Method for manufacturing thermoplastic resin compositions

Abstract

To provide a method for producing a thermoplastic resin composition having improved vibration fatigue resistance.SOLUTION: A method for producing a thermoplastic resin composition includes: a melting / kneading process in which 5 pts.mass or more and 100 pts.mass or less of glass fiber having an average fiber diameter of 3 μm or more and 9 μm or less is added to 100 pts.mass of thermoplastic resin having a viscosity number VN of 80 or more and 200 or less, and the resin and the fiber are melted / kneaded to obtain a molten / kneaded product; and a heating process of heating the molten / kneaded product at a temperature T expressed by the following general formula (I) to obtain a thermoplastic resin composition, where a thermoplastic resin composition obtained in the melting / kneading process is round pellets or elliptic pellets. Tm-130°C≤T≤Tm-10°C (I)(in the formula, Tm denotes the melting point of the thermoplastic resin).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a thermoplastic resin composition. [Background technology]

[0002] Polyamide resins exhibit excellent properties as engineering plastics and are used in the manufacture of various machines and parts, including automobiles, machinery, and electrical and electronic components. In particular, due to their excellent mechanical properties and wear resistance, polyamide resins are widely used as molding materials for sliding parts such as gears, cams, and bearings.

[0003] In recent years, there has been a growing demand for higher performance in various types of machinery and components. Therefore, improvements have been made to enhance the mechanical properties or molding properties of polyamide resin molded products by incorporating various fillers into the polyamide resin. Examples of such fillers include tetrafluoroethylene resin particles as lubricants and glass fibers as reinforcing materials.

[0004] Patent Document 1 describes a polyamide resin composition suitable for molding sliding members, which is low friction and has excellent wear resistance, and is made by blending polytetrafluoroethylene particles and, if necessary, calcium titanate whiskers or glass fibers with a polyamide resin such as 46-nylon.

[0005] Patent Document 2 describes a resin composition for sliding materials, which is obtained by blending glass fibers, tetrafluoroethylene resin, and molybdenum disulfide with a polyamide resin, such as 66-nylon (66-polyamide resin).

[0006] Patent Document 3 describes a resin composition comprising a thermoplastic resin, such as nylon MXD6 or nylon 66, blended with reinforcing fibers, such as small-diameter glass fibers with a fiber diameter of approximately 6 μm to 8 μm, in an amount of 15% to 30% by mass. This resin composition is described as being particularly suitable for the manufacture of hollow tubes with excellent inner surface smoothness.

[0007] Patent Document 4 describes a reduction gear for an electric power steering device molded using a polyamide resin mixture. Patent Document 4 discloses the incorporation of fibrous materials such as glass fibers or carbon fibers into the polyamide resin mixture.

[0008] Patent Document 5 discloses the results of studies on various physical properties, primarily abrasion resistance, friction characteristics, and limiting PV value, of molded articles of known glass fiber-containing polyamide resin compositions. Specifically, it reports that particularly excellent abrasion resistance, friction characteristics, and limiting PV value can be achieved when a polyamide resin composition is molded, comprising polyamide 66 with a number-average molecular weight within a specific range, glass fibers having a specific average fiber diameter and average fiber length that are bundled using a specific sizing agent, and specific additives. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 185747 / 1983 [Patent Document 2] Japanese Unexamined Patent Publication No. 1-110558 [Patent Document 3] Japanese Patent Application Publication No. 8-41246 [Patent Document 4] Japanese Patent Publication No. 2003-83423 [Patent Document 5] Patent No. 4321590 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Generally, in the case of resins that are not reinforced with fillers, vibration fatigue characteristics are governed by the entanglement of polymer chains, so higher molecular weight materials exhibit better vibration fatigue resistance. In contrast, in the case of resins reinforced with fillers, the interface between the filler and the resin can be the starting point for vibration fatigue failure, and the lower the degree of adhesion at the interface between the filler and the resin, the lower the vibration fatigue resistance.

[0011] Therefore, the polyamide resin compositions described in Patent Documents 1 to 5 have the problem that, despite having a sufficiently high molecular weight, they contain fillers, and therefore their vibration fatigue resistance is not particularly sufficient.

[0012] Furthermore, small components, in particular, tend to have variations in physical properties, requiring consideration of filler filling properties. To improve filler filling properties, it is necessary to ensure uniform filler content within small components. Specifically, this can be achieved by making it more difficult for fillers to fall out during manufacturing.

[0013] The present invention has been made in view of the above circumstances, and provides a method for producing a thermoplastic resin composition that has improved vibration fatigue resistance and is less prone to filler detachment during manufacturing. [Means for solving the problem]

[0014] In other words, the present invention includes the following embodiments. [1] A method for producing a thermoplastic resin composition, comprising: a melt-kneading step of adding 5 to 100 parts by mass of glass fibers having an average fiber diameter of 3 μm to 9 μm to 100 parts by mass of a thermoplastic resin having a viscosity number VN of 80 to 200, and melt-kneading to obtain a melt-kneaded product; and a heating step of heating the melt-kneaded product at a temperature T represented by the following general formula (I) to obtain a thermoplastic resin composition, wherein the thermoplastic resin composition obtained in the melt-kneading step is in the form of round pellets or elliptical pellets. Tm-130℃≦T≦Tm-10℃ (I) (In the formula, Tm is the melting point of the thermoplastic resin.) [2] The method for producing the thermoplastic resin composition according to [1], wherein the thermoplastic resin composition has a viscosity number VN of 200 or more and 350 or less. [3] The average fiber length of the glass fiber is 100 μm or more and 1000 μm or less, and the method for producing a thermoplastic resin composition according to [1] or [2]. [4] The average fiber diameter of the glass fiber is 4 μm or more and 8 μm or less, and the method for producing a thermoplastic resin composition according to any one of [1] to [3]. [5] In the heating step, the heating at the temperature T is performed for 30 minutes or more and 15 hours or less, and the method for producing a thermoplastic resin composition according to any one of [1] to [4]. [6] In the heating step, the heating at the temperature T is performed in an inert gas atmosphere with an oxygen concentration of 5 ppm or less, and the method for producing a thermoplastic resin composition according to any one of [1] to [5]. [7] In the heating step, the heating at the temperature T is performed in an inert gas atmosphere with a moisture concentration of 10 ppm or less, and the method for producing a thermoplastic resin composition according to any one of [1] to [6]. [8] The thermoplastic resin is polyamide or polyester, and the method for producing a thermoplastic resin composition according to any one of [1] to [7]. [9] The polyamide is polyamide 6, polyamide 66, or polyamide 610, and the method for producing a thermoplastic resin composition according to [8].

[10] The value obtained by dividing the amount of amino terminal groups of the polyamide by the amount of carboxy terminal groups is 0.5 or more and 0.9 or less, and the method for producing a thermoplastic resin composition according to [8] or [9].

