JP7812411B2 - Polyamide composition, its manufacturing method, and molded article - Google Patents

Description

The present invention relates to a polyamide composition, a method for producing the same, and a molded article.

Due to their outstanding property profile, aliphatic polyamide-based compositions are used to produce molded articles in a wide variety of applications. Polyamide compositions with flame-retardant properties are particularly required for components in the electrical and electronics industry to ensure adequate fire protection.

Polyamides are often flame-retarded by adding halogen compounds. However, recent regulations on hazardous substances, such as RoHS (Restriction of Hazardous Substances) and PoHS (Prohibition on Certain Hazardous Substances in Consumer Products), have put in place various restrictions to prevent the use of products containing halogen compounds in electrical and electronic components. For this reason, several non-halogen flame retardants for polyamides have been developed.

Examples of non-halogen flame retardants include phosphorus compounds. Patent Document 1 discloses the use of calcium and aluminum salts of phosphinic acid or diphosphinic acid as flame retardants for polyamides. Test specimens with a thickness of 1.2 mm made from polyamide compositions containing these non-halogen flame retardants and reinforced with 30% by weight of glass fiber, based on the total weight of the composition, achieve a flammability classification of V-0 according to UL94.

Patent Document 2 discloses that to achieve UL94 flammability classification V-0, a glass fiber reinforced polyamide composition primarily composed of polyamide 6 requires aluminum phosphinate in an amount far exceeding 20% by mass relative to the total mass of the composition, and a glass fiber reinforced polyamide composition primarily composed of polyamide 66 requires aluminum phosphinate in an amount exceeding 30% by mass. Thus, to achieve flammability classification V-0 using a phosphinic acid flame retardant, a large amount must be added, which poses a problem as it adversely affects mechanical properties.

Patent Document 3 discloses a polyamide composition based on a mixture of an aliphatic polyamide containing a phosphinate salt as a flame retardant and a semi-aromatic polyamide. It has been reported that the addition of the semi-aromatic polyamide reduces the amount of flame retardant used and improves tensile elongation.

Patent Document 4 also discloses a polyamide composition based on a mixture of polyamides, including aromatic polyamides, and polyphenylene sulfide, using a phosphinate as a flame retardant. It has been reported that adding polyphenylene sulfide, which has excellent flame retardancy, to polyamides, including aromatic polyamides, can reduce the amount of flame retardant used and reduce the amount of outgassing resulting from the flame retardant.

Patent No. 3947261 Patent No. 4698789 Patent No. 4614959 JP 2009-270107 A Japanese Patent Application Laid-Open No. 2005-179362 EP 699708 Japanese Patent Application Publication No. 08-073720

However, although the polyamide composition described in Patent Document 3 has improved tensile elongation at break by reducing the amount of flame retardant used, there is still room for improvement in long-term heat resistance and the like required for automobiles and various electrical parts.
Furthermore, although the polyamide composition described in Patent Document 4 reduces the amount of flame retardant used and reduces outgassing by adding polyphenylene sulfide, there is concern that if the ratio of aliphatic polyamide to aromatic polyamide is increased, it will become difficult to maintain a flammability classification of V-0 according to UL94.
As described above, in the prior art, there is no known polyamide composition that uses a non-halogen flame retardant and yet has both flame retardancy and long-term heat resistance.

The present invention was made in consideration of the above circumstances and provides a polyamide composition containing a non-halogen flame retardant that can produce molded articles with excellent flame retardancy and long-term heat resistance, a method for producing the same, and a molded article made from the polyamide composition. It also provides a method for adding a styrene copolymer as a flame retardant aid.

That is, the present invention includes the following aspects.
A polyamide composition according to a first aspect of the present invention is a polyamide composition containing (A) a polyamide, (B) a phosphorus-based flame retardant, and (C) a styrene copolymer, wherein the content of the (C) styrene copolymer is 0.1 mass % or more and 7.0 mass % or less with respect to the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer.

The (A) polyamide may contain (A1) an aliphatic polyamide and (A2) a semi-aromatic polyamide containing diamine units and dicarboxylic acid units.

The (A2) semi-aromatic polyamide may contain 50 mol% or more of isophthalic acid units among all dicarboxylic acid units constituting the (A2) semi-aromatic polyamide.

The (A2) semi-aromatic polyamide may contain 75 mol% or more of isophthalic acid units out of all dicarboxylic acid units constituting the (A2) semi-aromatic polyamide.

The (A2) semi-aromatic polyamide may contain 100 mol% isophthalic acid units out of all dicarboxylic acid units constituting the (A2) semi-aromatic polyamide.

The (C) styrene copolymer may contain acrylonitrile units and styrene units.

The styrene copolymer (C) may contain acrylonitrile units and styrene units, and the content of the acrylonitrile units may be 30% by mass or more based on the total mass of the constituent units of the styrene copolymer (C).

The (B) phosphorus-based flame retardant may contain at least one phosphinate selected from the group consisting of a phosphinate represented by the following general formula (1), a diphosphinate represented by the following general formula (2), and a condensate thereof.

(In general formula (1), R ¹¹ and R ¹² each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ^{M n11+} represents an n11-valent metal ion. M represents an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n11 is 2 or 3, and a plurality of R ¹¹ and R ¹² may be the same or different.
In general formula (2), ^R21 and ^R22 are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ^Y21 is an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms. ^M'm21+ is an m21-valent metal ion. M' is an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n21 is an integer of 1 to 3. When n21 is 2 or 3, multiple ^R21 , ^R22 , and ^Y21 may be the same or different. m21 is 2 or 3. x is 1 or 2. When x is 2, multiple M' may be the same or different. n21, x, and m21 are integers that satisfy the relationship 2 × n21 = m21 × x.

The content of the (B) phosphorus-based flame retardant may be 0.1% by mass or more and 30% by mass or less relative to the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer.

The polyamide composition may have a tanδ peak temperature of 90°C or higher.

The weight average molecular weight of the polyamide composition may be 10,000 or more and 50,000 or less.

The polyamide composition according to the first aspect may further contain at least one type of filler (D).

The molded article according to the second aspect of the present invention is obtained by molding the polyamide composition according to the first aspect.

The method for producing a polyamide composition according to the third aspect of the present invention is a method for producing the polyamide composition according to the first aspect, in which raw material components containing the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer are melt-kneaded.

A method according to a fourth aspect of the present invention is a method in which a styrene copolymer is added as a flame retardant aid to a resin composition containing a polyamide and a phosphorus-based flame retardant.

The polyamide composition and its manufacturing method described above contain a non-halogen flame retardant, and molded articles with excellent flame retardancy and long-term heat resistance can be obtained.

The following describes in detail the form for carrying out the present invention (hereinafter simply referred to as "the present embodiment"). 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 with appropriate modifications within the scope of its gist.

In this specification, "polyamide" refers to a polymer having amide (-NHCO-) groups in the main chain.

<Polyamide composition>
The polyamide composition of the present embodiment contains the following components (A) to (C).
(A) polyamide;
(B) a phosphorus-based flame retardant;
(C) Styrene copolymer

In the polyamide composition of the present embodiment, the content of component (C) relative to the total mass of components (A) to (C) is 0.1 mass % or more and 7 mass % or less.
The polyamide composition of the present embodiment has the above-described configuration, and thus contains a non-halogen flame retardant, and a molded article having excellent flame retardancy and long-term heat resistance can be obtained.

<Characteristics of Polyamide Composition>
The molecular weight and tan δ peak temperature of the polyamide composition of the present embodiment can be as follows, and specifically, can be measured by the method described in the examples below.

[Weight average molecular weight (Mw) of polyamide composition]
The weight average molecular weight (Mw) can be used as an index of the molecular weight of a polyamide composition.
The weight average molecular weight (Mw) of the polyamide composition is preferably 10,000 or more and 50,000 or less, more preferably 17,000 or more and 45,000 or less, even more preferably 20,000 or more and 45,000 or less, even more preferably 25,000 or more and 45,000 or less, particularly preferably 30,000 or more and 42,000 or less, and most preferably 34,000 or more and 38,000 or less.
When the weight-average molecular weight (Mw) of the polyamide composition is within the above range, the polyamide composition obtained has excellent mechanical properties, particularly excellent rigidity in water absorption, rigidity at heat, flowability, etc. Furthermore, molded articles obtained from the polyamide composition containing a component typified by the filler (D) have excellent tensile strength and long-term heat resistance.

As a method for controlling the Mw of the polyamide composition within the above range, for example, the polyamide (A) and the styrene copolymer (C) may be used whose Mw falls within the ranges described below.
The weight average molecular weight (Mw) can be measured using GPC (gel permeation chromatography) as described in the examples below.

[Tan δ Peak Temperature of Polyamide Composition]
The lower limit of the tan δ peak temperature of the polyamide composition is preferably 90°C, more preferably 105°C, and even more preferably 110°C.
On the other hand, the upper limit of the tan δ peak temperature of the polyamide composition is preferably 150°C, more preferably 140°C, and even more preferably 130°C.
That is, the tan δ peak temperature of the polyamide composition is preferably 90°C or higher and 150°C or lower, more preferably 105°C or higher and 140°C or lower, and even more preferably 110°C or higher and 130°C or lower.
When the tan δ peak temperature of the polyamide composition is equal to or higher than the lower limit, the polyamide composition tends to have better water absorption rigidity and hot rigidity. On the other hand, when the tan δ peak temperature of the polyamide composition is equal to or lower than the upper limit, the molded article obtained from the polyamide composition containing a component typified by (D) filler tends to have better tensile strength and long-term heat resistance.

One example of a method for controlling the tan δ peak temperature of a polyamide composition within the above range is to contain (A1) an aliphatic polyamide and (A2) a semi-aromatic polyamide containing diamine units and dicarboxylic acid units, as described below, and control the contents thereof within the ranges described below.

The following describes in detail each of the components of the polyamide composition of this embodiment.

<(A) Polyamide>
From the viewpoint of improving flame retardancy, weld strength, and laser welding strength, the polyamide (A) contained in the polyamide composition of the present embodiment preferably contains an aliphatic polyamide (A1) and a semi-aromatic polyamide (A2) containing diamine units and dicarboxylic acid units.

[(A1) Aliphatic polyamide]
The structural units of the aliphatic polyamide (A1) preferably satisfy at least one of the following conditions (1) and (2):
(1) The polymer contains (A1-a) an aliphatic dicarboxylic acid unit and (A1-b) an aliphatic diamine unit.
(2) (A1-c) Contains at least one unit selected from the group consisting of lactam units and aminocarboxylic acid units.

The polyamide composition of this embodiment can contain, as the aliphatic polyamide (A1), one or more polyamides that satisfy at least one of the above conditions (1) and (2). In particular, it is particularly preferable that the structural units of the aliphatic polyamide (A1) contained in the polyamide composition of this embodiment satisfy the above condition (1).

