Glass-reinforced resin molded products

Abstract

Provided is a glass reinforced resin molded article capable of reducing anisotropy of shrinkage and TD-direction shrinkage. This glass reinforced molded article includes a thermoplastic resin and 10.0-90.0 mass% of a glass reinforcing material relative to the total weight. The glass reinforcing material includes flat-cross-section glass fibers having a flat cross-sectional shape in which the ratio of the major diameter to the minor diameter is 3.0-10.0. The flat-cross-section glass fiber content C relative to the total weight is 10.0-80.0 mass%. The major diameter D of the flat-cross-section glass fibers is 25.0-55.0 μm. The proportion P of glass reinforcing material having a length of 50-100 μm to the total number of glass reinforcing materials having a length of 50 μm or greater included in the glass reinforced resin molded article is 4-50%. C, D, and P above satisfy formula (1).　Formula (1): 0.46≤P / (C×D)1 / 2≤0.99

Description

[Technical Field]

[0001] This invention relates to glass-reinforced resin molded articles. [Background technology]

[0002] Conventionally, glass-reinforced resin molded articles containing flat-section glass fibers having a flat cross-sectional shape are known as glass reinforcing materials (see, for example, Patent Documents 1 and 2).

[0003] Glass-reinforced resin molded products containing flat-section glass fibers as glass reinforcement material exhibit superior dimensional stability and reduced warping compared to glass-reinforced resin molded products containing circular-section glass fibers, and also have superior mechanical properties and surface smoothness. For these reasons, they are used in lightweight, thin, and compact parts such as portable electronic device casings. As described in Patent Documents 1 and 2, attempts have been made to increase the fiber length of the flat-section glass fibers contained in glass-reinforced resin molded products containing flat-section glass fibers in order to improve their mechanical properties. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-105359 [Patent Document 2] Japanese Patent Publication No. 2010-222486 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, as electronic devices have become even more miniaturized, glass-reinforced resin molded parts used in them are required to have higher dimensional precision.

[0006] However, in order to achieve this high dimensional precision, conventional glass-reinforced resin molded products containing flattened cross-section glass fibers have a large anisotropy in shrinkage, which is expressed as the ratio of the shrinkage rate in the MD direction (hereinafter referred to as the MD direction shrinkage rate) to the shrinkage rate in the TD direction (hereinafter referred to as the TD direction shrinkage rate). In particular, it is not possible to sufficiently reduce the value of the TD direction shrinkage rate.

[0007] Here, the TD direction is the direction perpendicular to the direction in which the resin composition flows when a resin composition containing a glass reinforcing material is molded to produce a glass-reinforced resin molded product. The MD direction is the direction in which the resin composition flows when a resin composition containing a glass reinforcing material is molded to produce a glass-reinforced resin molded product.

[0008] The present invention aims to provide a glass-reinforced resin molded product that can overcome the aforementioned disadvantages, reduce the anisotropy of the shrinkage rate, and further reduce the shrinkage rate in the TD direction. [Means for solving the problem]

[0009] The inventors of the present invention have diligently investigated the reasons why conventional glass-reinforced resin molded products containing flat-section glass fibers exhibit high anisotropy in shrinkage and why the TD direction shrinkage rate cannot be sufficiently reduced. As a result, contrary to conventional attempts, they discovered that by shifting the length distribution of the glass reinforcing material in the glass-reinforced resin molded product toward the shorter direction, the anisotropy of shrinkage can be reduced, and moreover, the TD direction shrinkage rate can be reduced, thus completing the present invention.

[0010] That is, the glass fiber reinforced resin molded product of the present invention is a glass fiber reinforced resin molded product containing a glass reinforcing material in the range of 10.0 to 90.0% by mass and a thermoplastic resin in the range of 90.0 to 10.0% by mass with respect to the total amount of the glass fiber reinforced resin molded product. The glass reinforcing material includes flat cross-section glass fibers having a ratio of the major axis to the minor axis (major axis / minor axis) in the range of 3.0 to 10.0, and the content C of the flat cross-section glass fibers with respect to the total amount of the glass fiber reinforced resin molded product is in the range of 10.0 to 80.0% by mass, and the major axis D of the flat cross-section glass fibers is 30.0 in the range of ~55.0 μm, and the ratio P of the glass reinforcing material having a length in the range of 50 to 100 μm to the total number of the glass reinforcing materials having a length of 50 μm or more included in the glass fiber reinforced resin molded product is in the range of 4 to 50%, and C, D, and P satisfy the following formula (1). 0.46 ≦ P / (C×D) 1 / 2 ≦ 0.99 ···(1)

[0011] According to the glass fiber reinforced resin molded product of the present invention, by including the glass reinforcing material and the thermoplastic resin in the above ranges, and having C, D, and P in the above ranges and satisfying the formula (1), the anisotropy of the shrinkage rate can be reduced, and moreover, the shrinkage rate in the TD direction can be reduced.

[0012] The glass-reinforced resin molded article of the present invention can be obtained, for example, by kneading the glass reinforcing material and the thermoplastic resin in a twin-screw kneader and performing injection molding using the resulting resin pellets. When the glass-reinforced resin molded article of the present invention is obtained by injection molding, it can also be expressed as a glass-reinforced resin injection molded article. Furthermore, the glass fiber reinforced resin molded article of this embodiment can also be obtained by other known molding methods such as injection compression molding, two-color molding, hollow molding, foam molding (including those using supercritical fluid), insert molding, in-mold coating molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, blow molding, stamping molding, infusion, hand lay-up, spray-up, resin transfer molding, sheet molding compound, bulk molding compound, pultrusion, and filament winding.

[0013] Here, the MD direction shrinkage rate and the TD direction shrinkage rate can be determined as follows. The MD direction shrinkage rate is calculated by measuring the actual length dimension (actual length dimension; unit = mm) of the flat plate obtained by injection molding using a glass-reinforced resin composition constituting a glass-reinforced resin molded product and a mold with internal cavity dimensions of 80 mm in length, 60 mm in width, and 2.0 mm in depth using a caliper, and then calculating (80 - actual length dimension) / 80 × 100. The TD direction shrinkage rate is calculated by measuring the width dimension (actual width dimension; unit = mm) of the flat plate using a caliper, and then calculating (60 - actual width dimension) / 60 × 100.

[0014] Reducing the anisotropy of the shrinkage rate means that when manufacturing a flat glass-reinforced resin molded product with a thickness of 2 mm as described above, the ratio of the shrinkage rate in the MD direction to the shrinkage rate in the TD direction (hereinafter referred to as the shrinkage rate in the MD direction / shrinkage rate in the TD direction) is 0.50 or more. Also, being able to reduce the shrinkage rate in the TD direction means that when manufacturing a flat glass-reinforced resin molded product with a thickness of 2 mm as described above, the ratio of the shrinkage rate in the TD direction to the shrinkage rate in the TD direction of a glass-reinforced resin molded product manufactured under exactly the same conditions except that only circular cross-section glass fibers with a fiber diameter of 11.0 μm are used as the glass reinforcing material and the screw rotation speed during kneading of the glass reinforcing material and the resin is 100 rpm (hereinafter referred to as the shrinkage rate in the TD direction / reference shrinkage rate) is less than 0.70.

[0015] Further, in the glass-reinforced resin molded product of the present invention, C is in the range of 20.0 to 70.0% by mass, D is in the range of 30.0 to 50.0 μm, P is in the range of 10 to 40%, and it is preferable that C, D, and P satisfy the following formula (2). 0.54 ≦ P / (C × D) 1 / 2 ≦ 0.72 ···(2)

[0016] According to the glass-reinforced resin molded product of the present invention, when C, D, and P are in the above ranges and satisfy formula (2), the anisotropy of the shrinkage rate can be reduced, and moreover, the shrinkage rate in the TD direction can be further reduced.

[0017] Here, being able to further reduce the shrinkage rate in the TD direction means that when manufacturing a flat glass-reinforced resin molded product with a thickness of 2 mm, the shrinkage rate in the TD direction / reference shrinkage rate is less than 0.60.

[0018] Also, in the glass-reinforced resin molded product of the present invention, the flat cross-section glass fiber preferably has a flat cross-sectional shape in which the ratio of the major axis to the minor axis is in the range of 5.0 to 8.0.

