JP6712178B2 - Polyamide resin composition and method for improving chemical resistance - Google Patents

Description

The present invention relates to a polyamide resin composition having excellent chemical resistance and a method for improving chemical resistance.

Polyamide resin has excellent mechanical properties (mechanical strength, rigidity, impact resistance, etc.), heat resistance, and chemical resistance, so it can be used for clothing, industrial materials, automobiles, electrical and electronic parts, and other industrial products. It is used in various industrial fields.

As for materials used for automobile engine rooms, recently, assuming use in cold regions, suppression of deterioration of resin due to calcium chloride, which is an antifreezing agent, and long-life coolant (LLC), which is an antifreeze liquid for cooling system parts, is used. There is a high demand for suppression of resin deterioration due to (1). Polyamide resins are required to have calcium chloride resistance and hydrolysis resistance as described above when used for parts related to automobile engine rooms.

As a technique for improving the calcium chloride resistance and the hydrolysis resistance of a polyamide resin, a polyamide having a long carbon chain (long-chain polyamide; a polyamide having a large proportion of methylene chains to amide bonds) has been conventionally known.

On the other hand, long-chain polyamide has a low melting point, and therefore, a mixture with polyamide 66 or the like has been disclosed in order to improve heat resistance (see, for example, Patent Documents 1 to 3).

JP-A-60-88066 JP, 2008-144132, A Special table 2013-523930 gazette

It is an object of the present invention to provide a polyamide resin composition having excellent chemical resistance, which is suitable for parts used in an automobile engine room, and a method for improving chemical resistance. is there.

As a result of intensive studies to solve the above problems, the present inventors have found that the melting point is 240° C. or lower and the polyamide having a carbon number/nitrogen number ratio (C/N ratio) of 7 or more and a melting point of A polyamide resin composition containing a polyamide having a carbon number/nitrogen number ratio (C/N ratio) of 240° C. or higher and a C/N ratio of less than 7 has a melting point in a specific temperature range and a crystallization peak temperature of 1 It was found that a polyamide resin composition having excellent chemical resistance can be obtained by using the above method, and the present invention has been completed.

That is, the polyamide resin composition of the present invention has a melting point of 240° C. or lower, a carbon number/nitrogen number ratio (C/N ratio) of 7 or more, and a melting point of 240° C. or more. A polyamide resin composition comprising a polyamide (B) having a carbon number/nitrogen number ratio (C/N ratio) of less than 7, wherein the polyamide resin composition has at least one melting point below 240°C. , 240° C. or higher, and at least one crystallization peak temperature.

The polyamide (A) preferably contains 50 mol% or more of a unit composed of an aliphatic diamine and an aliphatic dicarboxylic acid and/or a unit composed of an ω-aliphatic aminocarboxylic acid.
The polyamide (A) is one or more selected from the group consisting of polyamide 410, polyamide 412, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide 1010, polyamide 1012, and copolyamides containing these as constituent components. Is preferred.

The polyamide (B) preferably contains 50 mol% or more of a unit composed of an aliphatic diamine and an aliphatic dicarboxylic acid.
The polyamide (B) is preferably one or more selected from the group consisting of polyamide 46, polyamide 56, polyamide 66, and a copolyamide containing these as constituent components.

The crystallization peak temperature of the polyamide resin composition is equal to or higher than the crystallization peak temperature of the polyamide (A) and is preferably equal to or lower than the crystallization peak temperature of the polyamide (B).
It is preferable that 30 to 70 mass% of polyamide (A) and 30 to 70 mass% of polyamide (B) are contained with respect to 100 mass% of polyamide.

The method for improving the chemical resistance of the present invention comprises adding the polyamide resin composition of the present invention to a polyamide resin to improve the chemical resistance of the polyamide resin composition.

According to the present invention, a polyamide resin composition having excellent chemical resistance can be provided.

The present invention will be specifically described below.
First, each component that can be used in the present invention will be described in detail.

[polyamide]
The polyamide resin composition of the present invention includes a polyamide (A) having a melting point of 240° C. or lower and a carbon number/nitrogen number ratio (C/N ratio) of 7 or more. By containing such a polyamide (A), it tends to have excellent chemical resistance. The carbon number/nitrogen number ratio (C/N ratio) of the polyamide (A) is 7 or more, preferably 8 or more. The upper limit of the carbon number/nitrogen number ratio (C/N ratio) is not particularly limited, but is preferably 15 or less, more preferably 12 or less, still more preferably 10 or less. When the carbon number/nitrogen number ratio is within the above range, the chemical resistance and the heat resistance tend to be more excellent. The C/N ratio of the copolyamide can be determined as an average value calculated from the molar ratio of the copolymerization ratio.

