Polyamide resin composition and method for producing the same

Abstract

To provide a polyamide resin composition which has good melt workability and surface appearance, and low melt shear viscosity even in a large-sized apparatus assuming an actual production apparatus, while having high relative viscosity, and a method for producing the same.SOLUTION: A polyamide resin composition contains a polyamide resin and an inorganic filler, wherein formic acid relative viscosity (RV) is 70 or more and 400 or less, and melt shear viscosity [η] Pa s at melting point+15°C of the polyamide resin composition and a shear rate of 1,000 sec-1 satisfies the following general formula (I): [η]≤0.7×[RV]+7×[inorganic filler]+100. In the formula (I), [η] represents melt shear viscosity (Pa s), [RV] represents formic acid relative viscosity of the polyamide resin composition, and [inorganic filler] represents an inorganic filler content (mass%).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyamide resin composition and a method for producing the same.

Background Art

[0002] Since polyamide resins exhibit excellent properties, they are used in the manufacture of various machines and parts such as automobiles, machinery, electrical and electronic parts. Among them, polyamide resins are particularly widely used as molding materials for sliding parts such as gears, cams, and bearings because of their excellent mechanical properties and wear resistance.

[0003] In recent years, in the automotive field, there has been a remarkable trend to replace automotive parts conventionally made of metal with glass fiber-reinforced polyamide resins from the viewpoints of weight reduction for fuel efficiency improvement, cost reduction, and rationalization of the assembly process. For further high performance of various machines and parts, while the demand for resin compositions with a higher molecular weight of the resin component is increasing, materials with even better processability are also required.

[0004] As a method for obtaining a high molecular weight resin composition, a method of melt-kneading a high molecular weight resin with an extruder, a method of melt-kneading a low molecular weight resin with an extruder to obtain a pellet-like product and then performing a heating process (hereinafter sometimes referred to as solid-phase polymerization) to increase the molecular weight, etc. are known.

[0005] Patent Documents 1 and 2 describe a method of suppressing the occurrence of wall surface fusion and fusion lumps by pre-heat-treating crystalline polyamide particles in an amorphous state to promote crystallization and then performing solid-phase polymerization.

[0006] Patent Document 3 describes a method of suppressing heat-resistant discoloration and mold fouling due to outgassing during melt molding by performing solid-phase polymerization on a low condensate whose terminals are adjusted by polymerization.

[0007] In addition, Patent Document 4 discloses a glass fiber-containing polyamide resin composition that is advantageously used in the production of sliding parts such as gears for electric power steering. The polyamide resin composition contains 30 to 90% by mass of polyamide 66 having a number average molecular weight of 23,000 to 50,000 and 70 to 10% by mass of glass fibers having an average fiber diameter of 4 to 8 μm, with the aim of providing such a composition.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, although the inventions described in Patent Documents 1 to 4 can all produce high molecular weight resin compositions, the effects in large-scale equipment assuming actual production equipment have not been shown. In the production of large-scale equipment, product variations are likely to occur due to uneven heating and the like, resulting in problems in melt processability and surface appearance.

[0010]

[0011] ​In addition, polyamide resin compositions in a relatively high viscosity range are difficult to control in terms of viscosity, and this has been cited as a problem leading to issues such as a decrease in yield due to off-spec products.

[0012] The present invention has been made in view of the above circumstances, and an object thereof is to provide a polyamide resin composition having a low melt shear viscosity with good melt processability and surface appearance even in large-scale equipment assuming actual production equipment, while having a high relative viscosity, and a method for producing the same.

[0013] In addition, the present invention has been made in view of the above circumstances, and provides a method for producing a thermoplastic resin composition that can suppress the generation of oligomers during production and further improve the viscosity controllability during production.

Means for Solving the Problems

[0014] The inventors of the present invention have found that a specific polyamide resin composition and production method can solve the above problems, and have completed the present invention.

[0015] The present invention has been made based on the above findings and includes the following aspects. {Aspect 1} 〔1〕 A polyamide resin composition containing a polyamide resin and an inorganic filler, having a formic acid relative viscosity (RV) of 70 or more and 400 or less, at a temperature of the melting point of the polyamide resin composition + 15°C and a shear rate of 1000 sec -1 wherein the melt shear viscosity [η] Pa·s satisfies the following general formula (I). [η] ≦ 0.7×[RV] + 7×[inorganic filler] + 100 ··· (I) (In formula (I), [η] represents the melt shear viscosity (Pa·s), [RV] represents the formic acid relative viscosity of the polyamide resin composition, and [inorganic filler] represents the content (% by mass) of the inorganic filler in 100% by mass of the polyamide resin composition.) 〔2〕 The polyamide resin composition according to [1], wherein the polyamide resin is at least one polyamide resin selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610, and polyamide 612. [3] The polyamide resin composition according to [1] or [2], wherein the inorganic filler is glass fiber having a number average fiber diameter of 3 μm or more and 15 μm or less. [4] The polyamide resin composition according to any one of [1] to [3], wherein the inorganic filler is glass fiber having a number average fiber diameter of 3 μm or more and 9 μm or less. [5] A melt-kneading step of adding 5 to 100 parts by mass of an inorganic filler to 100 parts by mass of a polyamide resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less and melt-kneading to obtain melt-kneaded product pellets, A heating step of subjecting the melt-kneaded product pellets to solid-phase polymerization at a set temperature T °C satisfying the following general formula (II): Tm - 130 ≤ T ≤ Tm - 10 ··· (II) (In the formula (II), T represents the set temperature (°C), and Tm represents the melting point (°C) of the polyamide resin.) A method for producing a polyamide resin composition according to any one of [1] to [4], including the heating step. [6] The method for producing a polyamide resin composition according to [5], wherein in the heating step, solid-phase polymerization is carried out with a heating time of 10 hours or more and 50 hours or less from the start of temperature increase. [7] The method for producing a polyamide resin composition according to [5] or [6], wherein in the heating step, solid-phase polymerization is carried out under a reduced pressure of 0.015 MPa or less in absolute pressure or under an inert gas stream. [8] The method for producing a polyamide resin composition according to any one of [5] to [7], wherein the melt shear viscosity [η] Pa·s at the melting point of the polyamide resin composition + 15 °C and a shear rate of 1000 sec -1 satisfies the following general formula (III). 0.7×[RV] + 7×[Inorganic filler] + 50 < [η] ≤ 0.7×[RV] + 7×[Inorganic filler] + 100 ··· (III) (In formula (III), [η] represents the melt shear viscosity (Pa·s), [RV] represents the formic acid relative viscosity of the polyamide resin composition, and [Inorganic filler] represents the content (% by mass) of the inorganic filler in 100% by mass of the polyamide resin composition.) [9] The melt shear viscosity [η] Pa·s at the melting point of the polyamide resin composition + 15°C and a shear rate of 1000 sec -1 satisfies the following general formula (IV), and the method for producing a polyamide resin composition according to any one of [5] to [7]. 0.7×[RV] + 7×[Inorganic filler] - 50 ≤ [η] ≤ 0.7×[RV] + 7×[Inorganic filler] + 50 ··· (IV) (In formula (IV), [η] represents the melt shear viscosity (Pa·s), [RV] represents the formic acid relative viscosity of the polyamide resin composition, and [Inorganic filler] represents the content (% by mass) of the inorganic filler in 100% by mass of the polyamide resin composition.) [Aspect 2]

[10] A melt-kneading step of adding 5 to 100 parts by mass of glass fiber to 100 parts by mass of a thermoplastic resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less, and melt-kneading to obtain a melt-kneaded product, A pre-drying step of heating and drying the melt-kneaded product at a temperature T1°C within the range represented by the following formula (V), After the pre-drying step, a heating step of heating at a temperature T2°C within the range represented by the following formula (VI) to obtain a thermoplastic resin composition, The method for producing a thermoplastic resin composition comprising Tm - 185 ≤ T1 < Tm - 130 ···(V) (In formula (V), Tm is the melting point (°C) of the thermoplastic resin.) Tm - 130 ≤ T2 ≤ Tm - 10 ···(VI) (In formula (VI), Tm is the melting point (°C) of the thermoplastic resin.)

[11] The method for producing a thermoplastic resin composition according to

[10] , wherein in the pre-drying step, heating is performed at a temperature of T1 °C for 2 hours or more to dry the composition.

[12] The method for producing a thermoplastic resin composition according to

[10] or

[11] , wherein in the heating step, heating is performed at a temperature of T2 °C for 30 minutes or more and 24 hours or less. [Advantages of the Invention]

[0016] According to Embodiment 1 of the present invention, it is possible to provide a polyamide resin composition having a high relative viscosity, excellent melt processability, and good surface appearance, and a method for producing the same.

[0017] Further, according to Embodiment 2 of the present invention, since it has the above configuration, it is possible to suppress the generation of oligomers during production, and further improve the viscosity controllability during production. [Modes for Carrying Out the Invention]

[0018] Hereinafter, modes for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The present embodiment is an exemplification for explaining the present invention, and the present invention is not limited only to the embodiments thereof. That is, the present invention can be variously modified without departing from the gist thereof.

[0019] [Embodiment 1] [Polyamide Resin Composition] The polyamide resin composition of the present embodiment (hereinafter sometimes simply referred to as "the present embodiment") contains a polyamide resin and an inorganic filler, has a formic acid relative viscosity (RV) of 70 or more and 400 or less, and is a polyamide resin composition in which the melt shear viscosity [η] Pa·s at the melting point of the polyamide resin composition + 15 °C and a shear rate of 1000 sec -1 satisfies the following general formula (I). [η] ≦ 0.7 × [RV] + 7 × [inorganic filler] + 100 ··· (I) (In formula (I), [η] represents the melt shear viscosity (Pa·s), [RV] represents the relative viscosity of formic acid of the polyamide resin composition, and [inorganic filler] represents the content (% by mass) of the inorganic filler in 100% by mass of the polyamide resin composition.) The above melt shear viscosity varies depending on the content of the inorganic filler and the relative viscosity of formic acid in the polyamide resin composition. The melt shear viscosity can be linked to the moldability, and the relative viscosity of formic acid can be linked to some mechanical properties. However, if the melt shear viscosity satisfies the above formula (I), it can be said that the melt shear viscosity is low in the polyamide resin composition with the same content of the inorganic filler and relative viscosity of formic acid, and it can be judged that the moldability is good while satisfying the mechanical properties. As can be seen from the above formula (I), usually, the higher the content of the inorganic filler, the higher the melt shear viscosity, and the higher the relative viscosity of formic acid, the higher the melt shear viscosity.

[0020] The polyamide resin composition of the present embodiment has a relative viscosity of formic acid (RV) of 70 or more and 400 or less, preferably 80 or more and 380 or less, more preferably 90 or more and 360 or less, and most preferably 100 or more and 350 or less. The melt shear viscosity [η] Pa·s of the polyamide resin composition of the present embodiment satisfies the following general formula (I), and preferably satisfies the following general formula (III) or the following general formula (IV). [η]≦0.7×[RV]+7×[inorganic filler]+100 ··· (I) 0.7×[RV]+7×[inorganic filler]+50<[η]≦0.7×[RV]+7×[inorganic filler]+100 ··· (III) 0.7×[RV]+7×[inorganic filler]-50≦[η]≦0.7×[RV]+7×[inorganic filler]+50 ··· (IV) (In formulas (I), (III), and (IV), [η] represents the melt shear viscosity (Pa·s), [RV] represents the relative viscosity of formic acid of the polyamide resin composition, and [inorganic filler] represents the content (% by mass) of the inorganic filler in 100% by mass of the polyamide resin composition.)

[0021] Regarding the materials used in the polyamide resin composition of the present embodiment, the details will be described below. (Polyamide resin) The polyamide resin preferably has a relative viscosity (RV) in formic acid of 25 or more and 70 or less, more preferably 27 or more and 65 or less, and even more preferably 30 or more and 60 or less. When the relative viscosity (RV) in formic acid is within the above range, the degree of polymerization of the polyamide resin is within an appropriate range, and it will be kneaded with the inorganic filler in a state where a large amount of the ends of the polyamide exists, so that the adhesion at the interface between the inorganic filler and the polyamide resin can be improved. The relative viscosity (RV) in formic acid is represented by the value measured with 90% formic acid at 25°C specified in ASTM D789.

