Polyamide resin composition

Abstract

[Problem] To provide a polyamide resin composition hardly affected by variations in manufacturing conditions and capable of stably providing a molded article having high rigidity and a favorable appearance. [Solution] A polyamide resin composition which contains 0-3 parts by mass hypophosphite metal salt (D) with respect to a total of 100 parts by mass constituted by 20-60 parts by mass aliphatic polyamide resin (A), 5-20 parts by mass polyamide MXD6 resin (B), and 30-59 parts by mass inorganic hardening material (C), and which is characterized in that the MFR of a 2.16 kg load of the polyamide resin composition measured at 275°C is 3-60 g / 10 min.

Description

Technical Field

[0001] The present invention relates to a polyamide resin composition, and more particularly to a polyamide resin composition that contains a reinforcing fiber in a high filling amount and can provide a molded product having high strength, high rigidity, and excellent appearance.

Background Art

[0002] Generally, aliphatic polyamide resins typified by polyamide 6 and polyamide 66 are excellent in mechanical strength, heat resistance, impact resistance, and chemical resistance, and are widely used in automotive parts, electrical parts, electronic parts, and household goods. Among them, fiber-reinforced polyamide resin compositions added with inorganic reinforcing materials typified by glass fiber are known to significantly improve rigidity, strength, heat resistance, etc., and a large amount of reinforcing materials such as glass fiber is added (Patent Documents 1, 2, etc.). However, when a large amount of a reinforcing material such as glass fiber is added, the appearance of the molded product is extremely deteriorated, and the commercial value is often significantly impaired. In Patent Documents 1 and 2, it is proposed to use a low-viscosity polyamide resin, but the appearance of the molded product was not satisfactory. Therefore, in Patent Document 3, a method of using an amorphous semi-aromatic polyamide resin and a specific elastomer in combination in addition to an aliphatic polyamide resin is proposed to improve the appearance of the molded product (Patent Document 3). In this method, although the appearance is improved, there are drawbacks such as a decrease in the rigidity and heat resistance of the molded product, and it is easily affected by fluctuations in manufacturing conditions, and there are difficulties in manufacturing stability, and it is difficult to obtain stable molded product characteristics.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

[0004] The present invention aims to solve the above-mentioned problems and to provide a polyamide resin composition that is less susceptible to fluctuations in manufacturing conditions, has a high reinforcing fiber content, and can stably provide molded products with high strength, high rigidity, good appearance, and excellent high-temperature rigidity.

[0005] The inventors of the present invention have investigated the cause of the inability to consistently obtain molded products with a good appearance when mixing different types of polyamide resins, such as amorphous polyamide resins, with crystalline aliphatic polyamide resins in order to improve appearance. As a result, they found that the cause is that the rate of progress of the amide exchange reaction between polyamides is easily affected by fluctuations in manufacturing conditions. Therefore, they conceived that if the amide exchange reaction could be advanced to reach a metastable polymer state early, the product would be less susceptible to fluctuations in manufacturing conditions, leading to the present invention. [Means for solving the problem]

[0006] In other words, the present invention is as follows. (1) A polyamide resin composition comprising 20 to 60 parts by mass of aliphatic polyamide resin (A), 5 to 20 parts by mass of polyamide MXD6 resin (B), and 30 to 59 parts by mass of inorganic reinforcing material (C), totaling 100 parts by mass, and containing 0 to 3 parts by mass of a metal hypophosphite salt (D), A polyamide resin composition characterized in that the MFR measured under the conditions of a load of 2.16 kg and 275°C is 3 to 60 g / 10 min. (2) The polyamide resin composition according to (1), wherein the cooling crystallization temperature of the polyamide resin composition is 160 to 190°C. (3) The polyamide resin composition according to (1) or (2), which contains 0.001 to 3 parts by mass of the hypophosphate metal salt (D) with respect to 100 parts by mass of the total of (A), (B), and (C). (4) The polyamide resin composition according to any one of (1) to (3), characterized in that the inorganic reinforcing material (C) in the polyamide resin composition contains 40 to 59 parts by mass with respect to 100 parts by mass of the total of (A), (B), and (C). (5) The polyamide resin composition according to any one of (1) to (4), characterized in that the inorganic reinforcing material (C) is glass fiber. (6) The polyamide resin composition according to any one of (1) to (5), characterized in that the MFR measured under the conditions of a load of 2.16 kg and 275°C is 4 to 25 g / 10 min. [Effects of the Invention]

