JPWO2019172354A1 - Polyamide resin composition - Google Patents

Abstract

The polyamide resin composition of the present invention can provide a molded product having high vibration characteristics even after water absorption and having an excellent appearance, and is a polyamide (a2) containing an aliphatic polyamide (a1) and an aromatic component. A polyamide resin composition containing a polyamide resin (A) composed of the above, and a glass fiber (B) having a cross-sectional area of 1.5 × 10-6 to 5.0 × 10-6 cm2. The mass ratio ((A): (B)) of A) to the glass fiber (B) is 20:80 to 35:65, and the mass ratio of the aliphatic polyamide (a1) to the polyamide (a2) containing an aromatic component. ((A1) :( a2)) is 0: 100 to 95: 5, and the polyamide (a2) containing an aromatic component is a polyamide containing metaxylylene diamine and sebacic acid as constituent components. It is a polyamide resin composition to be used.

Description

In the present invention, the specific elastic modulus is increased by adding glass fibers having a specific cross-sectional area to a polyamide resin having low water absorption and a high glass transition temperature, and extremely high resonance is maintained while maintaining the good appearance required for automobile parts. The present invention relates to a polyamide resin composition that has achieved a frequency. The polyamide resin composition of the present invention can be suitably used as a molded product such as a housing for electrical and electronic parts and vehicle parts used for automobile interiors and exteriors, for example, exterior mirror body parts for supporting door mirrors. In particular, it is possible to realize an unprecedented downsizing of each molded product.

By reinforcing the polyamide resin with glass fiber, it is possible to exhibit not only high rigidity and high toughness but also high load flexibility. Therefore, the glass fiber reinforced polyamide resin composition is widely used as an internal member and an external member in the fields of electrical and electronic equipment and automobiles. In recent years, the level of vibration characteristics required due to the thinning of product wall thickness, especially in electrical and electronic members, and the miniaturization of vehicle parts has increased, and the thermoplasticity with a higher specific elastic modulus expressed by elastic modulus / specific gravity has increased. A resin composition is required. Further, since the polyamide resin molded product is inferior in weather resistance to the polymethyl methacrylate resin (PMMA) molded product and the like, the weather resistance of the product is often imparted in the post-molding process such as painting. Further, when the filling amount of glass is 60% by mass or more, the weather resistance is remarkably deteriorated, and it cannot be used particularly as a vehicle interior or exterior part.

In Patent Document 1, a resin composition having a high resonance frequency and vibration resistance is obtained by copolymerizing a nylon 66 base with an isophthalamide component that reduces crystallinity and blending 60% or more of a reinforcing material such as glass fiber. .. However, the increase in elastic modulus is not sufficient due to the component that lowers the crystallinity, and a good balance between the flexural modulus and the specific gravity for obtaining a resonance frequency of 200 Hz or higher in the test sample shape has not been obtained. In addition, there is a problem that the elongation and impact resistance are lowered by adding mica.

Patent Document 2 discloses a long-fiber polyamide molding material in which a polyamide resin and a glass roving fiber having a non-circular cross section are combined. However, in the examples of this patent document, 60% or more of glass fiber is not blended, and therefore the elastic modulus / specific gravity which is proportional to the resonance frequency is not sufficiently high, so that the strength and impact are high. Even a molding material having characteristics does not exhibit sufficient characteristics in terms of vibration resistance.

In Patent Document 3, a plurality of resins such as polyamide 6, polyamide 66, and non-crystalline polyamide are used as a blend base instead of copolymerization, a reinforcing material is highly filled while maintaining crystallinity, and an optimum amount of polypropylene is added. As a result, a high resonance frequency is obtained and at the same time, damping characteristics are also imparted. However, as the current vibration resistance requirement, a resonance frequency of 230 Hz or higher is required in the test method of Patent Document 3, and when a resin having a low elastic modulus such as polypropylene is used as a component, this cannot be reached at all. Absent. Therefore, there is a demand for a combination of glass fiber and a thermoplastic resin, which can exhibit characteristics having a higher specific elastic modulus.

Patent Document 4 discloses a polyamide resin composition that achieves an extremely high resonance frequency by increasing the specific elastic modulus by adding glass fibers having a specific cross-sectional area to an aliphatic polyamide and an aromatic polyamide resin. ing. However, in this polyamide resin composition, the elastic modulus decreases after water absorption, so that the vibration characteristics deteriorate in actual use.