[0022] Examples of the polyamide resin include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polytetramethylene sebacamide (nylon 410), polypentamethylene adipamide (nylon 56), polypentamethylene sebacamide (nylon 510), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polydecamethylene adipamide (nylon 106), polydecamethylene sebacamide (nylon 1010), polydecamethylene dodecamide (nylon 1012), polyundecanamide (nylon 11), polydodecanamide (nylon 12), polycaproamide / polyhexamethylene adipamide copolymer (nylon 6 / 66), polycaproamide / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polyhexamethylene terephthalamide / polyundecanamide copolymer (nylon 6T / 11), polyhexamethylene terephthalamide / polydodecanamide copolymer (nylon 6T / 12), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyxylylene adipamide (nylon XD6), polyxylylene sebacamide (nylon XD10), polyhexamethylene terephthalamide / polypentamethylene terephthalamide copolymer (nylon 6T / 5T), polyhexamethylene terephthalamide / poly-2-methylpentamethylene terephthalamide copolymer (nylon 6T / M5T), polypentamethylene terephthalamide / polydecamethylene terephthalamide copolymer (nylon 5T / 10T), polynonamethylene terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polydodecamethylene terephthalamide (nylon 12T), and the like.Note that the " / " mentioned here indicates a copolymer. These polyamide resins may be used alone or in combination of two or more. Among these, as the polyamide resin, it is preferable to use at least one polyamide resin selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610, and polyamide 612, and it is particularly preferable to use polyamide 66. Polyamide 66 itself is a generally known polyamide resin and is usually produced by polycondensation of hexamethylenediamine and adipic acid. Alternatively, polyamide 66 may be a copolymer containing less than 30% by mass of at least one monomer unit selected from the group consisting of lactam, aminocarboxylic acid, and combinations of other diamines and dicarboxylic acids with respect to the total mass of all monomer units.

[0023] Also, these polyamide resins may be commercially available ones or may be produced by known methods. Specifically, the production method of polyamide is not particularly limited, and examples thereof include a method of ring-opening polymerization of lactam, a method of self-condensation of ω-aminocarboxylic acid, and a method of condensing diamine and dicarboxylic acid.

[0024] Furthermore, it is preferable that the value [NH2] / [COOH] obtained by dividing the amount of amino end groups ([NH2]) by the amount of carboxy end groups ([COOH]) of the polyamide resin is 0.5 or more and 0.9 or less. When [NH2] / [COOH] is within the above range, the interaction between the surface of the glass fiber and the polyamide end becomes sufficiently large during melt kneading, and the physical properties of the resulting polyamide resin composition become sufficiently high. The amount of amino end groups and the amount of carboxy end groups can be measured, for example 1 by using H-NMR.

[0025] (Inorganic filler) The inorganic filler is preferably at least one selected from the group consisting of chopped strand glass fiber (glass fiber), carbon fiber, wollastonite, talc, mica, kaolin, barium sulfate, calcium carbonate, apatite, sodium phosphate, fluorite, boron nitride, potassium titanate, and molybdenum disulfide. Among these, from the viewpoints of physical properties, safety, and economy, chopped strand glass fiber, carbon fiber, wollastonite, talc, mica, kaolin, boron nitride, potassium titanate, and apatite are preferred, and chopped strand glass fiber is more preferred. It is preferable to use the chopped strand glass fiber that is aggregated by a known aggregating agent (binder) mainly composed of an acrylic resin, an epoxy resin, a urethane resin, or the like, and it is more preferable to use the one aggregated by an aggregating agent mainly composed of an acrylic resin or an epoxy resin. In addition, since further improvement in the mechanical properties of the obtained molded article is expected, it is preferable to use the inorganic filler that has been pretreated with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound, or an epoxy compound.

[0026] The content of the inorganic filler in the polyamide resin composition of the present embodiment is preferably 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the polyamide resin. When the content of the inorganic filler is 5 parts by mass or more with respect to 100 parts by mass of the polyamide resin, the rigidity and strength of the polyamide resin composition can be further increased. On the other hand, when the content of the inorganic filler is 100 parts by mass or less with respect to 100 parts by mass of the polyamide resin, the molding processability becomes better when the polyamide resin composition is molded for each application. Further, the content of the inorganic filler in the polyamide resin composition is more preferably 7 parts by mass or more and 95 parts by mass or less, and even more preferably 10 parts by mass or more and 90 parts by mass or less. In addition, the content of the inorganic filler in the polyamide resin composition of the present embodiment (that is, the content of the inorganic filler in 100% by mass of the polyamide resin composition (% by mass)) is preferably 4.7% by mass or more and 50% by mass or less, more preferably 6.5% by mass or more and 48% by mass or less, and even more preferably 9% by mass or more and 47% by mass or less.

[0027] A description will be given of chopped strand glass fiber, which is an example of the inorganic filler (hereinafter, sometimes simply referred to as "glass fiber"). The weight average fiber length of the glass fiber in the polyamide resin composition is preferably 100 μm or more and 1000 μm or less. When the weight average fiber length of the glass fiber is 100 μm or more, the reinforcing effect can be more surely exhibited sufficiently, and the impact strength and tensile strength of the obtained polyamide resin composition can be further improved. On the other hand, when the average fiber length of the glass fiber is 1000 μm or less, it is possible to more effectively suppress the glass fiber from protruding from the pellets when the obtained melt-kneaded product is pelletized and the bulk density of the pellets from decreasing. Incidentally, the weight average fiber length of the glass fiber can be measured, for example, using the following method. First, 100 or more glass fibers are arbitrarily selected, and the total mass of the glass fibers is measured. Next, the fiber length of each glass fiber is measured by observing the glass fiber with an optical microscope, a scanning electron microscope, or the like, and the value obtained by dividing the total value by the total mass of the glass fibers can be determined as the weight average fiber length.

[0028] The number average fiber diameter of the glass fiber is preferably 3 μm or more and 15 μm or less, more preferably 4 μm or more and 13 μm or less, and even more preferably 5 μm or more and 10 μm. Further, it is preferably 3 μm or more and 9 μm or less. That is, the glass fiber as a raw material preferably has a very thin shape. When the average fiber diameter of the glass fiber is 3 μm or more, the strength of the glass fiber is sufficiently high, so that the reinforcing effect is more sufficiently exhibited. When the average fiber diameter of the glass fiber is 15 μm or less, the surface area of the glass fiber is sufficiently large, and the effect of further strengthening the adhesion at the interface between the glass fiber and the resin is sufficiently exhibited. Incidentally, the number average fiber diameter of the glass fiber can be measured, for example, by using the following method. First, 100 or more glass fibers are arbitrarily selected. Next, the fiber diameter of each glass fiber is measured by observing the glass fiber with an optical microscope, a scanning electron microscope, or the like, and the value obtained by dividing the total value by 100 can be determined as the number average fiber diameter.

[0029] From the viewpoint of being able to exhibit high characteristics, the wollastonite preferably has a number average fiber diameter (D) of 3 to 30 μm, a weight average fiber length (L) of 10 to 500 μm, and an aspect ratio (L / D) of 3 to 100.

[0030] From the viewpoint of being able to exhibit high characteristics, the talc, mica, kaolin, silicon nitride, and potassium titanate preferably have a number average particle diameter of 0.1 to 3 μm. From the viewpoint of improving mechanical strength, it is preferable to subject the inorganic filler to surface treatment. The surface treatment agent is not particularly limited, and for example, a coupling agent or a film-forming agent can be used. The coupling agent is not particularly limited, and examples thereof include silane-based coupling agents and titanium-based coupling agents.

[0031] (Copper compound) In the polyamide resin composition of the present embodiment, in addition to the above-described polyamide resin and inorganic filler, a copper compound can be blended. Examples of the copper compound include cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide (copper iodide), copper sulfate, copper phosphate, copper borate, copper nitrate and other inorganic acid copper salts; copper acetate, copper propionate, copper benzoate, copper adipate, copper terephthalate, copper isophthalate, copper stearate and other organic acid copper salts. Alternatively, a copper complex salt coordinated with a chelating agent can be used. Among them, it is preferable to use cuprous iodide. These copper compounds may be used alone or in combination of two or more.

[0032] The content of the copper compound is not particularly limited, but is preferably 0.0001 part by mass or more and 1 part by mass or less, more preferably 0.005 part by mass or more and 0.3 part by mass or less, and still more preferably 0.02 part by mass or more and 0.1 part by mass or less with respect to 100 parts by mass of the polyamide resin.

[0033] (Metal halide) In the polyamide resin composition of the present embodiment, in addition to the above-described polyamide resin and inorganic filler, a metal halide can be blended. As the metal halide, potassium halide is preferable. Examples of the potassium halide include potassium iodide, potassium bromide, potassium chloride and the like. Among them, potassium iodide is preferable as the metal halide. These potassium halides may be used alone or in combination of two or more.

[0034] The content of the metal halide is not particularly limited, but is preferably 0.0001 part by mass or more and 1 part by mass or less, more preferably 0.005 part by mass or more and 0.8 part by mass or less, and still more preferably 0.02 part by mass or more and 0.7 part by mass or less with respect to 100 parts by mass of the polyamide resin.

[0035] (Other resin components) In the polyamide resin composition of the present embodiment, other thermoplastic resins other than the polyamide resin can be used as long as the properties of the obtained polyamide resin composition are not impaired. Examples of other thermoplastic resins include general-purpose resins such as polyethylene, polypropylene, ethylene-propylene copolymer, polystyrene, ABS resin, AS resin, and acrylic resin; polycarbonate, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, and the like. These other thermoplastic resins are preferably used after being modified with a modifier such as maleic anhydride or a glycidyl group-containing monomer. Among them, resins having no functional groups such as polyethylene, polypropylene, or ethylene-propylene copolymer are preferably used after being modified.

[0036] <Method for producing polyamide resin composition> Hereinafter, each step of the method for producing the polyamide resin composition of the present embodiment will be described in detail. The method for producing the polyamide resin composition of the present embodiment is a melt-kneading step of adding 5 to 100 parts by mass of an inorganic filler to 100 parts by mass of a polyamide resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less, and melt-kneading to obtain melt-kneaded product pellets; subjecting the melt-kneaded product pellets to solid-phase polymerization at a set temperature T °C satisfying the following general formula (II): Tm - 130 ≤ T ≤ Tm - 10 ··· (II) (In the formula (II), T represents the set temperature (°C), and Tm represents the melting point (°C) of the polyamide resin.) and a heating step of obtaining a polyamide resin composition, and is characterized by including the above steps.

[0037] In the prior art, in order to obtain a polyamide resin composition having a high molecular weight, it was common to polymerize a polyamide resin to increase its molecular weight, then add an inorganic filler, and perform melt-kneading. In contrast, in the method of this embodiment, the formic acid relative viscosity (RV) is defined, and a polyamide resin having a low to medium molecular weight is melt-kneaded together with an inorganic filler. After the melt-kneaded product is extruded into strands, cooled by passing through a water-cooling bath or the like, cut to obtain pellets, and then when solid-phase polymerization of these pellets is carried out, by controlling the heating rate, set temperature, heating time, etc., a polyamide resin composition having a relatively low melt shear viscosity while having a high formic acid relative viscosity can be obtained. This polyamide resin composition is useful because it has a low melt shear viscosity during melt processing.

[0038] (Melt-kneading step) In the melt-kneading step in the production method of this embodiment, an inorganic filler is added to a polyamide resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less so as to have a specific blending ratio, and melt-kneading is carried out to obtain melt-kneaded product pellets. Specifically, it is preferable to add 5 parts by mass or more and 100 parts by mass or less of the inorganic filler with respect to 100 parts by mass of the polyamide resin, more preferably 7 parts by mass or more and 95 parts by mass or less, and even more preferably 10 parts by mass or more and 90 parts by mass or less. By the addition amount of the inorganic filler being equal to or more than the above lower limit value, a polyamide resin composition having enhanced rigidity and strength can be obtained. On the other hand, by the addition amount of the inorganic filler being equal to or less than the above upper limit value, when the obtained polyamide resin composition is molded for each application, the moldability becomes better.

[0039] Moreover, as the polyamide resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less, a polyamide resin having a formic acid relative viscosity (RV) of 27 or more and 65 or less is more preferable, and a polyamide resin having a formic acid relative viscosity (RV) of 30 or more and 60 or less is even more preferable.

[0040] As the apparatus for performing melt-kneading, known apparatuses can be used. For example, melt-kneading machines such as single-screw or twin-screw extruders, Banbury mixers, and mixing rolls are used. Among these, a multi-screw extruder equipped with a devolatilization mechanism (vent) device and side feeder equipment is preferable, and a twin-screw extruder is more preferable.

