Polyamide resin composition and method for producing polyamide resin composition

Abstract

A purpose of the present invention is to provide a polyamide resin composition that exhibits excellent mechanical strength retention in a high-temperature environment and during water absorption, and that is excellent in continuous moldability.　A polyamide resin composition according to the present embodiment includes: A) a polyamide resin containing at least one type of semi-aromatic polyamide; (B) an inorganic reinforcing filler; and (C) another additive. The proportion of the (A) component is 30 to 80% by weight, the proportion of the (B) component is 20 to 70% by weight, and the proportion of the (C) component is 0 to 5% by weight, relative to 100% by weight of the total of the (A) to (C) components. The polyamide resin composition further includes, in addition to the (A) to (C) components, (D) an amine compound having a molecular weight of 150 or less. The concentration of the (D) amine compound having a molecular weight of 150 or less is at least 20 ppm and less than 200 ppm relative to the total mass of the (A) to (C) components.

Description

Polyamide resin composition and method for producing polyamide resin composition

[0001] The present invention relates to a polyamide resin composition, a method for producing the same, and a molded article made of the polyamide resin composition.

[0002] Plastic parts made from reinforced thermoplastic resins are widely used in automotive, electrical, and electronic applications. Polyamide resins, which have excellent properties in terms of heat resistance, chemical resistance, mechanical strength, abrasion resistance, and moldability, are often used in these plastic parts.

[0003] Furthermore, in the field of automobiles, there is a trend to replace metal parts with plastic materials. In this application, plastic materials are sometimes used at high temperatures of around 150° C., and high mechanical strength at high temperatures is required. For example, Patent Document 1 teaches a semi-crystalline, semi-aromatic polyamide based on a monomer containing an aromatic monomer.

[0004] Furthermore, in applications requiring miniaturization and weight reduction, such as electronic plastic parts typified by electric and electronic devices, there is a demand for plastic materials that have high mechanical strength and excellent thin-wall processability. For example, Patent Document 2 teaches a partially aromatic polyamide material that has excellent moldability.

[0005] The aromatic polyamide resin materials described above have high mechanical strength in high-temperature environments, but are difficult to process because they require high processing temperatures, and the high molding temperatures cause discoloration of molded products. Furthermore, copolyamide materials using multiple monomers to improve the processability of polyamide resin materials tend to have lower heat resistance, which is a disadvantage in that they have lower high-temperature physical properties.

[0006] Furthermore, Patent Document 3 discloses an example of adding an amine compound as a heat stabilizer to a polyamide resin. However, although the method disclosed in Patent Document 3 is suitable for alicyclic polyamide resins or aliphatic polyamide resins, there has been insufficient consideration of its effect on semi-aromatic polyamide resins, which require high processing temperatures, and there has been no consideration of resin degradation due to the presence of the amine compound.

[0007] JP-T-2020-513438A JP-A-2018-178117A JP-A-5708487A

[0008] Therefore, an object of the present invention is to provide a polyamide resin composition that exhibits excellent property retention in high-temperature environments and when absorbing water. Another object of the present invention is to provide a polyamide resin composition that is a polyamide resin material that requires high molding temperatures, can suppress the occurrence of mold deposits during molding, and exhibits excellent continuous moldability. A further object of the present invention is to provide a polyamide resin composition that does not exhibit a decrease in molecular weight even in high-temperature environments and does not impair its performance as a plastic material even in high-temperature environments.

[0009] As a result of extensive research into polyamide resin compositions, the present inventors have discovered that the above-mentioned problems can be solved by including a specific semi-aromatic polyamide, an inorganic reinforcing filler, and an additive, optimizing the content ratios of these, and further including a specific amount of an amine compound, thereby completing the present invention.

[0010] That is, the present invention is as follows: [1] A polyamide resin composition comprising: (A) a polyamide resin containing at least one semi-aromatic polyamide; (B) an inorganic reinforcing filler; and (C) other additives, wherein the proportion of component (A) is 30 to 80 wt%, the proportion of component (B) is 20 to 70 wt%, and the proportion of component (C) is 0 to 5 wt%, relative to 100 wt% of the total of components (A) to (C), and further comprising (D) an amine compound having a molecular weight of 150 or less in addition to components (A) to (C), wherein the concentration of the amine compound having a molecular weight of 150 or less is 20 ppm or more and less than 200 ppm relative to the total mass of components (A) to (C). [2] The polyamide resin composition according to [1], wherein 50 mol% or more of all dicarboxylic acid units constituting the at least one semi-aromatic polyamide are terephthalic acid. [3] The polyamide resin composition according to [1], wherein 50 mol % or more of all dicarboxylic acid units constituting the at least one semi-aromatic polyamide are isophthalic acid. [4] The polyamide resin composition according to [1] or [2], wherein the at least one semi-aromatic polyamide contains repeating units obtained by condensation of an aliphatic diamine component having 4 to 6 carbon atoms with terephthalic acid. [5] The polyamide resin composition according to any one of [1] to [4], wherein the content of the semi-aromatic polyamide relative to the total weight of the polyamide resin (A) is 50 wt % or more. [6] The polyamide resin composition according to [1], [2], or [5], wherein the polyamide resin (A) is composed solely of a semi-aromatic polyamide containing repeating units obtained by condensation of an aliphatic diamine component having 4 carbon atoms with terephthalic acid. [7] The polyamide resin composition according to [1], [2], [4], or [5], wherein the (A) polyamide resin is composed solely of a semi-aromatic polyamide containing a repeating unit obtained by condensation of an aliphatic diamine component having from 4 to 6 carbon atoms with terephthalic acid. [8] The polyamide resin composition according to any one of [1] to [7], wherein the (B) inorganic reinforcing filler contains at least one fibrous inorganic reinforcing filler.[9] The polyamide resin composition according to [8], wherein the (B) inorganic reinforcing filler consists solely of a fibrous reinforcing filler.

