JP2013203869A - Polyamide resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide resin composition capable of providing a molded product improved in surface appearance such as sink mark or weld line and enhanced in strength.SOLUTION: A polyamide resin composition contains: 3-30 pts.mass of a spherical filler (C), relative to 100 pts.mass in total of 30-80 mass% of a polyamide resin (A) and 20-70 mass% of glass fibers (B). The polyamide resin (A) includes a crystalline polyamide resin (a1) and an amorphous polyamide resin (a2), with (a2)/{(a1)+(a2)}=0.1-0.4. The spherical filler (C) satisfies the following expressions (1) and (2). D90/D10<3(1)D50/D50>0.5(2), wherein D10, D50, D90are cumulative particle sizes of 10%, 50%, 90% from the minor particle side in volume particle size distribution respectively, and D50is a number average particle size.

Description

  The present invention relates to a polyamide resin composition having excellent surface appearance and increased weld strength.

  With recent miniaturization of office machines and electronic devices, the housing and chassis are becoming thinner. In order to satisfy practical strength even if it is thin, use a resin composition reinforced with glass fiber, etc., arrange many ribs and bosses on the molded body, partially thicken, etc. Ingenuity has been made. On the other hand, even if it is thin, in order to improve moldability, the design which increases the number of gate points is made. Increasing the number of gates complicates the flow of resin in the mold, causing sink marks and weld lines to become conspicuous on the surface of the molded body, and the problem of impairing the appearance has become apparent. Furthermore, the use of a resin composition reinforced with glass fiber or the like has caused problems such as the weld line rising.

  In order to improve such problems, a method of using flat glass fibers having an irregular cross section as an inorganic filler for warping deformation has been proposed (Patent Document 1). Although warp deformation can be suppressed, it was not sufficient because the weld line bulge, which is likely to occur when flat glass fibers are used, the weld strength is greatly reduced, and the bosses and ribs are sinked. .

  In addition, a method has been proposed in which a crystalline glass and an amorphous polyamide or a microcrystalline polyamide are combined and a flat glass fiber having an irregular cross section is used as an inorganic filler (Patent Document 2). Since crystallinity is suppressed by combining amorphous polyamide or microcrystalline polyamide, the rise of sink marks and weld lines is improved, but it is still insufficient. Furthermore, in addition to Patent Document 2, a method of adding a spherical filler has been proposed (Patent Documents 3 and 4). Addition of spherical fillers improves sink marks and weld line excitement, but it is still insufficient.

Japanese Patent Laid-Open No. 10-2119026 JP 2008-163340 A JP 2009-7482 A JP 2010-260889 A

  An object of the present invention is to provide a polyamide resin composition having improved surface appearance such as sink marks and weld lines of a molded body and increased weld strength.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the gist of the present invention is as follows.
(1) Polyamide resin comprising 3 to 30 parts by mass of spherical filler (C) with respect to 100 parts by mass in total of 30 to 80% by mass of polyamide resin (A) and 20 to 70% by mass of glass fiber (B) In the composition, the polyamide resin (A) is a crystalline polyamide resin (a1) and an amorphous polyamide resin (a2), (a2) / {(a1) + (a2)} = 0.1 to 0.4 And the spherical filler (C) satisfies the following formulas (1) and (2).
D90 _V / D10 _V <3 (1)
D50 _N / D50 _V > 0.5 (2)
However, D10 _V, D50 _{V, and} D90 _V are particle sizes that become 10%, 50%, and 90% cumulative from the small particle size side, respectively, in the volume particle size distribution. D50 _N is the number average particle size.
(2) The polyamide resin composition according to (1), wherein the glass fiber (B) is a flat glass fiber having a flat cross section having a major axis / minor axis ratio of 1.5 to 10.
(3) The polyamide resin composition according to (1) or (2), wherein the crystalline polyamide resin (a1) is any one polyamide selected from nylon 6 and nylon 66.
(4) The polyamide resin composition of (1) to (3), wherein the spherical filler (C) is a glass bead.
(5) A resin molded product obtained by molding the polyamide resin composition of (1) to (4).

  ADVANTAGE OF THE INVENTION According to this invention, the polyamide resin composition which improved the surface external appearances, such as the sink mark and weld line of a molded object, and raised weld strength is obtained.

It is the schematic which shows the molded object for performing external appearance evaluation of the polyamide resin composition of this invention.