[11] The thermoplastic resin composition substantially does not contain boron oxide, and the method for producing a thermoplastic resin composition according to any one of [1] to

[10] . [Effect of the Invention]

[0015] According to the production method of the above aspect, a method for producing a thermoplastic resin composition can be provided, in which the vibration fatigue resistance is improved and the filler is less likely to fall off during production. [Embodiments for Carrying Out the Invention]

[0016] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0017] <Method for producing thermoplastic resin compositions> The method for producing the thermoplastic resin composition of this embodiment (hereinafter simply referred to as "the method for producing this embodiment") includes a melt-kneading step and a heating step. In the melt-kneading process, 5 to 100 parts by mass of glass fibers with an average fiber diameter of 3 μm to 9 μm are added to 100 parts by mass of a thermoplastic resin with a viscosity number VN of 80 to 200, and the mixture is melt-kneaded to obtain a melt-kneaded product. In the heating step, the molten mixture obtained in the molten mixture step is heated at a temperature T represented by the following general formula (I) to obtain a thermoplastic resin composition. Tm-130℃≦T≦Tm-10℃ (I) (In the formula, Tm is the melting point of the thermoplastic resin.)

[0018] In a typical method for producing thermoplastic resin compositions, a thermoplastic resin is polymerized to increase its molecular weight, then a filler such as glass fiber is added, and the mixture is melt-kneaded to obtain the thermoplastic resin composition.

[0019] In contrast, the manufacturing method of this embodiment involves melt-kneading a thermoplastic resin with low to medium molecular weight and glass fibers to obtain a melt-kneaded product. This improves the adhesion at the interface between the glass fibers and the thermoplastic resin. Subsequently, by solid-phase polymerization of the melt-kneaded product to increase its molecular weight, the improved adhesion at the interface between the glass fibers and the thermoplastic resin is maintained, and a thermoplastic resin composition with excellent vibration fatigue resistance can be obtained. Furthermore, by performing the melt-kneading process and the heating process in this order, the improved adhesion at the interface between the glass fibers and the thermoplastic resin is maintained, making it less likely for the filler to fall off during manufacturing.

[0020] The following describes in detail each step of the manufacturing method according to this embodiment.

[0021] [Melting and mixing process] In the melt-kneading process, glass fibers with an average fiber diameter of 3 μm to 9 μm are added to a thermoplastic resin having a viscosity number VN of 80 or more and 200 or less in a specific blending ratio, and the mixture is melt-kneaded to obtain a melt-kneaded product. Specifically, the glass fibers can be added in an amount of 5 to 100 parts by mass, preferably 10 to 100 parts by mass, and more preferably 15 to 100 parts by mass, per 100 parts by mass of the thermoplastic resin. By having a glass fiber content above the lower limit, a thermoplastic resin composition with enhanced rigidity and strength can be obtained. On the other hand, by having a glass fiber content below the upper limit, the resulting thermoplastic resin composition will have better moldability when molded for various applications.

[0022] Known devices can be used as the apparatus for melt-kneading. For example, melt-kneaders such as single-screw or twin-screw extruders, Banbury mixers, and mixing rolls can be used. Among these, multi-screw extruders equipped with a devolatilization mechanism (venting) device and side feeder equipment are preferred, and twin-screw extruders are more preferred.

[0023] When melt-kneading in an extruder, the molecular weight of the thermoplastic resin can be adjusted by appropriately setting the kneading conditions such as the resin temperature, degree of reduced pressure, and average residence time during extrusion. The resin temperature during melt-kneading is preferably above the melting point of the raw thermoplastic resin and below 370°C, more preferably between the melting point of the raw thermoplastic resin and 350°C, even more preferably between the melting point of the raw thermoplastic resin and 340°C, particularly preferably between the melting point of the raw thermoplastic resin and 335°C, and most preferably between the melting point of the raw thermoplastic resin and 330°C.

[0024] By setting the resin temperature during melt mixing above the lower limit of the raw thermoplastic resin, the melting of the raw thermoplastic resin becomes sufficient, which tends to further reduce the load on the extruder motor. Conversely, by setting the resin temperature during melt mixing below the upper limit of the raw thermoplastic resin, the decomposition of the raw thermoplastic resin itself tends to be further suppressed.

[0025] The weight-average molecular weight of the thermoplastic resin is controlled to range from low to medium molecular weight by appropriately setting the mixing conditions such as resin temperature, degree of reduced pressure, and average residence time during extrusion. Here, the range from low to medium molecular weight refers to the ranges of weight-average molecular weight between 10,000 and 70,000, between 15,000 and 65,000, and between 20,000 and 60,000.

[0026] For example, when using polyamide 66 with a melting point of 264°C as the raw material thermoplastic resin, the resin temperature during melt kneading is preferably 264°C to 360°C, more preferably 270°C to 350°C, even more preferably 275°C to 340°C, particularly preferably 280°C to 335°C, and most preferably 285°C to 330°C.

[0027] By raising the resin temperature during melt mixing above the lower limit, the polyamide 66 tends to melt more thoroughly, further reducing the load on the extruder motor. Conversely, by lowering the resin temperature during melt mixing below the upper limit, the decomposition of the polyamide 66 itself tends to be further suppressed.

[0028] Even when using polyamide resins other than polyamide 66 as the raw material, the temperature can be adjusted as appropriate according to its melting point. The resin temperature can be measured, for example, by directly contacting a thermometer such as a thermocouple with the molten mixture coming out of the extruder's nozzle (spindle). The resin temperature can be adjusted by adjusting the heater temperature of the extruder cylinder, or by appropriately adjusting the shear heat generated by changing the extruder's rotation speed and discharge rate.

[0029] The average residence time during melting and mixing is preferably 10 seconds to 120 seconds, more preferably 20 seconds to 100 seconds, even more preferably 25 seconds to 90 seconds, particularly preferably 30 seconds to 80 seconds, and most preferably 35 seconds to 70 seconds.

[0030] By ensuring the average residence time during melt mixing is above the lower limit, the molten mixture tends to be obtained more efficiently. Conversely, by ensuring the average residence time during melt mixing is below the upper limit, the extrusion discharge rate (production rate) tends to increase to some extent. As a result, the productivity of the polyamide resin composition also tends to improve.

[0031] Average residence time refers to the residence time when the residence time within the melting and mixing equipment is constant. If the residence time is uneven, it means the average of the shortest residence time and the longest residence time.

[0032] The average residence time is measured using the following method. Component X is added to the melt-mixing apparatus, and the start and end times of discharge are measured when component X is at its highest concentration. By averaging the measured start and end times of discharge, the average residence time can be measured. Component X is a component that can be distinguished from the raw polyamide resin used in the melt-mixing process, such as a coloring agent masterbatch during melt-mixing, or a resin with a different color from the raw polyamide resin used in the melt-mixing process. The average residence time mentioned above can be adjusted as appropriate by the discharge volume (discharge speed) and rotation speed of the extruder.

