JP2024125639A - Polyamide resin composition - Google Patents

Abstract

To provide a polyamide resin composition with high fluidity during molding, high mechanical strength, and high reflow heat resistance.SOLUTION: The resin composition includes a polyamide resin (A), a polystyrene resin (B) with a weight average molecular weight of 100,000 or more, and a flame retardant (C). The content of the polystyrene resin (B) is less than 10 mass% relative to the total mass of the polyamide resin (A) and the polystyrene resin (B).SELECTED DRAWING: None

Description

The present invention relates to a polyamide resin composition.

Resin compositions containing polyamide resins have excellent moldability, mechanical properties, chemical resistance, etc., and are used in a variety of fields, including industrial materials, automobiles, electrical and electronic products, and industrial applications. Among these, they are particularly popular in the electrical and electronic fields, taking advantage of their excellent mechanical strength and heat resistance.

In recent years, with the trend toward smaller electronic devices and lighter products, there is a demand for processing polyamide resin compositions into complex shapes and thinning them by injection molding. In order to improve injection moldability, it is important to increase the fluidity of the polyamide resin composition during injection molding, and various methods for increasing fluidity have been proposed. Patent Document 1 proposes a method of adding relatively low molecular weight polystyrene to a semi-aromatic polyamide resin. Patent Document 2 shows that the fluidity of a semi-aromatic polyamide resin can be increased by adding 10% by mass or more of polystyrene resin to the resin.

JP 2018-65942 A JP 2000-256553 A

However, after extensive research, the inventors of the present invention found that adding a relatively low molecular weight polystyrene, as in Patent Document 1, significantly reduces toughness. In addition, adding a relatively large amount of polystyrene, as in Patent Document 2, tends to reduce heat resistance and flame retardancy, and is likely to impair reflow heat resistance.

The present invention aims to provide a polyamide resin composition that has high flowability during molding, mechanical strength, and reflow heat resistance.

The present invention provides a polyamide resin composition comprising a polyamide resin (A), a polystyrene resin (B) having a weight average molecular weight of 100,000 or more, and a flame retardant (C), in which the content of the polystyrene resin (B) is less than 10 mass% based on the total mass of the polyamide resin (A) and the polystyrene resin (B).

The polyamide resin composition of the present invention has high flowability during molding, mechanical strength, and reflow heat resistance.

FIG. 2 is a diagram showing the relationship between the temperature and time of the reflow process in the reflow heat resistance test carried out in the examples and comparative examples of the present application.

The polyamide resin composition of this embodiment is described below.

As mentioned above, there is a demand for improved moldability of polyamide resin compositions, but when attempting to improve moldability, reflow heat resistance and flame retardancy tend to decrease, and toughness also tends to decrease. Therefore, the reality is that no polyamide resin composition has been obtained that combines moldability, reflow heat resistance, flame retardancy, and high toughness.

In response to this, the inventors of the present invention conducted extensive research and found that a polyamide resin composition having the above-mentioned properties can be obtained by combining polyamide resin (A), polystyrene resin (B) having a weight-average molecular weight of 100,000 or more, and flame retardant (C) and setting the amount of polystyrene resin (B) to less than 10% by mass relative to the total mass of polyamide resin and polystyrene resin (B). The reasons for this are believed to be as follows.

In general, in a composition containing polyamide resin, the amide bonds of multiple polyamide resin molecules are hydrogen-bonded to each other. As a result, it is believed that the fluidity during melting is low, and molding processability is likely to be low. In contrast, when polyamide resin (A), flame retardant (C), and polystyrene resin (B) having a relatively large molecular weight (molecular weight of 100,000 or more) are mixed, the fluidity is increased by the flame retardant (C) having a low melt viscosity. Furthermore, the hydrogen bonds between the amide bonds of polyamide resin (A) are broken by the highly hydrophobic polystyrene. As a result, it is believed that molding processability is significantly improved. Furthermore, the water absorption rate of the polyamide resin composition can be reduced by the high molecular weight of polystyrene resin (B) and the high hydrophobicity of the flame retardant (C), and the flame retardancy can also be increased by the flame retardant (C).

In addition, the addition of polystyrene resin to polyamide resin improves the fluidity during melting, but can cause a decrease in toughness. By setting the weight-average molecular weight of the polystyrene resin to 100,000 or more and setting the amount of polystyrene resin (B) added to less than 10 mass% of the total mass of the polyamide resin and polystyrene resin (B), it is possible to increase the fluidity during melting while suppressing the decrease in toughness.

Here, the polyamide resin composition of this embodiment may contain other components as necessary in addition to the polyamide resin (A), polystyrene resin (B), and flame retardant (C), such as a flame retardant auxiliary (D), a filler, and various additives. Each component will be described below.

Polyamide resin (A)
The polyamide resin (A) may be any resin containing a plurality of amide bonds, and is usually a resin obtained by polymerizing a dicarboxylic acid and a diamine. Such a polyamide resin (A) contains a dicarboxylic acid component unit (Aa) derived from a dicarboxylic acid and a diamine component unit (Ab) derived from a diamine.

The polyamide resin (A) may be a semi-aromatic polyamide resin obtained by polymerizing mainly an aromatic dicarboxylic acid and an aliphatic or alicyclic diamine, a semi-aromatic polyamide resin obtained by polymerizing mainly an aliphatic or alicyclic dicarboxylic acid and an aromatic diamine, or an aliphatic polyamide resin obtained by polymerizing mainly an aliphatic dicarboxylic acid and an aliphatic diamine. Among these, the polyamide resin (A) is preferably a semi-aromatic polyamide resin. That is, the polyamide resin (A) is more preferably a semi-aromatic polyamide resin having a dicarboxylic acid component unit (Aa) and/or a diamine component unit (Ab) having an aromatic ring, and a dicarboxylic acid component unit (Aa) and/or a diamine component unit (Ab) not having an aromatic ring. When the polyamide resin (A) is a semi-aromatic polyamide resin, the heat resistance and low water absorption of the polyamide resin composition are more likely to be improved.

