JP2024074668A - Polyamide resin composition and molded body - Google Patents

Abstract

[Problem] To provide a resin composition and a resin molded product that are excellent in mechanical properties and molded product appearance, and that do not break female threads even with high tightening torque when fastening parts using a self-tapping screw. [Solution] The polyamide resin composition contains 75 to 89 parts by mass of a crystalline aliphatic polyamide containing (A) at least one selected from the group consisting of (A-a) lactam units having 4 to 14 carbon atoms and (A-a') aminocarboxylic acid units having 4 to 14 carbon atoms, or (A-b) aliphatic dicarboxylic acid units and (A-c) aliphatic diamine units, and 11 to 25 parts by mass of (B) a semi-aromatic polyamide containing diamine units and dicarboxylic acid units, and further contains 100 to 200 parts by mass of (C) a fibrous reinforcing material, 0 to 2.5 parts by mass of (D) carbon black, and 0.05 to 0.5 parts by mass of (E) a crystallization retarder, relative to 100 parts by mass of the total amount of (A) and (B). [Selected Figure] None

Description

The present invention relates to a polyamide resin composition and a molded body.

Polyamide resins, such as polyamide 6 (hereinafter also referred to as "PA6") and polyamide 66 (hereinafter also referred to as "PA66"), have excellent mechanical properties as well as heat resistance, impact resistance, and chemical resistance, and are therefore widely used in automotive parts, electrical parts, electronic parts, household goods, etc.

In recent years, from the standpoint of economy and productivity, there has been a strong demand for polyamide resins with superior moldability and secondary processability. In particular, there is a particular demand in the market for polyamide resin materials that combine the tapping processability of screw fastening with the appearance of molded products. Furthermore, screws used in automobiles are constantly subject to vibration, so extremely high fastening reliability is required. Therefore, the challenge is to suppress the effects of variations in the tightening torque and manage fastening with a stable axial force.

Patent Document 1 discloses a composition that improves self-tapping properties and appearance while maintaining mechanical strength and heat resistance by blending glass fibers and an acid-modified elastomer with a polyamide resin consisting of a crystalline polyamide resin and an amorphous polyamide resin. However, in parts that are subject to vibration, such as the interior and exterior of an automobile, the composition is insufficient in terms of appearance and fastening properties of the screw at high torque.

Patent Document 2 discloses a composition in which a crystalline semi-aromatic polyamide is the main component and a fibrous reinforcing material is compounded. However, when molding is performed under high-cycle molding conditions in which the molding temperature is increased and the mold temperature is decreased in order to improve productivity, the composition is insufficient in terms of the appearance and dimensional stability of the molded product.

JP 2000-248172 A JP 2015-55538 A

Problem to be solved by the invention

In view of the problems with the conventional technology described above, the present invention provides a resin composition and a resin molded body that have excellent mechanical properties and molded product appearance, and in which the female thread (boss) is not destroyed even when the screw is tightened with a high tightening torque when fastening parts using a self-tapping screw.

Means for solving the problem

That is, the present invention is as follows.
[1]
(A) 75 to 89 parts by mass of a crystalline aliphatic polyamide containing at least one selected from the group consisting of (A-a) lactam units having from 4 to 14 carbon atoms and (A-a') aminocarboxylic acid units having from 4 to 14 carbon atoms, or (A-b) aliphatic dicarboxylic acid units and (A-c) aliphatic diamine units;
(B) 11 to 25 parts by mass of a semi-aromatic polyamide containing (Ba) a dicarboxylic acid unit and (B-b) a diamine unit,
For 100 parts by mass of the total amount of the crystalline aliphatic polyamide (A) and the semi-aromatic polyamide (B),
(C) 100 to 200 parts by mass of fibrous reinforcing material,
(D) 0 to 2.5 parts by mass of carbon black; and (E) 0.05 to 0.5 parts by mass of a crystallization retarder.
[2]
The polyamide resin composition according to [1], wherein a molded product obtained by molding a test piece having a thickness of 0.75 mm at a cylinder temperature of 280°C and a mold temperature of 90°C has a cold crystallization peak of 2.0 J/g or less when heated to 280°C at 20°C/min after being kept at 30°C for 3 minutes in differential scanning calorimetry (DSC).
[3]
The polyamide resin composition according to [1] or [2], wherein the aliphatic polyamide resin (A) is polyamide 6.
[4]
The polyamide resin composition according to any one of [1] to [3], wherein the semi-aromatic polyamide (B) contains 50 mol % or more of isophthalic acid units in all dicarboxylic acid units (Ba) constituting the semi-aromatic polyamide (B).
[5]
The polyamide resin composition according to any one of [1] to [4], wherein the semi-aromatic polyamide (B) contains 75 mol % or more of isophthalic acid units in all dicarboxylic acid units (Ba) constituting the semi-aromatic polyamide (B).
[6]
The polyamide resin composition according to any one of [1] to [5], wherein the semi-aromatic polyamide (B) contains 100 mol% of isophthalic acid units in all dicarboxylic acid units (Ba) constituting the semi-aromatic polyamide (B).
[7]
The polyamide resin composition according to any one of [1] to [6], wherein the weight average molecular weight Mw is 10,000≦Mw≦40,000.
[8]
A molded article having an insertion site for fastening a self-tapping screw, the molded article being obtained by molding the polyamide resin composition according to any one of [1] to [7].

The present invention provides a polyamide resin composition that, when molded into a molded article, has excellent flexural modulus, tensile strain, appearance, and self-tapping properties for screw fastening.

The following describes in detail the embodiment of the present invention (hereinafter, simply referred to as "the present embodiment"). The following 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 practiced by appropriately modifying it within the scope of its gist. In this specification, "polyamide" means a polymer having an amide (-NHCO-) group in the main chain.

<<Polyamide resin composition>>
The polyamide resin composition of the present invention comprises 75 to 89 parts by mass of a crystalline aliphatic polyamide comprising (A) at least one selected from the group consisting of (A-a) lactam units having from 4 to 14 carbon atoms and (A-a') aminocarboxylic acid units having from 4 to 14 carbon atoms, or (A-b) aliphatic dicarboxylic acid units and (A-c) aliphatic diamine units, and 11 to 25 parts by mass of (B) a semi-aromatic polyamide comprising (B-a) dicarboxylic acid units and (B-b) diamine units, and further comprises 100 to 200 parts by mass of (C) a fibrous reinforcing material, 0 to 2.5 parts by mass of (D) carbon black, and 0.05 to 0.5 parts by mass of (E) a crystallization retarder, relative to 100 parts by mass of the total amount of the crystalline aliphatic polyamide (A) and the semi-aromatic polyamide (B).

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

<(A) Crystalline Aliphatic Polyamide>
The crystalline aliphatic polyamide (A) contained in the polyamide resin composition of the present invention preferably contains (A-a) lactam units and/or (A-a') aminocarboxylic acid units, or (A-b) aliphatic dicarboxylic acid units and (Ac) aliphatic diamine units.

((A-a) Lactam Unit and/or (A-a') Aminocarboxylic Acid Unit)
The crystalline aliphatic polyamide (A) may contain a lactam unit (A-a) and/or an aminocarboxylic acid unit (A-a'). By containing such units, a polyamide having excellent toughness tends to be obtained. Here, the lactam constituting the lactam unit (A-a) and the aminocarboxylic acid constituting the aminocarboxylic acid unit (A-a') refer to lactam and aminocarboxylic acid capable of being polymerized (condensed), respectively.

The lactam constituting the lactam unit (A-a) and the aminocarboxylic acid constituting the aminocarboxylic acid unit (A-a') are lactams and aminocarboxylic acids having 4 to 14 carbon atoms, respectively, and lactams and aminocarboxylic acids having 6 to 12 carbon atoms are preferred.