[0019] Furthermore, because it offers an excellent balance of mechanical properties, heat resistance, dimensional accuracy, and material cost, the thermoplastic resin in the glass-reinforced resin molded article of the present invention is preferably one thermoplastic resin selected from the group consisting of polycarbonate, polybutylene terephthalate, polyamide, or polyetheretherketone.

[0020] Furthermore, when a flat glass-reinforced resin molded product with a thickness of 2 mm is manufactured, the above formula (2) is satisfied, and the effects of the present invention are greatly enhanced. Therefore, in the glass-reinforced resin molded product of the present invention, it is more preferable that the thermoplastic resin is polycarbonate or polyamide.

[0021] Furthermore, when a flat glass-reinforced resin molded product with a thickness of 2 mm is manufactured, the MD direction shrinkage rate / TD direction shrinkage rate becomes 0.60 or higher, and the TD direction shrinkage rate / reference shrinkage rate becomes less than 0.50, and the effects of the present invention are particularly large. Therefore, in the glass-reinforced resin molded product of the present invention, it is even more preferable that the thermoplastic resin is polyamide. [Modes for carrying out the invention]

[0022] Next, embodiments of the present invention will be described in more detail.

[0023] The glass-reinforced resin molded product of this embodiment is a glass-reinforced resin molded product comprising, in a range of 10.0 to 90.0% by mass of glass reinforcing material and in a range of 90.0 to 10.0% by mass of thermoplastic resin, wherein the glass reinforcing material comprises flat cross-sectional glass fibers having a flat cross-sectional shape with a ratio of major axis to minor axis (major axis / minor axis) in the range of 3.0 to 10.0, the content C of the flat cross-sectional glass fibers in the total amount of the glass-reinforced resin molded product being in the range of 10.0 to 80.0% by mass, and the major axis D of the flat cross-sectional glass fibers is 30.0The glass reinforcing materials are in the range of ~55.0 μm, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product is in the range of 4 to 50%, and C, D and P satisfy the following formula (1). 0.46 ≤ P / (C×D) 1 / 2 ≤ 0.99 ···(1)

[0024] Here, the larger P is, the less anisotropy the shrinkage rate becomes, but the absolute value of the shrinkage rate in the TD direction tends to worsen. Also, the larger C is, the larger the value of P becomes, and while the absolute value of the shrinkage rate in the TD direction decreases, the anisotropy of the shrinkage rate tends to worsen. Also, the larger D is, the larger the value of P tends to become, and while the anisotropy of the shrinkage rate decreases, the absolute value of the shrinkage rate in the TD direction also tends to decrease. Equation (1) is presumed to reflect these trends and express the balance between the reduction of shrinkage rate anisotropy and the reduction of the absolute value of the shrinkage rate in the TD direction.

[0025] The glass-reinforced resin molded product of this embodiment can be obtained, for example, by kneading the glass reinforcing material and the thermoplastic resin in a twin-screw kneader and performing injection molding using the resulting resin pellets.

[0026] In the glass-reinforced resin molded product of this embodiment, for example, flat-section glass fibers, circular-section glass fibers, glass flakes, glass powder, glass beads, etc., can be used as the glass reinforcing material.

[0027] The glass composition of the glass forming the flattened cross-section glass fibers or the circular cross-section glass fibers is not particularly limited. In the glass-reinforced resin molded product of this embodiment, possible glass compositions for the glass fibers include the most common E glass composition, a high-strength, high-modulus glass composition, a high-modulus, easy-to-manufacture glass composition, and a low-dielectric-constant, low-dielectric-loss-tangent glass composition. From the viewpoint of improving the strength of the glass-reinforced resin molded product, the glass composition of the glass fibers is preferably the high-strength, high-modulus glass composition or the high-modulus, easy-to-manufacture glass composition. From the viewpoint of reducing the dielectric constant and dielectric-loss-tangent of the glass-reinforced resin molded product and thereby reducing the transmission loss of high-frequency signals passing through the glass-reinforced resin molded product, the glass composition of the glass fibers is preferably the low-dielectric-constant, low-dielectric-loss-tangent glass composition.

[0028] The E glass composition consists of SiO2 in the range of 52.0 to 56.0 mass%, Al2O3 in the range of 12.0 to 16.0 mass%, MgO and CaO in total in the range of 20.0 to 25.0 mass%, and B2O3 in the range of 5.0 to 10.0 mass%, relative to the total amount of glass fibers.

[0029] The high-strength, high-modulus glass composition contains SiO2 in the range of 60.0 to 70.0 mass%, Al2O3 in the range of 20.0 to 30.0 mass%, MgO in the range of 5.0 to 15.0 mass%, Fe2O3 in the range of 0 to 1.5 mass%, and Na2O, K2O, and Li2O in total in the range of 0 to 0.2 mass%, relative to the total amount of glass fibers.

[0030] The easily manufactured glass composition with high modulus of elasticity is a composition that contains SiO2 in the range of 57.0 to 60.0 mass%, Al2O3 in the range of 17.5 to 20.0 mass%, MgO in the range of 8.5 to 12.0 mass%, CaO in the range of 10.0 to 13.0 mass%, and B2O3 in the range of 0.5 to 1.5 mass%, relative to the total amount of glass fibers, and the total amount of SiO2, Al2O3, MgO, and CaO is 98.0 mass% or more.

[0031] The low dielectric constant low dielectric loss tangent glass composition is a composition that includes SiO2 in the range of 48.0 to 62.0 mass%, B2O3 in the range of 17.0 to 26.0 mass%, Al2O3 in the range of 9.0 to 18.0 mass%, CaO in the range of 0.1 to 9.0 mass%, MgO in the range of 0 to 6.0 mass%, Na2O, K2O, and Li2O in total in the range of 0.05 to 0.5 mass%, TiO2 in the range of 0 to 5.0 mass%, SrO in the range of 0 to 6.0 mass%, F2 and Cl2 in total in the range of 0 to 3.0 mass%, and P2O5 in the range of 0 to 6.0 mass%, based on the total amount of glass fibers.

[0032] The content of each component in the aforementioned glass composition can be measured using an ICP emission spectrometer for the light element Li, and using a wavelength-dispersive X-ray fluorescence spectrometer for the other elements. The measurement method is as follows: After cutting glass fibers to an appropriate size, they are placed in a platinum crucible and melted in an electric furnace at a temperature of 1550°C for 6 hours while stirring to obtain homogeneous molten glass. If organic matter adheres to the surface of the glass fibers during cutting, or if the glass fibers are mainly included in the organic matter (resin) as a reinforcing material, the organic matter is removed by heating in a muffle furnace at 300-650°C for 2-24 hours, for example, before use. Next, the obtained molten glass is poured onto a carbon plate to produce glass cullet, which is then crushed and powdered to obtain glass powder. For the light element Li, the glass powder is heated and decomposed with acid, and then quantitatively analyzed using an ICP emission spectrometer. For the other elements, the glass powder is formed into a disc shape using a press, and then quantitatively analyzed using a wavelength-dispersive X-ray fluorescence spectrometer. Quantitative analysis using a wavelength-dispersive X-ray fluorescence spectrometer can be performed by preparing calibration curve samples based on results measured by the fundamental parameter method, and then analyzing them using the calibration curve method. The content of each component in the calibration curve sample can be quantitatively analyzed using an ICP emission spectrometer. These quantitative analysis results can then be converted to oxide equivalents to calculate the content and total amount of each component, and from these values, the content (mass%) of each component can be determined as described above.

[0033] Glass fibers having the aforementioned glass composition can be manufactured as follows. First, a glass raw material (glass batch) prepared to have the aforementioned composition is supplied to a melting furnace and melted at a temperature in the range of, for example, 1450 to 1550°C. Next, the molten glass batch (molten glass) is drawn out from 1 to 30,000 nozzle tips of a bushing controlled to a predetermined temperature and rapidly cooled to form glass filaments. Next, a sizing agent or binder is applied to the formed glass filaments using an applicator, and 1 to 30,000 glass filaments are bundled together using a sizing shoe and wound onto a tube at high speed using a winding machine to obtain glass fibers.