[10] The polyamide resin composition according to [1] or [2], wherein the (C) other additive is a modified elastomer having a reactive functional group capable of reacting with the terminal group and / or main chain amide bond of the polyamide resin.

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

[10] , wherein the (D) amine compound having a molecular weight of 150 or less has 3 to 10 carbon atoms and 2 to 2 nitrogen atoms.

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

[11] , wherein the (A) polyamide resin has a skeleton derived from a first amine compound, and the (D) amine compound is a second amine compound different from the first amine compound.

[13] The polyamide resin composition according to any one of [1] to

[12] , wherein the (D) amine compound having a molecular weight of 150 or less has 3 to 5 carbon atoms and 1 nitrogen atom.

[14] A method for producing a polyamide resin composition comprising (A) a polyamide resin containing a semi-aromatic polyamide having a skeleton derived from at least one first amine compound, B) an inorganic reinforcing filler, (C) other additives, and (D) a second amine compound different from the first amine compound and having a molecular weight of 150 or less, wherein the proportion of the (A) component is 30 to 80% by weight, the proportion of the (B) component is 20 to 70% by weight, and the proportion of the (C) component is 0 to 5% by weight, relative to 100% by weight of the total of the (A) to (C) components; the concentration of the (D) amine compound is 20 ppm or more and less than 200 ppm relative to the total mass of the (A) to (C) components; the method comprises the steps of melt-kneading the (A) polyamide resin and the (B) inorganic reinforcing filler in an extruder; and performing a vacuum reduction prior to the step of melt-kneading the (A) polyamide resin and the (B) inorganic reinforcing filler; and the temperature of the resin composition at the extruder outlet is 350 to 400°C.

[0011] According to the present invention, a polyamide resin composition having high mechanical property retention in a high-temperature environment of 150°C can be provided, and during injection molding of the polyamide resin composition, the occurrence of mold deposits (MD) can be suppressed, discoloration during molding can be suppressed, and continuous moldability can be improved.

[0012] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0013] In this specification, the term "polyamide" refers to a polymer having an amide group (-NHCO-) ​​in the main chain.

[0014] [Polyamide Resin Composition] The polyamide resin composition of the present embodiment (hereinafter sometimes referred to as the "resin composition of the present embodiment" or simply the "resin composition") contains the following (A) to (C): (A) a polyamide resin containing at least one semi-aromatic polyamide; (B) at least one inorganic reinforcing filler; and (C) at least one other additive consisting of components other than (A) and (B). Here, the proportion of the (A) component is 30 to 80% by weight, the proportion of the (B) component is 20 to 70% by weight, and the proportion of the (C) component is 0 to 5% by weight, relative to 100% by weight of the total of the (A) to (C) components.

[0015] In addition to the components (A), (B), and (C), the composition further contains (D) an amine compound having a molecular weight of 150 or less, and the concentration of the (D) amine compound having a molecular weight of 150 or less contained in 1 kg of the total mass of the components (A), (B), and (C) is 20 ppm or more and less than 200 ppm.

[0016] In the polyamide resin composition of this embodiment, by adjusting the concentration of (D) the amine compound having a molecular weight of 150 or less contained in 1 kg of the resin composition comprising (A) to (D) to 20 ppm or more but less than 200 ppm, a polyamide resin composition can be realized that exhibits excellent property retention in a high-temperature environment of 150°C and after water absorption, can suppress hydrolysis of the polyamide in a high-temperature environment, and exhibits significantly little decrease in molecular weight. Furthermore, even in molding that requires high molding temperatures, the occurrence of MD (mold deposits) can be suppressed, and molded products with excellent continuous moldability can be obtained.

[0017] Each component constituting the polyamide resin composition of this embodiment will be described in detail below. <(A) Polyamide Resin> The polyamide resin of this embodiment contains (A-1) at least one semi-aromatic polyamide. ((A-1) Semi-aromatic Polyamide) The (A-1) semi-aromatic polyamide is preferably a semi-aromatic polyamide containing repeating units obtained by condensation of (I) aliphatic diamine units having a linear hydrocarbon chain (including a backbone having a side chain) and (II) dicarboxylic acid units having at least one aromatic ring in the molecule.

[0018] The (I) aliphatic diamine unit having a linear hydrocarbon chain (including a skeleton having a side chain) preferably contains an aliphatic diamine unit having from 4 to 12 carbon atoms, more preferably contains an aliphatic diamine unit having from 4 to 10 carbon atoms, and particularly preferably contains an aliphatic diamine unit having from 4 to 6 carbon atoms. When the number of carbon atoms in the aliphatic diamine unit is within the above range, the polyamide resin composition is more excellent in high-temperature property retention, etc.

[0019] The aliphatic diamines may be used alone or in combination of two or more.

[0020] The (II) dicarboxylic acid unit having at least one aromatic ring in the molecule preferably contains a dicarboxylic acid unit having from 8 to 14 carbon atoms, and particularly preferably contains a terephthalic acid and / or isophthalic acid unit. By containing the dicarboxylic acid unit, the polyamide resin composition has better high-temperature property retention and the like.