[0007] The polyamide resin composition of the present invention is less susceptible to fluctuations in manufacturing conditions and can stably provide molded articles with high strength, high rigidity, good appearance, and excellent high-temperature rigidity. [Modes for carrying out the invention]

[0008] The present invention will be described in detail below. In the present invention, the aliphatic polyamide resin (A) is preferably an aliphatic polyamide resin having an acid amide bond (-CONH-) in its molecule and having a crystalline melting point. Specifically, examples include polymers of polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polytetramethylene adipamide (polyamide 46), polyhexamethylene sevacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), poly-lauryl lactam (polyamide 12), poly-11-aminoundecanoic acid (polyamide 11), and copolymers and blends thereof, but are not limited to these. In the present invention, preferred aliphatic polyamide resins (A) include polyamide 6, polyamide 66, and mixtures of polyamide 6 and polyamide 66, with polyamide 6 being particularly preferred.

[0009] The relative viscosity of the aliphatic polyamide resin (A) (measured with 96% sulfuric acid and a polyamide resin concentration of 1 g / dl) is preferably in the range of 1.8 to 3.5, and more preferably in the range of 2.0 to 3.2.

[0010] The blending ratio of aliphatic polyamide resin (A) to 100 parts by mass of the total of aliphatic polyamide resin (A), polyamide MXD6 resin (B), and inorganic reinforcing material (C) is 20 to 60 parts by mass, preferably 25 to 50 parts by mass, and more preferably 28 to 42 parts by mass. The effects of the present invention are difficult to exhibit in the range of less than 20 parts by mass and more than 60 parts by mass. In the present invention, the blending ratio directly corresponds to the content ratio in the polyamide resin composition.

[0011] The polyamide MXD6 resin (B) in this invention is a polyamide resin mainly composed of polymetaxylylene adipamide, and is a polycondensate of a diamine component in which at least 80 mol% of the diamine component is metaxylylenediamine and a dicarboxylic acid component in which at least 80 mol% of the dicarboxylic acid component is adipic acid. As a diamine component other than metaxylylenediamine, paraxylylenediamine, tetramethylenediamine, hexamethylenediamine, etc. can be used as the diamine component other than metaxylylenediamine, provided that it is 20 mol% or less. As a dicarboxylic acid component other than adipic acid, aliphatic dicarboxylic acids such as sebacic acid can be used as the dicarboxylic acid component, provided that it is 20 mol% or less.

[0012] The relative viscosity of polyamide MXD6 resin (B) (measured in 96% sulfuric acid with a polyamide resin concentration of 1 g / dl) is preferably in the range of 1.5 to 4.0, and more preferably in the range of 1.8 to 3.0.

[0013] The blending ratio of polyamide MXD6 resin (B) to 100 parts by mass of the total of aliphatic polyamide resin (A), polyamide MXD6 resin (B), and inorganic reinforcing material (C) is 5 to 20 parts by mass, preferably 10 to 20 parts by mass, and more preferably 10 to 17 parts by mass. This content range results in excellent moldability, superior appearance of the molded product, and excellent heat resistance. The effects of the present invention are less pronounced in the ranges of less than 5 parts by mass and more than 20 parts by mass.