The content of the polyamide (A) is preferably 30 to 70 mass% with respect to 100 mass% of the polyamide contained in the polyamide resin composition. It is more preferably 35 to 65% by mass, and further preferably 40 to 60% by mass. When the content is within the above range, the chemical resistance tends to be more excellent.

The melting point is a value measured by differential scanning calorimetry (DSC) according to JIS K7121. Specifically, it is the melting peak temperature when heated at a heating rate of 20° C./min. The melting point can be measured by DSC7 (manufactured by Perkin Elmer) or the like. Hereinafter, the meaning of the melting point and the measuring method are the same in this specification.

The melting point of the polyamide (A) is 240° C. or lower, preferably 150 to 240° C., more preferably 180 to 240° C., and further preferably 190 to 230° C. When the melting point is within the above range, the chemical resistance, moldability and appearance tend to be more excellent.

The polyamide resin composition of the present invention includes a polyamide (B) having a melting point of 240° C. or higher and a carbon number/nitrogen number ratio (C/N ratio) of less than 7. By including such a polyamide (B), it tends to be excellent in mechanical strength and thermal rigidity. The carbon number/nitrogen number ratio (C/N ratio) of the polyamide (B) is preferably 4 or more and less than 7, and more preferably 5 or more and less than 7. The C/N ratio of the copolyamide can be obtained as an average value calculated from the molar ratio of the copolymerization ratio as the C/N ratio as in the case of the polyamide (A).

The content of the polyamide (B) is preferably 30 to 70 mass% with respect to 100 mass% of the polyamide contained in the polyamide resin composition. It is more preferably 35 to 65% by mass, and further preferably 40 to 60% by mass. When the content is within the above range, the rigidity during heating tends to be more excellent.

The melting point of the polyamide (B) is 240° C. or higher, preferably 240 to 320° C., more preferably 240 to 300° C., and further preferably 250 to 280° C. When the melting point is within the above range, the mechanical strength, the rigidity under heat, and the moldability tend to be excellent.

Polyamide means a polymer compound having a -CO-NH-(amide) bond in the main chain. The polyamide (A) and the polyamide (B) are obtained by condensing (a) a polyamide obtained by ring-opening polymerization of a lactam, (b) a polyamide obtained by self-condensation of ω-aminocarboxylic acid, (c) a diamine and a dicarboxylic acid. It may be a polyamide obtained by doing so, or a copolymer thereof.

The lactam as the raw material of the above (a) polyamide is not particularly limited, but examples thereof include pyrrolidone, caprolactam, undecalcactam, and dodecalcactam.

In addition, the ω-aminocarboxylic acid that is a raw material of the polyamide resin (b) is not particularly limited, and examples thereof include ω-amino fatty acid which is a ring-opening compound of lactam with water. The above-mentioned (a) polyamide and (b) polyamide may be those obtained by condensing two or more kinds of lactams or ω-aminocarboxylic acids in combination.

The diamine (monomer) as a raw material of the above-mentioned (c) polyamide is not particularly limited, but for example, a linear aliphatic diamine such as hexamethylenediamine or pentamethylenediamine; 2-methylpentanediamine or 2- Examples thereof include branched aliphatic diamines such as ethylhexamethylenediamine; aromatic diamines such as p-phenylenediamine and m-phenylenediamine; alicyclic diamines such as cyclohexanediamine, cyclopentanediamine and cyclooctanediamine.

On the other hand, the dicarboxylic acid (monomer) as a raw material of the above-mentioned (c) polyamide is not particularly limited, but for example, aliphatic dicarboxylic acids such as adipic acid, pimelic acid and sebacic acid; phthalic acid and isophthalic acid, etc. Aromatic dicarboxylic acids; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and the like.
The above-mentioned (c) polyamide may be obtained by condensing one kind alone or two or more kinds of diamine and dicarboxylic acid in combination.