[0041] When melting and kneading the polyamide resin and the inorganic filler in the extruder, the molecular weight of the polyamide resin can be adjusted by appropriately setting kneading conditions such as the resin temperature during extrusion, the degree of vacuum, and the average residence time. As the resin temperature during melting and kneading, it is preferably not less than the melting point of the raw polyamide resin and not more than 370°C, more preferably not less than the melting point of the raw polyamide resin + 5°C and not more than 350°C, still more preferably not less than the melting point of the raw polyamide resin + 10°C and not more than 340°C, particularly preferably not less than the melting point of the raw polyamide resin + 15°C and not more than 335°C, and most preferably not less than the melting point of the raw polyamide resin + 20°C and not more than 330°C. By setting the temperature during melting and kneading to be not less than the melting point of the raw polyamide resin, the melting of the polyamide resin becomes sufficient and the load on the extruder motor tends to be further reduced. Also, by setting the resin temperature during melting and kneading to be not more than 370°C, the decomposition of the polyamide resin itself tends to be more suppressed. For example, when using polyamide 66 with a melting point of 264°C as the polyamide resin, the resin temperature during melting and kneading is preferably not less than 264°C and not more than 370°C, more preferably not less than 269°C and not more than 350°C, still more preferably not less than 274°C and not more than 340°C, particularly preferably not less than 279°C and not more than 335°C, and most preferably not less than 284°C and not more than 330°C. Even when using a polyamide resin other than polyamide 66 as the raw polyamide resin, it can be appropriately adjusted according to its melting point.

[0042] The resin temperature during melting and kneading can be measured, for example, by directly contacting a thermometer such as a thermocouple with the melt-kneaded product coming out of the discharge port (spinning nozzle) of the extruder. The adjustment of the resin temperature during melting and kneading can be achieved by adjusting the heater temperature of the cylinder of the extruder or by appropriately adjusting the amount of heat generated by shear of the resin by changing the rotation speed and discharge amount of the extruder.

[0043] The average residence time during the melt-kneading is preferably 10 seconds or more and 120 seconds or less, more preferably 20 seconds or more and 100 seconds or less, still more preferably 25 seconds or more and 90 seconds or less, particularly preferably 30 seconds or more and 80 seconds or less, and most preferably 35 seconds or more and 70 seconds or less. By setting the average residence time during the melt-kneading to 10 seconds or more, the melt-kneaded product can be obtained more efficiently. Also, by setting the average residence time during the melt-kneading to 120 seconds or less, the discharge rate (production rate) of extrusion tends to increase to some extent. As a result, the productivity of the polyamide resin composition also tends to be better. Note that the average residence time means the residence time when the residence time in the melt-kneading apparatus is constant, and when the residence time is non-uniform, it means the average value of the shortest residence time and the longest residence time. A component (hereinafter abbreviated as "Component X") that can be distinguished from the raw material polyamide resin, such as a colorant masterbatch during melt-kneading or a resin having a different color from the raw material polyamide resin used in the melt-kneading process, is added to the melt-kneading apparatus, and the discharge start time and discharge end time in the state where Component X is the most concentrated are measured, and the average residence time can be measured by averaging the discharge start time and the discharge end time. The above average residence time can be appropriately adjusted according to the discharge amount (discharge rate) and rotation speed of the extruder.

[0044] (Heating step) In the heating step in the method for producing the polyamide resin composition of the present embodiment, the melt-kneaded product pellets are subjected to solid-phase polymerization at a set temperature T (°C) satisfying the following general formula (II): Tm - 130 ≤ T ≤ Tm - 10 ··· (II) (In formula (II), T represents the set temperature (°C), and Tm represents the melting point (°C) of the polyamide resin.) to obtain a polyamide resin composition.

[0045] One preferred form of the heating step in the method for producing the polyamide resin composition of the present embodiment is to set the temperature T (°C) represented by the general formula (II) to 180 °C or higher for the polyamide resin composition pellets produced in the melt-kneading step, heat and raise the temperature at a rate of 8 to 40 °C / hour, and perform solid-phase polymerization for 10 hours or more and 50 hours or less from the start of temperature rise to increase the molecular weight and obtain a polyamide resin composition having a target formic acid relative viscosity. Another preferred form of the heating step is to set the temperature T represented by the general formula (II) to 180 °C or lower for the polyamide composition pellets produced in the melt-kneading step, heat and raise the temperature at a rate of 40 to 200 °C / hour, and perform solid-phase polymerization for 10 hours or more and 50 hours or less from the start of temperature rise to increase the molecular weight and obtain a polyamide resin composition having a target formic acid relative viscosity.

[0046] The formic acid relative viscosity (RV) of the polyamide resin composition obtained in the heating step is preferably adjusted to 70 or more and 400 or less. The formic acid relative viscosity of the polyamide resin composition is more preferably 80 or more and 380 or less, even more preferably 90 or more and 360 or less, and most preferably 100 or more and 350 or less. When the formic acid relative viscosity (RV) of the polyamide resin composition is 70 or more, sufficient mechanical strength can be exhibited, and when it is 400 or less, melt processability such as molding can be maintained. The melt shear viscosity of the polyamide resin composition obtained in the heating step is preferably within the range represented by the following general formula (I), and more preferably within the range represented by the following general formula (III) or (IV). When the melt shear viscosity is within the range of the following general formula (I) and within the range of the above formic acid relative viscosity (RV), a polyamide resin composition having good melt processability is obtained. [η] ≦ 0.7×[RV] + 7×[inorganic filler] + 100 ··· (I) 0.7×[RV] + 7×[inorganic filler] + 50 < [η] ≦ 0.7×[RV] + 7×[inorganic filler] + 100 ··· (III) 0.7×[RV] + 7×[inorganic filler] - 50 ≦ [η] ≦ 0.7×[RV] + 7×[inorganic filler] + 50 ··· (IV) (In the formula, [η] represents the melt shear viscosity (Pa·s), [RV] represents the relative viscosity in formic acid of the polyamide resin composition, and [inorganic filler] represents the filler content (% by mass) in 100% by mass of the polyamide resin composition.)

[0047] Regarding the set temperature T in the heating step, by setting it to be "the melting point of the polyamide resin - 130°C" or higher, the reaction can be accelerated, polymerization can be carried out efficiently, and the target degree of polymerization can be reached. Further, when the set temperature T is "the melting point of the polyamide resin - 10°C" or lower, thermal decomposition of the polyamide resin can be further suppressed, coloring deterioration on the polymer surface can be suppressed, and in addition, fusion of the composition pellets with each other can be further suppressed. Note that the melting point Tm of the polyamide resin composition can be measured in accordance with JIS-K7121. As the measuring device, for example, Diamond DSC manufactured by PERKIN-ELMER can be used. Specifically, it can be measured using the method shown in the examples described later.

[0048] In the heating step, the heating time of the polyamide resin composition pellets is preferably 8 hours or more and 50 hours or less from the start of temperature rise within the temperature range of the general formula (II), and more preferably 10 hours or more and 50 hours or less from the start of temperature rise. When the heating time is at least the above lower limit value, the polyamide resin composition can keep the melt shear viscosity low while having a high relative viscosity in formic acid. When the heating time is at most the above upper limit value, a polyamide resin composition with a high relative viscosity in formic acid and a low melt shear viscosity can be efficiently produced. Also, regarding the relationship between the set temperature and the heating rate in the heating step, when the set temperature is 180°C or higher, heat up at a heating rate of 8 - 40°C / hour, and when the set temperature is below 180°C, heat up at a heating rate of 40 - 200°C / hour. By adjusting the time from the start of temperature rise, a polyamide resin composition with a predetermined relative viscosity in formic acid (RV) and melt shear viscosity can be obtained.

[0049] Incidentally, the solid-phase polymerization reaction can be carried out either in a continuous mode or in a batch mode. The solid-phase polymerization reactor may be vertical or horizontal. It is preferable to stir the solid-phase polymerization reaction to enhance the uniformity of the reaction. The polymerization reactor may be of a main body rotation type or a stirring type using a stirring blade or the like.

[0050] Also, the solid-phase polymerization reaction in the heating step can be carried out either under vacuum or under an inert gas stream. When the solid-phase polymerization is carried out under vacuum, it is preferably carried out at a degree of vacuum of 0.015 MPa or less in absolute pressure, more preferably at a degree of vacuum of 50 Pa to 0.015 MPa in absolute pressure, even more preferably at a degree of vacuum of 100 Pa to 0.013 MPa in absolute pressure, and most preferably at a degree of vacuum of 500 Pa to 0.012 MPa in absolute pressure. By setting the degree of vacuum to 0.015 MPa or less in absolute pressure, the coloring of the pellets due to oxidative degradation in solid-phase polymerization is suppressed.

[0051] When the solid-phase polymerization is carried out under an inert gas stream, it is preferably carried out in an inert gas atmosphere with an oxygen concentration of 5 vol ppm or less. By having an oxygen concentration of 5 vol ppm or less, the oxidative degradation of the obtained polyamide resin composition can be more effectively suppressed. Thereby, the reaction in which the molecular chains are broken and the decrease in the rate (polymerization reaction rate) at which the molecular weight increases can be more suppressed, and a polyamide resin composition having a predetermined molecular weight can be obtained. Also, the decrease in the mechanical properties and yellowing of the obtained polyamide resin composition can be more effectively suppressed.

[0052] Furthermore, when the solid-phase polymerization is carried out under an inert gas stream, a particle layer is formed with the melt-kneaded pellets, and at a position with a height of 0 times or more and 0.8 times or less, preferably 0 times or more and 0.5 times or less the height h of the particle layer, with respect to 10 kg of the melt-kneaded pellets, an amount of 50 L / hour or more and 1000 L / hour or less, preferably 100 L / hour or more and 900 L / hour or less, particularly preferably 200 L / hour or more and 800 L / hour or less of the inert gas is supplied while carrying out the solid-phase polymerization reaction. Incidentally, the height h of the particle layer of the melt-kneaded pellets is defined as follows. Open the solid-phase polymerization reactor, charge particles or pellets of an operation-equivalent amount of the melt-kneaded material at normal temperature and atmospheric pressure, and measure the height of the particle layer with the bottom of the reactor having a gas supply port as the reference (h = 0) in a state where a predetermined amount of inert gas is passed through. When the height surface of the particle layer fluctuates, the highest height and the lowest height can be measured, and the average value of these can also be taken as h.

[0053] Also, when using a main body rotation type as the solid-phase polymerization apparatus, the atmosphere may be vacuum (reduced pressure) or may be under an inert gas stream. The rotation speed is preferably from 0.3 revolutions per minute to 10 revolutions per minute, more preferably from 0.4 revolutions per minute to 8 revolutions per minute, and even more preferably from 0.5 revolutions per minute to 5 revolutions per minute. By setting the rotation speed to 0.3 revolutions per minute or more, the heat conduction efficiency to the pellets is improved, and by setting it to 10 revolutions per minute or less, wear of the inner wall of the apparatus can be suppressed.

[0054] By using the polyamide resin composition of the present embodiment, since the melt shear viscosity is low and the melt processability is excellent, productivity is improved, and the obtained polyamide resin composition is excellent in mechanical properties and long-term properties. Therefore, for example, it is suitably used for automotive parts, electronic and electrical parts, industrial machinery parts, various gears, etc.

[0055] {Aspect 2} <Method for producing a thermoplastic resin composition> The method for producing a thermoplastic resin composition of the present embodiment (hereinafter, may be simply referred to as "the production method of the present embodiment") includes a melt-kneading step, a pre-drying step, and a heating step in this order. The production method of the present embodiment may be a method consisting only of a melt-kneading step, a pre-drying step, and a heating step, or may further include other steps. In the above melt-kneading step, 2.5 to 100 parts by mass (preferably 5 to 100 parts by mass) of glass fiber is added to 100 parts by mass of a thermoplastic resin having a relative viscosity (RV) of formic acid of 25 or more and 70 or less, and melt-kneaded to obtain a melt-kneaded product. The above melt-kneaded product may be a kneaded product composed only of the above thermoplastic resin and the above glass fiber, or may further contain other components. In the above pre-drying step, the melt-kneaded product obtained in the above melt-kneading step is heated at a temperature T1 °C within the range represented by the following formula (V) and dried to obtain a pre-dried melt-kneaded product. In this specification, the units of temperature T1 and melting point Tm are °C. Tm - 185 ≤ T1 < Tm - 130 (V) (In the formula, Tm is the melting point (°C) of the above thermoplastic resin.) In the above heating step, the pre-dried melt-kneaded product obtained in the above pre-drying step is heated at a temperature T2 °C within the range represented by the following formula (VI) to obtain a thermoplastic resin composition. In this specification, the unit of temperature T2 is °C. Tm - 130 °C ≤ T2 ≤ Tm - 10 °C (VI) (In the formula, Tm is the melting point (°C) of the above thermoplastic resin.)

[0056] In the production method of a normal thermoplastic resin composition, after polymerizing a thermoplastic resin to increase its molecular weight, a filler such as glass fiber is added and melt-kneaded to obtain a thermoplastic resin composition.