((A1-a) Aliphatic Dicarboxylic Acid Unit)
Examples of the aliphatic dicarboxylic acid constituting the aliphatic dicarboxylic acid unit (A1-a) include linear or branched saturated aliphatic dicarboxylic acids having from 3 to 20 carbon atoms.
Examples of linear saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms include, but are not limited to, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, and diglycolic acid.
Examples of branched saturated aliphatic dicarboxylic acids having from 3 to 20 carbon atoms include, but are not limited to, dimethylmalonic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylglutaric acid, 2,2-diethylsuccinic acid, 2,3-diethylglutaric acid, 2,2-dimethylglutaric acid, 2-methyladipic acid, and trimethyladipic acid.
The aliphatic dicarboxylic acids constituting the (A1-a) aliphatic dicarboxylic acid unit may be used singly or in combination of two or more.
Among these, the aliphatic dicarboxylic acid constituting the aliphatic dicarboxylic acid unit (A1-a) is preferably a linear saturated aliphatic dicarboxylic acid having 6 or more carbon atoms, since the polyamide composition tends to have better heat resistance, fluidity, toughness, low water absorbency, rigidity, and the like.

Specific examples of preferred linear saturated aliphatic dicarboxylic acids having 6 or more carbon atoms include adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid.
Among these, the linear saturated aliphatic dicarboxylic acid having 6 or more carbon atoms is preferably adipic acid, sebacic acid, or dodecanedioic acid from the viewpoint of the heat resistance of the polyamide composition.

Furthermore, the (A1) aliphatic polyamide may further contain units derived from a trivalent or higher polycarboxylic acid, as necessary, to the extent that the effects of the polyamide composition of this embodiment are not impaired. Examples of trivalent or higher polycarboxylic acids include trimellitic acid, trimesic acid, and pyromellitic acid. These trivalent or higher polycarboxylic acids may be used alone or in combination of two or more.

((A1-b) Aliphatic Diamine Unit)
Examples of the aliphatic diamine constituting the aliphatic diamine unit (A1-b) include linear saturated aliphatic diamines having 2 to 20 carbon atoms, and branched saturated aliphatic diamines having 3 to 20 carbon atoms.
Examples of linear saturated aliphatic diamines having 2 to 20 carbon atoms include, but are not limited to, ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, and tridecamethylenediamine.
Examples of branched saturated aliphatic diamines having 3 to 20 carbon atoms include, but are not limited to, 2-methylpentamethylenediamine (also referred to as 2-methyl-1,5-diaminopentane), 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 2-methyl-1,8-octanediamine (also referred to as 2-methyloctamethylenediamine), and 2,4-dimethyloctamethylenediamine.
The aliphatic diamines constituting the (A1-b) aliphatic diamine unit may be used singly or in combination of two or more.
In particular, the carbon number of the aliphatic diamine constituting the (A1-b) aliphatic diamine unit is preferably 6 or more and 12 or less, and more preferably 6 or more and 10 or less. When the carbon number of the aliphatic diamine constituting the (A1-b) aliphatic diamine unit is equal to or more than the above-mentioned lower limit, the heat resistance of the obtained molded article is more excellent. On the other hand, when the carbon number is equal to or less than the above-mentioned upper limit, the crystallinity and releasability of the obtained molded article are more excellent.

Specific examples of preferred linear or branched saturated aliphatic diamines having 6 to 12 carbon atoms include hexamethylenediamine, 2-methylpentamethylenediamine, and 2-methyl-1,8-octanediamine.
Among these, hexamethylenediamine or 2-methylpentamethylenediamine is preferred as the linear or branched saturated aliphatic diamine having from 6 to 12 carbon atoms. By containing such an aliphatic diamine unit (A1-b), the heat resistance, rigidity, etc. of a molded article obtained from the polyamide composition are improved.

Furthermore, the (A1) aliphatic polyamide may further contain units derived from a trivalent or higher polyvalent aliphatic amine, as necessary, to the extent that the effects of the polyamide composition of this embodiment are not impaired. Examples of trivalent or higher polyvalent aliphatic amines include bishexamethylenetriamine.

((A1-c) At least one structural unit selected from the group consisting of lactam units and aminocarboxylic acid units)
The aliphatic polyamide (A1) may contain at least one structural unit (A1-c) selected from the group consisting of lactam units and aminocarboxylic acid units. By containing such units, the resulting polyamide tends to have excellent toughness.
The terms "lactam unit" and "aminocarboxylic acid unit" used herein refer to a lactam and an aminocarboxylic acid that have been polymerized (condensed).

Examples of lactams constituting the lactam unit include, but are not limited to, butyrolactam, pivalolactam, ε-caprolactam, caprylolactam, enantholactam, undecanolactam, laurolactam (dodecanolactam), and the like.
Among these, the lactam constituting the lactam unit is preferably ε-caprolactam or laurolactam, and more preferably ε-caprolactam. By including such a lactam, molded articles obtained from the polyamide composition tend to have better toughness.

The aminocarboxylic acid constituting the aminocarboxylic acid unit is not limited to the following, but examples thereof include ω-aminocarboxylic acids, which are compounds formed by ring-opening of lactams, and α,ω-amino acids.
The aminocarboxylic acid constituting the aminocarboxylic acid unit is preferably a linear or branched saturated aliphatic carboxylic acid having from 4 to 14 carbon atoms and substituted with an amino group at the ω position. Examples of such aminocarboxylic acids include, but are not limited to, 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Other examples of aminocarboxylic acids include para-aminomethylbenzoic acid.

The lactam and aminocarboxylic acid constituting at least one structural unit selected from the group consisting of (A1-c) lactam units and aminocarboxylic acid units may each be used alone or in combination of two or more types.

Among these, as the aliphatic polyamide (A1), from the viewpoints of mechanical properties, heat resistance, moldability, and toughness, polyamides containing dicarboxylic acid units and diamine units are preferred, and polyamide 66 (PA66) is more preferred. Due to its excellent mechanical properties, heat resistance, moldability, and toughness, PA66 is considered a suitable material for automotive parts.

The content of (A1) aliphatic polyamide can be, for example, 50% by mass or more and 100% by mass or less, for example, 55% by mass or more and 100% by mass or less, or for example, 57% by mass or more and 100% by mass or less, relative to the total mass of polyamide in the polyamide composition.

((A1) Weight Average Molecular Weight Mw(A1) of Aliphatic Polyamide)
The weight average molecular weight Mw(A1) of the aliphatic polyamide (A1) can be used as an index of the molecular weight. The weight average molecular weight Mw(A1) of the aliphatic polyamide is preferably 10,000 or more and 50,000 or less, more preferably 17,000 or more and 45,000 or less, even more preferably 20,000 or more and 45,000 or less, even more preferably 25,000 or more and 45,000 or less, particularly preferably 30,000 or more and 45,000 or less, and most preferably 35,000 or more and 40,000 or less.
When the weight-average molecular weight Mw(A1) is within the above range, a polyamide composition having excellent mechanical properties, particularly rigidity when absorbing water, rigidity when hot, and fluidity, as well as excellent tensile strength, flexural modulus when absorbing water, long-term heat resistance, and tracking resistance when formed into a molded article can be obtained.
The weight average molecular weight Mw(A1) can be measured using GPC as described in the examples below.

[(A2) Semi-aromatic polyamide]
(A2) The semi-aromatic polyamide is a polyamide containing diamine units and dicarboxylic acid units.
The semi-aromatic polyamide (A2) preferably contains 20 mol % to 80 mol % of aromatic structural units, more preferably 30 mol % to 70 mol % of aromatic structural units, and even more preferably 40 mol % to 60 mol % of aromatic structural units, based on all structural units of the semi-aromatic polyamide (A2). As used herein, "aromatic structural units" refers to aromatic diamine units and aromatic dicarboxylic acid units.

Furthermore, the (A2) semi-aromatic polyamide is preferably a polyamide containing (A2-a) dicarboxylic acid units containing 50 mol% or more of isophthalic acid units relative to the total dicarboxylic acid units of the (A2) semi-aromatic polyamide, and (A2-b) diamine units containing diamine units having from 4 to 10 carbon atoms.
In this case, the total content of isophthalic acid units and diamine units having 4 to 10 carbon atoms in the semi-aromatic polyamide (A2) is preferably 50 mol% or more, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, and particularly preferably 100 mol% based on the total structural units of the semi-aromatic polyamide (A2).

The proportion of the specified monomer units constituting (A2) the semi-aromatic polyamide can be measured by nuclear magnetic resonance spectroscopy (NMR) or the like.

((A2-a) Dicarboxylic acid unit)
The dicarboxylic acid unit (A2-a) is not particularly limited, and examples thereof include an aromatic dicarboxylic acid unit, an aliphatic dicarboxylic acid unit, and an alicyclic dicarboxylic acid unit.
Among these, the (A2-a) dicarboxylic acid units preferably contain isophthalic acid units in an amount of 50 mol% or more, more preferably 65 mol% or more and 100 mol% or less, even more preferably 75 mol% or more and 100 mol% or less, particularly preferably 80 mol% or more and 100 mol% or less, and most preferably 100 mol% or less, relative to the total number of moles of the (A2-a) dicarboxylic acid units.
When the proportion of isophthalic acid units in the (A2-a) dicarboxylic acid units is at least the above lower limit, a polyamide composition tends to be obtained that simultaneously satisfies mechanical properties, particularly rigidity when absorbing water, rigidity when hot, fluidity, etc. Furthermore, molded articles obtained from the polyamide composition tend to be superior in tensile strength, flexural modulus when absorbing water, long-term heat resistance, and tracking resistance.

(1) Aromatic dicarboxylic acid unit Examples of aromatic dicarboxylic acids constituting aromatic dicarboxylic acid units other than isophthalic acid units include, but are not limited to, dicarboxylic acids having an aromatic group such as a phenyl group or a naphthyl group. The aromatic group of the aromatic dicarboxylic acid may be unsubstituted or may have a substituent.

The substituent is not particularly limited, but examples thereof include alkyl groups having from 1 to 4 carbon atoms, aryl groups having from 6 to 10 carbon atoms, arylalkyl groups having from 7 to 10 carbon atoms, alkylaryl groups having from 7 to 10 carbon atoms, halogen groups, silyl groups having from 1 to 6 carbon atoms, sulfonic acid groups and salts thereof (such as sodium salts).
Examples of alkyl groups having 1 to 4 carbon atoms include, but are not limited to, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group.
Examples of the aryl group having 6 to 10 carbon atoms include, but are not limited to, a phenyl group and a naphthyl group.
Examples of the arylalkyl group having 7 to 10 carbon atoms include, but are not limited to, a benzyl group.
Examples of alkylaryl groups having 7 to 10 carbon atoms include, but are not limited to, tolyl and xylyl groups.
Examples of the halogen group include, but are not limited to, a fluoro group, a chloro group, a bromo group, and an iodo group.
Examples of the silyl group having 1 to 6 carbon atoms include, but are not limited to, a trimethylsilyl group and a tert-butyldimethylsilyl group.
Among these, the aromatic dicarboxylic acid constituting the aromatic dicarboxylic acid unit other than the isophthalic acid unit is preferably an unsubstituted or predetermined substituent-substituted aromatic dicarboxylic acid having 8 to 20 carbon atoms.

