Pellet, method for producing pellet, molded article, and gear

Abstract

This pellet comprises a semi-aromatic polyamide and glass fibers, wherein: the semi-aromatic polyamide has a structural unit represented by formula (1); and in a cross-section at the center in the MD direction of a specimen of the pellet obtained under the following molding conditions, the coefficient of variation of the distance between centroids of the glass fibers is 0.570 or less. (Molding conditions) [Specimen] Specimen type A prescribed in ISO 3167:93. [Injection molding conditions] Barrel temperature: 330°C-350°C, mold temperature: 120°C, back pressure: 7 MPa, screw rotation speed: 100 rpm, injection pressure: 70 MPa, injection speed: 26 mm / s, injection time: 2 seconds, holding pressure: 50 MPa, cooling time: 20 seconds, filling time: 2 seconds [Formula 1] [Ar1: a phenylene group or a naphthylene group, and p: an integer of 4-12]

Description

Pellets, pellet manufacturing method, compact and gear

[0001] This application claims priority to Japanese Patent Application No. 2024-014462, filed February 1, 2024, the contents of which are incorporated herein by reference.

[0002] Polyamides are widely used as molding materials for various components, etc. For example, Patent Document 1 discloses a polyamide resin composition containing (A) a polyamide resin, (B) glass fibers having a carboxylic acid anhydride-containing unsaturated vinyl monomer compound on at least a portion of the surface thereof, and (C) a copolymer containing the carboxylic acid anhydride-containing unsaturated vinyl monomer and having a glass transition temperature Tg exceeding 60°C.

[0003] Japanese Patent No. 6209213

[0004] However, there is still room for improvement in the durability of molded articles containing semi-aromatic polyamides.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide pellets containing glass fiber and semi-aromatic polyamide that can be used to produce molded articles with excellent durability, a method for producing such pellets, and a molded article and gear that are made from such pellets and have excellent durability.

[0006] As a result of intensive research aimed at solving the above-mentioned problems, the inventors have found that the durability of a molded article obtained by injection molding pellets can be improved by setting the value of the coefficient of variation of the distance between the centers of gravity of glass fibers, which is measured on a cross section of a test piece obtained by injection molding pellets, to a specific value, and have completed the present disclosure. That is, the present disclosure has the following aspects.

[0007] [1] A pellet comprising a semi-aromatic polyamide and a glass fiber, wherein the semi-aromatic polyamide has a structural unit represented by the following formula (1), and the coefficient of variation of the distance between the centers of gravity of the glass fiber is 0.570 or less in a cross section at the center in the MD direction of a test piece obtained by molding the pellet under the following molding conditions. (Molding conditions) [Test piece] Type A test piece specified in ISO 3167:93. [Injection molding conditions] Barrel temperature: 330 to 350°C, mold temperature: 120°C, back pressure: 7 MPa, screw rotation speed: 100 rpm, injection pressure: 70 MPa, injection speed: 26 mm / s, injection time: 2 seconds, dwell pressure: 50 MPa, cooling time: 20 seconds, and filling time: 2 seconds. [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12.

[0008] [2] The pellet according to [1], wherein the content of the glass fiber is 10% by mass or more and 60% by mass or less relative to 100% by mass of the total content of the semi-aromatic polyamide and the glass fiber.

[0009] [3] In the formula (1), the Ar １ represents a 1,4-phenylene group, and p is 9 or 10.

[0010] [4] A method for producing pellets according to any one of [1] to [3], comprising melt-kneading a semi-aromatic polyamide and glass fibers in an extruder, the extruder having a kneading zone, and the kneading zone including a counter-rotating screw element.

[0011] [5] A molded article obtained by injection molding the pellet according to any one of [1] to [3].

[0012] [6] A gear comprising a semi-aromatic polyamide and glass fibers, wherein the semi-aromatic polyamide has a structural unit represented by formula (1), and the coefficient of variation of the distance between centers of gravity of the glass fibers is 0.570 or less in a cross section of the gear teeth cut along a perpendicular bisector to a line connecting a root and a tip of the tooth. [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12.

[0013] According to the present disclosure, it is possible to provide pellets containing glass fiber and semi-aromatic polyamide that can be used to produce a molded article having excellent durability, a method for producing such pellets, and a molded article and gear having excellent durability that are made from such pellets.

[0014] 2B is a partially enlarged view illustrating gear teeth. FIG. 2C is an example of an SEM image used to calculate the coefficient of variation of the distance between the centers of gravity of glass fibers in the examples. FIG. 2D is a processed image obtained by binarizing the SEM image of FIG. 2A using image analysis software and used to calculate the coefficient of variation of the distance between the centers of gravity of glass fibers. FIG. 2E is a plan view showing a resin gear produced in the examples. FIG. 2F is a schematic diagram showing the outline configuration and screw configuration of a cylinder part of a twin-screw extruder used in the examples.

[0015] The pellets, the method for producing the pellets, the compacts, and the gears of the present disclosure will be described below.

[0016] Pellets: A pellet according to an embodiment comprises a semi-aromatic polyamide and glass fibers, wherein the semi-aromatic polyamide has a structural unit represented by the following formula (1), and a test piece obtained by molding the pellets under the following molding conditions has a coefficient of variation of the distance between the centers of gravity of the glass fibers in a cross section at the center in the MD direction of the test piece, of 0.570 or less. (Molding Conditions) [Test Piece] Type A test piece according to ISO 3167:93. [Injection Molding Conditions] Barrel temperature: 330-350°C, mold temperature: 120°C, back pressure: 7 MPa, screw rotation speed: 100 rpm, injection pressure: 70 MPa, injection speed: 26 mm / s, injection time: 2 seconds, dwell pressure: 50 MPa, cooling time: 20 seconds, and filling time: 2 seconds.

[0017] [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12.

[0018] In this specification, the term "semi-aromatic polyamide" refers to a polyamide in which the total amount of aliphatic diamines and aliphatic dicarboxylic acids accounts for 30 mol % or more and 70 mol % or less of the total amount of diamine components and dicarboxylic acid components constituting the polyamide, with the remainder being aromatic diamines and aromatic dicarboxylic acids.

[0019] Pellets having the above coefficient of variation of 0.570 or less have improved durability of molded articles obtained by injection molding the pellets, compared to pellets having a coefficient of variation that does not satisfy the above requirement of 0.570 or less.