[0034] In this embodiment, the flattened cross-section glass fibers used in the glass-reinforced resin molded product can be obtained by controlling the temperature conditions, with the nozzle tip having a non-circular shape and having protrusions or notches for rapidly cooling the molten glass. Furthermore, the short and long diameters of the glass fibers can be adjusted by adjusting the diameter of the nozzle tip, the winding speed, and the temperature conditions. For example, increasing the winding speed can reduce the short and long diameters, while decreasing the winding speed can increase them.

[0035] Furthermore, in the flattened cross-section glass fiber, the flattened cross-sectional shape is preferably rectangular, elliptical, or oblong, and more preferably oblong. Here, the cross-sectional shape is the shape of the cross-section obtained by cutting the glass fiber with a plane perpendicular to the length direction, and the oblong shape is a rectangle with semicircular shapes attached to both ends, or a similar shape.

[0036] Normally, glass fibers are formed by bundling together multiple glass filaments. However, in glass-reinforced resin molded products, the bundling process breaks down, and the glass filaments are dispersed within the glass-reinforced resin molded product.

[0037] In this embodiment, a preferred form of the flattened cross-section glass fiber in the glass-reinforced resin molded product before molding is that the number of glass filaments constituting the glass fiber (number of bundled fibers) is preferably in the range of 1 to 20,000, more preferably in the range of 50 to 10,000, and even more preferably in the range of 1,000 to 8,000, and the glass fiber (also called glass fiber bundle or glass strand) is preferably cut to a length in the range of 1.0 to 25.0 mm, more preferably in the range of 1.2 to 10.0 mm, particularly preferably in the range of 1.5 to 6.0 mm, and most preferably in the range of 2.5 to 3.5 mm to form chopped strands. Furthermore, in addition to chopped strands, other possible forms of glass fibers having a flat cross-sectional shape in the glass-reinforced resin molded product of this embodiment that can be taken before molding include, for example, roving, in which the number of glass filaments constituting the glass fiber is in the range of 10 to 30,000 and the glass fibers are not cut, and cut fibers, in which the number of glass filaments constituting the glass fiber is in the range of 1 to 20,000 and the glass fibers are crushed to a length in the range of 0.01 to 1.00 mm by a known method such as a ball mill or Henschil mixer.

[0038] In the glass-reinforced resin molded product of this embodiment, the glass fibers may be coated on their surface with an organic substance for purposes such as improving the adhesion between the glass fibers and the resin, or improving the uniform dispersion of the glass fibers in a mixture of glass fibers and resin or inorganic material. Examples of such organic substances include urethane resin, epoxy resin, vinyl acetate resin, acrylic resin, modified polypropylene, particularly carboxylic acid-modified polypropylene, (poly)carboxylic acid, particularly copolymers of maleic acid and unsaturated monomers, or silane coupling agents.

[0039] Furthermore, in the glass-reinforced resin molded product of this embodiment, the glass fibers may be coated with a composition containing a lubricant, surfactant, etc., in addition to these resins or silane coupling agents. Such a composition coats the glass fibers at a rate of 0.1 to 2.0% by mass, based on the mass of the glass fibers in the state before coating with the composition.

[0040] Furthermore, the coating of glass fibers with organic matter can be carried out, for example, in the glass fiber manufacturing process, by applying the sizing agent or binder containing a solution of the resin, the silane coupling agent, or the composition to the glass fibers using a known method such as a roller-type applicator, and then drying the glass fibers coated with the resin, the silane coupling agent, or the composition solution.

[0041] Examples of silane coupling agents include aminosilane, chlorsilane, epoxysilane, mercaptosilane, vinylsilane, acrylicsilane, and cationicsilane. These silane coupling agents can be used individually or in combination of two or more types.

[0042] Examples of aminosilanes include γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-N'-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-anilinopropyltrimethoxysilane.

[0043] Examples of chlorsilanes include γ-chloropropyltrimethoxysilane.

[0044] Examples of epoxysilanes include γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0045] Examples of mercaptosilanes include γ-mercaptotrimethoxysilane.

[0046] Examples of vinylsilanes include vinyltrimethoxysilane and N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane.

[0047] Examples of acrylicsilanes include γ-methacryloxypropyltrimethoxysilane.

[0048] Examples of cationic silanes include N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride and N-phenyl-3-aminopropyltrimethoxysilane hydrochloride.

[0049] Examples of lubricants include modified silicone oils, animal oils and their hydrogenated counterparts, vegetable oils and their hydrogenated counterparts, animal waxes, vegetable waxes, mineral waxes, condensates of higher saturated fatty acids and higher saturated alcohols, polyethyleneimines, polyalkylpolyamine alkylamide derivatives, fatty acid amides, and quaternary ammonium salts. These lubricants can be used individually or in combination of two or more types.

[0050] Examples of animal oils include beef tallow. Examples of vegetable oils include soybean oil, coconut oil, rapeseed oil, palm oil, and castor oil.

[0051] Examples of animal-derived waxes include beeswax and lanolin.

[0052] Examples of plant-based waxes include candelilla wax and carnauba wax.

[0053] Examples of mineral-based waxes include paraffin wax and montan wax.

[0054] Examples of condensates between higher saturated fatty acids and higher saturated alcohols include stearic acid esters such as lauryl stearate.

[0055] Examples of fatty acid amides include dehydration condensates of polyethylene polyamines such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine with fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid.

[0056] Examples of quaternary ammonium salts include alkyltrimethylammonium salts such as lauryltrimethylammonium chloride.

[0057] Examples of surfactants include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. These surfactants can be used individually or in combination of two or more types.

[0058] Examples of nonionic surfactants include ethylene oxide propylene oxide alkyl ether, polyoxyethylene alkyl ether, polyoxyethylene-polyoxypropylene-block copolymer, alkyl polyoxyethylene-polyoxypropylene-block copolymer ether, polyoxyethylene fatty acid ester, polyoxyethylene fatty acid monoester, polyoxyethylene fatty acid diester, polyoxyethylene sorbitan fatty acid ester, glycerol fatty acid ester ethylene oxide adduct, polyoxyethylene castor oil ether, hydrogenated castor oil ethylene oxide adduct, alkylamine ethylene oxide adduct, fatty acid amide ethylene oxide adduct, glycerol fatty acid ester, polyglycerin fatty acid ester, pentaerythritol fatty acid ester, sorbitol fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyhydric alcohol alkyl ether, fatty acid alkanolamide, acetylene glycol, acetylene alcohol, ethylene oxide adduct of acetylene glycol, ethylene oxide adduct of acetylene alcohol, and the like.

[0059] Examples of cationic surfactants include alkyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, alkyldimethylethylammonium ethyl sulfate, higher alkylamine salts such as higher alkylamine acetates and higher alkylamine hydrochlorides, ethylene oxide adducts to higher alkylamines, condensates of higher fatty acids and polyalkylene polyamines, salts of esters of higher fatty acids and alkanolamines, salts of higher fatty acid amides, imidazoline-type cationic surfactants, and alkylpyridinium salts.

[0060] Examples of anionic surfactants include higher alcohol sulfates, higher alkyl ether sulfates, α-olefin sulfates, alkylbenzene sulfons, α-olefin sulfons, reaction products of fatty acid halides and N-methyl taurine, dialkyl sulfosuccinates, higher alcohol phosphates, and phosphate salts of higher alcohol ethylene oxide adducts.

[0061] Examples of amphoteric surfactants include amino acid-type amphoteric surfactants such as alkali metal alkylaminopropionates, betaine-type surfactants such as alkyldimethylbetaine, and imidazoline-type amphoteric surfactants.

[0062] As the glass flakes used in the glass-reinforced resin molded product of this embodiment, for example, flake-shaped flakes with a thickness in the range of 1 to 20 μm and a side length in the range of 0.05 to 1 mm can be used. Also, as the glass flakes used in the glass-reinforced resin molded product of this embodiment, for example, those with a volume-average particle size in the range of 0.5 to 20 μm can be used. Also, as the glass beads used in the glass-reinforced resin molded product of this embodiment, for example, spherical beads with an outer diameter in the range of 10 to 100 μm can be used.