[0021] The (II) dicarboxylic acid unit having at least one aromatic ring in the molecule preferably contains terephthalic acid in an amount of 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 100 mol% based on the total number of moles.

[0022] The (II) dicarboxylic acid unit having at least one aromatic ring in the molecule may contain a dicarboxylic acid unit other than a terephthalic acid unit and / or an isophthalic acid unit, provided that the effect of the dicarboxylic acid unit is not impaired. The other dicarboxylic acid unit is preferably an aromatic dicarboxylic acid unit, and, for example, a dicarboxylic acid having a benzene ring skeleton or a naphthalene skeleton is particularly preferred.

[0023] The aromatic ring moiety of the aromatic dicarboxylic acid unit may be unsubstituted or may have a substituent. The substituent is not particularly limited, but examples thereof include an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, a halogen group such as a chloro group or a bromo group, a silyl group having 1 to 6 carbon atoms, a sulfonic acid group, and a salt thereof (e.g., a sodium salt).

[0024] The aromatic dicarboxylic acids constituting the aromatic dicarboxylic acid unit may be used alone or in combination of two or more.

[0025] Furthermore, the content of the semi-aromatic polyamide (A-1) in the polyamide resin (A) constituting the polyamide resin composition of the present embodiment is preferably 20% by mass or more, more preferably 50% by mass or more, particularly preferably 70% by mass or more, and most preferably 100% by mass, relative to the total mass (100% by mass) of the polyamide resin (A).

[0026] Furthermore, when the content of the semi-aromatic polyamide (A-1) in the polyamide resin (A) is 100% by mass, the polyamide resin (A) preferably contains a semi-aromatic polyamide (A-1) containing a repeating unit obtained by condensation of an aliphatic diamine component having from 4 to 6 carbon atoms with terephthalic acid, and more preferably is composed solely of a semi-aromatic polyamide containing a repeating unit obtained by condensation of an aliphatic diamine component having from 4 to 6 carbon atoms with terephthalic acid. Furthermore, when the content of the semi-aromatic polyamide (A-1) in the polyamide resin (A) is 100% by mass, it is particularly preferable that the polyamide resin (A) is composed solely of a semi-aromatic polyamide (A-1) containing a repeating unit obtained by condensation of an aliphatic diamine component having from 4 to 6 carbon atoms with terephthalic acid.

[0027] The melting point Tm of the semi-aromatic polyamide (A-1) is preferably 280°C or higher and 360°C or lower, more preferably 290°C or higher and 350°C or lower, and particularly preferably 300°C or higher and 340°C or lower. When the melting point Tm of the semi-aromatic polyamide (A-1) is equal to or higher than the lower limit, the heat resistance and compression resistance of molded articles obtained from the polyamide composition tend to be more excellent. On the other hand, when the melting point Tm of the semi-aromatic polyamide (A-1) is equal to or lower than the upper limit, thermal decomposition of the polyamide composition during melt processing such as extrusion and molding is more suppressed, and physical properties in high-temperature environments tend to be good.

[0028] Furthermore, from the viewpoint of mechanical properties, particularly water absorption rigidity and hot rigidity, the crystallization enthalpy ΔH of the semi-aromatic polyamide (A-1) is preferably 30 J / g or more and 70 J / g or less, more preferably 35 J / g or more and 65 J / g or less, and particularly preferably 40 J / g or more and 60 J / g or more. On the other hand, the crystallization enthalpy ΔH of the semi-aromatic polyamide (A-1) is not particularly limited, and the higher the better. Examples of devices for measuring the melting point Tm and crystallization enthalpy ΔH of the semi-aromatic polyamide (A-1) include Diamond-DSC manufactured by Perkin-Elmer.

[0029] Furthermore, the tan δ peak temperature of the semi-aromatic polyamide (A-1) is preferably 80°C or higher, more preferably 90°C or higher and 160°C or lower, even more preferably 100°C or higher and 155°C or lower, particularly preferably 110°C or higher and 150°C or lower, and most preferably 120°C or higher and 150°C or lower. When the tan δ peak temperature of the crystalline semi-aromatic polyamide (A-1) is equal to or higher than the above lower limit, the heat resistance and property retention rate upon water absorption of molded articles obtained from the polyamide composition tend to be more excellent. The tan δ peak temperature of the crystalline semi-aromatic polyamide (A-1) can be measured using a viscoelasticity measurement analyzer (Rheology: DVE-V4) or the like.

[0030] (A-2) Aliphatic Polyamide) The polyamide resin (A) may contain an aliphatic polyamide (A-2) in addition to the at least one semi-aromatic polyamide (A-1). The aliphatic polyamide (A-2) contained in the polyamide resin (A) is an aliphatic polyamide containing (III) aliphatic diamine units having a linear hydrocarbon chain (including a backbone having a side chain) and (IV) aliphatic dicarboxylic acid units.

[0031] The (III) aliphatic diamine unit having a linear hydrocarbon chain (including a skeleton having a side chain) preferably contains an aliphatic diamine unit having 4 to 12 carbon atoms, more preferably contains an aliphatic diamine unit having 4 to 10 carbon atoms, and particularly preferably contains an aliphatic diamine unit having 4 to 6 carbon atoms.

[0032] Examples of the aliphatic dicarboxylic acid constituting the (IV) aliphatic dicarboxylic acid unit include linear or branched saturated aliphatic dicarboxylic acids having from 3 to 20 carbon atoms, and linear or branched unsaturated aliphatic dicarboxylic acids having from 4 to 20 carbon atoms. Among these, linear saturated aliphatic dicarboxylic acids having from 4 to 10 carbon atoms are particularly preferred from the viewpoint of the heat resistance of the polyamide composition.