Hereinafter, the present invention will be described in detail.
The polyamide resin composition of the present invention is a polyamide resin composition comprising a polyamide resin (A), glass fibers (B) and spherical fillers (C).

  The crystalline polyamide resin (a1) in the polyamide resin (A) is polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polyhexamethylene sebaca Mido (nylon 610), polyhexamethylene dodecamide (nylon 612), polyundecamethylene adipamide (nylon 116), polybis (4-aminocyclohexyl) methane dodecamide (nylon PACM12), polybis (3-methyl-4) Aminocyclohexyl) methane dodecamide (nylon dimethyl PACM12), polydecamethylene terephthalamide (nylon 10T), polyundecamethylene terephthalamide (nylon 11T), polyundecamethylene hexahydroterephthalamide (nai) 11T (H)), polyundecamide (nylon 11), polydodecamide (nylon 12), polytrimethylhexamethylene terephthalamide (nylon TMDT), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalate / isophthalamide (nylon 6T) / 6I), polymetaxylylene adipamide (nylon MXD6), and copolymers and mixtures thereof. Of these, nylon 6, nylon 66, copolymerized polyamides thereof, and mixed polyamides are particularly preferable. These crystalline polyamide resins preferably have a melting point of 160 to 320 ° C, more preferably 180 to 300 ° C, from the viewpoint of improving the heat resistance of the obtained polyamide resin composition.

  The amorphous polyamide resin (a2) in the polyamide resin (A) is a polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane, terephthalic acid / 2,2, 4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine polycondensate, isophthalic acid / bis (3-methyl-4-aminocyclohexyl) methane / ω-laurolactam polycondensate, isophthalic acid / Polycondensate of terephthalic acid / hexamethylenediamine, polycondensate of isophthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine, isophthalic acid / terephthalic acid / 2,2, 4-trimethylhexamethylenediamine / 2,4,4-trimethylhexa Polycondensate of ethylenediamine, a polycondensate of isophthalic acid / bis (3-methyl-4-aminocyclohexyl) methane / .omega.-laurolactam can be cited. Also included are those in which the benzene ring of the terephthalic acid component and / or isophthalic acid component constituting these polycondensates is substituted with an alkyl group or a halogen atom. Furthermore, two or more of these amorphous polyamide resins can be used in combination. Preferably, a polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine, a polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane, or terephthalic acid / 2, Polycondensate of 2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine or polycondensation of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane And a mixture of terephthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine polycondensate. Particularly preferred is a polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine, a polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane, or a mixture thereof. By blending the amorphous polyamide resin (a2) with the polyamide resin composition of the present invention, it is possible to improve the surface appearance such as sink marks and welds of the resulting molded article, and to improve the bending elastic modulus of the weld part. be able to.

  These amorphous polyamide resins (a2) preferably have a glass transition temperature of 80 to 200 ° C. from the viewpoint of improving the heat resistance of the resulting polyamide resin composition and improving processability. More preferably, it is 170 degreeC. A glass transition temperature of less than 80 ° C. is not preferable because when the polyamide resin composition is molded, it is solidified to cause a defective mold release or a longer molding cycle. When the glass transition temperature exceeds 200 ° C., when the polyamide resin composition is molded, the solidification is too early, and appearance defects such as sink marks and glass floating tend to occur, and the melt viscosity at the time of kneading increases. Uniform kneading becomes difficult, which is not preferable.

In the crystalline polyamide resin (a1), the crystallinity is a calorie value measured by a differential scanning calorimeter (DSC) at a heating rate of 16 ° C./min in a nitrogen atmosphere at 1 cal / min. means greater than g.
In the amorphous polyamide resin (a2), the term “amorphous” means that the value of heat of fusion measured by a differential scanning calorimeter (DSC) at a rate of temperature increase of 16 ° C./min in a nitrogen atmosphere is 1 cal / g. It means the following.