The polyamide (A) preferably contains 50 mol% or more of a unit composed of an aliphatic diamine and an aliphatic dicarboxylic acid and/or a unit composed of an ω-aliphatic aminocarboxylic acid. It is more preferably 60 mol% or more, further preferably 80 mol% or more, particularly preferably 90 mol% or more, and most preferably 100 mol%. When the units composed of these aliphatic compounds are within the above range, the toughness and moldability tend to be more excellent.

Although the polyamide (A) is not particularly limited, for example, polyamide 410 (polytetramethylene sebacamide), polyamide 412 (polytetramethylene dodecamide), polyamide 610 (polyhexamethylene sebacamide), polyamide 612 (polyamide) Hexamethylene dodecamide), polyamide 11 (polyundecane amide), polyamide 12 (polydodecane amide), polyamide 1010 (polydecamethylene sebacamide), polyamide 1012 (polydecamethylene dodecamide), and these as constituent components One or more selected from the group consisting of copolyamides may be mentioned. Among them, one or more selected from the group consisting of polyamide 410, polyamide 412, polyamide 610, polyamide 612, and copolyamide containing these as constituent components is preferable, and it is composed of polyamide 410, polyamide 412, polyamide 610, and polyamide 612. More preferably, at least one selected from the group. When it is at least one selected from these groups, it tends to be more excellent in chemical resistance, moldability and appearance.

The polyamide (B) preferably contains 50 mol% or more of a unit composed of an aliphatic diamine and an aliphatic dicarboxylic acid. It is more preferably 60 mol% or more, further preferably 80 mol% or more, particularly preferably 90 mol% or more, and most preferably 100 mol%. When the units composed of these aliphatic compounds are within the above range, the toughness and moldability tend to be more excellent.

The polyamide (B) is not particularly limited, and examples thereof include polyamide 4 (poly α-pyrrolidone), polyamide 6 (polycaproamide), polyamide 46 (polytetramethylene adipamide), polyamide 56 (polypentamethylene adipamide). Amide), polyamide 66 (polyhexamethylene adipamide), and one or more selected from the group consisting of copolyamides containing these as constituent components. Among them, one or more selected from the group consisting of polyamide 46, polyamide 56, polyamide 66, and a copolyamide containing these as constituent components is preferable, and one selected from the group consisting of polyamide 46, polyamide 56, and polyamide 66 More than one kind is more preferable. By being one or more selected from these groups, the mechanical strength, the rigidity at the time of heat, and the moldability tend to be excellent.

The polyamide resin composition of the present invention may contain a polyamide other than the above polyamide (A) and polyamide (B), and the polyamide other than the polyamide (A) and the polyamide (B) is not particularly limited, but for example, , Polyamide 6T (polyhexamethylene terephthalamide), polyamide 9T (polynonane methylene terephthalamide), polyamide 6I (polyhexamethylene isophthalamide), and copolyamides containing these as constituents.

The terminal group of the polyamide used in the present invention is not particularly limited, but generally has an amino group or a carboxyl group. The ratio of the amount of amino end groups to the total amount of amino end groups and the amount of carboxyl end groups in the polyamide used in the present invention [amount of amino end groups/(amount of amino end groups+amount of carboxyl end groups)] is 0.3 or more and 1 It is preferably less than 0.0, more preferably 0.3 or more and 0.8 or less, still more preferably 0.3 or more and 0.6 or less. When the ratio of the amount of terminal groups is within the above range, the molded product obtained from the polyamide resin composition tends to have more excellent color tone, mechanical strength, and vibration fatigue resistance.

The amount of amino terminal groups of the polyamide is preferably 10 to 100 μmol/g, more preferably 15 to 80 μmol/g, and further preferably 30 to 80 μmol/g. When the amount of amino terminal groups is within the above range, the mechanical strength of the polyamide resin composition tends to be more excellent.

Here, as an example of the method for measuring the amount of amino terminal groups and the amount of carboxyl terminal groups in the present specification, ¹ H-NMR method and titration method can be mentioned. ^{In the 1} H-NMR method, it can be determined by the integrated value of the characteristic signal corresponding to each terminal group. In the titration method, for amino end groups, a method of titrating a polyamide resin phenol solution with 0.1N hydrochloric acid, and for carboxyl end groups, a method of titrating a polyamide resin benzyl alcohol solution with 0.1N sodium hydroxide, etc. Is mentioned.