The dicarboxylic acid component unit (Aa) derived from the dicarboxylic acid of the polyamide resin (A) may contain a component unit derived from a biomass-derived dicarboxylic acid, and the diamine component unit (Ab) derived from the diamine may contain a component unit derived from a biomass-derived diamine. The polyamide resin (A) may be a biomass-derived polyamide resin (A) obtained by polymerizing a raw material group including a raw material derived from biomass.
Hereinafter, an example will be described in which the polyamide resin (A) is a semi-aromatic polyamide resin.

In the polyamide resin (A), at least one of the dicarboxylic acid component unit (Aa) and the diamine component unit (Ab) preferably contains both a component unit having an aromatic ring and a component unit not having an aromatic ring. And, for at least one of the dicarboxylic acid component unit (Aa) and the diamine component unit (Ab), the number of moles of the component unit not having an aromatic ring is preferably 30 mol% or more and 70 mol% or less, more preferably 35 mol% or more and 60 mol% or less, and even more preferably 37.5 mol% or more and 55 mol% or less, based on the total number of moles of the component unit having an aromatic ring and the component unit not having an aromatic ring. In addition, the number of moles of the component unit not having an aromatic ring in the dicarboxylic acid component (Aa) is preferably 30 mol% or more and 70 mol% or less, more preferably 35 mol% or more and 60 mol% or less, and even more preferably 37.5 mol% or more and 55 mol% or less, based on the total number of moles of the dicarboxylic acid component (Aa). When the dicarboxylic acid component unit (Aa) or the diamine component unit (Ab) contains many component units that do not have an aromatic ring, the distance between the multiple polyamide resins (A) in the polyamide resin composition is usually short, and the amide bonds are more likely to form hydrogen bonds. In contrast, the polyamide resin composition of this embodiment contains the polystyrene resin (B) and the flame retardant (C) described below in addition to the polyamide resin (A). Therefore, even if the polyamide resin (A) contains many component units that do not have an aromatic ring as described above, the polyamide bonds are less likely to form hydrogen bonds, and the fluidity of the polyamide resin composition is sufficiently high.

Here, the type of dicarboxylic acid component unit (Aa) constituting the polyamide resin (A) is not particularly limited, and may include, for example, a component unit derived from an aromatic dicarboxylic acid, a component unit derived from an alicyclic dicarboxylic acid, a component unit derived from an aliphatic dicarboxylic acid, etc. In addition, the polyamide resin (A) may contain only one type of dicarboxylic acid component unit (Aa) in one molecule, or may contain two or more types of dicarboxylic acid component units (Aa). From the viewpoint of the heat resistance of the polyamide resin (A) and the polyamide resin composition containing it, it is preferable that at least a part of the dicarboxylic acid component unit (Aa) is a terephthalic acid component unit derived from terephthalic acid. The amount of the terephthalic acid component unit is preferably 30 mol% or more and 100 mol% or less, more preferably 30 mol% or more and 70 mol% or less, based on the total number of moles of the dicarboxylic acid component unit (Aa).

The polyamide resin (A) may contain component units derived from aromatic dicarboxylic acids other than terephthalic acid. Examples of aromatic dicarboxylic acids other than terephthalic acid include isophthalic acid, 2-methylterephthalic acid, naphthalenedicarboxylic acid, phthalic anhydride, trimellitic acid, pyromellitic acid, trimellitic anhydride, pyromellitic anhydride, etc. The polyamide resin may contain only one type of component unit derived from these, or may contain two or more types. The total number of moles of the component units derived from aromatic dicarboxylic acids other than terephthalic acid is preferably 70 mol% or less, more preferably 20 mol% or more and 70 mol% or less, based on the total number of moles of the dicarboxylic acid component units (Aa).

The polyamide resin (A) may contain a component unit derived from an aliphatic dicarboxylic acid. The number of carbon atoms in the aliphatic dicarboxylic acid is preferably 4 to 20, more preferably 6 to 12, and even more preferably 6 to 10. The hydrocarbon structure in the aliphatic dicarboxylic acid may be branched, but is linear, that is, the aliphatic dicarboxylic acid is more preferably a linear aliphatic dicarboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, etc., and the polyamide resin (A) may contain only one or more of the components derived from these. Among the above, adipic acid is particularly preferable from the viewpoint of improving the mechanical strength of the polyamide resin (A). The amount of component units derived from aliphatic dicarboxylic acids is preferably 70 mol% or less, more preferably more than 30 mol% and 70 mol% or less, and even more preferably 35 mol% or more and 60 mol% or less, based on the total number of moles of dicarboxylic acid component units (Aa).

The number of carbon atoms of the alicyclic dicarboxylic acid is preferably 4 to 20, more preferably 6 to 12, and even more preferably 6 to 10. Examples of alicyclic dicarboxylic acids include cyclohexane dicarboxylic acid. The amount of component units derived from alicyclic dicarboxylic acids is preferably 80 mol% or less, more preferably more than 10 mol% and 70 mol% or less, and even more preferably 20 mol% or more and 60 mol% or less, based on the total number of moles of dicarboxylic acid component units (Aa). The polyamide resin (A) may contain component units derived from alicyclic dicarboxylic acids.

The polyamide resin (A) preferably contains terephthalic acid component units and adipic acid component units as the dicarboxylic acid component units (Aa). In this case, the amount of the terephthalic acid component units is preferably 30 mol% or more and 70 mol% or less, and more preferably 40 mol% or more and 65 mol% or less, relative to the total number of moles of the dicarboxylic acid component units (Aa). The amount of the adipic acid component units is preferably 30 mol% or more and 70 mol% or less, and more preferably 35 mol% or more and 60 mol% or less, relative to the total number of moles of the dicarboxylic acid component units (Aa).