Patent Document 5 describes a polyamide resin composition that achieves an extremely high resonance frequency even after water absorption by increasing the specific elastic modulus by adding glass fibers having a specific cross-sectional area to the aromatic polyamide resin. It is disclosed. However, this aromatic polyamide resin has a high melting point and is extremely difficult to process. In addition, there is no description about the appearance, and it is hard to say that both the appearance and the vibration characteristics after water absorption are compatible.

Japanese Unexamined Patent Publication No. 7-118522 Japanese Unexamined Patent Publication No. 2008-95066 Japanese Unexamined Patent Publication No. 2005-162775 International release WO2014 / 171363 International release WO2015 / 00196

The present invention was devised in view of the current state of the prior art, and an object of the present invention is to obtain a molded product having high vibration resistance, that is, an extremely high resonance frequency, and to have high vibration characteristics even after water absorption. At the same time, it is an object of the present invention to provide a polyamide resin composition having an excellent appearance.

As a result of diligent studies to achieve such an object, the present inventor adds a glass fiber having a specific shape cross-sectional area to a polyamide resin to develop an elastic coefficient with respect to its specific gravity (density). Glass fiber with a cross-sectional area of 9.5 x ^10-7 cm ² (glass fiber diameter 11 μm) and a cross-sectional area of 13.3 x ^10-7 cm ² (glass fiber) that are used for maximum purpose and are used for general purposes. By reducing the number of fibers and the surface area of the glass fibers as compared with the glass fibers having a diameter of 13 μm), the appearance of the molded product can be improved despite the high filling amount of the glass fibers. However, when the polyamide 6 or the polyamide 66 is used as the resin, the elastic modulus is lowered due to water absorption, and the expected performance cannot be obtained. Further, when a polyamide resin having a high glass transition temperature is used in order to maintain a high elastic modulus even after water absorption, the polyamide resin generally has an aromatic ring as a skeleton, so that the melting point and the crystallization temperature are high. Even if the mold temperature is raised sufficiently, it is difficult to obtain a good appearance with the glass fiber reinforced system. Therefore, it is necessary to adjust the fluidity and crystallinity to improve the appearance by adding another polyamide having a certain compatibility. However, in this case, since the melting point of the resin is high, the crystallinity may be significantly impaired when the resin is extruded and kneaded. Therefore, the production condition range is very narrow, and the production is very difficult and stable. poor. In addition, the elastic modulus decreases due to the decrease in crystallinity. The present invention is a polyamide resin composition containing glass fibers having a specific cross-sectional area in a polyamide resin containing a polyamide resin having a low water absorption rate and a high glass transition temperature, and a molded product made of this polyamide resin composition is in water. With respect to X = E / ρ consisting of the bending elasticity E (unit: GPa) when water is absorbed to equilibrium and the density ρ (g / cm ³ ) of the molded product, 18>X> 8.0 is satisfied and 2.0. It is a molded product having a good appearance with>ρ> 1.7. This molded product not only has a high resonance frequency that could not be achieved by the prior art, but also has excellent appearance, heat resistance, strength, and impact resistance by eliminating deterioration of vibration characteristics during water absorption.

That is, the present invention adopts the following configurations (1) to (5).
(1) A polyamide resin (A) composed of an aliphatic polyamide (a1) and a polyamide (a2) containing an aromatic component, and a cross-sectional area of 1.5 × ^{10-6 to} 5.0 × ^10-6 cm ² The polyamide resin composition containing the glass fiber (B) of the above, wherein the mass ratio ((A) :( B)) of the polyamide resin (A) and the glass fiber (B) is 20:80 to 35:65. Yes, the mass ratio ((a1) :( a2)) of the aliphatic polyamide (a1) and the polyamide (a2) containing an aromatic component is 0: 100 to 95: 5, and the polyamide (a2) containing an aromatic component. Is a polyamide resin composition comprising metaxylylene diamine and sebacic acid as constituents.
(2) The polyamide resin composition according to (1), wherein the aliphatic polyamide (a1) is a polyamide 66.
(3) The polyamide resin composition according to (1) or (2), wherein a part or all of the glass fiber (B) is a flat cross-section glass fiber.
(4) The polyamide resin composition according to any one of (1) to (3), further containing the copper compound (C) in an amount of up to 0.5% by mass.
(5) A molded product made of the polyamide resin composition according to any one of (1) to (4), which has a density ρ (g / cm ³ ) of the molded product and a flexural modulus when water is absorbed to equilibrium in water. A molded product characterized in that E (GPa) satisfies 8.0 <E / ρ <18, 1.7 <ρ <2.0.