[0014] The blending ratio of aliphatic polyamide resin (A) and polyamide MXD6 resin (B) is preferably 10 to 90 parts by mass of polyamide MXD6 resin (B) per 100 parts by mass of aliphatic polyamide resin (A), more preferably 10 to 70 parts by mass, even more preferably 10 to 55 parts by mass, and most preferably 15 to 45 parts by mass. If the ratio is less than 10 parts by mass, it becomes difficult to control the crystallization temperature, and if it exceeds 90 parts by mass, the glass transition temperature becomes high, making it difficult to obtain a good appearance unless the mold temperature is increased.

[0015] The inorganic reinforcing material (C) in the present invention most effectively improves physical properties such as strength, rigidity, and heat resistance. Specifically, examples include fibrous materials such as glass fibers, carbon fibers, alumina fibers, silicon carbide fibers, and zirconia fibers; whiskers such as aluminum borate and potassium titanate; needle-shaped wollastonite; and milled fibers. In addition to these, fillers such as glass beads, glass flakes, glass balloons, silica, talc, kaolin, wollastonite, mica, alumina, hydrotalcite, montmorillonite, graphite, carbon nanotubes, fullerenes, zinc oxide, indium oxide, tin oxide, iron oxide, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, red phosphorus, calcium carbonate, potassium titanate, lead zirconate titanate, barium titanate, aluminum nitride, boron nitride, zinc borate, aluminum borate, barium sulfate, magnesium sulfate, and layered silicates that have been organically treated for the purpose of delamination can also be used as inorganic reinforcing material (C). Among these, glass fibers and carbon fibers are particularly preferred. These inorganic reinforcing materials (C) may be one type or a combination of two or more types.

[0016] When using a fibrous reinforcing material as the inorganic reinforcing material (C), it is preferable that the material has been pre-treated with a coupling agent such as an organosilane compound, organotitanium compound, organoborane compound, or epoxy compound, and is particularly preferable that it readily reacts with carboxylic acid groups and / or carboxylic acid anhydride groups. A polyamide resin composition containing glass fibers treated with a coupling agent is preferable because it yields molded articles with excellent mechanical properties and appearance characteristics. In addition, if the coupling agent is untreated, other fibrous reinforcing materials can be added later.

[0017] When the inorganic reinforcing material (C) is glass fiber, chopped strand glass fiber with a fiber length of about 1 to 20 mm can be preferably used. As the cross-sectional shape of the glass fiber, circular cross-section and non-circular cross-section glass fibers can be used. From the perspective of physical properties, non-circular cross-section glass fibers are preferred as the cross-sectional shape of the glass fiber. The non-circular cross-section glass fibers include those that are substantially elliptical, substantially oval, or substantially cocoon-shaped in the cross-section perpendicular to the fiber length direction, and the flatness ratio is preferably 1.5 to 8. Here, the flatness ratio is the ratio of the major axis to the minor axis when assuming a rectangle with the minimum area circumscribing the cross-section perpendicular to the longitudinal direction of the glass fiber, taking the length of the long side of this rectangle as the major axis and the length of the short side as the minor axis. The thickness of the glass fiber is not particularly limited, but the minor axis is about 1 to 20 μm and the major axis is about 2 to 100 μm.

[0018] The glass fiber is preferably treated with a coupling agent such as a silane-based or titanate-based coupling agent, and in particular, the glass fiber treated with a silane-based coupling agent can be preferably used. Examples of preferred silane-based coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. In particular, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane are preferred.

[0019] The blending ratio of the inorganic reinforcing material (C) with respect to a total of 100 parts by mass of the aliphatic polyamide resin (A), polyamide MXD6 resin (B) and inorganic reinforcing material (C) is 30 to 59 parts by mass. Preferably it is 40 to 59 parts by mass, more preferably 45 to 59 parts by mass, and still more preferably 50 to 59 parts by mass. If it is less than 30 parts by mass, there is a risk of insufficient rigidity, and if it exceeds 59 parts by mass, there is a risk of inferior appearance of the molded product. When the blending ratio of the inorganic reinforcing material (C) is 40 to 59 parts by mass, it is preferable because the balance between rigidity and molding appearance is particularly excellent.