The type of diamine component unit (Ab) constituting the semi-aromatic polyamide resin (polyamide resin (A)) is not particularly limited, and may include, for example, a component unit derived from an aromatic diamine, a component unit derived from an alicyclic diamine, a component unit derived from an aliphatic diamine, etc. The polyamide resin (A) may contain only one type of diamine component unit (Ab) in one molecule, or may contain two or more types of diamine component units (Ab). From the viewpoint of the heat resistance and low water absorption of the polyamide resin (A), it is preferable that the polyamide resin (A) mainly contains at least one of a diamine component unit derived from an aliphatic diamine and a diamine component unit derived from an alicyclic diamine. Moreover, the polyamide resin (A) preferably contains a total of 80 mol% to 100 mol% of diamine component units derived from aliphatic diamines having 4 to 15 carbon atoms and diamine component units derived from alicyclic diamines having 4 to 20 carbon atoms, more preferably 90 mol% to 100 mol%, and it is particularly preferable that substantially all of the diamine component units (Ab) are at least one of component units derived from aliphatic diamines having 4 to 15 carbon atoms and alicyclic diamine component units derived from alicyclic diamines having 4 to 20 carbon atoms. The hydrocarbon structure in the aliphatic diamine may be branched, but is linear, that is, the aliphatic diamine is preferably a linear aliphatic diamine.

Examples of aliphatic diamines having 4 to 15 carbon atoms include linear aliphatic diamines such as 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane; and branched aliphatic diamines such as 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. Among these, 1,6-diaminohexane, 1,9-diaminononane, 2-methyl-1,5-diaminopentane, and 2-methyl-1,8-diaminooctane are preferred, with 1,6-diaminohexane being more preferred.

Examples of component units derived from alicyclic diamines include 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 2,5-bisaminomethylnorbornane, 2,6-bisaminomethylnorbornane, isophoronediamine, piperazine, 2,5-dimethylpiperazine, bis(4-aminocyclohexyl)methane, 1,3-bis(aminocyclohexyl)methane, bis(4-aminocyclohexyl)propane, 4,4'-diamino-3,3'-dimethyldicyclohexyl ... Included are component units derived from amino-3,3'-dimethyldicyclohexylmethane, 4,4'-diamino-3,3'-dimethyl-5,5'-dimethyldicyclohexylmethane, 4,4'-diamino-3,3'-dimethyl-5,5'-dimethyldicyclohexylpropane, α,α'-bis(4-aminocyclohexyl)-p-diisopropylbenzene, α,α'-bis(4-aminocyclohexyl)-m-diisopropylbenzene, α,α'-bis(4-aminocyclohexyl)-1,4-cyclohexane, and α,α'-bis(4-aminocyclohexyl)-1,3-cyclohexane. Among these, component units derived from 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 2,5-bisaminomethylnorbornane, 2,6-bisaminomethylnorbornane, bis(4-aminocyclohexyl)methane, and 4,4'-diamino-3,3'-dimethyldicyclohexylmethane are preferred, and component units derived from 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 2,5-bisaminomethylnorbornane, 2,6-bisaminomethylnorbornane, and bis(4-aminocyclohexyl)methane are more preferred.

The amount of the component units derived from the alicyclic diamine is preferably 80 mol% or less, more preferably more than 10 mol% and 70 mol% or less, and even more preferably 20 mol% or more and 60 mol% or less, based on the total number of moles of the diamine component units (Ab).

The polyamide resin (A) preferably contains 50 mol% or more and 100 mol% or less of 1,6-diaminohexane component units as the diamine component units (Ab), more preferably contains 60 mol% or more and 100 mol% or less of 1,6-diaminohexane component units, even more preferably contains 80 mol% or more and 100 mol% or less of 1,6-diaminohexane component units, and even more preferably contains 90 mol% or more and 100 mol% or less of 1,6-diaminohexane component units, and it is particularly preferable that substantially all of the diamine component units (Ab) are 1,6-diaminohexane component units.

Here, the melting point (Tm) of the polyamide resin (A) measured by differential scanning calorimetry (DSC) is preferably 280 to 330°C, more preferably 290 to 330°C. If the melting point of the polyamide resin (A) is within the above range, the heat resistance of the polyamide resin composition can be improved while there is no need to excessively increase the molding temperature, which is preferable. The melting point of the polyamide resin (A) is adjusted by the type of dicarboxylic acid component unit (Aa) and diamine component unit (Ab) constituting the polyamide resin (A), the molecular weight of the polyamide resin (A), etc.

The melting point (Tm) is measured using a differential scanning calorimeter (e.g., PerkinElmer DSC7). Specifically, about 5 mg of polyamide resin (A) is sealed in an aluminum pan for measurement and heated from room temperature to 340°C at 10°C/min. In order to completely melt the polyamide resin (A), it is held at 340°C for 5 minutes and then cooled to 23°C at 10°C/min. After leaving it at 23°C for 5 minutes, it is heated a second time to 340°C at 10°C/min. The peak temperature (°C) during this second heating is taken as the melting point (Tm) of the polyamide resin (A).

The polyamide resin (A) preferably has an intrinsic viscosity [η] of 0.5 to 1.2 dl/g, more preferably 0.5 to 0.9 dl/g, and even more preferably 0.7 to 0.85 dl/g, measured at 25°C in 96.5% sulfuric acid. When the intrinsic viscosity [η] is within this range, the flowability during molding tends to be better. When the intrinsic viscosity [η] is within the above range, the compatibility with the polystyrene resin (B) described below and the dispersibility of the flame retardant (C) tend to be better.