Furthermore, as a method for adjusting the concentration of the terminal group of the polyamide used in the present invention, a known method can be used. The adjusting method is not particularly limited, and examples thereof include a method using an end adjuster. As a specific example, one or more end modifiers selected from the group consisting of a monoamine compound, a diamine compound, a monocarboxylic acid compound, and a dicarboxylic acid compound are added so that a predetermined terminal concentration is obtained during polymerization of polyamide. Is mentioned. The timing of adding the terminal adjuster to the solvent is not particularly limited as long as it functions as the terminal adjuster, and may be, for example, when the above-mentioned polyamide raw material is added to the solvent.

The monoamine compound is not particularly limited, and examples thereof include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine and dibutylamine. Alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine and naphthylamine, and any mixture thereof. Among them, butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferable from the viewpoints of reactivity, boiling point, stability of sealing end, price, and the like. These may be used alone or in combination of two or more.

The diamine compound is not particularly limited, but is, for example, a linear aliphatic diamine such as hexamethylenediamine or pentamethylenediamine; a branched aliphatic diamine such as 2-methylpentanediamine or 2-ethylhexamethylenediamine; Examples thereof include aromatic diamines such as p-phenylenediamine and m-phenylenediamine; alicyclic diamines such as cyclohexanediamine, cyclopentanediamine and cyclooctanediamine. These may be used alone or in combination of two or more.

The monocarboxylic acid compound is not particularly limited, for example, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecyl acid, myristic acid, palmitic acid, stearic acid, pivalic acid and isobutyl. Aliphatic monocarboxylic acids such as acids; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatics such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid and phenylacetic acid Examples include monocarboxylic acid. In the present invention, these carboxylic acid compounds may be used alone or in combination of two or more.

The dicarboxylic acid compound is not particularly limited, and examples thereof include malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, and 2,2-dimethylglutaric acid. Aliphatic dicarboxylic acids such as 3,3-diethylsuccinic acid, azelaic acid, sebacic acid and suberic acid; alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; isophthalic acid 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, diphenic acid, diphenylmethane- Examples include units derived from aromatic dicarboxylic acids such as 4,4′-dicarboxylic acid, diphenylsulfone-4,4′-dicarboxylic acid and 4,4′-biphenyldicarboxylic acid. These may be used alone or in combination of two or more.

According to ISO 307, the polyamide used in the present invention has a viscosity number (VN) measured with 96% (mass fraction) sulfuric acid of 100 to 180 ml/g for mechanical strength and injection molding. It is preferable from the viewpoints of fluidity and appearance. More preferably, it is 110 to 150 ml/g.

[Polyamide resin composition]
The polyamide resin composition of the present invention has at least one melting point below 240°C and at least one melting point above 240°C, and has one crystallization peak temperature.
Like the melting point, the crystallization peak temperature is a value measured by differential scanning calorimetry (DSC) according to JIS K7121, and specifically, the crystallization peak temperature when cooled at a cooling rate of 20° C./min. That is.

The melting point of the polyamide resin composition is preferably at least one at 150 to 238°C, and at least one at 240 to 320°C, at least one at 180 to 235°C, and at least one at 240 to 300°C. More preferably, at least one at 180 to 235° C., at least one at 240 to 280° C., even more preferably at least one at 190 to 230° C., particularly preferably at least one at 240 to 280° C. .. When at least two melting points are within the above ranges, the mechanical strength, the rigidity at heat, the chemical resistance, and the moldability tend to be excellent.

The crystallization peak temperature of the polyamide resin composition is not particularly limited, but is preferably 150 to 240°C, more preferably 160 to 220°C, and further preferably 170 to 200°C. When the crystallization peak temperature is within the above range, the chemical resistance and the moldability tend to be more excellent. Further, when the crystallization peak temperature is one within the above range, the chemical resistance and the hydrolysis resistance tend to be more excellent.
Further, the crystallization peak temperature of the polyamide resin composition is equal to or higher than the crystallization peak temperature of the polyamide (A) and is equal to or lower than the crystallization peak temperature of the polyamide (B), which is excellent in chemical resistance and moldability. It is preferable because it tends to occur.