Examples of lactams constituting the (Aa) lactam unit include, but are not limited to, butyrolactam, pivalolactam, ε-caprolactam, caprylolactam, enantholactam, undecanolactam, and laurolactam (dodecanolactam).
Among them, preferred lactams are ε-caprolactam, laurolactam, etc., and more preferred is ε-caprolactam. When the crystalline aliphatic polyamide (A) contains lactam units (Aa) derived from such lactams, a polyamide resin composition having superior toughness tends to be obtained.

The aminocarboxylic acid constituting the aminocarboxylic acid unit (Aa') is, but is not limited to, for example, ω-aminocarboxylic acids, which are compounds formed by ring-opening of lactam, and α,ω-amino acids.
The aminocarboxylic acid is preferably a linear or branched saturated aliphatic carboxylic acid having 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 paraaminomethylbenzoic acid.

The lactam constituting the lactam unit (A-a) and the amino carboxylic acid constituting the amino carboxylic acid unit (A-a') may each be used alone or in combination of two or more kinds.

((A-b) Aliphatic Dicarboxylic Acid Unit)
Examples of the aliphatic dicarboxylic acid constituting the aliphatic dicarboxylic acid unit (A-b) include, but are not limited to, linear or branched saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms, such as malonic acid, dimethylmalonic acid, succinic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylglutaric acid, 2,2-diethylsuccinic acid, 2,3-diethylglutaric acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosane dioic acid, and diglycolic acid.

The (A-b) aliphatic dicarboxylic acid unit is preferred because the polyamide resin composition tends to have better heat resistance, fluidity, toughness, low water absorption, and rigidity by including an aliphatic dicarboxylic acid having 6 or more carbon atoms. The aliphatic dicarboxylic acid constituting the (A-b) aliphatic dicarboxylic acid unit having 6 or more carbon atoms is not particularly limited, and examples thereof include adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosane dioic acid. Among these, adipic acid, sebacic acid, and dodecanedioic acid are preferred from the viewpoint of the heat resistance of the polyamide resin composition.
The aliphatic dicarboxylic acid constituting the aliphatic dicarboxylic acid unit (Ab) may be used alone or in combination of two or more kinds.

The crystalline aliphatic polyamide (A) may further contain units derived from trivalent or higher polycarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid, as necessary, within the scope of the present invention. The trivalent or higher polycarboxylic acids may be used alone or in combination of two or more.

((A-c) Aliphatic Diamine Unit)
The aliphatic diamine constituting the aliphatic diamine unit (Ac) may be linear or branched.
Examples of linear aliphatic diamines constituting the aliphatic diamine unit (A-c) include, but are not limited to, linear saturated aliphatic diamines having 2 to 20 carbon atoms, such as ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, and tridecamethylenediamine.

Examples of branched aliphatic diamines constituting the aliphatic diamine unit (A-c) having a substituent branched from the main chain include, but are not limited to, branched saturated aliphatic diamines having 3 to 20 carbon atoms, such as 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.
Among these, 2-methylpentamethylenediamine and 2-methyl-1,8-octanediamine are preferred, and 2-methylpentamethylenediamine is more preferred. By including such an aliphatic diamine unit (Ac), the polyamide resin composition tends to have better heat resistance, rigidity, etc.

The carbon number of the aliphatic diamine unit (Ac) is preferably 6 or more and 12 or less. When the carbon number is 6 or more, excellent heat resistance is obtained, and when the carbon number is 12 or less, excellent crystallinity and releasability are obtained. The carbon number of the diamine unit (Ac) is more preferably 6 or more and 10 or less.
The aliphatic diamine (Ac) may be used alone or in combination of two or more kinds.

The crystalline aliphatic polyamide (A) may further contain units derived from a polyvalent aliphatic amine having a valence of three or more, such as bishexamethylenetriamine, as necessary, to the extent that the object of the present invention is not impaired.

Specific examples of the crystalline aliphatic polyamide (A) used in the polyamide resin composition of the present invention include polyamide 6 (PA6). PA6 is considered to be a suitable material for automotive parts because it has excellent mechanical properties, appearance, moldability, and toughness.

In the present invention, the content of (A) crystalline aliphatic polyamide is 75.0 parts by mass or more and 89.0 parts by mass or less, preferably 78.0 parts by mass or more and 85 parts by mass or less, more preferably 80.0 parts by mass or more and 82.0 parts by mass or less, and even more preferably 80.0 parts by mass or more, based on the total amount of polyamide in the polyamide resin composition. By setting the content of (A) crystalline aliphatic polyamide within the above range, a polyamide resin composition having excellent mechanical properties, moldability, and self-tapping properties can be obtained.

<(B) Semi-aromatic polyamide>
(B) The semi-aromatic polyamide is a polyamide containing (Ba) dicarboxylic acid units and (Bb) diamine units.
The semi-aromatic polyamide (B) preferably contains 20 mol % or more and 80 mol % or less of aromatic constituent units, more preferably 30 mol % or more and 70 mol % or less of aromatic constituent units, and even more preferably 40 mol % or more and 60 mol % or less of aromatic constituent units, based on the total constituent units of the semi-aromatic polyamide (B). The term "aromatic constituent units" used herein means aromatic diamine units and aromatic dicarboxylic acid units.

((Ba) Dicarboxylic acid unit)
The dicarboxylic acid unit (B-a) may contain an aromatic dicarboxylic acid unit, an aliphatic dicarboxylic acid unit, or an alicyclic dicarboxylic acid unit, and is not particularly limited. Among them, the dicarboxylic acid unit (B-a) preferably contains 50 mol% or more and 100 mol% or less of isophthalic acid units, which are aromatic dicarboxylic acid units, based on the total mole number of dicarboxylic acids, more preferably contains 65 mol% or more and 100 mol% or less, even more preferably contains 70 mol% or more and 100 mol% or less, even more preferably contains 75 mol% or more and 100 mol% or less, even more preferably contains 80 mol% or more and 100 mol% or less, and particularly preferably contains 100 mol%.
When the ratio of isophthalic acid units in the dicarboxylic acid units (Ba-a) is equal to or more than the above lower limit, it tends to be possible to obtain a polyamide resin composition that simultaneously satisfies mechanical properties, particularly water absorption rigidity, hot rigidity, fluidity, surface appearance, etc.
The proportion of the isophthalic acid unit can be measured by nuclear magnetic resonance spectroscopy (NMR) or the like.

-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 ring such as a benzene ring, a naphthalene ring, etc. The aromatic ring of the aromatic dicarboxylic acid may be unsubstituted or may have a substituent.
The substituent is not particularly limited, but examples thereof include an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, an arylalkyl group having 7 to 10 carbon atoms, a halogen group such as a chloro group or a bromo group, a silyl group having 1 to 6 carbon atoms, and a sulfonic acid group and a salt thereof (such as a sodium salt).
Specific examples of the aromatic dicarboxylic acid include, but are not limited to, unsubstituted or predetermined substituent-substituted aromatic dicarboxylic acids having 8 to 20 carbon atoms, such as 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 kinds.

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

- Alicyclic dicarboxylic acid unit -
Examples of alicyclic dicarboxylic acids constituting the alicyclic dicarboxylic acid unit (hereinafter also referred to as "alicyclic dicarboxylic acid unit") include, but are not limited to, alicyclic dicarboxylic acids having an alicyclic structure with 3 to 10 carbon atoms, and alicyclic dicarboxylic acids having an alicyclic structure with 5 to 10 carbon atoms are preferred.
Examples of such alicyclic dicarboxylic acids include, but are not limited to, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,3-cyclopentanedicarboxylic acid, etc. Among these, 1,4-cyclohexanedicarboxylic acid is preferred.
The alicyclic dicarboxylic acid constituting the alicyclic dicarboxylic acid unit may be used alone or in combination of two or more kinds.