[0033] The (A-2) aliphatic polyamide may contain (V) at least one selected from the group consisting of lactam units and aminocarboxylic acid units, instead of (III) aliphatic diamine units having a linear hydrocarbon chain (including a backbone having a side chain) and (IV) aliphatic dicarboxylic acid units.

[0034] The aliphatic polyamide (A-2) contained in the polyamide composition of this embodiment is preferably a polyamide containing dicarboxylic acid units and diamine units, more preferably a polyamide containing aliphatic dicarboxylic acid units and aliphatic diamine units, more preferably a polyamide containing aliphatic dicarboxylic acid units and aliphatic diamine units, more preferably a polyamide containing aliphatic dicarboxylic acid units having 4 to 10 carbon atoms and aliphatic diamine units having 4 to 10 carbon atoms, even more preferably a polyamide containing saturated aliphatic dicarboxylic acid units and saturated aliphatic diamine units having 4 to 10 carbon atoms, particularly preferably polyamide 46 (PA46), polyamide 66 (PA66), or polyamide 610 (PA610), with PA66 being the most preferred. PA66 is considered to be a suitable material for automotive parts and industrial machinery applications due to its excellent mechanical properties, heat resistance, moldability, and toughness.

[0035] Furthermore, the content of the aliphatic polyamide (A-2) in the polyamide resin (A) constituting the polyamide resin composition of the present embodiment is preferably 0% by mass or more and 80% by mass or less, more preferably 0% by mass or more and 50% by mass or less, and particularly preferably 0% by mass or more and 30% by mass or less, relative to the total mass (100% by mass) of the polyamide resin (A).

[0036] Furthermore, the terminals of the polyamides ((A-1) at least one type of semi-aromatic polyamide and (A-2) aliphatic polyamide) contained in the polyamide resin composition of the present embodiment may be capped with a known terminal capping agent.

[0037] <(B) At Least One Kind of Inorganic Reinforcing Filler> The polyamide resin composition of the present embodiment contains (B) at least one kind of inorganic reinforcing filler in addition to the (A) polyamide resin.

[0038] The inorganic reinforcing filler (B) is not particularly limited, but is preferably, for example, a fibrous inorganic reinforcing material, and particularly preferably glass fiber or carbon fiber. By including a fibrous inorganic reinforcing material as the inorganic reinforcing filler (B), a polyamide resin composition having excellent mechanical strength can be obtained, and can be used for automotive and industrial applications. These fibrous reinforcing fillers may be used alone or in combination of two or more.

[0039] The polyamide resin composition of the present embodiment may contain an inorganic reinforcing filler other than the fibrous inorganic reinforcing filler. Examples of the inorganic reinforcing filler other than the fibrous inorganic reinforcing filler include, but are not limited to, talc, mica, wollastonite, kaolin, hydrotalcite, glass flakes, calcium carbonate, zinc oxide, silica, alumina, titanium oxide, carbon nanotubes, graphite, aluminum, and iron.

[0040] In the polyamide resin composition of this embodiment, the content of the inorganic reinforcing filler (B) in the polyamide resin composition is preferably 20% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 65% by mass or less, and particularly preferably 30% by mass or more and 60% by mass or less, relative to the total mass of the polyamide resin composition. By having the content of the inorganic reinforcing filler (B) in the above range, a polyamide resin composition that satisfies both mechanical strength and toughness can be obtained.

[0041] [(C) Other Additives] In addition to the components (A) and (B) described above, the polyamide resin composition of the present embodiment may also contain (C) other additives that are conventionally used in polyamide resin compositions, within a range that does not impair the effects of the polyamide resin composition of the present embodiment.

[0042] Examples of the (C) other additives include impact modifiers, moldability improvers (hereinafter also referred to as "lubricants"), deterioration inhibitors, heat stabilizers, nucleating agents, and dyes and pigments for coloring.

[0043] The (C) other additives may also contain a modified elastomer for the purpose of improving impact resistance. As the modified elastomer, those modified with dicarboxylic acids such as maleic acid or itaconic acid, or their anhydrides are preferred in terms of having better mechanical properties.

[0044] The modified elastomer has, as its constituent components, at least one component derived from an olefin compound, and the main chain of the modified elastomer is preferably an unsaturated hydrocarbon structure and / or a saturated hydrocarbon structure obtained by reducing the unsaturated hydrocarbon, and can be expressed as CmHn (m and n are natural numbers).

[0045] Furthermore, the proportion of the olefin compound-derived components contained in the modified elastomer is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.

[0046] Furthermore, the additive may be, for example, a carboxylic acid having multiple carboxy groups, such as citric acid. By adding a carboxylic acid having multiple carboxy groups, it is possible to neutralize the amine compounds generated during processing and release them from the system. Furthermore, since the carboxylic acid has multiple carboxy groups in its molecule, it not only contributes to the construction of a crosslinked structure by reaction with the terminal amino groups of the polyamide resin, but also acts as a capping agent for the terminal amino groups of the polyamide resin.

[0047] Furthermore, when the polyamide resin composition of the present embodiment contains the other additives (C), the content of the other additives (C) in the polyamide composition of the present embodiment varies depending on the type of the other additives, the use of the polyamide composition, etc., and is not particularly limited as long as it is within a range that does not impair the effects of the polyamide composition of the present embodiment. For example, the content is preferably 0% by mass or more and 5% by mass or less, more preferably 0% by mass or more and 3% by mass or less, and particularly preferably 0% by mass or more and 1% by mass or less, relative to the total mass of the polyamide resin composition.