[0063] Furthermore, in the glass-reinforced resin molded product of this embodiment, the thermoplastic resin may be polyethylene, polypropylene, polystyrene, styrene / maleic anhydride resin, styrene / maleimide resin, polyacrylonitrile, acrylonitrile / styrene (AS) resin, acrylonitrile / butadiene / styrene (ABS) resin, chlorinated polyethylene / acrylonitrile / styrene (ACS) resin, acrylonitrile / ethylene / styrene (AES) resin, acrylonitrile / styrene / methyl acrylate (ASA) resin, styrene / acrylonitrile (SAN) resin, methacrylic resin, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyamide, polyacetal, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polycarbonate, polyarylene sulfide, polyethersulfone (PES), or polyphenylsulfone (PPSU). Polyphenylene ether (PPE), modified polyphenylene ether (m-PPE), polyaryl ether ketone, liquid crystal polymer (LCP), fluororesin, polyetherimide (PEI), polyarylate (PAR), polysulfone (PSF), polyamideimide (PAI), polyaminobismaleimide (PABM), thermoplastic polyimide (TPI), polyethylene naphthalate (PEN), ethylene / vinyl acetate (EVA) resin, ionomer (IO) resin, polybutadiene, styrene / butadiene resin, polybutylene, polymethylpentene, olefin / vinyl alcohol resin, cyclic olefin resin, cellulose resin, polylactic acid, etc. can be used, but preferably polyamide, polycarbonate, polybutylene terephthalate, or polyaryl ether ketone can be used, more preferably polyamide or polycarbonate can be used, and even more preferably polyamide can be used.

[0064] Specifically, polyamides include polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polytetramethylene adipamide (polyamide 46), polytetramethylene sevacamide (polyamide 410), polypentamethylene adipamide (polyamide 56), polypentamethylene sevacamide (polyamide 510), polyhexamethylene sevacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polydecamethylene adipamide (polyamide 106), and Lidecamethylene sebamid (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polyundecanamide (polyamide 11), polyundecamethylene adipamide (polyamide 116), polydodecanamide (polyamide 12), polyxylene adipamide (polyamide XD6), polyxylene sebamid (polyamide XD10), polymetaxylylene adipamide (polyamide MXD6), polyparaxylylene adipamide (polyamide PXD6), polytetramethylene terephthalamide ( Polyamide 4T), Polypentamethylene terephthalamide (Polyamide 5T), Polyhexamethylene terephthalamide (Polyamide 6T), Polyhexamethylene isophthalamide (Polyamide 6I), Polynonamethylene terephthalamide (Polyamide 9T), Polydecamethylene terephthalamide (Polyamide 10T), Polyundecamethylene terephthalamide (Polyamide 11T), Polydodecamethylene terephthalamide (Polyamide 12T), Polytetramethylene isophthalamide (Polyamide 4I), Poly Examples include copolymers or mixtures thereof, consisting of one or more components from among bis(3-methyl-4-aminohexyl)methaneterephthalamide (polyamide PACMT), polybis(3-methyl-4-aminohexyl)methaneisophthalamide (polyamide PACMI), polybis(3-methyl-4-aminohexyl)methanendodecamido (polyamide PACM12), polybis(3-methyl-4-aminohexyl)methanetetradecamide (polyamide PACM14), etc.

[0065] Examples of polycarbonates include polymers obtained by a transesterification method in which a dihydroxydiaryl compound is reacted with a carbonate ester such as diphenyl carbonate in a molten state, or polymers obtained by a phosgene method in which a dihydroxyaryl compound is reacted with phosgene.

[0066] Examples of polybutylene terephthalate include polymers obtained by polycondensation of terephthalic acid or its derivatives with 1,4-butanediol.

[0067] Examples of polyaryl ether ketones include polyether ketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), and polyether ether ketone ketone (PEEKK).

[0068] Examples of polyethylene include high-density polyethylene (HDPE), medium-density polyethylene, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-high molecular weight polyethylene.

[0069] Examples of polypropylene include isotactic polypropylene, atactic polypropylene, syndiotactic polypropylene, and mixtures thereof.

[0070] Examples of polystyrene include general-purpose polystyrene (GPPS), which is atactic polystyrene having an atactic structure; high-impact polystyrene (HIPS), which is GPPS with added rubber components; and syndiotactic polystyrene, which has a syndiotactic structure.

[0071] Examples of methacrylic resins include polymers obtained by homopolymerizing one of the following: acrylic acid, methacrylic acid, styrene, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, and fatty acid vinyl esters, or polymers obtained by copolymerizing two or more of these.

[0072] Examples of polyvinyl chloride include vinyl chloride homopolymers polymerized by conventionally known methods such as emulsion polymerization, suspension polymerization, microsuspension polymerization, and bulk polymerization, copolymers of vinyl chloride monomer and copolymerizable monomers, and graft copolymers obtained by graft polymerization of vinyl chloride monomer onto a polymer.

[0073] Examples of polyacetals include homopolymers in which oxymethylene units are the main repeating units, and copolymers that mainly consist of oxymethylene units and contain oxyalkylene units having 2 to 8 adjacent carbon atoms in the main chain.

[0074] Examples of polyethylene terephthalate include polymers obtained by polycondensation of terephthalic acid or its derivatives with ethylene glycol.

[0075] Examples of polytrimethylene terephthalate include polymers obtained by polycondensation of terephthalic acid or its derivatives with 1,3-propanediol.

[0076] Examples of polyarylene sulfides include linear polyphenylene sulfides, cross-linked polyphenylene sulfides with high molecular weight obtained by curing reactions after polymerization, polyphenylene sulfide sulfones, polyphenylene sulfide ethers, and polyphenylene sulfide ketones.

[0077] Examples of modified polyphenylene ethers include polymer alloys of poly(2,6-dimethyl-1,4-phenylene) ether and polystyrene, polymer alloys of poly(2,6-dimethyl-1,4-phenylene) ether and styrene / butadiene copolymer, polymer alloys of poly(2,6-dimethyl-1,4-phenylene) ether and styrene / maleic anhydride copolymer, polymer alloys of poly(2,6-dimethyl-1,4-phenylene) ether and polyamide, and polymer alloys of poly(2,6-dimethyl-1,4-phenylene) ether and styrene / butadiene / acrylonitrile copolymer.

[0078] Examples of liquid crystal polymers (LCPs) include (co)polymers consisting of one or more structural units selected from thermotropic liquid crystal polyesters such as aromatic hydroxycarbonyl units, aromatic dihydroxy units, aromatic dicarbonyl units, aliphatic dihydroxy units, and aliphatic dicarbonyl units.

[0079] Examples of fluororesins include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), fluoroethylene propylene resin (FEP), fluoroethylene tetrafluoroethylene resin (ETFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and ethylene / chlorotrifluoroethylene resin (ECTFE).

[0080] Examples of ionomer (IO) resins include polymers obtained by copolymerizing olefins or styrene with unsaturated carboxylic acids, in which some of the carboxyl groups are neutralized with metal ions.

[0081] Examples of olefin / vinyl alcohol resins include ethylene / vinyl alcohol copolymers, propylene / vinyl alcohol copolymers, ethylene / vinyl acetate copolymer saponifies, and propylene / vinyl acetate copolymer saponifies.

[0082] Examples of cyclic olefin resins include monocyclic compounds such as cyclohexene, polycyclic compounds such as tetracyclopentadiene, and polymers of cyclic olefin monomers.

[0083] Examples of polylactic acid include poly-L-lactic acid, which is a homopolymer of the L-isomer; poly-D-lactic acid, which is a homopolymer of the D-isomer; and stereocomplex-type polylactic acid, which is a mixture thereof.

[0084] Examples of cellulose resins include methylcellulose, ethylcellulose, hydroxycellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, cellulose acetate, cellulose propionate, and cellulose butyrate.

[0085] In the glass-reinforced resin molded product of this embodiment, the content of glass reinforcing material relative to the total amount of the glass-reinforced resin molded product is preferably in the range of 20.0 to 75.0% by mass, more preferably in the range of 30.0 to 69.5% by mass, even more preferably in the range of 40.0 to 67.0% by mass, particularly preferably in the range of 45.0 to 63.0% by mass, and most preferably in the range of 50.0 to 60.0% by mass.

