JP7809564B2 - Polyamide resin composition and molded article thereof - Google Patents

Description

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

Polyamide resin compositions have traditionally been known as molding materials. They are known to produce molded articles with excellent mechanical strength and heat resistance.

For example, Patent Document 1 discloses a semi-aromatic polyamide resin composition containing a semi-aromatic polyamide (A) having a melting point of 290°C or higher and 340°C or lower, a semi-aromatic polyamide (B) having a heat of fusion of 0 J/g or higher and 5 J/g or lower, an olefin polymer (C) containing a functional group structural unit containing a heteroatom, and a fibrous filler (D). According to Patent Document 1, the semi-aromatic polyamide resin composition is capable of producing molded articles with good impact resistance, fuel barrier properties, and injection moldability.

Furthermore, Patent Document 2 discloses a polyamide resin composition containing a polyamide (I) having a terminal amino group content ([NH ₂ ]) of 10 μequivalents/g or more and less than 60 μequivalents/g, and a modified resin (II) modified with an unsaturated compound having a carboxyl group and/or an acid anhydride group, which comprises dicarboxylic acid units containing 50 to 100 mol% of terephthalic acid units and diamine units containing 60 to 100 mol% of aliphatic diamine units having 6 to 18 carbon atoms. According to Patent Document 2, the polyamide resin composition is capable of improving the impact resistance, heat resistance, etc., of molded articles as well as chemical resistance.

International Publication No. 2015/011935 JP 2008-179753 A

Polyamide resin compositions can be used in automotive parts, such as the housing of a water pump that pumps coolant to cool the engine. Water pumps sometimes use antifreeze, such as long-life coolant (LLC), as the coolant. There is a demand for polyamide resin compositions that can suppress the decrease in elongation (tensile elongation at break) of molded bodies after exposure to LLC, so that molded bodies are less likely to break when removed from the member to which they are attached.

In response to this issue, the inventors conducted research and found that while adding a modified resin modified with a compound containing a functional group structural unit to a polyamide resin composition could suppress the decrease in elongation to some extent, depending on the amount added, it could significantly reduce the tensile strength of the molded article after immersion in LLC. To prevent the molded article from becoming brittle and breaking after exposure to LLC, it is necessary to suppress the decrease in tensile strength after immersion in LLC. For these reasons, there is a growing demand for polyamide resin compositions that can simultaneously suppress the decrease in tensile strength after immersion in LLC and the decrease in tensile elongation at break after immersion in LLC (enhancing LLC resistance).

According to the present inventors, the polyamide resin composition described in Patent Document 2 was able to suppress the decrease in tensile strength of a molded article after immersion in LLC, but was unable to suppress the decrease in tensile elongation at break of the molded article after immersion in LLC.

The present invention was made in consideration of the above circumstances, and aims to provide a polyamide resin composition and molded articles thereof that, by adding a modified resin, can suppress a decrease in tensile elongation at break after the molded article is immersed in LLC, while also suppressing a decrease in tensile strength.

The present invention relates to the following polyamide resin composition and molded article thereof.

The polyamide resin composition of the present invention comprises a polyamide resin and a modified resin (C) modified with a compound containing a functional group structural unit, the modified resin being present in an amount of 0.1 to 20 parts by mass relative to 100 parts by mass of the polyamide resin. The polyamide resin comprises a polyamide resin (A) having a melting point (Tm ₁ ) of 300°C or higher as measured by a differential scanning calorimeter (DSC), the amount of which is 70 to 95 parts by mass relative to 100 parts by mass of the polyamide resin, and a polyamide resin (B) having a melting point that is not substantially measurable by a differential scanning calorimeter (DSC), the amount of which is 5 to 30 parts by mass relative to 100 parts by mass of the polyamide resin. The crystallization rate, expressed as the difference between the melting point (Tm) of the polyamide resin composition and the crystallization temperature (Tc) of the polyamide resin composition, both measured by a differential scanning calorimeter (DSC), is 31 to 40°C.

The molded article of the present invention is obtained by molding the above-mentioned polyamide resin composition.

The present invention provides a polyamide resin composition and molded articles thereof that, by adding a modified resin, can suppress a decrease in tensile elongation at break after the molded article is immersed in LLC, while also suppressing a decrease in tensile strength.

Embodiments of the present invention are described in detail below. Note that the present invention is not limited to the following embodiments.

In this specification and claims, the notation "to" means a range that includes not only intermediate values but also boundary values. For example, when written as "A to B," it means a range that includes "A," "B," and "the intermediate value between A and B."

1. Polyamide Resin Composition The polyamide resin composition of the present invention comprises a polyamide resin containing a polyamide resin (A) and a polyamide resin (B), and a modified resin (C), and has a crystallization rate, expressed as the difference between the melting point and the crystallization temperature of the polyamide resin composition, of 31 to 40°C.

The inventors have discovered that when the polyamide resin composition of the present invention combines polyamide resin (A), polyamide resin (B), and modified resin (C) in a specified content ratio and the crystallization rate is 31 to 40°C, it is possible to suppress both the decrease in tensile strength and the decrease in tensile elongation at break after immersion in LLC (increasing LLC resistance) compared to when polyamide resin (A) and polyamide resin (B) are used alone, as in the polyamide resin composition described in Patent Document 2. The reason for this is unclear, but is thought to be as follows.

Highly crystalline polyamide resin (A) forms crystals in the molded product, inhibiting the penetration of LLC and preventing a decrease in tensile strength after immersion in LLC. It is believed that adding a predetermined amount of amorphous or low-crystalline polyamide resin (B) to this polyamide resin (A) can appropriately adjust the crystallinity of the polyamide resin. According to the inventors' findings, combining a polyamide resin containing polyamide resin (A) and polyamide resin (B) with a modifying resin (C) can prevent a decrease in elongation after immersion in LLC. This is believed to be because the appropriate degree of crystallinity of the polyamide resin makes it easier for the added modifying resin (C) to be uniformly dispersed among the crystallized polyamide resin.

However, the inventors have found that adding modified resin (C) can sometimes result in a decrease in tensile strength after immersion in LLC, depending on the amount added. This is thought to be because the functional group structural units of modified resin (C) present in the gaps between the crystals make it easier for LLC to penetrate, making the polyamide resin more susceptible to degradation. Therefore, the inventors have conducted further research and found that by adjusting the crystallization rate of a polyamide resin composition containing modified resin (C) to fall within the above range, the decrease in tensile strength after immersion in LLC can be suppressed more effectively than with polyamide resin compositions containing the same amount of modified resin (C) but with a crystallization rate outside the above range.

When forming a molded body, the time required to mold the polyamide resin composition is limited to improve production efficiency, and the time during which the polyamide resin composition reaches a temperature near the crystallization temperature is short. In this case, if the crystallization temperature is 31°C or higher, more crystals can be formed within this short time. Therefore, even if the modified resin (C) is included, excessive penetration of LLC into the molded body can be sufficiently suppressed, and a decrease in tensile strength due to degradation of the polyamide resin by LLC can be suppressed. Meanwhile, according to the inventors' new findings, imparting a minimal amount of LLC into the molded body can impart flexibility to the molded body. This is thought to compensate for the decrease in elongation due to hydrolysis of the polyamide resin that occurs during LLC immersion. From this perspective, in this embodiment, the crystallization temperature is set to 40°C or lower, suppressing excessive crystal formation during molding and allowing the molded body to have slight LLC penetration.

For these reasons, the addition of a modified resin to the polyamide resin composition of the present invention can suppress a decrease in tensile strength while also suppressing a decrease in tensile elongation at break after the molded product is immersed in LLC.

1-1. Polyamide Resin In the present invention, the polyamide resin includes a polyamide resin (A) and a polyamide resin (B) whose melting point is substantially not measurable by differential scanning calorimetry (DSC).