[0020] The pellets contain glass fibers. The pellets have a coefficient of variation of the distance between the centers of gravity of the glass fibers, measured on a cross section of a test piece molded from the pellets under the molding conditions described above, of 0.570 or less, preferably 0.568 or less, more preferably 0.566 or less, and even more preferably 0.564 or less.

[0021] Pellets having a coefficient of variation of glass fibers in the cross section of the test piece of 0.570 or less have high durability when molded by injection molding the pellets.

[0022] The value of the coefficient of variation may be 0.060 or more, 0.080 or more, 0.100 or more, or 0.150 or more.

[0023] The value of the coefficient of variation may be 0.060 or more and 0.570 or less, 0.080 or more and 0.568 or less, 0.100 or more and 0.566 or less, or 0.150 or more and 0.564 or less.

[0024] The coefficient of variation is an index representing the variation in the distance between the centers of gravity of the glass fibers. The smaller the value of the coefficient of variation, the smaller the variation in the distance between the centers of gravity. The coefficient of variation is expressed as standard deviation / average value. By dividing the standard deviation by the average value, the influence of the magnitude of the value of the distance between the centers of gravity can be eliminated, and the variation can be evaluated with high accuracy.

[0025] The average value of the distance between the centers of gravity of the glass fibers may be 80.0 μm or less, 58.3 μm or more and 78.0 μm or less, or 58.5 μm or more and 76.0 μm or less.

[0026] The standard deviation of the distance between the centers of gravity of the glass fibers may be 34.0 μm or less, 32.0 μm or more and 33.9 μm or less, or 32.5 μm or more and 33.8 μm or less.

[0027] The "distance between centers of gravity" of glass fibers is measured as the distance between the centers of gravity of the areas occupied by the cross sections of scattered glass fibers in a two-dimensional observation image of the cross section at the center of the MD direction of the test piece to be measured.

[0028] The "average value of the distance between centers of gravity" of the glass fibers is calculated by calculating the distance between centers of gravity of all combinations of the cross sections of the multiple glass fibers that appear in the two-dimensional observation image, and then calculating the arithmetic average value of all the distances between centers of gravity obtained.

[0029] The "coefficient of variation of the distance between centers of gravity" of glass fibers is calculated based on the distance between centers of gravity of glass fibers scattered in the cross section at the center of the MD direction of the test piece. That is, the coefficient of variation can be calculated by calculating the standard deviation from the distance between centers of gravity and the average value, and then dividing the standard deviation by the average value. In this specification, the "cross section at the center of the MD direction of the test piece" refers to the cross section perpendicular to the MD direction at the center of the MD direction of the test piece.

[0030] In the test piece, which is an injection-molded article, the glass fibers are oriented in the MD direction. In the cross section of the test piece at the center in the MD direction, a cross section of the glass fibers cut in a direction perpendicular to the axial direction of the glass fibers (hereinafter simply referred to as the "orthogonal direction") is exposed.

[0031] In this embodiment, the dispersion state (distance between centers of gravity) of the glass fibers dispersed within the pellets is confirmed as a substitute for the dispersion state of the glass fibers in the test specimen. The inventors' studies have revealed that test specimens obtained by injection molding pellets under the above molding conditions maintain the dispersion state of the glass fibers in the pellets to a large extent, while allowing the measurement of the distance between centers of gravity for a larger number of glass fibers than in pellets, thereby enabling the dispersion state to be grasped more appropriately. Specifically, it has been found that there is a positive correlation between the dispersion state of test specimens injection-molded from pellets with poor dispersion (long distance between centers of gravity in the cross section) and the dispersion state of test specimens injection-molded from pellets with good dispersion (short distance between centers of gravity in the cross section).

[0032] In the case of ordinary cylindrical glass fibers, the cross section of a glass fiber cut in the orthogonal direction is observed as a circle, and can therefore be easily distinguished from the cross section of a glass fiber not cut in the orthogonal direction. The cross section of a glass fiber cut at a slight angle from the orthogonal direction may also be included in the measurement object. In the case of ordinary cylindrical glass fibers, the cross section of a glass fiber cut at a slight angle from the orthogonal direction is observed as an ellipse. In this specification, the cross section of a glass fiber in which the ratio of the major axis / minor axis of the circumscribed rectangle that has the smallest area surrounding the cross section of the glass fiber is 1 or more and 2 or less is defined as the cross section of the glass fiber cut in the orthogonal direction. Alternatively, cross sections that do not fall under the "cross section of a glass fiber in which the ratio of the major axis / minor axis of the circumscribed rectangle that has the smallest area surrounding the cross section of the glass fiber is 1 or more and 2 or less" may be manually excluded from the measurement object before analyzing the distance between the centers of gravity.

[0033] The value of the coefficient of variation of the distance between the centers of gravity of the glass fibers is obtained by the following image acquisition and analysis.

[0034] [Coefficient of variation of distance between centers of gravity of glass fiber] (Image acquisition) A test piece to be measured is cut, the cut piece is immersed in epoxy resin, and polished so that the cut surface to be measured is exposed. Then, an ion sputtering apparatus (for example, E-1030 manufactured by Hitachi, Ltd.) is used to polish the cut surface. －７ A palladium alloy is vapor-deposited on the cut surface under a pressure of 0.05 Pa, and a cross-sectional image of the test piece is obtained using a scanning electron microscope (SEM, Hitachi, Ltd., S-4700 model) under conditions of an acceleration voltage of 25 kV and an observation magnification of 600. Of the cross-sectional images of the test piece, glass fibers cut in a direction perpendicular to the axial direction of the glass fibers are used as the object for measuring the distance between the centers of gravity of the glass fibers.

[0035] (Analysis) The cross-sectional image is subjected to median processing with a filter size of 5 × 5 using image analysis software (Mitani Corporation, WinROOF, Ver. 3.54), and then binarized into a resin phase region and a cross-sectional region of the glass fiber (for example, the threshold value during binarization is set to 100). The threshold value for the binarization process may be set to a value that allows visual inspection of the image and distinguishing between regions occupied by glass fiber and regions occupied by other components. Using the processed two-dimensional observation image, dust and noise that are clearly not glass fiber, regions of glass fiber cut in the middle of the image edge, and regions of glass fiber not cut in a direction perpendicular to the axial direction of the glass fiber are excluded from the analysis, and then the average value and standard deviation of the distance between the centers of gravity of the glass fiber regions and the coefficient of variation expressed as standard deviation / average value are calculated.