[0057] On the other hand, in the production method of this embodiment, a low-molecular-weight to medium-molecular-weight thermoplastic resin and glass fiber are melt-kneaded to obtain a melt-kneaded product. Thereby, the adhesion at the interface between the glass fiber and the thermoplastic resin is improved. Then, by subjecting the melt-kneaded product to solid-phase polymerization to increase its molecular weight in the heating step, the state where the adhesion at the interface between the glass fiber and the thermoplastic resin is improved is maintained, and a thermoplastic resin composition excellent in vibration fatigue resistance can be obtained. Further, by carrying out the melt-kneading step and the heating step in this order, the state where the adhesion at the interface between the glass fiber and the thermoplastic resin is improved is maintained, and it becomes difficult for the filler to fall off during production.

[0058] Hereinafter, each step of the manufacturing method of this embodiment will be described in detail.

[0059] [Melting and Kneading Step] In the melting and kneading step, glass fibers are added to a thermoplastic resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less at a ratio of a specific blending ratio, and melted and kneaded to obtain a melt-kneaded product. Specifically, the added mass ratio of the glass fiber to 100 parts by mass of the above thermoplastic resin is preferably 2.5 parts by mass or more and 100 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, still more preferably 10 parts by mass or more and 100 parts by mass or less, and particularly preferably 20 parts by mass or more and 90 parts by mass or less. When the blending amount of the glass fiber is 5 parts by mass or more, a thermoplastic resin composition with enhanced rigidity and strength can be obtained. On the other hand, when it is below the above upper limit value, the resulting thermoplastic resin composition has better moldability when molded for each application.

[0060] As the apparatus for performing the melting and kneading, a known apparatus can be used. For example, melt-kneading machines such as single-screw or twin-screw extruders, Banbury mixers, and mixing rolls are used. Among these, a multi-screw extruder equipped with a devolatilization mechanism (vent) device and side feeder equipment is preferred, and a twin-screw extruder is more preferred.

[0061] When melt-kneading with an extruder, the molecular weight of the thermoplastic resin after melt-kneading can be adjusted by appropriately setting kneading conditions such as the resin temperature during extrusion, the degree of vacuum reduction, and the average residence time.

[0062] The resin temperature during melting and kneading is preferably not less than the melting point of the raw material thermoplastic resin and not more than 370 °C, more preferably the melting point of the raw material thermoplastic resin + 5 °C or more and 350 °C or less, still more preferably the melting point of the raw material thermoplastic resin + 10 °C or more and 340 °C or less, particularly preferably the melting point of the raw material thermoplastic resin + 15 °C or more and 335 °C or less, and most preferably the melting point of the raw material thermoplastic resin + 20 °C or more and 330 °C or less. By setting the resin temperature during melt-kneading to be equal to or higher than the above lower limit value, the melting of the raw material thermoplastic resin becomes sufficient, and the load on the melt-kneading machine such as the extruder motor tends to be further reduced. Also, by setting the resin temperature during melt-kneading to be equal to or lower than the above upper limit value, the decomposition of the raw material thermoplastic resin itself tends to be further suppressed.

[0063] By appropriately setting kneading conditions such as the resin temperature, degree of vacuum, and average residence time during melt-kneading (for example, during extrusion), the weight-average molecular weight of the thermoplastic resin after melt-kneading can be controlled within the range from a low molecular weight to a medium molecular weight. Here, the range from a low molecular weight to a medium molecular weight may be a range where the weight-average molecular weight is 10,000 or more and 70,000 or less, preferably 15,000 or more and 65,000 or less, more preferably 20,000 or more and 60,000 or less.

[0064] For example, when using polyamide 66 with a melting point of 264°C as the raw material thermoplastic resin, it is preferable that the resin temperature during melt-kneading is 264°C or higher and 370°C or lower, more preferably 269°C or higher and 350°C or lower, even more preferably 274°C or higher and 340°C or lower, particularly preferably 279°C or higher and 335°C or lower, and most preferably 284°C or higher and 330°C or lower. By setting the resin temperature during melt-kneading to be equal to or higher than the above lower limit value, polyamide 66 melts more sufficiently, and the load on the melt-kneading machine such as the extruder motor tends to be further reduced. Also, by setting the resin temperature during melt-kneading to be equal to or lower than the above upper limit value, the decomposition of polyamide 66 itself tends to be further suppressed.

[0065] Even when using a polyamide resin other than polyamide 66 as the raw material polyamide resin, it can be appropriately adjusted according to its melting point. The above resin temperature can be measured, for example, by directly contacting a thermometer such as a thermocouple with the melt-kneaded product coming out of the discharge port (spinning nozzle) of the extruder. Adjustment of the resin temperature is possible by adjusting the heater temperature of the cylinder of the extruder or by appropriately adjusting the amount of heat generated by shearing of the resin by changing the rotation speed and discharge amount of the extruder.

[0066] The average residence time during melt-kneading is preferably 10 seconds or more and 120 seconds or less, more preferably 20 seconds or more and 100 seconds or less, still more preferably 25 seconds or more and 90 seconds or less, particularly preferably 30 seconds or more and 80 seconds or less, and most preferably 35 seconds or more and 70 seconds or less. By setting the average residence time during melt-kneading to be not less than the above lower limit value, the melt-kneaded product tends to be obtained more efficiently. Also, by setting the average residence time during melt-kneading to be not more than the above upper limit value, the discharge rate (production rate) of extrusion tends to increase to some extent. As a result, the productivity of the thermoplastic resin composition such as the polyamide resin composition also tends to be better. The average residence time means the residence time when the residence time in the melt-kneading apparatus is constant. When the residence time is non-uniform, it means the average value of the shortest residence time and the longest residence time.

[0067] The average residence time is measured by the following method. Component X is added to the melt-kneading apparatus, and the discharge start time and discharge end time in the state where Component X is the thickest are measured. By averaging the measured discharge start time and discharge end time, the average residence time can be measured. Component X is a component that can be distinguished from the raw material thermoplastic resin (for example, polyamide resin) used in the melt-kneading process, such as a colorant masterbatch during melt-kneading or a resin having a different color from the raw material thermoplastic resin (for example, polyamide resin) used in the melt-kneading process. The above average residence time can be appropriately adjusted according to the discharge amount (discharge rate) and rotation speed of the extruder.

[0068] The melt-kneaded product obtained by melt-kneading may be resin pellets and can be provided in various shapes. Preferred pellet shapes include round, elliptical, cylindrical, etc., which differ depending on the cutting method during extrusion processing. Pellets cut by a cutting method called underwater cut often become round, pellets cut by a cutting method called hot cut often become round or elliptical, and pellets cut by a cutting method called strand cut often become cylindrical.

[0069] The spherical pellets may have a shape that can approximate a perfect sphere even if they are not a perfect sphere or a complete true sphere. The preferred size in the case of spherical pellets is 8 mm or less as the pellet diameter (the maximum part of the diameter in the case of a true sphere approximation), more preferably 0.5 mm or more and 6 mm or less, and even more preferably 1 mm or more and 5 mm or less.

[0070] The elliptical pellets may have a shape that can approximate an ellipse even if they are not a perfect ellipse or a complete ellipsoid. The preferred size in the case of elliptical pellets is 8 mm or less as the major radius of the pellet (the maximum part of the major radius in the case of an ellipsoid approximation), more preferably 0.5 mm or more and 6 mm or less, and even more preferably 1 mm or more and 5 mm or less.

[0071] The cylindrical pellets may have a shape that can approximate a cylinder even if they are not a perfect cylinder or a complete cylindrical shape. The preferred size in the case of cylindrical pellets is 1 mm or more and 3 mm or less as the pellet diameter (the maximum part of the diameter in the case of a cylinder approximation), and the preferred length is 2 mm or more and 10 mm or less.

[0072] The raw materials used in the melt-kneading process will be described in detail below.

[0073] (Thermoplastic resin) As the thermoplastic resin, those having an inherent viscosity VN of 80 g / mL or more and 200 g / mL or less are preferred, those having an inherent viscosity VN of 100 g / mL or more and 200 g / mL or less are more preferred, and those having an inherent viscosity VN of 130 g / mL or more and 190 g / mL or less are even more preferred. When the inherent viscosity VN is within the above range, the degree of polymerization of the thermoplastic resin is within an appropriate range, and the adhesion at the interface between the glass fiber and the thermoplastic resin can be further improved. The inherent viscosity VN is a value measured in accordance with ISO307 (JIS-K6933). For example, it can be measured using the method shown in the examples described later. The resin component in the thermoplastic resin composition may be only the above thermoplastic resin having an inherent viscosity VN within the above range.

[0074] The relative viscosity (RV) of the thermoplastic resin in formic acid is 25 or more and 70 or less, preferably 27 or more and 65 or less, and more preferably 30 or more and 60 or less.

[0075] Specifically, the thermoplastic resin is preferably polyamide or polyester, and more preferably polyamide. The above thermoplastic resin may be one kind or a combination of two or more kinds.

[0076] Examples of polyamides include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polytetramethylene sebacamide (nylon 410), polypentamethylene adipamide (nylon 56), polypentamethylene sebacamide (nylon 510), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polydecamethylene adipamide (nylon 106), polydecamethylene sebacamide (nylon 1010), polydecamethylene dodecamide (nylon 1012), polyundecanamide (nylon 11), polydodecanamide (nylon 12), polycaproamide / polyhexamethylene adipamide copolymer (nylon 6 / 66), polycaproamide / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polyhexamethylene terephthalamide / polyundecanamide copolymer (nylon 6T / 11), polyhexamethylene terephthalamide / polydodecanamide copolymer (nylon 6T / 12), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyxylylene adipamide (nylon XD6), polyxylylene sebacamide (nylon XD10), polyhexamethylene terephthalamide / polypentamethylene terephthalamide copolymer (nylon 6T / 5T), polyhexamethylene terephthalamide / poly-2-methylpentamethylene terephthalamide copolymer (nylon 6T / M5T), polypentamethylene terephthalamide / polydecamethylene terephthalamide copolymer (nylon 5T / 10T), polynonamethylene terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polydodecamethylene terephthalamide (nylon 12T), etc.Note that the " / " mentioned here indicates a copolymer. These polyamides may be used alone or in combination of two or more.

[0077] Among them, as the polyamide, at least one polyamide resin selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610, and polyamide 612 is preferable, polyamide 6, polyamide 66, or polyamide 610 is more preferable, and polyamide 66 is particularly preferable. Polyamide 66 itself is a generally known polyamide resin and is usually produced by polycondensation of hexamethylenediamine and adipic acid. Alternatively, polyamide 66 may be a copolymer containing less than 30% by mass of at least one monomer unit selected from the group consisting of lactam, aminocarboxylic acid, and a combination of other diamines and dicarboxylic acids with respect to the total mass of all monomer units.

[0078] Also, these polyamides may be commercially available ones or may be produced by known methods. Specifically, the production method of polyamide is not particularly limited, and examples include a method of ring-opening polymerization of lactam, a method of self-condensation of ω-aminocarboxylic acid, a method of condensing diamine and dicarboxylic acid, etc.

[0079] It is preferable that the value [NH2] / [COOH] obtained by dividing the amount of amino end groups of the polyamide by the amount of carboxy end groups is 0.5 or more and 0.9 or less. When [NH2] / [COOH] is not less than the above lower limit value, solid-phase polymerization can be carried out more efficiently in the heating step described later. When [NH2] / [COOH] is not more than the above upper limit value, the interaction between the surface of the glass fiber and the polyamide end becomes sufficiently large, and the physical properties of the resulting composition, particularly the vibration fatigue resistance, become sufficiently high. The amount of amino end groups and the amount of carboxy end groups can be measured, for example 1 by using H-NMR.

[0080] Polyester is a polycondensate of a polyvalent carboxylic acid (dicarboxylic acid) and a polyalcohol (diol). Examples of the polyvalent carboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of the polyalcohol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. These components may be used individually or in combination of two or more. Specific examples of the polyester include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.

[0081] (Glass fiber) It is preferable to use glass fibers that are bundled with a known bundling agent (binder) mainly composed of an acrylic resin, an epoxy resin, a urethane resin, or the like, and more preferably those bundled with a bundling agent mainly composed of an acrylic resin or an epoxy resin. Further, since further improvement in the mechanical properties of the resulting thermoplastic resin composition is expected, it is preferable to use glass fibers pretreated with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound, or an epoxy compound.

[0082] The weight average fiber length of the glass fiber is preferably 100 μm or more and 1000 μm or less. When the weight average fiber length is at least the above lower limit value, the reinforcing effect can be more sufficiently exhibited, and the impact strength and tensile strength of the resulting thermoplastic resin composition can be further improved. On the other hand, when the weight average fiber length is at most the above upper limit value, when the resulting thermoplastic resin composition is pelletized, the glass fiber is less likely to protrude from the pellet. As a result, the bulk density of the pellet is less likely to decrease.

