Polyamide resin composition

Abstract

The present invention is a polyamide resin composition which contains 50-90% by mass of (A) a crystalline polyamide resin and 9-49% by mass of (B) a talc, and which preferably additionally contains (C) a coupling agent and (D) a fatty acid metal salt. The average particle diameter of the secondary particles of the talc (B) in this polyamide resin composition is larger than 30 μm; and a molded article of this polyamide resin composition is not susceptible to the occurrence of appearance defects or sink, and is able to stably achieve characteristics within desired ranges.

Description

Technical Field

[0001] The present invention relates to a polyamide resin composition, and more particularly to a polyamide resin composition containing a large amount of talc as a reinforcing material.

Background Art

[0002] As a method for improving drawbacks of polyamide resins such as dimensional changes due to water absorption, reduction in rigidity, and low heat distortion temperature, it has long been widely known to blend fibrous or inorganic fillers such as glass fibers, carbon fibers, talc, and calcium carbonate as reinforcing materials.

[0003] When attempting to blend a large amount of granular inorganic fillers such as talc, since the difference in bulk density between the polyamide resin and the granular inorganic filler is large, it is difficult to sufficiently mix them by simple dry blending using a single-screw extruder. For this reason, a polyamide resin composition having a desired talc content is produced by devising such as sprinkling talc after attaching a coupling agent and water to the polyamide resin (for example, Patent Document 1).

[0004] However, even when the talc content is the same, there may be cases where the appearance of the molded product of the polyamide resin composition is defective or sink marks occur in the molded product. In particular, in the case of appearance parts, there is still room for improvement because there is a problem that good products cannot be continuously obtained even when the molding conditions are changed and the defect rate increases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, the present invention aims to solve the above-mentioned problems, that is, to obtain a polyamide resin composition in which defects in the appearance of molded articles and shrinkage occur less frequently when the talc content is the same, and in which properties within a desired range can be stably obtained. [Means for solving the problem]

[0007] In order to solve the above problems, the inventors diligently researched the aggregation characteristics of talc powder itself, the dispersibility of talc in polyamide resin, and the morphology of polyamide resin compositions. As a result, they found that the dispersion and aggregation state of talc fluctuates and is not always constant. They discovered that by adjusting the maximum outer diameter of the talc aggregates to a specific range, the properties of the resin composition become stable, leading to the present invention.

[0008] In other words, the present invention is "[1] A polyamide resin composition containing 50 to 90% by mass of crystalline polyamide resin (A) and 9 to 49% by mass of talc (B), characterized in that the average particle size of the secondary particles of talc (B) in the polyamide resin composition is greater than 30 μm." [2] The polyamide resin composition according to [1], further comprising a coupling agent (C) and a fatty acid metal salt (D). [3] The polyamide resin composition according to [1] or [2], wherein the crystalline polyamide resin (A) contains an aliphatic polyamide resin.

[0009] By adopting the above configuration, the present invention has made it possible to solve the problem. [Effects of the Invention]

[0010] The polyamide resin composition of the present invention, despite containing a large amount of talc, exhibits fewer defects in the appearance of molded products and fewer sink marks, and stably displays properties within the desired range. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below. The crystalline polyamide resin (A) in the present invention is a polyamide resin having an acid amide bond (-CONH-) in its molecule and having a crystalline melting point. The crystalline polyamide resin (A) preferably contains an aliphatic polyamide resin (A1). Specifically, examples include polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polytetramethylene adipamide (polyamide 46), polyhexamethylene sevacamide (polyamide 610), polylauryl lactam (polyamide 12), poly-11-aminoundecanoic acid (polyamide 11), etc., and other examples include copolymers of these and blends of these polymers, but are not limited to these. As the aliphatic polyamide resin (A1), polyamide 6 and polyamide 66 are preferred, and polyamide 6 is more preferred.