(Polyamide resin (A))
The polyamide resin (A) forms crystals in the molded body, suppressing excessive penetration of LLC and thereby suppressing a decrease in tensile strength after immersion in LLC. The polyamide resin (A) is a polyamide resin having a melting point (Tm ₁ ) of 300°C or higher as measured by differential scanning calorimetry (DSC). The melting point of the polyamide resin (A) is preferably 300°C or higher and 340°C or lower, and more preferably 300°C or higher and 330°C or lower. When the melting point of the polyamide resin (A) is 300°C or higher, the heat resistance and mechanical strength of the polyamide resin composition can be improved. Furthermore, when the melting point is 340°C or lower, the melting point of the polyamide resin composition does not increase excessively, and thermal decomposition of the polymer and various carbonizing agents during melt polymerization and melt molding can be further suppressed.

The melting point (Tm ₁ ) of the polyamide resin (A) can be measured, for example, using a differential scanning calorimeter (DSC220C model, manufactured by Seiko Instruments Inc.).

Specifically, about 5 mg of polyamide resin (A) is sealed in a measuring aluminum pan and heated from room temperature to 350°C at 10°C/min. To completely melt the resin, it is held at 350°C for 3 minutes and then cooled to 30°C at 10°C/min. After leaving it at 30°C for 5 minutes, it is heated a second time to 350°C at 10°C/min. The temperature (°C) of the endothermic peak during this second heating is taken as the melting point ( _Tm1 ) of the polyamide resin.

The melting point (Tm ₁ ) of the polyamide resin (A) can be adjusted to fall within the above range by adjusting the composition of the polyamide resin (A). For example, the melting point (Tm ₁ ) can be increased by increasing the content of the component unit derived from terephthalic acid, which will be described later.

The heat of fusion (ΔH) of polyamide resin (A) measured by differential scanning calorimetry (DSC) is preferably greater than 5 J/g. The heat of fusion is an indicator of the crystallinity of a resin, with a larger heat of fusion indicating higher crystallinity. When the heat of fusion (ΔH) of polyamide resin (A) exceeds 5 J/g, the crystallinity is increased, thereby suppressing a decrease in the tensile strength of the resulting molded article after immersion in LLC.

The heat of fusion (ΔH) is a value calculated from the area of the endothermic peak during melting during the first heating process in accordance with JIS K7122:2012.

The polyamide resin (A) is not particularly limited as long as it has a melting point of 300°C or higher, but it can be, for example, a polyamide containing component units (a1) derived from a dicarboxylic acid, such as structural units derived from terephthalic acid, and component units (a2) derived from a diamine. Below, we will explain the case where the polyamide resin (A) contains component units (a1) derived from a dicarboxylic acid and component units (a2) derived from a diamine.

(Component unit (a1) derived from dicarboxylic acid)
The component units (a1) derived from a dicarboxylic acid component contain, relative to the total number of moles of the component units (a1) derived from a dicarboxylic acid, 20 to 100 mol % of component units derived from terephthalic acid and 0 to 80 mol % of at least one of component units derived from an aromatic dicarboxylic acid other than terephthalic acid and component units derived from an aliphatic dicarboxylic acid having 4 to 20 carbon atoms.

Examples of terephthalic acid include terephthalic acid, terephthalic acid esters, etc.

Examples of aromatic carboxylic acids other than terephthalic acid include isophthalic acid, 2-methylterephthalic acid, and naphthalenedicarboxylic acid. Of these, isophthalic acid is preferred.

The aliphatic dicarboxylic acid has 4 to 20 carbon atoms, preferably 6 to 12 carbon atoms. Examples of such aliphatic dicarboxylic acids include adipic acid, azelaic acid, and sebacic acid. Of these, adipic acid and sebacic acid are preferred.

The component units derived from aromatic dicarboxylic acids other than terephthalic acid and the component units derived from aliphatic dicarboxylic acids having 4 to 20 carbon atoms are contained in an amount of 0 to 80 mol % relative to the total number of moles of component units (a1), at least one of which is derived from a dicarboxylic acid. From the viewpoint of further suppressing the decrease in tensile strength after immersion in LLC and further suppressing the decrease in tensile elongation at break after immersion in LLC, it is preferable that the component units derived from aromatic dicarboxylic acids other than terephthalic acid account for 20 to 80 mol % of these.

The dicarboxylic acid-derived component units (a1) preferably contain 20 to 100 mol% of component units derived from terephthalic acid and 0 to 80% of component units derived from aromatic dicarboxylic acids other than terephthalic acid, relative to the total moles of the dicarboxylic acid-derived component units (a1). It is more preferable that it contains 20 to 80 mol% of component units derived from terephthalic acid and 20 to 80% of component units derived from aromatic dicarboxylic acids other than terephthalic acid. It is even more preferable that it contains 55 to 85 mol% of component units derived from terephthalic acid and 15 to 45 mol% of component units derived from aromatic dicarboxylic acids other than terephthalic acid. When the content of component units derived from terephthalic acid is above a certain level, the melting point of the polyamide resin (A) tends to be 300°C or higher, thereby improving the heat resistance of the resulting molded article. It also further improves the crystallinity of the polyamide resin (A), thereby further suppressing a decrease in tensile strength after immersion in LLC.

When the dicarboxylic acid-derived component units (a1) include component units derived from an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, the content thereof is preferably 20 to 60 mol % relative to the total number of moles of the dicarboxylic acid-derived component units (a1).

The dicarboxylic acid-derived component unit (a1) may further include component units derived from other dicarboxylic acids in addition to those mentioned above, as long as the effects of the present invention are not impaired. For example, the dicarboxylic acid-derived component unit (a1) may further include component units derived from an alicyclic dicarboxylic acid. Examples of alicyclic dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid. The content of the component units derived from other dicarboxylic acids may be, for example, 0 to 20 mol %, 0 to 10 mol %, or 0.1 to 10 mol %, relative to the total number of moles of the dicarboxylic acid-derived component unit (a1).

(Diamine-derived component unit (a2))
The diamine-derived component unit (a2) includes at least one of a component unit (a2-1) derived from an aliphatic diamine having 4 to 15 carbon atoms and a component unit (a2-2) derived from an alicyclic diamine having 4 to 20 carbon atoms.

The component units (a2-1) derived from an aliphatic diamine having 4 to 15 carbon atoms preferably include at least one of component units derived from a linear alkylenediamine having 4 to 15 carbon atoms and component units derived from a branched alkylenediamine having 4 to 15 carbon atoms (alkylenediamine having a side chain).

Examples of linear alkylenediamines include 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane. Of these, 1,6-diaminohexane, 1,9-nonanediamine, and 1,10-diaminodecane are preferred. Only one type of linear alkylenediamine may be included, or two or more types may be included.

The content of component units derived from linear alkylenediamines having 4 to 15 carbon atoms is preferably 40 to 100 mol %, and more preferably 80 to 100 mol %, relative to the total number of moles of component units (a2-1) derived from aliphatic diamines having 4 to 15 carbon atoms. A content of component units derived from linear alkylenediamines above a certain level can increase the crystallinity of the polyamide resin and further increase the tensile strength after immersion in LLC.

Examples of branched alkylenediamines include 2-methyl-1,5-diaminopentane, 2-methyl-1,6-diaminohexane, 2-methyl-1,7-diaminoheptane, 2-methyl-1,8-diaminooctane, 2-methyl-1,9-diaminononane, 2-methyl-1,10-diaminodecane, and 2-methyl-1,11-diaminoundecane. Of these, 2-methyl-1,5-diaminopentane and 2-methyl-1,8-diaminooctane are preferred. Only one type of branched alkylenediamine may be included, or two or more types may be included.

The content of component units derived from branched alkylenediamine may be 0 to 60 mol %, and preferably 0 to 20 mol %, relative to the total number of moles of component units (a2-1) derived from aliphatic diamines having 4 to 15 carbon atoms. When this content is 0 mol % or more, excessive increases in crystallinity of the polyamide resin can be suppressed, further suppressing a decrease in tensile break elongation after immersion in LLC. Furthermore, when this content is 60 mol % or less, excessive decreases in crystallinity can be suppressed, further suppressing a decrease in tensile strength after immersion in LLC.

The content of component units (a2-1) derived from an aliphatic diamine having 4 to 15 carbon atoms is preferably 50 to 100 mol %, and more preferably 60 to 100 mol %, relative to the total number of moles of component units (a2) derived from diamine.