[0083] The weight average fiber length of the glass fiber can be measured, for example, using the following method. First, for example, select arbitrarily 100 or more glass fibers and measure the total mass of the glass fibers. Next, by observing the glass fibers with an optical microscope, a scanning electron microscope, or the like, the fiber length of each glass fiber is measured, and a value obtained by dividing the total value by the total mass of the glass fibers can be determined as the weight average fiber length.

[0084] The number average fiber diameter of the glass fibers is preferably 3 μm or more and 15 μm or less, more preferably 3 μm or more and 9 μm or less, still more preferably 4 μm or more and 8 μm or less, and particularly preferably 5 μm or more and 7 μm. Further, it may be 4 μm or more and 13 μm or less, or may be 5 μm or more and 10 μm. When the number average fiber diameter is at least the above lower limit value, the strength of the glass fibers is sufficiently high, so that the reinforcing effect is more sufficiently exhibited. When the number average fiber diameter is at most the above upper limit value, the surface area of the glass fibers is sufficiently large, and the effect of further strengthening the adhesion at the interface between the glass fibers and the resin is sufficiently exhibited.

[0085] The number average fiber diameter of the glass fibers can be measured, for example, using the following method. First, for example, arbitrarily select 100 or more glass fibers. Next, by observing the glass fibers with an optical microscope, a scanning electron microscope, or the like, the fiber diameter of each glass fiber is measured, and a value obtained by dividing the total value by the number of the measured glass fibers can be determined as the number average fiber diameter.

[0086] Generally used glass fibers are called "E glass" and contain about 7% by mass of boron oxide with respect to the total mass of the glass fibers. The glass fibers contained in the thermoplastic resin composition of the present embodiment preferably do not substantially contain boron oxide in their composition. That is, the obtained thermoplastic resin composition preferably does not substantially contain boron oxide. By substantially not containing boron oxide, the physical properties of the composition, particularly the vibration fatigue resistance, become better. Here, "substantially free of boron oxide" means that it contains no boron oxide at all, or contains only a very small amount that does not interfere with the properties of the resulting thermoplastic resin composition (particularly, vibration fatigue resistance). Specifically, the content of boron oxide is preferably less than 5% by mass, more preferably less than 1% by mass, still more preferably less than 0.1% by mass, and particularly preferably 0% by mass, based on the total mass of the thermoplastic resin composition.

[0087] (Other components) The above other components are components other than the above thermoplastic resin and the above glass fiber, and examples include copper compounds, metal halide compounds, other resin components, combinations thereof, and the like.

[0088] -Copper compound- In the melt-kneading step, a copper compound can be blended in addition to the thermoplastic resin and the glass fiber. Examples of the copper compound include inorganic acid copper salts such as cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide (copper iodide), copper sulfate, copper phosphate, copper borate, and copper nitrate; and organic acid copper salts such as copper acetate, copper propionate, copper benzoate, copper adipate, copper terephthalate, copper isophthalate, and copper stearate. Alternatively, a copper complex salt coordinated with a chelating agent can be used. Among them, it is preferable to use cuprous iodide. These copper compounds can be used alone or in combination of two or more.

[0089] The blending amount of the copper compound is preferably from 0.0001 part by mass to 1 part by mass, more preferably from 0.005 part by mass to 0.2 part by mass, and still more preferably from 0.02 part by mass to 0.1 part by mass, based on 100 parts by mass of the thermoplastic resin.

[0090] -Metal halide compound- In the melt-kneading step, a metal halide compound can be blended in addition to the thermoplastic resin and the glass fiber. As the metal halide, potassium halide is preferable. Examples of the potassium halide include potassium iodide, potassium bromide, potassium chloride, etc. Among them, potassium iodide is preferable. These potassium halides may be used alone or in combination of two or more.

[0091] The blending amount of the metal halide is preferably 0.0001 part by mass or more and 1 part by mass or less, more preferably 0.005 part by mass or more and 0.2 part by mass or less, and even more preferably 0.02 part by mass or more and 0.15 part by mass or less with respect to 100 parts by mass of the thermoplastic resin.

[0092] -Other resin components- In the production method of the present embodiment, as the resin used as a raw material, in addition to the thermoplastic resin having a relative formic acid viscosity within the above range, other thermoplastic resins having a relative formic acid viscosity outside the above range can be used as long as the properties of the obtained thermoplastic resin composition are not impaired.

[0093] Examples of other thermoplastic resins having a relative formic acid viscosity outside the above range include general-purpose resins such as polyethylene, polypropylene, ethylene-propylene copolymer, polystyrene, ABS resin, AS resin, and acrylic resin; aliphatic polyamide resins such as polyamide 6 and polyamide 11; polycarbonate, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, etc. These other thermoplastic resins are preferably used after being modified with a modifier such as maleic anhydride or a glycidyl group-containing monomer. Among them, resins having no functional groups such as polyethylene, polypropylene, or ethylene-propylene copolymer are preferably used after being modified.

[0094] [Pre-drying step] In the pre-drying step, the above melt-kneaded product is heated at a temperature T1 °C within the range represented by the following formula (V) and dried to remove moisture and oligomers in the melt-kneaded product, thereby obtaining a pre-dried melt-kneaded product. Tm - 185 ≤ T1 < Tm - 130 (V) (In the formula, Tm is the melting point (°C) of the above thermoplastic resin.)

[0095] The melt-kneaded product obtained in the melt-kneading step may be directly introduced from the extruder into a pre-dryer for pre-drying, or may be added to the pre-dryer for pre-drying after being once packaged in a paper bag or the like and stored.

[0096] The pre-drying step can be carried out either in a continuous manner or in a batch manner. The pre-dryer may be vertical or horizontal. The pre-drying may be carried out with stirring or may be static. The stirring type pre-dryer may be of a main body rotation type or may be of a stirring type by a stirring blade or the like. The static type pre-dryer may be of a box-shaped shelf type, may be of a flat type, or may be of a hopper type.

[0097] The heating method in the pre-drying step may be a method of heating the inside by heating the dryer to a predetermined temperature using a heat medium such as electricity or oil, or may be a method of heating by directly blowing hot air or the like onto the content, or may be a method of heating by utilizing the heat storage of the melt-kneaded product itself obtained in the melt-kneading step.

[0098] The pre-drying time of the melt-kneaded product is preferably 30 minutes or more, more preferably 2 hours or more. Also, it is preferably 24 hours or less. When the pre-drying time is at least the above lower limit value, oligomers can be efficiently removed from the melt-kneaded product. When the pre-drying time is at most the above upper limit value, coloring (yellowing) of the composition can be more effectively suppressed during the pre-drying step.

[0099] [Heating Step] In the heating step, the pre-dried melt-kneaded product is heated at a temperature T2 °C within the range represented by the following formula (VI), and the thermoplastic resin in the pre-dried melt-kneaded product is polymerized to a higher molecular weight by solid-phase polymerization or the like to obtain a thermoplastic resin composition. Tm - 130 ≤ T2 ≤ Tm - 10 (VI) (In the formula, Tm is the melting point (°C) of the above thermoplastic resin.)

[0100] When the temperature T2 °C is equal to or higher than "the melting point of the thermoplastic resin - 130 °C", the polymerization reaction can be accelerated, and polymerization can be carried out efficiently to reach the target degree of polymerization. When the temperature T2 °C is equal to or lower than "the melting point of the thermoplastic resin - 10 °C", the thermoplastic resin is less likely to undergo thermal decomposition, and coloring deterioration on the polymer surface can be suppressed. Also, fusion of solid prepolymers with each other can be more effectively suppressed. The temperature T2 °C is preferably in the range of Tm - 110 °C or higher and Tm - 30 °C or lower.

[0101] The melting point Tm of the thermoplastic resin can be measured according to JIS-K7121. As a measuring device, for example, Diamond DSC manufactured by PERKIN-ELMER can be used. Specifically, it can be measured using the method shown in the examples described later.

[0102] In the heating step, the heating time of the pre-dried melt-kneaded product is preferably 30 minutes or more and 24 hours or less, more preferably 30 minutes or more and 15 hours or less, within the above temperature range. When the heating time is equal to or longer than the above lower limit value, the thermoplastic resin composition can reach the desired viscosity (degree of polymerization of the thermoplastic resin) more efficiently. When the heating time is equal to or shorter than the above upper limit value, fusion of low-order condensates and coloring (yellowing) of the composition during solid-phase polymerization can be more effectively suppressed.

[0103] The solid-phase polymerization reaction can be carried out either in a continuous mode or a batch mode. The solid-phase polymerization reactor may be vertical or horizontal. It is preferable to stir the solid-phase polymerization reaction to enhance the uniformity of the reaction. The polymerization reactor may be of a main body rotation type or a stirring type with a stirring blade or the like. Among them, the solid-phase polymerization reaction in the heating step is preferably carried out continuously.

[0104] The solid-phase polymerization reaction in the heating step can be carried out either under vacuum or under a gas flow. The solid-phase polymerization reaction under a gas flow is preferably carried out under an inert gas flow such as nitrogen gas. The above heating step is preferably carried out under an inert gas atmosphere with an oxygen concentration of 5 ppm or less or under vacuum at a temperature of T2 °C.

[0105] When the solid-phase polymerization is carried out under an inert gas stream, it is preferably carried out under an inert gas atmosphere with an oxygen concentration of 5 ppm or less. When the oxygen concentration is below the above upper limit value, the resulting thermoplastic resin composition is less likely to undergo oxidative degradation. As a result, a reaction in which molecular chains are broken is less likely to occur, and the rate at which the molecular weight increases (polymerization reaction rate) is less likely to decrease, making it easier to obtain a thermoplastic resin composition with a predetermined molecular weight. In addition, a decrease in the mechanical properties and yellowing of the resulting thermoplastic resin composition can be more effectively suppressed.

[0106] When the solid-phase polymerization is carried out under an inert gas stream, it is preferable to form a particle layer from the melt-kneaded material and carry out a solid-phase reaction while supplying a predetermined amount of inert gas to a predetermined position of the height of the particle layer. Specifically, at a position with a height of 0 times or more and 0.8 times or less, preferably 0 times or more and 0.5 times or less, of the height h of the particle layer, the inert gas is supplied in an amount of 0.1 Nm 3 / hour or more and 10 Nm 3 / hour or less, preferably 0.14 Nm 3 / hour or more and 10 Nm 3 / hour or less while carrying out the solid-phase polymerization reaction.

[0107] The height h of the particle layer is defined as follows. Open the solid-phase polymerization reactor, charge the particles or pellets of the melt-kneaded material in an amount equivalent to the operation under normal temperature and atmospheric pressure, and measure the height of the particle layer with the bottom of the reactor having a gas supply port as a reference (h = 0) while passing a predetermined amount of inert gas, and set it as h. When the height surface of the particle layer is not constant, the average value of the highest height and the lowest height is set as h.

[0108] The ratio of the viscosity number VN of the thermoplastic resin composition after the heating step to the viscosity number VN of the thermoplastic resin added in the melt-kneading step (viscosity number VN of the thermoplastic resin composition after the heating step / viscosity number VN of the thermoplastic resin added in the melt-kneading step) is preferably 1.0 to 5.0, more preferably 1.1 to 4.0, and even more preferably 1.2 to 3.0 from the viewpoint of further improving the vibration fatigue resistance and further suppressing coloring. Also, the ratio of the formic acid relative viscosity (RV) of the thermoplastic resin composition after the heating step to the formic acid relative viscosity (RV) of the thermoplastic resin added in the melt-kneading step (formic acid relative viscosity (RV) of the thermoplastic resin composition after the heating step / formic acid relative viscosity (RV) of the thermoplastic resin added in the melt-kneading step) is preferably 1.0 to 9.0, more preferably 1.1 to 8.0, and even more preferably 1.2 to 7.0 from the viewpoint of further improving the vibration fatigue resistance and further suppressing coloring.

[0109] (Thermoplastic resin composition) The thermoplastic resin composition obtained by the production method of the present embodiment may be the polyamide resin composition of the above-described present embodiment. The thermoplastic resin composition obtained by the production method of the present embodiment preferably has an average viscosity number of 200 g / mL or more and 350 g / mL or less, more preferably 210 g / mL or more and 330 g / mL or less, and even more preferably 220 g / mL or more and 300 g / mL or less. When the average viscosity number is at least the above lower limit value, the abrasion resistance is better, while when the average viscosity number is at most the above upper limit value, the moldability is better when molded for each application. The average viscosity number can be measured by the method described in the examples below.

[0110] The content of the glass fiber in the thermoplastic resin composition is preferably 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. When the content of the glass fiber is at least the above lower limit value, the rigidity and strength of the thermoplastic resin composition can be further increased, while when it is at most the above upper limit value, the moldability is better when the thermoplastic resin composition is molded for each application.