[0012] In the present invention, in addition to the above-mentioned aliphatic polyamide resin (A1), it is preferable from the viewpoint of moldability to use a polyamide resin (A2) that delays the crystallization of the aliphatic polyamide resin (A1) in the crystalline polyamide resin (A). The polyamide resin (A2) is not particularly limited as long as it can delay the crystallization of the aliphatic polyamide resin (A1), but for example, a polyamide with a higher crystallization temperature than the aliphatic polyamide resin (A1) or a polyamide that morphologically inhibits crystallization can be used. Specifically, examples include polyamide MXD6 (polymetaxylylene adipamide), hexamethylene terephthalate / hexamethylene isophthalate copolymer (6T / 6I), 4,4'-diamino-3,3'-dimethyl-dicyclohexylenemethane (CA) / isophthalic acid (I) / lauryl lactam (LL) copolymer (I / CA / LL), and terephthalic acid (T) / trimethyl-hexamethylenediamine (TMD) polymer (T / TMD). Polyamide MXD6 is preferred as the polyamide resin (A2) because it can improve the appearance of the molded article. Polyamide MXD6 is particularly preferred because it can improve not only the appearance of the molded article but also its mechanical properties.

[0013] The preferred ratio of aliphatic polyamide resin (A1) to polyamide resin (A2) is 70 to 99.5 parts by mass of aliphatic polyamide resin (A1) and 0.5 to 30 parts by mass of polyamide resin (A2), with 100 parts by mass of crystalline polyamide resin (A), and more preferably 80 to 95 parts by mass of aliphatic polyamide resin (A1) and 5 to 20 parts by mass of polyamide resin (A2).

[0014] The relative viscosity (96% sulfuric acid method) of the crystalline polyamide resin (A) is preferably in the range of 1.8 to 3.5, and more preferably in the range of 2.0 to 3.2. Below 1.8, toughness decreases, and above 3.5, fluidity tends to decrease. This preferred range of relative viscosity is the same for aliphatic polyamide resin (A1) and polyamide resin (A2). When using aliphatic polyamide resin (A1) and polyamide resin (A2) in combination, the weighted average calculated from the respective content ratios is used as the relative viscosity of the crystalline polyamide resin (A).

[0015] The amount of crystalline polyamide resin (A) blended (contained) in the polyamide resin composition is 50 to 90% by mass, preferably 55 to 80% by mass, more preferably 56 to 74% by mass, and even more preferably 60 to 68% by mass. Below 50% by mass, uniform dispersion of talc is difficult, and performance such as mechanical properties becomes unstable. Above 90% by mass, the effect of improving impact resistance is small.

[0016] In the present invention, the talc (B) preferably has an average primary particle size of 1 to 20 μm, and more preferably 2 to 15 μm. If the average particle size exceeds the above range, the flexural modulus and appearance of the molded product tend to decrease. On the other hand, if the average particle size is below the above range, dispersion problems are likely to occur. The average particle size can be measured by laser diffraction (e.g., LA920W manufactured by Horiba, Ltd.) or by liquid-layer sedimentation type optical transmission method (e.g., Shimadzu CP type, etc.), and the particle size value at a cumulative amount of 50% by weight is read from the particle size cumulative distribution curve. In the present invention, the former method was used for measurement.

[0017] These talcs are obtained by mechanically grinding naturally occurring talcs and then further classifying the resulting material. Alternatively, the material may be further classified after initial rough classification. Mechanical grinding methods include using grinders such as jaw crushers, hammer crushers, roll crushers, screen mills, jet grinders, colloid mills, roller mills, and vibratory mills. These ground talcs are then wet-classified once or repeatedly using devices such as cyclones, cyclone air separators, micro separators, and sharp-cut separators to adjust them to the average particle size shown in this invention. When producing the talcs used in this invention, it is preferable to grind the talcs to a specific particle size and then perform the classification operation using a sharp-cut separator in order to obtain talcs of a specific particle size.

