the glass transition was taken as the glass transition temperature (Tg).

[0096] (Intrinsic viscosity [η]) 0.5 g of polyamide resin was dissolved in 50 ml of 96.5% sulfuric acid solution. The flow time of the resulting solution at 25°C ± 0.05°C was measured using an Ubbelohde viscometer. The intrinsic viscosity was then calculated based on the following formula: [η]=ηSP / (C(1+0.205ηSP)) [η]: Intrinsic viscosity (dl / g) ηSP: Specific viscosity C: Sample concentration (g / dl) ηSP was calculated using the following formula: ηSP=(t-t0) / t0 t: Number of seconds for sample solution to flow down (seconds) t0: Number of seconds the blank sulfuric acid flows (seconds)

[0097] 1-2. Fatty acid metal salts (B) Sodium montanate (NS-8 manufactured by Nitto Kasei Kogyo Co., Ltd., melting point 200-220°C)

[0098] 1-3.Lubricant (C) (1) Components Aliphatic diamide (C1) Ethylene bisstearamide: Wako Pure Chemical Industries, Ltd. Low-density polyethylene (C2) Low-density polyethylene 1: NUC8008 (density: 918 kg / m) manufactured by NUC Corporation 3 , Melting point: 108℃, MFR: 4.7g / 10min) ·Copolymer (C3) Ethylene-n-butyl acrylate copolymer 1: 35BA320 manufactured by Arkema Inc. (n-butyl acrylate content: 26 to 35% by mass, melting point: 65°C, MFR: 32 to 37 g / 10 min @ 2.16 kg load, 190°C) Aromatic carboxylic acid compounds (C4) Terephthalic acid: Wako Pure Chemical Industries, Ltd.

[0099] (2) Preparation of lubricant 720 g of low-density polyethylene 1, 1440 g of ethylene bisstearamide, 400 g of terephthalic acid, and 1440 g of ethylene-n-butyl acrylate copolymer were mixed in a tumbler blender and melt-kneaded in a twin-screw extruder (TEX30α manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 230°C. The mixture was then extruded into strands and cooled in a water bath. The strands were then taken up in a pelletizer and cut to obtain pellets of a lubricant.

[0100] 1-4. Reinforcement material (D) Glass fiber (Nittobo, CSX3J-451)

[0101] 2. Preparation of polyamide resin composition (Example 1, Comparative Examples 1 to 5) The components shown in Table 1 were mixed in a tumbler blender in the compounding ratios shown in the table, and melt-kneaded in a twin-screw extruder (TEX30α manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of (melting point (Tm) of polyamide resin (A) + 15°C). The mixture was then extruded into strands and cooled in a water bath. The strands were then taken up in a pelletizer and cut to obtain pellets of a polyamide resin composition.

[0102] (evaluation) (1) Liquidity Injection molding was carried out under the following conditions using a bar flow mold with a width of 10 mm and a thickness of 0.5 mm, and the flow length (mm) of the resin in the mold was measured. Injection molding machine: Tupearl TR40S3A (manufactured by Sodick Plastech Co., Ltd.) Injection pressure setting: 2000 kg / cm 2 Cylinder set temperature: 335℃

[0103] (2) Tensile strength The obtained polyamide resin composition was molded using the following injection molding machine under the following molding conditions to obtain an ASTM dumbbell-shaped test piece Type I having a thickness of 3.2 mm. (Molding conditions) Molding machine: Sumitomo Heavy Industries SG50M3 Molding machine cylinder temperature: 340℃ Mold temperature: 120℃ Injection setting speed: 60mm / sec The obtained test piece was left for 24 hours in a nitrogen atmosphere at a temperature of 23° C. Then, a tensile test was carried out in an atmosphere at a temperature of 23° C. and a relative humidity of 50% in accordance with ASTM D638 to measure the tensile strength.

[0104] The evaluation results of Examples 1 and 2 and Comparative Examples 1 to 5 are shown in Table 1.