The diamine-derived component unit (a2) may include a component unit (a2-2) derived from an alicyclic diamine having 4 to 20 carbon atoms. Examples of alicyclic diamines having 4 to 20 carbon atoms include 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 2,5-bisaminomethylnorbornane, and 2,6-bisaminomethylnorbornane.

The content of component units (a2-2) derived from an alicyclic diamine having 4 to 20 carbon atoms is preferably 0 to 60 mol %, and more preferably 0 to 40 mol %, relative to the total number of moles of component units (a2) derived from diamine.

The diamine-derived component units (a2) may further include component units derived from other diamines other than the component units (a2-1) derived from aliphatic diamines having 4 to 15 carbon atoms and the component units (a2-2) derived from alicyclic diamines having 4 to 20 carbon atoms, provided that the effects of the present invention are not impaired. Examples of other diamines include aromatic diamines such as metaxylylenediamine. The content of the component units derived from other diamines can be 0 to 10 mol % based on the total number of moles of the diamine-derived component units (a2).

The constituent units of polyamide resin (A) and their ratios can be calculated from the charge ratios used when preparing polyamide resin (A), or can be measured by NMR spectroscopy.

In the case of ^1H -NMR measurement, for example, a nuclear magnetic resonance spectrometer (ECX400 manufactured by JEOL Ltd.) is used, the solvent is deuterated ortho-dichlorobenzene, the sample concentration is 20 mg/0.6 mL, the measurement temperature is 120°C, the observation nucleus is ^1H (400 MHz), the sequence is single pulse, the pulse width is 5.12 μsec (45° pulse), the repetition time is 7.0 seconds, and the number of accumulations is 500 or more. The reference chemical shift is set to 0 ppm for hydrogen in tetramethylsilane, but similar results can also be obtained by setting the peak derived from the residual hydrogen in deuterated ortho-dichlorobenzene at 7.10 ppm as the reference value for the chemical shift. Peaks such as ^1H derived from functional group-containing compounds can be assigned by conventional methods.

In the case of ^13C -NMR measurement, for example, a nuclear magnetic resonance spectrometer (ECP500 manufactured by JEOL Ltd.) is used as the measurement device, a mixed solvent of ortho-dichlorobenzene/heavy benzene (80/20% by volume) is used as the solvent, the measurement temperature is 120°C, the observation nucleus is ^13C (125 MHz), single pulse proton decoupling, 45° pulse, repetition time is 5.5 seconds, the number of accumulations is 10,000 or more, and the reference value of the chemical shift is 27.50 ppm. Assignment of various signals is performed based on a conventional method, and quantification can be performed based on the accumulated value of the signal intensity.

Specific examples of polyamide resin (A) include polyamide resins in which the dicarboxylic acid-derived component units (a1) are component units derived from terephthalic acid and component units derived from isophthalic acid, and the diamine-derived component units (a2) are component units derived from 1,6-diaminohexane.

The intrinsic viscosity [η] of polyamide resin (A), measured in concentrated sulfuric acid at 25°C, is preferably 0.70 to 1.60 dl/g, and more preferably 0.80 to 1.20 dl/g. When the intrinsic viscosity [η] of polyamide resin (A) is 0.70 dl/g or higher, the decrease in tensile strength after immersion in LLC can be sufficiently suppressed. When the intrinsic viscosity [η] is 1.60 dl/g or lower, the fluidity of the polyamide resin composition during molding is less likely to be impaired.

The intrinsic viscosity [η] of the polyamide resin (A) can be measured as follows: 0.5 g of the semi-aromatic polyamide resin (A) is dissolved in 50 ml of a 96.5% sulfuric acid solution to prepare a sample solution. The flow time of the obtained solution at 25°C ± 0.05°C is measured using an Ubbelohde viscometer, and the intrinsic viscosity [η] is calculated based on the following formula:
[η]=ηSP/(C*(1+0.205ηSP))
[η]: Intrinsic viscosity (dl/g)
ηSP: specific viscosity C: sample concentration (g/dl)
t: number of seconds for the sample solution to flow down (seconds)
t ₀ : Number of seconds (seconds) for blank sulfuric acid to flow
ηSP=(t−t ₀ )/t ₀

Polyamide resin (A) can be produced by methods similar to those used to produce known polyamide resins. For example, it can be produced by polycondensing a dicarboxylic acid and a diamine in a homogeneous solution. Specifically, as described in WO 03/085029, a dicarboxylic acid and a diamine are heated in the presence of a catalyst to obtain a low-order condensate, and then a melt of this low-order condensate is subjected to shear stress to cause polycondensation.

(Polyamide resin (B))
The melting point of polyamide resin (B) is substantially not measurable by differential scanning calorimetry (DSC). In this specification, "substantially not measurable" means that, in the measurement of the melting point using a differential scanning calorimetry (DSC), an endothermic peak due to crystalline melting is not substantially observed during the second heating (from room temperature to 330°C). "Substantially not measurable" means that the heat of fusion (ΔH) of polyamide resin (B) measured by differential scanning calorimetry (DSC) is 0 J/g or more and 5 J/g or less. Because polyamide resin (B) has low crystallinity, using it together with polyamide resin (A) can prevent the crystallinity of the polyamide resin from increasing too much, thereby further suppressing the decrease in tensile elongation at break after immersion in LLC. The heat of fusion can be measured by the method described for polyamide resin (A).

As mentioned above, the heat of fusion is an indicator of the crystallinity of a resin, and the smaller the heat of fusion, the lower the crystallinity. Therefore, it is preferable that the heat of fusion of polyamide resin (B) is 0 J/g. It is also preferable that polyamide resin (B) is an amorphous resin.

The heat of fusion (ΔH) of the polyamide resin (B) can be adjusted to fall within the above range by adjusting the composition of the polyamide resin (B). For example, the heat of fusion can be reduced by increasing the content of the component units derived from isophthalic acid, which will be described later.

The polyamide resin (B) is not particularly limited as long as it is a polyamide resin having a heat of fusion (ΔH) of 0 J/g or more and 5 J/g or less, but it can be, for example, a polyamide containing component units (b1) derived from a dicarboxylic acid and component units (b2) derived from a diamine. Below, we will explain the case where the polyamide resin (B) contains component units (b1) derived from a dicarboxylic acid and component units (b2) derived from a diamine.

(Component unit (b1) derived from dicarboxylic acid)
The dicarboxylic acid-derived component unit (b1) includes an isophthalic acid-derived component unit. By including an isophthalic acid-derived component unit, the crystallinity of the polyamide resin (B) can be further reduced.

The content of component units derived from isophthalic acid is preferably 40 to 100 mol %, and more preferably 50 to 100 mol %, relative to the total number of moles (b1) of components derived from dicarboxylic acids in polyamide resin (B). When the content of isophthalic acid component units is 40 mol % or more, the crystallinity of polyamide resin (B) can be further reduced.

The dicarboxylic acid-derived component units (b1) may further contain component units derived from other dicarboxylic acids other than the isophthalic acid-derived component units, as long as the effects of the present invention are not impaired. Examples of other dicarboxylic acids include aromatic dicarboxylic acids other than isophthalic acid, such as terephthalic acid, 2-methylterephthalic acid, and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. The aliphatic dicarboxylic acids and alicyclic dicarboxylic acids may be the same as the aliphatic dicarboxylic acids and alicyclic dicarboxylic acids described above, respectively. Of these, aromatic dicarboxylic acids other than isophthalic acid are preferred, and terephthalic acid is more preferred.

The content of component units derived from other dicarboxylic acids can be, for example, 0 to 60 mol %, or can also be 0 to 45 mol %, relative to the total number of moles of component units (b1) derived from dicarboxylic acids.

When the dicarboxylic acid-derived component units (b1) further contain component units derived from terephthalic acid, the molar ratio of the isophthalic acid-derived component units to the terephthalic acid-derived component units (isophthalic acid-derived component units/terephthalic acid-derived component units) is preferably 55/45 to 95/5, more preferably 60/40 to 80/20, and even more preferably 60/40 to 70/30. When the molar ratio is within the above range, the crystallinity of the polyamide resin (B) can be further reduced, thereby further suppressing the decrease in the tensile elongation at break of the resulting molded article after immersion in LLC.