[0018] The talc used in this invention is talc that does not require any surface treatment, but for the purpose of improving adhesion or dispersibility with polyamide resins, modified polyolefins grafted with various organic titanate coupling agents, organic silane coupling agents, unsaturated carboxylic acids, or their anhydrides, fatty acids, fatty acid metal salts, fatty acid esters, etc., may be used. Alternatively, granular talc may be produced by granulating with a water-soluble polymer binder.

[0019] The amount of talc (B) blended (contained) in the polyamide resin composition is 9 to 49% by mass, preferably 19 to 44% by mass, more preferably 25 to 43% by mass, and even more preferably 31 to 39% by mass. Below 9% by mass, the effect of improving mechanical properties is small, and above 49% by mass, uniform dispersion in the polyamide resin becomes difficult, and the mechanical properties and appearance of the molded product tend to become unstable.

[0020] The polyamide resin composition of the present invention preferably contains a coupling agent (C) and a fatty acid metal salt (D) in addition to a crystalline polyamide resin (A) and talc (B).

[0021] As the coupling agent (C), a silane coupling agent, a titanate coupling agent, etc. can be used. Examples of the silane coupling agent include alkoxy group-containing silanes such as methyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, and methacryloxypropyltrimethoxysilane; aminosilane coupling agents such as aminopropyltrimethoxysilane, aminopropyltriethoxysilane, ureidopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, and N-2-(aminoethyl)aminopropyltrimethoxysilane; epoxy silane coupling agents such as glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, and (3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercapto silane coupling agents such as mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane; and organosilazane compounds such as hexamethyldisilazane, hexaphenyldisilazane, trisilazane, cyclotrisilazane, and 1,1,3,3,5,5-hexamethylcyclotrisilazane.

[0022] Examples of titanate coupling agents include tetrakis(2-ethylhexyloxy)titanium, titanium-i-propoxyoctylene glycolate, di-i-propoxybis(acetylacetonate)titanium, propanedioxytitanium bis(ethylacetoacetate), tri-n-butoxytitanium monostearate, di-i-propoxytitanium distearate, butyl titanate dimer, titanium octylene glycolate, diisopropoxytitanium bis(triethanolamine), dihydroxytitanium bislactate, dihydroxybis(ammonium lactate)titanium, bis(dioctyl pyrophosphate)ethylene titanate, bis(dioctyl pyrophosphate)oxyacetate titanate, tri-n-butoxytitanium monostearate, and tetra-n-buty Examples include lutitanate, tetraisopropylbis(dioctylphosphite) titanate, tetraoctylbis(ditridecylphosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, isopropyltrioctanoyl titanate, isopropyltricumylphenyl titanate, isopropyltriisostearoyl titanate, isopropylisostearoyldiacrylic titanate, isopropyldimethacrylateisostearoyl titanate, isopropyltri(dioctylphosphate) titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyltris(dioctylpyrophosphate) titanate, and isopropyltri(N-amidoethyl / aminoethyl) titanate.

[0023] The amount of coupling agent (C) in the polyamide resin composition is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.8% by mass, and even more preferably 0.1 to 0.5% by mass. Furthermore, relative to talc (B), it is preferably 0.1 to 4.0% by mass, more preferably 0.2 to 2.0% by mass.

[0024] The fatty acid metal salt (D) is blended for the purpose of suppressing the aggregation of talc and expressing good appearance and physical properties. As the fatty acid metal salt (D), a metal salt of a fatty acid having 9 to 30 carbon atoms is preferable. For example, calcium stearate, magnesium stearate, zinc stearate, calcium behenate, magnesium behenate, zinc behenate, zinc montanate, calcium montanate, magnesium montanate, calcium melissate, magnesium melissate, zinc melissate, calcium cerotate, magnesium cerotate, zinc cerotate, calcium lignocerate, magnesium lignocerate, zinc lignocerate and the like can be mentioned. Among these metal salts, a calcium salt, magnesium salt or zinc salt of a fatty acid having 15 to 28 carbon atoms is preferable, and particularly calcium stearate, magnesium stearate, zinc stearate, calcium behenate, magnesium behenate, zinc behenate, zinc montanate, calcium montanate, magnesium montanate and the like are more preferable in terms of performance and ease of availability. These metal salts can be produced by a synthesis method (double decomposition method) in which a carboxylic acid compound and a metal hydroxide are reacted and then washed with water, dehydrated and dried, or a method in which they are directly reacted without using water (direct method).