Examples of the alicyclic structure of the alicyclic dicarboxylic acid include, but are not limited to, a cycloalkane structure, a cycloalkene structure, a bicyclic alkane structure, a bicyclic alkene structure, a polycyclic compound structure, a spiro compound structure, and the like, each having 3 to 10 carbon atoms. The alicyclic structure of the alicyclic dicarboxylic acid may be unsubstituted or may have a substituent. Examples of the substituent include, but are not limited to, alkyl groups having 1 to 4 carbon atoms, such as 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.

The dicarboxylic acid units (Ba) 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.
By using such a dicarboxylic acid, the mechanical properties of the polyamide resin composition, in particular, water absorption rigidity, hot rigidity, fluidity, surface appearance, etc. tend to be more excellent.

In the present invention, the dicarboxylic acid constituting the dicarboxylic acid unit (Ba) is not limited to the compounds described above as the dicarboxylic acid, and may be a compound equivalent to the above dicarboxylic acid.
Here, the term "compound equivalent to a dicarboxylic acid" refers to a compound that can have a dicarboxylic acid structure similar to the dicarboxylic acid structure derived from the above dicarboxylic acid. Examples of such compounds include, but are not limited to, anhydrides and halides of dicarboxylic acids.

Furthermore, the semi-aromatic polyamide (B) may further contain units derived from a polyvalent carboxylic acid having three or more carboxylic acids, such as trimellitic acid, trimesic acid, and pyromellitic acid, as necessary.
The trivalent or higher polyvalent carboxylic acid may be used alone or in combination of two or more kinds.

((B-b) Diamine Unit)
The diamine unit (B-b) constituting the semi-aromatic polyamide (B) may contain an aromatic diamine acid unit, an aliphatic diamine unit, or an alicyclic diamine unit, and is not particularly limited. Among them, it is preferable to contain a diamine unit having 4 to 10 carbon atoms.
The total amount of diamine units having 4 to 10 carbon atoms is preferably 50 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and particularly preferably 100 mol%, relative to 100 mol% of all diamine units (B-b) constituting the semi-aromatic polyamide (B).
When the ratio of the diamine units having 4 to 10 carbon atoms in all diamine units (B-b) is equal to or more than the above lower limit, the polyamide resin composition tends to simultaneously satisfy mechanical properties, particularly water absorption rigidity, rigidity under high temperature use (hot rigidity), fluidity, surface appearance, etc.
The total amount of diamine units having 4 to 10 carbon atoms can be measured by nuclear magnetic resonance spectroscopy (NMR) or the like.

- Aliphatic diamine unit -
Examples of aliphatic diamines constituting the aliphatic diamine unit include, but are not limited to, linear saturated aliphatic diamines having 4 to 20 carbon atoms, such as ethylene diamine, propylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, and tridecamethylene diamine.

- 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, and 1,3-cyclopentanediamine.

- 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 ring, and examples thereof include metaxylylenediamine.

Among the (B-b) diamine units, preferably, they are aliphatic diamine units, more preferably, they are diamine units having a linear saturated aliphatic group having from 4 to 10 carbon atoms, even more preferably, they are diamine units having a linear saturated aliphatic group having from 6 to 10 carbon atoms, and even more preferably, they are hexamethylenediamine.
Use of such a diamine tends to result in a polyamide resin composition that is more excellent in mechanical properties, particularly rigidity upon water absorption, rigidity under high temperature use (rigidity when hot), fluidity, surface appearance, and the like.
The diamine may be used alone or in combination of two or more kinds.

The semi-aromatic polyamide (B) may further contain a polyvalent aliphatic amine having a valence of three or more, such as bishexamethylenetriamine, if necessary.
The trivalent or higher polyvalent aliphatic amines may be used alone or in combination of two or more kinds.

The semi-aromatic polyamide (B) used in the polyamide resin composition of the present invention is preferably polyamide 6I (polyhexamethylene isophthalamide), polyamide 9I, or polyamide 10I, with polyamide 6I being the most preferred. Polyamide 6I is highly compatible with crystalline aliphatic polyamides and tends to result in polyamide resin compositions with excellent mechanical properties, moldability, and self-tapping properties.

In the present invention, the content of the semi-aromatic polyamide (B) is preferably 11.0 parts by mass or more and 25.0 parts by mass or less, more preferably 15.0 parts by mass or more and 22.0 parts by mass or less, even more preferably 18.0 parts by mass or more and 20.0 parts by mass or less, and even more preferably 20.0 parts by mass or less, based on the total amount of polyamide in the polyamide resin composition. By setting the content of the semi-aromatic polyamide (B) to the above lower limit or more, the dimensional stability of the self-tap is good, the contact area with the screw is increased, and since the toughness of the crystalline aliphatic polyamide (A) is not impaired, it is possible to tighten the tap screw with a high tightening force. On the other hand, by setting the content of the semi-aromatic polyamide (B) to the above upper limit or less, it is possible to suppress the deterioration of the crystallinity and toughness of the polyamide resin composition and prevent crack destruction before the tightening screw spins idly.

(End-capping agent)
The ends of the polyamide used in the present invention may be capped with a known end-capping agent.
Such an end-capping agent can also be added as a molecular weight regulator when producing a polyamide from the above-mentioned dicarboxylic acid and diamine, and optionally a lactam and/or an aminocarboxylic acid.

Examples of the end-capping agent include, but are not limited to, monocarboxylic acids, monoamines, acid anhydrides such as phthalic anhydride, monoisocyanates, monoacid halides, monoesters, and monoalcohols.
Among these, monocarboxylic acids and monoamines are preferable. By capping the ends of the polyamide with an end-capping agent, the polyamide resin composition tends to have better thermal stability.
The end-capping agent may be used alone or in combination of two or more kinds.

Monocarboxylic acids that can be used as end-capping agents may be any that are reactive with amino groups that may be present at the ends of polyamides, and include, but are not limited to, aliphatic monocarboxylic acids such as 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; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; and aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid.
In particular, it is preferred that the ends of the aromatic polyamide (B) be blocked with acetic acid from the viewpoints of flowability, dimensional stability, and mechanical strength of the molded product.
The monocarboxylic acid may be used alone or in combination of two or more kinds.

The monoamine that can be used as the end-capping agent may be any monoamine that is reactive with a carboxyl group that may be present at the end of a polyamide, and includes, but is not limited to, aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; and aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine.
The monoamines may be used alone or in combination of two or more kinds.
Polyamide resin compositions containing polyamide end-capped with an end-capping agent tend to be excellent in flowability, and in the dimensional stability and mechanical strength of molded articles.

<Production method of polyamide>
When producing the polyamides ((A) crystalline aliphatic polyamide and (B) semi-aromatic polyamide) contained in the polyamide resin composition of this embodiment, it is preferable that the amount of dicarboxylic acid added and the amount of diamine added are approximately the same molar amount. Taking into consideration the amount of diamine that escapes to the outside of the reaction system during the polymerization reaction in the molar ratio, the molar amount of the total diamines relative to the molar amount of the total 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 one or more selected from the group consisting of lactams constituting lactam units (e.g., (A-a) lactam units having 4 to 14 carbon atoms) and aminocarboxylic acids constituting aminocarboxylic acid units (e.g., (A-a') aminocarboxylic acid units having 4 to 14 carbon atoms) to obtain a polymer.
(2) A step of polymerizing a combination of a dicarboxylic acid constituting a dicarboxylic acid unit and a diamine constituting a diamine unit (e.g., a combination of an aliphatic dicarboxylic acid unit (A-b) and an aliphatic diamine unit (A-c), or a combination of a dicarboxylic acid unit (B-a) and a diamine unit (B-b)) to obtain a polymer.

The method for producing polyamide preferably further includes, after the polymerization step, an increase step for increasing the degree of polymerization of the polyamide. If necessary, the method may include, after the polymerization step and the increase step, a sealing step for sealing the ends of the obtained polymer with a terminal sealing agent.