(Component unit (b2) derived from diamine)
The diamine-derived component units (b2) include component units derived from aliphatic diamines having 4 to 15 carbon atoms.

Examples of aliphatic diamines having 4 to 15 carbon atoms include those described for polyamide resin (A). Of these, the aliphatic diamine is preferably 1,6-diaminohexane.

The content of component units derived from aliphatic diamine is preferably 50 to 100 mol %, and more preferably 60 to 100 mol %, based on the total number of moles of component units (b2) derived from diamine.

The diamine-derived component units (b2) may further contain component units derived from other diamines in addition to the aliphatic diamine-derived component units, as long as the effects of the present invention are not impaired. Examples of components derived from other diamines include alicyclic diamines and aromatic diamines. Examples of alicyclic diamines and aromatic diamines include those similar to those described for polyamide resin (A). The content of the other diamine-derived component units can be, for example, 0 to 10 mol % relative to the total number of moles of diamine-derived component units (b2).

The constituent units and their ratios in polyamide resin (B) can be calculated from the charge ratios used when preparing polyamide resin (B), or can be measured by NMR. For NMR, the same method as described for polyamide resin (A) can be used.

Specific examples of polyamide resin (B) include a polycondensate of isophthalic acid/terephthalic acid/1,6-diaminohexane/bis(3-methyl-4-aminocyclohexyl)methane, a polycondensate of isophthalic acid/terephthalic acid/1,6-diaminohexane, and a polycondensate of isophthalic acid/2,2,4-trimethyl-1,6-diaminohexane/2,4,4-trimethyl-1,6-diaminohexane. Of these, a polycondensate of isophthalic acid/terephthalic acid/1,6-diaminohexane is preferred. Only one type of polyamide resin (B) may be used, or two or more types may be used.

The intrinsic viscosity [η] of polyamide resin (B), measured in concentrated sulfuric acid at 25°C, is preferably 0.60 to 1.60 dl/g, and more preferably 0.60 to 1.20 dl/g. When the intrinsic viscosity [η] of polyamide resin (B) is 0.60 dl/g or higher, the decrease in tensile strength after immersion in LLC can be sufficiently suppressed. When the intrinsic viscosity [η] is 1.60 dl/g or lower, the fluidity of the polyamide resin composition during molding is less likely to be impaired.

Polyamide resin (B) can be produced by the same method as described for polyamide resin (A).

1-2. Modified resin (C)
The modified resin (C) is modified with a compound containing a functional group structural unit. That is, the modified resin (C) can be obtained by subjecting an unmodified resin to a modification reaction using a compound containing a functional group structural unit.

Examples of the resin before modification include olefin copolymers, styrene copolymers, etc. Of these, olefin copolymers are preferred.

Examples of olefin copolymers include olefin polymers such as ethylene-α-olefin copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-ethyl acrylate copolymer, as well as polyethylene, polypropylene, and polybutadiene. Of these, ethylene-α-olefin copolymers are preferred.

Examples of α-olefins other than ethylene that constitute the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. Among these, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene are preferred. These α-olefins can be used alone or in combination of two or more. The content of component units derived from α-olefins in the ethylene-α-olefin copolymer is from 0.5 mol% to 30 mol%, and preferably from 1 mol% to 20 mol%.

Examples of styrene copolymers include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene/butylene-styrene copolymer (SEBS), and styrene-ethylene/propylene-styrene copolymer (SEPS). Of these, styrene-ethylene/butylene-styrene copolymer (SEBS) is preferred.

Examples of the functional group structural unit include functional groups containing heteroatoms. Examples of functional groups containing heteroatoms include carboxylic acid groups (including carboxylic acid anhydride groups), ester groups, ether groups, aldehyde groups, and ketone groups. Of these, carboxylic acid groups (including carboxylic acid anhydride groups) are preferred.

Examples of compounds containing a carboxylic acid group include α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and phthalic acid. Examples of compounds containing a carboxylic acid anhydride group include dicarboxylic acid anhydrides having an α,β-unsaturated bond, such as maleic anhydride, itaconic anhydride, and phthalic anhydride. Of these, maleic anhydride is preferred.

The content (modification amount) of functional group structural units in modified resin (C) is preferably 0.3 to 5.0 mass% relative to the total mass of modified resin (C), and more preferably 0.4 to 4.0 mass%. When the content (modification amount) is 0.3 mass% or more, sufficient interaction with polyamide resin (A) and polyamide resin (B) is possible, thereby improving compatibility and facilitating more uniform dispersion of modified resin (C) in the polyamide resin composition. This further suppresses a decrease in tensile elongation at break after immersion in LLC. When the content (modification amount) is 5.0 mass% or less, excessive increases in melt viscosity due to excessive interaction are suppressed, making it less likely that melt fluidity at high temperatures will decrease. This further suppresses a decrease in the moldability of the polyamide resin composition.

The content (modification amount) of functional group structural units in modified resin (C) can be calculated from the charge ratio when preparing modified resin (C), or can be measured by NMR. The same NMR method as described for polyamide resin (A) can be used.

The density of the modified resin (C), measured in accordance with JIS K7112:1999, is preferably 0.800 g to 1.00 g/cm ^3. When the density of the modified resin (C) is 0.800 g/cm ³ or higher, the strength of the resulting molded article is less likely to be impaired, and when it is 0.800 g/cm ³ or lower, the resulting molded article is imparted with appropriate flexibility, and the decrease in tensile elongation at break after immersion in LLC can be further suppressed. From the same viewpoint, the density of the modified resin (C) is more preferably 0.800 to 0.950 g/cm ³ , and even more preferably 0.850 to 0.900 g/cm ^3. The density of the modified resin (C) can be adjusted by the composition of the raw materials used in synthesizing the resin before modification, which is the raw material, the polymerization temperature, the hydrogen concentration, etc.

The MFR (Melt Flow Rate) of the modified resin (C), measured according to ASTM D1238 at 230°C under a load of 2.16 kg, is preferably 0.5 to 20 g/10 min. An MFR of 0.5 g/10 min or more does not impair the melt fluidity of the semi-aromatic polyamide resin composition at high temperatures, while an MFR of 20 g/10 min or less suppresses gas generation during kneading.

Modified resin (C) is obtained by graft-modifying the unmodified resin with a compound containing a functional group structural unit.

Graft modification can be carried out using a variety of conventionally known methods. For example, it can be carried out using a melt modification method, in which the unmodified resin is melted using an extruder and a graft monomer is added to carry out graft copolymerization, or it can be carried out using a solution modification method, in which the unmodified resin is dissolved in a solvent and a graft monomer is added to carry out graft copolymerization. In either case, it is preferable to carry out the reaction in the presence of a radical initiator to efficiently graft copolymerize the graft monomer.

Examples of radical initiators include organic peroxides and organic peresters, specifically organic peroxides such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxidebenzoate)hexyne-3, 1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-di(tert- Examples of suitable peroxides include organic peresters such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl perbenzoate, tert-butyl perphenyl acetate, tert-butyl perisobutyrate, tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate, and tert-butyl perdiethyl acetate, and azo compounds such as azoisobutyronitrile and dimethyl azoisobutyrate. Among these, preferred are dialkyl peroxides such as dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxybenzoate)hexyne-3, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and 1,4-bis(tert-butylperoxyisopropyl)benzene. The radical initiator is typically used in a proportion of 0.001% by mass or more and 1% by mass or less based on the resin before modification as a raw material.

Specific examples of modified resin (C) include maleic anhydride-modified ethylene-α-olefin copolymer, maleic anhydride-modified styrene-ethylene/butylene-styrene copolymer (m-SEBS), etc.