Specific examples of unsubstituted or predetermined substituent-substituted aromatic dicarboxylic acids having from 8 to 20 carbon atoms include, but are not limited to, terephthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, and 5-sodium sulfoisophthalic acid.
The aromatic dicarboxylic acid constituting the aromatic dicarboxylic acid unit may be used alone or in combination of two or more.

(2) Aliphatic Dicarboxylic Acid Unit Examples of the aliphatic dicarboxylic acid constituting the aliphatic dicarboxylic acid unit include linear or branched saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms.

Examples of linear saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms include, but are not limited to, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, and diglycolic acid.
Examples of branched saturated aliphatic dicarboxylic acids having from 3 to 20 carbon atoms include, but are not limited to, dimethylmalonic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylglutaric acid, 2,2-diethylsuccinic acid, 2,3-diethylglutaric acid, 2,2-dimethylglutaric acid, 2-methyladipic acid, and trimethyladipic acid.

(3) Alicyclic Dicarboxylic Acid Unit The alicyclic dicarboxylic acid constituting the alicyclic dicarboxylic acid unit (hereinafter sometimes referred to as "alicyclic dicarboxylic acid unit") is, but is not limited to, for example, an alicyclic dicarboxylic acid having an alicyclic structure with 3 to 10 carbon atoms. Among these, the alicyclic dicarboxylic acid is preferably an alicyclic dicarboxylic acid having an alicyclic structure with 5 to 10 carbon atoms.

Examples of such alicyclic dicarboxylic acids include, but are not limited to, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, etc. Among these, 1,4-cyclohexanedicarboxylic acid is preferred as the alicyclic dicarboxylic acid.
The alicyclic dicarboxylic acid constituting the alicyclic dicarboxylic acid unit may be used alone or in combination of two or more.

The alicyclic group of the alicyclic dicarboxylic acid may be unsubstituted or may have a substituent. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include the same groups as those exemplified above in the "aromatic dicarboxylic acid unit."

The dicarboxylic acid units other than the isophthalic acid units preferably contain aromatic dicarboxylic acid units, and more preferably contain aromatic dicarboxylic acids having 6 or more carbon atoms.
Use of such dicarboxylic acids tends to provide a polyamide composition that simultaneously satisfies mechanical properties, particularly rigidity when absorbing water, rigidity when hot, fluidity, etc. Furthermore, molded articles obtained from the polyamide composition tend to have better tensile strength, flexural modulus when absorbing water, long-term heat resistance, and tracking resistance.

In the (A2) semi-aromatic polyamide, the dicarboxylic acid constituting the (A2-a) dicarboxylic acid unit is not limited to the compounds described above as the dicarboxylic acid, and may be a compound equivalent to the above dicarboxylic acid.
The term "compound equivalent to a dicarboxylic acid" used herein refers to a compound that can have a dicarboxylic acid structure similar to the dicarboxylic acid structure derived from the dicarboxylic acid. Examples of such compounds include, but are not limited to, anhydrides of dicarboxylic acids and halides of dicarboxylic acids.

Furthermore, the semi-aromatic polyamide (A2) may further contain units derived from a trivalent or higher polycarboxylic acid, as needed, within a range that does not impair the effects of the polyamide composition of the present embodiment.
Examples of trivalent or higher polycarboxylic acids include trimellitic acid, trimesic acid, pyromellitic acid, etc. These trivalent or higher polycarboxylic acids may be used alone or in combination of two or more.

((A2-b) Diamine Unit)
The diamine units (A2-b) constituting the semi-aromatic polyamide (A2) are not particularly limited and include, for example, aromatic diamine units, aliphatic diamine units, alicyclic diamine units, etc. Among these, the diamine units (A2-b) constituting the semi-aromatic polyamide (A2) preferably contain diamine units having from 4 to 10 carbon atoms, and more preferably contain diamine units having from 6 to 10 carbon atoms.

(1) Aliphatic Diamine Unit Examples of the aliphatic diamine constituting the aliphatic diamine unit include linear saturated aliphatic diamines having 4 to 20 carbon atoms.
Examples of linear saturated aliphatic diamines having 4 to 20 carbon atoms include, but are not limited to, ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, and tridecamethylenediamine.

(2) Alicyclic Diamine Unit Examples of alicyclic diamines (hereinafter also referred to as "alicyclic diamines") constituting the alicyclic diamine unit include, but are not limited to, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, 1,3-cyclopentanediamine, and the like.

(3) Aromatic Diamine Unit The aromatic diamine constituting the aromatic diamine unit is not limited to the following, as long as it is a diamine containing an aromatic group. Specific examples of aromatic diamines include metaxylylenediamine.

The diamines constituting the diamine units may be used singly or in combination of two or more.
Among these, the diamine unit (A2-b) is preferably an aliphatic diamine unit, more preferably a linear saturated aliphatic diamine unit having from 4 to 10 carbon atoms, still more preferably a linear saturated aliphatic diamine unit having from 6 to 10 carbon atoms, and particularly preferably a hexamethylenediamine unit.
Use of such diamines tends to provide a polyamide composition that simultaneously satisfies mechanical properties, particularly rigidity upon absorption of water, rigidity at heat, fluidity, etc. Furthermore, molded articles obtained from the polyamide composition tend to have better tensile strength, flexural modulus upon absorption of water, long-term heat resistance, and tracking resistance.

(A2) As the semi-aromatic polyamide, polyamide 6I (polyhexamethylene isophthalamide), polyamide 9I, or polyamide 10I is preferred, with polyamide 6I being more preferred. Polyamide 6I is considered a suitable material for automotive parts due to its excellent heat resistance, moldability, and flame retardancy.

The content of the (A2) semi-aromatic polyamide can be 0% by mass or more and 50.0% by mass or less, preferably 10.0% by mass or more and 45.0% by mass or less, more preferably 15.0% by mass or more and 43.0% by mass or less, and even more preferably 20.0% by mass or more and 41.0% by mass or less, relative to the total mass of polyamide in the polyamide composition.
By setting the content of the (A2) semi-aromatic polyamide within the above range, the mechanical properties of molded articles obtained from the polyamide composition are improved. Furthermore, by adding a component typified by the (D) filler, the tensile strength, flexural modulus after absorbing water, long-term heat resistance, and tracking resistance of molded articles obtained from the polyamide composition tend to be improved.

((A2) Weight average molecular weight Mw(A2) of semi-aromatic polyamide)
The weight average molecular weight Mw(A2) can be used as an index of the molecular weight of the semi-aromatic polyamide (A2). The weight average molecular weight Mw(A2) of the semi-aromatic polyamide is preferably 10,000 to 50,000, more preferably 15,000 to 45,000, even more preferably 15,000 to 40,000, even more preferably 17,000 to 30,000, particularly preferably 17,000 to 25,000, and most preferably 18,000 to 22,000.
When the weight-average molecular weight Mw(A2) is within the above range, a polyamide composition having excellent mechanical properties, particularly rigidity when absorbing water, rigidity when hot, and fluidity, as well as excellent tensile strength, flexural modulus when absorbing water, long-term heat resistance, and tracking resistance when formed into a molded article can be obtained.
The weight average molecular weight Mw(A2) can be measured using GPC as described in the examples below.

[End-capping agent]
The terminals of the polyamide (A) contained in the polyamide composition of the present embodiment may be capped with a known terminal capping agent.
Such an end-capping agent can also be added as a molecular weight regulator when producing a polyamide from the above dicarboxylic acid and the above diamine, or from at least one member selected from the group consisting of the above lactam and the above aminocarboxylic acid.

Examples of the end-capping agent include, but are not limited to, monocarboxylic acids, monoamines, acid anhydrides (such as phthalic anhydride), monoisocyanates, monoesters, monoalcohols, etc. One type of end-capping agent may be used alone, or two or more types may be used in combination.
Among these, monocarboxylic acids or monoamines are preferred as the end-capping agent. By blocking the ends of the polyamide with an end-capping agent, molded articles obtained from the polyamide composition tend to have better thermal stability.

The monocarboxylic acid usable as the end-capping agent may be any monocarboxylic acid that is reactive with amino groups that may be present at the terminals of the polyamide, and examples of the monocarboxylic acid include, but are not limited to, aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids.
Examples of the aliphatic monocarboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid.
Examples of alicyclic monocarboxylic acids include cyclohexanecarboxylic acid.
Examples of aromatic monocarboxylic acids include benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid.
These monocarboxylic acids may be used alone or in combination of two or more.
In particular, it is preferred that the terminals of the semi-aromatic polyamide (A2) be blocked with acetic acid from the viewpoints of fluidity and mechanical strength.

The monoamine usable as the end-capping agent may be any monoamine that is reactive with carboxyl groups that may be present at the terminals of the polyamide, and includes, but is not limited to, aliphatic monoamines, alicyclic monoamines, and aromatic monoamines.
Examples of the aliphatic monoamine include methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine.
Examples of alicyclic monoamines include cyclohexylamine and dicyclohexylamine.
Examples of aromatic monoamines include aniline, toluidine, diphenylamine, and naphthylamine.
These monoamines may be used alone or in combination of two or more.

Polyamide compositions containing polyamides end-capped with an end-capping agent tend to have superior heat resistance, flowability, toughness, low water absorption, and rigidity.

<(A) Method for producing polyamide>
When producing the polyamide (A) (aliphatic polyamide (A1) and semi-aromatic polyamide (A2)) contained in the polyamide composition of this embodiment, the amount of dicarboxylic acid added and the amount of diamine added are preferably approximately the same molar amount. Taking into account the amount of diamine that escapes to the outside of the reaction system during the polymerization reaction, the molar amount of all diamines relative to the molar amount of all dicarboxylic acids is preferably 0.9 to 1.2, more preferably 0.95 to 1.1, and even more preferably 0.98 to 1.05.

The method for producing polyamide includes, but is not limited to, the following polymerization step (1) or (2).
(1) A step of polymerizing a combination of a dicarboxylic acid constituting a dicarboxylic acid unit and a diamine constituting a diamine unit to obtain a polymer.
(2) A step of polymerizing one or more members selected from the group consisting of lactams constituting the lactam units and aminocarboxylic acids constituting the aminocarboxylic acid units to obtain a polymer.

The method for producing polyamide preferably further includes, after the polymerization step, an increasing step of increasing the degree of polymerization of the polyamide. If necessary, after the polymerization step and the increasing step, a capping step of capping the ends of the resulting polymer with an end-capping agent may be included.