[0086] In the glass-reinforced resin molded product of this embodiment, the content of glass reinforcing material relative to the total amount of the glass-reinforced resin molded product can be calculated as follows. First, the mass of the glass-reinforced resin molded product (mass before heating) is measured. Next, the glass-reinforced resin molded product is heated in a muffle furnace at 625°C for a period of 0.5 to 24 hours to burn off the resin components. Then, the mass of the glass material remaining after burning off the resin components (mass after heating) is measured. From the obtained mass before heating and mass after heating, the content of glass reinforcing material can be calculated by (mass after heating / mass before heating) × 100. If materials other than glass material are present after burning off the resin components, the glass material can be separated by utilizing the difference in specific gravity of these materials.

[0087] In the glass-reinforced resin molded product of this embodiment, the content of thermoplastic resin relative to the total amount of the glass-reinforced resin molded product is preferably in the range of 80.0 to 25.0% by mass, more preferably in the range of 70.0 to 30.5% by mass, even more preferably in the range of 60.0 to 33.0% by mass, particularly preferably in the range of 55.0 to 37.0% by mass, and most preferably in the range of 50.0 to 40.0% by mass.

[0088] In the glass-reinforced resin molded product of this embodiment, the content of thermoplastic resin relative to the total amount of the glass-reinforced resin molded product can be calculated as follows. First, the mass of the glass-reinforced resin molded product (mass before heating) is measured. Next, the glass-reinforced resin molded product is heated in a muffle furnace at 625°C for a period of 0.5 to 24 hours to burn off the resin components. Then, the mass of the substance remaining after burning off the resin components (mass after heating) is measured. From the obtained mass before heating and mass after heating, the content of thermoplastic resin can be calculated by ((mass before heating - mass after heating) / mass before heating) × 100.

[0089] In the glass-reinforced resin molded product of this embodiment, the content C of the flat cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product is preferably in the range of 20.0 to 70.0% by mass, more preferably in the range of 30.0 to 67.0% by mass, even more preferably in the range of 40.0 to 65.0% by mass, particularly preferably in the range of 45.0 to 62.0% by mass, and most preferably in the range of 50.0 to 60.0% by mass.

[0090] In the glass-reinforced resin molded product of this embodiment, the content C of the flat-section glass fibers relative to the total amount of the glass-reinforced resin molded product can be calculated as follows. First, the cross-section of the glass-reinforced resin molded product is polished, and the cross-sectional shape (shape of the cross-section cut by a plane perpendicular to the length direction) of at least 200 glass material samples is observed using a scanning electron microscope (SEM). Here, if the cross-sectional shape of all the observed glass material samples is flat, the content C of the flat-section glass fibers relative to the total amount of the glass-reinforced resin molded product, calculated by the method described above, is taken as the content C of the flat-section glass fibers. On the other hand, if the observed glass material samples include those with a circular cross-sectional shape and those with a flat cross-sectional shape, the cross-sectional area and length of the glass material are measured using an SEM and a stereomicroscope for at least 200 glass material samples remaining after the resin component incineration, and the volume ratio of the glass material with a flat cross-sectional shape to the glass material with a circular cross-sectional shape is calculated. Next, the content C of the flattened cross-section glass fibers can be calculated by apportioning the glass reinforcing material based on the calculated volume ratio. Furthermore, if materials other than glass are present when analyzing the cross-sectional shape using SEM, the glass material can be separated by compositional analysis (SEM-EDX analysis).

[0091] Furthermore, the ratio of the total content of glass reinforcing materials other than flat-section glass fibers to the content C of the flat-section glass fibers is, for example, in the range of 0 to 0.50, preferably in the range of 0 to 0.30, more preferably in the range of 0 to 0.10, particularly preferably in the range of 0 to 0.05, and most preferably 0.

[0092] The flattened cross-section glass fibers used in the glass-reinforced resin molded product of this embodiment have a major axis D preferably in the range of 30.0 to 50.0 μm, more preferably in the range of 30.5 to 45.0 μm, and even more preferably in the range of 31.0 to 43.0 μm. Furthermore, in the flattened cross-section glass fibers used in the glass-reinforced resin molded product of this embodiment, the major axis D is particularly preferably in the range of 31.0 to 35.0 μm from the viewpoint of increasing the fluidity of the mixture of the glass reinforcing material and the thermoplastic resin during the manufacture of the glass-reinforced resin molded product, and particularly preferably in the range of 37.0 to 43.0 μm from the viewpoint of increasing the strength of the glass-reinforced resin molded product.

[0093] The flattened cross-section glass fibers used in the glass-reinforced resin molded product of this embodiment have a short diameter in the range of, for example, 3.0 to 18.0 μm, preferably in the range of 3.5 to 9.5 μm, more preferably in the range of 3.7 to 8.0 μm, even more preferably in the range of 4.0 to 7.4 μm, particularly preferably in the range of 4.5 to 7.0 μm, and most preferably in the range of 5.0 to 6.4 μm.

[0094] The major axis D and minor axis of the flattened cross-section glass fibers used in the glass-reinforced resin molded product of this embodiment can be calculated, for example, as follows. First, the cross-section of the glass-reinforced resin molded product is polished, and then, using an electron microscope, for 100 or more glass filaments having a flattened cross-sectional shape, the longest side passing approximately through the center of the cross-section of the glass filament is defined as the major axis D, and the side perpendicular to the major axis D at approximately the center of the cross-section of the glass filament is defined as the minor axis, and the lengths of each are measured, and the average value of these can be calculated.

[0095] The flattened cross-section glass fibers used in the glass-reinforced resin molded product of this embodiment have a ratio of major axis to minor axis (major axis / minor axis) preferably in the range of 5.0 to 8.0, more preferably in the range of 5.5 to 7.5, even more preferably in the range of 5.6 to 7.0, and particularly preferably in the range of 5.7 to 6.6.

[0096] In the glass-reinforced resin molded product of this embodiment, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product is preferably in the range of 10 to 40%, more preferably in the range of 15 to 38%, even more preferably in the range of 20 to 37%, particularly preferably in the range of 26 to 36%, and most preferably in the range of 27 to 35%. The P can be determined by the method described in the examples below.

[0097] Furthermore, in the glass-reinforced resin molded product of this embodiment, the ratio of glass reinforcing materials having a length in the range of 300 to 500 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product is preferably less than 7.0%, more preferably less than 5.0%, and even more preferably less than 3.0%.

[0098] Furthermore, in the glass-reinforced resin molded product of this embodiment, the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product is, for example, in the range of 30 to 60%, preferably in the range of 35 to 55%, and more preferably in the range of 40 to 50%.

[0099] Furthermore, in the glass-reinforced resin molded product of this embodiment, it is preferable that C, D, and P satisfy the following formula (2) when C is in the range of 20.0 to 70.0 mass%, D is in the range of 30.0 to 50.0 μm, and P is in the range of 10 to 40%. 0.54 ≤ P / (C×D) 1 / 2 ≤ 0.72 ···(2)

[0100] Furthermore, in the glass-reinforced resin molded product of this embodiment, it is even more preferable that C, D, and P satisfy the following formula (3) when the ratio of the major axis to the minor axis (major axis / minor axis) of the flattened cross-section glass fibers is in the range of 5.0 to 8.0, C is in the range of 20.0 to 70.0 mass%, D is in the range of 31.0 to 43.0 μm, and P is in the range of 10 to 40%. 0.59 ≤ P / (C×D) 1 / 2 ≤ 0.71 ···(3)

[0101] Furthermore, in the glass-reinforced resin molded product of this embodiment, it is particularly preferable that C, D, and P satisfy the following formula (4) when the ratio of the major axis to the minor axis (major axis / minor axis) of the flattened cross-section glass fibers is in the range of 5.7 to 6.6, C is in the range of 20.0 to 70.0 mass%, D is in the range of 31.0 to 35.0 μm, and P is in the range of 10 to 40%. 0.60 ≤ P / (C×D) 1 / 2 ≤ 0.70 ···(4)

[0102] The glass-reinforced resin molded product of this embodiment is preferably used for the casing and components (motherboards, frames, speakers, antennas, etc.) of portable electronic devices such as smartphones, tablets, laptops, and mobile computers.