1-3. Other Components The polyamide resin composition of the present invention may further contain other components in addition to those described above, provided that the effects of the present invention are not impaired. Examples of such other components include additives such as inorganic fillers, organic fillers, organic flame retardants, lubricants, antioxidants (heat stabilizers), heat stabilizers, weather stabilizers, antistatic agents, antislip agents, antiblocking agents, antifogging agents, pigments, dyes, natural oils, synthetic oils, and waxes. Furthermore, the polyamide resin composition may further contain other heat-resistant resins.

(Inorganic filler (D))
The inorganic filler (D) may be an inorganic filler having a fibrous, powdery, granular, plate-like, needle-like, cloth-like or mat-like shape.

Examples of fibrous inorganic fillers (D) include glass fibers, carbon fibers, asbestos fibers, and boron fibers. Of these, glass fibers are particularly preferred. The use of glass fibers improves moldability and also improves mechanical properties such as strength (elastic modulus) and heat resistance properties such as heat distortion temperature of molded articles containing the inorganic filler.

The average length of the fibrous inorganic filler (D) is typically 0.1 mm or more and 20 mm or less, and preferably 0.3 mm or more and 6 mm or less. The aspect ratio of the fibrous inorganic filler is typically 10 or more and 2000 or less, and preferably 30 or more and 600 or less.

In addition to fibrous inorganic fillers, other fillers in powder, granule, plate-like, needle-like, cloth-like, or mat-like shapes can also be used. Examples of such other fillers include powder-like or plate-like inorganic compounds such as silica, silica alumina, alumina, calcium carbonate, titanium dioxide, talc, wollastonite, diatomaceous earth, clay, kaolin, spherical glass, mica, gypsum, red iron oxide, magnesium oxide, and zinc oxide, as well as needle-like inorganic compounds such as potassium titanate. Two or more of these fillers can also be used in combination.

The average particle size of other fillers is typically 0.1 μm or more and 200 μm or less, and preferably 1 μm or more and 100 μm or less.

Fiber fillers and other fillers can also be treated with silane coupling agents or titanium coupling agents before use.

The inorganic filler preferably contains at least one of a fibrous filler and another filler, and more preferably contains at least one of a fibrous filler and talc.

(organic filler)
Examples of the organic filler include wholly aromatic polyamides such as polyparaphenylene terephthalamide, polymetaphenylene terephthalamide, polyparaphenylene isophthalamide, polymetaphenylene isophthalamide, condensates of diaminodiphenyl ether and terephthalic acid (isophthalic acid) and condensates of para(meta)aminobenzoic acid, wholly aromatic polyamideimides such as condensates of diaminodiphenyl ether and trimellitic anhydride or pyromellitic anhydride, wholly aromatic polyesters, wholly aromatic polyimides, heterocycle-containing compounds such as polybenzimidazole and polyimidazophenanthroline, and secondary processed products such as powder, plate, fiber, or cloth formed from polytetrafluoroethylene or the like.

(organic flame retardant)
The organic flame retardant may be a phosphinic acid compound or an organic flame retardant such as polybrominated styrene, brominated polyethylene ether, or brominated polystyrene, whose main constituent is a component unit represented by the following formula (I) produced from a brominated styrene monomer: In the following formula, m is a number of 1 to 5.

The polybrominated styrene preferably contains 60% by weight or more of dibrominated styrene units, and particularly preferably 70% by weight or more. The polybrominated styrene may also be copolymerized with 40% by weight or less, preferably 30% by weight or less, of monobrominated styrene and/or tribrominated styrene in addition to dibrominated styrene.

In addition to the organic flame retardants described above, the semi-aromatic polyamide resin composition of the present invention can also use at least one flame retardant aid selected from antimony oxide, sodium antimonate, tin oxide, iron oxide, zinc oxide, and zinc nitrate. Sodium antimonate is particularly preferred, and substantially anhydrous sodium antimonate that has been heat-treated at a high temperature of 550°C or higher is particularly preferred.

(antioxidant)
Examples of the antioxidant include phosphorus-based antioxidants, phenol-based antioxidants, amine-based antioxidants, and sulfur-based antioxidants.

Examples of phosphorus-based antioxidants include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triphenyl phosphite, 2-ethylhexyl acid phosphate, dilauryl phosphite, tri-iso-octyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, trilauryl phosphite, trilauryl-di-thiophosphite, trilauryl-tri-thiophosphite, trisnonylphenyl phosphite, distearyl pentaerythritol diphosphite, tris(mononylphenyl) phosphite, tris(dinonylphenyl) phosphite, trioctadecyl phosphite, 1,1,3-tris(2-methyl-di-tridecylphosphite-5-tert-butylphenyl)butane, 4,4'-butylidene-bis(3-methyl-6-tert-butyl)tridecyl sil phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butyl-di-tridecyl)phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol-di-phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-di-phosphite, tetrakis(2,4-di-tert-butylphenyl)4,4'-bisphenylene diphosphite, distearyl pentaerythritol diphosphite, tridecyl phosphite, tristearyl phosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, sorbitol-tris-phosphite-distearyl-mono-C30-diol ester and bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite. Among these are pentaerythritol-diphosphite-based phosphorus antioxidants such as bis(2,4-di-tert-butylphenyl)pentaerythritol-diphosphite and bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-diphosphite, as well as tetrakis(2,4-di-tert-butylphenyl)4,4'-bisphenylene diphosphite.

Examples of phenolic antioxidants include 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, 2,6-di-tert-butyl-p-cresol, 2,4,6-tri-tert-butylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, styrenated phenol, 4-hydroxy-methyl-2,6-di-tert-butyl ethylphenol, 2,5-di-tert-butyl-hydroquinone, cyclohexylphenol, butylhydroxyanisole, 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 4,4'-iso-propylidenebisphenol, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), 1,1-bis-(4-hydroxy-phenyl)cyclohexane, 4,4'-methylene-bis-(2,6-di- tert-butylphenol), 2,6-bis(2'-hydroxy-3'-tert-butyl-5'-methylmethylbenzyl)4-methyl-phenol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butyl-phenyl)butane, 1,3,5-tris-methyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxy-benzyl)benzene, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, tris(3,5-di-tert -butyl-4-hydroxyphenyl)isocyanurate, tris[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl-oxyethyl]isocyanate, 4,4'-thiobis(3-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), and N,N'-hexamethylenebis(3,5-di-tert-butylphenol-4-hydroxycinnamamide).

Examples of amine antioxidants include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, aldol-α-naphthylamine, 2,2,4-trimethyl-1,2-dihydroquinone polymer, and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline.

Examples of sulfur-based antioxidants include thiobis(β-naphthol), thiobis(N-phenyl-β-naphthylamine), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, dodecyl mercaptan, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyldithiocarbamate, nickel isopropyl xanthate, dilauryl thiodipropionate, and distearyl thiodipropionate.

(Other heat-resistant resins)
Examples of other heat-resistant resins include PPS (polyphenylene sulfide), PPE (polyphenyl ether), PES (polyether sulfone), PEI (polyether imide), LCP (liquid crystal polymer), and modified products of these resins. Polyphenylene sulfide is particularly preferred.

1-4. Composition of Polyamide Resin Composition The polyamide resin composition of the present invention comprises a polyamide resin and a modified resin (C), and the content of polyamide resin (A) is 70 to 95 parts by mass, the content of polyamide resin (B) is 5 to 30 parts by mass, and the content of modified resin (C) is 0.1 to 20 parts by mass, relative to 100 parts by mass of the polyamide resin ((A) + (B)).

The mass ratio ((A)/(B)) of the content of polyamide resin (A) to the content of polyamide resin (B) is preferably 70/30 to 95/5, and more preferably 80/20 to 95/5. By ensuring that the content of polyamide resin (A) is above a certain level, the crystallinity of the polyamide resin can be increased, further suppressing the decrease in tensile strength after immersion in LLC. Furthermore, by ensuring that the content of polyamide resin (B) is above a certain level, the crystallinity of the polyamide resin can be decreased, further suppressing the decrease in tensile elongation at break after immersion in LLC.