[0025] The blending (content) amount of the fatty acid metal salt (D) in the polyamide resin composition is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, and still more preferably 0.1 to 1% by mass.

[0026] In the polyamide resin composition of the present invention, a crystalline polyamide resin (A) and talc (B) (preferably talc with an average primary particle size of 20 μm or less) are melt-kneaded in a ratio of 50 to 90% by mass of polyamide resin (A) and 9 to 49% by mass of talc (B), and it is necessary that the average secondary particle size of the talc (B) in the polyamide resin composition is greater than 30 μm. The average secondary particle size is preferably 35 μm or more, more preferably 40 μm or more. If the average secondary particle size is 30 μm or less, the appearance of the molded product will be poor, and shrinkage will easily occur during molding. The average secondary particle size of the talc (B) in the polyamide resin composition is preferably 60 μm or less, more preferably 50 μm or less, and even more preferably 45 μm or less.

[0027] Talc has a nucleating effect, and on the surface of talc in a polyamide resin composition, polyamide resin crystals begin to form at a higher temperature than the normal crystallization temperature. If the average secondary particle size of the dispersed phase consisting of component (B) is 30 μm or less, the total surface area of ​​talc increases, making the nucleating effect of talc more pronounced and increasing the degree of crystallization, thus accelerating the solidification of the resin injected into the mold during molding. Because it is more likely to solidify before it adheres to the mold, the mold transferability decreases, the appearance of the molded product deteriorates, and at the same time, because it solidifies before the holding pressure takes effect, it is thought that shrinkage is more likely to occur.

[0028] The method for measuring the average particle size of secondary particles involves observing molded products obtained by injection molding a polyamide resin composition using a scanning electron microscope (SEM) at 500x magnification. The maximum lengths of 500 secondary particles with a maximum length greater than the average particle size of the primary talc (B) particles are measured, and the average of the maximum lengths of the 100 largest secondary particles is calculated.

[0029] In addition to the above, the polyamide resin composition of the present invention may optionally contain, to the extent known, light or heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, plasticizers, lubricants, crystal nucleating agents, mold release agents, antistatic agents, halogenated flame retardants and antimony trioxide combinations, various phosphoric acid-based flame retardants, melamine-based flame retardants, inorganic pigments, organic pigments, dyes, or other polymers.

[0030] Examples of stabilizers include organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, as well as heat stabilizers, light stabilizers such as hindered amine, benzophenone, and imidazole types, as well as ultraviolet absorbers, metal deactivators, and copper compounds. Examples of copper compounds include copper salts of organic carboxylic acids such as cuprous chloride, cuprous bromide, cuprous iodide, cupric chloride, cupric bromide, cupric iodide, cupric phosphate, cupric pyrophosphate, copper sulfide, copper nitrate, and copper acetate. Furthermore, it is preferable to include alkali metal halide compounds as components other than copper compounds. Examples of alkali metal halide compounds include lithium chloride, lithium bromide, lithium iodide, sodium fluoride, sodium chloride, sodium bromide, sodium iodide, potassium fluoride, potassium chloride, potassium bromide, and potassium iodide. These additives may be used individually or in combination. The amount of stabilizer to add should be selected to the optimal amount, but it is possible to add up to 5 parts by mass per 100 parts by mass of polyamide resin (A).