Specific methods for producing polyamide include various methods such as those exemplified in the following 1) to 4).
1) A method in which an aqueous solution or suspension of one or more selected from the group consisting of a dicarboxylic acid-diamine salt, a mixture of a dicarboxylic acid and a diamine, a lactam, and an aminocarboxylic acid is heated and polymerized while maintaining the molten state (hereinafter, this may be referred to as a "thermal melt polymerization method").
2) A method in which the degree of polymerization of polyamide obtained by the hot melt polymerization method is increased while maintaining the solid state at a temperature below the melting point (hereinafter, sometimes referred to as "hot melt polymerization/solid phase polymerization method").
3) A method in which one or more members selected from the group consisting of dicarboxylic acid-diamine salts, mixtures of dicarboxylic acids and diamines, lactams, and aminocarboxylic acids are polymerized while maintaining the solid state (hereinafter, this may be referred to as a "solid-state polymerization method").
4) A method of polymerizing a dicarboxylic acid halide component equivalent to a dicarboxylic acid and a diamine component (hereinafter, sometimes referred to as a "solution method").

Among these, a specific method for producing polyamide is preferably a production method including a hot melt polymerization method. Furthermore, when producing polyamide by a hot melt polymerization method, it is preferable to maintain the molten state until the polymerization is completed. To maintain the molten state, it is necessary to produce the polyamide composition under polymerization conditions suitable for the composition. Examples of polymerization conditions include the following: First, the polymerization pressure in the hot melt polymerization method is controlled to 14 kg/cm ² or more and 25 kg/cm ² or less (gauge pressure), and heating is continued. Next, the pressure in the vessel is reduced over 30 minutes or more until it reaches atmospheric pressure (gauge pressure: 0 kg/cm ² ).

In the method for producing polyamide, the polymerization mode is not particularly limited, and may be a batch system or a continuous system.
The polymerization apparatus used for producing polyamide is not particularly limited, and known apparatuses can be used. Specific examples of the polymerization apparatus include an autoclave reactor, a tumbler reactor, and an extruder reactor (e.g., a kneader).

Hereinafter, as a method for producing polyamide, a method for producing polyamide by batch-type hot melt polymerization will be specifically shown, but the method for producing polyamide is not limited to this.
First, an aqueous solution containing about 40% by mass to about 60% by mass of raw polyamide components (a combination of a dicarboxylic acid and a diamine, and optionally at least one selected from the group consisting of a lactam and an aminocarboxylic acid) is prepared. The aqueous solution is then concentrated to about 65% by mass to about 90% by mass in a concentration tank operated at a temperature of 110°C to 180°C and a pressure of about 0.035 MPa to 0.6 MPa (gauge pressure) to obtain a concentrated solution.
The resulting concentrated solution is then transferred to an autoclave, and heating is continued until the pressure in the autoclave reaches about 1.2 MPa or more and 2.2 MPa or less (gauge pressure).
Next, the pressure in the autoclave is maintained at about 1.2 MPa to 2.2 MPa (gauge pressure) while at least one of water and gas components is removed. Next, when the temperature reaches about 220°C to 260°C, the pressure is reduced to atmospheric pressure (gauge pressure: 0 MPa). After the pressure in the autoclave is reduced to atmospheric pressure, the pressure can be reduced as needed to effectively remove by-product water.
The autoclave is then pressurized with an inert gas such as nitrogen, and the polyamide melt is extruded from the autoclave as a strand. The extruded strand is cooled and cut to obtain polyamide pellets.

<(A) Characteristics of Polyamide>
[(A) Polyamide polymer terminal]
The polymer terminals of the polyamide (A) contained in the polyamide composition of the present embodiment are not particularly limited, but can be classified and defined as 1) to 4) below.
That is, 1) amino terminus, 2) carboxy terminus, 3) terminus with a capping agent, and 4) other terminus.
1) The amino terminus is a polymer end having an amino group (—NH ₂ group) and is derived from a diamine unit.
2) The carboxyl terminal is a polymer terminal having a carboxy group (—COOH group) and is derived from a dicarboxylic acid unit.
3) The term "terminals formed by a capping agent" refers to terminals formed when a capping agent is added during polymerization. Examples of the capping agent include the above-mentioned terminal capping agents.
4) Other terminals are polymer terminals that are not classified into the above 1) to 3). Specific examples of other terminals include terminals generated by deammoniating amino terminals and terminals generated by decarboxylating carboxyl terminals.

[(A) Weight average molecular weight Mw(A) of polyamide]
The weight average molecular weight Mw(A) can be used as an index of the molecular weight of (A) polyamide. The weight average molecular weight Mw(A) of the polyamide is preferably 12,000 to 44,000, more preferably 17,500 to 40,000, even more preferably 20,000 to 40,000, still more preferably 24,000 to 40,000, particularly preferably 28,000 to 37,500, and most preferably 32,000 to 36,000.
When the weight average molecular weight Mw(A) is within the above range, a polyamide composition having excellent flame retardancy, long-term heat resistance, weld strength, and laser welding strength can be obtained.
The weight average molecular weight Mw(A) can be measured using GPC as described in the examples below.

<(B) Phosphorus-based flame retardant>
The phosphorus-based flame retardant (B) contained in the polyamide composition of this embodiment is not particularly limited as long as it is a flame retardant containing phosphorus but not containing a halogen element, and examples of the phosphorus-based flame retardant (B) include phosphate ester-based flame retardants, melamine polyphosphate-based flame retardants, phosphazene-based flame retardants, phosphinic acid-based flame retardants, and red phosphorus-based flame retardants.
Among these, the phosphorus-based flame retardant (B) is preferably a phosphate ester-based flame retardant, a melamine polyphosphate-based flame retardant, a phosphazene-based flame retardant, or a phosphinic acid-based flame retardant, and more preferably a phosphinic acid-based flame retardant.

Specific examples of phosphinic acid flame retardants include at least one phosphinic acid salt selected from the group consisting of a phosphinic acid salt represented by the following general formula (1) (hereinafter sometimes abbreviated as "phosphinic acid salt (1)"), a diphosphinic acid salt represented by the following general formula (2) (hereinafter sometimes abbreviated as "diphosphinic acid salt (2)"), and condensates thereof.

(In general formula (1), R ¹¹ and R ¹² each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ^{M n11+} represents an n11-valent metal ion. M represents an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n11 is 2 or 3. When n11 is 2 or 3, a plurality of R ¹¹ and R ¹² may be the same or different.
In general formula (2), ^R21 and ^R22 are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ^Y21 is an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms. ^M'm21+ is an m21-valent metal ion. M' is an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n21 is an integer of 1 to 3. When n21 is 2 or 3, multiple ^R21 , ^R22 , and ^Y21 may be the same or different. m21 is 2 or 3. x is 1 or 2. When x is 2, multiple M' may be the same or different. n21, x, and m21 are integers that satisfy the relationship 2 × n21 = m21 × x.

[R ¹¹ , R ¹² , R ²¹ and R ²² ]
R ¹¹ , R ¹² , R ²¹ and R ²² are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. When n11 is 2 or 3, multiple R ¹¹ and R ¹² may be the same or different, but are preferably the same in terms of ease of production. When n21 is 2 or 3, multiple R ²¹ and R ²² may be the same or different, but are preferably the same in terms of ease of production.
The alkyl group may be chain-like or cyclic, but is preferably chain-like. The chain-like alkyl group may be linear or branched. Examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group. Examples of branched alkyl groups include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1,1-dimethylethyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, a 3,3-dimethylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, and a 1,1,2-trimethylpropyl group.
Examples of the aryl group include a phenyl group and a naphthyl group.
The alkyl group and the aryl group may have a substituent. Examples of the substituent in the alkyl group include an aryl group having 6 to 10 carbon atoms. Examples of the substituent in the aryl group include an alkyl group having 1 to 6 carbon atoms.
Specific examples of the alkyl group having a substituent include a benzyl group.
Specific examples of the aryl group having a substituent include a tolyl group and a xylyl group.
Among these, R ¹¹ , R ¹² , R ²¹ and R ²² are preferably alkyl groups having 1 to 6 carbon atoms, and more preferably methyl or ethyl groups.

[ ^Y21 ]
^Y21 is an alkylene group having from 1 to 10 carbon atoms or an arylene group having from 6 to 10 carbon atoms. When n21 is 2 or 3, a plurality of ^Y21 may be the same or different, but is preferably the same in terms of ease of production.
The alkylene group may be chain-like or cyclic, but is preferably chain-like. The chain-like alkylene group may be linear or branched. Examples of linear alkylene groups include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group. Examples of branched alkylene groups include a 1-methylethylene group and a 1-methylpropylene group.
Examples of the arylene group include a phenylene group and a naphthylene group.
The alkylene group and the arylene group may have a substituent. Examples of the substituent in the alkylene group include an aryl group having 6 to 10 carbon atoms. Examples of the substituent in the arylene group include an alkyl group having 1 to 6 carbon atoms.
Specific examples of the alkylene group having a substituent include a phenylmethylene group, a phenylethylene group, a phenyltrimethylene group, and a phenyltetramethylene group.
Specific examples of the substituted arylene group include a methylphenylene group, an ethylphenylene group, a tert-butylphenylene group, a methylnaphthylene group, an ethylnaphthylene group, and a tert-butylnaphthylene group.
Among these, Y ²¹ is preferably an alkylene group having 1 to 10 carbon atoms, more preferably a methylene group or an ethylene group.

[M and M′]
M and M' are each independently an ion of an element belonging to Group 2 or 15 of the periodic table, an ion of a transition element, a zinc ion, or an aluminum ion. Examples of ions of elements belonging to Group 2 of the periodic table include calcium ions and magnesium ions. Examples of ions of elements belonging to Group 15 of the periodic table include bismuth ions.
When x is 2, the plurality of M' may be the same or different, but it is preferable that they are the same for ease of production.
Among these, calcium, zinc or aluminum is preferred as M and M', and calcium or aluminum is more preferred.

[x]
x represents the number of M' and is 1 or 2. x can be appropriately selected depending on the type of M' and the number of diphosphinic acids.

[n11 and n21]
n11 represents the number of phosphinic acids and the valence of M, and is 2 or 3. n11 can be appropriately selected depending on the type and valence of M.
n21 represents the number of diphosphinic acids and is an integer of 1 to 3. n21 can be appropriately selected depending on the type and number of M'.

[m21]
m21 represents the valence of M' and is 2 or 3.
n21, x, and m21 are integers that satisfy the relational expression 2×n21=m21×x.

Specific examples of preferred phosphinates (1) include calcium dimethylphosphinate, magnesium dimethylphosphinate, aluminum dimethylphosphinate, zinc dimethylphosphinate, calcium ethylmethylphosphinate, magnesium ethylmethylphosphinate, aluminum ethylmethylphosphinate, zinc ethylmethylphosphinate, calcium diethylphosphinate, magnesium diethylphosphinate, aluminum diethylphosphinate, zinc diethylphosphinate, calcium methyl-n-propylphosphinate, magnesium methyl-n-propylphosphinate, aluminum methyl-n-propylphosphinate, zinc methyl-n-propylphosphinate, methane di(methylphosphinate) ) calcium, magnesium methane di(methylphosphinate), aluminum methane di(methylphosphinate), zinc methane di(methylphosphinate), calcium benzene-1,4-(dimethylphosphinate), magnesium benzene-1,4-(dimethylphosphinate), aluminum benzene-1,4-(dimethylphosphinate), zinc benzene-1,4-(dimethylphosphinate), calcium methylphenylphosphinate, magnesium methylphenylphosphinate, aluminum methylphenylphosphinate, zinc methylphenylphosphinate, calcium diphenylphosphinate, magnesium diphenylphosphinate, aluminum diphenylphosphinate, and zinc diphenylphosphinate are particularly preferred as the phosphinate (1) due to their excellent flame retardancy.