In the polyamide resin composition of the present invention, by defining the cross-sectional area of the glass fiber to be added in a specific range, the expression of the elastic ratio with respect to the density can be controlled in the glass fiber high filling region, and the glass fiber is 65% by mass. In the above composition, by using a polyamide resin having a low equilibrium water absorption in water and a high glass transition temperature, a high resonance frequency can be obtained even in actual use, and high strength and impact resistance are further excellent. Since it has weather resistance and discoloration resistance, it is extremely suitable as a housing for electrical and electronic equipment and parts for interior and exterior of automobiles.

FIG. 1 is a schematic view of a vibration test device for evaluating resonance frequency.

The polyamide resin composition of the present invention comprises a polyamide resin (A) composed of an aliphatic polyamide (a1) and a polyamide (a2) containing an aromatic component, and a cross-sectional area of 1.5 × ^{10-6 to} 5.0. It contains x ^10-6 cm ² of glass fiber (B). The polyamide resin composition of the present invention contains the above (A) and (B) as main constituents, and it is preferable that the total of them accounts for 95% by mass or more.

The polyamide resin (A) is preferably partially a crystalline resin from the viewpoint of developing a flexural modulus with respect to the density when glass fibers are added, and further, the ratio of the crystalline polyamide resin is large (for example, 50 mass). % Or more) is preferable. The polyamide resin is a polyamide resin obtained by polycondensing lactam, ω-aminocarboxylic acid, dicarboxylic acid, diamine and the like as raw materials, or a copolymer or blend thereof. Examples of lactam and ω-aminocarboxylic acid include ε-caprolactam, 6-aminocaproic acid, ω-enantractum, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone and α-piperidin. And so on. Examples of the dicarboxylic acid include dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid and sebacic acid. Examples of diamines include tetramethylenediamine, hexamethylenediamine, m-xylylenediamine, paraxylylenediamine, undecamethylenediamine, dodecamethylenediamine, 2-methylpentamethylenediamine, trimethylhexamethylenediamine, aminoethylpiperazine, and bis. Aminomethylcyclohexane and the like can be mentioned.

In order to satisfy both high flexural modulus and high impact resistance at the same time, the polyamide resin (A) contains an aliphatic polyamide (a1) and a polyamide (a2) having an aromatic component (a1) :( a2) = 0. It is necessary to mix and use at a mass ratio of: 100 to 95: 5. The polyamide resin for injection molding preferably maintains a certain level of crystallinity, and when the polyamide (a2) having an aromatic component is crystalline, (a1) :( a2) = 0: 100 to 75: A mass ratio of 25 is more preferable from the viewpoint of moldability and heat resistance. (A1): (a2) = 0: 100 to 70:30 is more preferable, and (a1) :( a2) = 0: 100 to 45:55 is particularly preferable. From the viewpoint of suppressing deterioration of vibration characteristics during water absorption, it is particularly preferable that (a1) :( a2) = 0: 100 to 20:80.

As the polyamide (a2) having an aromatic component, a polyamide resin that exhibits a high elastic modulus, adjusts the solidification rate, and improves the strand property during production and the mold transfer property during injection molding is preferable. As the polyamide (a2) containing an aromatic component, the polyamide MXD10 (polymethoxylylene sebacamide) containing metaxylylenediamine and sebacic acid as constituent components is optimal. Considering compatibility, strength development, toughness retention, and rigidity development when used in combination with the aliphatic polyamide (a1), the polyamide (a2) containing an aromatic component is preferably a crystalline polyamide containing a metaxylylenediamine as a component. Further, considering the retention of elastic modulus during equilibrium water absorption in water, it is preferable that the glass transition temperature is 70 ° C. or higher and the water absorption rate after equilibrium water absorption in water is 3.5% or less. Therefore, the polyamide MXD10 is preferable from this point as well. ..