[0033] The thermoplastic resin composition obtained by melt kneading is in the form of resin pellets, which are either round or oval-shaped. The shape of the pellets can be round or oval depending on the cutting method used during the extrusion process.

[0034] Round or oval-shaped pellets can be obtained by cutting them using methods such as the underwater cut or the hot cut.

[0035] The round pellets may not be perfect spheres or ideally spherical shapes, but may be approximates a perfect sphere. In the case of round pellets, the preferred size is a pellet diameter (or the diameter at the widest point in the case of an approximate sphere) of 8 mm or less, 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.

[0036] The elliptical pellets may not be ellipsoids or perfect ellipsoids, but may have a shape that approximates an ellipsoid. In the case of elliptical pellets, the preferred size is 8 mm or less in terms of the semi-major axis of the pellet (or the point of maximum semi-major axis in the case of an ellipsoidal 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.

[0037] The raw materials used in the melting and mixing process are described in detail below.

[0038] (thermoplastic resin) The thermoplastic resin can have a viscosity number VN of 80 or more and 200 or less, preferably 100 or more and 200 or less, and more preferably 130 or more and 190 or less. Having a viscosity number VN within the above range ensures that the degree of polymerization of the thermoplastic resin is within an appropriate range, improving the adhesion at the interface between the glass fiber and the thermoplastic resin. The viscosity number VN is a value measured in accordance with ISO 307 (JIS-K6933). For example, it can be measured using the method shown in the examples described later.

[0039] Specifically, polyamide or polyester is preferred as the thermoplastic resin, with polyamide being more preferred.

[0040] Examples of polyamides include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polytetramethylene sevacamide (nylon 410), polypentamethylene adipamide (nylon 56), polypentamethylene sevacamide (nylon 510), polyhexamethylene sevacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polydecamethylene adipamide (nylon 106), polydecamethylene sevacamide (nylon 1010), and polydecamethylene. Methylene dodecamide (Nylon 1012), Polyundecaneamide (Nylon 11), Polydodecaneamide (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 Phthalamide / Polyhexamethylene isophthalamide copolymer (Nylon 6T / 6I), Polyhexamethylene terephthalamide / Polyundecaneamide copolymer (Nylon 6T / 11), Polyhexamethylene terephthalamide / Polydodecaneamide copolymer (Nylon 6T / 12), Polyhexamethylene adipamide / Polyhexamethylene terephthalamide / Polyhexamethylene isophthalamide copolymer (Nylon 66 / 6T / 6I), Polyxylylene adipamide (Nylon XD6), Polyxylylene sebaamide (Nylon XD10), Examples include 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), and polydodecamethylene terephthalamide (nylon 12T).In this context, " / " indicates a copolymer. These polyamides may be used individually or in combination of two or more.

[0041] Among these, polyamide 6, polyamide 66, or polyamide 610 are preferred, with polyamide 66 being particularly preferred. Polyamide 66 itself is a polyamide resin that is already generally known 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 lactams, aminocarboxylic acids, and combinations of other diamines and dicarboxylic acids, based on the total mass of all monomer units.

[0042] Furthermore, these polyamides may be commercially available or manufactured using known methods. Specific examples of methods for producing polyamides are not particularly limited, but include methods such as ring-opening polymerization of lactams, self-condensation of ω-aminocarboxylic acids, and condensation of diamines and dicarboxylic acids.

[0043] It is preferable that the ratio of the amount of amino-terminal groups to the amount of carboxy-terminal groups of the polyamide, [COOH] / [NH2], is between 0.5 and 0.9. When [COOH] / [NH2] is above the lower limit, solid-phase polymerization can be carried out more efficiently in the heating step described later. When [COOH] / [NH2] is below the upper limit, the interaction between the glass fiber surface and the polyamide ends becomes sufficiently large, resulting in sufficiently high physical properties of the resulting composition, particularly vibration fatigue resistance. The amounts of amino-terminal groups and carboxy-terminal groups are, for example, 1 The measurement can be performed using 1H-NMR. Specifically, it can be performed using the method shown in the examples described later.

[0044] Polyester is a polycondensate of a polycarboxylic acid (dicarboxylic acid) and a polyalcohol (diol). Examples of polycarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of polyalcohols 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 polyesters include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.

[0045] (Glass fiber) It is preferable to use glass fibers that are bound together with a known binder mainly composed of acrylic resin, epoxy resin, or urethane resin, and more preferably glass fibers bound together with a binder mainly composed of acrylic resin or epoxy resin. Furthermore, since further improvement in the mechanical properties of the resulting molded product can be expected, it is preferable to use glass fibers that have been pre-treated with a coupling agent such as an isocyanate compound, organosilane compound, organotitanate compound, organoborane compound, or epoxy compound.

[0046] The average fiber length of the glass fibers is preferably between 100 μm and 1000 μm. An average fiber length above the lower limit allows for a more sufficient reinforcing effect, further improving the impact strength and tensile strength of the resulting thermoplastic resin composition. On the other hand, an average fiber length below the upper limit reduces the likelihood of glass fibers protruding from the pellets when the resulting thermoplastic resin composition is pelletized. This reduces the likelihood of a decrease in the bulk density of the pellets.

[0047] The average fiber length of glass fibers can be measured, for example, using the following method. First, for example, 100 or more glass fibers are arbitrarily selected, and their total mass is measured. Next, the fiber length of each glass fiber is measured by observing the glass fibers with an optical microscope or scanning electron microscope, and the sum of these lengths is divided by the total mass of the glass fibers to obtain the weight-average fiber length.

[0048] The average fiber diameter of the glass fibers is 3 μm to 9 μm, preferably 4 μm to 8 μm, and more preferably 5 μm to 7 μm. In other words, it is preferable that the raw material glass fibers be very fine. When the average fiber diameter is above the lower limit, the strength of the glass fibers is sufficiently high, and the reinforcing effect is more fully exhibited. When the average fiber diameter is below the upper limit, 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 fully exhibited.

[0049] The average fiber diameter of glass fibers can be measured, for example, using the following method. First, for example, 100 or more glass fibers are arbitrarily selected. Next, the fiber diameter of each glass fiber is measured by observing them with an optical microscope or scanning electron microscope, and the sum of these values ​​can be divided by 100 to obtain the number-average fiber diameter.

[0050] The glass fibers commonly used are called "E-glass" and contain approximately 7% by mass of boron oxide relative to the total mass of the glass fibers. In this embodiment, it is preferable that the glass fibers included in the thermoplastic resin composition are substantially free of boron oxide. That is, it is preferable that the resulting thermoplastic resin composition is substantially free of boron oxide. By substantially omitting boron oxide, the physical properties of the composition, particularly its vibration fatigue resistance, are improved.