[0031] As flame retardants, a combination of halogenated flame retardants and flame retardant additives is preferable. Preferred halogenated flame retardants include brominated polystyrene, brominated polyphenylene ether, brominated bisphenol-type epoxy polymer, brominated styrene maleic anhydride polymer, brominated epoxy resin, brominated phenoxy resin, decabromodiphenyl ether, decabromoviphenyl, brominated polycarbonate, perchlorocyclopentadecane, and brominated crosslinked aromatic polymers. Examples of flame retardant additives include antimony trioxide, antimony pentoxide, sodium antimonate, zinc stagnate, zinc borate, layered silicates such as montmorillonite, fluorinated polymers, and silicones. In particular, from the standpoint of thermal stability, a combination of dibrom polystyrene as the halogenated flame retardant and any of antimony trioxide, sodium antimonate, or zinc stagnate as the flame retardant additive is preferred. Examples of non-halogenated flame retardants include melamine cyanurate, red phosphorus, metal salts of phosphinic acid, and nitrogen-containing phosphate compounds. In particular, a combination of a phosphinate metal salt and a nitrogen-containing phosphate compound is preferred. The nitrogen-containing phosphate compound includes melamine or a reactive compound of melamine condensates such as melam or melon, and polyphosphate, or mixtures thereof. As for other flame retardants and flame retardant aids, when using these flame retardants, the addition of hydrotalcite compounds or alkali compounds is preferred to prevent metal corrosion of molds, etc. The amount of flame retardant to be added should be selected to the optimal amount, but it is possible to add up to 20 parts by mass per 100 parts by mass of polyamide resin (A).

[0032] The polyamide resin composition of the present invention preferably contains 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, of the total of polyamide resin (A), talc (B), coupling agent (C), and fatty acid metal salt (D) (the coupling agent (C) and fatty acid metal salt (D) are optional components).

[0033] The manufacturing apparatus for producing the polyamide resin composition of the present invention is not particularly limited as long as it can melt-knead the polyamide resin and talc. It can be used with any single-screw extruder, twin-screw extruder, kneader, Banbury mixer, roll, etc., which are well known to those skilled in the art and capable of melt-kneading, but it is preferable to use a twin-screw extruder.

[0034] The screws of a twin-screw extruder are used in appropriate combinations of full-flight screws, reverse full-flight screws, orthogonal kneading discs, progressive kneading discs, and reverse kneading discs. In the present invention, it is preferable to incorporate a progressive kneading disc as the screw configuration for the plasticizing region.

[0035] Furthermore, it is preferable that the ratio L / D, which is the ratio of the screw length L (mm) to the screw diameter D (mm), satisfies the relationship 10 ≤ (L / D) ≤ 100. If there are no other operational problems, a smaller L / D is preferable from the viewpoint of fine dispersion of talc. Note that if it exceeds 100, the mechanical strength of the resin composition tends to decrease due to thermal degradation.

[0036] Furthermore, the melting temperature of the resin composition during melt mixing is preferably 180 to 330°C, and more preferably 200 to 300°C. If the melting temperature is below 180°C, melting will be insufficient, and a large amount of unmelted gel is likely to occur. Conversely, if it exceeds 330°C, the resin composition is prone to thermal degradation.

[0037] The screw rotation speed N during melt mixing is preferably 100 to 1,500 rpm, and more preferably 150 to 1,000 rpm. If the screw rotation speed is less than 100 rpm, the talc tends to penetrate the resin poorly, and conversely, if it exceeds 1,500 rpm, the resin is prone to deterioration due to shear heat. The discharge rate Q is preferably 5 to 3,000 kg / hr, and more preferably 10 to 2,000 kg / hr. If the discharge rate is less than 5 kg / hr, the dispersibility of the talc tends to decrease, and even if it exceeds 2,000 kg / hr, the dispersibility tends to decrease due to the re-aggregation of the talc.