[0048] <(D) Amine Compound with a Molecular Weight of 150 or Less> The polyamide resin composition of this embodiment further comprises an amine compound with a molecular weight of 150 or less in addition to the components (A) to (C) described above. The concentration of the (D) amine compound with a molecular weight of 150 or less contained per 1 kg of the polyamide resin composition of this embodiment must be 20 ppm or more but less than 200 ppm, preferably 20 ppm or more but less than 150 ppm, and more preferably 20 ppm or more but less than 120 ppm. When the concentration of the (D) amine compound with a molecular weight of 150 or less per 1 kg of the polyamide resin composition is equal to or greater than the above-mentioned lower limit, the amine compound captures radicals that can cause polyamide decomposition, making molecular weight reduction less likely. On the other hand, when the amine compound concentration is less than 200 ppm, nucleophilic attack by the amine compound on amide bonds is suppressed, thereby suppressing deterioration of physical properties under high temperature conditions and upon water absorption. Furthermore, because molecular weight reduction under high temperature conditions is suppressed, performance as a plastic material is not impaired even under high temperature conditions. Furthermore, by adding (D) an amine compound having a molecular weight of 150 or less to the polyamide resin composition of the present embodiment, the generation of MD (mold deposit) during injection molding is suppressed, and therefore a polyamide resin composition with excellent continuous moldability can be provided.

[0049] The method for adjusting the concentration of the (D) amine compound having a molecular weight of 150 or less to the above-mentioned range is not particularly limited, but the following methods (1) or (2) are preferred. (1) When producing the polyamide resin composition of this embodiment using an extruder, the content of the (D) component is adjusted by providing two or more, preferably three or more, vacuum devolatilization ports in the barrel. (2) When producing the polyamide resin composition of this embodiment using an extruder, the content of the (D) component is adjusted by adding an amine compound or an acid compound. The acid compound is not particularly limited, but is preferably a carboxylic acid, carbonic acid, or phosphoric acid. Preferred carboxylic acids include monocarboxylic acids such as formic acid and acetic acid, dicarboxylic acids such as succinic acid and adipic acid, and tricarboxylic acids such as citric acid.

[0050] The concentration of (D) an amine compound having a molecular weight of 150 or less contained in 1 kg of the polyamide resin composition of this embodiment can be measured by the following methods (i) to (iv). (i) A powder sample is obtained by freeze-pulverizing the polyamide resin composition of this embodiment using liquid nitrogen. (ii) Approximately 20 mg of the powder sample obtained by freeze-pulverization is weighed, and dimethyl terephthalate is added as an internal standard. The sample is then heated at 350°C for 5 minutes to generate gas. (iii) The generated gas is collected using a cold trap, and the trapped components are desorbed by heating. The gas components are then introduced into a GC / MS. (iv) The concentration of (D) an amine compound having a molecular weight of 150 or less is measured as a semi-quantitative value relative to the internal standard from the peak area of ​​the spectrum obtained by GC / MS. The sample heating and gas desorption can be performed using, for example, a TDU2 manufactured by Gestel. The semi-quantitative measurement of the compounds can be performed using, for example, a GC-7890 MSD-5977B manufactured by Agilent. The column may be DB-HeavyWAX or the like.

[0051] <Measurement conditions> TDU: Thermal desorption temperature: 350°C Thermal desorption time: 5 minutes Heating conditions: 40°C - 350°C, 720°C / sec Split ratio: Splitless CIS: Trap temperature: -40°C Heating conditions: -40°C - 300°C, 12°C / sec GC: Column: DB-HeavyWAX (30m x 0.25mm x 0.25µm) Carrier gas: He (1.2mL / min) Oven temperature: 40°C - 280°C, 10°C / sec

[0052] The amine compound (D) is preferably a second amine compound different from the first amine compound. By using a diamine different from the diamine constituting the polyamide, nucleophilic attack by the amine compound on the amide bond is further suppressed, thereby suppressing deterioration of physical properties under high temperature conditions and when absorbing water.

[0053] Furthermore, the (D) amine compound having a molecular weight of 150 or less preferably has 3 to 10 carbon atoms and 2 or less nitrogen atoms. It is more preferable that the number of carbon atoms is 3 to 5 and the number of nitrogen atoms is 1 or less. Nucleophilic attack on the amide bond is further suppressed, thereby suppressing deterioration of physical properties in high-temperature environments and upon water absorption. Examples of such (D) amine compounds having a molecular weight of 150 or less include, but are not limited to, allylamine, isobutylamine, isopropylamine, ethylamine, ethylenediamine, octanediamine, diisopropylamine, diethylamine, diethylenetriamine, cyclopropylamine, cyclohexanediamine, cyclohexylamine, dibutylamine, dimethylamine, triethylamine, trimethylamine, butylamine, 1-pentanamine, methylamine, aziridines, aromatic amines such as aniline, and heterocyclic aromatic amines.

[0054] [Method for Producing Polyamide Resin Composition] The method for producing the polyamide composition of the present embodiment is not particularly limited, as long as it is a method of mixing the components (A) a polyamide resin containing at least one kind of semi-aromatic polyamide, (B) an inorganic reinforcing filler, and, if necessary, the above-mentioned (C) other additives.

[0055] Examples of methods for mixing the above components include the following methods (1) and (2): (1) A method in which the above components (A) to (C) are mixed using a Henschel mixer or the like, and then fed to a melt kneader and kneaded. (2) A method in which the above components (A) to (C) are mixed using a single-screw or twin-screw extruder or the like, and then fed to a melt kneader and kneaded.