Specific examples of preferred diphosphinates (2) include calcium methane di(methylphosphinate), magnesium methane di(methylphosphinate), aluminum methane di(methylphosphinate), zinc methane di(methylphosphinate), calcium benzene-1,4-di(methylphosphinate), magnesium benzene-1,4-di(methylphosphinate), aluminum benzene-1,4-di(methylphosphinate), and zinc benzene-1,4-di(methylphosphinate).

Methods for producing phosphinates include, but are not limited to, those described in Patent Documents 5, 6, and 7. Specifically, phosphinates are produced in an aqueous solution using phosphinic acid and a metal carbonate, metal hydroxide, or metal oxide. These are essentially monomeric compounds, but depending on the reaction conditions and environment, they also include polymeric phosphinates, which are condensates with a degree of condensation of 1 to 3.

The content of the (B) phosphorus-based flame retardant is preferably 0.1 mass% or more and 30 mass% or less, more preferably 5 mass% or more and 30 mass% or less, still more preferably 10 mass% or more and 29 mass% or less, and particularly preferably 15 mass% or more and 29 mass% or less, based on the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer.
By setting the content of the (B) phosphorus-based flame retardant to the above lower limit or more, a polyamide composition with superior flame retardancy can be obtained. On the other hand, by setting the content of the (B) phosphorus-based flame retardant to the above upper limit or less, a polyamide composition with superior flame retardancy can be obtained without impairing the properties of the polyamide copolymer.

<(C) Styrene copolymer>
The (C) styrene copolymer contained in the polyamide composition of this embodiment refers to a styrene copolymer having a styrene content of 10% by weight or more. Specific examples of the (C) styrene copolymer include styrene-acrylonitrile copolymers (AS resins), copolymers of styrene monomers with maleimide-based monomers such as maleimide and N-phenylmaleimide, and acrylamide-based monomers such as acrylamide. Furthermore, copolymers in which a portion of the styrene in a styrene-based polymer has been substituted with a monomer such as α-methylstyrene, p-methylstyrene, vinylxylene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, p-t-butylstyrene, ethylstyrene, or vinylnaphthalene may also be used. Among these, a styrene copolymer (C) containing styrene units and acrylonitrile units is preferred due to its excellent flame retardancy and long-term heat resistance. An AS resin having an acrylonitrile unit content of 30% by weight or more, and 35% by weight or more, of the total weight of the constituent units of the (C) styrene copolymer is particularly preferred.
It is believed that the addition of styrene copolymer improves fluidity and dispersibility of the flame retardant, which allows for the formation of a strong and dense char (a carbonized layer formed by combustion) during combustion, thereby improving flame retardancy. It is also believed that the addition of styrene copolymer improves fluidity and dispersibility of the heat stabilizer, which increases the radical trapping efficiency of the heat stabilizer and improves long-term heat resistance.

The content of the (C) styrene copolymer is from 0.1% by mass to 7% by mass, preferably from 0.5% by mass to 6% by mass, more preferably from 1% by mass to 5% by mass, and even more preferably from 1% by mass to 3% by mass, based on the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer.
By setting the content of the (C) polymer within the above range, it is possible to obtain a polyamide composition that is excellent in flame retardancy and has good weld strength and long-term heat resistance when molded into a molded product.

[(C) Weight average molecular weight Mw(C) of polymer]
The weight average molecular weight Mw(C) can be used as an index of the molecular weight of the (C) polymer. The weight average molecular weight Mw(C) of the (C) polymer is preferably from 5,000 to 220,000, more preferably from 5,000 to 150,000, even more preferably from 7,000 to 15,000, and most preferably from 70,000 to 100,000.
When the weight average molecular weight Mw(C) is within the above range, it is possible to obtain a polyamide composition that has both flame retardancy and good weld strength and long-term heat resistance when molded into a molded article.
The weight average molecular weight Mw can be measured using GPC as described in the examples below.

<(D) Filler>
The polyamide composition of the present embodiment may further contain a filler (D) in addition to the components (A) to (C). By containing the filler (D), the polyamide composition can be made to have more excellent mechanical properties such as toughness and rigidity.

The filler (D) contained in the polyamide composition of the present embodiment is not particularly limited, and examples thereof include glass fiber, carbon fiber, calcium silicate fiber, potassium titanate fiber, aluminum borate fiber, glass flake, talc, kaolin, mica, hydrotalcite, zinc carbonate, calcium hydrogen phosphate, wollastonite, zeolite, boehmite, magnesium oxide, calcium silicate, sodium aluminosilicate, magnesium silicate, ketjen black, acetylene black, furnace black, carbon nanotubes, graphite, brass, copper, silver, aluminum, nickel, iron, calcium fluoride, montmorillonite, swellable fluoromica, and apatite.
These fillers (D) may be used singly or in combination of two or more.
Among these, the filler (D) is preferably glass fiber, carbon fiber, glass flake, talc, kaolin, mica, calcium hydrogen phosphate, wollastonite, carbon nanotube, graphite, calcium fluoride, montmorillonite, swellable fluoromica, or apatite from the viewpoint of rigidity, strength, etc. Furthermore, the filler (D) is more preferably glass fiber or carbon fiber, and even more preferably glass fiber.

When the (D) filler is glass fiber or carbon fiber, the number average fiber diameter (D) is preferably 3 μm or more and 30 μm or less. The weight average fiber length (L) is preferably 100 μm or more and 750 μm or less. Furthermore, the aspect ratio ((L)/(D)) of the number average fiber diameter (D) to the weight average fiber length (L) is preferably 10 or more and 100 or less. By using glass fiber or carbon fiber having the above configuration, better properties can be achieved.
When the filler (D) is glass fiber, the number average fiber diameter (D) is preferably 3 μm or more and 30 μm or less, the weight average fiber length (L) is preferably 103 μm or more and 500 μm or less, and the aspect ratio ((L)/(D)) is preferably 3 or more and 100 or less.

The number average fiber diameter and weight average fiber length of the filler (D) can be measured using the following method.
First, a molded product of the polyamide composition is dissolved in a solvent in which the polyamide is soluble, such as formic acid. Next, from the resulting insoluble components, for example, 100 or more fillers are arbitrarily selected. The fillers can then be observed using an optical microscope, a scanning electron microscope, or the like to determine the filler size.

The content of the filler (D) in the polyamide composition is preferably 1% by mass or more and 80% by mass or less, more preferably 10% by mass or more and 70% by mass or less, even more preferably 15% by mass or more and 60% by mass or less, particularly preferably 20% by mass or more and 55% by mass or less, and most preferably 25% by mass or more and 50% by mass or less, relative to the total mass of the polyamide composition.
When the content of the (D) filler is equal to or greater than the above lower limit, the mechanical properties such as strength and rigidity of the polyamide composition tend to be further improved. On the other hand, when the content of the (D) filler is equal to or less than the above upper limit, a polyamide composition having even more excellent laser weld strength tends to be obtained.
In particular, when the (D) filler is glass fiber and the content of the (D) filler is within the above range relative to the total mass of the polyamide composition, the mechanical properties such as strength and rigidity of the polyamide composition tend to be further improved.

<(E) Other Additives>
In addition to the components (A) to (C) above, the polyamide composition of this embodiment may also contain (E) other additives commonly used in polyamides, provided that the effects of the polyamide composition of this embodiment are not impaired. Examples of (E) other additives include (E1) moldability improvers, (E2) deterioration inhibitors, (E3) nucleating agents, and (E4) heat stabilizers.
The content of (E) other additives in the polyamide composition of the present embodiment varies depending on the type of additive and the use of the polyamide composition, 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.

[(E1) Moldability improver]
The moldability improver (E1) contained in the polyamide composition of the present embodiment is not particularly limited, but examples thereof include higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, etc. The moldability improver is also used as a "lubricant."

(higher fatty acids)
Examples of higher fatty acids include linear or branched, saturated or unsaturated aliphatic monocarboxylic acids having from 8 to 40 carbon atoms.
Examples of the linear saturated aliphatic monocarboxylic acid having from 8 to 40 carbon atoms include lauric acid, palmitic acid, stearic acid, behenic acid, and montanic acid.
Examples of branched saturated aliphatic monocarboxylic acids having from 8 to 40 carbon atoms include isopalmitic acid and isostearic acid.
Examples of the linear unsaturated aliphatic monocarboxylic acid having from 8 to 40 carbon atoms include oleic acid and erucic acid.
Examples of branched unsaturated aliphatic monocarboxylic acids having 8 to 40 carbon atoms include isooleic acid.
Among these, stearic acid or montanic acid is preferred as the higher fatty acid.

(Higher fatty acid metal salts)
The higher fatty acid metal salt is a metal salt of a higher fatty acid.
Examples of the metal element of the metal salt include elements of Groups 1, 2 and 3 of the periodic table, zinc, aluminum, and the like.
Examples of elements in Group 1 of the periodic table include sodium and potassium.
Examples of Group 2 elements in the periodic table include calcium and magnesium.
Examples of Group 3 elements in the periodic table include scandium and yttrium.
Among these, elements of Groups 1 and 2 of the Periodic Table of Elements or aluminum are preferred, and sodium, potassium, calcium, magnesium or aluminum is more preferred.

Specific examples of higher fatty acid metal salts include calcium stearate, aluminum stearate, zinc stearate, magnesium stearate, calcium montanate, sodium montanate, and calcium palmitate.
Among these, metal salts of higher fatty acids are preferably metal salts of montanic acid or metal salts of stearic acid.

(Higher fatty acid ester)
The higher fatty acid ester is an ester of a higher fatty acid and an alcohol.
The higher fatty acid ester is preferably an ester of an aliphatic carboxylic acid having 8 to 40 carbon atoms and an aliphatic alcohol having 8 to 40 carbon atoms.
Examples of the aliphatic alcohol having 8 to 40 carbon atoms include stearyl alcohol, behenyl alcohol, and lauryl alcohol.
Specific examples of higher fatty acid esters include stearyl stearate and behenyl behenate.

(Higher fatty acid amide)
Higher fatty acid amides are amide compounds of higher fatty acids.
Examples of higher fatty acid amides include stearic acid amide, oleic acid amide, erucic acid amide, ethylene bisstearylamide, ethylene bisoleylamide, N-stearyl stearic acid amide, and N-stearyl erucic acid amide.
These higher fatty acids, higher fatty acid metal salts, higher fatty acid esters and higher fatty acid amides may be used singly or in combination of two or more.