[0111] The weight average fiber length of the glass fiber contained in the thermoplastic resin composition is preferably 100 μm or more and 1000 μm or less. When the weight average fiber length is at least the above lower limit value, the reinforcing effect can be more sufficiently exhibited, and the impact strength and tensile strength can be further improved. On the other hand, when the weight average fiber length is at most the above upper limit value, when the thermoplastic resin composition is pelletized, it becomes difficult for the glass fiber to protrude from the pellet. As a result, it becomes difficult for the bulk density of the pellet to decrease.

[0112] The weight average fiber length of the glass fiber contained in the thermoplastic resin composition can be measured, for example, using the following method. First, the thermoplastic resin composition is dissolved in a solvent in which the thermoplastic resin is soluble, such as formic acid. Next, for example, 100 or more glass fibers are arbitrarily selected from the obtained insoluble components, and the total mass of the glass fibers is measured. Next, the fiber length of each glass fiber is measured by observing the glass fiber with an optical microscope, a scanning electron microscope, etc., and the value obtained by dividing the total value by the total mass of the glass fibers can be determined as the weight average fiber length.

[0113] Since the thermoplastic resin composition obtained by the production method of the present embodiment is excellent in vibration fatigue resistance, it is suitably used, for example, for automotive parts, electronic and electrical parts, industrial machine parts, various gears, etc.

Examples

[0114] Hereinafter, the present invention will be described with specific examples and comparative examples, but the present invention is not limited to the following examples.

[0115] {Examples 1-1 to 1-14, Comparative Examples 1-1 to 1-3} [Raw materials] <Production of polyamide resin> (Production Example 1-1: Production of polyamide resin A1-1 (polyamide 66)) 15,000 g of an equimolar salt of adipic acid and hexamethylenediamine, and 0.5 mol% excess adipic acid with respect to the equimolar salt component were dissolved in 15,000 g of distilled water to obtain a 50 mass% aqueous solution of the raw material monomers. The obtained aqueous solution was charged into an autoclave with an internal volume of 40 L, and the inside of the autoclave was replaced with nitrogen. While stirring this aqueous solution at a temperature of 110°C or higher and 150°C or lower, water vapor was gradually removed to concentrate the solution to a concentration of 70 mass%. Then, the internal temperature was raised to 220°C. At this time, the pressure in the autoclave increased to 1.8 MPa. While gradually removing water vapor and maintaining the pressure at 1.8 MPa, the reaction was carried out for 1 hour until the internal temperature reached 270°C. Then, the pressure was reduced to atmospheric pressure over about 1 hour. After reaching atmospheric pressure, it was discharged in a strand shape from the lower nozzle, cooled with water, and cut to obtain pellets of polyamide resin A1-1. The obtained pellets were dried in a nitrogen stream at 90°C for 4 hours. The formic acid relative viscosity (RV) of these pellets was 48, and the melting point was 265°C.

[0116] (Production Example 1-2: Production of polyamide resin A1-2 (polyamide 66)) Before discharging from the lower nozzle, the inside of the tank was maintained under a reduced pressure of 100 torr (1.33×10 4 Pa) for 5 minutes using a vacuum device, and pellets of polyamide resin A1-2 were produced in the same manner as in Production Example 1-1. The formic acid relative viscosity (RV) of these pellets was 60, and the melting point was 264°C.

[0117] <Production of inorganic filler> (Production Example 1-3: Production of inorganic filler B1-1) First, the following (x-1) to (x-4) were diluted with water so that the solid content was 2 mass% of polyurethane resin, 4 mass% of maleic anhydride-butadiene copolymer, 0.6 mass% of γ-aminopropyltriethoxysilane, and 0.1 mass% of carnauba wax to obtain a glass fiber sizing agent. The obtained glass fiber sizing agent was attached to glass fibers having a number average fiber diameter of 7 μm. The attachment method was such that the sizing agent was attached to the glass fibers by an applicator provided during the winding of the melt-spun glass fibers onto a rotating drum. Thereafter, the glass fibers to which the sizing agent was attached were dried to obtain rovings of glass fiber bundles surface-treated with the above glass fiber sizing agent. At that time, the glass fibers were formed into bundles of 1,000. The amount of the glass fiber sizing agent attached to the glass fibers was 0.6% by mass. The obtained rovings were cut into lengths of 3 mm to obtain an inorganic filler B1-1 (chopped strand, hereinafter also simply abbreviated as "(B1-1)").

[0118] In addition, the components (x1-1) to (x1-4) constituting the sizing agent used when producing the above inorganic filler are as follows. (x1-1) Polyurethane resin emulsion Trade name: Bondic (registered trademark) 1050 (manufactured by Dainippon Ink and Chemicals, Inc.) (aqueous solution with a solid content of 50% by mass) (x1-2) Maleic anhydride-based copolymer emulsion Trade name: Acrobinder (registered trademark) BG-7 (manufactured by Sanyo Chemical Industries, Ltd.) (aqueous solution with a solid content of 25% by mass) (x1-3) Amino silane-based coupling agent Trade name: KBE-903 (manufactured by Shin-Etsu Chemical Co., Ltd.) γ-aminopropyltriethoxysilane (x1-4) Lubricant Trade name: Carnauba wax (manufactured by Kato Yoko Co., Ltd.)

[0119] (Production Example 1-4: Production of Inorganic Filler B1-2) An inorganic filler B1-2 (chopped strand, hereinafter also simply abbreviated as "(B1-2)") was obtained in the same manner as in Production Example 1-3 except that glass fibers having a number average fiber diameter of 5 μm were used instead of glass fibers having a number average fiber diameter of 7 μm. The amount of the glass fiber sizing agent attached to the glass fibers was 0.7% by mass.

[0120] (Production Example 1-5: Production of Inorganic Filler B1-3) An inorganic filler (B1-3) (chopped strand, hereinafter also simply abbreviated as "(B1-3)") was obtained in the same manner as in Production Example 1-3, except that glass fibers with a number average fiber diameter of 13 μm were used instead of glass fibers with a number average fiber diameter of 7 μm. The adhesion amount of the glass fiber sizing agent to the glass fibers was 0.4% by mass.

[0121] [Other Raw Materials] In addition to the above-produced raw materials, the following raw materials were further used. ·Copper compound Copper iodide: Copper(I) iodide, manufactured by Wako Pure Chemical Industries, Ltd. ·Metal halide Potassium iodide: Potassium iodide, manufactured by Wako Pure Chemical Industries, Ltd.

[0122] [Evaluation] The following evaluations were performed on the polyamide resin compositions of each sample obtained by the above method. The evaluation results are shown in Table 1.

[0123] (Production of Molded Products) The molded products used for each physical property measurement and each evaluation were manufactured using the method shown below. The apparatus used was "NEX-50III" or "NEX-50IV" manufactured by Nissei Plastic Industrial Co., Ltd. The cylinder temperature was set at 290 °C and the mold temperature was set at 120 °C. Using the injection molding conditions of injection for 10 seconds and cooling for 10 seconds, each polyamide composition was molded up to 100 shots to obtain molded products (ISO test pieces).

[0124] (1) Formic Acid Relative Viscosity (RV) The formic acid relative viscosity (RV) of the polyamide resin as a raw material and the polyamide resin compositions obtained in the examples and comparative examples was measured in accordance with ASTM D789. More specifically, the RV value measured at 25 °C using a solution prepared by dissolving the polyamide resin in 90% by mass formic acid (10% by mass water) to a concentration of 8.4% by mass was adopted.

[0125] (2) Melt Shear Viscosity η (Pa·s) The polyamide resin composition after solid-phase polymerization was measured from 30°C to 300°C at a heating rate of 20°C / min using a Diamond DSC manufactured by PERKIN-ELMER in accordance with JIS-K7121. Based on the obtained melting point Tm, the melt shear viscosity η at a shear rate of 1000 sec -1 was used to evaluate the fluidity at. The specific measurement method was to use a twin capillary rheometer RH7-2 type manufactured by ROSAND, UK, Barrel diameter: 15 mm, Long capillary die: Capillary diameter 1 mm, capillary length 16 mm, inlet angle 180 degrees Short capillary die: Capillary diameter 1 mm, capillary length 0.25 mm, inlet angle 180 degrees and measured under the above temperature conditions.

[0126] (3) Evaluation of the surface gloss of the molded product The gripping part of the molded product obtained by the above manufacturing method was measured for 60-degree gloss in accordance with JIS-K7150 using a gloss meter (manufactured by HORIBA, IG320). Based on the measured surface gloss value, evaluation was carried out according to the following evaluation criteria. A (excellent): 60 or more B (good): 55 or more and less than 60 C (acceptable): 50 or more and less than 55 D (unacceptable): less than 50

[0127] (4) Evaluation of GF floating on the surface of the molded product Regarding the appearance of the gripping part of the molded product obtained by the above manufacturing method, the GF floating on the surface of the molded product was visually judged and evaluated. (Evaluation criteria) A (excellent): No GF floating is visible on the surface of the molded product. B (good): Slight GF floating is visible on the surface of the molded product. C (acceptable): GF floating is visible on the surface of the molded product. D (unacceptable): GF floating is prominent on the surface of the molded product.

[0128] (5) Evaluation of the surface appearance of the molded product Regarding the appearance of the gripping part of the molded product obtained by the above manufacturing method, the sink marks, avatars, silver, etc. on the surface of the molded product were comprehensively judged and evaluated. (Evaluation Criteria) A (Excellent): No sink marks, avatars, etc. are visible on the surface of the molded product. B (Good): Slight sink marks, avatars, etc. are visible on the surface of the molded product. C (Fair): Sink marks, avatars, etc. are visible on the surface of the molded product. D (Poor): Sink marks, avatars, etc. are prominent on the surface of the molded product.

[0129] Using the above-described constituent components, polyamide resin compositions of each sample were produced under the conditions shown below.

[0130] [Example 1-1: Production of Polyamide Resin Composition PA1-a1] (1) Melt-Kneading Step Using a twin-screw extruder with a screw diameter of 26 mm (manufactured by Coperion GmbH, trade name "ZSK26MC") equipped with a melting zone and a kneading zone, a mixture obtained by attaching a copper compound and a halide to the polyamide resin A1-1 obtained in Production Example 1-1 was supplied as a top feed according to the compounding composition described in Table 1, and the inorganic filler B1-1 obtained in Production Example 1-3 was supplied from a side feed arranged in front of the kneading zone. Melting kneading was carried out under extrusion conditions of a set temperature of 290°C, a screw rotation speed of 300 rpm, and a discharge rate of 30 kg / h. The strands extruded from the die were cooled by a strand bath and cut by a strand cutter to obtain pellets. (2) Heating Step (Solid-Phase Polymerization) 5 T of the polyamide resin composition pellets obtained in the above-mentioned (1) melt-kneading step were placed in a batch-type tumbler-type solid-phase polymerization reaction tank (with jacket), and while stirring, the temperature was raised to 50 °C with the set temperature of the heat medium in the jacket being 50 °C, and the system waited until the pellet temperature reached 50 °C. After confirming that the temperature of the polyamide resin composition pellets had reached 50 °C, the pressure reduction in the tank was started, and the temperature was raised at a set temperature of 215 °C and a heating rate of 12 °C / hour, which was taken as the start time of solid-phase polymerization. Heating was stopped 25 hours after the start of solid-phase polymerization, and solid-phase polymerization was terminated. The final degree of pressure reduction was 0.0010 MPa in absolute pressure. The temperature was lowered until the pellet temperature reached 60 °C, the pressure reduction was stopped, and after returning to normal pressure, the pellets were discharged from the tank. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 170, and the melt shear viscosity was 225 Pa·s.

[0131] [Example 1-2: Production of Polyamide Resin Composition PA1-a2] Melt-kneading was carried out in the same manner as in Example 1-1 to obtain pellets. Solid-phase polymerization was carried out in the same manner as in Example 1 except that the set temperature was 230 °C, the heating rate was 14 °C / hour, and the solid-phase polymerization time was 20 hours. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 334, and the melt shear viscosity was 330 Pa·s.

[0132] [Example 1-3: Production of Polyamide Resin Composition PA1-a3) Except that the polyamide resin A1-1 obtained in Production Example 1-1 was replaced with the polyamide resin A1-2 obtained in Production Example 1-2, melt-kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of the polyamide resin composition PA1-a3. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 185, and the melt shear viscosity was 240 Pa·s.

[0133] [Example 1-4: Production of Polyamide Resin Composition PA1-a4] Except that the amount of the inorganic filler B1-1 was reduced to the amount shown in Table 1 in the melt-kneading step, and the heating rate was 20 °C / hour and the heating time was 17 hours in the heating step, melt-kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of the polyamide resin composition PA1-a4. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 180, and the melt shear viscosity was 215 Pa·s.