[0056] The components constituting the polyamide composition may be fed into the melt kneader by feeding all of the components into the same feed port at once, or by feeding each component through a different feed port. The melt kneading temperature is preferably about 10 to 30°C higher than the melting point of the polyamide resin (A) containing at least one semi-aromatic polyamide. The shear rate in the kneader is 100 sec. －１ The average residence time of the resin composition during kneading is preferably about 0.5 minutes or more and about 3 minutes or less. Any known device may be used as the melt-kneading device, and for example, a single-screw or twin-screw extruder, a Banbury mixer, a melt-kneader (e.g., a mixing roll), etc. are preferably used. The blending amounts of each component when producing the polyamide composition of this embodiment are the same as the contents of each component in the polyamide composition described above.

[0057] The method for producing a polyamide composition of the present embodiment is a method for producing a polyamide resin composition comprising: (A) a polyamide resin containing a semi-aromatic polyamide having a skeleton derived from at least one first amine compound; (B) an inorganic reinforcing filler; (C) other additives; and (D) a second amine compound having a molecular weight of 150 or less, which is different from the first amine compound, The resin composition may be one in which the proportion of the (A) component is 30 to 80% by weight, the proportion of the (B) component is 20 to 70% by weight, and the proportion of the (C) component is 0 to 5% by weight, relative to 100% by weight of the total of the (A) to (C) components; the concentration of the (D) amine compound is 20 ppm or more and less than 200 ppm with respect to the total mass of the (A) to (C) components; the resin composition may include a step of melt-kneading the (A) polyamide resin and the (B) inorganic reinforcing filler in an extruder; and a step of performing vacuum decompression prior to the step of melt-kneading the (A) polyamide resin and the (B) inorganic reinforcing filler; and the temperature of the resin composition at the outlet of the extruder is 350 to 400°C.

[0058] [Molded Article] The molded article of this embodiment contains the polyamide resin composition of this embodiment described above. The method for obtaining the molded article of this embodiment is not particularly limited, and any known molding method can be used. Examples of known 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).

[0059] 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.

[0060] (Constituent Components) Hereinafter, each constituent component of the polyamide resin composition used in the present examples and comparative examples will be described. (A-1) Semi-aromatic polyamide A-1-1: Polyamide 4T / 6T copolyamide (melting point 328°C) A-1-2: Polyamide 6T / 6I copolyamide (melting point 320°C) A-1-3: Polyamide 9T (melting point 305°C) A-1-4: Polyamide 6I

[0061] Among the semi-aromatic polyamides (A-1), polyamide 4T / 6T copolyamide (A-1-1) was prepared as follows: 1500 g of 4T / 6T salt (38 mol% / 62 mol%) was added to a 50-liter rotary dryer, which was then evacuated to 50 mbar and filled with nitrogen. After repeating the above procedure five times, the mixture was heated to 220°C over 5 hours, followed by 255°C over 15 hours, while the reaction water was removed from the system. Under a nitrogen purge, a mixture of 65 g of 1,6-hexamethylenediamine, 30 g of 1,4-butanediamine, and 100 g of water was added over 7 hours. The mixture was further reacted at 235°C under a nitrogen atmosphere for 29 hours, and the material was cooled to room temperature to obtain a white powder ((A-1-1) polyamide 4T / 6T copolyamide). The polyamide 4T / 6T copolyamide (A-1-1) prepared under the above conditions was dried under a nitrogen atmosphere to adjust the moisture content to 0.2% by mass or less, and then used as a raw material for the polyamide resin compositions in the examples and comparative examples described below.

[0062] (A-2) Aliphatic polyamides A-2-1: Polyamide 66 (melting point 265°C) A-2-2: Polyamide 46 (melting point 295°C) A-2-3: Polyamide 610 (melting point 220°C)

[0063] (B) Inorganic reinforcing filler B-1: Carbon fiber (HT C413 manufactured by Teijin Limited) B-2: Glass fiber (ECS03T-275H manufactured by Nippon Electronic Glass Co., Ltd.) B-3: Glass flakes (MEG160FY-M03 manufactured by Nippon Sheet Glass Co., Ltd.)

[0064] (Method for Producing Polyamide Resin Composition) In the examples and comparative examples described below, polyamide resin compositions were produced under the following conditions. First, a twin-screw extruder with 13 barrels, having an upstream feed port on the first barrel from the upstream side of the extruder and downstream feed ports on the sixth and ninth barrels, was used. (A) Polyamide resin and, if necessary, (C) other additives were fed through the upstream feed port. Furthermore, while the resin fed through the upstream feed port was fully molten, (B) inorganic reinforcing filler was fed through the downstream feed port. The (B) inorganic reinforcing filler could be fed through either the feed port on the sixth or ninth barrel, and the temperature could be adjusted appropriately depending on the filler used. Furthermore, when producing the polyamide resin composition of this embodiment using the above method, the mixture was melt-kneaded under reduced pressure through vacuum devolatilizer ports provided on the fifth, eighth, and twelfth barrels, and the barrel temperature was set to a temperature 10°C to 30°C higher than the melting point of (A) polyamide resin. The melt-kneaded product extruded from the die head was cooled in the form of strands and pelletized to obtain pellets of the polyamide composition. The types of components used in the production of the polyamide resin composition are as follows, and the amounts of each component are shown in Table 1.