[Method for producing polyamide resin composition]
As a method for producing the polyamide resin composition, a method of kneading the polyamide in a molten state by a single-screw or multi-screw extruder can be used. When an extruder is used, the polyamide resin composition of the present invention can be produced by adjusting the processing temperature or residence time, or by using phosphite ester or metal phosphite. For example, the polyamide (A) and the polyamide (B) are produced by adjusting the processing temperature to 290 to 350° C. and adjusting the average residence time to 2 to 10 minutes to produce at least one melting point. There is a tendency that a polyamide resin composition having a single crystallization peak temperature and having a single crystallization peak temperature is obtained. The polyamide resin composition of the present invention is more likely to be obtained as the processing temperature is higher, and as the average residence time is longer. On the other hand, by using phosphite ester or metal phosphite, even if the average residence time is short, the polyamide resin composition of the present invention is easily obtained, for example, even if the average residence time is less than 2 minutes, The polyamide resin composition of the present invention can be obtained.

Examples of the phosphite include ethyl phosphate, diethyl phosphate, dipropyl phosphate, dibutyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, tris(2 -Ethylhexyl) phosphate, triphenyl phosphate, diphenyl cresyl phosphate, tricresyl phosphate, biphenyl phosphate, tris(2,4-di-t-butylphenyl) phosphate, tris(1,5-di-t-butylphenyl) , Tris(dimethylphenyl), tris(isopropylphenyl)phosphate, octyldiphenylphosphate, or mixtures thereof.

Examples of the metal phosphite include phosphorous acid, hypophosphorous acid, and elements of groups 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13 of the periodic table of elements and tin, Examples thereof include metal salts with lead and the like. These metal phosphites may be used alone or in combination of two or more.
The content of these phosphite esters and metal phosphite is preferably 0.05 to 10 parts by mass, more preferably 0. 0 parts by mass with respect to 100 parts by mass of the polyamide contained in the polyamide resin composition. It is 1 to 5 parts by mass, more preferably 0.1 to 2.5 parts by mass.

[Uses of polyamide resin composition]
The polyamide resin composition of the present invention may be used as it is, but for example, it may be used by adding it when compounding a polyamide resin and an inorganic filler such as glass fiber, chemical resistance and mechanical strength. It is preferable because a polyamide resin composition having excellent rigidity when heated can be obtained. When the polyamide resin composition of the present invention is added to the polyamide resin, the proportion is preferably 5 to 95% by mass, more preferably 10 to 90% by mass, and further preferably 10 to 60% by mass with respect to 100% by mass of the polyamide resin. preferable.

Examples of additional components are given below.
Inorganic fillers such as glass fiber, antioxidants, ultraviolet absorbers, heat stabilizers, photodegradation inhibitors, plasticizers, lubricants, mold release agents, nucleating agents, flame retardants, colorants, etc. can also be added. Alternatively, other thermoplastic resins may be blended.

The lubricant is not particularly limited, and examples thereof include fatty acid metal salts, fatty acid esters, fatty acid amides, polyethylene wax and the like. From the viewpoints of excellent appearance and moldability, at least one selected from fatty acid metal salts, fatty acid esters, and fatty acid amides is preferable, and it is more preferable to use two or more types in combination, and the fatty acid metal salt and fatty acid ester are used in combination. Is more preferable.
The colorant is not particularly limited, but examples thereof include carbon black, titanium oxide, and azine dyes.

The composition thus obtained can be molded by various conventionally known methods, for example, injection molding into molded articles of various parts.
As these various parts, for example, they can be suitably used for automobiles, machine industry, electricity and electronics, industrial materials, industrial materials, daily use and household products.
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to those shown in the Examples.

(Used raw materials)
(1) Polyamide (1-1) Polyamide 610 (hereinafter abbreviated as PA-1)
Melting point: 220°C, crystallization peak temperature: 180°C
VN (sulfuric acid): 115 ml/kg, amino terminal group: 40 mmol/kg,
Carboxylic acid end group: 60 mmol/kg
(1-2) Polyamide 66 (hereinafter abbreviated as PA-2)
Melting point: 260°C, crystallization peak temperature: 215°C
VN (sulfuric acid): 145 ml/kg, amino end group: 50 mmol/kg,
Carboxylic acid end group: 80 mmol/kg

(2) Glass fiber Glass fiber having an average fiber diameter of 10 μm (hereinafter abbreviated as GF)
(3) Heat stabilizer A mixture of copper iodide (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter abbreviated as CuI) and potassium iodide (Wako Pure Chemical Industries, Ltd., hereinafter abbreviated as KI) at a mass ratio of 1:5 ( (Hereinafter, abbreviated as HS)
(4) Lubricant (4-1) Calcium montanate (hereinafter abbreviated as WAX-1)
(4-2) montanic acid ester (hereinafter abbreviated as WAX-2)