As the aliphatic polyamide (a1), polyamide 6, polyamide 66, polyamide 46, polyamide 610 and the like are preferable in terms of moldability, heat resistance, toughness, rigidity and the like. The aliphatic polyamide (a1) preferably has a relative viscosity of 1.8 to 2.8 in a 98% sulfuric acid solution. As a result, while maintaining a certain degree of toughness, the productivity when highly filling the glass fiber having a specific cross-sectional area and the fluidity of the resin composition during molding are improved, and the appearance of the molded product is improved. As the aliphatic polyamide (a1), polyamide 66 is particularly preferable.

In order to satisfy the high flexural modulus and maintain the high elastic modulus even during the equilibrium water absorption in water, the polyamide resin (A) is mainly composed of the polyamide MXD10 (preferably 55% by mass or more), and the polyamide 6 , Polyamide 66, or Polyamide 610 is preferably blended.

The polyamide resin (A) preferably has a carboxyl group or an amino group at the molecular end in order to efficiently react with the coupling agent surface-treated on the glass. Specifically, the polyamide resin (A) is preferably 10 to 95 meq / kg with respect to the terminal carboxyl group concentration (CEG: meq / kg).

The polyamide resin composition of the present invention needs to have a mass ratio ((A) :( B)) of the polyamide resin (A) to the glass fiber (B) of 20:80 to 35:65. As a result, in the molded product made of the polyamide resin composition of the present invention, the density ρ (g / cm ³ ) of the molded product and the flexural modulus E (GPa) when water is absorbed to equilibrium in water are 8.0 <E / ρ <. 18, 1.7 <ρ <2.0 can be satisfied. When the mass ratio of the glass fiber (B) is lower than the above range, the above-mentioned value of E / ρ may be 1.7 or less, and a sufficiently high resonance frequency cannot be obtained. When the mass ratio of the glass fiber (B) is higher than the above range, not only the ratio of the glass fiber (B) becomes too high to efficiently produce a molded product, but also the interface between the glass fiber (B) and the polyamide resin is defective. However, sufficient strength and impact resistance cannot be obtained. (A): (B) is preferably 22:78 to 33:67, more preferably 24:76 to 30:70.

It is preferable to use flat cross-section glass fiber for a part (for example, 50% by mass or more) or all of the glass fiber (B). The flat cross-section glass fiber includes a fiber having a substantially elliptical shape, a substantially oval shape, and a substantially cocoon shape in a cross section perpendicular to the length direction of the fiber, and the flatness is preferably 1.5 to 8. More preferably, it is 2 to 5. Here, the flatness is assumed to be a rectangle having the smallest area circumscribing a cross section perpendicular to the longitudinal direction of the glass fiber, the length of the long side of this rectangle is the major axis, and the length of the short side is the minor axis. This is the ratio of major axis / minor axis when When the flatness is less than the above range, the impact resistance of the molded product may not be improved so much because there is no large difference in shape from the glass fiber having a circular cross section. On the other hand, when the flatness exceeds the above range, the bulk density in the polyamide resin becomes high, so that it may not be uniformly dispersed in the polyamide resin, and the impact resistance of the molded product may not be improved so much. In the present invention, glass fibers having a substantially oval cross section and a flatness of 2 to 5 are particularly preferable because they exhibit high mechanical properties. In the present invention, it is necessary that the thickness of the glass fiber (B) is limited to 1.5 × ^{10-6 to} 5.0 × ^10-6 cm ² in terms of cross-sectional area regardless of its cross-sectional shape. A glass fiber having a round cross section having a diameter of 11 μm and 13 μm, which is conventionally used for general purposes, is not preferable because physical properties are not efficiently expressed in a high filling region of 65% by mass or more. When flat cross-section glass fiber is used for a part or all of the glass fiber, the minor axis / major axis ratio is 0.3 to 0.5 and the minor axis / major axis ratio is 0.3 to 0.5. Flat cross-section glass fiber (B-2) of 0.2 to 0.3 is used in combination at (B-1) :( B-2) = 0: 100 to 100: 0, preferably 10: 90 to 90:10. By doing so, it is possible to control the warp and shrinkage of the molded product and the value of bending elasticity / density, and to add carbon black, hindered amine light stabilizer, ultraviolet absorber, etc. necessary for improving the weather resistance. The agent can be sufficiently added.