[0038] Furthermore, the ratio Q / N, which is the ratio of the discharge rate Q (unit: kg / hr) to the screw rotation speed N (unit: rpm) during melt-kneading, is preferably 0.01 ≤ (Q / N) ≤ 1, and more preferably 0.05 ≤ (Q / N) ≤ 0.9. If it is less than 0.01, the mechanical strength of the resin composition tends to decrease due to thermal degradation. Also, if it exceeds 1, the conveying force becomes insufficient, and talc is more likely to be ejected.

[0039] Furthermore, talc, which tends to have poor penetration into polyamide resin during extrusion, can be fed through the side port of the twin-screw extruder. By feeding it through the side port, the penetration of talc into the resin is stable even when the screw is rotating at high speeds. In addition, because it comes into contact with the molten resin, the shear between the talc and the resin pellets is reduced, as is the case with pre-filling, making it less likely for the talc to be finely ground to less than 30 μm, and making it easier to stably obtain an average secondary particle size larger than 30 μm.

[0040] In the method for producing the polyamide resin composition of the present invention, it is preferable to melt-knead a crystalline polyamide resin (A) and talc having a primary particle size of 1 to 20 μm in a predetermined ratio, and to supply a portion or all of the talc from the side port of a twin-screw extruder. When supplying a portion of the talc from the side port, it is preferable to supply an amount of 50% or more by mass and less than 100% by mass of the total talc amount from the side port.

[0041] Furthermore, component (C) may be added simultaneously with the other raw material components, but it may also be added after being attached to the talc beforehand.

[0042] Furthermore, in order to remove gaseous components associated with the talc during melt-kneading, it is preferable to perform vacuum degassing in the melt-kneading section after plasticization is complete. [Examples]

[0043] The present invention will now be specifically described using examples and comparative examples, but the present invention is not limited to these.

[0044] The characteristics and physical properties shown in the following examples and comparative examples were measured using the test methods described below.

[0045] 1) Average particle size of talc secondary particles: Cross-sectional sections were prepared using a microtome from test pieces prepared according to 4) below, platinum sputtering was performed, and the sections were observed at 500x magnification using a scanning electron microscope (SEM). The maximum lengths of 500 secondary particles with a maximum length greater than the average particle size of the primary talc particles were measured, and the average of the maximum lengths of the 100 largest secondary particles was calculated to determine the average particle size of the secondary particles.

[0046] 2) Bending deflection: Measured in accordance with JIS K 7171:2016.

[0047] 3) Charpy impact strength: Measured in accordance with ISO 179 / leA (with notch).

[0048] 4) Appearance evaluation of molded product: Using a Toshiba Machine EC-100 injection molding machine, the cylinder temperature was set to the melting point of the polyamide resin + 20°C, and the mold temperature to 90°C. Test pieces measuring 100 mm in length, 100 mm in width, and 2 mm in thickness were produced by injection molding. The appearance of these test pieces was evaluated visually. ◎: There is no lifting or sink marks of the reinforcing material throughout the molded product. ○: There is slight lifting or shrinkage of the reinforcing material near the gate and at the end. △: Minor chipping is visible in the molded product. ×: The entire molded product has a large amount of lifting or sink marks from the reinforcing material.

[0049] 5) Operational stability: Operational stability during melting and mixing was evaluated according to the following criteria. ◎: Continuous operation is possible without talc being ejected from the inlet or vent. △: A small amount of talc may leak from the inlet or vent. ×: A large amount of talc is ejected from the inlet and vent, making continuous operation impossible.