[0036] For the analysis, cross-sectional images containing 30 to 500 cross sections of glass fibers cut in orthogonal directions are used. Analysis is performed using 20 to 100 such cross-sectional images, with the total number of glass fiber cross sections being 3,000 to 10,000.

[0037] The average diameter of the circular area equivalent diameter (diameter converted into a perfect circle of the same area) of the region occupied by one glass fiber obtained from the above two-dimensional observation image may be a numerical value exemplified as the fiber diameter (single fiber diameter) of the glass fiber described below, and may be, for example, 5 μm or more and 20 μm or less.

[0038] The coefficient of variation of the distance between the centers of gravity of the glass fibers can be controlled by adjusting the production conditions related to the intensity of melt kneading in the process of kneading the semi-aromatic polyamide and the glass fibers, as will be explained later in the pellet production method.

[0039] <Glass Fiber> Examples of the glass fiber include chopped glass fiber of long fiber type and milled glass fiber of short fiber type, etc. The above-mentioned pellets may contain two or more types of glass fiber.

[0040] Examples of glass fibers include E-glass, A-glass, C-glass, D-glass, AR-glass, R-glass, S-glass, and mixtures thereof. Among these, E-glass is preferred because it has excellent strength and is easily available.

[0041] As the glass fiber, a weakly alkaline fiber is preferable because it has excellent mechanical strength (tensile strength and Izod impact strength). In particular, a glass fiber having a silicon oxide content of 50% by mass to 80% by mass, and more preferably 65% ​​by mass to 77% by mass, based on the total mass of the glass fiber, is preferable.

[0042] The glass fibers may be treated with a coupling agent such as a silane coupling agent or a titanium coupling agent, if necessary.

[0043] The glass fiber may be coated with a thermoplastic resin such as a urethane resin, an acrylic resin, or an ethylene / vinyl acetate copolymer, or a thermosetting resin such as an epoxy resin. The glass fiber may be treated with a sizing agent.

[0044] The number-average fiber length of the glass fibers in the pellets is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. When the number-average fiber length of the glass fibers is 20 μm or more, the effect as a reinforcing material in a molded article molded using the pellets is more improved than when the number-average fiber length is less than 20 μm.

[0045] The number-average fiber length of the glass fibers in the pellets is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 500 μm or less. In the case of pellets in which the number-average fiber length of the glass fibers is 1000 μm or less, the fluidity of the composition containing the semi-aromatic polyamide and the glass fibers is improved compared to when the number-average fiber length exceeds 1000 μm, and even a molded article having a fine structure can be easily molded.

[0046] An example of the numerical range of the number average fiber length of the glass fibers in the pellets is preferably 20 μm or more and 1000 μm or less, more preferably 30 μm or more and 800 μm or less, and even more preferably 40 μm or more and 500 μm or less.

[0047] (Measurement of Number-Average Fiber Length of Glass Fibers) Here, the number-average fiber length of the glass fibers in the pellets can be measured by the following method. First, 5 g of pellets are heated in an air atmosphere in a muffle furnace ("FP410" manufactured by Yamato Scientific Co., Ltd.) at 600°C for 4 hours to remove the resin and obtain an ashing residue containing glass fibers. 0.3 g of the ashing residue is added to 50 mL of ethylene glycol to prepare a mixed solution, and the mixed solution is irradiated with ultrasonic waves for 5 minutes using an ultrasonic cleaner (manufactured by VELVO-CLEAR, model number: VS-25). This causes the ashing residue to be uniformly dispersed in the ethylene glycol, and a sample solution in which the glass fibers are dispersed is obtained.

[0048] Next, 5 mL of the sample solution was diluted 5 times with ethylene glycol to obtain a sample solution. The resulting sample solution was imaged one by one using a particle shape image analyzer (Beckman Coulter's "Rapid VUE"). The imaged glass fibers were observed from the viewing direction, and the longitudinal length was read as the fiber length.

[0049] The measurement is terminated when the number of measured glass fibers reaches 10,000, and the arithmetic mean value of the fiber lengths of 10,000 glass fibers is calculated from the fiber lengths of each glass fiber thus measured, and this value is taken as the number-average fiber length of the glass fibers.

[0050] The average fiber diameter (single fiber diameter) of the glass fibers is preferably 5 μm or more and 20 μm or less. When the average fiber diameter of the glass fibers is 5 μm or more, handling is easier than when the average fiber diameter is less than 5 μm, and production efficiency can be improved. The average fiber diameter of the glass fibers is more preferably 5.5 μm or more, and even more preferably 6 μm or more. Furthermore, when the average fiber diameter of the glass fibers is 20 μm or less, the fluidity of the liquid crystal polyester pellet composition is improved compared to when the average fiber diameter exceeds 20 μm. Furthermore, the effect of the glass fibers as a reinforcing material for the molded article obtained by injection molding the pellets is further improved. The average fiber diameter of the glass fibers is more preferably 17 μm or less, and even more preferably 15 μm or less. As an example of the numerical range of the average fiber diameter (single fiber diameter) of the glass fibers, it is preferably 5 μm or more and 20 μm or less, more preferably 5.5 μm or more and 17 μm or less, and even more preferably 6 μm or more and 15 μm or less.

[0051] The diameter of the glass fibers remains substantially unchanged even after melt-kneading.

[0052] Furthermore, unless otherwise specified, the "fiber diameter of glass fiber" refers to the value measured by "Method A" among the methods described in JIS R3420 "7.6 Single Fiber Diameter."

[0053] The number average fiber length and number average fiber diameter of the glass fibers in a molded product made from pellets can be measured in the same manner as above, except that "pellets" is replaced with "molded product."

[0054] <Semi-aromatic Polyamide> Semi-aromatic polyamide can be obtained as a polymer of an aliphatic diamine and an aromatic dicarboxylic acid.

[0055] When the pellets contain a semi-aromatic polyamide, the heat resistance of the molded article obtained by injection molding the pellets is increased.

[0056] The aliphatic diamine is preferably an aliphatic diamine having 4 to 12 carbon atoms. Examples of aliphatic diamines having 4 to 12 carbon atoms include 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. These may be used alone or in combination of two or more.

[0057] Examples of aromatic dicarboxylic acids include terephthalic acid, phthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. These may be used alone or in combination of two or more.