[(E2) Deterioration inhibitor]
The deterioration inhibitor (E2) contained in the polyamide composition of the present embodiment is used for the purposes of preventing thermal deterioration and discoloration when heated, and improving heat aging resistance.
The deterioration inhibitor (E2) is not particularly limited, but examples thereof include copper compounds, phenol-based stabilizers, phosphite-based stabilizers, hindered amine-based stabilizers, triazine-based stabilizers, benzotriazole-based stabilizers, benzophenone-based stabilizers, cyanoacrylate-based stabilizers, salicylate-based stabilizers, and sulfur-based stabilizers.
Examples of copper compounds include copper acetate and copper iodide.
Examples of the phenolic stabilizer include hindered phenol compounds.
These deterioration inhibitors (E2) may be used alone or in combination of two or more.

[(E3) Nucleating Agent]
(E3) Nucleating agent means a substance that, when added, provides at least one of the following effects (1) to (3):
(1) The effect of increasing the crystallization peak temperature of the polyamide composition.
(2) The effect of reducing the difference between the extrapolated onset temperature and the extrapolated end temperature of the crystallization peak.
(3) The effect of making the spherulites in the resulting molded product finer or more uniform in size.

Examples of the nucleating agent (E3) include, but are not limited to, talc, boron nitride, mica, kaolin, silicon nitride, carbon black, potassium titanate, and molybdenum disulfide.
The nucleating agent (E3) may be used alone or in combination of two or more.
Among these, talc or boron nitride is preferred as the nucleating agent (E3) from the viewpoint of nucleating agent effect.

In addition, since the effect of the nucleating agent is high, the number average particle size of the nucleating agent (E3) is preferably 0.01 μm or more and 10 μm or less.
The number-average particle size of the nucleating agent can be measured using the following method. First, the molded product is dissolved in a solvent in which polyamide is soluble, such as formic acid. Next, from the resulting insoluble components, for example, 100 or more nucleating agents are arbitrarily selected. Next, the number-average particle size can be determined by observing the particles with an optical microscope, a scanning electron microscope, or the like, and measuring the particle size.

The content of the nucleating agent in the polyamide composition of the present embodiment is preferably 0.001 parts by mass or more and 1 part by mass or less, more preferably 0.001 parts by mass or more and 0.5 parts by mass or less, and even more preferably 0.001 parts by mass or more and 0.09 parts by mass or less, relative to 100 parts by mass of polyamide ((A) aliphatic polyamide and (B) semi-aromatic polyamide).
By setting the content of the nucleating agent to at least the above lower limit per 100 parts by mass of polyamide, the heat resistance of the polyamide composition tends to be further improved. On the other hand, by setting the content of the nucleating agent to at most the above upper limit per 100 parts by mass of polyamide, a polyamide composition with better toughness can be obtained.

[(E4) Heat stabilizer]
Examples of the heat stabilizer (E4) include, but are not limited to, phenol-based heat stabilizers, phosphorus-based heat stabilizers, amine-based heat stabilizers, and metal salts of elements of Groups 3, 4, and 11 to 14 of the Periodic Table of the Elements.

(Phenol-based heat stabilizer)
Examples of phenolic heat stabilizers include, but are not limited to, hindered phenol compounds, etc. Hindered phenol compounds have the property of imparting excellent heat resistance and light resistance to resins such as polyamides and fibers.
Examples of the hindered phenol compound include, but are not limited to, N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenylpropionamide], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], onate], 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propynyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, and the like.
These hindered phenol compounds may be used alone or in combination of two or more.

When a phenolic heat stabilizer is used, the content of the phenolic heat stabilizer in the polyamide composition is preferably 0.01 mass % or more and 1 mass % or less, and more preferably 0.05 mass % or more and 1 mass % or less, relative to the total mass of the polyamide composition.
When the content of the phenolic heat stabilizer is within the above range, the heat aging resistance of the polyamide composition can be further improved, and the amount of gas generation can be further reduced.

(Phosphorus-based heat stabilizer)
Examples of phosphorus-based heat stabilizers include, but are not limited to, pentaerythritol-type phosphite compounds, trioctyl phosphite, trilauryl phosphite, tridecyl phosphite, octyl diphenyl phosphite, trisisodecyl phosphite, phenyl diisodecyl phosphite, phenyl di(tridecyl) phosphite, diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl (tridecyl) phosphite, triphenyl phosphite, tris(nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,4-di-t-butyl-5-methylphenyl) phosphite, ) phosphite, tris(butoxyethyl)phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-tetra-tridecyl)diphosphite, tetra(C12 to C15 mixed alkyl)-4,4'-isopropylidenediphenyl diphosphite, 4,4'-isopropylidenebis(2-t-butylphenyl)-di(nonylphenyl)phosphite, tris(biphenyl)phosphite, tetra(tridecyl)-1,1,3-tris(2-methyl-5-t-butyl-4-hydroxyphenyl)butane diphosphite, tetra(tridecyl)-4,4'-butylidenebis(3-methyl-6-t-butylphenyl)diphosphite, tetra( C1 to C15 mixed alkyl)-4,4'-isopropylidene diphenyl diphosphite, tris(mono, di mixed nonylphenyl) phosphite, 4,4'-isopropylidenebis(2-t-butylphenyl)-di(nonylphenyl) phosphite, 9,10-di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, tris(3,5-di-t-butyl-4-hydroxyphenyl) phosphite, hydrogenated-4,4'-isopropylidene diphenyl polyphosphite, bis(octylphenyl)-bis(4,4'-butylidenebis(3-methyl-6-t-butylphenyl))-1,6-hexanol diphosphite, hexatridecyl-1, Examples of suitable phosphate groups include 1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)diphosphite, tris(4,4'-isopropylidenebis(2-t-butylphenyl))phosphite, tris(1,3-stearoyloxyisopropyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, 2,2-methylenebis(3-methyl-4,6-di-t-butylphenyl)2-ethylhexylphosphite, tetrakis(2,4-di-t-butyl-5-methylphenyl)-4,4'-biphenylene diphosphite, and tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphite.
These phosphorus-based heat stabilizers may be used alone or in combination of two or more.

Examples of the pentaerythritol phosphite compound include, but are not limited to, 2,6-di-t-butyl-4-methylphenyl-phenyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-methyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2-ethylhexyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-isodecyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-lauryl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2-ethylhexyl-pentaerythritol diphosphite, ,6-di-t-butyl-4-methylphenyl-isotridecyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-stearyl pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-cyclohexyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-benzyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-ethylcellosolve-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-butylcarbitol-pentaerythritol Diphosphite, 2,6-di-t-butyl-4-methylphenyl-octylphenyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-nonylphenyl pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-ethylphenyl)pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2,6-di-t-butylphenyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2,4-di-t- butylphenyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2,4-di-t-octylphenyl-pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2-cyclohexylphenyl-pentaerythritol diphosphite, 2,6-di-t-amyl-4-methylphenyl-phenyl pentaerythritol diphosphite, bis(2,6-di-t-amyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-octyl-4-methylphenyl)pentaerythritol diphosphite, and the like.
These pentaerythritol-type phosphite compounds may be used alone or in combination of two or more.

When a phosphorus-based heat stabilizer is used, the content of the phosphorus-based heat stabilizer in the polyamide composition is preferably 0.01 mass % or more and 1 mass % or less, and more preferably 0.05 mass % or more and 1 mass % or less, relative to the total mass of the polyamide composition.
When the content of the phosphorus-based heat stabilizer is within the above range, the heat aging resistance of the polyamide composition can be further improved, and the amount of gas generation can be further reduced.

(amine-based heat stabilizer)
Examples of the amine-based heat stabilizer include, but are not limited to, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(phenylacetoxy)-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyl Oxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4-(ethylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, 4-(cyclohexylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, 4-(phenylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidyl)-carbonate, bis(2,2,6,6-tetramethyl-4-piperidyl)-oxalate, bis(2,2,6,6-tetramethyl-4-piperidyl)-malonate, bis(2,2,6,6-tetramethyl-4 -piperidyl)-sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)-adipate, bis(2,2,6,6-tetramethyl-4-piperidyl)-terephthalate, 1,2-bis(2,2,6,6-tetramethyl-4-piperidyloxy)-ethane, α,α'-bis(2,2,6,6-tetramethyl-4-piperidyloxy)-p-xylene, bis(2,2,6,6-tetramethyl-4-piperidyltolylene-2,4-dicarbamate, bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene-1,6-dicarbamate, tris(2,2,6,6-tetramethyl-4-piperidyl)-benzene-1,3, 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro(5,5)undecane]diethanol.
These amine-based heat stabilizers may be used alone or in combination of two or more.

When an amine-based heat stabilizer is used, the content of the amine-based heat stabilizer in the polyamide composition is preferably 0.01% by mass or more and 1% by mass or less, and more preferably 0.05% by mass or more and 1% by mass or less, relative to the total mass of the polyamide composition.
When the content of the amine-based heat stabilizer is within the above range, the heat aging resistance of the polyamide composition can be further improved, and the amount of gas generation can be further reduced.

(Metal salts of elements of groups 3, 4 and 11 to 14 of the periodic table)
There are no particular limitations on the metal salts of elements in Groups 3, 4, and 11 to 14 of the periodic table, as long as they are salts of metals belonging to these groups.
Among these, copper salts are preferred from the viewpoint of further improving the heat aging resistance of the polyamide composition. Examples of such copper salts include, but are not limited to, copper acetate, copper propionate, copper benzoate, copper adipate, copper terephthalate, copper isophthalate, copper salicylate, copper nicotinate, copper stearate, and copper complex salts in which copper is coordinated with a chelating agent.
Examples of the chelating agent include ethylenediamine and ethylenediaminetetraacetic acid.
These copper salts may be used alone or in combination of two or more.
Among these, copper acetate is preferred as the copper salt. When copper acetate is used, a polyamide composition can be obtained that is more excellent in heat aging resistance and can more effectively inhibit metal corrosion of the screw and cylinder during extrusion (hereinafter, also simply referred to as "metal corrosion").

When a copper salt is used as the heat stabilizer (E4), the content of the copper salt in the polyamide composition is preferably 0.01 mass % or more and 0.60 mass % or less, and more preferably 0.02 mass % or more and 0.40 mass % or less, relative to the total mass of the polyamide (A).
When the content of the copper salt is within the above range, the heat aging resistance of the polyamide composition can be further improved, and copper precipitation and metal corrosion can be more effectively suppressed.

From the viewpoint of improving the heat aging resistance of the polyamide composition, the content concentration of the copper element derived from the copper salt is preferably ¹⁰ parts by mass or more and 2,000 parts by mass or less, more preferably 30 parts by mass or more and 1,500 parts by mass or less, and even more preferably 50 parts by mass or more and 500 parts by mass or less, per 106 parts by mass (1,000,000 parts by mass) of the polyamide (A).

The components of the heat stabilizer (E4) described above may be used alone or in combination of two or more.

<Method for producing polyamide 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 polyamide (A) with the above components (B) to (C), and, if necessary, components (D) and (E).