[0020] It is preferable that the polyamide resin composition of the present invention contains a hypophosphite metal salt (D). The hypophosphite metal salt (D) is a salt of hypophosphorous acid and metals of Groups 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13 of the periodic table of elements and metals such as tin and lead, and may be used alone or in combination of two or more. Among these, from the viewpoint of more significantly achieving the effects of the present invention, sodium hypophosphite (NaH2PO2) and calcium hypophosphite (Ca(H2PO2)2) are preferable. The hypophosphite metal salt may be a hydrate, and examples include sodium hypophosphite monohydrate (NaH2PO2·H2O).

[0021] The blending amount of the hypophosphite metal salt (D) is preferably 0.001 to 3 parts by mass, more preferably 0.05 to 1.5 parts by mass, and still more preferably 0.08 to 0.8 parts by mass with respect to a total of 100 parts by mass of the aliphatic polyamide resin (A), polyamide MXD6 resin (B) and inorganic reinforcing material (C). Even if the hypophosphite metal salt (D) is not blended, a molded product excellent in high strength, high rigidity, and high temperature rigidity can be obtained. However, when the hypophosphite metal salt (D) is present within a specific range, the amide exchange reaction between the crystalline aliphatic polyamide resin and polyamide MXD6 is promoted, which is preferable for stabilizing the properties of the resin composition.

[0022] The polyamide resin composition of the present invention has a melt flow rate (MFR) of 3 to 60 g / 10 min, measured under conditions of a load of 2.16 kg and a temperature of 275°C, preferably 3 to 45 g / 10 min, more preferably 4 to 25 g / 10 min, even more preferably 5 to 20 g / 10 min, and most preferably 5 to 15 g / 10 min. If the MFR is less than 3 g / 10 min, the fluidity may be insufficient in the case of thin-walled molded products, and if the MFR exceeds 60 g / 10 min, there is a tendency for burrs to easily form on the molded product. This MFR can be achieved by using the above configuration for the polyamide resin composition.

[0023] The polyamide resin composition of the present invention is preferable for obtaining molded articles having the effects of the present invention if the MFR measured under conditions of a load of 2.16 kg and 275°C is 4 to 25 g / 10 min, as it exhibits excellent fluidity. This MFR can be achieved by adjusting the composition of the polyamide resin composition.

[0024] The polyamide resin composition of the present invention preferably has a cooling crystallization temperature of 160 to 190°C, more preferably 170 to 185°C, which is determined by DSC measurement at a heating rate of 20°C / min in accordance with JIS K7121. If the cooling crystallization temperature is less than 160°C, the solidification rate will be slow, and the molding cycle may become too long. If it exceeds 190°C, the effect of improving the appearance of the molded product may be poor.

[0025] Furthermore, in addition to the above, the polyamide resin composition of the present invention may optionally contain heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, plasticizers, lubricants, crystal nucleating agents, mold release agents, antistatic agents, halogenated flame retardants and antimony oxide combinations, various phosphoric acid-based flame retardants, melamine-based flame retardants, inorganic pigments, organic pigments, dyes, or other polymers, as needed within a known range. The polyamide resin composition of the present invention preferably contains 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, in total, the aliphatic polyamide resin (A), polyamide MXD6 resin (B), inorganic reinforcing material (C), and metal hypophosphite salt (D).

[0026] The method for producing the polyamide resin composition of the present invention is not particularly limited as long as it is capable of melt-kneading, but a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, roll, etc. can be used, and the use of a twin-screw extruder is preferred. In the case of a twin-screw extruder, it is preferable to pre-mix the above-mentioned (A), (B) and various additives, and optionally (D) component dissolved in water, in a tumbler or Henschel mixer, supply the pre-mixed mixture from the main feeder, supply (C) component from the side feeder, and melt-knead at a temperature range of 220 to 330°C. The polyamide resin composition that has been melt-kneaded and discharged in strand form into cooling water is pelletized to a length of about 1 to 10 mm by a pelletizer.