[0058] The semi-aromatic polyamide contained in the pellets includes a semi-aromatic polyamide having a structural unit represented by the following general formula (1).

[0059] [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different from each other. p is an integer of 4 to 12, and multiple p's may be the same or different from each other.

[0060] From the viewpoint of excellent heat resistance and durability of a molded article obtained by injection molding the pellets, it is more preferable that Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p may be 9 or 10.

[0061] From the viewpoint of obtaining a molded article obtained by injection molding the pellets with even better heat resistance and durability, it is more preferable that Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p may be 10.

[0062] The Ar １ The phenylene group in Ar may be a 1,4-phenylene group or a 1,3-phenylene group. １ The naphthylene group includes a 2,6-naphthylene group and a 2,7-naphthylene group.

[0063] Preferably, in the general formula (1), Ar １ represents a 1,4-phenylene group, and p may be an integer of 4 to 12.

[0064] More preferably, in the general formula (1), Ar １ represents a 1,4-phenylene group, and p may be 9 or 10.

[0065] Particularly preferably, in the general formula (1), Ar １ represents a 1,4-phenylene group, and p may be 10.

[0066] In the semi-aromatic polyamide, the content of the structural unit represented by the general formula (1) is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units in the semi-aromatic polyamide (100%).

[0067] In the semi-aromatic polyamide, the structural unit represented by the general formula (1) is Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and the content of structural units in which p is 9 or 10 is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units in the semi-aromatic polyamide (100%).

[0068] In the semi-aromatic polyamide, the structural unit represented by the general formula (1) is Ar １represents a 1,4-phenylene group, and p is 9 or 10, the content of which is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units (100%) in the semi-aromatic polyamide.

[0069] In the semi-aromatic polyamide, the structural unit represented by the general formula (1) is Ar １ represents a 1,4-phenylene group, and p is 10, the content of which is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units (100%) in the semi-aromatic polyamide.

[0070] The melt mass-flow rate (MFR) of the semi-aromatic polyamide measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g is preferably 150 g / 10 min or less, more preferably 125 g / 10 min or less, and even more preferably 100 g / 10 min or less. In another aspect, the melt mass-flow rate (MFR) of the semi-aromatic polyamide measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g is preferably 80 g / 10 min or less, more preferably 50 g / 10 min or less, and even more preferably 30 g / 10 min or less.

[0071] The melt mass-flow rate (MFR) of the semi-aromatic polyamide, measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g, may be 5 g / 10 min or more, 10 g / 10 min or more, 15 g / 10 min or more, or 22 g / 10 min or more.

[0072] The upper and lower limits of the melt mass-flow rate (MFR) of the semi-aromatic polyamides exemplified above can be freely combined.

[0073] The melt mass-flow rate (MFR) of the semi-aromatic polyamide measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g may be, for example, 5 g / 10 min or more and 150 g / 10 min or less, 10 g / 10 min or more and 125 g / 10 min or less, or 15 g / 10 min or more and 100 g / 10 min or less. In another aspect, the melt mass flow rate (MFR) of the semi-aromatic polyamide, measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g, may be, for example, 5 g / 10 min to 80 g / 10 min, 10 g / 10 min to 50 g / 10 min, 15 g / 10 min to 30 g / 10 min, or 22 g / 10 min to 30 g / 10 min. Resin compositions containing semi-aromatic polyamides having an MFR within the above ranges tend to have excellent heat resistance and durability.

[0074] The MFR of the semi-aromatic polyamide can be controlled by appropriately adjusting conditions related to the reaction efficiency of the polymerization reaction, such as the raw material monomer, catalyst, and reaction time.

[0075] <Optional Components> The pellets may contain optional components that do not fall under either the semi-aromatic polyamide or the glass fiber.

[0076] Examples of optional components include fillers other than the glass fibers, additives, and resins that do not fall under the category of semi-aromatic polyamides (hereinafter sometimes referred to as "other resins").

[0077] The filler may be a fibrous filler or a granular filler. The filler may be an inorganic filler or an organic filler.

[0078] The content of the optional components relative to the total mass of the pellets (100% by mass) may be 10% by mass or less, 3% by mass or less, or 0% by mass.

[0079] The pellets may further contain fillers other than glass fibers, but preferably do not contain any fibrous fillers other than glass fibers.

[0080] Examples of the additives include stabilizers, release agents, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, surfactants, flame retardants, and colorants.

[0081] Examples of other resins include thermoplastic resins such as polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyphenylene ether, polyetherimide, and fluororesin; and thermosetting resins such as phenolic resin, epoxy resin, polyimide resin, and cyanate resin.

[0082] (Content) In the pellets, the proportion of the glass fiber content relative to the total content of the semi-aromatic polyamide and the glass fiber (100% by mass) is preferably 10% by mass or more, preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 55% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less. Pellets having a glass fiber content equal to or greater than the above lower limit have better durability of a molded article obtained by injection molding the pellets. Pellets having a glass fiber content equal to or less than the above upper limit have better fluidity during injection molding.

[0083] From the same viewpoint, the content of the glass fibers relative to the total mass of the pellets (100% by mass) is preferably 10% by mass or more, preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 55% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less.

[0084] From the viewpoint of durability of the molded article obtained by injection molding the pellets, the content of the semi-aromatic polyamide relative to the total mass of the pellets (100% by mass) is preferably 40% by mass or more, more preferably 40% by mass or more and 90% by mass or less, more preferably 45% by mass or more and 80% by mass or less, and even more preferably 50% by mass or more and 70% by mass or less.

[0085] The content ratios of the glass fiber and semi-aromatic polyamide in the pellets may be, for example, preferably 10% by mass or more and 60% by mass or less and 40% by mass or more and 90% by mass or less of the semi-aromatic polyamide, more preferably 20% by mass or more and 55% by mass or less and 45% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less and 50% by mass or more and 70% by mass or less, relative to 100% by mass of the total mass of the pellets. The sum of the content ratios of the glass fiber and the semi-aromatic polyamide does not exceed 100% by mass.

[0086] The pellets can be obtained by molding a resin composition containing a semi-aromatic polyamide and glass fibers.

[0087] The molding method for molding a molded body using pellets is not particularly limited, but melt molding is preferred, and examples include extrusion molding and injection molding. A molding method can be selected depending on the shape of the molded body, etc., and the molded body can be molded into the desired shape.