In the present invention, it is important to obtain a polyamide resin composition pellet having a higher flexural modulus with respect to density when the glass fiber (B) is added to the polyamide resin (A). Therefore, it is necessary to use glass fibers having a specific range of cross-sectional areas with a small number of glass fibers and less interference between the glass fibers. In this case, the required cross-sectional area of the glass fiber (B) is 1.5 × ^{10-6 to} 5.0 × ^10-6 cm ² . If the cross-sectional area of the glass fiber is smaller than this, not only the number of fibers per unit mass increases, but also each single yarn is easily broken, so that the fiber length can be increased with a high filling rate in pellet granulation of a twin-screw extruder. It is not possible to obtain pellets that are kept effective. The cross-sectional area of the glass fiber (B) is preferably 1.5 × ^{10-6 to} 3.0 × ^10-6 cm ² .

Glass fibers having various cross-sectional shapes are applied to the glass fibers (B), but the glass fibers are hard to break during pellet production, and because the surface area of the glass fibers is large, the physical properties are greatly exhibited, and the molded product is warped and deformed. From the viewpoint of being able to suppress the glass fiber, it is preferable that the glass fiber used for the purpose of increasing the elastic coefficient with respect to the density includes a glass fiber having a flat cross-sectional shape. Further, by using a plurality of types of glass fibers (B) having a flat cross section having different deformed ratios during kneading with the polyamide resin (A), the resin flow pattern is disturbed and a fast resin flow from a specific orifice hole of the extruder is performed. Can be suppressed. As a result, the productivity is remarkably improved in the production method of granulating pellets by biaxial extrusion and strand cutting, and it is possible to efficiently obtain composition ratio pellets exhibiting a high flexural modulus with respect to density.

In producing the polyamide resin composition of the present invention, a polyamide-reactive silane is used for a mixture of the polyamide resin (A) and the glass fiber (B), especially when a flat cross-section glass fiber is used for the glass fiber (B). It is preferable to add the coupling agent at a ratio of 0.1 to 1.0% by mass of the glass fiber (B). The sizing agent for chopped strands for polyamide contains a small amount of a silane coupling agent in advance in the fiber bundle in order to improve the adhesiveness with the matrix resin. However, since there is an upper limit to the amount of the aminosilane coupling agent that can be attached to the fiber bundle in advance so that the fiber bundle does not cause defibration failure during extrusion, it is preferable to additionally add the shortage.

Carbon black may be added to the polyamide resin composition of the present invention in order to improve weather discoloration resistance. Carbon black produced by the current mainstream furnace method is called "furness black" and is distinguished from carbon black produced by other methods. The furnace method of furnace black is a method in which petroleum-based or coal-based oil is blown into a high-temperature gas and incompletely burned to obtain carbon black, which has a high yield and is suitable for mass production and has a particle size. It is the most commonly used method for producing carbon black for various purposes, from rubber reinforcement to coloring, because it can be widely controlled such as and structure. On the other hand, the channel method of channel black is a method in which carbon black is precipitated by contacting an incompletely burned flame with channel steel (H-shaped steel), mainly using natural gas as a raw material, and scraping and collecting the carbon black. However, due to problems in yield and environment, the furnace method has become the mainstream as a mass production process. The acetylene method of acetylene black is a method of obtaining carbon black by thermal decomposition of acetylene gas. Carbon black having a high structure and high crystallinity can be obtained, and it is mainly used as a conductivity-imparting agent. Oil smoke black (lamp black) is a method of recovering carbon black as soot from the smoke generated when burning oil or pine. It is a method that has continued since BC and is not suitable for mass production, but it has a unique color tone. It is used as a raw material for solid ink because it produces carbon black. The carbon black used in the present invention may be any of the above-mentioned carbon blacks, but if it is selected from the viewpoint of price, it is preferably carbon black produced by the furnace method. The content of carbon black in the polyamide resin composition of the present invention is 0 to 5% by mass, and from the viewpoint that the color of the molded product obtained from the polyamide resin composition is other than black, it is preferably 0 to 0. It is 5% by mass, more preferably 0 to 0.3% by mass. Setting the carbon black content to 0% by mass is one of the preferred embodiments. When the weather resistance and discoloration resistance are surely improved, the content of carbon black is preferably 0.3 to 5% by mass.