[0051] In this context, "substantially boron-free" means that the composition contains no boron oxide at all, or only trace amounts that do not impair the properties of the resulting thermoplastic resin composition (particularly vibration fatigue resistance). Specifically, the boron oxide content is preferably less than 5% by mass, more preferably less than 1% by mass, even more preferably less than 0.1% by mass, and particularly preferably 0% by mass, based on the total mass of the thermoplastic resin composition.

[0052] (copper compound) In the melt-mixing process, copper compounds can be added in addition to thermoplastic resins and glass fibers. Examples of copper compounds include inorganic 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 copper salts such as copper acetate, copper propionate, copper benzoate, copper adipate, copper terephthalate, copper isophthalate, and copper stearate. Alternatively, copper complex salts coordinated with a chelating agent can be used. Among these, cuprous iodide is preferred. These copper compounds may be used individually or in combination of two or more.

[0053] The amount of copper compound blended is preferably 0.0001 parts by mass or more and 1 part by mass or less per 100 parts by mass of thermoplastic resin, more preferably 0.005 parts by mass or more and 0.2 parts by mass or less, and even more preferably 0.02 parts by mass or more and 0.1 parts by mass or less.

[0054] (Metal halides) In the melt-mixing process, metal halides can be added in addition to thermoplastic resins and glass fibers. Potassium halides are preferred as metal halides. Examples of potassium halides include potassium iodide, potassium bromide, and potassium chloride. Among these, potassium iodide is preferred. These potassium halides may be used individually or in combination of two or more.

[0055] The amount of metal halide added is preferably 0.0001 parts by mass or more and 1 part by mass or less, more preferably 0.005 parts by mass or more and 0.2 parts by mass or less, and even more preferably 0.02 parts by mass or more and 0.15 parts by mass or less, per 100 parts by mass of thermoplastic resin.

[0056] (Other resin components) In the manufacturing method of this embodiment, as the raw material resin, in addition to thermoplastic resins with viscosity numbers within the above range, other thermoplastic resins with viscosity numbers outside the above range can be used, as long as the properties of the resulting thermoplastic resin composition are not impaired.

[0057] Other thermoplastic resins with viscosity numbers outside the above range include, for example, 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; and polycarbonate, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, and polyphenylene sulfide. These other thermoplastic resins are preferably modified with a modifier such as maleic anhydride or a glycidyl group-containing monomer before use. Among these, resins without functional groups, such as polyethylene, polypropylene, or ethylene-propylene copolymer, are preferably modified before use.

[0058] [Heating process] In the heating step, the molten mixture is heated to a temperature T represented by the following general formula (I), and the thermoplastic resin in the molten mixture is increased in molecular weight by solid-phase polymerization to obtain a thermoplastic resin composition. Tm-130℃≦T≦Tm-10℃ (I) (In the formula, Tm is the melting point of the thermoplastic resin.)

[0059] The molten mixture obtained in the molten mixing process may be introduced directly from the extruder into a solid-phase polymerization reactor for solid-phase polymerization, or it may be packaged in a paper bag or the like for storage before being added to the solid-phase polymerization reactor for solid-phase polymerization.

[0060] By setting the temperature T to be above the melting point of the thermoplastic resin (-130°C), the polymerization reaction can be accelerated, allowing for efficient polymerization and enabling the desired degree of polymerization to be achieved. By keeping the temperature T below the melting point of the thermoplastic resin (-10°C), the thermoplastic resin becomes less susceptible to thermal decomposition, thereby suppressing discoloration degradation on the polymer surface. Furthermore, the fusion of solid prepolymers can be further inhibited.

[0061] The melting point Tm of thermoplastic resins can be measured in accordance with JIS-K7121. For example, a Diamond DSC from PERKIN-ELMER can be used as the measuring device. Specifically, it can be measured using the method shown in the examples described later.

[0062] In the heating process, the heating time of the molten mixture is preferably 30 minutes to 15 hours within the above temperature range. A heating time above the lower limit allows the thermoplastic resin composition to reach the desired viscosity (degree of polymerization of the thermoplastic resin) more efficiently. A heating time below the upper limit more effectively suppresses the fusion of lower-order condensates and discoloration (yellowing) of the composition during solid-phase polymerization.

[0063] Solid-phase polymerization can be carried out in either a continuous or batch manner. The solid-phase polymerization reactor may be vertical or horizontal. Stirring is preferable to enhance the uniformity of the solid-phase polymerization reaction. The polymerization reactor may be a rotating type or a stirring type using impellers or the like. In particular, it is preferable to carry out the solid-phase polymerization reaction in the heating step continuously.

[0064] Furthermore, in the solid-phase polymerization reaction during the heating process, it is preferable to use a molten mixture in which condensation water has been generated. The amount of condensation water is, for example, 2 g or more per 1 kg of molten mixture, preferably 2 g to 15 g, and more preferably 2 g to 10 g.

[0065] The solid-phase polymerization reaction in the heating process can be carried out under either a vacuum or a gas stream, but it is preferable to carry it out under a gas stream of an inert gas such as nitrogen gas.

[0066] When solid-phase polymerization is carried out under an inert gas stream, it is preferable to carry it out in an inert gas atmosphere with an oxygen concentration of 5 ppm or less. By keeping the oxygen concentration below the above upper limit, the resulting thermoplastic resin composition is less susceptible to oxidative degradation. This reduces the likelihood of reactions that cleave molecular chains, prevents a decrease in the rate at which molecular weight increases (polymerization reaction rate), and makes it easier to obtain a thermoplastic resin composition with a predetermined molecular weight. Furthermore, it is possible to more effectively suppress the deterioration of the mechanical properties and yellowing of the resulting thermoplastic resin.

[0067] When solid-phase polymerization is carried out under an inert gas stream, it is preferable to carry it out in an inert gas atmosphere with a moisture concentration of 10 ppm or less. A moisture concentration below the above upper limit makes the thermoplastic resin less susceptible to hydrolysis. This prevents a decrease in the rate at which the molecular weight increases (polymerization reaction rate), making it easier to obtain a thermoplastic resin composition with a predetermined molecular weight.

[0068] When solid-phase polymerization is carried out under an inert gas stream, it is preferable to form a particle layer with the molten mixture and carry out the solid-phase reaction while supplying a predetermined amount of inert gas to a predetermined position at a specific height of the particle layer. Specifically, at a height of 0 to 0.8 times, preferably 0 to 0.5 times, the height of the particle layer, an inert gas is introduced at a rate of 0.1 Nm³ per 1 kg of molten compound. 3 / hour over 10Nm 3 Less than or equal to / hour, preferably 0.14 Nm 3 / hour over 10Nm 3 It is preferable to carry out the solid-phase polymerization reaction while supplying an amount of less than / hour.