[0088] The above-mentioned pellets can be used as a material for molded articles for all applications to which a resin composition can generally be used as a material. Examples of the molded articles of this embodiment include electrical and electronic components such as connectors, sockets, relay parts, coil bobbins, optical pickups, oscillators, printed wiring boards, circuit boards, semiconductor packages, and computer-related parts; semiconductor manufacturing process-related parts such as IC trays and wafer carriers; home electrical appliance parts such as VTRs, televisions, irons, air conditioners, stereos, vacuum cleaners, refrigerators, rice cookers, and lighting fixtures; lighting fixture parts such as lamp reflectors and lamp holders; audio product parts such as compact discs, laser discs (registered trademark), and speakers; communication equipment parts such as ferrules for optical cables, telephone parts, facsimile parts, and modems; copier or other parts such as separation claws and heater holders. or printing machine-related parts; machine parts such as impellers, fan gears, gears, bearings, motor parts or cases; automotive parts such as automotive mechanism parts, engine parts, engine room parts, electrical parts, or interior parts; cooking utensils such as microwave cooking pots or heat-resistant tableware; heat insulating or soundproofing materials such as flooring or wall materials, support materials such as beams or pillars, building materials such as roofing materials, or civil engineering and construction materials; parts for aircraft, spacecraft, or space equipment; radiation facility components such as nuclear reactors, marine facility components, cleaning jigs, optical equipment parts, valves, pipes, nozzles, filters, membranes, medical equipment parts or medical materials, sensor parts, sanitary fixtures, sporting goods, leisure goods, or cable ties.

[0089] Among these, the molded article obtained by injection molding the pellets is preferably a gear.

[0090] The gear of the present embodiment is a gear including a semi-aromatic polyamide and glass fibers, wherein the semi-aromatic polyamide has a structural unit represented by the following formula (1), and the coefficient of variation of the distance between the centers of gravity of the glass fibers is 0.570 or less in a cross section of the gear teeth cut along a perpendicular bisector to a line connecting the base and tip of the teeth:

[0091] Fig. 1 is a partially enlarged view illustrating gear teeth, as observed from a field of view along the rotation axis of the gear. Fig. 1 is an enlarged view of the side of a gear tooth exposed on the side of a spur gear, which is a type of gear. The above-mentioned "root" and "tip" are defined as follows.

[0092] First, when the gear G is viewed from above, the intersections P1 and P2 between the root circle C and the gear tooth T are found. When the intersection P3 between the tooth T and the perpendicular bisector L1 of the baseline BL connecting the intersections P1 and P2 is assumed, the intersection P3 is defined as the "tooth tip." When the intersection P4 between the perpendicular bisector PB and the root circle C is assumed, the intersection P4 is defined as the "tooth dedendum."

[0093] Assuming that a perpendicular bisector L2 is a line segment between intersection points P3 and P4 of the perpendicular bisector L1, the gear is cut along an imaginary plane that includes the perpendicular bisector L2 and is perpendicular to the perpendicular bisector L1. The coefficient of variation of the distance between the centers of gravity is calculated for the obtained cross section. The method for calculating the coefficient of variation of the distance between the centers of gravity is as described above in [Coefficient of variation of the distance between the centers of gravity of glass fibers].

[0094] In the gear, which is an injection-molded article, the molten resin flows from the base of the gear teeth toward the tip of the gear teeth during molding, so that the glass fibers are oriented in the gear teeth from the base of the gear teeth toward the tip of the gear teeth, just as the glass fibers are oriented in the MD direction in the test specimen.

[0095] Types of gears include spur gears, helical gears, racks, internal gears, worm gears, worm wheel gears, and bevel gears. Bevel gears include hypoid gears.

[0096] The coefficient of variation of the glass fibers in the gear teeth can be determined as follows, by appropriately changing the method so that the "side surface of the gear teeth" can be observed depending on the type of gear.

[0097] When the gear is a helical gear, an internal gear, or a worm wheel gear, the "side of the gear tooth" is exposed in the field of view along the rotation axis of the gear, so the coefficient of variation of the glass fiber in the gear tooth can be determined in the same manner as the method shown in FIG.

[0098] When the gear is a rack, the "side surface of the gear tooth" is exposed in a field of view perpendicular to the extending direction of the gear. Therefore, when the gear is a rack, the coefficient of variation of the glass fiber in the gear tooth can be found by replacing the "intersection point between the tooth root circle C and the gear tooth T" with the "intersection point between the rack tooth root and the gear tooth" for the intersection points P1 and P2 in Fig. 1 in the same manner as shown in Fig. 1.

[0099] If the gear is a bevel gear, the "side surface of the gear tooth" is exposed in a field of view perpendicular to the rotation axis of the gear. Therefore, if the gear is a bevel gear, in the above explanation using Fig. 1, the operation of "cutting the gear along an imaginary plane that includes the perpendicular bisector L2 and is perpendicular to the perpendicular bisector L1" can be read as "cutting the gear along an imaginary plane that includes the perpendicular bisector L2 and follows the ridge of the gear tooth," and the other aspects can be determined in the same manner as the method shown in Fig. 1.

[0100] When the gear is a worm wheel gear, the worm wheel gear is first cut along a cross section including the rotation axis of the gear to expose the cross section of the gear teeth, and then the coefficient of variation of the glass fiber in the gear teeth can be determined in the same manner as when the gear is a rack.

[0101] Such gears have excellent durability. The durability of the gears can be measured by the following durability test.

[0102] (Gear Durability Test) A metal master gear serving as the drive gear and a test resin gear are meshed and installed in a power-absorbing gear operation tester specified in JIS B 1759. The tester is operated under the following conditions: a load torque of 5 N·m on the resin gear, a rotational speed of 5,000 rpm, no lubrication, a temperature of 150°C, a humidity of 50% RH, and a normal backlash of 0.1 mm. The total number of rotations until the resin gear breaks is measured. In this durability test, "breakage" of the resin gear refers to a state in which power cannot be transmitted from the metal master gear of the drive gear to the resin gear, for example, due to breakage of the resin gear teeth. Furthermore, a hot air generator is used to intermittently blow hot air onto the drive gear and resin gear to maintain a temperature of 150°C inside the test chamber. The shape and material of the metal master gear and the shape of the test resin gear can be as described in the examples.

[0103] Since the above-mentioned gear has good durability under high load conditions, it may be used under conditions where the torque applied to the gear is 4 N·m or more, or may be used under conditions where the torque is 4 N·m or more and 30 N·m or less, or may be used under conditions where the torque is 5 N·m or more and 20 N·m or less.