A hindered amine light stabilizer may be added to the polyamide resin composition of the present invention in order to improve weather discoloration resistance. The hindered amine light stabilizer refers to a compound (HALS) having a 2,2,6,6-tetramethylpiperidine structure. The content of the hindered amine light stabilizer is preferably 0 to 1.0% by mass in the polyamide resin composition of the present invention. By blending a hindered amine light stabilizer with the polyamide resin composition of the present invention, weather resistance is improved. If the blending ratio is less than the above range, the contribution to weather resistance is small, while if it exceeds the above range, the amount of gas increases during production and molding, which tends to impair productivity.

In the polyamide resin composition of the present invention, an ultraviolet absorber may be added in order to improve weather discoloration resistance. As the ultraviolet absorber, a known ultraviolet absorber can be used. The content of the ultraviolet absorber is 0 to 1% by mass, preferably 0.05 to 1% by mass, and more preferably 0.1 to 0.8% by mass in the polyamide resin composition of the present invention. is there. The UV absorber can further improve the weather resistance when used in combination with the hindered amine light stabilizer.

The polyamide resin composition of the present invention contains the copper compound (C) in an amount of up to 0.5% by mass, more at least 0.01% by mass, and at most 0.4% by mass in order to improve heat resistance. Can be contained in. Specific examples of the copper compound include copper chloride, copper bromide, copper iodide, copper acetate, copper acetylacetonate, copper carbonate, copper borofluoride, copper citrate, copper hydroxide, copper nitrate, copper sulfate, and oxalic acid. Examples include copper. In the present invention, it is also possible to add a stabilizer, for example, an alkali halide compound as another additive component in combination with the copper compound. Examples of the alkali metal halide compound include lithium bromide, lithium iodide, potassium bromide, potassium iodide, sodium bromide and sodium iodide, and potassium iodide is particularly preferable.

In addition, the polyamide resin composition of the present invention has other additive components, such as the above stabilizer, the above, as long as the characteristics of the present invention are not impaired with respect to the mixture of the polyamide resin (A) and the glass fiber (B). Coupling agent, inorganic filler, light or heat stabilizer, phenol-based antioxidant, phosphorus-based antioxidant, mold release agent, crystal nucleating agent, lubricant, flame retardant, antistatic agent, pigment, dye, etc. It can be blended in an amount of 5% by mass. This additive component also includes a master base (resin) component when each of the above components is used as a master batch.

The method for producing the polyamide resin composition of the present invention is not particularly limited, and each component can be obtained by melt-kneading by a conventionally known kneading method. The specific kneading device is also not limited, and examples thereof include a single-screw or twin-screw extruder, a kneader, and a kneader, but a twin-screw extruder is particularly preferable in terms of productivity. The screw arrangement is not particularly limited, but it is preferable to provide a kneading zone in order to disperse each component more evenly. As a specific method, the polyamide resin (A) and other additive components are preblended with a blender, put into a single-screw or twin-screw extruder from a hopper, and then at least a part of (A) is melted. Then, the glass fiber (B) is put into the melt mixture by a feeder into a single-screw or twin-screw extruder, and after melt-kneading, the glass fiber (B) is discharged into a strand shape, cooled and cut.

The polyamide resin composition of the present invention can be made into a molded product by a so-called hollow method typified by injection molding, extrusion molding, thermoforming, compression molding, blow molding, die slide molding and the like. The molded product made of the glass fiber reinforced polyamide resin composition of the present invention produced as described above can be obtained by using a specific polyamide resin (A) and a glass fiber (B) having a specific cross-sectional area. The density ρ (g / cm ³ ) and the bending elasticity E (GPa) at the time of equilibrium water absorption in water can satisfy 8.0 <E / ρ <18, 1.7 <ρ <2.0, which is good. Vibration resistance, extremely high bending strength and impact resistance can be achieved.