(Evaluation method)
The evaluation method will be described below.
<Chemical resistance (formic acid solubility)>
The polyamide resin composition pellets obtained in Examples and Comparative Examples were injection-molded [PS-40E: manufactured by Nissei Plastic Co., Ltd.] using injection + pressure holding time of 10 seconds, cooling time of 15 seconds, and mold temperature. The temperature was set to 80° C. and the temperature of the molten resin was 290° C., and strip-shaped molded pieces of 125×12.5×3 mm were molded. After immersing the obtained molded piece in 90% formic acid for 30 minutes, it was determined whether the surface was whitened.

<Chemical resistance (calcium chloride resistance)>
The polyamide resin composition pellets obtained in Production Examples and Comparative Production Examples were injection-molded [PS-40E: manufactured by Nissei Resin Co., Ltd.] using an injection + pressure holding time of 10 seconds, a cooling time of 15 seconds, and a mold. The temperature was set to 80° C. and the molten resin temperature was set to 290° C., and a flat plate type molded piece of 130×130×3 mm was molded. Next, a test piece was obtained by cutting from the center of the flat plate in the direction perpendicular to the flow (direction perpendicular to the axis from the gate of the molded product to the end of the flow direction) into a strip of 130×10×3 mm. The obtained test piece was allowed to absorb water in water at 80° C. for 100 hours. After that, 1) wrap the test piece with gauze, 2) impregnate the gauze with a 40 mass% calcium chloride aqueous solution, 3) apply a load with a cantilever bending stress of 20 MPa, leave it for 1 hour, and 4) put it in an oven at 100°C. It was exposed for 2 hours, 5) the gauze was removed, it was cooled at room temperature for 1 hour, and 6) the presence or absence of cracks was visually confirmed. The cycles 1) to 6) were repeated until cracks were observed on the surface of the test piece, and the number of cycles at which cracks began to be observed was evaluated.

[Example 1]
L/D (cylinder length of extruder/cylinder diameter of extruder)=48 (number of barrels: 12) twin-screw extruder [ZSK-26MC: Coperion (Germany)] is used for upstream supply The temperature from the mouth to the die was set to 300° C., the screw rotation speed was 150 rpm, the discharge rate was 10 kg/h, and PA-1 was supplied at a ratio of 50 parts by mass and PA-2 at a ratio of 50 parts by mass from the upstream supply port and melted. The mixture was kneaded, and a polyamide resin composition (a-1) was obtained with an average residence time of 3 minutes. The obtained polyamide resin composition (a-1) had two melting points of 221° C. and 258° C., and a crystallization peak temperature of 187° C. When tested for chemical resistance, no whitening was observed and the surface was not attacked by formic acid.

[Example 2]
L/D (cylinder length of extruder/cylinder diameter of extruder)=48 (number of barrels: 12) twin-screw extruder [ZSK-26MC: Coperion (Germany)] is used for upstream supply The temperature from the mouth to the die was set to 300° C., the screw rotation speed was 300 rpm, the discharge rate was 25 kg/h, 50 parts by mass of PA-1 and 50 parts by mass of PA-2, and tris(2,4-di-t-butyl). 0.2 parts by mass of phenyl)phosphate and 0.2 parts by mass of calcium hypophosphite are supplied from the upstream supply port and melt-kneaded, and the polyamide resin composition (a-2) is obtained with an average residence time of 1 minute. Obtained. The obtained polyamide resin composition (a-2) had two melting points of 221° C. and 258° C., and a crystallization peak temperature of 185° C. When tested for chemical resistance, no whitening was observed.

[Comparative Example 1]
L/D (cylinder length of extruder/cylinder diameter of extruder)=48 (number of barrels: 12) twin-screw extruder [ZSK-26MC: Coperion (Germany)] is used for upstream supply The temperature from the mouth to the die was set to 280° C., the screw rotation speed was 300 rpm, the discharge rate was 25 kg/h, PA-1 was 50 parts by mass and PA-2 was 50 parts by mass from the upstream side supply port to be melted. The mixture was kneaded, and a polyamide resin composition (a-3) was obtained with an average residence time of 1 minute. The obtained polyamide resin composition (a-3) had two melting points of 220°C and 260°C and two crystallization peak temperatures of 215°C and 181°C. When the chemical resistance was tested, whitening was observed and the surface was attacked by formic acid.