[0069] The height h of the particle layer is defined as follows: The solid-phase polymerization reactor is opened, and at room temperature and atmospheric pressure, an amount of molten compound particles or pellets equivalent to the operating volume is charged in. With a predetermined amount of inert gas flowing through, the height of the particle layer is measured with the bottom of the reactor where the gas supply port is located as the reference point (h=0), and this height is defined as h. If the height plane of the particle layer is not constant, h is defined as the average value of the highest and lowest heights.

[0070] <Thermoplastic resin composition> The thermoplastic resin composition obtained by the manufacturing method of this embodiment preferably has a viscosity number VN of 200 to 350, more preferably 210 to 330, and even more preferably 220 to 300. When VN is above the lower limit, the abrasion resistance is better, while when VN is below the upper limit, the moldability is better when molded for each application.

[0071] The glass fiber content in the thermoplastic resin composition is preferably 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of thermoplastic resin. A glass fiber content above the lower limit allows for greater rigidity and strength of the thermoplastic resin composition, while a content below the upper limit improves moldability when the thermoplastic resin composition is molded for various applications.

[0072] The average fiber length of the glass fibers contained in the thermoplastic resin composition is preferably between 100 μm and 1000 μm. An average fiber length above the lower limit allows for a more sufficient reinforcing effect, further improving impact strength and tensile strength. On the other hand, an average fiber length above the lower limit also reduces the likelihood of glass fibers protruding from the pellets when the thermoplastic resin composition is pelletized. This helps to prevent a decrease in the bulk density of the pellets.

[0073] The average fiber length of glass fibers contained in a 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, from the obtained insoluble components, for example, 100 or more glass fibers are arbitrarily selected, and the total mass of these glass fibers is measured. Then, the fiber length of each glass fiber is measured by observing the glass fibers with an optical microscope or scanning electron microscope, and the weight-average fiber length can be obtained by dividing the sum of these lengths by the total mass of the glass fibers.

[0074] The thermoplastic resin composition obtained by the manufacturing method of this embodiment exhibits excellent vibration fatigue resistance and is therefore suitable for use in applications such as automobile parts, electronic and electrical components, industrial machinery parts, and various gears. [Examples]

[0075] The embodiment will be described in detail below with reference to specific examples and comparative examples, but this embodiment is not limited in any way to the following examples and comparative examples. Various physical properties were measured using the methods described below. Furthermore, various evaluations were conducted using the methods described below.

[0076] <Method for measuring physical properties> [Physical Properties 1] (viscosity number VN) The viscosity number VN was measured using pellets of polyamide resin and polyamide resin composition in accordance with ISO 307 (JIS-K6933). Specifically, the measurement was performed on a solution containing 0.5% by mass of polyamide resin or polyamide resin composition in 96% by mass sulfuric acid at 25°C. When the polyamide resin composition contained reinforcing materials such as glass fibers, the ash content in the polyamide resin composition was measured in advance, for example, according to the provisions of ISO 3451-4, and the polyamide resin content was calculated from the polyamide resin composition by using the polyamide resin content obtained by subtracting the ash content.

[0077] [Physical Properties 2] (Moisture percentage) The moisture content (mass%) of the polyamide resin composition pellets produced in the examples and comparative examples was measured using a Karl Fischer moisture meter (Mitsubishi Chemical Analytec Co., Ltd., coulometric titration type trace moisture analyzer CA-200) in accordance with ISO 15512.

[0078] [Physical Properties 3] (Melting point) The heat of fusion was measured using a Diamond-DSC manufactured by PERKIN-ELMER in accordance with JIS-K7121 (hereinafter also referred to as "DSC measurement"). The DSC measurement was performed under a nitrogen atmosphere. Approximately 10 mg of pellets of the polyamide resin composition produced in the examples and comparative examples were used as samples. Specifically, in the DSC measurement, first, the sample was heated from 25°C to the melting point of the polyamide resin + approximately 30°C (for example, 294°C for PA66) at a heating rate of 20°C / min. Next, the polyamide resin was completely melted by holding it at the highest temperature from the first heating for 3 minutes. After that, the sample was cooled down to 25°C at a cooling rate of 20°C / min and held at 25°C for 3 minutes. Then, the melting point of the polyamide resin composition was determined from the endothermic peak (melting peak) that appeared when the sample was heated again at a heating rate of 20°C / min.

[0079] [Physical Properties 4] (Molar ratio of carboxyl-terminal groups to amino-terminal groups) For the polyamide resin compositions produced in the examples and comparative examples, the amount of carboxy-terminal groups [COOH] and amino-terminal groups [NH2] were respectively 1 The amount of end groups present in 1 kg of polyamide resin was calculated by 1H-NMR (sulfuric acid-d2 solvent). The specific procedure is as follows. For carboxyl group termini, the integral value of the 2.724 ppm peak (a') was calculated for the hydrogen atoms of the methylene group (-CH2-) adjacent to the terminal COOH group. For the amino group terminus, the integral value of the peak (b') around 2.884 ppm was calculated for the hydrogen of the methylene group (-CH2-) adjacent to the terminal NH2. For dicarboxylic acid units in the polyamide main chain, the hydrogen atoms of the methylene group (-CH2-) adjacent to the amide group were calculated using the integral value of the 2.451 ppm peak (a). For diamine units in the polyamide main chain, the hydrogen atoms of the methylene group (-CH2-) adjacent to the amide group were calculated using the integral value of the 3.254 ppm peak (b).

[0080] Using the integrated values ​​of the peaks mentioned above, the amount of carboxy-terminal group [COOH] and the amount of amino-terminal group [NH2] were calculated using the following formulas.

[0081] Carboxyterminant group content [COOH] (mmolEq / kg) =(a' / 2) / [{(b+b')×114.2 / 4}+{(a+a')×112.1 / 4}] Amino-terminal group content [NH2] (mmolEq / kg) =(b' / 2) / [{(b+b')×114.2 / 4}+{(a+a')×112.1 / 4}]

[0082] From the obtained amounts of carboxy-terminal groups [COOH] and amino-terminal groups [NH2], the molar ratio of carboxy-terminal groups to amino-terminal groups [COOH] / [NH2] was determined.

[0083] [Physical Properties 5] (Pellet diameter) The obtained 100 pellets were measured using electronic calipers, and the average value was defined as the pellet diameter. For round pellets, the pellet diameter (or the point of maximum diameter in the case of a spherical approximation) was measured; for elliptical pellets, the semi-major axis of the pellet (or the point of maximum semi-major axis in the case of an ellipsoidal approximation) was measured; and for cylindrical pellets, the maximum height was measured.

[0084] <Evaluation Method> [Preparation of test specimens] Small tensile test specimens (Type CP13) (3 mm thick) were manufactured from the polyamide resin composition pellets produced in the Examples and Comparative Examples using an injection molding machine in accordance with JIS-K7139, as described below. A PS40E injection molding machine manufactured by Nissei Plastic Industrial Co., Ltd. was used, and a mold for two of the above-mentioned small tensile test specimens was attached. The cylinder temperature was set to the melting point of the polyamide resin + approximately 15°C (for example, 280°C for PA66), and the mold temperature was set to 80°C. Furthermore, dumbbell-shaped small tensile test specimens were obtained from the polyamide resin composition pellets under injection molding conditions of 10 seconds of injection, 7 seconds of cooling, and a plasticization amount of 30 mm (cushion amount of approximately 10 mm).