[0065] [Example 1] According to the above-mentioned production method, (A-1) a semi-aromatic polyamide and (B) an inorganic reinforcing filler were supplied to an extruder, and melt-kneaded under reduced pressure through vacuum devolatilization ports provided at three locations to obtain a polyamide resin composition in which the concentration of (D) an amine compound having a molecular weight of 150 or less contained per 1 kg of the polyamide resin composition was 20 ppm or more but less than 200 ppm.

[0066] [Examples 2 to 12] According to the above-mentioned production method, (A-1) semi-aromatic polyamide and, if necessary, (A-2) aliphatic polyamide and (B) inorganic reinforcing filler were supplied to an extruder, and melt-kneaded under reduced pressure through vacuum devolatilization ports provided at three locations to obtain polyamide resin compositions in which the concentration of (D) an amine compound having a molecular weight of 150 or less contained per kg of the polyamide resin composition was 20 ppm or more but less than 200 ppm.

[0067] Example 13 According to the above production method, (A-1) semi-aromatic polyamide, (B) inorganic reinforcing filler, and 3-pyrroline (manufactured by Tokyo Chemical Industry Co., Ltd.) as an amine compound were fed into an extruder, and melt-kneaded under reduced pressure through vacuum degassing ports installed in three locations. Equivalent amounts of (B) inorganic reinforcing filler were added through the sixth and ninth barrels. A polyamide resin composition was obtained in which the concentration of (D) an amine compound with a molecular weight of 150 or less contained per 1 kg of the polyamide composition was 20 ppm or more but less than 200 ppm.

[0068] [Comparative Example 1] According to the above-mentioned production method, (A-1) semi-aromatic polyamide and (B) inorganic reinforcing filler were supplied to an extruder, and melt-kneaded under reduced pressure through a vacuum devolatilization port provided at only one location, to obtain a polyamide resin composition in which the concentration of (D) an amine compound having a molecular weight of 150 or less contained per kg of the polyamide resin composition was 200 ppm or more.

[0069] [Comparative Examples 2 to 4] According to the above-mentioned production method, (A-1) semi-aromatic polyamide, (A-2) aliphatic polyamide, and (B) inorganic reinforcing filler were supplied to an extruder, and melt-kneaded under reduced pressure through a vacuum devolatilization port provided at only one location, to obtain a polyamide resin composition in which the concentration of (D) an amine compound having a molecular weight of 150 or less contained per kg of the polyamide resin composition was 200 ppm or more.

[0070] [Comparative Example 5] According to the above-mentioned production method, (A-1) semi-aromatic polyamide, (B) inorganic reinforcing filler, and 5% by mass of citric acid relative to the total mass of the polyamide resin composition were supplied to an extruder, and the mixture was melt-kneaded under reduced pressure through vacuum devolatilizer ports provided at three locations, thereby obtaining a polyamide resin composition in which the concentration of (D) an amine compound having a molecular weight of 150 or less contained per 1 kg of the polyamide resin composition was less than 20 ppm.

[0071] Comparative Example 6 According to the above-mentioned production method, (A-1) semi-aromatic polyamide and (B) inorganic reinforcing filler were fed into an extruder, and melt-kneaded under reduced pressure through three vacuum degassing ports. Equivalent amounts of (B) inorganic reinforcing filler were added through the sixth and ninth barrels. A polyamide resin composition was obtained in which the concentration of (D) an amine compound with a molecular weight of 150 or less per 1 kg of the polyamide composition was less than 20 ppm.

[0072] <Evaluation of Mechanical Properties and Moldability> Molded articles were produced by injection molding from the polyamide resin compositions of the samples obtained in the Examples and Comparative Examples, and the following evaluations were carried out.

[0073] (1) Evaluation of Continuous Moldability When injection molding was performed using the polyamide resin composition of each sample, the presence or absence of deposits (MD) on the venting vent provided in the mold was evaluated. The degree of deposits on the venting vent after 100 continuous molding shots was evaluated according to the following criteria. (Evaluation criteria) A: Excellent (no deposits on the venting vent of the mold after 100 continuous molding shots) B: Good (slight deposits on the venting vent of the mold after 100 continuous molding shots) C: Poor (clogged vent of the mold due to deposits during continuous molding after 100 shots)

[0074] (2) Water-Absorbed Bending Property Retention Rate For each sample polyamide resin composition, a molded article was produced by injection molding, and a multipurpose test piece (Type A) was cut from the molded article to prepare a bending test piece (80 mm x 10 mm x 4 mm strip). The bending strength and bending modulus were measured in accordance with ASTM D790 using a bending tester (Toyo Seiki Co., Ltd.: UTM25) at 23°C and a crosshead speed of 5 mm / min. The bending strength and bending modulus retention rates (%) were calculated using the following formulas: Water-Absorbed Bending Strength Retention Rate (%) = (Bending Strength of Water-Absorbed Test Piece / Bending Strength of Absolutely Dry Test Piece) x 100 Water-Absorbed Bending Modulus Retention Rate (%) = (Bending Modulus of Water-Absorbed Test Piece / Bending Modulus of Absolutely Dry Test Piece) x 100 Note that the water absorption of the test pieces was measured using a method in accordance with JIS K-7143.