Examples of a method for mixing the above components (A) to (C) and, if necessary, the components (D) and (E) include the following method (1) or (2).
(1) A method in which the above components (A) to (C), and, if necessary, components (D) and (E), are mixed using a Henschel mixer or the like, and the mixture is fed into a melt kneader and kneaded.
(2) A method in which the above components (A) to (C), and, if necessary, component (D), are mixed in advance using a Henschel mixer or the like in a single-screw or twin-screw extruder to prepare a mixture containing the components (A) to (C), and, if necessary, component (E), and the mixture is fed to a melt kneader and kneaded, and then component (D) is optionally blended in through a side feeder.

The components that make up the polyamide composition can be supplied to the melt kneader by supplying all of the components to the same supply port at once, or by supplying each component through a different supply port.

When the polyamide (A) contains an aliphatic polyamide (A1), the melt-kneading temperature is preferably a temperature that is higher by about 1°C or more and 100°C or less than the melting point of the aliphatic polyamide (A1), and more preferably a temperature that is higher by about 10°C or more and 50°C or less than the melting point of the aliphatic polyamide (A1).
The shear rate in the kneader is preferably about 100 sec ⁻¹ or more, and the average residence time during kneading is preferably about 0.5 to 5 minutes.
Any known melt-kneading device may be used, and for example, a single-screw or twin-screw extruder, a Banbury mixer, a melt-kneader (mixing roll, etc.), etc. are preferably used.
The amount of each component blended when producing the polyamide composition of this embodiment is the same as the content of each component in the polyamide composition described above.

≪Molded products≫
The molded article of this embodiment is obtained by molding the polyamide composition of the above embodiment.
The molded article of this embodiment is excellent in flame retardancy and long-term heat resistance, even though it contains a non-halogen flame retardant.

The method for obtaining the molded product 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, molding with other materials, 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).

<Application>
The molded article of the present embodiment contains the polyamide composition of the above embodiment, has excellent flame retardancy and long-term heat resistance, and can be used for a variety of applications.
The molded article of this embodiment can be suitably used in, for example, the automotive field, the electrical and electronic field, the mechanical and industrial field, the office equipment field, and the aviation and space field.

≪Addition method≫
The method of this embodiment is a method of adding (C) a styrene copolymer as a flame retardant aid to a resin composition containing (A) a polyamide and (B) a phosphorus-based flame retardant. As described above, adding (C) a styrene copolymer to a resin composition containing (A) a polyamide and (B) a phosphorus-based flame retardant improves the fluidity of the resin composition and the dispersibility of the flame retardant (B) phosphorus-based flame retardant. This is thought to be why a strong and dense char (a carbonized layer formed by combustion) can be formed during combustion, improving the flame retardancy. Furthermore, adding (C) a styrene copolymer to a resin composition containing (A) a polyamide and (B) a phosphorus-based flame retardant improves the fluidity of the resin composition and the dispersibility of the heat stabilizer, thereby increasing the radical trapping efficiency of the heat stabilizer and improving long-term heat resistance.

The resin composition may contain the components (D) and (E) in addition to the components (A) and (B). Components (A) to (E) may be the same as those exemplified for the polyamide composition.

The present invention will be explained in detail below using specific examples and comparative examples, but the present invention is not limited to the following examples.

The components of the polyamide compositions used in the examples and comparative examples are described below.

<Components>
[(A1) Aliphatic polyamide]
A1-1: Polyamide 66

[(A2) Semi-aromatic polyamide]
A2-1: Polyamide 6I
A2-2: Polyamide 6I/6T (manufactured by EMS Co., Ltd., model number: G21, content of isophthalic acid units in all dicarboxylic acid units: 70 mol%, molecular weight: 27,000)

[(B) Phosphorus-based flame retardant]
B-1: Phosphinic acid flame retardant, aluminum diethylphosphinate (manufactured by Clariant, trade name: "Exolit OP1230")
B-2: Phosphinic acid flame retardant, calcium diethylphosphinate (manufactured by Taihei Chemical Industry Co., Ltd.)

[(B') Non-phosphorus flame retardant]
B'-1: Nitrogen-based flame retardant melamine cyanurate (manufactured by Nissan Chemical Industries, Ltd.)

[(C) Styrene copolymer]
C-1: Styrene-acrylonitrile copolymer (AS) (manufactured by Asahi Kasei Corporation) (acrylonitrile content: 40% by weight, molecular weight: 80,000)
C-2: Styrene-acrylonitrile copolymer (AS) (manufactured by Asahi Kasei Corporation) (acrylonitrile content: 25% by weight, molecular weight: 140,000)
C-3: Styrene-acrylonitrile copolymer (AS) (manufactured by Asahi Kasei Corporation) (acrylonitrile content: 30% by weight, molecular weight: 130,000)

[(D) Filler]
D-1: Glass fiber (GF) (manufactured by Nippon Electric Glass Co., Ltd., product name "ECS03T275H", average fiber diameter 10 μmφ, cut length 3 mm)

[(E) Other Additives]
E-1: Phenolic heat stabilizer (manufactured by Ciba Specialty Chemicals, product name: "Irganox 1098")

<Production of Polyamide>
The methods for producing the aliphatic polyamide A1-1 and the semi-aromatic polyamide A2-1 are described in detail below. The aliphatic polyamide A1-1 and the semi-aromatic polyamide A2-1 obtained by the methods described below were dried in a nitrogen stream to adjust the moisture content to about 0.2% by mass, and then used as raw materials for the polyamide compositions in the examples and comparative examples described below.

Synthesis Example 1 Synthesis of Aliphatic Polyamide A1-1 (Polyamide 66) A polyamide polymerization reaction was carried out by the "hot melt polymerization method" as follows.
First, 1500 g of an equimolar salt of adipic acid and hexamethylenediamine was dissolved in 1500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers. This aqueous solution was charged into an autoclave with an internal volume of 5.4 L and purged with nitrogen. Next, the solution was concentrated by gradually removing water vapor to a solution concentration of 70% by mass while stirring at a temperature of approximately 110°C to 150°C. The internal temperature was then raised to 220°C. At this time, the autoclave was pressurized to 1.8 MPa. The reaction was continued for 1 hour while gradually removing water vapor to maintain the pressure at 1.8 MPa until the internal temperature reached 245°C. The pressure was then reduced over 1 hour. The autoclave was then maintained at a reduced pressure of 650 torr (86.66 kPa) for 10 minutes using a vacuum device. The final internal temperature of the polymerization was 265°C. The mixture was then pressurized with nitrogen to form a strand from the lower spinneret (nozzle), cooled with water, cut, and discharged in the form of pellets. The pellets were then dried at 100°C in a nitrogen atmosphere for 12 hours to obtain aliphatic polyamide A1-1 (polyamide 66).
The resulting aliphatic polyamide A1-1 (polyamide 66) had Mw(A1)=40,000.

Synthesis Example 2 Synthesis of Semi-Aromatic Polyamide A2-1 (Polyamide 6I) Polyamide polymerization reaction was carried out by the "hot melt polymerization method" as follows.
First, 1500 g of an equimolar salt of isophthalic acid and hexamethylenediamine, a 1.5 mol% excess adipic acid relative to the total equimolar salt components, and 0.5 mol% acetic acid were dissolved in 1500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers. Next, the solution was concentrated by gradually removing water vapor to a solution concentration of 70% by mass while stirring at a temperature of approximately 110°C to 150°C. The internal temperature was then raised to 220°C. At this time, the autoclave was pressurized to 1.8 MPa. The reaction was continued for 1 hour while gradually removing water vapor to maintain the pressure at 1.8 MPa until the internal temperature reached 245°C. The pressure was then reduced over 30 minutes. The autoclave was then maintained at a reduced pressure of 650 torr (86.66 kPa) for 10 minutes using a vacuum device. The final internal temperature of the polymerization was 265°C. The mixture was then pressurized with nitrogen and formed into strands from the lower spinneret (nozzle), which were then cooled with water, cut, and discharged in pellet form. The pellets were then dried at 100°C under a nitrogen atmosphere for 12 hours to obtain semi-aromatic polyamide A2-1 (polyamide 6I).
The resulting semi-aromatic polyamide A2-1 (polyamide 6I) had a content of isophthalic acid units in dicarboxylic acid units of 100 mol % and Mw(A2) of 20,000.

<Physical properties and evaluation>
First, the polyamide composition pellets obtained in the Examples and Comparative Examples were dried in a nitrogen stream to reduce the moisture content in the polyamide composition to 500 ppm or less. Next, the pellets of each polyamide composition with the adjusted moisture content were used to measure various physical properties and perform various evaluations using the methods described below.

[Physical Property 1] Tan δ Peak Temperature Using a PS40E injection molding machine manufactured by Nissei Kogyo Co., Ltd., a molded article was molded in accordance with JIS-K7139 under the injection molding conditions of a cylinder temperature of 290°C, a mold temperature of 100°C, injection for 10 seconds, and cooling for 10 seconds. This molded article was measured under the following conditions using a dynamic viscoelasticity evaluation device (EPLEXOR500N manufactured by GABO Corporation).

(Measurement conditions)
Measurement mode: Tension Measurement frequency: 8.00 Hz
Temperature rise rate: 3°C/min Temperature range: -100°C to 250°C

The ratio of storage modulus E1 to loss modulus E2 (E2/E1) was defined as tan δ, and the highest temperature was defined as the tan δ peak temperature.

[Property 2] Molecular weight (Mw) of polyamide composition
The weight average molecular weight (Mw) of the polyamide compositions obtained in the examples and comparative examples was measured using GPC under the following measurement conditions.

(Measurement conditions)
Measuring device: HLC-8020 manufactured by Tosoh Corporation
Solvent: hexafluoroisopropanol solvent Standard sample: PMMA (polymethyl methacrylate) (manufactured by Polymer Laboratory Co., Ltd.) GPC column: TSK-GEL GMHHR-M and G1000HHR

[Evaluation 1] Flame Retardancy Measurement was carried out using the method of UL94 (a standard established by Under Writers Laboratories Inc., USA). Test specimens (length 127 mm, width 12.7 mm, thickness 1.6 mm) were prepared by attaching a UL test specimen mold (mold temperature = 100°C) to an injection molding machine (PS40E manufactured by Nissei Kogyo Co., Ltd.) and molding each polyamide composition at a cylinder temperature of 290°C. The injection pressure was set at the full filling pressure + 2% when molding the UL test specimen. The flame retardancy grade was evaluated according to the UL94 standard (vertical flame test) to determine whether the specimen was classified as V-0, V-1, or V-2. The smaller the grade, the higher the flame retardancy.

[Evaluation 2] Weld Strength: Test specimens were obtained by molding using an injection molding machine (PS40E manufactured by Nissei Kogyo Co., Ltd.) equipped with a mold that allowed molten resin to flow from both longitudinal ends of a 127 mm long, 12.7 mm wide, and 1.6 mm thick specimen, forming a weld in the center of the longitudinal direction. Specific molding conditions were injection + pressure retention time of 25 seconds, cooling time of 15 seconds, mold temperature of 80°C, and molten resin temperature set to the polyamide's high-temperature melting peak temperature (Tm2) + 20°C. The molded test specimens were subjected to a tensile test in accordance with ASTM D638, except that the chuck distance was 50 mm and the tensile speed was 50 mm/min, to determine the tensile strength.