[0103] Next, examples and comparative examples of the present invention are shown. [Examples]

[0104] [Example 1] In this example, first, flattened cross-section glass fibers in an amount of 30.0% by mass relative to the total amount were used as a glass reinforcing material, and polycarbonate (manufactured by Teijin Limited, trade name: Panlite L1250Y (referred to as PC in Tables 1-2)) in an amount of 70.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., trade name: TEM-26SS) at a screw rotation speed of 110 rpm to obtain resin pellets. The flattened cross-section glass fibers have an E-glass composition, a minor axis of 5.5 μm, a major axis D of 33.0 μm, and a major axis / minor axis ratio of 6.0.

[0105] Next, using the resin pellets obtained in this embodiment, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 120°C and an injection temperature of 300°C to produce a glass-reinforced resin molded product (glass-reinforced resin injection molded product) with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0106] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product created in this embodiment, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 1 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0107] Next, for the glass-reinforced resin molded product created in this embodiment, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product was determined by the method described later, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product was determined by the method described later.

[0108] Next, from the content C of the flat-section glass fibers relative to the total amount of the glass-reinforced resin molded product, the major axis D of the flat-section glass fibers, and the ratio P of the glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 1.

[0109] [The ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product] First, the glass-reinforced resin molded product was heated in a muffle furnace at 650°C for a period of 0.5 to 24 hours to decompose the organic matter. Next, the remaining glass material was transferred to a glass petri dish, and the glass material was dispersed on the surface of the petri dish using acetone. Then, the length of more than 1000 strands of glass material dispersed on the surface of the petri dish was measured using a stereomicroscope, and the total number of glass material strands with a length of 50 μm or more, and the number of glass material strands with a length of 50 to 100 μm (target measurement) were measured. Next, the ratio P of glass reinforcing materials with a length in the range of 50 to 100 μm was calculated by ((number of glass material strands with a length of 50 to 100 μm) / (total number of glass material strands with a length of 50 μm or more)) × 100.

[0110] [The ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product.] First, the glass-reinforced resin molded product was heated in a muffle furnace at 650°C for a period of 0.5 to 24 hours to decompose the organic matter. Next, the remaining glass material was transferred to a glass petri dish, and the glass material was dispersed on the surface of the petri dish using acetone. Then, the length of more than 1000 strands of glass material dispersed on the surface of the petri dish was measured using a stereomicroscope, and the total number of glass material strands with a length of 25 μm or more, and the number of glass material strands with a length of 25 to 100 μm (target measurement) were measured. Next, the ratio of glass reinforcing materials with a length in the range of 25 to 100 μm was calculated as ((number of glass material strands with a length of 25 to 100 μm) / (total number of glass material strands with a length of 25 μm or more)) × 100 to the total number of glass reinforcing materials with a length of 25 μm or more.

[0111] [Example 2] In this example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 42.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and resin pellets were obtained in exactly the same manner as in Example 1, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0112] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this embodiment were used.

[0113] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 1.

[0114] [Example 3] In this example, flattened cross-section glass fibers with a minor diameter of 11.0 μm, a major diameter D of 44.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 1, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 200 rpm.

[0115] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this embodiment were used.

[0116] Next, for the glass fiber reinforced resin molded product created in this example, in exactly the same manner as in Example 1, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, and the ratio P of the glass reinforcing material having a length in the range of 50 to 100 μm to the total number of the glass reinforcing materials having a length of 50 μm or more included in the glass fiber reinforced resin molded product, and the ratio of the glass reinforcing material having a length in the range of 25 to 100 μm to the total number of the glass reinforcing materials having a length of 25 μm or more included in the glass fiber reinforced resin molded product were determined. From the content rate C of the flat cross-section glass fiber with respect to the total amount of the glass fiber reinforced resin molded product, the major axis diameter D of the flat cross-section glass fiber, and the ratio P of the glass reinforcing material having a length in the range of 50 to 100 μm to the total number of the glass reinforcing materials having a length of 50 μm or more included in the glass fiber reinforced resin molded product, P / (C×D) 1 / 2 was calculated. The results are shown in Table 1.

[0117] 〔Example 4〕 In this example, first, as the glass reinforcing material, 28.0% by mass of flat cross-section glass fiber with respect to the total amount and 2.0% by mass of glass flakes with respect to the total amount, and as the thermoplastic resin, 70.0% by mass of polycarbonate with respect to the total amount were kneaded in a twin-screw kneader at a screw rotation speed of 110 rpm to obtain resin pellets. The flat cross-section glass fiber has an E glass composition, a minor axis diameter of 5.5 μm, a major axis diameter D of 33.0 μm, and a major axis diameter / minor axis diameter of 6.0. Also, the glass flakes have a thickness of 5 μm and a particle diameter of 160 μm.

[0118] Next, a glass fiber reinforced resin molded product was created in exactly the same manner as in Example 1, except that the resin pellets obtained in this example were used.

[0119] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 1.

[0120] [Example 5] In this example, resin pellets were obtained in exactly the same manner as in Example 4, except that 24.0% by mass of flattened cross-section glass fibers and 6.0% by mass of glass flakes were used as glass reinforcing materials.

[0121] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this embodiment were used.

[0122] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 1.

[0123] [Comparative Example 1] In this comparative example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 28.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 1, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0124] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this comparative example were used.

[0125] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 2.

[0126] [Comparative Example 2] In this comparative example, flattened cross-section glass fibers with a minor diameter of 11.0 μm, a major diameter D of 44.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 1, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0127] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this comparative example were used.

[0128] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 2.

[0129] [Comparative Example 3] In this comparative example, first, 10.0% by mass of flattened cross-section glass fibers and 20.0% by mass of glass flakes, based on the total amount, were used as glass reinforcing materials, and 70.0% by mass of polycarbonate, based on the total amount, were kneaded in a twin-screw kneader at a screw rotation speed of 110 rpm to obtain resin pellets. The flattened cross-section glass fibers had an E-glass composition, a minor diameter of 5.5 μm, a major diameter D of 33.0 μm, and a major diameter / minor diameter ratio of 6.0. The glass flakes had a thickness of 5 μm and a particle size of 160 μm.

[0130] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this comparative example were used.

[0131] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 2.

[0132] [Comparative Example 4] In this comparative example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 28.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Comparative Example 3, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0133] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this comparative example were used.

[0134] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined in exactly the same manner as in Example 1. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 2.

[0135] [Reference example 1] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the resin pellets were obtained in exactly the same manner as in Example 1, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0136] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 1, except that the resin pellets obtained in this reference example were used.

[0137] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined in exactly the same manner as in Example 1. The TD direction shrinkage rate was then used as the reference shrinkage rate for Examples 1-5 and Comparative Examples 1-4. The results are shown in Tables 1 and 2.

[0138] [Example 6] In this example, first, flattened cross-section glass fibers in an amount of 40.0% by mass relative to the total amount as a glass reinforcing material and polycarbonate (manufactured by Teijin Limited, trade name: Panlite L1250Y (referred to as PC in Table 3)) in an amount of 60.0% by mass relative to the total amount as a thermoplastic resin were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., trade name: TEM-26SS) at a screw rotation speed of 110 rpm to obtain resin pellets. The flattened cross-section glass fibers have an E-glass composition, a minor axis of 5.5 μm, a major axis D of 33.0 μm, and a major axis / minor axis ratio of 6.0.

[0139] Next, using the resin pellets obtained in this embodiment, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 120°C and an injection temperature of 300°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0140] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product created in this embodiment, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 2 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0141] Next, for the glass-reinforced resin molded product created in this embodiment, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined, and from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 3.

[0142] [Example 7] In this example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 42.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and resin pellets were obtained in exactly the same manner as in Example 6, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0143] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 6, except that the resin pellets obtained in this embodiment were used.

[0144] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 6. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 3.

[0145] [Reference example 2] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the resin pellets were obtained in exactly the same manner as in Example 6, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0146] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 6, except that the resin pellets obtained in this reference example were used.

[0147] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined, making them exactly the same as in Example 6. The TD direction shrinkage rate was then used as the reference shrinkage rate for Examples 6 and 7. The results are shown in Table 3.