The content of the modified resin (C) per 100 parts by mass of the polyamide resin ((A) + (B)) is 0.1 to 20 parts by mass. When the content is 0.1 part by mass or more, the modified resin (C) can be dispersed in the polyamide resin, suppressing a decrease in tensile elongation at break after immersion in LLC. When the content is 20 parts by mass or less, excessive penetration of LLC due to the functional group structural units of the modified resin (C) present in the gaps between the crystals is suppressed, and hydrolysis of the polyamide resin that occurs during LLC immersion can be suppressed, thereby further suppressing a decrease in tensile strength after LLC immersion. From this perspective, the content of the modified resin (C) is preferably 0.5 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 3 parts by mass.

1-5. Physical Properties of Polyamide Resin Composition The polyamide resin compositions of the present invention each have a crystallization rate, measured by differential scanning calorimetry (DSC), expressed as the difference between the melting point (Tm) of the polyamide resin composition and the crystallization temperature (Tc) of the polyamide resin composition, of 31 to 40° C. As described above, a crystallization rate of 31° C. or higher can further suppress a decrease in tensile strength after immersion in LLC, while a crystallization rate of 40° C. or lower can suppress a decrease in tensile elongation at break after immersion in LLC.

The crystallization rate can be adjusted to the above range by adjusting the composition of the polyamide resin composition. The melting point (Tm) of the polyamide resin composition can be measured using the same method as described for polyamide resin (A). Furthermore, the temperature (°C) of the exothermic peak during the cooling process after the second heating using the above method can be taken as the crystallization temperature (Tc) of the polyamide resin composition.

The polyamide resin composition preferably has a ratio of the tensile strength after immersion to the tensile strength of the molded article before immersion in LLC (tensile strength retention rate) of 70% or more, and more preferably 72% or more. The tensile strength before immersion can be measured, for example, by preparing a Type A1 test piece as specified in JIS K 7139:2009 using the polyamide resin composition and measuring it according to a method in accordance with ISO 527:2012. The tensile strength after immersion can be measured, for example, by immersing the test piece A1 in a 50/50 solution of pure water and LLC liquid at 130°C for 500 hours and then measuring it according to a method in accordance with ISO 527:2012.

The polyamide resin composition preferably has a tensile elongation at break after immersion in LLC of 2.0% or more, and more preferably 2.2% or more. The tensile elongation at break after immersion in LLC was measured in accordance with ISO 527:2012.

1-6. Method for Producing Polyamide Resin Composition The polyamide resin composition of the present invention can be produced by any method. For example, it can be produced by mixing the polyamide resin (A), polyamide resin (B), and modified resin (C) in the above-mentioned ratios, melt-kneading the mixture, and, after the mixing and melt-kneading, granulating or pulverizing the mixture as needed.

The mixing method can be any known method, such as a Henschel mixer, V blender, ribbon blender, or tumbler blender.

The melt-kneading method can be any known method, such as using a single-screw extruder, multi-screw extruder, kneader, Banbury mixer, etc.

The granulation or pulverization method can be any known method, for example, granulation or pulverization can be performed using a pelletizer.

2. Molded Article The molded article of the present invention is obtained by molding the polyamide resin composition of the present invention.

In other words, the polyamide resin composition prepared as described above can be used to produce molded articles of the desired shape by conventional melt molding methods, such as compression molding, injection molding, or extrusion molding.

For example, the polyamide resin composition of the present invention can be placed in a molten state in an injection molding machine whose cylinder temperature is adjusted to a temperature equal to or higher than the melting point of polyamide resin (A), for example, approximately 300°C to 350°C, and then introduced into a mold of a predetermined shape to produce a molded article.

The shape of the molded article produced using the polyamide resin composition of the present invention is not particularly limited, and various shapes can be used depending on the application.

Molded articles of the polyamide resin composition of the present invention can be used in a variety of applications. Examples of such applications include automotive exterior parts such as radiator grilles, rear spoilers, wheel covers, hubcaps, cowl vent grilles, air outlet louvers, air scoops, hood bulges, sunroofs, sunroof rails, fenders, and tailgates; cylinder head covers, engine mounts, air intake manifolds, throttle bodies, air intake pipes, radiator tanks, radiator supports, water pump housings such as water pumps, water pump inlets, and water pump outlets; thermostat housings such as water jacket spacers and thermostat housings; automotive engine compartment parts such as cooling fans, fan shrouds, oil pans, oil filter housings, oil filler caps, oil level gauges, oil pumps, timing belts, timing belt covers, engine covers, and turbo-related parts; fuel caps, fuel filler tubes, automotive fuel tanks, fuel sender modules, fuel cut-off valves, quick connectors, canisters, These include automotive fuel system parts such as fuel delivery pipes and fuel filler necks; automotive drive system parts such as shift lever housings and propeller shafts; automotive chassis parts such as stabilizer bar linkage rods and engine mount brackets; automotive functional parts such as window regulators, door locks, door handles, outside door mirror stays, wipers and their parts, accelerator pedals, pedal modules, joints, plastic screws, nuts, bushings, seal rings, bearings, bearing retainers, gears and actuators; automotive electronic parts such as wire harness connectors, relay blocks, sensor housings, fuse parts, encapsulations, ignition coils and distributor caps, and high-voltage automotive electrical parts; general-purpose equipment fuel system parts such as fuel tanks for general-purpose equipment (brush cutters, lawn mowers, and chainsaws), as well as electrical and electronic parts such as connectors and LED reflectors; building materials, industrial equipment parts, and various housing or exterior parts such as small housings (including housings for personal computers and mobile phones) and exterior molded products.

The polyamide resin composition of the present invention can suppress the decrease in tensile strength of molded articles after immersion in LLC, and can suppress the decrease in tensile elongation at break after immersion in LLC, making it particularly suitable for use in environments exposed to antifreeze, and can be suitably used for thermostat housings, water pump housings, water jacket spacers, etc. Furthermore, it can be suitably used for automotive parts exposed to environmental temperatures of 100°C or higher, particularly turbo-related parts and high-voltage automotive electrical parts. Additionally, the resin composition of the present invention can be suitably used for automotive electronics parts, electrical and electronic parts, industrial equipment parts, and electrical equipment parts such as housings or exterior parts for electrical equipment.

The present invention will be specifically explained below with reference to examples, but the scope of the present invention is not limited to the description of the examples.

1. Constituent Materials 1-1. Preparation of Polyamide Resin (A) 2,774 g (16.7 mol) of terephthalic acid, 1,196 g (7.2 mol) of isophthalic acid, 2,800 g (24.1 mol) of 1,6-diaminohexane, 36.6 g (0.3 mol) of benzoic acid as a molecular weight modifier, 5.7 g (6.5 × ¹⁰ mol) of sodium hypophosphite monohydrate as a catalyst, and 545 g of distilled water were placed in an autoclave with a capacity of 13.6 L and purged with nitrogen. Stirring was started at 190 °C, and the internal temperature was raised to 250 °C over 3 hours. At this time, the internal pressure of the autoclave was raised to 3.03 MPa. The reaction was continued for 1 hour, after which the low-order condensate was discharged into the atmosphere through a spray nozzle installed at the bottom of the autoclave and extracted. Thereafter, the low-order condensate was cooled to room temperature, pulverized to a particle size of 1.5 mm or less in a pulverizer, and dried for 24 hours at 110° C. The water content of the obtained low-order condensate was 4110 ppm, and the intrinsic viscosity [η] was 0.15 dl/g.

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

The composition of the obtained polyamide (A) was such that the content of component units derived from terephthalic acid in the component units derived from dicarboxylic acids was 70 mol % and the content of component units derived from aromatic dicarboxylic acids other than terephthalic acid (isophthalic acid) was 30 mol %. The polyamide (A) also had an intrinsic viscosity [η] of 1.0 dl/g, a melting point Tm ₁ of 330°C, and a heat of fusion (ΔH) of 55 J/g.