[0027] The polyamide resin composition of the present invention can be molded into articles by known molding methods. The molding method is not specified, and it can be suitably used in injection molding, blow molding, extrusion molding, foam molding, distorted molding, calendering, and various other molding methods. Among these, injection molding is preferred. Molded articles made from the polyamide resin composition of the present invention have high rigidity and excellent appearance, making them suitable as metal substitute parts in fields such as automobiles, electrical and electronic components, and household goods. For example, they are suitable for door mirror parts and circuit breaker parts. [Examples]

[0028] The present invention will now be specifically described using examples and comparative examples, but the present invention is not limited to these. The measured values ​​and evaluations in the examples were obtained by the following methods.

[0029] 1. Measurement Method and Evaluation Method (1) Relative viscosity (RV) of polyamide resin: The polyamide resin was measured using an Ubbelohde viscous tube at 25°C with a 96% by mass sulfuric acid solution at a concentration of 1 g / dl. (2) Cooling down crystallization temperature (Tc2): A DSC measuring device (Seiko Instruments, EXSTAR6000) was used. The temperature was raised to 300°C at a heating rate of 20°C / min under a nitrogen stream, held at that temperature for 5 minutes, and then cooled to 50°C at a rate of 10°C / min. The peak temperature of the crystallization peak observed at this temperature was measured.

[0030] (3) Melt Flow Rate (MFR): Measurements were performed in accordance with ISO 1133. The obtained polyamide resin composition pellets were dried until the moisture content was less than 0.1% by mass, and measurements were taken at a temperature of 275°C and a load of 2.16 kg.

[0031] (4) Bending strength, bending modulus: Measurements were taken in accordance with ISO-178. (5) Charpy impact strength: Measurements were taken in accordance with ISO-179-1eA. (6) Heat distortion temperature: The temperature of deflection under a load of 1.82 MPa was measured in accordance with JIS K 7191-2:2015.

[0032] (7) Method for evaluating the appearance of molded products: The specular gloss of the molded product was measured and evaluated using the following method. Using a mirror-finished mold measuring 100mm x 100mm x 3mm (thickness), molded parts were produced at a resin temperature of 280°C and a mold temperature of 80°C. The glossiness was measured at an incident angle of 60 degrees in accordance with JIS Z-8714. A higher value indicates better glossiness. The gloss level measurement results were evaluated based on the following criteria. ◎: 97 or higher ○: 95 or higher, less than 97 △: 90 or higher, less than 95 ×: Less than 90

[0033] 2. Raw materials used in the examples and comparative examples [Polyamide resin] A-1: Polyamide 6 Toyobo's "Gramide T-800" (RV2.6) B-1: Polyamide MXD6 Toyobo's "Gramide T-600" (RV2.1) B-2: Polyamide 6T6I 6T / 6I = 33 / 67 (mol%), EMS Grivoly G21 (RV2.0) [Inorganic reinforcement] C-1: Glass fiber Nippon Electric Glass Co., Ltd., ECS03T-275H C-2: Talc Hayashi Chemical Co., Ltd., Tarkan Powder PK [Metal hypophosphite salts] D-1: Sodium hypophosphite [Other additives] E-1: Magnesium stearate E-2: Pigment Sumitomo Chemical Color Co., Ltd., EPC-840

[0034] [Examples 1-13, Comparative Examples 1-4] To obtain the compositions shown in Table 1 below, each component except the inorganic reinforcing material was pre-mixed in a tumbler. The pre-mixed mixture was then supplied from the main feeder of a twin-screw extruder (TEM-1008, L / D=40) and the inorganic reinforcing material from the side feeder. The mixture was melt-kneaded (main barrel temperature 270°C, discharge rate: 350 kg / hr or 450 kg / hr), and the strands of resin composition discharged in a water bath were pelletized with a strand cutter to obtain pellets of each resin composition. The obtained resin composition pellets were dried and then evaluated using the method described above. The results are shown in Table 1.