[0085] [Rating 1] (Tensile strength) The tensile strength of the obtained small tensile test specimens (Type CP13) (3 mm thick) was measured in a dry state. The tensile strength of the dumbbell was measured under the conditions of a chuck distance of 30 mm and a tensile speed of 5 mm / min.

[0086] [Rating 2] (Vibration fatigue resistance) For the obtained small tensile test specimens (Type CP13) (3 mm thick), the number of vibrations (cycles) at which the specimen fractured was determined using a hydraulic servo fatigue testing machine (product name: EHF-50-10-3, manufactured by Sagimiya Seisakusho Co., Ltd.) in accordance with JIS K7118, under the conditions of a temperature of 120°C, a frequency of 20 Hz sine wave, and a tensile load of 60 MPa. The evaluation criteria include a higher number of vibrations before fracture (15 x 10 5 (If the number of vibrations was 2 or more) it was evaluated as having excellent vibration fatigue resistance.

[0087] [Rating 3] (Wear depth) The obtained small tensile test piece (Type CP13) (3 mm thick) was used in a reciprocating friction and wear test machine (AFT-15MS type manufactured by Toyo Precision Co., Ltd.), and a SUS304 test piece (a 5 mm diameter sphere) as the counter material. A sliding test was carried out at a linear velocity of 30 mm / sec, a reciprocating distance of 20 mm, a temperature of 23°C, a humidity of 50%, a load of 1.5 kg, and a reciprocating number of 5,000 times to obtain the friction coefficient. The wear depth at the center of the wear scar of the sample after the sliding test was measured with a surface roughness meter (575A-30 manufactured by Toyo Precision Co., Ltd.). In Table 1, the respective results are shown as "friction coefficient (23°C)" and "wear depth (23°C)".

[0088] [Evaluation 4] (Glass fiber (GF) dropout rate) 25 kg of the pellets of the polyamide resin composition produced in the examples and comparative examples were sieved by passing through a plain woven wire mesh (18 mesh, wire diameter 0.4 mm, mesh opening 1.01 mm, aperture ratio 51.3%) to obtain the material passing through the wire mesh. The polyamide resin was removed by burning the material passing through the wire mesh at 650°C for 2 hours, and the weight was measured to obtain the amount of dropped GF in 25 kg of the pellets. Using the obtained value, the GF dropout rate was calculated from the following formula. GF dropout rate (wt%) = (amount of dropped GF in 25 kg of pellets) / (25 kg × (GF charged amount / total amount of polyamide resin composition)) × 100 ​​​​​​​​​​​​​​​灰分 ) × 100 Here, σ 灰分 μ is the standard deviation of ash content. 灰分 This represents the arithmetic mean of the ash content.

[0090] [Productivity Evaluation: Noise Assessment during Solid-Phase Polymerization] During the solid-phase polymerization operation, ten people confirmed the occurrence of squeaking and abnormal noises, and evaluated them as follows. If the number of people who detect a noise or unusual sound is 0: ○ If the number of people who detect a noise or unusual sound is between 1 and 2: △ If three or more people detect that a noise or abnormal sound has occurred: ×

[0091] <Raw materials> 1. (A) Component: Manufacturing of polyamide resin [Manufacturing Example 1] (Production of polyamide resin A1: polyamide 66) 15,000 g of an equimolar salt of adipic acid and hexamethylenediamine, and 0.5 mol% excess adipic acid relative to the equimolar salt component, were dissolved in 15,000 g of distilled water to obtain a 50% by mass aqueous solution of the raw material monomer. The obtained aqueous solution was placed in a 40 L autoclave, and the autoclave was purged with nitrogen. This aqueous solution was concentrated by gradually removing water vapor while stirring at a temperature of 110°C to 150°C until the solution concentration reached 70% by mass. Then, the internal temperature was raised to 220°C. At this time, the autoclave was pressurized to 1.8 MPa. The reaction was continued for 1 hour while gradually removing water vapor and maintaining the pressure at 1.8 MPa until the internal temperature reached 270°C. Then, the pressure was reduced to atmospheric pressure over approximately 1 hour. After reaching atmospheric pressure, the solution was discharged in strand form from the lower nozzle, water-cooled, and cut to obtain pellets of polyamide resin A1. The resulting pellets were dried in a nitrogen atmosphere at 90°C for 4 hours. The viscosity number VN of these pellets was 133, and the melting point was 265°C.

[0092] [Manufacturing Example 2] (Production of polyamide resin A2: polyamide 66) Polyamide resin A2 pellets were produced using the same method as in Production Example 1, except that the inside of the tank was maintained under reduced pressure of 100 torr (1.33 × 10⁴ Pa) for 10 minutes using a vacuum device before discharge from the lower nozzle. The viscosity number VN of these pellets was 188 and the melting point was 264°C.

[0093] 2. (B) Component: Manufacturing of fibrous reinforcing material [Manufacturing Example 3] (Manufacturing of fibrous reinforcing material B1) First, (x-1) to (x-4), described below, were diluted with water in the following proportions as solids: 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 scrubber. The obtained glass fiber sizing agent was attached to glass fibers (containing boron oxide) with a number-average fiber diameter of 7 μm. The attachment method involved using an applicator installed while the melt-proofed glass fibers were being wound onto a rotating drum to attach the sizing agent to the glass fibers. Subsequently, the glass fibers to which the sizing agent had been attached were dried to obtain roving of glass fiber bundles surface-treated with the glass fiber sizing agent. At this time, the glass fibers were bundled in units of 1,000. The amount of glass fiber sizing agent attached to the glass fibers was 0.6% by mass. The obtained roving was cut to a length of 3 mm to obtain fibrous reinforcement material B1 (chopped strand, hereinafter simply abbreviated as "(B1)").

[0094] The components (x-1) to (x-4) that make up the sizing agent used in the preparation of the fibrous reinforcing material are as follows: (x-1) Polyurethane resin emulsion Product name: Bondic (registered trademark) 1050 (manufactured by Dainippon Ink Co., Ltd.) (Aqueous solution with 50% solid content by mass) (x-2) Maleic anhydride-based copolymer emulsion Product Name: Acrobinder (Registered Trademark) BG-7 (Manufactured by Sanyo Chemical Industries, Ltd.) (Aqueous solution with 25% solid content by mass) (x-3) Aminosilane coupling agent Product name: KBE-903 (manufactured by Shin-Etsu Chemical Co., Ltd.) γ-aminopropyltriethoxysilane (x-4) Lubricant Product name: Carnauba wax (manufactured by Kato Yoko Co., Ltd.)