[0075] (3) 150°C flexural modulus retention rate For each sample polyamide resin composition, a molded product was produced by injection molding, and a multipurpose test piece (Type A) was cut from the molded product to prepare a flexural test piece (80 mm x 10 mm x 4 mm strip). The flexural strength and flexural modulus were measured for the test piece in accordance with ASTM D790 using a flexural tester (Toyo Seiki Co., Ltd.: UTM25) at 23°C and 150°C and a crosshead speed of 5 mm / min. The flexural modulus retention rate (%) was calculated using the following formula: 150°C flexural modulus retention rate (%) = (flexural modulus at 150°C / flexural modulus at 23°C) x 100

[0076] (4) Molecular Weight Retention Rate at 230°C Pellets of the polyamide resin composition of each sample were dried for 18 hours in a vacuum dryer with the temperature inside the dryer set at 230°C, and the weight average molecular weight Mw of the pellets was then measured by GPC (gel permeation chromatography). The molecular weight retention rate at 230°C (%) was calculated using the following formula: Molecular weight retention rate at 230°C (%) = (weight average molecular weight Mw after treatment at 230°C / weight average molecular weight Mw before heat treatment) x 100

[0077]

[0078]

[0039] From the results in Table 1, it can be seen that the polyamide resin composition of the present invention not only had no deposits on the venting vent of the injection molding die and was excellent in continuous moldability, but also had excellent bending property retention in a high-temperature environment and after water absorption, and molecular weight retention after high-temperature treatment. When the content of the amine compound (D) having a molecular weight of 150 or less in the polyamide resin composition of this embodiment is within the range of the present invention, a polyamide resin composition having particularly excellent properties as described above can be obtained.

[0079] On the other hand, even if the contents of the components (A) to (C) are the same as those in the example compositions of this embodiment, when the content of the amine compound (D) having a molecular weight of 150 or less is outside the range of the present invention, it is understood that the above performance is impaired.

Claims

1. A polyamide resin composition comprising: (A) a polyamide resin containing at least one semi-aromatic polyamide; (B) an inorganic reinforcing filler; and (C) other additives, wherein the proportion of component (A) is 30-80% by weight, the proportion of component (B) is 20-70% by weight, and the proportion of component (C) is 0-5% by weight, relative to 100% by weight of the total of components (A) to (C); and further comprising, in addition to components (A) to (C), (D) an amine compound having a molecular weight of 150 or less, wherein the concentration of the amine compound (D) having a molecular weight of 150 or less is 20 ppm or more and less than 200 ppm relative to the total mass of components (A) to (C).

2. The polyamide resin composition according to claim 1, wherein terephthalic acid accounts for 50 mol % or more of the total dicarboxylic acid units constituting said at least one semi-aromatic polyamide.

3. The polyamide resin composition according to claim 1, wherein 50 mol % or more of all dicarboxylic acid units constituting said at least one semi-aromatic polyamide are isophthalic acid.

4. The polyamide resin composition according to claim 1 or 2, wherein the at least one semi-aromatic polyamide contains a repeating unit obtained by condensation of an aliphatic diamine component having 4 to 6 carbon atoms with terephthalic acid.

5. A polyamide resin composition according to any one of claims 1 to 3, characterized in that the content of said semi-aromatic polyamide relative to the total weight of said polyamide resin (A) is 50% by weight or more.

6. A polyamide resin composition according to any one of claims 1 to 3, characterized in that the polyamide resin (A) is composed solely of a semi-aromatic polyamide containing repeating units obtained by condensation of an aliphatic diamine component having four carbon atoms with terephthalic acid.

7. A polyamide resin composition according to any one of claims 1 to 3, characterized in that the polyamide resin (A) is composed solely of a semi-aromatic polyamide containing repeating units obtained by condensation of an aliphatic diamine component having 4 to 6 carbon atoms with terephthalic acid.

8. A polyamide resin composition according to any one of claims 1 to 3, wherein the inorganic reinforcing filler (B) contains at least one type of fibrous inorganic reinforcing filler.

9. The polyamide resin composition according to claim 8, wherein the inorganic reinforcing filler (B) consists solely of a fibrous reinforcing filler.

10. A polyamide resin composition according to any one of claims 1 to 3, characterized in that the (C) other additive is a modified elastomer having a reactive functional group capable of reacting with the terminal group and / or main chain amide bond of the polyamide resin.

11. The polyamide resin composition according to any one of claims 1 to 3, wherein the (D) amine compound having a molecular weight of 150 or less has 3 to 10 carbon atoms and 2 or less nitrogen atoms.

12. A polyamide resin composition according to any one of claims 1 to 3, characterized in that the polyamide resin (A) has a skeleton derived from a first amine compound, and the amine compound (D) is a second amine compound different from the first amine compound.

13. A polyamide resin composition according to any one of claims 1 to 3, characterized in that (D) the amine compound having a molecular weight of 150 or less has 3 to 5 carbon atoms and 1 nitrogen atom.

14. A method for producing a polyamide resin composition comprising (A) a polyamide resin containing a semi-aromatic polyamide having a skeleton derived from at least one first amine compound, (B) an inorganic reinforcing filler, (C) other additives, and (D) a second amine compound different from the first amine compound and having a molecular weight of 150 or less, wherein, relative to 100% by weight of the total of components (A) to (C), the proportion of component (A) is 30 to 80% by weight, the proportion of component (B) is 20 to 70% by weight, and the proportion of component (C) is 0 to 5% by weight, and the concentration of the amine compound (D) is 20 ppm or more and less than 200 ppm relative to the total mass of components (A) to (C), and the method comprises the steps of melt-kneading the (A) polyamide resin and the (B) inorganic reinforcing filler in an extruder and applying a vacuum pressure reduction prior to the step of melt-kneading the (A) polyamide resin and the (B) inorganic reinforcing filler, and wherein the temperature of the resin composition at the extruder outlet is 350 to 400°C.

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