1-2. Preparation of Other Polyamide Resins (A') 1,787 g (10.8 mol) of terephthalic acid, 1,921 g (13.1 mol) of adipic acid, 2,800 g (24.1 mol) of 1,6-diaminohexane, 5.7 g (6.5 × ¹⁰ mol) of sodium hypophosphite monohydrate, and 554 g of distilled water were placed in a 13.6 L autoclave and purged with nitrogen. Stirring was initiated at 190°C, and the internal temperature was raised to 250°C over three hours. At this time, the internal pressure of the autoclave was increased to 3.01 MPa. The reaction was continued for one hour, after which the low condensate was discharged into the atmosphere through a spray nozzle installed at the bottom of the autoclave and extracted. The mixture was then cooled to room temperature, pulverized in a pulverizer to a particle size of 1.5 mm or less, and dried at 110°C for 24 hours. The water content of the obtained low condensation product was 3600 ppm, and the intrinsic viscosity [η] was 0.14 dl/g.

Next, this low condensate was placed in a tray-type solid-state polymerization reactor, and after purging with nitrogen, the temperature was raised to 220°C over approximately 1 hour and 30 minutes. The reaction was then allowed to proceed for 1 hour, and the temperature was lowered to room temperature. The intrinsic viscosity [η] of the resulting polyamide was 0.48 dl/g. Subsequently, polyamide resin (A') was prepared by melt polymerization in a twin-screw extruder with a screw diameter of 30 mm and L/D = 36, with a barrel setting temperature of 330°C, a screw rotation speed of 200 rpm, and a resin feed rate of 6 kg/h.

The resulting polyamide resin (A') had an intrinsic viscosity [η] of 0.90 dl/g, a melting point Tm ₁ of 295° C., and a heat of fusion (ΔH) of 65 J/g.

1-3. Preparation of Polyamide Resin (B) 1,196 g (7.2 mol) of terephthalic acid, 2,774 g (16.7 mol) of isophthalic acid, 2,800 g (24.1 mol) of 1,6-diaminohexane, 109.5 g (0.9 mol) of benzoic acid as a molecular weight modifier, 5.7 g (6.5 × ¹⁰ mol) of sodium hypophosphite monohydrate as a catalyst, and 545 g of distilled water were placed in a 13.6 L autoclave and purged with nitrogen. Stirring was initiated at 190°C, and the internal temperature was raised to 250°C over three hours. At this time, the internal pressure of the autoclave was increased to 3.03 MPa. After continuing the reaction for one hour, the low-order condensate was discharged into the atmosphere through a spray nozzle installed at the bottom of the autoclave and extracted. The low-order condensate was then cooled to room temperature, pulverized in a pulverizer to a particle size of 1.5 mm or less, and dried at 110°C for 24 hours. The resulting low-order condensate had a water content of 3,000 ppm and an intrinsic viscosity [η] of 0.14 dl/g.

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

The composition of the resulting polyamide (B) was such that, among the dicarboxylic acid-derived component units, the content of component units derived from terephthalic acid was 30 mol %, and the content of component units derived from isophthalic acid was 70 mol %. Furthermore, the intrinsic viscosity [η] of polyamide (B) was 0.68 dl/g, the melting point was not measured, and the heat of fusion ΔH was 0 J/g.

The intrinsic viscosity [η], melting point Tm, and heat of fusion ΔH of polyamide resin (B) were measured using the following methods.

[Intrinsic viscosity [η]]
0.5 g of polyamide resin was dissolved in 50 ml of 96.5% sulfuric acid solution. The flow time of the obtained solution at 25°C ± 0.05°C was measured using an Ubbelohde viscometer and calculated based on the formula: [η] = η/(C(1 + 0.205η)).
[η]: Intrinsic viscosity (dl/g)
ηSP: specific viscosity C: sample concentration (g/dl)
t: number of seconds for the sample solution to flow down (seconds)
t ₀ : Number of seconds (seconds) for blank sulfuric acid to flow
ηSP=(t−t ₀ )/t ₀

[Melting point Tm ₁ ]
The melting points _Tm1 of the polyamide resin (A), the polyamide resin (A'), and the polyamide resin (B) were measured using a differential scanning calorimeter (DSC220C, manufactured by Seiko Instruments Inc.) as follows.

Approximately 5 mg of polyamide resin (A), polyamide resin (A'), or polyamide resin (B) was sealed in a measuring aluminum pan and heated from room temperature to 350°C at 10°C/min. To completely melt the resin, it was held at 350°C for 3 minutes and then cooled to 30°C at 10°C/min. Then, after leaving it at 30°C for 5 minutes, it was heated a second time to 350°C at 10°C/min. The temperature (°C) of the endothermic peak during this second heating was taken as the melting point ( _Tm1 ) of the polyamide resin.

[Heat of fusion ΔH]
The heat of fusion ΔH of polyamide resin (A), polyamide resin (A′), and polyamide resin (B) was determined from the area of the endothermic peak during melting in the first heating process using a differential scanning calorimeter (DSC220C type, manufactured by Seiko Instruments Inc.) in accordance with JIS K7121:2012.

1-4. Modified resin (C)
(Preparation of Modified Ethylene/1-Butene Copolymer (C1))
An ethylene/1-butene copolymer was prepared using a Ti-based catalyst. The resulting ethylene/1-butene copolymer had an ethylene content of 81 mol%, a density of 0.861 g/ ^cm3 , and an MFR (ASTM D 1238, 230°C, 2.16 kg load) of 1.2 g/10 min.

100 parts by mass of the ethylene-1-butene copolymer prepared above, 1.2 parts by mass of maleic anhydride, and 0.06 parts by mass of peroxide (Perhexyne-25B, manufactured by NOF Corporation) were mixed in a Henschel mixer, and the resulting mixture was melt-graft-modified in a 65 mmφ single-screw extruder with a barrel temperature set to 230°C to obtain a modified ethylene-1-butene copolymer.

The resulting modified ethylene/1-butene copolymer (C1) had a density of 0.866 g/ ^cm3 , an MFR (ASTM D1238 standard, 230°C, 2.16 kg load) of 1.2 g/10 min, and a content (modification amount) of structural units having a carboxylic acid group (carboxylic anhydride group) of 1.0 mass% based on the mass of the modified ethylene/1-butene copolymer (C1).

Preparation of Modified Styrene-Ethylene/Butylene-Styrene Copolymer (C2) A solution prepared by dissolving 100 parts by mass of styrene-ethylene/butylene-styrene copolymer (SEBS) (Tuftec H1041, styrene/ethylene/butylene=30/70, manufactured by Asahi Kasei Corporation), 1.2 parts by mass of maleic anhydride, and 0.06 parts by mass of peroxide (Perhexyne-25B, manufactured by NOF Corporation) in acetone was mixed. The resulting mixture was then charged through the hopper of a screw extruder having a screw diameter of 30 mm and L/D=42, and extruded into a strand at a barrel setting temperature of 250°C, a screw rotation speed of 180 rpm, and a discharge rate of 10 kg/h. The resulting strand was sufficiently cooled and then granulated to obtain maleic anhydride-modified styrene-ethylene/butylene-styrene copolymer (m-SEBS) (C2).

The resulting modified styrene-ethylene/butylene-styrene copolymer (m-SEBS) (C2) had a density of 0.92 g/ ^cm3 , an MFR (ASTM D1238 standard, 230°C, 2.16 kg load) of 5.0 g/10 min, and a content (modification amount) of structural units having a carboxylic acid group (carboxylic anhydride group) of 1% by mass relative to the mass of the modified styrene-ethylene/butylene-styrene copolymer.

The density, MFR, and degree of modification of the modified resin were measured using the following methods.

[density]
The density was measured at a temperature of 23°C using a density gradient tube in accordance with JIS K7112:1999.

[MFR]
The MFR was measured in accordance with ASTM D1238 at 230° C. under a load of 2.16 kg.

[Amount of modification]
The content (modification amount) (mass %) of component units derived from maleic anhydride in each copolymer was measured by NMR under the following conditions.
Measurement equipment: Nuclear magnetic resonance equipment (ECP500 type, manufactured by JEOL Ltd.)
Observed nucleus: ^13C (125MHz)
Sequence: Single pulse proton decoupling
Pulse width: 4.7 μsec (45° pulse)
Repeat time: 5.5 seconds
Accumulation count: 10,000 times or more
Solvent: orthodichlorobenzene/deuterated benzene (volume ratio: 80/20) mixed solvent
Sample concentration: 55 mg/0.6 mL
Measurement temperature: 120℃
Reference value of chemical shift: 27.50 ppm

1-5. Inorganic filler (D)
Glass fiber (ECS 03 T-747H, manufactured by Nippon Electric Glass Co., Ltd.) was used.