  The mass ratio of the crystalline polyamide resin (a1) and the amorphous polyamide resin (a2) in the polyamide resin (A) is such that (a2) / {(a1) + (a2)} is 0.1 to 0.4. Must meet. When the inorganic filler (fibrous reinforcing material and plate-like silicate) is blended at a high concentration as in the present invention when it is less than 0.1, so-called glass is produced due to the shrinking action accompanying crystallization of the crystalline polyamide resin. It floats and the surface smoothness of the molded body cannot be improved. When it exceeds 0.4, when the inorganic filler is blended at a high concentration, the effect of suppressing the crystallinity of the amorphous polyamide resin becomes excessive, and the cooling time that can be taken out from the mold increases. Furthermore, while the surface smoothing action of the amorphous polyamide resin is increased, the mold surface must be heated at a temperature higher than the glass transition temperature of the amorphous polyamide resin used in order to sufficiently bring out the action. Don't be. Therefore, in injection molding or the like, the molding cycle is extended and productivity is deteriorated.

  The relative viscosity of the polyamide resin (A) in the present invention is not particularly limited, but the relative viscosity measured with 96 wt% concentrated sulfuric acid as a solvent at a temperature of 25 ° C. and a concentration of 1 g / dl is 1.8. Is preferably in the range of -2.5, more preferably 1.9-2.3, and even more preferably 1.9-2.1. When the relative viscosity is less than 1.8, the melt viscosity is low, and it becomes easy to cut at the time of taking the strand after melt-kneading, and the workability is lowered. If the relative viscosity is greater than 2.5, the melt viscosity is high, so that the fluidity during molding is poor and thin-wall molding becomes difficult. Even if the molding can be performed, the time until the resin is filled in the mold becomes long, so that the resin temperature at the flow front is lowered, that is, the resin bonding at the weld portion is deteriorated, and the weld strength is lowered. In addition, sink marks and weld lines may occur in the molded body, which may deteriorate the appearance. From the viewpoint of ensuring fluidity of the polyamide resin composition, transferability to the mold, appearance of the resulting molded product, and weld strength, it is possible to use a polyamide resin (A) having a relative viscosity of 1.9 to 2.3. preferable.

  Here, the weld is a characteristic phenomenon that occurs particularly when the resin is injection-molded, and is a defect in which a thin line is generated in a fused portion of the molten resin flow in the mold. If a mold is provided with a pin, a core, or the like in order to form a hollow portion or the like in the molded body, the molten resin wraps around the portion and then merges again to generate a weld line. In addition, when it is necessary to provide two or more gates, the generation of a weld line is inevitable.

  The occurrence of this weld becomes more remarkable when a large amount of inorganic filler such as glass fiber is blended. There is a risk that the appearance may be damaged or the mechanical characteristics may be significantly deteriorated due to poor fusion due to the occurrence of welds. In order to improve these defects, it is necessary to devise (1) increase the temperature of the molten resin and mold, (2) increase the injection pressure and speed, and change the position, number, size, etc. of the gate. It is. The weld strength indicates a mechanical property (for example, flexural modulus) of the weld portion.

  A well-known thing can be used for the glass fiber (B) in this invention. The glass fiber may be surface-treated with a coupling agent such as a silane coupling agent, a titanium coupling agent, or a zirconia coupling agent in order to improve adhesion and uniform dispersibility with the polyamide resin (A). . The coupling agent is contained in a known sizing agent and can be easily obtained by dipping and drying together with the sizing agent. Examples of the form of the glass fiber (B) include long fiber type roving, short fiber type chopped strand, and milled fiber.

  As the cross-sectional shape of the glass fiber (B), a circular, flat gourd type, eyebrows type, oval type, elliptical type, rectangular shape, or similar products thereof are used. In order to reduce the warpage peculiar to the polyamide molding which mix | blended the glass fiber, what is 1.5-10 of the major axis / minor axis ratio of the flat fiber cross section is used suitably, and 2.0-6. More preferred is 0. When the major axis / minor axis ratio is 1.5 or less, the effect of promoting the warping of the molded article is small, and when the ratio is 10 or more, it is difficult to produce glass fibers themselves. Here, the major axis / minor axis ratio of the fiber cross section is calculated from the major axis and minor axis measured with the microscope in the vertical direction of the cut cross section of the glass fiber, and is an average value of ten pieces.

1-15 mm is preferable and, as for the average fiber length of a glass fiber (B), 2-10 mm is more preferable. If the average fiber length is less than 1 mm, sufficient mechanical strength cannot be secured. 15mm
If it exceeds, the flow of the resin becomes worse at the time of resin molding and workability becomes worse. Here, the average fiber length refers to an average value of 20 pieces measured with a microscale as a reference when a glass fiber is observed with a microscope.