[0134] [Example 1-5: Production of polyamide resin composition PA1-a5] Except that the compounding amount of the inorganic filler B1-1 was increased to the amount shown in Table 1 in the melt-kneading step, melt-kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of the polyamide resin composition PA1-a5. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 190, and the melt shear viscosity was 460 Pa·s.

[0135] [Example 1-6: Production of polyamide resin composition PA1-a6] Except that the compounding amount of the inorganic filler B1-1 was increased to the amount shown in Table 1 and the set temperature was 190 °C, the heating rate was 10 °C / hour, and the heating time was 33 hours in the heating step, melt-kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of the polyamide resin composition PA1-a6. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 178, and the melt shear viscosity was 280 Pa·s.

[0136] [Example 1-7: Production of polyamide resin composition PA1-a7] Except that the inorganic filler B1-2 was used instead of the inorganic filler B1-1 and the amount of the inorganic filler B1-2 was set to the amount shown in Table 1, melt-kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of the polyamide resin composition PA1-a7. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 172, and the melt shear viscosity was 315 Pa·s.

[0137] [Example 1-8: Production of polyamide resin composition PA1-a8] Using inorganic filler B1-3 instead of inorganic filler B1-1 and setting the amount of inorganic filler B1-3 to the amount shown in Table 1, melt-kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of polyamide resin composition PA1-a8. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 177, and the melt shear viscosity was 290 Pa·s.

[0138] [Example 1-9: Production of polyamide resin composition PA1-a9] (1) Melt-kneading step Using a twin-screw extruder with a screw diameter of 26 mm (manufactured by Coperion K-Tron GmbH, trade name "ZSK26MC") equipped with a screw having a melting zone and a kneading zone, a mixture obtained by attaching a copper compound and a halide to polyamide resin A1-1 obtained in Production Example 1-1 was fed as a top feed according to the compounding composition described in Table 1, and inorganic filler B1-1 obtained in Production Example 1-3 was fed from a side feed arranged in front of the kneading zone. Melt-kneading was carried out under extrusion conditions of a set temperature of 290°C, a screw rotation speed of 300 rpm, and a discharge rate of 30 kg / h. The strand extruded from the die was cooled by a strand bath and cut by a strand cutter to obtain pellets. (2) Heating step (solid-phase polymerization) 11 kg of the polyamide resin composition pellets obtained in the above (1) melt-kneading step were put into a conical ribbon vacuum dryer (manufactured by Okawara Mfg. Co., Ltd., trade name Ribocone RM-10V), and nitrogen was flowed at 10 L / min while stirring, and nitrogen substitution was carried out for 15 minutes. While flowing nitrogen at 10 L / min and stirring, the temperature was raised to 50°C at a set temperature, and the pellets were waited until the temperature reached 50°C. After confirming that the temperature of the polyamide resin composition pellets reached 50°C, heating was started at a set temperature of 160°C and a heating rate of 130°C / hour, which was taken as the start time of solid-phase polymerization. Heating was stopped 48 hours after the start of solid-phase polymerization to terminate the solid-phase polymerization. The temperature was lowered while flowing nitrogen until the pellet temperature reached 60°C, and the pellets were discharged from the tank. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 145, and the melt shear viscosity was 270 Pa·s.

[0139] [Example 1-10: Production of Polyamide Resin Composition PA1-a10] Melting kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1, except that the heating rate was 130 °C / hour and the heating time was 8 hours in the heating process, and pellets of the polyamide resin composition PA1-a10 were obtained. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 180, and the melt shear viscosity was 310 Pa·s.

[0140] [Example 1-11: Production of Polyamide Resin Composition PA1-a11] Melting kneading and solid-phase polymerization were carried out in the same manner as in Example 1-6, except that the heating rate was 80 °C / hour and the heating time was 10 hours in the heating process, and pellets of the polyamide resin composition PA1-a11 were obtained. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 200, and the melt shear viscosity was 400 Pa·s.

[0141] [Example 1-12: Production of Polyamide Resin Composition PA1-a12] Melting kneading and solid-phase polymerization were carried out in the same manner as in Example 1-6, except that the heating rate was 130 °C / hour and the heating time was 8 hours in the heating process, and pellets of the polyamide resin composition PA1-a12 were obtained. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 176, and the melt shear viscosity was 379 Pa·s.

[0142] [Example 1-13: Production of Polyamide Resin Composition PA1-a13] Melting kneading and solid-phase polymerization were carried out in the same manner as in Example 1-5, except that the heating rate was 130 °C / hour and the heating time was 8 hours in the heating process, and pellets of the polyamide resin composition PA1-a13 were obtained. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 190, and the melt shear viscosity was 521 Pa·s.

[0143] [Example 1-14: Production of Polyamide Resin Composition PA1-a14] Except that the set temperature was 215°C, the heating rate was 130°C / hour, and the heating time was 8 hours in the heating process, melt kneading and solid-phase polymerization were carried out in the same manner as in Examples 1-9 to obtain pellets of the polyamide resin composition PA1-a14. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 176, and the melt shear viscosity was 380 Pa·s.

[0144] [Comparative Example 1-1: Production of Polyamide Resin Composition PA1-b1] Except that the set temperature was 230°C, the heating rate was 230°C / hour, and the heating time was 5 hours in the heating process, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1-1 to obtain pellets of the polyamide resin composition PA1-b1. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 174, and the melt shear viscosity was 341 Pa·s.

[0145] [Comparative Example 1-2: Production of Polyamide Resin Composition PA1-b2] Except that the set temperature was 230°C, the heating rate was 230°C / hour, and the heating time was 5 hours in the heating process, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1-3 to obtain pellets of the polyamide resin composition PA1-b2. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 186, and the melt shear viscosity was 351 Pa·s.

[0146] [Comparative Example 1-3: Production of Polyamide Resin Composition PA1-b3] Except that the set temperature was 230°C, the heating rate was 230°C / hour, and the heating time was 5 hours in the heating process, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1-6 to obtain pellets of the polyamide resin composition PA1-b3. The formic acid relative viscosity (RV) of the polyamide resin composition after solid-phase polymerization was 178, and the melt shear viscosity was 409 Pa·s.

[0147]

Table 1

[0148] From the results in Table 1, it can be seen that the polyamide resin compositions PA1-a1 to PA1-a14 (Examples 1-1 to 1-14) are superior to the polyamide resin compositions PA1-b1 to PA1-b3 (Comparative Examples 1-1 to 1-3) in melt processability, surface gloss of the molded product, GF floating, and appearance.

[0149] {Examples 2-1 to 2-14, Comparative Examples 2-1 to 2-4}

[0150] <Measurement Method of Physical Properties> [Physical Property 1] (Viscosity Number VN) Using pellets of polyamide, melt-kneaded product, and thermoplastic resin composition, in accordance with ISO307 (JIS-K6933), the viscosity number VN was measured. Specifically, at 25°C, in sulfuric acid with a concentration of 96% by mass, a solution with a concentration of 0.5% by mass of polyamide, melt-kneaded product, or thermoplastic resin composition was measured. When the sample contains a reinforcing material such as glass fiber, the ash content rate in the sample was measured in advance based on the provisions of ISO3451-4, for example, and the content rate of the polyamide resin after subtracting the ash content rate was used to calculate the content of the polyamide resin in the sample. In addition, the relative viscosity RV of formic acid can be measured by the same method as in the examples of the above Aspect 1.

[0151] [Physical Property 2] (Moisture Content) Regarding the pellets of the melt-kneaded product after the melt-kneading process and the pellets after the pre-drying process produced in the examples and comparative examples, the moisture content (mass ppm) in the pellets was measured using a Karl Fischer moisture meter (manufactured by Mitsubishi Chemical Analytech Co., Ltd., Coulometric titration type trace moisture measuring device CA-200 type) by a method compliant with ISO15512.

[0152] [Physical Property 3] (Melting Point) In accordance with JIS-K7121, the heat of fusion was measured using a Diamond-DSC manufactured by PERKIN-ELMER (hereinafter also referred to as "DSC measurement"). The DSC measurement was carried out under a nitrogen atmosphere. As the sample, about 10 mg of pellets of polyamide 66 produced in Production Examples 1 and 2 were used. Specifically, in the above DSC measurement, first, the sample was heated from 25°C to the melting point of polyamide + about 30°C (for example, 294°C for PA66) at a heating rate of 20°C / min. Next, it was held at the maximum temperature during the first heating for 3 minutes to completely melt the polyamide into a molten state once. Then, the sample was cooled to 25°C at a cooling rate of 20°C / min and held at 25°C for 3 minutes. Thereafter, when the sample was heated again at a heating rate of 20°C / min, the melting point of polyamide 66 was determined from the endothermic peak (melting peak) that appeared.

[0153] <Evaluation method> [Preparation of test pieces] Regarding the pellets of the thermoplastic resin compositions produced in the Examples and Comparative Examples, using an injection molding machine, in accordance with JIS-K7139, small tensile test pieces (type CP13) (3 mm thick) were produced as follows. As the injection molding apparatus, PS40E manufactured by Nissei Plastic Industrial Co., Ltd. was used, and a mold for taking two of the above small tensile test pieces was attached. The cylinder temperature was set at the melting point of polyamide + about 15°C (for example, 280°C for PA66), and the mold temperature was 80°C. Furthermore, under the injection molding conditions of injection for 10 seconds, cooling for 7 seconds, and a plasticization amount of 30 mm (cushion amount of about 10 mm), dumbbell-shaped small tensile test pieces were obtained from the pellets of the thermoplastic resin composition.

[0154] [Evaluation 1] (Amount of oligomer generated) Regarding the amount of oligomer generated, the amount of deposits inside the apparatus during solid-phase polymerization was measured. After carrying out solid-phase polymerization under the conditions of the Examples described later, after removing the thermoplastic resin composition from the apparatus, the residues inside the apparatus were collected using a scraper or the like, and the weight was measured to obtain the amount of oligomer generated.

[0155] [Evaluation 2] (Average number of viscosities and coefficient of variation of the number of viscosities) Regarding the average viscosity number, the thermoplastic resin composition was produced 10 times each under the conditions of each of the following examples, and the arithmetic mean value μVN was calculated from the numerical values of 10 points of the viscosity number VN measured for each. Regarding the coefficient of variation of the viscosity number, the thermoplastic resin composition was produced 10 times each under the conditions of each of the examples in the same manner as described above, and the coefficient of variation of the viscosity number CVVN was calculated using the following formula from the numerical values of 10 points of the viscosity number meter measured for each. CVVN = (σVN / μVN) × 100 Here, σVN represents the standard deviation of the viscosity number, and μVN represents the arithmetic mean of the viscosity number.

[0156] <Raw materials> 1. Component (A): Production of polyamide [Production Example 2-1] (Polyamide A2-1: Production of polyamide 66) 15,000 g of an equimolar salt of adipic acid and hexamethylenediamine, and 0.5 mol% excess adipic acid with respect to the equimolar salt component were dissolved in 15,000 g of distilled water to obtain a 50 mass% aqueous solution of the raw material monomer. The obtained aqueous solution was charged into an autoclave with an internal volume of 40 L, and the inside of the autoclave was replaced with nitrogen. While stirring this aqueous solution at a temperature of 110 °C or higher and 150 °C or lower, water vapor was gradually removed to concentrate the solution to a concentration of 70 mass%. Thereafter, the internal temperature was raised to 220 °C. At this time, the pressure in the autoclave increased to 1.8 MPa. While gradually removing water vapor and maintaining the pressure at 1.8 MPa, the reaction was carried out for 1 hour until the internal temperature reached 270 °C. Thereafter, the pressure was gradually reduced to atmospheric pressure over about 1 hour, and after reaching atmospheric pressure, it was discharged in a strand shape from the lower nozzle, cooled with water, and cut to obtain pellets of polyamide A2-1. The obtained pellets were dried at 90 °C for 4 hours in a nitrogen stream. The formic acid relative viscosity (RV) of these pellets was 48, the viscosity number VN was 133 g / mL, and the melting point was 265 °C.

[0157] [Production Example 2-2] (Polyamide A2-2: Production of polyamide 66) Before discharging from the lower nozzle, the inside of the tank was evacuated to 100 torr (1.33×104 Pellets of polyamide A2-2 were produced in the same manner as in Production Example 2-1, except that they were maintained under reduced pressure in Pa) for 10 minutes. The relative viscosity (RV) of formic acid of these pellets was 85, the viscosity number VN was 188 g / mL, and the melting point was 264 °C.