The resonance frequency F (0) has a relationship of F (0) ∝k (E'/ ρ) ^ (1/2) with respect to the elastic modulus E'(GPa) and the density ρ (g / cm ³ ). , X'= E'/ ρ, which is proportional to the square root of the X'value. That is, in terms of flexural modulus and molded product density, it can be said that a composition composition having a high flexural modulus for the density has a higher resonance frequency in the molded product and improved vibration resistance. In the conventional composition structure mainly premised on injection molding, a glass fiber diameter of 6.5 to 13 μm was optimized in order to increase the strength and impact development with respect to the amount of glass fiber added. That is, as the cross-sectional area, a glass fiber diameter of 3.3 × ^10-7 cm ^{2 to} 1.34 × ^10-6 cm ² was designed as the optimum. Due to its small diameter, the glass fiber having this cross-sectional area has an upper limit of less than 65% by mass in the polyamide resin composition, and the X'value shown in the present invention is that the resonance frequency is proportional to the square root. , X'<11. Sufficient resonance frequency height cannot be obtained in this region. In the present invention, in order to obtain a glass fiber reinforced resin composition pellet which is premised on injection molding and exhibits a resonance frequency higher than this, a thicker glass fiber, that is, a cross-sectional area of 1.5 × 10 ^{-6 to} 5 is obtained. .0 x ^10-6 cm ² glass fiber is used. In addition, when imparting weather resistance, a certain amount or more of carbon black is added. When glass fibers having a conventional cross-sectional area are used, it is extremely difficult to granulate pellets containing 65% by mass or more of glass fibers and carbon black by a twin-screw extruder.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. The method for measuring the physical property values of this example was as follows.

(1) Relative viscosity of polyamide resin: 0.25 g of the polyamide resin was dissolved in 25 ml of 98% sulfuric acid, 10 ml of this solution was placed in an Oswald viscosity tube, measured at 20 ° C., and calculated from the following formula.
RV = T / T0
RV: Relative viscosity, T: Sample solution drop time, T0: Solvent drop time

(2) Flexural modulus: Measured according to ISO-178.

(3) Density: Measured according to JIS-Z8807.

(4) Resonance frequency (at the time of equilibrium water absorption in water): The vibration test was performed by the central vibration method using an ISO tension dumbbell test piece with reference to ISO6721-1 (see FIG. 1). The frequency response function was calculated by fixing the center of the test piece to the exciter, applying vibration from the exciter in an atmosphere of 23 ° C. and 50% RH, and performing a Fourier transform on the acceleration response according to ISO6721-1. The resonance frequency was calculated. As the test piece, the one subjected to the treatment described in the following measurement of equilibrium water absorption in water was used.

(5) Equilibrium water absorption in water:
Using a flat plate having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm, it was allowed to stand in water at 80 ° C., and the change over time of the mass was traced. It was calculated from the following formula.
Equilibrium water absorption in water (%) = (mass during water absorption at 80 ° C.-mass during drying) / mass during drying x 100

(6) Appearance of molded product: Using an injection molding machine (IS-100 manufactured by Toshiba Machine Co., Ltd.), the cylinder temperature is 300 ° C., the mold temperature is 130 ° C., the injection pressure is 90%, the injection speed is 60%, and the holding pressure is 90%. A molded product having a thickness of 100 mm × 100 mm × 2 mm was prepared and evaluated by visual observation according to the following criteria.
◎: There is no floating of glass fiber or reinforcing material in the entire molded product ○: There is a slight floating of glass fiber or reinforcing material near the gate or at the end ×: There is a large amount of floating of glass fiber or reinforcing material in the entire molded product

Polyamide resin used (A)
(A1a) Polyamide 6 having a relative viscosity RV = 1.9, "Nylon T-860" manufactured by Toyobo Co., Ltd.
(A1b) Polyamide 66 having a relative viscosity RV = 2.4, "EPR24" manufactured by Shinma Co., Ltd.
(A1c) Polyamide 610 with relative viscosity RV = 2.7, "RilsanSMVO-F" manufactured by Arkema.
(A2a) Polyamide MXD6 having a relative viscosity RV = 2.1, "T-600" manufactured by Toyobo Co., Ltd.
(A2b) Polyamide MXD10 having a relative viscosity RV = 2.1, "Rilsan XMFO" manufactured by Arkema Co., Ltd.
(A2c) Polyamide 6T / 6I with relative viscosity RV = 2.1, "Gribory G21" manufactured by Ms, non-crystalline polyamide