  The compounding quantity of a polyamide resin (A) and glass fiber (B) needs to be (A) / (B) = 30 / 70-80 / 20 (mass%), (A) / (B) = 35 / 65 to 75/25 (mass%) is preferable, and (A) / (B) = 40/60 to 70/30 (mass%) is more preferable. When the blending amount of the glass fiber (B) is less than 20% by mass, the bending elastic modulus of the obtained molded product is lowered, which is not preferable. When the blending amount of the glass fiber (B) exceeds 70% by mass, the flow characteristics are deteriorated, the strands cannot be taken out during the resin melt kneading, and the production of the polyamide resin composition is difficult.

  Examples of the spherical filler (C) in the present invention include glass beads, glass balloons, talc, barium sulfate, and the like, and the glass beads are highly effective in improving the surface appearance such as sink marks and weld lines of the resulting molded product. Can be preferably used. The surface of the spherical filler (C) may be pretreated with a coupling agent such as a silane coupling agent or a titanate coupling agent, or other surface treatment agent. The mechanical strength of the molded body obtained by performing such pretreatment can be further increased. These may be used alone or in combination of two or more.

The spherical filler (C) in the present invention needs to satisfy the following formulas (1) and (2).
D90 _V / D10 _V <3 (1)
D50 _N / D50 _V > 0.5 (2)
However, D10 _V, D50 _{V, and} D90 _V are particle sizes that become 10%, 50%, and 90% cumulative from the small particle size side, respectively, in the volume particle size distribution. D50 _V is a so-called volume average particle diameter. Further, D50 _N is the number average particle diameter.

Satisfying the above formula (1) indicates that there is a large distribution of spherical fillers having a large particle size in the volume average particle size distribution. When D90 _V / D10 _V is 3 or more, the smoothness of the surface of the molded body of the polyamide resin composition is not impaired, and it becomes difficult to improve sink marks and welds.

By satisfying the above formula (2), the smoothness of the surface of the molded body of the polyamide resin composition can be improved. When D50 _N / D50 _V is less than 0.5, it becomes difficult to obtain a smoothness of the surface of the molded product.

The volume average particle diameter (D50 _V ) of the spherical filler (C) is preferably 5 to 100 μm, and more preferably 5 to 50 μm. If D50 _V is less than 5 μm, the improvement level of appearance problems such as sink marks and weld lines tends to be small, and if it exceeds 100 μm, the surface of the molded product becomes a textured surface and smoothness cannot be obtained. .

  In general, when the molded body is thin, glass fibers are easily oriented in the flow direction during molding, and shrinkage in the thickness direction is likely to increase. Therefore, when the thickness is thin, appearance problems such as sink marks are likely to occur. By adding the spherical filler (C), shrinkage in the thickness direction can be suppressed, and sink marks at the ribs and boss portions and the rise of the weld line can be suppressed. Further, if it is within the range of the above formula (1), the shrinkage in the thickness direction is further reduced, so that the appearance defect is drastically reduced, and the degree of freedom in design is greatly improved.

  The spherical filler (C) needs to be contained in an amount of 3 to 30 parts by mass, preferably 4 to 25 parts by mass, and 5 to 20 parts by mass with respect to 100 parts by mass in total of the polyamide resin (A) and the glass fiber (B). More preferred. If the content of the spherical filler (C) is less than 3 parts by mass, the effect of improving the surface appearance, particularly sink marks, is small, and if it exceeds 30 parts by mass, the bending elastic modulus of the welded part of the molded product tends to decrease and becomes brittle. Absent.

  The polyamide resin composition of the present invention may contain other additives as necessary. These additives include silica, fine glass powder, kaolin, talc, titanium oxide, calcium carbonate, alumina and other powders, known antistatic agents, colorants, lubricants, mold release agents, nucleating agents, flame retardants And impact resistance improvers.

  The method for producing the polyamide resin composition of the present invention is preferably a melt-kneading method using a twin screw extruder. Specifically, a predetermined amount of polyamide resin is supplied from the feed hole (top feed) located on the most upstream side of the twin-screw extruder, and when the polyamide resin reaches a molten state, a predetermined amount of glass fiber is placed on the side. It is obtained by feeding from a feed, forming into a strand shape with a spinning hole attached to the downstream end of the extruder, and then cooling and cutting into a pellet shape.