[0105] [Table 1]

[0106] As shown in Table 1, the polyamide resin composition of Example 1 containing the fatty acid metal salt (B) and the aliphatic diamide (C1) can significantly improve fluidity while minimizing the decrease in tensile strength compared to the polyamide resin compositions of Comparative Examples 1 to 5 containing only either the fatty acid metal salt (B) or the aliphatic diamide (C1). In particular, the polyamide resin composition of Comparative Example 2, which used only the fatty acid metal salt (B), and the polyamide resin composition of Comparative Example 4, which used only the aliphatic diamide (C2), exhibited fluidity at a level higher than that predicted from these compositions. [Industrial Applicability]

[0107] The polyamide resin composition of the present disclosure can improve the flowability during injection molding while suppressing a decrease in the tensile strength of the polyamide resin composition, and therefore can be suitably used for automobile cooling system parts and the like that are required to have particularly high strength.

Claims

1. a polyamide resin (A) having a melting point of 280°C or higher as measured by differential scanning calorimetry (DSC); 0.1 to 30 parts by mass of a fatty acid metal salt (B) relative to 100 parts by mass of the polyamide resin (A); 0.1 to 30 parts by mass of a lubricant (C) relative to 100 parts by mass of the polyamide resin (A); Including, The polyamide resin (A) contains a structural unit derived from a dicarboxylic acid and a structural unit derived from a diamine, the structural units derived from the dicarboxylic acid comprise 20 to 100 mol % of structural units derived from terephthalic acid and 0 to 80 mol % of structural units derived from an aromatic dicarboxylic acid other than terephthalic acid, relative to the total number of moles of the structural units derived from the dicarboxylic acid; the diamine-derived structural unit includes at least one of an aliphatic diamine-derived structural unit and an alicyclic diamine-derived structural unit, The lubricant (C) is Relative to 100 parts by mass of the lubricant (C), 10 to 79.5 parts by mass of an aliphatic diamide (C1) obtained by reacting a saturated aliphatic monocarboxylic acid having 10 to 30 carbon atoms in its main chain with an aliphatic diamine having 2 to 12 carbon atoms in its main chain; 10 to 79.5 parts by mass of low-density polyethylene (C2), 10 to 79.5 parts by mass of a copolymer (C3) containing a structural unit derived from an olefin and a structural unit derived from an α,β-unsaturated carboxylic acid ester; 0.5 to 20 parts by mass of an aromatic carboxylic acid compound (C4) Including, Polyamide resin composition.

2. The aliphatic diamide (C1) is ethylene bisstearamide. The polyamide resin composition according to claim 1.

3. The copolymer (C3) is a copolymer containing a structural unit derived from ethylene and a structural unit derived from a C1-10 alkyl acrylate ester. The polyamide resin composition according to claim 1 or 2.

4. The copolymer (C3) includes at least one of an ethylene-n-butyl acrylate copolymer, an ethylene-methyl acrylate copolymer, and an ethylene-ethyl acrylate copolymer. The polyamide resin composition according to claim 3.

5. The aromatic carboxylic acid compound (C4) is terephthalic acid. The polyamide resin composition according to any one of claims 1 to 4.

6. the content ratio (C / B) of the lubricant (C) to the fatty acid metal salt (B) is 0.1 to 10 (mass ratio); The polyamide resin composition according to any one of claims 1 to 5.

7. Further containing 1 to 300 parts by mass of glass fiber (D) per 100 parts by mass of the polyamide resin (A), The polyamide resin composition according to any one of claims 1 to 6.

8. The glass transition temperature of the polyamide resin (A) measured by differential scanning calorimetry (DSC) is 100 to 145°C. The polyamide resin composition according to any one of claims 1 to 7.

9. The polyamide resin composition has a tensile strength of 205 MPa or more as measured in accordance with ASTM D638. The polyamide resin composition according to any one of claims 1 to 8.

10. The polyamide resin composition according to any one of claims 1 to 9, Molded body.

11. Used in automotive cooling system parts, The molded article according to claim 10.

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