The intrinsic viscosity is a value measured in accordance with JIS K6810-1977, and is calculated based on the following formula by dissolving about 0.5 g of polyamide resin (A) in 50 ml of 96.5% concentrated sulfuric acid, measuring the number of seconds it takes for the obtained solution to flow down under conditions of 25°C ± 0.05°C using an Ubbelohde viscometer.
[η]=ηSP/[C(1+0.205ηSP)]
ηSP=(t-t0)/t0
[η]: Intrinsic viscosity (dl/g)
ηSP: Specific viscosity C: Sample concentration (g/dl)
t: number of seconds for sample solution to flow (seconds)
t0: Number of seconds (seconds) for blank sulfuric acid to flow

The amount of polyamide resin (A) in the polyamide resin composition is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 60% by mass or less, based on the total mass of the polyamide resin composition. When the amount of polyamide resin (A) is within this range, the inherent mechanical strength and reflow heat resistance of polyamide resin (A) are more easily exhibited.

Polystyrene resin (B)
The polystyrene resin (B) may be any resin that is mainly polymerized from styrene-based monomers (excluding those copolymerized with butadiene, etc.) and has a weight-average molecular weight of 100,000 or more.

Examples of styrene-based monomers include styrene or monomers having a substituent bonded to the benzene ring of the styrene. Specific examples include styrene; alkylstyrenes such as p-methylstyrene, m-methylstyrene, o-methylstyrene, ethylstyrene, isopropylstyrene, and t-butylstyrene; and alkoxystyrenes such as methoxystyrene and ethoxystyrene. The polystyrene resin may be a polymer of only one of these styrene-based monomers, or may be a polymer of two or more of them. Furthermore, it may be a polymer of other monomers as long as the purpose and effect of the present invention are not impaired. However, the amount of structural units derived from styrene-based monomers in polystyrene resin (B) is 50 mol% or more, preferably 60 mol% or more, and more preferably 70 mol% or more, based on the total number of moles of structural units of polystyrene resin (B). There are no particular limitations on the type of monomer other than the styrene-based monomer that is copolymerized with the above styrene-based monomer (excluding butadiene, etc.).

Among the polystyrene resins (B), polystyrene, poly-p-methylstyrene, poly-m-methylstyrene, poly-o-methylstyrene, poly-t-butylstyrene, and copolymers of styrene and p-methylstyrene are preferred, with polystyrene being more preferred.

The weight average molecular weight of the polystyrene resin (B) may be 100,000 or more, preferably 150,000 or more, and more preferably 200,000 or more. There is no particular upper limit, but it is preferably 1,000,000 or less, and more preferably 500,000 or less. The weight average molecular weight of the polystyrene resin (B) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

The amount of polystyrene resin (B) in the polyamide resin composition is preferably less than 10% by mass, more preferably 1% by mass or more and 9% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less, based on the total mass of the polyamide resin (A) and polystyrene resin (B) described above. As described above, when the amount of polystyrene resin (B) is within this range, it is possible to increase the fluidity of the polyamide resin composition and reduce the water absorption rate without impairing the inherent mechanical strength and reflow heat resistance of the polyamide resin (A).

Flame retardant (C) and flame retardant assistant (D)
The flame retardant (C) may be any compound capable of imparting flame retardancy to the polyamide resin composition. When the polyamide resin composition is used for electric/electronic components or surface-mounted components, the polyamide resin composition is required to have high flame retardancy and flame resistance such as V-0 as specified by Underwriters Laboratories Standard UL94. Therefore, in this embodiment, the flame retardant (C) is contained in the polyamide resin composition to enhance its flame retardancy. As described above, in this embodiment, the addition of the flame retardant (C) can also improve the flowability and reduce the water absorption rate of the polyamide resin composition.

Known flame retardants can be used as the flame retardant (C), and examples include halogen-based flame retardants such as brominated polystyrene, polybrominated styrene, and brominated polyphenylene ether; and non-halogen-based flame retardants such as metal salts of phosphoric acid compounds, phosphazene compounds, and melamine polyphosphates. Among these, brominated polystyrene and polybrominated styrene are preferred, and brominated polystyrene is more preferred, from the viewpoints of easily obtaining the above-mentioned flowability improving effect and water absorption reducing effect, and further having good compatibility with the polystyrene resin (B).

Brominated polystyrene is a flame retardant obtained by brominating polystyrene or poly-α-methylstyrene. In the brominated polystyrene, bromine atoms are bonded to the carbon atoms constituting the aromatic ring, but depending on the production method, bromine atoms may also be bonded to the alkyl chain constituting the main skeleton of the polymer. The flame retardant (C) may be any brominated polystyrene, but a type in which bromine atoms are mainly bonded to the carbon atoms constituting the aromatic ring is preferred, and it is preferable that substantially no bromine atoms are bonded to the alkyl chain constituting the main skeleton of the polymer. The bromine content in the brominated polystyrene is preferably 65 to 71 mass%, more preferably 67 to 71 mass%. Furthermore, substantially no bromine atoms are bonded to the alkyl chain constituting the main skeleton of the polymer means that the proportion of bromine atoms bonded to the alkyl chain constituting the main skeleton of the polymer is 0 to 0.5 mass%. The proportion is more preferably 0 to 0.2 mass%. Such brominated polystyrene has good thermal stability, and the thermal stability of the polyamide resin composition obtained using it is also improved.