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

Among them, a specific method for producing polyamide is preferably a production method including a hot melt polymerization method. In addition, when producing polyamide by a hot melt polymerization method, it is preferable to maintain the molten state until the polymerization is completed. In order to maintain the molten state, it is necessary to produce the polyamide resin composition under polymerization conditions suitable for the composition. Examples of the polymerization conditions include the following conditions. 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 tank is reduced over 30 minutes or more until it becomes atmospheric pressure (gauge pressure is 0 kg/cm ² ).

In the method for producing a polyamide, the polymerization form is not particularly limited, and may be a batch type or a continuous type.
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 type reactor, a tumbler type reactor, and an extruder type reactor (such as a kneader).

Hereinafter, as a method for producing polyamide, a method for producing polyamide by a batch-type hot melt polymerization method will be specifically described, but the method for producing polyamide is not limited thereto.
First, an aqueous solution containing about 40% to 60% by weight of raw materials for polyamide (lactam and/or aminocarboxylic acid, dicarboxylic acid, diamine) is prepared. The aqueous solution is then concentrated to about 65% to 90% by weight 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 concentrated solution obtained is then transferred to an autoclave, and heating is continued until the pressure in the autoclave becomes about 1.2 MPa or more and 2.2 MPa or less (gauge pressure).
Next, in the autoclave, the pressure is maintained at about 1.2 MPa to 2.2 MPa (gauge pressure) while removing at least one of water and gas components. 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 necessary to effectively remove the by-produced 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.

(Polyamide polymer end)
The polymer ends of the polyamide used in the present invention are not particularly limited, but can be classified and defined as follows.
That is, 1) amino terminus, 2) carboxyl terminus, 3) terminus with a capping agent, and 4) other terminus.

1) The amino terminal is a polymer end having an amino group ( _-NH2 group) and originates from the diamine unit of the raw material.
2) The carboxyl terminal is a polymer terminal having a carboxyl group (—COOH group) and originates from the dicarboxylic acid used as the raw material.
3) The term "terminal end by a capping agent" refers to an end 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 not classified into the above-mentioned 1) to 3), and examples thereof include terminals generated by deammonia reaction of amino terminals and terminals generated by decarboxylation of carboxyl terminals.

<(A) Characteristics of Aliphatic Polyamide>
Specifically, the molecular weight of the crystalline aliphatic polyamide (A) can be measured by the method described in the examples below.

As an index of the molecular weight of the (A) aliphatic polyamide, Mw(A) (weight average molecular weight) can be used. The Mw(A) (weight average molecular weight) of the (A) crystalline aliphatic polyamide is preferably 10,000 or more, more preferably 15,000 or more, even more preferably 17,000 or more, even more preferably 20,000 or more, preferably 50,000 or less, more preferably 40,000 or less, even more preferably 34,000 or less, and even more preferably 30,000 or less. By having Mw(A) (weight average molecular weight) in the above range, a polyamide resin composition excellent in flowability, appearance of molded products, dimensional stability of the tap part, mechanical properties, etc. can be obtained. In addition, a polyamide resin composition containing a component represented by an inorganic filler has excellent surface appearance. The Mw(A) (weight average molecular weight) can be measured using GPC (gel permeation chromatography).

The molecular weight distribution of (A) crystalline aliphatic polyamide is indicated by Mw(A) (weight average molecular weight)/Mn(A) (number average molecular weight). (A) crystalline aliphatic polyamide's Mw(A) (weight average molecular weight)/Mn(A) (number average molecular weight) is preferably 1.8 or more, more preferably 1.9 or more, and preferably 2.2 or less, more preferably 2.1 or less. The lower limit of the molecular weight distribution is 1.0. By having Mw(A) (weight average molecular weight)/Mn(A) (number average molecular weight) in the above range, a polyamide resin composition having excellent fluidity, etc. can be obtained.

In addition, polyamide resin compositions containing components such as inorganic fillers have excellent surface appearance.

Methods for controlling the Mw(A) (weight average molecular weight)/Mn(A) (number average molecular weight) of the (A) crystalline aliphatic polyamide within the above range include, for example, adding a known polycondensation catalyst such as phosphoric acid or sodium hypophosphite as an additive during the thermal melt polymerization of the polyamide, and controlling the polymerization conditions such as heating conditions and reduced pressure conditions. In the present invention, the Mw(A) (weight average molecular weight)/Mn(A) (number average molecular weight) of the (A) crystalline aliphatic polyamide can be measured and calculated using the Mw(A) (weight average molecular weight) and Mn(A) (number average molecular weight) obtained using GPC (gel permeation chromatography).

<(B) Characteristics of Semi-aromatic Polyamide>
The molecular weight, melting point Tm2, crystallization enthalpy ΔH, and tan δ peak temperature of the (B) semi-aromatic polyamide can be specifically measured by the methods shown below.

As an index of the molecular weight of the (B) semi-aromatic polyamide, Mw(B) (weight average molecular weight) can be used. The Mw(B) (weight average molecular weight) of the (B) polyamide is preferably 10,000 or more, more preferably 13,000 or more, even more preferably 15,000 or more, even more preferably 18,000 or more, particularly preferably 19,000 or more, preferably 50,000 or less, more preferably 40,000 or less, even more preferably 25,000 or less, even more preferably 22,000 or less, and particularly preferably 21,000 or less.

When Mw(B) (weight average molecular weight) is within the above range, a polyamide resin composition having excellent flowability, dimensional stability of molded products, mechanical strength, etc. can be obtained. In addition, polyamide resin compositions containing components such as inorganic fillers have excellent surface appearance. Note that Mw(B) (weight average molecular weight) can be measured using GPC (gel permeation chromatography).

The molecular weight distribution of the semi-aromatic polyamide (B) is indicated by Mw(B) (weight average molecular weight)/Mn(B) (number average molecular weight).
The Mw(B) (weight average molecular weight)/Mn(B) (number average molecular weight) of the semi-aromatic polyamide (B) is preferably 2.4 or less, more preferably 1.7 or more and 2.4 or less, even more preferably 1.8 or more and 2.3 or less, even more preferably 1.9 or more and 2.2 or less, and most preferably 1.9 or more and 2.1 or less. The lower limit of Mw(B) (weight average molecular weight)/Mn(B) (number average molecular weight) is 1.0. By having Mw(B) (weight average molecular weight)/Mn(B) (number average molecular weight) in the above range, a polyamide resin composition having excellent flowability and the like can be obtained. In addition, a polyamide resin composition containing a component represented by an inorganic filler has excellent surface appearance.

As a method for controlling the Mw(B) (weight average molecular weight)/Mn(B) (number average molecular weight) of the semi-aromatic polyamide (B) within the above range, for example, a method of adding a known polycondensation catalyst such as phosphoric acid or sodium hypophosphite as an additive during the thermal melt polymerization of polyamide can be mentioned. It is also important to control the polymerization conditions such as heating conditions and decompression conditions, and complete the polycondensation reaction as low as possible and in as short a time as possible. In particular, if the semi-aromatic polyamide (B) is an amorphous polyamide, it is desirable because it does not have a melting point and therefore the reaction temperature can be lowered.
When the molecular structure of a polyamide contains an aromatic compound unit, the molecular weight distribution (Mw/Mn) tends to increase with increasing molecular weight. A high molecular weight distribution indicates a high proportion of polyamide molecules having a three-dimensional molecular structure, and the three-dimensional molecular structure tends to progress further during high-temperature processing, resulting in a decrease in fluidity and a deterioration in the surface appearance of a polyamide resin composition containing a component represented by an inorganic filler.

In the present invention, the Mw(B) (weight average molecular weight)/Mn(B) (number average molecular weight) of the semi-aromatic polyamide (B) can be calculated using the Mw(B) (weight average molecular weight) and Mn(B) (number average molecular weight) obtained using GPC (gel permeation chromatography).