[0035] [Table 1]

[0036] From the resin compositions of each example, it can be seen that molded articles with high strength, high rigidity, good appearance, and excellent high-temperature rigidity can be obtained. In particular, when the blending ratio of inorganic reinforcing material (C) is 40 to 59 parts by mass, an excellent balance between rigidity and molded appearance is obtained. As shown in Examples 1 and 2 (6 and 7, 8 and 9, 10 and 11), by including a predetermined amount of metal hypophosphite salt, the resin composition of the present invention exhibits minimal change in melt fluidity even when the extruder discharge rate fluctuates significantly. The resulting molded articles have excellent appearance and consistently superior mechanical properties. In Examples 4 and 5, which do not contain metal hypophosphite, the inclusion of polyamide MXD6 resin resulted in a relatively small effect on discharge volume fluctuations and an improvement in the appearance of the molded product.

[0037] In Comparative Examples 1 and 2, which did not contain polyamide MXD6 resin, the appearance of the molded articles was significantly inferior. In Comparative Examples 3 and 4, which contained the amorphous polyamide resin polyamide 6T6I instead of polyamide MXD6 resin, the molded articles had a superior appearance, but the rigidity, heat resistance, and mechanical properties of the molded articles were reduced. In addition, in Comparative Examples 3 and 4, the change in the physical properties of the resin composition when the extruder discharge rate fluctuated significantly was somewhat larger than in Examples 1 and 2. [Industrial applicability]

[0038] The polyamide resin composition of the present invention is less susceptible to fluctuations in manufacturing conditions and can stably provide molded products with high rigidity and good appearance. Therefore, it is suitable as a molding material for parts and molded products in fields such as automobiles, electrical and electronic components, and household goods where high rigidity and good appearance are required.

Claims

1. A polyamide resin composition containing an aliphatic polyamide resin (A), a polyamide MXD6 resin (B), and an inorganic reinforcing material (C), The mixture contains, in proportion to 100 parts by mass of the aliphatic polyamide resin (A), the polyamide MXD6 resin (B), and the inorganic reinforcing material (C), 20 to 42 parts by mass of the aliphatic polyamide resin (A), 5 to 20 parts by mass of the polyamide MXD6 resin (B), 51 to 59 parts by mass of the inorganic reinforcing material (C), and 0 to 3 parts by mass of the metal hypophosphite salt (D). The polyamide MXD6 resin (B) is a polyamide resin mainly composed of polymetaxylylene adipamide, which is a polycondensate of a diamine component in which at least 80 mol% is metaxylylenediamine and a dicarboxylic acid component in which at least 80 mol% is adipic acid. The diamine component can be paraxylylenediamine, tetramethylenediamine, or hexamethylenediamine in an amount of 20 mol% or less, and the dicarboxylic acid component can be an aliphatic dicarboxylic acid in an amount of 20 mol% or less. A polyamide resin composition characterized in that the MFR measured under the conditions of a load of 2.16 kg and 275°C is 3 to 60 g / 10 min.

2. The polyamide resin composition according to claim 1, wherein the cooling crystallization temperature of the polyamide resin composition is 160 to 190°C.

3. The polyamide resin composition according to claim 1 or 2, wherein the hypophosphate metal salt (D) is contained in an amount of 0.001 to 3 parts by mass with respect to a total of 100 parts by mass of (A), (B), and (C).

4. The polyamide resin composition according to any one of claims 1 to 3, characterized in that the aliphatic polyamide resin (A) in the polyamide resin composition contains 20 to 50 parts by mass with respect to a total of 100 parts by mass of (A), (B), and (C).

5. The polyamide resin composition according to any one of claims 1 to 4, characterized in that the inorganic reinforcing material (C) is glass fiber.

6. The polyamide resin composition according to any one of claims 1 to 5, characterized in that the MFR of the polyamide resin composition measured under the conditions of a load of 2.16 kg and 275°C is 4 to 25 g / 10 min.

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