The weight average molecular weight of the brominated polystyrene is preferably 1000 to 4800, more preferably 2000 to 4500. The number average molecular weight (Mn) is preferably 800 to 4800, and the molecular weight distribution (Mw/Mn) is preferably 1.05 to 1.25. The weight average molecular weight and number average molecular weight are polystyrene-equivalent values measured by gel permeation chromatography (GPC) using chloroform as the mobile phase, a column temperature of 40°C, and a differential refractometer detector. The melt flow rate (MFR) of the brominated polystyrene is preferably 200 to 1000 g/10 min, more preferably 400 to 900 g/10 min. The MFR is the value measured at a load of 1200 g, a temperature of 270°C, and an orifice inner diameter of 2.095 mm. When the molecular weight of the brominated polystyrene is within the above range, the flame retardancy and toughness of the polyamide resin composition tend to be good.

The amount of the flame retardant (C) is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less, relative to the total mass of the polyamide resin composition. When the amount of the flame retardant (C) is within this range, the flame retardancy of the polyamide resin composition is likely to be increased, and the flowability is also likely to be further improved.

The polyamide resin composition may contain a flame retardant auxiliary (D) together with the flame retardant (C). The flame retardant auxiliary may be any one that enhances the flame retardant effect of the flame retardant (C), and may be any known one. Specific examples of the flame retardant auxiliary include antimony compounds such as antimony trioxide, antimony tetraoxide, antimony pentoxide, and sodium antimonate; zinc compounds such as zinc borate, zinc stannate, and zinc phosphate; calcium borate, calcium molybdate, and the like. These may be used alone or in combination of two or more. Among these, sodium antimonate, zinc borate, and zinc phosphate are preferred, and in particular, sodium antimonate and anhydrous zinc borate (2ZnO.3B ₂ O ₃ ) are preferred from the viewpoint of thermal stability.

The amount of the flame retardant aid in the polyamide resin composition is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.2% by mass or more and 3% by mass or less, based on the total mass of the polyamide resin composition.

Others The polyamide resin composition of the present embodiment may contain other components, as necessary, in addition to the polyamide resin (A), polystyrene resin (B), flame retardant (C) and flame retardant auxiliary (D) described above, within a range that does not impair the object and effect of the present invention. Examples of other components include a filler.

The filler may be fibrous, particulate or flat, but is preferably fibrous. Examples of fibrous fillers include glass fiber, wollastonite, potassium titanate whiskers, calcium carbonate whiskers, aluminum borate whiskers, magnesium sulfate whiskers, sepiolite, xonotlite, zinc oxide whiskers, milled fiber, cut fiber, wholly aromatic polyamide fiber (e.g., polyparaphenylene terephthalamide fiber, polymetaphenylene terephthalamide fiber, polyparaphenylene isophthalamide fiber, polymetaphenylene isophthalamide fiber, and fiber obtained from a condensate of diaminodiphenyl ether and terephthalic acid or isophthalic acid), boron fiber, liquid crystal polyester fiber, carbon fiber, etc. Among these, glass fiber, wollastonite and carbon fiber are preferred because they are easy to increase the strength (rigidity) and heat resistance of the resulting polyamide resin composition. The polyamide resin composition may contain only one type of fibrous filler, or may contain two or more types.

The weight average fiber length of the fibrous filler is preferably 100 μm to 20 mm, more preferably 500 μm to 10 mm, and even more preferably 700 μm to 10 mm. The weight average fiber diameter is preferably 15 μm to 40 μm, and more preferably 15 μm to 30 μm. The weight average fiber length and weight average fiber diameter can be specified as follows.
1) The polyamide resin composition or a molded article obtained therefrom is dissolved in a hexafluoroisopropanol/chloroform solution (0.1/0.9% by volume), and then filtered to obtain a residue.
2) The filtered material obtained in 1) above is dispersed in water, and the fiber length (Li) and diameter (Di) of each of 300 randomly selected fibers are measured using an optical microscope (magnification: 50x).
3) From the measured fiber length (Li) and diameter (Di) and their distributions, the weight average diameter and weight average length are determined based on the following formulas.
Weight average fiber length=(Σqi×Li ² )/(Σqi×Li)
In the above formula, Li represents the fiber length of the filler (D), and qi represents the number of fillers (D) having a fiber length of Li.
Weight average diameter = (Σri×Di ² )/(Σri×Di)
In the above formula, Di represents the diameter of the filler (D), and ri represents the number of fillers (D) having a diameter of Di.

The above-mentioned fibrous filler may be treated with a known surface treatment agent, such as a coupling agent such as a silane-based coupling agent, a titanium-based coupling agent, or an aluminate-based coupling agent, or a bundling agent, in order to enhance compatibility with the above-mentioned semi-aromatic polyamide resin (A) or polystyrene resin (B).

The amount of fibrous filler in the polyamide resin composition is preferably 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 40% by mass or less, relative to the total mass of the polyamide resin composition. When the amount of fibrous filler is within this range, the rigidity of the polyamide resin composition tends to fall within the desired range. On the other hand, the toughness and other properties derived from the polyamide resin are more easily exhibited.

The polyamide resin composition may also contain fillers in shapes other than fibers. Specifically, examples of other fillers having shapes such as powder, granules, plates, needles, cloth, and mats include powdery 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, zinc oxide, and hydrotalcite; needle-like inorganic compounds such as potassium titanate; and organic particles. These fillers can be used alone or in combination of two or more.

The non-fibrous fillers may also be treated with a known surface treatment agent, such as a silane coupling agent, a titanium coupling agent, or an aluminate coupling agent, to enhance compatibility with the semi-aromatic polyamide resin (A) or polystyrene resin (B) described above.

The amount of fillers in a form other than fibers in the polyamide resin composition is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 35% by mass or less, based on the total mass of the polyamide resin composition. When the amount of these fillers is within this range, the mechanical strength of the polyamide resin composition tends to fall within the desired range.