  Examples of the method for molding the polyamide resin composition of the present invention include known molding methods such as injection molding, extrusion molding, and blow molding. Among them, the injection molding method can be suitably used for producing a molded product that takes advantage of sufficient mechanical properties, low warpage, and weld strength of the polyamide resin composition.

  When molding by the injection molding method, the cylinder temperature of the injection molding machine is preferably set to (melting point + 20 ° C.) to (melting point + 70 ° C.) in order to plasticize the polyamide resin composition. In order to balance deterioration, (melting point + 30 ° C.) to (melting point + 60 ° C.) is more preferable.

  The mold temperature in the injection molding method is preferably set slightly higher than the glass transition temperature of the polyamide resin composition, and the resin heated and plasticized by the cylinder is injected, filled in the mold and cooled. In order to suppress the rapid cooling of the resin and the progress of crystallization, improve the transfer of the mold (clean appearance), and improve the dimensional accuracy of the resulting molded product (suppress the shrinkage of the molded product due to crystallization). Useful.

  The mold temperature control is also useful for suppressing the weld line from entering the molded article by setting it slightly higher than the glass transition temperature of the polyamide resin composition. As with mold transfer, slowing down the resin cooling ensures sufficient resin flow, suppresses the resin temperature drop at the resin flow front, and more fully joins the resin at the weld. I can do it.

  The polyamide resin composition of the present invention can be used in various molded object applications such as electric / electronic parts, automobile parts, building materials, etc. by taking advantage of sufficient mechanical properties, low warpage and weld strength. Among them, since the effect of improving the surface appearance such as sink marks and weld lines of the molded body is high, it can be suitably used for thin molded bodies such as housings and chassis of electronic devices.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the raw material used for the Example and the comparative example and the physical property measuring method are as follows.

1. Measurement Method (1) Relative Viscosity of Polyamide Resin and Polyamide Resin Composition In 96 mass% sulfuric acid, the polyamide resin is dissolved so that the concentration of the dried pellets of the polyamide resin is 1 g / dl. After separating by filtration, it was used for measurement. The measurement was performed at 25 ° C. using an Ubbelohde viscometer. The polyamide resin composition was also measured in the same manner after correcting the glass fiber and the spherical filler.

(2) Measurement of spherical filler particle size distribution Using a Multisizer 4 manufactured by BECKMAN COULTER, the particle size distribution of spherical fillers of 5.6 μm to 168 μm was measured by the Coulter principle using electrical resistance.

(3) Flexural modulus A test piece having a length of 150 mm, a width of 10 mm, and a thickness of 3 mm was injection-molded with a one-point gate and measured at 23 ° C. in accordance with ASTM D790.
The flexural modulus is a scale indicating the degree of deflection with respect to stress, and the higher the value, the better. From the viewpoint of suppressing deformation due to external force in the case of a thin molded body, the amount of glass fiber is 20% by mass. 6 GPa, preferably 6.5 GPa or more. When the blending amount of the glass fiber is 50% by mass, 15 GPa, preferably 15.5 GPa or more is required.

(4) Bending elastic modulus of weld part A test piece having a length of 150 mm, a width of 10 mm, and a thickness of 3 mm was injection-molded with a two-point gate from both ends. Similarly, it measured at 23 degreeC based on ASTMD790. In preparing the test piece, the cylinder temperature of the injection molding machine is 270 ° C. for polyamide 6, 290 ° C. for polyamide 66, the mold temperature is 80 ° C. for polyamide 6 and the polyamide 66 In this case, the cooling time was 100 seconds and 20 seconds. The weld line entered the line so as to cross the test piece just in the center of the test piece, but those having an abnormal appearance were not subjected to the test and were excluded.
The bending elastic modulus of the weld portion is a measure that indicates the degree of deflection with respect to the stress of the weld portion. If the bending elastic modulus of the weld part is not sufficiently high, when it is put to practical use as a molded body, the weld part may break due to repeated stress load. It is desired that the bending elastic modulus of the weld part is sufficiently high as well as an appearance problem.
The retention rate of the bending elastic modulus was calculated by taking the ratio of (3) bending elastic modulus and (4) bending elastic modulus of the weld part according to the following formula.
Retention rate of flexural modulus (%) = {(flexural modulus of weld portion) / (flexural modulus)} × 100
The retention rate of the flexural modulus is 100% when there is no decrease in the flexural modulus. In general, a certain degree of decrease in flexural modulus occurs, but the retention rate of flexural modulus is 70% or more, preferably 75% or more.