[0095] [Manufacturing Example 4] (Manufacturing of fibrous reinforcing material B2) Fibrous reinforcing material B2 (chopped strand, hereinafter simply abbreviated as "(B2)") was obtained using the same method as in Production Example 3 above, except that glass fibers with a number average fiber diameter of 5 μm (containing boron oxide) were used instead of glass fibers with a number average fiber diameter of 7 μm (containing boron oxide). The amount of glass fiber sizing agent adhering to the glass fibers was 0.7% by mass.

[0096] [Manufacturing Example 5] (Manufacturing of fibrous reinforcing material B3) Fibrous reinforcing material B3 (chopped strand, hereinafter simply abbreviated as "(B3)") was obtained using the same method as in Production Example 3 above, except that glass fibers with a number average fiber diameter of 7 μm (containing boron oxide) were used instead of glass fibers with a number average fiber diameter of 7 μm (boron oxide-free). The amount of glass fiber sizing agent adhering to the glass fibers was 0.6% by mass.

[0097] [Manufacturing Example 6] (Manufacturing of fibrous reinforcing material B4) A fibrous reinforcing material (B4) (chopped strand, hereinafter simply abbreviated as "(B4)") was obtained in the same manner as in Production Example 3, except that glass fibers with a number-average fiber diameter of 10 μm (containing boron oxide) were used instead of glass fibers with a number-average fiber diameter of 7 μm (containing boron oxide). The amount of glass fiber sizing agent adhering to the glass fibers was 0.5% by mass.

[0098] 3. Other raw materials In addition to the raw materials manufactured above, the following raw materials were also 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.

[0099] <Manufacturing of polyamide resin compositions> [Example 1] (Manufacturing of polyamide resin composition PA-a1) (1) Melt-mixing process Using a twin-screw extruder with a screw diameter of 26 mm (manufactured by Coperion Co., Ltd., product name "ZSK26MC"), a mixture of polyamide resin A1 obtained in Production Example 1, impregnated with a copper compound and a halide, was supplied as the top feed according to the compound composition shown in Table 1, and fibrous reinforcing material B1 obtained in Production Example 3 was supplied as the side feed. 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 25 kg / h, and pellets were obtained by the underwater cut method. The obtained pellets had a VN of 134, an ellipsoidal shape, and a pellet diameter of 3.5 mm.

[0100] (2)Heating process (solid phase polymerization) 10 kg of pellets obtained in "(1) Melt-mixing process" were placed in a conical ribbon vacuum dryer (manufactured by Okawara Seisakusho Co., Ltd., product name Ribocone RM-10V) and thoroughly purged with nitrogen (oxygen concentration 4.2 ppm, moisture concentration 8.7 ppm). With nitrogen flowing at 2 L / min and stirring, the pellets were heated at a temperature of 190°C for 6 hours. After that, the temperature was lowered while nitrogen flowing was still present, and when it reached approximately 50°C, the pellets were removed from the apparatus to obtain pellets of polyamide resin composition PA-a1. The VN of the obtained pellets was 230.

[0101] [Example 2] (Manufacturing of polyamide resin composition PA-a2) (1) Melt-mixing process Melt-kneading was carried out in the same manner as in Example 1, except that polyamide resin A2 obtained in Production Example 2 was used instead of polyamide resin A1 obtained in Production Example 1, and the extrusion conditions were set to a temperature of 310°C, a screw rotation speed of 250 rpm, and a discharge rate of 20 kg / h, to obtain pellets (molten kneaded material). The obtained pellets had a VN of 180, an ellipsoidal shape, and a pellet diameter of 3.5 mm.

[0102] (2)Heating process (solid phase polymerization) Solid-phase polymerization was carried out in the same manner as in Example 1, except that the pellet temperature was heated at 190°C for 3 hours, to obtain pellets of polyamide resin composition PA-a2. The VN of the obtained pellets was 234.

[0103] [Example 3] (Manufacturing of polyamide resin composition PA-a3) Solid-phase polymerization was carried out in the same manner as in Example 1, except that the pellets (molten mixture) obtained in "(1) Melt-kneading step" of Example 1 were heated at a pellet temperature of 210°C for 9 hours, to obtain pellets of polyamide resin composition PA-a3. The VN of the obtained pellets was 300.

[0104] [Example 4] (Manufacturing of polyamide resin composition PA-a4) Except for adjusting the amount of fibrous reinforcing material B1 to the amount shown in Table 1, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1 to obtain pellets of polyamide resin composition PA-a4. The VN of the obtained pellets was 228.

[0105] [Example 5] (Manufacturing of polyamide resin composition PA-a5) Except for increasing the amount of fibrous reinforcing material B1 to the amount shown in Table 1, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1 to obtain pellets of polyamide resin composition PA-a5. The VN of the obtained pellets was 238.

[0106] [Example 6] (Manufacturing of polyamide resin composition PA-a6) Except for using fibrous reinforcing material B2 instead of fibrous reinforcing material B1, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1 to obtain pellets of polyamide resin composition PA-a6. The VN of the obtained pellets was 236.

[0107] [Example 7] (Manufacturing of polyamide resin composition PA-a7) Except for using fibrous reinforcing material B3 instead of fibrous reinforcing material B1, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1 to obtain pellets of polyamide resin composition PA-a6. The VN of the obtained pellets was 230.

[0108] [Comparative Example 1] (Manufacturing of polyamide resin composition PA-b1) (1)Heating process (solid phase polymerization) 10 kg of polyamide resin A1 obtained in Production Example 1 was placed in a conical ribbon vacuum dryer (manufactured by Okawara Seisakusho Co., Ltd., product name Ribocone RM-10V) and thoroughly purged with nitrogen (oxygen concentration 4.2 ppm, moisture concentration 8.7 ppm). While flowing nitrogen at 2 L / min and stirring, the pellet was heated at a pellet temperature of 210°C for 8 hours. After that, the temperature was lowered while continuing to flow nitrogen, and when it reached approximately 50°C, the pellet was removed from the apparatus. The VN of the obtained pellet was 286.

[0109] (2) Melt-mixing process Using the pellets obtained in "(1) Heating step (solid-phase polymerization)", melt kneading was carried out under the same conditions as in "(1) Melt kneading step" of Example 1, according to the blending composition shown in Table 1, to obtain pellets of polyamide resin composition PA-b1. The obtained pellets had a VN of 235, an ellipsoidal shape, and a pellet diameter of 3.5 mm.

[0110] [Comparative Example 2] (Manufacturing of polyamide resin composition PA-b2) Except for using fibrous reinforcing material B4 instead of fibrous reinforcing material B1, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1 to obtain pellets of polyamide resin composition PA-b2. The VN of the obtained pellets was 231.