(B) The crystallization enthalpy ΔH of the semi-aromatic polyamide is, from the viewpoints of fluidity, dimensional stability of molded articles, mechanical strength, etc., preferably 15 J/g or less, more preferably 10 J/g or less, even more preferably 5 J/g or less, still more preferably 2 J/g or less, and particularly preferably 0 J/g.
As a method for controlling the crystallization enthalpy ΔH of the semi-aromatic polyamide (B) within the above range, the aromatic monomer ratio to the dicarboxylic acid unit (Ba) can be increased. It is important that the dicarboxylic acid unit (Ba) contains 75 mol % or more of isophthalic acid, and it is more preferable that the dicarboxylic acid unit (Ba) contains 100 mol % of isophthalic acid.
(B) An example of an apparatus for measuring the crystallization enthalpy ΔH of a semi-aromatic polyamide is Diamond-DSC manufactured by PERKIN-ELMER.

(B) The amount of amino terminals in the semi-aromatic polyamide is preferably 5 to 100 μequivalents/g, more preferably 10 to 90 μequivalents/g, even more preferably 20 to 80 μequivalents/g, even more preferably 30 to 70 μequivalents/g, and even more preferably 40 to 60 μequivalents/g, per 1 g of polyamide. By having the amount of amino terminals in the above range, a composition that is excellent in resistance to discoloration due to heat and light can be obtained. The amount of amino terminals can be measured by neutralization titration.

(B) The amount of carboxyl terminals in the semi-aromatic polyamide is preferably 50 to 300 μequivalents/g, more preferably 100 to 280 μequivalents/g, even more preferably 150 to 260 μequivalents/g, even more preferably 180 to 250 μequivalents/g, and even more preferably 200 to 240 μequivalents/g, per 1 g of polyamide. By having the amount of carboxyl terminals in the above range, a polyamide resin composition having excellent fluidity and the like can be obtained. In addition, a polyamide resin composition containing a component such as an inorganic filler has excellent surface appearance. The amount of carboxyl terminals can be measured by neutralization titration.

The total amount of amino terminals and carboxyl terminals is preferably 150 to 350 μequivalents/g, more preferably 160 to 300 μequivalents/g, even more preferably 170 to 280 μequivalents/g, even more preferably 180 to 270 μequivalents/g, and even more preferably 190 to 260 μequivalents/g, per gram of polyamide. By having the total amount of amino terminals and carboxyl terminals in the above range, a polyamide resin composition with excellent fluidity and the like can be obtained. In addition, when a polyamide resin composition containing a component such as an inorganic filler is used, the surface appearance is excellent.

<(C) Fibrous Reinforcement>
The polyamide resin composition of the present embodiment further contains (C) a fibrous reinforcing material in addition to the above-mentioned (A) and (B) components. As the (C) fibrous reinforcing material, any material that can improve the mechanical strength of the polyamide resin composition and the durability of the molded product can be used.
Contains chemical materials.

(C) Fibrous reinforcing materials include, but are not limited to, glass fibers, carbon fibers, calcium silicate fibers, potassium titanate fibers, aluminum borate fibers, aramid fibers, cellulose nanofibers, and the like. Among these, glass fibers, carbon fibers, or potassium titanate fibers having circular and noncircular cross sections are preferred from the viewpoint of increasing the strength and rigidity of the resulting molded product. Furthermore, glass fibers or carbon fibers having circular and noncircular cross sections are more preferred. These (C) fibrous reinforcing materials may be used alone or in combination of two or more kinds.

From the viewpoint of imparting excellent mechanical properties to the polyamide resin composition, the glass fibers and carbon fibers preferably have a number average fiber diameter of 3 μm or more and 30 μm or less, a weight average fiber length of 100 μm or more and 750 μm or less, and an aspect ratio of the weight average fiber length to the number average fiber diameter (the value obtained by dividing the weight average fiber length by the number average fiber diameter) of 10 or more and 100 or less.

From the viewpoint of imparting excellent mechanical properties to the polyamide resin composition, calcium silicate fibers are preferably those having a number average fiber diameter of 3 μm or more and 30 μm or less, a weight average fiber length of 10 μm or more and 500 μm or less, and an aspect ratio of 3 or more and 100 or less.

Here, the number average fiber diameter and weight average fiber length in this specification can be determined as follows.

That is, the polyamide resin composition is placed in an electric furnace, and the organic matter contained therein is incinerated. From the residue, for example, 100 or more pieces of (C) fibrous reinforcing material are arbitrarily selected, observed with a SEM, and the fiber diameters of these are measured. The number average fiber diameter can be obtained by calculating the average value.

Fiber length can also be measured using a 1000x SEM photograph, and the weight average fiber length can be calculated using a specific formula (if the length of n fibers is measured, weight average fiber length = Σ(I=1→n) (fiber length of nth fiber)2/Σ(I=1→n) (fiber length of nth fiber)).

The content of the (C) fibrous reinforcing material in the polyamide resin composition of the present invention is 100.0 parts by mass or more and 200.0 parts by mass or less, preferably 110.0 parts by mass or more and 175.0 parts by mass or less, and more preferably 120.0 parts by mass or more and 150.0 parts by mass or less, when the total of the (A) crystalline aliphatic polyamide and the (B) semi-aromatic polyamide is taken as 100 parts by mass. If the content of the (C) fibrous reinforcing material exceeds the above upper limit, the toughness of the polyamide resin composition tends to decrease and the self-tapping properties tend to decrease. If the content of the (C) fibrous reinforcing material is below the above range, the polyamide resin composition tends not to exhibit strength. Therefore, by setting the content of the (C) fibrous reinforcing material within the above range, a polyamide resin composition having excellent mechanical properties, moldability, and self-tapping properties can be obtained.

<(D) Carbon Black>
The polyamide resin composition of the present invention may further contain (D) carbon black. The carbon black is not particularly limited, but preferably has an average primary particle size in the range of 10 nm to 40 nm, more preferably 10 to 30 nm, and particularly preferably 10 to 20 nm. From the viewpoint of dispersibility in the composition, it is preferably 10 nm or more, and from the viewpoint of strength, rigidity, and expression of the thin wall part of the molded piece, it is preferably 40 nm or less. In addition, carbon black having a specific surface area in the range of 50 to 300 m ² /g (BET adsorption method) and an oil absorption amount (measured using dibutyl phthalate) in the range of 50 mL/100 g to 150 mL/100 g can be preferably used.

In addition, when (D) carbon black is used, the amount of carbon black added may be 0 parts by mass or more, preferably 0.04 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.4 parts by mass or more, preferably 1.00 parts by mass or less, more preferably 0.8 parts by mass or less, and even more preferably 0.7 parts by mass or less, when the total of (A) crystalline aliphatic polyamide resin, (B) semi-aromatic polyamide, and (C) fibrous reinforcing material is 100 parts by mass. In addition, the amount of carbon black added is 0 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.25 parts by mass or more, even more preferably 1 part by mass or more, preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.75 parts by mass or less, when the total of (A) crystalline aliphatic polyamide resin and (B) semi-aromatic polyamide is 100 parts by mass. By setting the content of (D) carbon black in the above range, it tends to function efficiently as a crystal nucleating agent and increase the crystallinity of the boss part. This results in a polyamide resin composition with excellent mechanical properties, moldability, and self-tapping properties.

<(E) Crystallization Retardant>
The polyamide resin composition of the present invention further contains (E) a crystallization retarder in order to further improve the appearance and mechanical strength of the molded product. The crystallization retarder is a substance that has the effect of lowering the crystallization starting point of the polyamide resin by being mixed with the polyamide resin. The crystallization retarder (E) is not particularly limited, but includes azine dyes, phthalocyanine dyes, lithium chloride, etc. Among them, azine dyes or phthalocyanine dyes are preferred. As the azine dye, nigrosine is preferred, and as the phthalocyanine dye, copper phthalocyanine dye is preferred.