(5) Fluidity A dedicated mold with one-point gate on one side that can collect a spiral shaped product with a thickness of 1 mm and a width of 20 mm is used. The injection molding machine is S2000i-B manufactured by FANUC, and the cylinder temperature is polyamide. In the case of 6, 270 ° C., in the case of polyamide 66, 290 ° C., the mold temperature is 80 ° C. in the case of polyamide 6, 100 ° C. in the case of polyamide 66, injection pressure 100 MPa, speed 70 mm / s, injection time 5 Molding was performed under the condition of seconds. The flow length of 120 mm or more is a practically problematic range, and is preferably 150 mm or more.

(6) Surface appearance of molded body A molded body (FIG. 1) having a thickness of 0.8 mm that imitates a mobile phone casing was molded. At both ends of the molded body, there are ribs having a width of 1 mm, a length of 10 mm, and a height of 0.5 mm. The injection molding machine is S2000i-B manufactured by FANUC, the cylinder temperature is 270 ° C. for polyamide 6, 290 ° C. for polyamide 66, the mold temperature is 80 ° C. for polyamide 6 and polyamide 66 In this case, it was molded at 100 ° C.

(6-1) Sink evaluation The part which attached the rib of the molded object was observed from the back side of the molded object, and the difference in the surface height of the part of a rib and a part without a rib was measured. If the difference in surface height was less than 10 μm, it was judged as acceptable (◎), even if it was 10-20 μm, it was acceptable (◯), and if it was larger than 20 μm, it was judged as unacceptable (x).

(6-2) Weld evaluation Welds formed at the resin joining portion of the molded body were evaluated. When the resin swelled at the resin junction (weld), the difference in surface height between the welded portion and the unwelded portion was measured. If the difference in surface height was less than 10 μm (◎), 10-20 μm (◯), and greater than 20 μm (×). ○ and ◎ were accepted.

2. Raw material (1) Polyamide resin (i) Crystalline polyamide resin / Polyamide (a1-1): Nylon 6 (A1012 manufactured by Unitika), relative viscosity 1.9
Polyamide (a1-2): Nylon 6 (A1015 manufactured by Unitika), relative viscosity 2.1
Polyamide (a1-3): nylon 6 (A1030BRL manufactured by Unitika), relative viscosity 2.5
Polyamide (a1-4): Nylon 6 (A1030BRF-BA manufactured by Unitika), relative viscosity 3.0
Polyamide (a1-5): Nylon 66 (Leona 1200 manufactured by Asahi Kasei Chemicals Corporation), relative viscosity 2.3
(Ii) Amorphous polyamide resin / polyamide (a2-1): isophthalic acid / terephthalic acid / hexamethylenediamine polycondensate (X21 manufactured by Mitsubishi Engineering Plastics)
Polyamide (a2-2): polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4aminocyclohexyl) methane (CX-3000 manufactured by Unitika)

(2) Glass fiber / Glass fiber (B-1): Flat glass fiber (CSG3PA820S manufactured by Nittobo Co., Ltd.) having an elliptical cross section with a major / minor diameter ratio of 4, major axis 28 μm, minor diameter 7 μm, fiber length 3 mm, silane System surface treatment glass fiber (B-2): Glass fiber having a circular cross section (T262H manufactured by Nippon Electric Glass Co., Ltd.), average fiber diameter 10 μm, fiber length 3 mm

(3) Spherical filler / spherical filler (C-1): glass beads (UB-02EA manufactured by Union),
D10 _V ; 13.82 μm, D50 _V ; 23.22 μm, D90 _V ; 34.58 μm, D50 _N ; 13.4 μm, D90 _V / D10 _V = 2.50, D50 _N / D50 _V = 0.58
-Spherical filler (C-2): Glass beads (EGB731B manufactured by Potters Barotini),
D10 _V ; 11.06 μm, D50 _V ; 21.33 μm, D90 _V ; 34.72 μm, D50 _N ; 9.7 μm, D90 _V / D10 _V = 3.14, D50 _N / D50 _V = 0.45