[0104] According to the pellets described above, the coefficient of variation of the distance between the centers of gravity of the glass fibers obtained from the test piece obtained under the specified molding conditions is 0.570 or less, and therefore the molded article obtained by injection molding the pellets has high durability.

[0105] The small coefficient of variation of the distance between the centers of gravity of the glass fibers makes the distribution of the glass fibers in the molded article uniform, which is presumed to result in the following phenomena: 1) stress concentration due to the difference in elastic modulus between the glass fibers and the non-glass fiber portion is unlikely to occur, and 2) aggregation of the glass fibers is reduced, reducing the probability that the glass fibers will fall off while entangling the surrounding glass fibers.These phenomena are thought to contribute to the improvement of the durability of the molded article.

[0106] <<Method for Producing Pellets>> A method for producing pellets according to an embodiment includes melt-kneading a semi-aromatic polyamide and glass fibers using an extruder, the extruder including a kneading zone, and the kneading zone including a reverse screw element.

[0107] As the extruder, a known extruder can be used, and depending on the number of screws, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, etc. can be mentioned, with a twin-screw extruder being preferred. The twin-screw extruder may be a co-rotating twin-screw extruder or a counter-rotating twin-screw extruder, with a co-rotating twin-screw extruder being preferred.

[0108] In the method for producing pellets, the extruder includes a kneading zone, the kneading zone including a counter-feeding screw element.

[0109] In the kneading zone, the raw materials in the extruder can be kneaded depending on the shape and arrangement of the screw elements. The screw elements that can constitute the kneading zone are broadly classified into forward screw elements (R) that transport the kneaded material in the same direction as the transport direction of the kneaded material from the raw material inlet to the outlet, reverse screw elements (L) that transport the kneaded material in the opposite direction to the transport direction, and neutral screw elements (N) that transport the kneaded material in neither direction. When the kneading zone includes reverse screw elements (L), the kneading strength of the semi-aromatic polyamide and the glass fiber is improved, and pellets can be easily produced in which the coefficient of variation of the distance between the centers of gravity of the glass fiber is 0.570 or less in the cross section of a test piece molded under the above-mentioned molding conditions.

[0110] The kneading zone preferably further includes a forward screw element (R). In order to further increase the kneading intensity, the kneading zone preferably has screw elements in the order of a forward screw element (R) and a reverse screw element (L) from the raw material inlet side.

[0111] The kneading zone may further include a neutral screw element (N). When the kneading zone includes a neutral screw element (N), it is preferable that the kneading zone has a forward screw element (R), a neutral screw element (N), and a reverse screw element (L) in this order from the raw material inlet side.

[0112] The number of screw elements constituting the kneading zone may be 1 or more and 10 or less, or may be 2 or more and 5 or less.

[0113] When the screw configuration shown in the examples (FIG. 4) has a kneading zone (first kneading zone N1 in FIG. 4) in which only the semi-aromatic polyamide is melt-kneaded and the semi-aromatic polyamide and the glass fiber are not melt-kneaded, the kneading zone does not need to include a reverse screw element.

[0114] The screw elements constituting the kneading zone may be of various shapes, and examples thereof include kneading disks, which are capable of distributing the glass fibers well. Examples of kneading disks include those having a shape in which multiple disks with flight tips parallel to the axial direction of the screw are stacked on top of each other. The disk shape preferably has one to three flight tip vertices, more preferably two or three, and even more preferably two.

[0115] The number of discs per screw element may be 3 to 5, with 3 being preferred.

[0116] The temperature of the kneading zone (hereinafter also referred to as the barrel temperature) is preferably set to a temperature 5 to 40° C. higher than the melting point of the semi-aromatic polyamide, and may be, for example, 300° C. or higher and 360° C. or lower, or 320° C. or higher and 340° C. By setting the temperature of the kneading zone within the above range, the kneading strength is improved favorably, and pellets can be easily produced in which the coefficient of variation of the distance between the centers of gravity of the glass fibers is 0.570 or less in the cross section of a test piece molded under the above molding conditions.

[0117] The screw length L / screw diameter D of the extruder may be 10 or more and 300 or less, or 20 or more and 200 or less.

[0118] The screw rotation speed of the extruder may be 50 rpm or more and 300,000 rpm or less, or 100 rpm or more and 12,000 rpm or less.

[0119] The extrusion rate of the kneaded material in the extruder may be 1 kg / min or more and 600 kg / min or less, and may be 5 kg / min or more and 400 kg / min or less.

[0120] The extruder preferably has a vacuum vent. The kneaded material kneaded in the extruder is extruded, for example, through a die into a strand shape, and then cut into a desired length and molded, which can be provided as a molding material such as pellets.

[0121] The molding material can be further subjected to melt molding such as injection molding as exemplified above to be molded into the shape of a desired molded article such as a gear, which can be provided as a molded article.

[0122] A method for producing pellets, comprising melt-kneading the semi-aromatic polyamide and the glass fiber in the extruder, wherein the semi-aromatic polyamide has a structural unit represented by the general formula (1) [in formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12. ] The obtained pellets are molded into a test piece under the following molding conditions, and when the coefficient of variation of the distance between the centers of gravity of the glass fibers is measured at the cross section of the center in the MD direction of the test piece, the pellets are prepared so that the coefficient of variation is 0.570 or less. (Molding Conditions) [Test Piece] Type A test piece specified in ISO 3167:93. [Injection Molding Conditions] Barrel temperature: 330 to 350°C, mold temperature: 120°C, back pressure: 7 MPa, screw rotation speed: 100 rpm, injection pressure: 70 MPa, injection speed: 26 mm / s, injection time: 2 seconds, dwell pressure: 50 MPa, cooling time: 20 seconds, and filling time: 2 seconds.

[0123] According to the above-described pellet manufacturing method, the above-described pellets can be manufactured.

[0124] Next, the present disclosure will be described in more detail by showing examples, but the present disclosure is not limited to the following examples.

[0125] <Raw materials> Resin: Semi-aromatic polyamide PA10T (Ar １ represents a 1,4-phenylene group, and p is 10, a semi-aromatic polyamide having a structural unit represented by the general formula (1), MFR: 24 g / 10 min) PA9T (Kuraray, Genestar N1000A, Ar １ represents a 1,4-phenylene group, and p is 9. Semi-aromatic polyamide having a structural unit represented by the general formula (1), MFR: 20 g / 10 min. Filler: glass fiber (manufactured by Nippon Electric Glass Co., Ltd., T-262H, average fiber diameter 10.5 μm, average fiber length 3 mm, coated with a film-forming agent containing an acid copolymer).