The content of the crystallization retarder (E) is preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.04 parts by mass or more, and preferably 0.2 parts by mass or less, more preferably 0.08 parts by mass or less, and even more preferably 0.06 parts by mass or less, when the total of the crystalline aliphatic polyamide resin (A), the semi-aromatic polyamide (B), and the glass fiber (C) is 100 parts by mass. The content of the crystallization retarder (E) is preferably 0.05 parts by mass or more, more preferably 0.075 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.2 parts by mass or less, and even more preferably 0.15 parts by mass or less, when the total of the crystalline aliphatic polyamide resin (A) and the semi-aromatic polyamide (B) is 100 parts by mass. (E) If the content of the crystallization retarder exceeds the above range, the crystallinity and toughness decrease, cracks tend to occur easily, and the uniformity of the crystallization decreases, which tends to lead to a decrease in the appearance of the molded product and the strength of the tapping part. (E) By setting the content of the crystallization retarder within the above range, uniform crystallization is induced, the dimensions tend to be stable, and a polyamide resin composition with excellent mechanical properties, moldability, and self-tapping properties can be obtained.

<Other additives>
The polyamide resin composition may contain other additives commonly used in polyamides, provided that the purpose of the present embodiment is not impaired. Examples of the other additives include antioxidants, fibrillating agents, lubricants, fluorescent bleaching agents, plasticizers, UV absorbers, antistatic agents, flow improvers, reinforcing agents, spreading agents, nucleating agents, rubbers, reinforcing agents, flame retardants, and other polymers. The content of the other additives in the polyamide resin composition of the present embodiment may be appropriately determined by a person skilled in the art depending on the purpose.

<Method of producing polyamide resin composition>
The method for producing the polyamide resin composition of the present invention is not particularly limited as long as it is a method of mixing (A) a crystalline aliphatic polyamide, (B) a semi-aromatic polyamide, (C) a fibrous reinforcing material, (D) carbon black, and (E) a crystallization retarder.

Examples of a method for mixing the above components (A), (B), (D), and (E) include the following method (1) or (2).
(1) The above components (A), (B), (D) and (E) are mixed using a Henschel mixer or the like, and then fed into a melt kneader for kneading.
(2) A method in which the above-mentioned components (A), (B), (D), and (E) 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 (D), and the mixture is fed to a melt kneader and kneaded, and then, optionally, component (C) is blended in through a side feeder.

The components constituting the polyamide resin composition may be fed to the melt kneader by feeding all of the components to the same feed port at once, or by feeding each component through a different feed port.

The melt-kneading temperature is preferably about 1° C. to 100° C. higher than the melting point of the crystalline aliphatic polyamide (A), and more preferably about 20° C. to 70° C. higher than the melting point of the crystalline aliphatic polyamide (A).
The shear rate in the kneader is preferably about 100 sec or more. The average residence time during kneading is preferably about 0.5 to 5 minutes.
The melt-kneading apparatus may be any known apparatus, and preferably used are, for example, a single-screw or twin-screw extruder, a Banbury mixer, a melt-kneader (mixing roll, etc.), etc.
The blending amount of each component when producing the polyamide resin composition of the present embodiment is the same as the content of each component in the polyamide resin composition described above.

<Physical Properties of Polyamide Resin Composition>
As an index of the molecular weight of the polyamide resin composition, Mw (weight average molecular weight) can be used. The Mw (weight average molecular weight) of the polyamide resin composition is preferably 10,000 or more, preferably 17,000 or more, more preferably 20,000 or more, even more preferably 25,000 or more, even more preferably 27,000 or more, most preferably 29,000 or more, preferably 40,000 or less, preferably 37,000 or less, more preferably 35,000 or less, even more preferably 34,000 or less, even more preferably 33,000 or less, and most preferably 32,000 or less. By having Mw (weight average molecular weight) in the above range, a polyamide resin composition having excellent mechanical properties, moldability, and self-tapping properties can be obtained.
As a method for controlling the Mw of the polyamide composition within the above range, for example, (A) a crystalline aliphatic polyamide and (B) a semi-aromatic polyamide having Mw within the above range may be used.
The weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC) as described in the following examples.

The total content of (A) crystalline aliphatic polyamide and (B) semi-aromatic polyamide having a number average molecular weight Mn of 500 to 2000 is preferably 0.5% by mass or more and less than 2.5% by mass, more preferably 0.8% by mass or more and less than 2.5% by mass, even more preferably 1.0% by mass or more and less than 2.5% by mass, still more preferably 1.2% by mass or more and less than 2.5% by mass, and most preferably 1.4% by mass or more and less than 2.5% by mass. By having a content of 500 to 2000 having a number average molecular weight Mn of 0.5% by mass or more, the polyamide composition has excellent flowability and tends to have excellent surface appearance when containing a component represented by an inorganic filler. In addition, by having a content of less than 2.5% by mass, gas generation during molding tends to be suppressed.

As a method for controlling the total content of polyamides having a number average molecular weight Mn of 500 or more and 2000 or less within the above range, a method of adjusting the molecular weight of the semi-aromatic polyamide (B) can be mentioned, and the Mw (weight average molecular weight) is preferably 10,000 to 25,000.
The total content of (A) aliphatic polyamide and (B) semi-aromatic polyamide having a number average molecular weight Mn of 500 or more and 2000 or less relative to the total amount of polyamide is determined by using GPC from an elution curve under the measurement conditions in the examples described later.
In the case where the composition containing (A) crystalline aliphatic polyamide and (B) semi-aromatic polyamide contains other components that are soluble in the solvent that dissolves the polyamide during GPC measurement, the other components are extracted and removed using a solvent that is insoluble in the polyamide but soluble in the other components, and then the GPC measurement is performed. Also, inorganic fillers that are insoluble in the solvent that dissolves the polyamide resin are dissolved in the solvent that dissolves the polyamide resin composition, and then filtered to remove the insoluble matter, and then the GPC measurement is performed.

The molecular weight distribution of the polyamide resin composition of the present invention is indicated by Mw (weight average molecular weight)/Mn (number average molecular weight).
The Mw (weight average molecular weight)/Mn (number average molecular weight) of the polyamide resin composition of the present invention is preferably 2.4 or less, more preferably 1.7 to 2.3, even more preferably 1.8 to 2.2, and even more preferably 1.9 to 2.1. The lower limit of the molecular weight distribution is 1.0. By having the Mw (weight average molecular weight)/Mn (number average molecular weight) in the above range, a polyamide resin composition having excellent flowability tends to be obtained. In addition, a polyamide resin composition containing a component represented by an inorganic filler tends to have excellent self-tapping properties, surface appearance, etc.

As a method for controlling the Mw (weight average molecular weight)/Mn (number average molecular weight) of the polyamide resin composition within the above range, it is important to set the Mw (weight average molecular weight)/Mn (number average molecular weight) of the semi-aromatic polyamide (B) within the above range.
When the molecular structure of a polyamide resin composition contains an aromatic compound unit, the molecular weight distribution (Mw/Mn) tends to increase with increasing molecular weight. A high molecular weight distribution indicates a high proportion of polyamide molecules having a three-dimensional molecular structure, and the three-dimensional molecular structure tends to progress further during high-temperature processing, reducing the fluidity, and the surface appearance of a polyamide resin composition containing a component such as an inorganic filler deteriorates.

In the present invention, the Mw (weight average molecular weight)/Mn (number average molecular weight) of the polyamide resin composition can be calculated using the Mw (weight average molecular weight) and Mn (number average molecular weight) obtained using GPC (gel permeation chromatography) as described in the following examples.