2. Preparation of Polyamide Resin Compositions (Examples 1 to 3 and Comparative Examples 1 to 7)
Polyamide resin (A), polyamide resin (A'), polyamide resin (B), modified resin (C), and inorganic filler (D) were mixed in a tumbler blender to obtain the compositions shown in Tables 1 and 2, and then melt-kneaded using a twin-screw extruder (TEX30α, manufactured by The Japan Steel Works, Ltd.) with a barrel temperature set at 345°C (310°C when polyamide resin (A') was used). The kneaded mixture was then extruded into strands and cooled in a water tank. The strands were then taken up in a pelletizer and cut to obtain pelletized polyamide resin compositions.

The crystallization rate of the resulting polyamide resin composition was measured using the difference between the melting point (Tm) and the crystallization temperature (Tc) of the polyamide resin composition as an index. The melting point (Tm) and crystallization temperature (Tc) of the polyamide resin composition were measured as follows using a differential scanning calorimeter (DSC220C, manufactured by Seiko Instruments Inc.).

Approximately 5 mg of the polyamide resin composition was sealed in a measuring aluminum pan and heated from room temperature to 350°C at 10°C/min. To completely melt the resin, it was held at 350°C for 5 minutes and then cooled to 30°C at 10°C/min. After leaving it at 30°C for 5 minutes, it was heated a second time to 350°C at 10°C/min. The temperature (°C) of the endothermic peak during this second heating was taken as the melting point (Tm) of the polyamide resin composition, and the temperature (°C) of the exothermic peak during the cooling process was taken as the crystallization temperature (Tc) of the polyamide resin composition.

The tensile strength (tensile strength retention rate) and tensile elongation at break of the polyamide resin composition after immersion in LLC were evaluated using the following methods.

The obtained polyamide resin composition was molded under the following molding conditions to obtain a Type A1 dumbbell test piece specified in JIS K 7139:2009.
(Molding conditions)
Molding machine: Toshiba Machine Co., Ltd. EC75N-2A
Molding machine barrel setting temperature: Melting point (Tm) of polyamide resin (A) or polyamide resin (A') + 10°C
Mold temperature: 160°C
Injection setting speed: 30mm/sec

(Tensile strength retention rate)
The obtained test piece was left for 24 hours in a nitrogen atmosphere at a temperature of 23° C. Thereafter, the tensile strength (MPa) of the test piece was obtained in accordance with ISO 527:2012.

Test pieces obtained under similar conditions were immersed in a 50/50 solution of pure water and long-life coolant (LLC liquid) (G48, manufactured by BASF) in an autoclave at 130°C for 500 hours. The tensile strength (MPa) of the test pieces after immersion was then measured in accordance with ISO 527:2019.

The ratio of the tensile strength after immersion in the above solution to the tensile strength before immersion (tensile strength retention rate) was calculated and used as an index of chemical resistance.

(Tensile elongation at break after immersion in LLC)
After immersion in the above solution, the test piece was measured for tensile elongation at break [%] in accordance with ISO 527:2019.

The evaluation results for Examples 1 to 3 are shown in Table 1, and the evaluation results for Comparative Examples 1 to 7 are shown in Table 2. Note that the numerical values for each composition in Tables 1 and 2 represent parts by mass.

As shown in Table 1, Examples 1 to 3, which contain polyamide resin and modified resin (C), and contain 70 to 95 parts by mass of polyamide resin (A), 5 to 30 parts by mass of polyamide resin (B), and 0.1 to 20 parts by mass of modified resin (C) per 100 parts by mass of polyamide resin, and have a crystallization rate (Tm-Tc) of 31 to 40°C, all showed high strength retention before and after LLC immersion, and high tensile elongation at break after LLC immersion (high LLC resistance).

A crystallization rate of 31°C or higher allows for the formation of more crystals during the short time it takes for the polyamide resin composition to reach its crystallization temperature during molding, and it is believed that the crystals suppress excessive penetration of LLC. This is believed to have prevented a decrease in tensile strength after immersion in LLC. A crystallization rate of 40°C or lower is believed to have prevented excessive crystal formation during molding, thereby preventing a decrease in tensile break elongation after immersion in LLC. Furthermore, the inclusion of highly crystalline polyamide resin (A) and polyamide resin (B) moderately reduces the crystallinity of the polyamide resin, making it easier for the modified resin (C) to be more uniformly dispersed in the crystallized polyamide resin, which is believed to have prevented a decrease in elongation after immersion in LLC.

In contrast, as shown in Table 2, in Comparative Examples 1 to 7, which did not contain any of polyamide resin (A), polyamide resin (B), and modified resin (C), the strength retention rate before and after LLC immersion and the tensile breaking elongation after LLC immersion did not increase. In particular, Comparative Example 7, which contained polyamide resin (A'), polyamide resin (B), and modified resin (C), had a significantly lower strength retention rate before and after LLC immersion than Comparative Examples 1 to 3.

Claims (5)

A polyamide resin composition,
A polyamide resin,
and a modified resin (C) modified with a compound containing a functional group structural unit, the content of which is 0.1 to 20 parts by mass relative to 100 parts by mass of the polyamide resin,
The polyamide resin comprises: a polyamide resin (A) having a melting point (Tm ₁ ) of 300°C or higher as measured by a differential scanning calorimeter (DSC), the content of which is 70 to 95 parts by mass relative to 100 parts by mass of the polyamide resin; and a polyamide resin (B) having a melting point that is not substantially measurable by a differential scanning calorimeter (DSC), the content of which is 5 to 30 parts by mass relative to 100 parts by mass of the polyamide resin;
The polyamide resin (A) contains a component unit (a1) derived from a dicarboxylic acid and a component unit (a2) derived from a diamine,
the dicarboxylic acid-derived component units (a1) comprise, relative to the total number of moles of the dicarboxylic acid-derived component units (a1), 20 to 80 mol % of terephthalic acid-derived component units and 20 to 80 mol % of aromatic dicarboxylic acid-derived component units other than terephthalic acid;
the diamine-derived component unit (a2) includes at least one of a component unit (a2-1) derived from an aliphatic diamine having 4 to 15 carbon atoms and a component unit (a2-2) derived from an alicyclic diamine having 4 to 20 carbon atoms;
the modified resin (C) is a modified resin obtained by modifying one type of resin selected from the group consisting of ethylene-α-olefin copolymer, styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene/butylene-styrene copolymer (SEBS), and styrene-ethylene/propylene-styrene copolymer (SEPS) with a compound containing a carboxylic acid group structural unit;
a crystallization rate, which is expressed as the difference between the melting point (Tm) of the polyamide resin composition and the crystallization temperature (Tc) of the polyamide resin composition, measured by a differential scanning calorimeter (DSC), of 31 to 40°C;
Polyamide resin composition. The polyamide resin (B) contains a component unit (b1) derived from a dicarboxylic acid and a component unit (b2) derived from a diamine,
The dicarboxylic acid-derived component unit (b1) includes an isophthalic acid-derived component unit,
The diamine-derived component unit (b2) includes a component unit derived from an aliphatic diamine having 4 to 15 carbon atoms.
The polyamide resin composition according to claim 1 . The structural unit (b1) derived from a dicarboxylic acid further contains a component unit derived from terephthalic acid,
a molar ratio of the component units derived from isophthalic acid to the component units derived from terephthalic acid (component units derived from isophthalic acid/component units derived from terephthalic acid) is 55/45 to 95/5;
The polyamide resin composition according to claim 2 . The modified resin (C) is an ethylene-α-olefin copolymer and contains functional group structural units in an amount of 0.3 to 5.0 mass% based on the total mass of the modified resin (C).
The polyamide resin composition according to any one of claims 1 to 3 . A molded product obtained by molding the polyamide resin composition according to any one of claims 1 to 4 .
Molded body.