[0126] <<Production of Pellets>> [Examples 1 and 2, Comparative Examples 1 and 2] The above-mentioned base resin was added to a twin-screw extruder (manufactured by Ikegai Corporation, PCM-30HS, screw diameter D: 30 mm, screw length L: 1230 mm, L / D: 41) in the blending amounts (% by mass) shown in Table 1 through the main feeder, and glass fiber was added through the side feeder. The mixture was melt-kneaded under conditions of a barrel temperature of 320 to 340°C, a screw rotation speed of 250 rpm, and a discharge rate of 10 kg / min, and discharged in the form of strands through a circular nozzle (discharge port) with a diameter of 4 mm. The strands were then passed through a water-cooled belt conveyor (manufactured by Isuzu Chemical Engineering Co., Ltd.) and pelletized in a pelletizer (manufactured by Isuzu Chemical Engineering Co., Ltd.) with a roller speed of 22 m / min and a rotary blade adjusted to 270 rpm, to obtain pellets for each Example and Comparative Example.

[0127] Figure 4 is a schematic diagram of the cylinder portion of the twin-screw extruder used. The twin-screw extruder has cylinder blocks C0 to C10 extending from the main feeder MF toward the die outlet, with a side feeder SF at position C6. The screw configuration inside the cylinder includes two kneading zones N1 and N2 at positions C4 and C9, with the remaining portion consisting of a flight screw.

[0128] The screw pattern (A) in Figure 4 is the screw pattern used in Examples 1 and 2. The second kneading zone N2 at the position C9 is composed of, in order from the main feeder side, a forward screw element (3R), a neutral screw element (3N), and a reverse screw element (3L). The barrel temperature in the kneading zone is 340°C. The screw pattern (B) in Figure 4 is the screw pattern used in Comparative Examples 1 and 2. The second kneading zone N2' at the position C9 is composed of, in order from the main feeder side, three forward screw elements (3R), (3R), and (3R). The barrel temperature in the kneading zone is 340°C, the same as with screw pattern (A).

[0129] The "3" included in the symbols (3R, 3N, 3L) representing each screw element indicates that one screw element is made up of three kneading discs.

[0130] In screw pattern (A), the first kneading zone N1 at position C4 is configured in the order of 3R, 3N, 3N, 3N, 3L, 3L from the main feeder side. In screw pattern (B), the first kneading zone N1' at position C4 is configured the same as the first kneading zone N1.

[0131] <<Measurement>> [Number Average Fiber Length of Glass Fibers in Test Specimen] The number average fiber length of the glass fibers in the test specimen was measured according to the above-mentioned (Measurement of Number Average Fiber Length of Glass Fibers).

[0132] [Fiber Diameter of Glass Fiber in Test Specimen] The fiber diameter of the glass fiber in the test specimen was measured by "Method A" among the methods described in JIS R3420 "7.6 Single Fiber Diameter," and was calculated as the average value for the total number of measured glass fibers.

[0133] [Coefficient of variation of distance between centers of gravity of glass fibers] (Image acquisition) The average value of the distance between centers of gravity of the glass fibers in each example and its standard deviation were determined by image analysis of SEM images. Specifically, the pellets obtained in the examples and comparative examples were used as molding materials to injection mold test pieces A specified in ISO 3167:93. The injection molding conditions were as follows: barrel temperature 330 to 350°C, mold temperature 120°C, back pressure 7 MPa, screw rotation speed 100 rpm, injection pressure 70 MPa, injection speed 26 mm / s, injection time 2 seconds, dwell pressure 50 MPa, cooling time 20 seconds, and filling time 2 seconds.

[0134] The center of the obtained test piece was cut in a direction perpendicular to the resin flow direction (TD direction), and the cut piece was immersed in epoxy resin.Furthermore, using a polishing machine (Kasai Shoko Co., Ltd., Refine Polisher), the cut surface was pressed against a waterproof abrasive paper (Refine Tech Co., Ltd.) rotating at 200 rpm, and under the condition of running water on the polished surface, the waterproof abrasive paper was changed to #320, #600, #1200, #1500, and #2000 in order, and polished for 3 minutes each.After polishing, the polished surface was pressed against a suede cloth (Refine Tech Co., Ltd.) rotating at 200 rpm, and a diluted solution of alumina oxide powder (Refine Tech Co., Ltd.) with a particle size of 0.3 μm diluted with water was run for 30 minutes, and cutting powder etc. on the polished surface was removed.After that, the polished surface was pressed against a suede cloth (Refine Tech Co., Ltd.) rotating at 200 rpm, and under the condition of running water on the polished surface for 1 hour, and the alumina on the polished surface was removed.

[0135] Next, an ion sputtering device (Hitachi, Ltd., E-1030) was used to －７ A palladium alloy was vapor-deposited on the cut surface under a pressure of 1000 kV, and the test piece was observed using a scanning electron microscope (SEM, Hitachi, Ltd., S-4700 model) at an acceleration voltage of 25 kV and an observation magnification of 600 times to obtain a cross-sectional image of the test piece.

[0136] Since glass fibers are generally oriented in the resin flow direction, cross sections perpendicular to the minor axis of the glass fibers, i.e., the axial direction of the glass fibers, are observed on the cut surface, as shown in Figures 2A and 2B (see below). However, a small number of glass fibers oriented perpendicular to the resin flow direction were also present, and there were portions where cross sections perpendicular to the major axis of the glass fibers, i.e., the axial direction of the glass fibers, were observed. Therefore, images of the cross sections of the glass fibers were obtained by avoiding the portions of the glass fibers oriented perpendicularly. Furthermore, since voids were sometimes present in the cross sections, images were obtained by avoiding the void portions. In other words, cross sections that did not fall within the "cross section of glass fibers with a ratio of the major axis to the minor axis of the circumscribed rectangle with the smallest area surrounding the cross section of the glass fiber, which is between 1 and 2, were manually excluded before analyzing the distance between the centers of gravity.