[0148] [Comparative Example 5] In this comparative example, first, flattened cross-section glass fibers in an amount of 20.0% by mass relative to the total amount were used as a glass reinforcing material, and polycarbonate (manufactured by Teijin Limited, product name: Panlite L1250Y (referred to as PC in Table 3)) in an amount of 80.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., product name: TEM-26SS) at a screw rotation speed of 100 rpm to obtain resin pellets. The flattened cross-section glass fibers had an E-glass composition, a minor axis of 7.0 μm, a major axis D of 28.0 μm, and a major axis / minor axis ratio of 4.0.

[0149] Next, using the resin pellets obtained in this comparative example, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 120°C and an injection temperature of 300°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0150] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product prepared in this comparative example, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 3 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0151] Next, for the glass-reinforced resin molded product prepared in this comparative example, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product were determined, and the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product were calculated as P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 3.

[0152] [Comparative Example 6] In this comparative example, flattened cross-section glass fibers with a minor diameter of 5.5 μm, a major diameter D of 33.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and resin pellets were obtained in exactly the same manner as in Comparative Example 5, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 110 rpm.

[0153] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Comparative Example 5, except that the resin pellets obtained in this comparative example were used.

[0154] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined, and the content C of the flat cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product were calculated as P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 3.

[0155] [Reference example 3] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the mixture was kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm, except that the procedure was exactly the same as in Comparative Example 5 to obtain resin pellets.

[0156] Next, a glass-reinforced resin molded product was prepared using the exact same method as Comparative Example 5, except that the resin pellets obtained in this reference example were used.

[0157] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined, making it exactly the same as Comparative Example 5. The TD direction shrinkage rate was then used as the reference shrinkage rate for Comparative Examples 5 and 6. The results are shown in Table 3.

[0158] [Example 8] In this example, first, flattened cross-section glass fibers in an amount of 30.0% by mass relative to the total amount were used as a glass reinforcing material, and polybutylene terephthalate (manufactured by Polyplastics Co., Ltd., trade name: Duranex 2000 (referred to as PBT in Table 4)) in an amount of 70.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., trade name: TEM-26SS) at a screw rotation speed of 110 rpm to obtain resin pellets. The flattened cross-section glass fibers had an E-glass composition, a minor axis of 5.5 μm, a major axis D of 33.0 μm, and a major axis / minor axis ratio of 6.0.

[0159] Next, using the resin pellets obtained in this embodiment, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 90°C and an injection temperature of 250°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0160] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product created in this embodiment, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 4 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0161] Next, for the glass-reinforced resin molded product created in this embodiment, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined, and from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 4.

[0162] [Example 9] In this example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 42.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and resin pellets were obtained in exactly the same manner as in Example 8, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0163] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 8, except that the resin pellets obtained in this example were used.

[0164] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 8. Then, from the content C of the flat cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 4.

[0165] [Example 10] In this example, flattened cross-section glass fibers with a minor diameter of 11.0 μm, a major diameter D of 44.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 8, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 200 rpm.

[0166] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 8, except that the resin pellets obtained in this example were used.

[0167] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 8. Then, from the content C of the flat cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 4.

[0168] [Comparative Example 7] In this comparative example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 28.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 8, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0169] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 8, except that the resin pellets obtained in this comparative example were used.

[0170] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined in exactly the same manner as in Example 8. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 4.

[0171] [Comparative Example 8] In this comparative example, flattened cross-section glass fibers with a minor diameter of 11.0 μm, a major diameter D of 44.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 8, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0172] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 8, except that the resin pellets obtained in this comparative example were used.

[0173] Next, for the glass-reinforced resin molded product prepared in this comparative example, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined in exactly the same manner as in Example 8. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 4.

[0174] [Reference example 4] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the resin pellets were obtained in exactly the same manner as in Example 8, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0175] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 8, except that the resin pellets obtained in this reference example were used.

[0176] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined in exactly the same manner as in Example 8. The TD direction shrinkage rate was then used as the reference shrinkage rate for Examples 8-10 and Comparative Examples 7-8. The results are shown in Table 4.

[0177] [Example 11] In this example, first, flattened cross-section glass fibers in an amount of 40.0% by mass relative to the total amount were used as a glass reinforcing material, and polybutylene terephthalate (manufactured by Polyplastics Co., Ltd., trade name: Duranex 2000 (referred to as PBT in Table 5)) in an amount of 60.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machine Co., Ltd., trade name: TEM-26SS) at a screw rotation speed of 110 rpm to obtain resin pellets. The flattened cross-section glass fibers had an E-glass composition, a minor axis of 5.5 μm, a major axis D of 33.0 μm, and a major axis / minor axis ratio of 6.0.

[0178] Next, using the resin pellets obtained in this embodiment, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 90°C and an injection temperature of 250°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0179] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product created in this embodiment, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 5 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0180] Next, for the glass-reinforced resin molded product created in this embodiment, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined, and from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 5.

[0181] [Example 12] In this example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 42.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and resin pellets were obtained in exactly the same manner as in Example 11, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0182] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 11, except that the resin pellets obtained in this embodiment were used.

[0183] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 11. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 5.

[0184] [Comparative Example 9] In this comparative example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 28.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 11, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0185] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 11, except that the resin pellets obtained in this comparative example were used.

[0186] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 11. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 5.

[0187] [Reference example 5] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the resin pellets were obtained in exactly the same manner as in Example 11, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0188] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 11, except that the resin pellets obtained in this reference example were used.

[0189] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined in exactly the same manner as in Example 11. The TD direction shrinkage rate was then used as the reference shrinkage rate for Examples 11-12 and Comparative Example 9. The results are shown in Table 5.

[0190] [Example 13] In this example, first, flattened cross-section glass fibers in an amount of 60.0% by mass relative to the total amount were used as a glass reinforcing material, and polyamide (manufactured by Ube Industries, Ltd., trade name: UBE1015B (referred to as PA in Table 6)) in an amount of 40.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., trade name: TEM-26SS) at a screw rotation speed of 100 rpm to obtain resin pellets. The flattened cross-section glass fibers have an E-glass composition, a minor axis of 7.0 μm, a major axis D of 42.0 μm, and a major axis / minor axis ratio of 6.0.

[0191] Next, using the resin pellets obtained in this embodiment, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 90°C and an injection temperature of 270°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0192] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product created in this embodiment, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 6 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0193] Next, for the glass-reinforced resin molded product created in this embodiment, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined, and from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 6.

[0194] [Example 14] In this example, flattened cross-section glass fibers with a minor diameter of 5.5 μm, a major diameter D of 33.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and the mixture was kneaded in a twin-screw kneader at a screw rotation speed of 110 rpm, except that the procedure was exactly the same as in Example 13, to obtain resin pellets.

[0195] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 13, except that the resin pellets obtained in this embodiment were used.

[0196] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 13. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 6.

[0197] [Example 15] In this example, flattened cross-section glass fibers with a minor diameter of 11.0 μm, a major diameter D of 44.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 13, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 130 rpm.

[0198] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 13, except that the resin pellets obtained in this embodiment were used.

[0199] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 13. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 6.

[0200] [Reference example 6] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the resin pellets were obtained in exactly the same manner as in Example 13, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm.

[0201] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 13, except that the resin pellets obtained in this reference example were used.

[0202] Next, for the glass-reinforced resin molded product created in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined, making them exactly the same as in Example 13. The TD direction shrinkage rate was then used as the reference shrinkage rate for Examples 13-15. The results are shown in Table 6.

[0203] [Comparative Example 10] In this comparative example, first, flattened cross-section glass fibers in an amount of 30.0% by mass relative to the total amount were used as a glass reinforcing material, and polyamide (manufactured by Ube Industries, Ltd., trade name: UBE1015B (referred to as PA in Table 7)) in an amount of 70.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., trade name: TEM-26SS) at a screw rotation speed of 100 rpm to obtain resin pellets. The flattened cross-section glass fibers had an E-glass composition, a minor axis of 7.0 μm, a major axis D of 28.0 μm, and a major axis / minor axis ratio of 4.0.