[Evaluation 3] Long-term heat resistance The multipurpose test piece (type A) for the above tensile strength was heated at 120° C. in a hot air circulating oven to cause thermal degradation.
After 1000 hours in the oven, the specimens were removed from the oven and cooled at 23°C for at least 24 hours. The cooled multipurpose test specimens (Type A) were then subjected to a tensile test in accordance with ISO 527 at a tensile speed of 5 mm/min in the same manner as described above, and the tensile strengths were measured. The heat aging retention was calculated using the following formula:

Heat resistance retention (%) = tensile strength after aging / tensile strength before aging x 100

[Evaluation 4] Laser welding strength
Each polyamide resin composition was dry-blended with a colored masterbatch for laser welding (Orient Chemical Industry: eBIND ACW-9871, hereinafter simply referred to as ACW) at a dilution ratio of 60 times, and a flat plate measuring 60 mm x 60 mm x 2.0 mm thick was molded, which was then cut into a flat plate measuring 28 mm x 60 mm x 2.0 mm thick to produce member A. Specific molding conditions were a mold temperature of 80°C and a molten resin temperature of the polyamide's higher-temperature melting peak temperature (Tm2) + 20°C.
In addition, 1500 ppm of carbon black (primary particle size 27 nm) was dry blended with 100 parts by mass of the polyamide resin composition, and a flat plate measuring 60 mm × 60 mm × 2.0 mm thick was molded from the dry blend. This was then cut into a flat plate measuring 25 mm × 60 mm × 2.0 mm thick to prepare Member B.
With these members A and B overlapping and fixed by 20 mm in the long side direction of each member, the head of the laser welding machine was irradiated with a laser at a scanning speed of 50.0 mm/sec and an output of 150 W from the member A side from one end of the test piece to the other end in a direction parallel to the short side of the test piece, and at the same time, that portion was cooled with air to prepare the test piece.
The prepared test piece was subjected to a tensile test using a universal testing machine manufactured by Instron Corporation, with both ends of member A and member B of the test piece clamped in chucks using a 30 kN load cell, under test conditions of a chuck distance of 30 mm and a tensile test speed of 5.0 mm/min, and the maximum point load was measured.

<Production of Polyamide Composition>
[Example 1]
Using a Toshiba Machine Co., Ltd. TEM35mm twin-screw extruder (set temperature: 280°C, screw rotation speed: 300 rpm), a pre-blended mixture of (A) polyamide A1-1, (C) styrene copolymer C-1, and (E) other additive E-1 was fed through the top feed port located at the most upstream end of the extruder. Furthermore, (B) phosphorus-based flame retardant B-1 and (D) filler D-1 were fed through the side feed port located downstream of the extruder (in a state where the resin fed through the top feed port was fully molten). The molten mixture extruded from the die head was cooled in the form of strands and pelletized to obtain pellets of the polyamide composition. The blending amounts were as shown in Table 1.
The pellets of the polyamide composition thus obtained were used to produce molded articles by the above-mentioned method, and various physical properties were measured and evaluated. The evaluation results are shown in Table 1.

[Examples 2 to 12, Comparative Examples 1 to 6]
The test pieces were produced in the same manner as in Example 1, except that the components (A) to (E) were formulated as shown in Table 1. The evaluation results are shown in Tables 1 and 2. In Table 2, "N.D." stands for No Data, and indicates that the strength of the test piece produced was so low that it could not be measured.

Table 1 shows that the polyamide compositions (Examples 1 to 12) containing (A) polyamide, (B) phosphorus-based flame retardant, and (C) styrene copolymer, in which the content of (C) styrene copolymer relative to the total mass of components (A) to (C) was in the range of 0.1% by mass or more and 7% by mass or less, produced molded articles that were both flame retardant and long-term heat resistant.

Furthermore, the polyamide compositions (Examples 2 to 12) containing (A1) aliphatic polyamide A1-1 and (A2) semi-aromatic polyamide A2-1 or A2-2 provided molded articles with particularly good laser welding strength.
Furthermore, in the polyamide compositions containing the styrene copolymer C-1 with a high acrylonitrile content (Examples 2, 3, and 6 to 10), molded articles having particularly good flame retardancy and long-term heat resistance were obtained.

On the other hand, in polyamide compositions (Comparative Examples 1 to 6) that did not contain the (C) styrene copolymer or in which the content of the (C) styrene copolymer relative to the total mass of components (A) to (C) exceeded 7 mass%, molded articles that exhibited both flame retardancy and long-term heat resistance could not be obtained.

From the above, it has become clear that the polyamide composition of this embodiment can produce molded articles that combine flame retardancy and long-term heat resistance, even when containing a non-halogen flame retardant.

The polyamide composition of this embodiment allows for the production of molded articles that combine flame retardancy and long-term heat resistance while containing a non-halogen flame retardant. The molded articles of this embodiment can be suitably used in the automotive, electrical and electronic, mechanical and industrial, office equipment, and aviation and space fields.

Claims (16)

(A) polyamide,
(B) a phosphorus-based flame retardant, and
(C) A polyamide composition containing a styrene copolymer,
the content of the (C) styrene copolymer is 0.1% by mass or more and 7.0% by mass or less with respect to the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer,
the polyamide (A) contains an aliphatic polyamide (A1) and a semi-aromatic polyamide (A2) containing a diamine unit and a dicarboxylic acid unit,
the content of the (A2) semi-aromatic polyamide is 20% by mass or more and 50.0% by mass or less, based on the total mass of polyamides in the polyamide composition;
The polyamide composition , wherein the semi-aromatic polyamide (A2) contains 50 mol % or more of isophthalic acid units among all dicarboxylic acid units constituting the semi-aromatic polyamide (A2) . (A) polyamide,
(B) a phosphorus-based flame retardant, and
(C) Styrene copolymer
A polyamide composition comprising:
the content of the (C) styrene copolymer is 0.1% by mass or more and 7.0% by mass or less with respect to the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer,
the polyamide (A) contains an aliphatic polyamide (A1) and a semi-aromatic polyamide (A2) containing a diamine unit and a dicarboxylic acid unit,
the content of the (A2) semi-aromatic polyamide is 20% by mass or more and 50.0% by mass or less, based on the total mass of polyamides in the polyamide composition;
The polyamide composition, wherein the (B) phosphorus-based flame retardant contains at least one phosphinate selected from the group consisting of a phosphinate represented by the following general formula (1), a diphosphinate represented by the following general formula (2), and a condensate thereof:
(In general formula (1), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ⁿ¹¹⁺ is a metal ion with a valence of n11. M is an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n11 is 2 or 3. When n11 is 2 or 3, multiple R ¹¹ and R ¹² may be the same or different.
In general formula (2), R ²¹ and R ²² are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ²¹ M' is an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms. ^m21+ is a metal ion with a valence of m21. M' is an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n21 is an integer of 1 to 3. When n21 is 2 or 3, multiple R ²¹ , R ²² and Y ²¹ may be the same or different. m21 is 2 or 3. x is 1 or 2. When x is 2, multiple M's may be the same or different. n21, x, and m21 are integers that satisfy the relational expression 2 × n21 = m21 × x. (A) polyamide,
(B) a phosphorus-based flame retardant, and
(C) Styrene copolymer
A polyamide composition comprising:
the content of the (C) styrene copolymer is 0.1% by mass or more and 7.0% by mass or less with respect to the total mass of the (A) polyamide, the (B) phosphorus-based flame retardant, and the (C) styrene copolymer,
the polyamide (A) contains an aliphatic polyamide (A1) and a semi-aromatic polyamide (A2) containing a diamine unit and a dicarboxylic acid unit,
A polyamide composition, comprising: (A2) a semi-aromatic polyamide content of 20% by mass or more and 50.0% by mass or less, based on the total mass of polyamides in the polyamide composition; and containing carbon black. 4. The polyamide composition according to claim 2 , wherein the semi-aromatic polyamide (A2) contains 50 mol% or more of isophthalic acid units among all dicarboxylic acid units constituting the semi-aromatic polyamide (A2). The polyamide composition according to any one of claims 1 to 4 , wherein the semi-aromatic polyamide (A2) contains 75 mol% or more of isophthalic acid units in all dicarboxylic acid units constituting the semi-aromatic polyamide (A2). The polyamide composition according to any one of claims 1 to 5 , wherein the semi-aromatic polyamide (A2) contains 100 mol% of isophthalic acid units in all dicarboxylic acid units constituting the semi-aromatic polyamide (A2). The polyamide composition according to any one of claims 1 to 6 , wherein the styrene copolymer (C) contains acrylonitrile units and styrene units. The polyamide composition according to any one of claims 1 to 7, wherein the styrene copolymer (C) contains acrylonitrile units and styrene units, and the content of the acrylonitrile units is 30 mass% or more based on the total mass of the constituent units of the styrene copolymer ( C ). The polyamide composition according to any one of claims 1 and 3 to 8, wherein the (B) phosphorus-based flame retardant comprises at least one phosphinate selected from the group consisting of a phosphinate represented by the following general formula (1) , a diphosphinate represented by the following general formula (2 ), and a condensate thereof:
(In general formula (1), R ¹¹ and R ¹² each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ^{M n11+} represents an n11-valent metal ion. M represents an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n11 is 2 or 3. When n11 is 2 or 3, a plurality of R ¹¹ and R ¹² may be the same or different.
In general formula (2), ^R21 and ^R22 are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. ^Y21 is an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms. ^M'm21+ is an m21-valent metal ion. M' is an element belonging to Group 2 or Group 15 of the periodic table, a transition element, zinc, or aluminum. n21 is an integer of 1 to 3. When n21 is 2 or 3, multiple ^R21 , ^R22 , and ^Y21 may be the same or different. m21 is 2 or 3. x is 1 or 2. When x is 2, multiple M' may be the same or different. n21, x, and m21 are integers that satisfy the relationship 2 × n21 = m21 × x. 10. The polyamide composition according to claim 1, wherein the content of the phosphorus-based flame retardant (B) is 0.1 mass % or more and 30 mass % or less, based on the total mass of the polyamide (A), the phosphorus-based flame retardant ( B ), and the styrene copolymer (C). The polyamide composition according to any one of claims 1 to 10 , wherein the polyamide composition has a tan δ peak temperature of 90°C or higher. The polyamide composition according to any one of claims 1 to 11 , wherein the polyamide composition has a weight average molecular weight of 10,000 or more and 50,000 or less. The polyamide composition according to any one of claims 1 to 12 , further comprising at least one filler (D). A molded article obtained by molding the polyamide composition according to any one of claims 1 to 13 . 15. The molded article of claim 14 , comprising carbon black. A method for producing the polyamide composition according to any one of claims 1 to 13 , comprising melt-kneading raw material components containing the polyamide (A), the phosphorus-based flame retardant (B), and the styrene copolymer (C).