The polyamide resin composition may further contain other polymers or any additives as necessary, as long as the effects of the invention are not impaired. Examples of other polymers include polyolefins such as polyethylene, polypropylene, poly-4-methyl-1-pentene, ethylene-1-butene copolymers, propylene-ethylene copolymers, propylene-1-butene copolymers, and polyolefin elastomers; polycarbonate; polyacetal; polysulfone; polyphenylene oxide; fluororesins; silicone resins; PPS (polyphenylene sulfide); LCP (liquid crystal polymer); Teflon (registered trademark); and the like. In addition to the above, modified polyolefins are also included, such as modified aromatic vinyl compound-conjugated diene copolymers or hydrogenated products thereof, such as modified polyethylene and modified SEBS, which are modified with carboxyl groups, acid anhydride groups, and amino groups, and modified polyolefin elastomers such as modified ethylene-propylene copolymers.

Examples of additives include antioxidants (phenols, amines, sulfurs, phosphorus compounds, etc.), heat stabilizers (lactone compounds, vitamin E compounds, hydroquinones, copper halides, iodine compounds, etc.), light stabilizers (benzotriazoles, triazines, benzophenones, benzoates, hindered amines, oxanilides, etc.), lubricants (waxes), fluorescent brighteners, plasticizers, thickeners, antistatic agents, release agents, pigments, crystal nucleating agents, and various other known additives.

The amount of additives in the polyamide resin composition is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less, relative to the total mass of the polyamide resin composition. When the amount of additives is within this range, the flowability, mechanical strength, and reflow heat resistance during molding of the polyamide resin composition can be improved.

Physical properties The physical properties of the polyamide resin composition are not particularly limited and are appropriately selected according to the application described below. For example, when the polyamide resin composition is used for electric/electronic components or surface mounting components, it is preferable that the composition has high reflow heat resistance, and particularly flame retardancy and flame resistance. Flame retardancy and flame resistance can be evaluated by the method specified in the Underwriters Laboratories Standard UL94 (UL Test No. UL94 dated June 18, 1991). The polyamide resin composition is processed into a test piece with a thickness of 0.8 mm, and a vertical flame test (flame retardancy test) is performed in accordance with the above standard, and the flame retardancy is preferably V-0.

- Method for Producing Polyamide Resin Composition The polyamide resin composition of this embodiment can be produced by a known method, for example, a method of mixing at least the above-mentioned semi-aromatic polyamide resin (A), polystyrene resin (B), flame retardant (C), and, if necessary, fillers and additives, etc., using a Henschel mixer, V blender, ribbon blender, tumbler blender, etc., or a method of mixing and then melt-kneading using a single-screw extruder, multi-screw extruder, kneader, Banbury mixer, etc., followed by granulation or pulverization. After mixing of each component, the components may be further melt-kneaded using a single-screw extruder, multi-screw extruder, kneader, Banbury mixer, etc., followed by granulation or pulverization.

Uses of the Polyamide Resin Composition The polyamide resin composition of the present embodiment can be molded into a molded product by a known molding method such as injection molding, extrusion molding, etc. The polyamide resin composition described above has good fluidity during molding, and is therefore suitable for injection molding and the like.

The polyamide resin composition of this embodiment is not particularly limited in its applications, but the polyamide resin composition has high mechanical strength and reflow heat resistance, and low water absorption. Therefore, it is very useful as an electric/electronic component or a surface mount component.

The present invention will be described below with reference to examples. The scope of the present invention is not to be construed as being limited by the examples.

1. Preparation of materials [Polyamide resin (A)]
PA6T/66: Semi-aromatic polyamide resin prepared in Synthesis Example 1 described later (6T/66=62.5 mol%/37.5 mol%, ratio of dicarboxylic acid components not having an aromatic ring to all dicarboxylic acid components=37.5 mol%)
PA6T/6I: Semi-aromatic polyamide resin prepared in Synthesis Example 2 described later (6T/6I=70%/30%, ratio of dicarboxylic acid components not having an aromatic ring to all dicarboxylic acid components=0 mol%)

[Polystyrene resin (B)]
PS1: Toyo Styrol GP G200C (manufactured by Toyo Styrol Co., Ltd., weight average molecular weight: 250,000)
PS2: Toyo Styrol GP MW1C (manufactured by Toyo Styrol Co., Ltd., weight average molecular weight: 370,000)
・PS3: Kristalex 5140 (manufactured by EASTMAN, weight average molecular weight 4,900)

[Flame retardant (C)]
Flame retardant (C): Brominated polystyrene (Albemarle, HP-3010, bromine content: 68% by mass, number average molecular weight (Mn): 3,400, weight average molecular weight (Mw): 4,000, Mw/Mn: 1.2)

[Flame retardant synergist (D)]
Sodium antimonate (SA-A, manufactured by Nippon Seiko Co., Ltd.)

[others]
・Glass fiber (manufactured by Central Glass Co., Ltd., ECS03-615)
Talc (Matsumura Sangyo Co., Ltd., High Filler #5000PJ)
Wax (Clariant Japan, Licomont CAV102)
m-SEBS (maleic SEBS, manufactured by Asahi Chemicals Corporation, Tuftec M1913)
・Hydrotalcite (Toda Kogyo Co., Ltd., NAOX-33)

[Synthesis Example 1]
2515g (15.1 mol%) of terephthalic acid, 2800g (24.1) of 1,6-diaminohexane, 1325g (9.0 mol) of adipic acid, 5.7g of sodium hypophosphite monohydrate and 554g of distilled water were placed in an autoclave with a capacity of 13.6L and substituted 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 3.01 MPa. After continuing the reaction for 1 hour, the low-order condensation product was discharged to the atmosphere from a spray nozzle installed at the bottom of the autoclave and extracted. The extracted low-order condensation product was cooled to room temperature, then pulverized to a particle size of 1.5 mm or less with a pulverizer, and dried at 110°C for 24 hours.