Glass fiber used (B)
(B1) Flat cross-section glass fiber Chopped strand "CSG3PA810S" manufactured by Nitto Boseki Co., Ltd., flatness 4.0 (minor axis / major axis ratio = 0.25), minor axis 7 μm, fiber length 3 mm cross-sectional area = 1.67 × 10 ^{-6 to} 1.96 x 10 ^-6 cm ²
(B2) Flat section glass fiber chopped strand "CSG3PL810S" manufactured by Nitto Boseki Co., Ltd., flatness 2.5 (minor axis / major axis ratio = 0.4), minor axis 9 μm, fiber length 3 mm cross section = 1.72 × 10 ^{-6 to} 2.03 x 10 ^-6 cm ²
(B3) Circular cross-section glass fiber “T-275N” manufactured by Nippon Electric Glass Co., Ltd. as a chopped strand, diameter 17 μm, fiber length 3 mm Cross-section area = approx. 2.27 × ^10-6 cm ²
(B4) Circular cross-section glass fiber “T-275H” manufactured by Nippon Electric Glass Co., Ltd. as a chopped strand, diameter 11 μm, fiber length 3 mm, cross-sectional area = approx. 9.50 × ^10-7 cm ²

Copper compound used (C)
(C1) Copper bromide (II): manufactured by Wako Pure Chemical Industries, Ltd. Purity 99.6%

Other additive components used Mold release agent: Montanic acid ester wax "WE40" manufactured by Clariant AG
Coupling agent: "KBE903" manufactured by Shin-Etsu Chemical Co., Ltd. as an aminosilane coupling agent
Pigment: Masterbatch carbon black ABF-T-9801 based on acrylonitrile-styrene (AS) manufactured by Regino Color as a black pigment.

<Examples 1 to 7, Comparative Examples 1 to 7>
A polyamide resin composition was obtained by melt-kneading using a twin-screw extruder at the blending ratios shown in Table 1. Various evaluations were performed using this. As is clear from Table 1, the test pieces of Examples 1 to 7 are molded products having an extremely high resonance frequency even when water is absorbed to equilibrium in water, have an excellent flexural modulus during water absorption in water equilibrium, and are vibration resistant. It is useful as a molded product. Further, the flexural modulus value at the time of equilibrium water absorption in water with respect to the density: X = E / ρ shows a high value. On the other hand, the test pieces of Comparative Examples 1 to 7 are inferior to those of Examples.

The molded product made of the polyamide resin composition of the present invention has a high vibration resistance property due to an extremely high resonance frequency, and exhibits a high flexural modulus even after water absorption in water. Therefore, it is suitable for housings of electronic and electrical equipment such as mobile phones and personal computers, and automobile parts, and is particularly suitable for mirror body holding parts for vehicles.

Claims (5)

A polyamide resin (A) composed of an aliphatic polyamide (a1) and a polyamide (a2) containing an aromatic component, and a glass fiber having a cross-sectional area of 1.5 × ^{10-6 to} 5.0 × ^10-6 cm ² . A polyamide resin composition containing (B), wherein the mass ratio ((A) :( B)) of the polyamide resin (A) and the glass fiber (B) is 20:80 to 35:65, and the fat. The mass ratio ((a1) :( a2)) of the group polyamide (a1) and the polyamide (a2) containing an aromatic component is 0: 100 to 95: 5, and the polyamide (a2) containing an aromatic component is metaxiri. A polyamide resin composition, which is a polyamide containing rangeamine and sebacic acid as constituents. The polyamide resin composition according to claim 1, wherein the aliphatic polyamide (a1) is a polyamide 66. The polyamide resin composition according to claim 1 or 2, wherein a part or all of the glass fiber (B) is a flat cross-section glass fiber. The polyamide resin composition according to any one of claims 1 to 3, further comprising a copper compound (C) in an amount of up to 0.5% by mass. A molded product made of the polyamide resin composition according to any one of claims 1 to 4, wherein the density ρ (g / cm ³ ) of the molded product and the bending elasticity E (GPa) when water is absorbed to equilibrium in water are determined. , 8.0 <E / ρ <18, 1.7 <ρ <2.0.