[Comparative example 2]
Using an autoclave with an internal volume of 5.4 L [manufactured by Nitto High Pressure Co., Ltd.], PA-1 was heated at a ratio of 50 parts by mass and PA-2 at a ratio of 50 parts by mass under a nitrogen atmosphere at 300° C. for 1 hour to obtain a polyamide resin. A composition (a-4) was obtained. The obtained polyamide resin composition (a-4) had a melting point of 194°C and a crystallization peak temperature of 133°C. When tested for chemical resistance, whitening was observed.
Table 1 shows the compositions, production conditions, melting points, etc. of the polyamide resin compositions of Examples and Comparative Examples. As shown in Table 1, the polyamide resin composition of the present invention was excellent in chemical resistance.

[Production Examples 1 to 4, Comparative Production Examples 1 to 5]
L/D (the extruder cylinder has an upstream supply port on the first barrel from the upstream side of the extruder, a downstream supply port on the ninth barrel, and a vacuum devolatilization port on the eleventh barrel). Length/cylinder diameter of extruder) = 48 (number of barrels: 12) twin-screw extruder [ZSK-26MC: made by Coperion (Germany)] and set the temperature from the upstream supply port to the die at 290°C. Then, at a screw rotation speed of 300 rpm and a discharge rate of 25 kg/h, the polyamide, the polyamide resin composition of Example 1 or 2 or Comparative Example 1 or 2 was heat-stabilized from the upstream supply port so that the ratios shown in Table 2 were obtained. An agent and a lubricant were supplied, glass fiber chopped strands were supplied from the downstream supply port, and the resin composition pellets were prepared by melt kneading under reduced pressure from the vacuum devolatilization port. The obtained resin composition was molded at a resin temperature of 290° C. and a mold temperature of 80° C., and the chemical resistance was evaluated. The physical properties are shown in Table 2 together with the composition.

As shown in Table 2, the polyamide resin compositions of Production Examples 1 to 4 using the polyamide resin composition of the present invention were dramatically excellent in chemical resistance. Therefore, the polyamide resin composition of the present invention can improve the chemical resistance of the polyamide resin even when added to other polyamide resins.

Since the polyamide resin composition of the present invention has excellent chemical resistance, it can be suitably used as a molded article requiring mechanical strength and chemical resistance such as an automobile underhood part.

Claims (7)

A method for improving the chemical resistance of the polyamide resin by adding the polyamide resin composition to the polyamide resin,
As the polyamide resin composition , a polyamide (A) having a melting point of 240° C. or less and a carbon number/nitrogen number ratio (C/N ratio) of 7 or more, and a melting point of 240° C. or more and carbon number/ A polyamide resin composition comprising a polyamide (B) having a nitrogen number ratio (C/N ratio) of less than 7, wherein the polyamide resin composition has at least one melting point below 240°C and 240°C. A method for improving chemical resistance using a polyamide resin composition having at least one melting point and one crystallization peak temperature as described above . The chemical resistance according to claim 1, wherein the polyamide (A) contains 50 mol% or more of a unit composed of an aliphatic diamine and an aliphatic dicarboxylic acid and/or a unit composed of an ω-aliphatic aminocarboxylic acid. How to improve sex . The polyamide (A) is one selected from the group consisting of polyamide 410, polyamide 412, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide 1010, polyamide 1012, and a copolyamide containing these as constituent components. The method for improving chemical resistance according to claim 1 or 2, which is the above. The method for improving chemical resistance according to claim 1, wherein the polyamide (B) contains 50 mol% or more of a unit composed of an aliphatic diamine and an aliphatic dicarboxylic acid. The polyamide (B) is one or more selected from the group consisting of polyamide 46, polyamide 56, polyamide 66, and a copolyamide containing these as constituent components. To improve the chemical resistance of . The chemical resistance according to any one of claims 1 to 5, wherein the crystallization peak temperature is equal to or higher than the crystallization peak temperature of the polyamide (A) and is equal to or lower than the crystallization peak temperature of the polyamide (B) . How to improve . The chemical resistance according to any one of claims 1 to 6, comprising 30 to 70% by mass of the polyamide (A) and 30 to 70% by mass of the polyamide (B) with respect to 100% by mass of the polyamide. How to improve .