Next, this low-order condensate was placed in a tray-type solid-phase polymerization apparatus, and after nitrogen replacement, the temperature was raised to 220°C over approximately 1 hour and 30 minutes. The low-order condensate was then reacted for 1 hour and cooled to room temperature. The polyamide (high condensate) was then further melt-polymerized in a twin-screw extruder with a screw diameter of 30 mm and L/D = 36 at a barrel setting temperature of 330°C, a screw rotation speed of 200 rpm, and a resin supply rate of 6 kg/hour to obtain polyamide 6T/66 (semi-aromatic polyamide resin). The intrinsic viscosity [η] of polyamide 6T/66, measured by the method described below, was 0.8 dl/g, and the melting point (Tm) was 320°C.

[Synthesis Example 2]
2800g (24.3 mol) of 1,6-diaminohexane, 2841g (17.0 mol) of terephthalic acid, 1211g (7.3 mol) of isophthalic acid, 5.7g of sodium hypophosphite monohydrate, and 545g of distilled water were placed in an autoclave with a capacity of 13.6L and substituted 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 allowed to proceed for 1 hour in this state, and then the low-order condensation product was discharged into the atmosphere from a spray nozzle installed at the bottom of the autoclave and extracted. Thereafter, after cooling to room temperature, the low-order condensation product was pulverized to a particle size of 1.5 mm or less with a pulverizer and dried at 110°C for 24 hours.

Next, this low-order condensate was placed in a tray-type solid-phase polymerization apparatus, and after nitrogen replacement, the temperature was raised to 180°C over approximately 1 hour and 30 minutes. After that, the reaction was carried out for 1 hour and 30 minutes, and the temperature was lowered to room temperature. After that, the mixture was melt-polymerized in a twin-screw extruder with a screw diameter of 30 mm and L/D = 36 at a barrel setting temperature of 340°C, a screw rotation speed of 200 rpm, and a resin supply rate of 6 kg/hour to obtain polyamide 6T/6I (semi-aromatic polyamide resin). The intrinsic viscosity [η] of the polyamide 6T/6I measured by the method described below was 0.9 dl/g, and the melting point (Tm) was 330°C.

Example 1
The components in the mass ratios shown in Table 1 were mixed in a tumbler blender, and melt-kneaded in a twin-screw extruder (TEX30α manufactured by Japan Steel Works, Ltd.) with the cylinder temperature set to the melting point (Tm) of polyamide resin (A-1) + 15°C. The molten mixture was extruded in the form of strands and cooled in a water tank. The strands were then taken up in a pelletizer and cut to obtain a pellet-shaped polyamide resin composition.

<Examples 2 to 5, Comparative Examples 1 to 6>
Pellet-shaped polyamide resin compositions were obtained in the same manner as in Example 1, except that the composition was changed as shown in Table 1.

<Evaluation method>
The intrinsic viscosity and melting point of the polyamide resin (A) were measured by the following methods. The resulting polyamide resin composition was evaluated for bending strength, toughness, flow length, water absorption, reflow heat resistance, and flame retardancy by the following methods. The results are shown in Table 1.

- Intrinsic viscosity [η]
In accordance with JIS K6810-1977, 0.5 g of polyamide resin was dissolved in 50 ml of 96.5% sulfuric acid solution, and the number of seconds it took for the sample solution to flow down was measured using an Ubbelohde viscometer under conditions of 25±0.05° C. From the measurement results, the intrinsic viscosity [η] of the polyamide resin was calculated according to the following formula.
[η]=ηSP/[C(1+0.205ηSP)]
ηSP=(t-t0)/t0
[η]: Intrinsic viscosity (dl/g)
ηSP: Specific viscosity C: Sample concentration (g/dl)
t: number of seconds for sample solution to flow (seconds)
t0: Number of seconds (seconds) for blank sulfuric acid to flow

Melting point (Tm)
The polyamide resin was heated using a PerkinElmer DSC7, held at 340° C. for 5 minutes, cooled to 23° C. at a rate of 10° C./min, and then heated at 10° C./min. The endothermic peak due to melting at this time was taken as the melting point of the polyamide resin.

Bending strength and toughness: A test piece having a length of 64 mm, a width of 6 mm and a thickness of 0.8 mm was prepared by injection molding. The molding machine used, the cylinder temperature of the molding machine and the mold temperature are shown below.
Molding machine: Sodick Plastic, Tupearl TR40S3A
Molding machine cylinder temperature: Melting point of polyamide resin + 10°C
Mold temperature: 120°C

The prepared test specimens were left at 23°C in a nitrogen atmosphere for 24 hours. Then, a bending test was performed using a bending tester (NTESCO AB5) in an atmosphere of 23°C and 50% relative humidity. The test conditions were a span of 26 mm and a bending speed of 5 mm/min. From the bending test, the bending strength, strain, elastic modulus, and the energy required to break the test specimen (toughness) were measured.

・Flow length test (fluidity)
The polyamide resin composition was injected into a bar flow mold having a width of 10 mm and a thickness of 0.5 mm under the following conditions, and the flow length (mm) of the resin in the mold was measured.
Injection molding machine: Sodick, Tupearl TR40S3A
Injection pressure setting: 2000 kg/ ^cm2
Cylinder temperature setting: melting point of each polyamide resin + 10℃
Mold temperature: 120°C

Measurement of Water Absorption and Reflow Heat Resistance Temperature The polyamide resin composition was injection molded under the following conditions to prepare a test piece having a length of 64 mm, a width of 6 mm and a thickness of 0.8 mm.
Molding machine: Sodick, Tupearl TR40S3A
Molding machine cylinder temperature: Melting point of each polyamide resin + 10°C
Mold temperature: 100°C
The prepared test piece was conditioned at a temperature of 40° C. and a relative humidity of 95% for 96 hours. The water absorption rate was calculated from the change in weight of the test piece before and after conditioning.