In the polyamide resin composition of the present invention, a test piece having a thickness of 0.75 mm is molded at a cylinder temperature of 280°C and a mold temperature of 90°C. The molded product is then heated to 280°C at 20.0°C/min after being kept at 30°C for 3 minutes in differential scanning calorimetry (DSC). The cold crystallization peak is preferably 2.0 J/g or less, more preferably 1.0 J/g or less, even more preferably 0.5 J/g or less, and even more preferably 0.2 J/g or less. If the polyamide resin composition of the present invention exceeds the above range, poor crystallization occurs in the mold during injection molding, and the boss tends to crack and break before the screw spins during self-tapping. By setting the above range, a polyamide resin composition having excellent mechanical properties, moldability, and self-tapping properties can be obtained.

<Molded body>
The molded article of the present embodiment is produced by molding the polyamide resin composition.
In addition, the molded product of this embodiment has a high surface gloss value. The surface gloss value of the molded product of this embodiment is 60 or more, preferably 70 or more, and more preferably 80 or more. Since the surface gloss value of the molded product is equal to or more than the above lower limit, the molded product obtained can be suitably used as various parts for automobiles, electrical and electronic products, industrial materials, industrial materials, daily necessities and household products, etc. In addition, since the self-tapping property of screw fastening is excellent, it is suitable for molded products having a self-tapping screw insertion part.

The manufacturing method of the molded product is not particularly limited, and any known molding method can be used. Known molding methods include, but are not limited to, commonly known plastic molding methods such as press molding, injection molding, gas-assisted injection molding, welding molding, extrusion molding, blow molding, film molding, blow molding, multi-layer molding, and melt spinning.

<Applications>
The molded product obtained by molding the polyamide resin composition obtained by the manufacturing method of this embodiment is obtained from the above polyamide resin composition, and therefore has excellent mechanical properties, molded product appearance, and self-tapping screw fastening. Therefore, this molded product can be suitably used as various parts for automobile parts, electric and electronic parts, home appliance parts, OA (Office Automation) equipment parts, mobile equipment parts, industrial equipment parts, daily necessities and household goods, and also for extrusion applications. Among them, the molded product is suitably used as automobile parts, electric and electronic parts, home appliance parts, OA equipment parts, or mobile equipment parts. Furthermore, it is suitable for molded products having a self-tapping screw insertion part.

Automobile parts include, but are not limited to, intake system parts, cooling system parts, fuel system parts, interior parts, exterior parts, electrical parts, etc.

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

The components of the polyamide resin composition used in this example and comparative examples are explained below.

<Components>
[(A) Crystalline Aliphatic Polyamide]
A-1: Polyamide 6 (manufactured by Ube Industries, trade name: "SF1013A", Mw(A) = 31500, Mw(A)/Mn(A) = 2.2)

[(B) Semi-aromatic polyamide]
B-1: Polyamide 6I
B-2: Polyamide 6I/6T (manufactured by EMS Co., Ltd., product name: "G21", Mw(B) = 27,000, Mw(B)/Mn(B) = 2.4)
B-3: Polyamide MXD6 (Toyobo Nylon manufactured by Toyobo Co., Ltd., product name "T-600", Mw(B): 45000, Mw(B)/Mw(B): 2.2)

[(C) Fibrous reinforcing material]
C-1: Glass fiber (GF) (manufactured by Nippon Electric Glass, product name: "ECS03T275H", average fiber diameter 10 μmφ, cut length 3 mm)
C-2: Wollastonite (manufactured by NYCO, "400WC" (product name), number average particle diameter 8.0 μm, number average particle length 35 μm)

[(D) Carbon Black]
D-1: Carbon black (CB) (manufactured by Mitsubishi Chemical Corporation, product name: "#52B")

[(E) Crystallization Retardant]
E-1: Nigrosine dye (TH807, manufactured by Orient Chemical Co., Ltd.)

<Production of polyamide>
Each method for producing the semi-aromatic polyamide B-1 will be described in detail below. The semi-aromatic polyamide B-1 obtained by the following production method was dried in a nitrogen stream to adjust the moisture content to about 0.2% by mass, and then used as a raw material for the polyamide resin composition in the examples and comparative examples described later.

Synthesis Example 1 Synthesis of Semi-aromatic Polyamide B-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, 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 an equimolar 50 mass % homogeneous aqueous solution of raw material monomers. Next, the solution was concentrated by gradually removing steam to a solution concentration of 70 mass % while stirring at a temperature of about 110 ° C. to 150 ° C. Next, the internal temperature was 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 steam and maintaining the pressure at 1.8 MPa until the internal temperature reached 245 ° C. Next, the pressure was reduced over 30 minutes. Next, the inside of the autoclave was maintained at a reduced pressure of 650 torr (86.66 kPa) for 10 minutes using a vacuum device. At this time, 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 semi-aromatic polyamide B-1 (polyamide 6I).
The resulting semi-aromatic polyamide B-1 (polyamide 6I) had a content of isophthalic acid units in dicarboxylic acid units of 100 mol % and Mw(B)=20,000.

<Method of measuring physical properties>
First, the pellets of the polyamide resin compositions obtained in the Examples and Comparative Examples were dried in a nitrogen stream to reduce the moisture content in the polyamide resin compositions to 500 ppm or less. Next, the pellets of each polyamide resin composition with the adjusted moisture content were used to carry out various physical properties and various evaluations using the following methods.

[Physical Property 1] Molecular weight of polyamide resin composition (Molecular weight of polyamide resin composition (Mn, Mw/Mn)
The Mw (weight average molecular weight)/Mn (number average molecular weight) of the polyamide resin compositions obtained in the Examples and Comparative Examples was calculated using the Mw and Mn measured by GPC (gel permeation chromatography, Tosoh Corporation, HLC-8020, hexafluoroisopropanol solvent, converted into a PMMA (polymethyl methacrylate) standard sample (Polymer Laboratory Co., Ltd.)). TSK-GEL GMHHR-M and G1000HHR were used as GPC columns.

[Physical property 2] Cold crystallization degree of polyamide resin composition Using an injection molding machine [NEX50III-5EG: manufactured by Nissei Plastics Co., Ltd.], the cooling time was set to 25 seconds, the screw rotation speed was set to 200 rpm, the mold temperature was set to 90 ° C., the cylinder temperature was set to 280 ° C., and the filling time was set to the range of 1.6 ± 0.1 seconds. The injection pressure and injection speed were appropriately adjusted to produce a strip molded piece (12.7 cm × 1.27 cm, thickness 0.75 mm). The center of the strip molded piece thus produced was cut with nippers by 8 g, and the crystallization degree was calculated from the endothermic peak when the temperature was increased at 20 ° C. / min after keeping it at 30 ° C. for 3 minutes by differential scanning calorimetry (DSC).

<Evaluation method>
[Evaluation 1] Appearance of molded body Using an injection molding machine [NEX50III-5EG: manufactured by Nissei Plastic Industrial Co., Ltd.], the cooling time was set to 25 seconds, the screw rotation speed was set to 200 rpm, the mold temperature was set to 90 ° C, the cylinder temperature was set to 280 ° C, and the filling time was set to the range of 1.6 ± 0.1 seconds. The injection pressure and injection speed were appropriately adjusted to produce a flat plate molded piece (6 cm × 9 cm, thickness 3 mm). The central part of the flat plate molded piece thus produced was measured for 60 degree gloss according to JIS-K7150 using a gloss meter (HORIBA IG320). It was judged that the larger the measured value, the better the surface appearance.

[Evaluation 2] Tensile strain Using an injection molding machine [NEX50III-5EG: manufactured by Nissei Plastic Industrial Co., Ltd.], the resin temperature was set to 290 ° C., the mold temperature was set to 80 ° C., and the injection + pressure holding time was set to 25 seconds, and the cooling time was set to 15 seconds. A multipurpose test piece of ISO type A was molded under the molding conditions. Using the obtained multipurpose test piece, the tensile breaking strain was measured under the condition of a tensile speed of 5 mm / min according to ISO 527. The obtained breaking strain was taken as the tensile strain. The higher the tensile strain, the better it was judged to be.