[0158] 2. Component (B): Production of glass fiber [Production Example 2-3] (Production of glass fiber B2-1) First, (x2-1) to (x2-4) described below were diluted with water at a ratio such that the solid content was 2% by mass of polyurethane resin, 4% by mass of maleic anhydride-butadiene copolymer, 0.6% by mass of γ-aminopropyltriethoxysilane, and 0.1% by mass of carnauba wax, to obtain a glass fiber sizing agent. The obtained glass fiber sizing agent was attached to glass fibers (containing boron oxide) having a number average fiber diameter of 7 μm. The attachment method was such that the sizing agent was attached to the glass fibers by an applicator provided during the winding of the melt-spun glass fibers onto a rotating drum. Thereafter, the glass fibers to which the sizing agent was attached were dried to obtain rovings of glass fiber bundles surface-treated with the above glass fiber sizing agent. At that time, the glass fibers were made into bundles of 1,000. The amount of the glass fiber sizing agent attached to the glass fibers was 0.6% by mass. The obtained rovings were cut into lengths of 3 mm to obtain glass fiber B2-1 (chopped strand, hereinafter also simply abbreviated as "(B2-1)").

[0159] The components (x2-1) to (x2-4) constituting the sizing agent used when producing the fibrous reinforcing material are as follows. (x2-1) Polyurethane resin emulsion Trade name: Bondic (registered trademark) 1050 (manufactured by Dainippon Ink and Chemicals, Incorporated) (Aqueous solution with a solid content of 50% by mass) (x2-2) Maleic anhydride-based copolymer emulsion Trade name: Acrobinder (registered trademark) BG-7 (manufactured by Sanyo Chemical Industries, Ltd.) (Aqueous solution with a solid content of 25% by mass) (x2-3) Amino silane coupling agent Product name: KBE-903 (manufactured by Shin-Etsu Chemical Co., Ltd.) γ-Aminopropyltriethoxysilane (x2-4) Lubricant Product name: Carnauba wax (manufactured by Kato Yoko Co., Ltd.)

[0160] [Production Example 2-4] (Production of glass fiber B2-2) Except for using glass fiber (containing boron oxide) with a number average fiber diameter of 5 μm instead of glass fiber (containing boron oxide) with a number average fiber diameter of 7 μm, glass fiber B2-2 (chopped strand, hereinafter also simply abbreviated as "(B2-2)") was obtained in the same manner as in Production Example 2-3 above. The adhesion amount of the glass fiber sizing agent to the glass fiber was 0.7% by mass.

[0161] [Production Example 2-5] (Production of glass fiber B2-3) Except for using glass fiber (boron oxide-free) with a number average fiber diameter of 7 μm instead of glass fiber (containing boron oxide) with a number average fiber diameter of 7 μm, glass fiber B2-3 (chopped strand, hereinafter also simply abbreviated as "(B2-3)") was obtained in the same manner as in Production Example 2-3 above. The adhesion amount of the glass fiber sizing agent to the glass fiber was 0.6% by mass.

[0162] [Production Example 2-6] (Production of glass fiber B2-4) Except for using glass fiber (containing boron oxide) with a number average fiber diameter of 10 μm instead of glass fiber (containing boron oxide) with a number average fiber diameter of 7 μm, glass fiber B2-4 (chopped strand, hereinafter also simply abbreviated as "(B2-4)") was obtained in the same manner as in Production Example 2-3. The adhesion amount of the glass fiber sizing agent to the glass fiber was 0.5% by mass.

[0163] 3. Other raw materials In addition to the above-produced raw materials, the following raw materials were further used. (C) component: Copper compound Copper iodide: Copper(I) iodide, manufactured by Wako Pure Chemical Industries, Ltd. (D) component: Metal halide Potassium iodide: Potassium iodide, manufactured by Wako Pure Chemical Industries, Ltd.

[0164] <Manufacture of thermoplastic resin composition> [Examples 2-1 to 2-5, 2-13 to 2-14, Comparative Examples 2-1, 2-4] (Manufacture of thermoplastic resin compositions PA2-a1 to a5, a13 to a14, b1, b4) (1) Melt-kneading step Using a twin-screw extruder with a screw diameter of 26 mm (manufactured by Coperion GmbH, trade name "ZSK26MC"), a mixture obtained by attaching a copper compound and a metal halide to polyamide A2-1 obtained in Production Example 1 was supplied as a top feed according to the compounding composition shown in Table 2, and glass fiber was supplied as a side feed. Melt-kneading was carried out under the extrusion conditions of a set temperature of 290°C, a screw rotation speed of 300 rpm, and a discharge rate of 25 kg / h, and melt-kneaded pellets were obtained by pelletizing with a strand cutter. The viscosity number and moisture content of the obtained melt-kneaded pellets were as shown in Table 2.

[0165] (2) Pre-drying step The pellets obtained in "(1) Melt-kneading step" were put into a vacuum oven (manufactured by Espec Corporation, trade name VAC-300), and pre-dried at the drying temperature and time shown in Table 2 by standing in a vacuum atmosphere (method1).

[0166] (3) Heating step (solid-phase polymerization) 10 kg of the pellets obtained in "(2) Pre-drying step" were put into a conical ribbon vacuum dryer (manufactured by Okawara Mfg. Co., Ltd., trade name Ribocone RM-10V), and sufficient nitrogen substitution was carried out (oxygen concentration 4.2 ppm). While flowing nitrogen at 2 L / min and stirring, heating was carried out at the pellet temperature and heating time shown in Table 2. Then, while nitrogen was flowing, the temperature was lowered, and when it reached about 50°C, the pellets were taken out of the apparatus as they were, and pellets of thermoplastic resin compositions PA2-a1 to a5, a13 to a14, b1, b4 were obtained.

[0167] [Example 2-6] (Production of Thermoplastic Resin Composition PA2-a6) In the “(2) Pre-drying step”, except that it was put into a nitrogen blow dryer (manufactured by Yamato Scientific Co., Ltd., product name DN-43HI) and carried out by standing in a nitrogen atmosphere (method2), it was carried out in the same manner as in Example 2-1, and pellets of the thermoplastic resin composition PA2-a6 were obtained.

[0168] [Example 2-7] (Production of Thermoplastic Resin Composition PA2-a7) In the “(2) Pre-drying step”, except that it was put into a conical ribbon vacuum dryer (manufactured by Okawara Seisakusho Co., Ltd., product name Ribocone RM-10V) and carried out with stirring in a nitrogen atmosphere (method3), it was carried out in the same manner as in Example 2-1, and pellets of the thermoplastic resin composition PA2-a7 were obtained.

[0169] [Examples 2-8 to 2-12] (Production of Thermoplastic Resin Compositions PA2-a8 to a12) In the “(1) Melt-kneading step” of Example 2-1, solid-phase polymerization was carried out in the same manner as in Example 2-1 except that the compounding composition shown in Table 2 was changed, and pellets of the thermoplastic resin compositions PA2-a8 to a12 were obtained.

[0170] [Comparative Examples 2-2, 3] (Production of Thermoplastic Resin Compositions PA2-b2, 3) Regarding the pellets obtained in the “(1) Melt-kneading step” of Example 2-1 or the pellets prepared according to the compounding composition shown in Table 2, solid-phase polymerization was carried out in the same manner as in Example 1 except that the heating step was carried out without going through the pre-drying step, and pellets of the thermoplastic resin compositions PA2-b2, 3 were obtained.

[0171]

Table 2

[0172] From Table 2, in the polyamide resin compositions PA2-a1 to PA2-a14 (Examples 2-1 to 2-14), all evaluation items were good. In Example PA2-a11 using boron oxide-free glass fibers, substantially no boron oxide was contained, and the mass ratio of boron oxide in the thermoplastic resin composition was 0% by mass.

Industrial Applicability

[0173] According to the present invention, a polyamide resin composition excellent in melt processability and surface appearance can be provided. The polyamide resin composition of the present invention is suitably used, for example, for automotive parts, electronic and electrical parts, industrial machine parts, various gears, and the like.

[0174] Further, according to the production method of the present embodiment, a thermoplastic resin composition capable of suppressing the generation of oligomers during production and further improving the viscosity controllability during production can be obtained. The thermoplastic resin composition obtained by the production method of the present embodiment is suitably used, for example, for automotive parts, electronic and electrical parts, industrial machine parts, various gears, and the like.

Claims

1. A polyamide resin composition containing a polyamide resin and an inorganic filler, wherein the formic acid relative viscosity (RV) is 70 or more and 400 or less, The melting point of the polyamide resin composition + 15 °C, shear rate 1000 sec －１ The polyamide resin composition in which the melt shear viscosity [η] Pa·s at satisfies the following general formula (I). [η] ≤ 0.7 × [RV] + 7 × [inorganic filler] + 100... (I) (In formula (I), [η] represents the melt shear viscosity (Pa·s), [RV] represents the formic acid relative viscosity of the polyamide resin composition, and [inorganic filler] represents the inorganic filler content (mass%)).)

2. The polyamide resin composition according to claim 1, wherein the polyamide resin is at least one polyamide resin selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610, and polyamide 612.

3. The polyamide resin composition according to claim 1 or 2, wherein the inorganic filler is glass fiber having a number average fiber diameter of 3 μm or more and 15 μm or less.

4. The polyamide resin composition according to claim 1 or 2, wherein the inorganic filler is glass fiber having a number average fiber diameter of 3 μm or more and 9 μm or less.

5. A melt kneading step of adding 5 to 100 parts by mass of an inorganic filler to 100 parts by mass of a polyamide resin having a formic acid relative viscosity (RV) of 25 or more and 70 or less, and melt kneading to obtain melt kneaded product pellets; a heating step of subjecting the melt kneaded product pellets to solid phase polymerization at a set temperature T (°C) satisfying the following general formula (II): Tm - 130 ≤ T ≤ Tm - 10... (II) (In formula (II), T represents the set temperature (°C), and Tm represents the melting point (°C) of the polyamide resin.) The method for producing a polyamide resin composition according to claim 1, comprising the heating step of obtaining a polyamide resin composition.

6. The method for producing a polyamide resin composition according to claim 5, wherein in the heating step, solid phase polymerization is carried out with a heating time of 10 hours or more and 50 hours or less from the start of temperature increase.

7. The method for producing a polyamide resin composition according to claim 5, wherein in the heating step, solid phase polymerization is carried out under a reduced pressure of 0.015 MPa or less in absolute pressure or under an inert gas stream.

8. The melting point of the polyamide resin composition + 15 °C, shear rate 1000 sec －１ The method for producing a polyamide resin composition according to claim 5, wherein the melt shear viscosity [η] Pa·s at －１ satisfies the following general formula (III). 0.7 × [RV] + 7 × [inorganic filler] + 50 < [η] ≤ 0.7 × [RV] + 7 × [inorganic filler] + 100... (III) (In formula (III), [η] represents the melt shear viscosity (Pa·s), [RV] represents the formic acid relative viscosity of the polyamide resin composition, and [inorganic filler] represents the inorganic filler content (mass%).)

9. The melting point of the polyamide resin composition + 15°C, shear rate 1000 sec －１ The method for producing a polyamide resin composition according to claim 5, wherein the melt shear viscosity [η] Pa·s at －１ satisfies the following general formula (IV). 0.7 × [RV] + 7 × [Inorganic filler] - 50 ≤ [η] ≤ 0.7 × [RV] + 7 × [Inorganic filler] + 50... (IV) (In formula (IV), [η] represents the melt shear viscosity (Pa·s), [RV] represents the relative viscosity of the polyamide resin composition in formic acid, and [Inorganic filler] represents the inorganic filler content (mass%)).)

10. A melt-kneading step of adding 5 to 100 parts by mass of glass fiber to 100 parts by mass of a thermoplastic resin having a relative viscosity in formic acid (RV) of 25 or more and 70 or less, and melt-kneading to obtain a melt-kneaded product. A pre-drying step of heating and drying the melt-kneaded product at a temperature T1 °C within the range represented by the following formula (V). After the pre-drying step, a heating step of heating at a temperature T2 °C within the range represented by the following formula (VI) to obtain a thermoplastic resin composition. A method for producing a thermoplastic resin composition, comprising the above steps. Tm - 185 ≤ T1 < Tm - 130... (V) (In formula (V), Tm is the melting point (°C) of the thermoplastic resin.) Tm - 130 ≤ T2 ≤ Tm - 10... (VI) (In formula (VI), Tm is the melting point (°C) of the thermoplastic resin.)

11. The method for producing a thermoplastic resin composition according to claim 10, wherein in the pre-drying step, heating and drying are performed at a temperature T1 °C for 2 hours or more.

12. The method for producing a thermoplastic resin composition according to claim 10, wherein in the heating step, heating is performed at a temperature T2 °C for 30 minutes or more and 24 hours or less.

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