[0204] Next, using the resin pellets obtained in this comparative example, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 90°C and an injection temperature of 270°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0205] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product prepared in this comparative example, and the MD direction shrinkage rate / TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 7 described later was used as the reference shrinkage rate, and the TD direction shrinkage rate / reference shrinkage rate was calculated.

[0206] Next, for the glass-reinforced resin molded product created in this embodiment, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined, and from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 7.

[0207] [Comparative Example 11] In this comparative example, flattened cross-section glass fibers with a minor diameter of 5.5 μm, a major diameter D of 33.0 μm, and a major diameter / minor diameter ratio of 6.0 were used, and resin pellets were obtained in exactly the same manner as in Comparative Example 10, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 110 rpm.

[0208] Next, a glass-reinforced resin molded product was prepared using the exact same method as Comparative Example 10, except that the resin pellets obtained in this comparative example were used.

[0209] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product were determined, and the content C of the flat cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product were calculated as P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 7.

[0210] [Reference example 7] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the mixture was kneaded in a twin-screw kneader at a screw rotation speed of 100 rpm, except that the procedure was exactly the same as in Comparative Example 10 to obtain resin pellets.

[0211] Next, a glass-reinforced resin molded product was prepared using the exact same method as Comparative Example 10, except that the resin pellets obtained in this reference example were used.

[0212] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined, making it exactly the same as Comparative Example 10. The TD direction shrinkage rate was then used as the reference shrinkage rate for Comparative Examples 10-11. The results are shown in Table 7.

[0213] [Example 16] In this example, first, flattened cross-section glass fibers in an amount of 70.0% by mass relative to the total amount were used as a glass reinforcing material, and polyetheretherketone (manufactured by Daicel Evonik Co., Ltd., product name: Vestakeep 2000G (referred to as PEEK in Table 8)) in an amount of 30.0% by mass relative to the total amount were used as a thermoplastic resin, and these were kneaded in a twin-screw kneader (manufactured by Shibaura Machinery Co., Ltd., product name: TEM-26SS) at a screw rotation speed of 120 rpm to obtain resin pellets. The flattened cross-section glass fibers have an E-glass composition, a minor axis of 5.5 μm, a major axis D of 33.0 μm, and a major axis / minor axis ratio of 6.0.

[0214] Next, using the resin pellets obtained in this embodiment, injection molding was performed using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: NEX80) at a mold temperature of 200°C and an injection temperature of 410°C to produce a glass-reinforced resin molded product with dimensions of 80 mm in length x 60 mm in width and a thickness of 2.0 mm.

[0215] Next, the shrinkage rate in the TD direction and the shrinkage rate in the MD direction were measured for the glass-reinforced resin molded product created in this embodiment, and the ratio of the MD direction shrinkage rate to the TD direction shrinkage rate was calculated. Furthermore, the TD direction shrinkage rate of the glass-reinforced resin molded product in Reference Example 8 described later was used as the reference shrinkage rate, and the ratio of the TD direction shrinkage rate to the reference shrinkage rate was calculated.

[0216] Next, for the glass-reinforced resin molded product created in this embodiment, in exactly the same manner as in Example 1, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm to the total number of glass reinforcing materials having a length of 25 μm or more contained in the glass-reinforced resin molded product are determined, and from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 8.

[0217] [Comparative Example 12] In this comparative example, flattened cross-section glass fibers with a minor diameter of 7.0 μm, a major diameter D of 28.0 μm, and a major diameter / minor diameter ratio of 4.0 were used, and resin pellets were obtained in exactly the same manner as in Example 16, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 120 rpm.

[0218] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 16, except that the resin pellets obtained in this comparative example were used.

[0219] Next, for the glass-reinforced resin molded product created in this embodiment, the MD direction shrinkage rate / TD direction shrinkage rate, the TD direction shrinkage rate / reference shrinkage rate, the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, and the ratio of glass reinforcing materials having a length in the range of 25 to 100 μm relative to the total number of glass reinforcing materials having a length of 25 μm or more included in the glass-reinforced resin molded product are determined in exactly the same manner as in Example 16. Then, from the content C of the flat cross-section glass fibers in the total amount of the glass-reinforced resin molded product, the major axis D of the flat cross-section glass fibers, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm relative to the total number of glass reinforcing materials having a length of 50 μm or more included in the glass-reinforced resin molded product, P / (C×D) 1 / 2 The value of was calculated. The results are shown in Table 8.

[0220] [Reference example 8] In this reference example, a circular cross-section glass fiber with a diameter of 11.0 μm was used as the glass reinforcing material, and the resin pellets were obtained in exactly the same manner as in Example 16, except that they were kneaded in a twin-screw kneader at a screw rotation speed of 120 rpm.

[0221] Next, a glass-reinforced resin molded product was prepared using the exact same method as in Example 16, except that the resin pellets obtained in this reference example were used.

[0222] Next, for the glass-reinforced resin molded product prepared in this reference example, the MD direction shrinkage rate, the TD direction shrinkage rate, and the MD direction shrinkage rate / TD direction shrinkage rate were determined in exactly the same manner as in Example 16, and the TD direction shrinkage rate was used as the reference shrinkage rate for Example 16 and Comparative Example 12. The results are shown in Table 8.

[0223] [Table 1]

[0224] [Table 2]

[0225] [Table 3]

[0226] [Table 4]

[0227] [Table 5]

[0228] [Table 6]

[0229] [Table 7]

[0230] [Table 8]

[0231] Tables 1 to 8 clearly show that, according to the glass-reinforced resin molded products of Examples 1 to 16, the MD direction shrinkage rate / TD direction shrinkage rate is 0.50 or higher, reducing the anisotropy of the shrinkage rate, and the TD direction shrinkage rate / reference shrinkage rate is less than 0.70, reducing the TD direction shrinkage rate.

[0232] On the other hand, from Tables 1-8, P / (C×D) 1 / 2 According to the glass-reinforced resin molded products of Comparative Examples 1 to 12, in which the value is less than 0.46 or greater than 0.99, it is clear that the MD direction shrinkage rate / TD direction shrinkage rate is less than 0.50, meaning that the anisotropy of the shrinkage rate cannot be reduced, or the TD direction shrinkage rate / reference shrinkage rate is 0.70 or greater, meaning that the TD direction shrinkage rate cannot be reduced, or both.

Claims

1. A glass-reinforced resin molded product comprising a glass reinforcing material in an amount of 10.0 to 90.0% by mass relative to the total amount of the glass-reinforced resin molded product, and a thermoplastic resin, The glass reinforcing material includes flattened cross-sectional glass fibers having a flattened cross-sectional shape in which the ratio of the major axis to the minor axis (major axis / minor axis) is in the range of 3.0 to 10.

0. The content C of the flattened cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product is in the range of 10.0 to 80.0% by mass. The major axis D of the flattened cross-section glass fiber is in the range of 30.0 to 55.0 μm. The proportion P of glass reinforcing materials having a length in the range of 50 to 100 μm, relative to the total number of glass reinforcing materials having a length of 50 μm or more, is in the range of 4 to 50%. A glass-reinforced resin molded product characterized in that C, D, and P satisfy the following formula (1). 0.46 ≦ P / (C×D) １／２ ≦ 0.99 ・・・(1)

2. A glass-reinforced resin molded article according to claim 1, characterized in that C is in the range of 20.0 to 70.0% by mass, D is in the range of 30.0 to 50.0 μm, P is in the range of 10 to 40%, and C, D, and P satisfy the following formula (2). 0.54 ≦ P / (C×D) １／２ ≦ 0.72 ・・・(2)

3. A glass-reinforced resin molded article according to claim 1 or claim 2, characterized in that the flattened cross-sectional glass fibers have a flattened cross-sectional shape in which the ratio of the major axis to the minor axis is in the range of 5.0 to 8.

0.

4. A glass-reinforced resin molded article according to any one of claims 1 to 3, characterized in that the thermoplastic resin is one thermoplastic resin selected from the group consisting of polycarbonate, polybutylene terephthalate, polyetheretherketone, or polyamide.

5. A glass-reinforced resin molded article according to claim 4, characterized in that the thermoplastic resin is polycarbonate or polyamide.

6. A glass-reinforced resin molded article according to claim 4, characterized in that the thermoplastic resin is a polyamide.

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