[0111] [Comparative Example 3] (Manufacturing of polyamide resin composition PA-b3) Except for reducing the amount of fibrous reinforcing material B1 to the amount shown in Table 2, melt kneading and solid-phase polymerization were carried out in the same manner as in Example 1 to obtain pellets of polyamide resin composition PA-b3. The VN of the obtained pellets was 225.

[0112] [Comparative Example 4] (Manufacturing of polyamide resin composition PA-b4) Except for increasing the amount of fibrous reinforcing material B1 to the amount shown in Table 2, melt kneading was carried out in the same manner as in Example 1, but the cutting performance using the underwater cut method was poor and pellets could not be obtained. Therefore, the subsequent heating step (solid-phase polymerization) was not carried out.

[0113] [Comparative Example 5] (Manufacturing of polyamide resin composition PA-b5) (1) Melt-mixing process Using a twin-screw extruder with a screw diameter of 26 mm (manufactured by Coperion Co., Ltd., product name "ZSK26MC"), a mixture of polyamide resin A1 obtained in Production Example 1, impregnated with a copper compound and a halide, was supplied as the top feed according to the compound composition shown in Table 1, and fibrous reinforcing material B1 obtained in Production Example 3 was supplied as the side feed. 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 25 kg / h, and pellets were obtained by the strand-cut method. The obtained pellets had a VN of 135, a cylindrical shape, and a pellet diameter of 3.5 mm.

[0114] (2)Heating process (solid phase polymerization) 10 kg of pellets obtained in "(1) Melt-mixing process" were placed in a conical ribbon vacuum dryer (manufactured by Okawara Seisakusho Co., Ltd., product name Ribocone RM-10V) and thoroughly purged with nitrogen (oxygen concentration 4.2 ppm, moisture concentration 8.7 ppm). With nitrogen flowing at 2 L / min and stirring, the pellets were heated at a temperature of 190°C for 6 hours. After that, the temperature was lowered while nitrogen flowing was still present, and when it reached approximately 50°C, the pellets were removed from the apparatus to obtain pellets of polyamide resin composition PA-a1. The VN of the obtained pellets was 227.

[0115] Various evaluations were performed using the polyamide resin compositions obtained in the examples and comparative examples by the method described above. The results are shown in Tables 1 and 2. Note that comparative example 4 was not evaluated because no pellets of the polyamide resin composition were obtained.

[0116] [Table 1]

[0117] [Table 2]

[0118] Tables 1 and 2 show that all evaluation items were favorable for polyamide resin compositions PA-a1 to PA-a7 (Examples 1 to 7).

[0119] (B) In polyamide resin compositions PA-a1, PA-a4, and PA-a5 (Examples 1, 4, and 5) with different amounts of fibrous reinforcing material, there was a tendency for tensile strength and vibration fatigue resistance to improve as the amount of fibrous reinforcing material increased.

[0120] In polyamide resin compositions PA-a1 and PA-a3 (Examples 1 and 3), which differed in heating temperature and time, a tendency was observed for tensile strength to improve as the heating temperature decreased and the heating time shortened. Furthermore, a tendency was observed for vibration fatigue resistance to improve as the heating temperature increased and the heating time lengthened.

[0121] (B) In polyamide resin compositions PA-a1 and PA-a6 (Examples 1 and 6) with different average fiber diameters of glass fibers contained in the fibrous reinforcing material, a tendency was observed for tensile strength, vibration fatigue resistance, and abrasion resistance to improve as the average fiber diameter decreased. (B) In polyamide resin compositions PA-A and PA-a7 (Examples 1 and 7) which differ in the type of glass fiber contained in the fibrous reinforcing material, it was observed that using glass fibers that did not contain boron oxide tended to result in better vibration fatigue resistance and abrasion resistance.

[0122] On the other hand, the polyamide resin composition PA-b1 (Comparative Example 1), obtained by following the heating and melt-kneading processes in that order, exhibited poor tensile strength, vibration fatigue resistance, abrasion resistance, and filler shedding properties. Furthermore, the polyamide resin composition PA-b2 (Comparative Example 2) obtained using (B) fibrous reinforcing material containing glass fibers with an average fiber diameter of 10 μm, which is greater than 9 μm, exhibited poor tensile strength, vibration fatigue resistance, and abrasion resistance.

[0123] (B) In the polyamide resin composition PA-b3 (Comparative Example 3), in which the amount of fibrous reinforcing material was 4 parts by mass (less than 5 parts by mass), both tensile strength and vibration fatigue resistance were poor. (B) When 150 parts by mass of fibrous reinforcing material was added (Comparative Example 4), the cutability by the underwater cut method was poor, and it was not possible to obtain a molten kneaded product. In the polyamide resin composition PA-b5 (Comparative Example 5), where the pellets obtained in the melt-mixing process were cylindrical, vibration fatigue resistance, wear resistance, filler shedding properties, and productivity were all poor. [Industrial applicability]

[0124] According to the manufacturing method of this embodiment, a thermoplastic resin composition with excellent vibration fatigue resistance can be obtained. The thermoplastic resin composition obtained by the manufacturing method of this embodiment can be suitably used in, for example, automobile parts, electronic and electrical components, industrial machine parts, various gears, and the like.

Claims

1. A melt-kneading step is performed to obtain a melt-kneaded product by adding 5 to 100 parts by mass of glass fibers having an average fiber diameter of 3 μm to 9 μm to 100 parts by mass of a thermoplastic resin having a viscosity number VN of 80 or more and 200 or less, and melt-kneading the mixture. The heating step includes heating the molten mixture at a temperature T represented by the following general formula (I) for 30 minutes to 15 hours under vacuum or inert gas flow to obtain a thermoplastic resin composition, A method for producing a thermoplastic resin composition, wherein the thermoplastic resin composition obtained in the melt-kneading step is in the form of round pellets or elliptical pellets. Tm-130℃≦T≦Tm-10℃ (I) (In the formula, Tm is the melting point of the thermoplastic resin.)

2. The method for producing the thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has a viscosity number VN of 200 or more and 350 or less.

3. A method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the average fiber length of the glass fibers is 100 μm or more and 1000 μm or less.

4. A method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the average fiber diameter of the glass fibers is 4 μm or more and 8 μm or less.

5. A method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the heating step is performed in an inert gas atmosphere with an oxygen concentration of 5 ppm or less.

6. A method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the heating step is performed in an inert gas atmosphere with a moisture concentration of 10 ppm or less.

7. A method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the thermoplastic resin is a polyamide or polyester.

8. A method for producing a thermoplastic resin composition according to claim 7, wherein the polyamide is polyamide 6, polyamide 66, or polyamide 610.

9. A method for producing a thermoplastic resin composition according to claim 7, wherein the value obtained by dividing the amount of amino-terminal groups of the polyamide by the amount of carboxy-terminal groups is 0.5 or more and 0.9 or less.

10. A method for producing the thermoplastic resin composition according to claim 1 or 2, wherein the thermoplastic resin composition substantially does not contain boron oxide.

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