Example 1
Crystalline polyamide resin (a1-1), amorphous polyamide resin (a2-1), and spherical filler (C-1) are mixed together and charged from the main hopper of a twin screw extruder (TEM37 manufactured by Toshiba Machine). The glass fibers were side-fed and melt kneaded. The compounding is 100 parts by mass in total of the crystalline polyamide resin (a1-1), the amorphous polyamide resin (a2-1), and the glass fiber (B-1) (mass of a1-1 / a2-1 / B-1). The spherical filler (C-1) was 5.5 parts by mass with respect to the ratio of 42.5 / 7.5 / 50). The melt kneading was performed under conditions of a cylinder set temperature of 270 ° C., a screw rotation of 200 rpm, and a discharge rate of 35 kg / h. After melt-kneading, the polyamide resin composition was taken out into a strand shape, cooled, and cut with a pelletizer to obtain polyamide resin composition pellets. The relative viscosity of the polyamide resin composition was measured using the obtained pellets. Similarly, the relative viscosity of the polyamide resin before melt kneading was measured. The results are shown in Table 1.

  Next, the obtained polyamide resin composition pellets were injection-molded under conditions of a cylinder temperature of 270 ° C. and a mold temperature of 80 ° C. using an injection molding machine (S2000i-B manufactured by FANUC) to obtain a test piece. Each evaluation was performed using the obtained test piece. The results are shown in Table 1.

Examples 2-11
A test piece was prepared in the same manner as in Example 1 except that the composition shown in Table 1 was used, and each evaluation was performed. The results are shown in Table 1. The barrel temperature setting of the extruder was 270 ° C. for polyamide 6 and 290 ° C. for polyamide 66. The cylinder temperature of the injection molding machine was 270 ° C. for polyamide 6, 290 ° C. for polyamide 66, 80 ° C. when the mold temperature was polyamide 6, and 100 ° C. for polyamide 66.

Comparative Examples 1-10
A test piece was prepared in the same manner as in Example 1 except that the formulation shown in Table 2 was used, and each evaluation was performed. The results are shown in Table 2.

  In Examples 1 to 11, in order to satisfy the requirements of the present invention, sink marks and weld lines of the molded body were improved, and the weld strength could be increased.

  Since Comparative Examples 1-4 did not use a predetermined spherical filler, both sink and weld were inferior.

  Comparative Example 5 was inferior in sink and weld because no spherical filler was added.

  In Comparative Example 6, sink marks were inferior because the blending amount of the spherical filler was too small.

  In Comparative Example 7, since the blending amount of the spherical filler was excessive, the bending elastic modulus retention rate of the weld portion was inferior.

  In Comparative Example 8, since the amorphous polyamide resin was not added, the bending elastic modulus retention rate, sink mark and weld of the weld part were inferior.

  In Comparative Example 9, since the blending amount of the glass fiber was too small, the flexural modulus was inferior.

In Comparative Example 10, since the blending amount of the glass fiber was excessive, the flowability was poor at the time of melt-kneading, and the strand could not be taken out, so the polyamide resin composition pellets could not be obtained.

Claims (5)

A polyamide resin composition comprising 3 to 30 parts by mass of a spherical filler (C) with respect to 100 parts by mass in total of 30 to 80% by mass of polyamide resin (A) and 20 to 70% by mass of glass fiber (B). The polyamide resin (A) includes a crystalline polyamide resin (a1) and an amorphous polyamide resin (a2), and (a2) / {(a1) + (a2)} = 0.1 to 0.4 A polyamide resin composition, wherein the spherical filler (C) satisfies the following formulas (1) and (2):
D90 _V / D10 _V <3 (1)
D50 _N / D50 _V > 0.5 (2)
However, D10 _V, D50 _{V, and} D90 _V are particle sizes that become 10%, 50%, and 90% cumulative from the small particle size side, respectively, in the volume particle size distribution. D50 _N is the number average particle size.   The polyamide resin composition according to claim 1, wherein the glass fiber (B) is a flat glass fiber having a flat cross section having a major axis / minor axis ratio of 1.5 to 10.   The polyamide resin composition according to claim 1 or 2, wherein the crystalline polyamide resin (a1) is any one polyamide selected from nylon 6 and nylon 66.   The polyamide resin composition according to any one of claims 1 to 3, wherein the spherical filler (C) is a glass bead. The resin molding formed by shape | molding the polyamide resin composition in any one of Claims 1-4.