[0050] The raw materials used in the examples and comparative examples of the present invention are as follows. The relative viscosity (RV) of the polyamide resin was measured by dissolving 0.25 g of polyamide resin in 25 ml of 96% sulfuric acid, placing 10 ml of this solution in an Ostwald viscosity tube, and setting it at 20°C. (A11) Polyamide 6: Toyobo's "Gramide T-840" (RV2.2, melting point 223℃) (A12) Polyamide 6: Ube Industries "1013B" (RV2.5, melting point 224℃) (A13) Polyamide 6: Toyobo "T-820" (RV3.1, melting point 225℃) (B1) Talc: "KST-W" manufactured by Katsumitsuyama Mining Co., Ltd. (average particle size 7 μm, apparent specific gravity 0.4) (B2) Talc: Fukuoka Talc Industry Co., Ltd. "FU-51" (average particle size 13 μm, apparent specific gravity 0.3) (B3) Talc: Hayashi Chemical Co., Ltd. "KHP-400B" (average particle size 19 μm, apparent specific gravity 1.0) (C) Silane coupling agent: Shin-Etsu Chemical Co., Ltd. "KBE-903" (3-aminopropyltriethoxysilane) (D1) Fatty acid metal salt: "NP-1500" (magnesium stearate) manufactured by Tannan Chemical Co., Ltd. (D2) Fatty acid metal salt: "CS-8CP" (calcium montanate) manufactured by Nitto Chemical Industries, Ltd. (E) Stabilizer: Potassium iodide manufactured by Mitsui Chemicals

[0051] Example 1 To achieve the composition shown in Table 1, all raw materials except talc were pre-mixed and fed from the main feed, while the talc was supplied separately from the side feed to a twin-screw extruder (TEX54αII, manufactured by Japan Steel Works, Ltd.) with an L / D ratio of 45 for melt-kneading. After being drawn from the die in strand form, the mixture was cooled and solidified in a water bath, and then cut in a pelletizer to obtain polyamide resin composition pellets. The extruder barrel temperature was set to 260°C, and the screw rotation speed, discharge rate, and Q / N were set to the manufacturing conditions shown in Table 1. The obtained pellets were dried in a hot-air dryer until the moisture content was 0.05% or less, and then various properties were evaluated. The evaluation results are shown in Table 1.

[0052] Comparative Example 1 The raw materials were pre-mixed to achieve the composition shown in Table 1 and supplied from the original feed to a twin-screw extruder (TEX54αII, manufactured by Japan Steel Works, Ltd.) with an L / D ratio of 45 for melt-kneading. After being drawn from the die in strand form, the mixture was cooled and solidified in a water bath, and then cut with a pelletizer to obtain polyamide resin composition pellets. The extruder barrel temperature was set to 260°C, and the screw rotation speed, discharge rate, and Q / N were set to the manufacturing conditions shown in Table 1. The obtained pellets were dried in a hot-air dryer until the moisture content was 0.05% or less, and then various properties were evaluated. The evaluation results are shown in Table 1.

[0053] Examples 2-8, Comparative Example 2 A portion of the talc was pre-mixed with the other raw materials and supplied from the original feed. Pellets were prepared and evaluated in the same manner as in Example 1, except that the manufacturing conditions were set to those shown in Table 1.

[0054] [Table 1]

[0055] The results in Table 1 show that when polyamide resin and talc are included in predetermined amounts, and the average secondary particle size of the talc is within a predetermined range, a polyamide resin composition with excellent molded appearance without reinforcing material lifting or shrinkage can be obtained. Furthermore, it exhibits excellent operational stability without talc ejection during melt kneading. [Industrial applicability]

[0056] Molded articles made from the polyamide composition of the present invention have an excellent appearance free from reinforcing material lifting or sink marks, and can be applied to a wide range of applications. They are particularly suitable for automotive interior parts such as consoles and cup holders, where a molded article appearance free from reinforcing material lifting or sink marks is important.

Claims

1. A polyamide resin composition containing 50 to 90% by mass of crystalline polyamide resin (A) and 9 to 49% by mass of talc (B), wherein the average particle size of the secondary particles of talc (B) in the polyamide resin composition is greater than 30 μm and 50 μm or less. It further contains stabilizers, A polyamide resin composition characterized in that the crystalline polyamide resin (A) contains polyamide 6 (except in cases where the polyamide resin composition contains rosin with an acid value of 60 mg KOH / g or more).

2. The polyamide resin composition according to claim 1, wherein the polyamide resin composition further contains a coupling agent (C) and a fatty acid metal salt (D).

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