The test piece that had been subjected to the humidity conditioning treatment was placed on a glass epoxy board with a thickness of 1 mm. A temperature sensor was installed on this board. The glass epoxy board on which the test piece was placed was set in an air reflow soldering device (AIS-20-82-C manufactured by Atec Techtron Co., Ltd.) and the reflow process was performed with the temperature profile shown in Figure 1. As shown in Figure 1, the temperature was raised to 230°C at a predetermined speed. Next, the test piece was heated to a predetermined set temperature (a: 270°C, b: 265°C, c: 260°C, d: 255°C, e: 235°C) in 20 seconds, and then cooled to 230°C. At this time, the maximum set temperature at which the test piece did not melt and blisters did not occur on the surface was determined, and this maximum set temperature was taken as the reflow heat resistance temperature. The reflow heat resistance temperature of the test piece that had absorbed moisture tends to be lower than that of the test piece in an absolutely dry state.

Flammability Test The polyamide resin compositions produced in the Examples and Comparative Examples were injection molded under the following conditions to prepare test pieces with a width of 13 mm, a length of 125 mm, and a thickness of 0.8 mm. Using the prepared test pieces, a vertical flame test was performed in accordance with the UL94 standard (UL Test No. UL94 dated June 18, 1991) to evaluate the flame retardancy. The evaluation was performed based on the criteria described in the standard.
Molding machine: Sodick, Tupearl TR40S3A
Molding machine cylinder temperature: Melting point of each polyamide resin + 10°C
Mold temperature: 120°C

As shown in Table 1 above, when polystyrene resin (B) having a molecular weight of 100,000 or more was simply added to a polyamide resin composition containing polyamide resin 6T/66 (when no flame retardant (C) was included), the flow length was short and the water absorption rate was relatively high at 2.5 mass% (Comparative Example 6). In addition, the reflow heat resistance temperature was low and the flame retardancy was unacceptable.

On the other hand, when flame retardant (C) was simply added to a polyamide resin composition containing polyamide resin 6T/66 (when polystyrene resin (B) was not included), the flame retardancy and reflow heat resistance temperature were improved, but the fluidity (flow length) during molding was insufficient (Comparative Example 1).

In contrast, when a polyamide resin composition containing polyamide 6T/66 as polyamide (A) was added with polystyrene resin (B) having a molecular weight of 100,000 or more and flame retardant (C), the flow length was increased, and the reflow heat resistance temperature and heat resistance were improved (for example, Examples 1 to 4). The toughness was also relatively good. However, when the amount of polystyrene resin (B) relative to the total mass of the polyamide resin and polystyrene resin was 10 mass% or more, the reflow heat resistance temperature was significantly reduced, and the flame retardancy and toughness were also reduced (Comparative Examples 2 and 3). The same results were obtained when polyamide 6T/6I was used as polyamide (A) (Comparative Example 4, Example 5). When a polystyrene resin having a molecular weight of less than 100,000 was added, the flow length was short and the water absorption rate was likely to be high (Comparative Example 4). Furthermore, in this case, the toughness was very low even when the amount added was small.

The present invention provides a polyamide resin composition that has high mechanical strength, reflow heat resistance, and low water absorption. Therefore, it is very useful in various applications such as industrial materials, automobiles, electrical and electronic products, and industrial applications.

Claims (8)

A polyamide resin (A),
A polystyrene resin (B) having a weight average molecular weight of 100,000 or more;
A flame retardant (C);
Including,
The content of the polystyrene resin (B) is less than 10% by mass based on the total mass of the polyamide resin (A) and the polystyrene resin (B);
Polyamide resin composition. The polyamide resin (A) contains a dicarboxylic acid component unit (Aa) derived from a dicarboxylic acid and a diamine component unit (Ab) derived from a diamine,
At least one of the dicarboxylic acid component unit (Aa) and the diamine component unit (Ab) contains a component unit having an aromatic ring.
The polyamide resin composition according to claim 1. at least one of the dicarboxylic acid component unit (Aa) and the diamine component unit (Ab) contains a component unit having an aromatic ring and a component unit not having an aromatic ring,
With respect to at least one of the dicarboxylic acid component unit (Aa) and the diamine component unit (Ab), the number of moles of the component unit not having an aromatic ring is 30 mol % or more and 70 mol % or less with respect to the total number of moles of the component unit having an aromatic ring and the component unit not having an aromatic ring.
The polyamide resin composition according to claim 2. The polyamide resin (A) contains a dicarboxylic acid component unit (Aa) derived from a dicarboxylic acid and a diamine component unit (Ab) derived from a diamine,
The dicarboxylic acid component unit (Aa) includes a component unit derived from terephthalic acid and a component unit derived from an aliphatic dicarboxylic acid having 4 to 15 carbon atoms.
The polyamide resin composition according to claim 1. the number of moles of the component units derived from the aliphatic dicarboxylic acid having 4 to 15 carbon atoms is 30 mol % or more and 70 mol % or less based on the total number of moles of the dicarboxylic acid component units (Aa);
The polyamide resin composition according to claim 4. the diamine component unit (Ab) contains 80 mol % or more and 100 mol % or less of component units derived from an aliphatic diamine having 4 to 15 carbon atoms;
The polyamide resin composition according to claim 5. the component unit derived from an aliphatic dicarboxylic acid having 4 to 15 carbon atoms is a component unit derived from adipic acid,
The component unit derived from an aliphatic diamine having 4 to 15 carbon atoms is a component unit derived from 1,6-diaminohexane.
The polyamide resin composition according to claim 6. When the test piece had a thickness of 0.8 mm and the flame retardancy test was conducted in accordance with the UL94 standard, the flame retardancy was V-0.
The polyamide resin composition according to claim 1.

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