[0137] (Analysis) The cross-sectional image obtained above was subjected to median processing with a filter size of 5 × 5 using image analysis software (Mitani Corporation, WinROOF, Ver. 3.54), and then binarized into a resin phase region and a cross-sectional region of the glass fiber (the threshold value for binarization was set to 100). The threshold value for the binarization process was set to a value that allowed visual inspection of the image and distinguishing between the region occupied by the glass fiber and the region occupied by other components. Using the processed two-dimensional observation image, dust and noise that were clearly not glass fiber and regions of glass fiber cut in the middle of the image edge were excluded from the analysis, and the average value of the distance between the centers of gravity between the glass fiber regions and its standard deviation were calculated. From these values, the coefficient of variation expressed as "standard deviation / average value of the distance between the centers of gravity" was calculated. For the analysis, 20 cross-sectional images containing 30 or more glass fibers (total number of glass fibers: 1,000) were used. 2A and 2B show an example of an SEM image (FIG. 2A) used for calculating the coefficient of variation of the distance between the centers of gravity of glass fibers, and a processed image (FIG. 2B) used for calculating the coefficient of variation of the distance between the centers of gravity of glass fibers after the SEM image is binarized using image analysis software.

[0138] [Gear Manufacturing and Durability Testing] The pellets of Examples 1 and 2 and Comparative Examples 1 and 2 were used as molding materials and injection molded under the following injection conditions: barrel temperature 320-340 ° C, mold temperature 120 ° C, back pressure 6 MPa, screw rotation speed 100 rpm, injection pressure 100 MPa, injection speed 30 mm / s, injection time 6 seconds, dwell pressure 90 MPa, and cooling time 25 seconds. Gear shape: spur gear, module 1, number of teeth 48, pressure angle 20 °, reference circle diameter 48 mm, tip circle diameter 50 mm, root circle diameter 45.5 mm, tooth width 8 mm, transition coefficient 0, straddling tooth thickness 16.909 (straddling tooth number 6). The resin gears of the examples and comparative examples were manufactured. The shape of the manufactured resin gears is shown in Figure 3.

[0139] A durability test was conducted on each of the gears obtained in the Examples and Comparative Examples. A metal master gear [material: S45C, carburized, quenched, and tempered (surface hardened), gear shape: spur gear, module 1, number of teeth: 67, pressure angle: 20°, reference circle diameter: 67 mm, tip circle diameter: 69 mm, root circle diameter: 64.5 mm, face width: 15 mm, transition coefficient: 0, straddling tooth thickness: 23.079 (number of straddling teeth: 8)] was installed as a drive gear in a power absorption gear operation tester specified in JIS B 1759, and the resin gear obtained in the Examples or Comparative Examples was meshed with the master gear.

[0140] The testing machine was operated under the following conditions: load torque on the resin gear was 5 N m, rotation speed was 5000 rpm, no lubrication, temperature was 150°C, humidity was 50% RH, and backlash in the normal direction was 0.1 mm, and the total number of rotations until the resin gear broke was measured.

[0141] In this durability test, "breakage" of the resin gear refers to a state in which power cannot be transmitted from the metal master gear of the drive gear to the resin gear, for example, due to breakage of the teeth of the resin gear. In addition, the test was conducted using a hot air generator to intermittently blow hot air onto the drive gear and resin gear so that the temperature inside the test tank was always maintained at 150°C.

[0142] The results of the above measurements are shown in Table 1.

[0143]

[0144] Furthermore, for the gear molded in Example 1, the gear teeth were cut along a perpendicular bisector to the line connecting the tooth base and tooth tip, and the coefficient of variation of the distance between the centers of gravity of the glass fibers exposed in the cross section was determined. As a result, it was confirmed that the cross section of the gear tooth tip also had the same dispersion state of the glass fibers as the results confirmed in the test specimen. Average distance between the centers of gravity of the glass fibers: 60.1 μm Standard deviation: 33.5 μm Coefficient of variation: 0.557

[0145] According to the results of the durability test, in Examples 1 and 2 in which the coefficient of variation of the distance between the centers of gravity of the glass fibers was 0.570 or less, the durability of the resin gear was significantly improved compared to Comparative Examples 1 and 2 in which the coefficient of variation was not 0.570 or less.

[0146] The durability test was carried out under high load conditions of a torque of 5 N m and at a high temperature of 150°C, and it was therefore demonstrated that the pellets of Examples 1 and 2 are useful pellets that can be used to produce gears that have excellent high-temperature durability under high load conditions.

[0147] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present disclosure. Furthermore, the present disclosure is not limited to the embodiments, but is limited only by the claims.

[0148] MF...Main feeder SF...Side feeder N1...First kneading zone N2...Second kneading zone L...Reverse feed screw element N...Neutral screw element R...Progressive feed screw element

Claims

1. Pellets comprising a semi-aromatic polyamide and glass fibers, wherein the semi-aromatic polyamide has a structural unit represented by the following formula (1), and the coefficient of variation of the distance between the centers of gravity of the glass fibers in a cross section at the center of the MD direction of a test piece obtained by molding the pellets under the following molding conditions is 0.570 or less. (Molding conditions) [Test piece] Type A test piece specified in ISO 3167:

93. [Injection molding conditions] Barrel temperature 330-350°C, mold temperature 120°C, back pressure 7 MPa, screw rotation speed 100 rpm, injection pressure 70 MPa, injection speed 26 mm / s, injection time 2 seconds, dwell pressure 50 MPa, cooling time 20 seconds, and filling time 2 seconds. [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12.

2. The pellet according to claim 1, wherein the content of the glass fiber is 10% by mass or more and 60% by mass or less relative to 100% by mass of the total content of the semi-aromatic polyamide and the glass fiber.

3. In the formula (1), the Ar １ The pellet according to claim 1 or 2, wherein p is a 1,4-phenylene group and p is 9 or 10.

4. A method for producing pellets according to claim 1 or 2, comprising melt-kneading a semi-aromatic polyamide and glass fibers in an extruder, the extruder having a kneading zone, and the kneading zone including a counter-rotating screw element.

5. A molded article obtained by injection molding the pellets according to claim 1 or 2.

6. A gear comprising a semi-aromatic polyamide and glass fibers, wherein the semi-aromatic polyamide has a structural unit represented by the following formula (1), and the coefficient of variation of the distance between the centers of gravity of the glass fibers is 0.570 or less in a cross section of the gear teeth cut along a perpendicular bisector to a line connecting the tooth base and the tooth tip. [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12.

Images