[Evaluation 3] Flexural modulus Using an injection molding machine [NEX50III-5EG: manufactured by Nissei Plastic Industrial Co., Ltd.], a resin temperature was set to 290°C, a mold temperature was set to 80°C, and an injection + pressure holding time was set to 25 seconds, and a cooling time was set to 15 seconds. A multipurpose test piece of ISO type A was molded under the molding conditions. The flexural modulus was measured according to ISO178 using the obtained multipurpose test piece. The higher the flexural modulus, the better the product was judged to be.

[Evaluation 4] Amount of change in inner diameter of self-tapping molded body A molded body was injection molded with a boss having a wall thickness of 5.6 mm and an inner diameter of 3.4 mmφ attached to a circular flat plate having a diameter of 140 mm and a thickness of 3 mm. The inner diameter of the actual molded piece was measured in 0.1 mm increments using a pin gauge. The difference between the inner diameter and the actual inner diameter, that is, the amount of shrinkage, was judged to be excellent when it was in the range of 0.06 to 0.15 mm, preferably 0.07 to 0.13 mm, and more preferably 0.08 to 0.10 mm.

[Evaluation 5] Destructive torque strength and destruction form by self-tapping screw A molded body with a boss having a wall thickness of 5.6 mm and an inner diameter of 3.4 mm was injection molded on a circular flat plate having a diameter of 140 mm and a thickness of 3 mm, and a self-tapping screw (Osaka Tamashii pan head tapping screw M4 x 10, screw nominal diameter 4 mm, nominal length 10 mm, hole shape is cross hole) was inserted into the boss mouth using a digital torque meter HDP-50 (manufactured by Hios), and the maximum torque until the inside of the resin was destroyed and the screw idly rotated was evaluated as the tightening torque. A higher tightening torque was judged to be superior. In addition, the destruction behavior during tightening was evaluated according to the following criteria.

(Evaluation criteria)
OK: The screw spun freely. NG: The boss broke due to a crack before the screw spun freely.

<Method of producing polyamide resin composition>
[Example 1] Production of resin composition Using a TEM35mm twin screw extruder (set temperature: 280°C, screw rotation speed: 300 rpm) manufactured by Toshiba Machine Co., Ltd., a pre-blended mixture of polyamide (A-1), (B-1), (D-1), and (E-1) was fed from a top feed port provided at the most upstream part of the extruder, (C-1) was fed from a side feed port on the downstream side of the extruder (in a state where the resin fed from the top feed port was fully molten), and the molten mixture extruded from the die head was cooled in a strand shape and pelletized to obtain polyamide resin composition pellets. The blending amounts were as shown in Table 1.
The pellets of the polyamide resin composition thus obtained were used to produce molded articles by the above-mentioned method, and various physical properties were evaluated. The evaluation results are shown in Table 1.

[Examples 2 to 6 and Comparative Examples 1 to 6] Production of resin compositions Pellets of a resin composition were obtained using the same method as in Example 1, except that the ingredients and amounts were as shown in Table 1. Molded articles were produced using the pellets of the resin composition obtained by the above-mentioned method, and various physical properties were evaluated. The evaluation results are shown in Table 1 below.

As can be seen from Table 1, the polyamide resin composition containing (A) crystalline aliphatic polyamide, (B) semi-aromatic polyamide, (C) fibrous filler, (D) carbon black, and (E) crystallization retarder within the specified numerical ranges provided molded articles with good appearance, mechanical properties, boss dimensional stability, and tapping properties, and the boss did not crack or break during tapping.

In comparing PA-a1 to PA-a3, which have different contents of aromatic polyamide (B) relative to the total amount of polyamide in the polyamide resin composition, it was found that the appearance and flexural modulus of the molded article tended to be more excellent as the content of crystalline aliphatic polyamide (B) increased. On the other hand, the tensile strain and the change in inner diameter of the self-tap tended to be more excellent as the content of aromatic polyamide (B) decreased (the content of polyamide A-1 increased). Furthermore, it was found that tapping strength tended to increase when the content of aromatic polyamide (B) was in the range of 18.0-20.0 parts by mass.

In comparing polyamide resin compositions PA-a2 and PA-a6, which have different contents of the (E) crystallization retarder component, it was found that the appearance of the molded product tended to improve as the content of the (E) crystallization retarder component increased. On the other hand, the inner diameter change of the self-tap tended to be better as the content of the (E) crystallization retarder component decreased.

(B) In comparing PA-a2 and PA-a4, which are different types of aromatic polyamide, the one containing polyamide 6I tended to have better flexural modulus, self-tap inner diameter change, and tapping strength.

(B) In comparing PA-a2 and PA-b4, which are different types of aromatic polyamide, the one containing polyamide 6I tended to have better appearance of the molded body, tensile strain, change in inner diameter of the self-tap, fracture behavior of the self-tap, and tapping strength.

(C) In comparing PA-a2 and PA-a5, which have different amounts of fibrous reinforcing material, it was found that the flexural modulus, change in inner diameter of the self-tap, fracture behavior of the self-tap, and tapping strength tended to be better as the amount of fibrous reinforcing material (C) increased.

The polyamide resin composition of the present invention has excellent mechanical properties, molded product appearance, and self-tapping properties for screw fastening, and has industrial applicability, such as being suitable for use as a molding material for various parts, including those for automobiles, electrical and electronic products, industrial materials, industrial materials, and daily necessities and household products, and is particularly suitable as a molding material for parts with self-tapping screw insertion parts.

Claims (8)

(A) 75 to 89 parts by mass of a crystalline aliphatic polyamide containing at least one selected from the group consisting of (A-a) lactam units having from 4 to 14 carbon atoms and (A-a') aminocarboxylic acid units having from 4 to 14 carbon atoms, or (A-b) aliphatic dicarboxylic acid units and (A-c) aliphatic diamine units;
(B) 11 to 25 parts by mass of a semi-aromatic polyamide containing (Ba) a dicarboxylic acid unit and (B-b) a diamine unit,
For 100 parts by mass of the total amount of the crystalline aliphatic polyamide (A) and the semi-aromatic polyamide (B),
(C) 100 to 200 parts by mass of fibrous reinforcing material,
(D) 0 to 2.5 parts by mass of carbon black; and (E) 0.05 to 0.5 parts by mass of a crystallization retarder. The polyamide resin composition according to claim 1, in which a molded body obtained by molding a test piece having a thickness of 0.75 mm at a cylinder temperature of 280°C and a mold temperature of 90°C has a cold crystallization peak of 2.0 J/g or less when heated to 280°C at 20°C/min after being kept at 30°C for 3 minutes in differential scanning calorimetry (DSC). The polyamide resin composition according to claim 1 or 2, wherein the aliphatic polyamide resin (A) is polyamide 6. The polyamide resin composition according to claim 1 or 2, wherein the (B) semi-aromatic polyamide contains 50 mol % or more of isophthalic acid units among all dicarboxylic acid units (B-a) constituting the (B) semi-aromatic polyamide. The polyamide resin composition according to claim 1 or 2, wherein the (B) semi-aromatic polyamide contains 75 mol % or more of isophthalic acid units among all dicarboxylic acid units (B-a) constituting the (B) semi-aromatic polyamide. The polyamide resin composition according to claim 1 or 2, wherein the (B) semi-aromatic polyamide contains 100 mol % isophthalic acid units out of all dicarboxylic acid units (B-a) constituting the (B) semi-aromatic polyamide. The polyamide resin composition according to claim 1 or 2, wherein the weight average molecular weight Mw is 10,000≦Mw≦40,000. 3. A molded article having an insertion site for fastening a self-tapping screw, which is obtained by molding the polyamide resin composition according to claim 1 or 2.