Patent Publication Number: US-2023159715-A1

Title: Reinforcing material and resin molded article

Description:
TECHNICAL FIELD 
     The present invention relates to a reinforcing material and a resin molded article. 
     BACKGROUND ART 
     As disclosed in patent document 1, the use of glass flakes coated with polyamide as a reinforcing material of a thermoplastic resin is known in the art. 
     PRIOR ART LITERATURE 
     Patent Literature 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-011036 
       
    
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     There is room for improvement in strength of a resin molded article including the coated glass flakes. 
     One object of the present invention is to provide a reinforcing material that increases the strength of a resin molded article in a preferred manner and the resin molded article. 
     Means for Solving the Problem 
     A reinforcing material that solves the above problem is for use with a thermoplastic resin. The reinforcing material includes coated glass flakes and coated glass strands. Each of the coated glass strands includes a plurality of glass filaments and a coating formed on the glass filaments. The glass flakes have a thickness of 0.1 to 4.0 μm. The glass flakes have an average particle diameter of 10 to 800 μm. The coatings on the glass flakes contain a glycidyl group-including resin and aminosilane. The coatings on the glass flakes contain the glycidyl group-including resin in an amount of 30% to 95% by mass when the total amount of the glycidyl group-including resin and the aminosilane corresponds to 100% by mass. The coated glass flakes have an ignition loss of 0.1% to 2.0% by mass measured pursuant to JIS R3420 (2013). The coatings on the glass filaments contain a glycidyl group-including resin, aminosilane, and a urethane resin. The coatings on the glass filaments contain the glycidyl group-including resin in an amount of 10% to 90% by mass, the aminosilane in an amount of 0.1% to 40% by mass, and the urethane resin in an amount of 1% to 50% by mass when the total amount of the glycidyl group-including resin, the aminosilane, and the urethane resin corresponds to 100% by mass. The coated glass strands have an ignition loss of 0.1% to 2.0% by mass measured pursuant to JIS R3420 (2013). 
     A resin molded article that solves the above problem includes a thermoplastic resin and the reinforcing material. 
     Preferably, in the resin molded article, the thermoplastic resin is polyphenylene sulfide. 
     Preferably, the resin molded article includes the coated glass flakes in an amount of 1% to 35% by mass and the coated glass strands in an amount of 5% to 70% by mass when the total amount of the thermoplastic resin, the coated glass flakes, and the coated glass strands corresponds to 100% by mass. 
     Effect of the Invention 
     The present invention succeeds in increasing the strength of a resin molded article in a preferred manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a glass flake manufacturing apparatus. 
         FIG.  2    is a schematic diagram of a glass flake manufacturing apparatus. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     One embodiment of a reinforcing material and a resin molded article will now be described. 
     The reinforcing material is for use with a thermoplastic resin. The reinforcing material includes coated glass flakes and coated glass strands. 
     Each coated glass flake includes a glass flake and a coating formed on the surface of the glass flake. The coated glass flakes increase the strength of a resin molded article, which is obtained by mixing the reinforcing material in a thermoplastic resin. The glass flakes of the coated glass flakes may be produced through a blow molding process, which is disclosed in, for example, Japanese Examined Patent Publication Nos. 41-17148 and 45-3541, or a rotational molding process, which is disclosed in, for example, Japanese Laid-Open Patent Publication No. 59-21533 and Japanese National Phase Laid-Open Patent Publication No. 2-503669. 
     In the blow molding process, a glass flake manufacturing apparatus shown in  FIG.  1    can be used. The manufacturing apparatus includes a fire-resistant furnace tank  12 , a blow nozzle  15 , and press rolls  17 . A glass base material  11  melted in the fire-resistant furnace tank  12  (melting tank) is inflated by gas delivered to the blow nozzle  15  into a balloon-like hollow glass film  16 . The press rolls  17  crush the hollow glass film  16  to obtain glass flakes  1 . The thickness of the glass flakes  1  can be controlled by adjusting, for example, a tensile rate of the hollow glass film  16  or a flow rate of the gas delivered from the blow nozzle  15 . 
     In the rotational molding process, a glass flake manufacturing apparatus shown in  FIG.  2    can be used. The manufacturing apparatus includes a rotation cup  22  and a set of annular plates  23  and annular cyclone collectors  24 . Molten glass base material  11  is fed through a nozzle  21  into the rotation cup  22  and radially forced out of an upper edge of the rotation cup  22  by centrifugal force. The molten glass base material  11  is drawn by an air flow through between the annular plates  23  into the annular cyclone collectors  24 . When passing through the annular plates  23 , the molten glass is cooled and hardened into a thin film and then crushed into microscopic pieces to obtain the glass flakes  1 . The thickness of the glass flakes  1  can be controlled by adjusting, for example, the space between the annular plates  23  or the velocity of the air flow. 
     The composition of the glass flake can be a commonly known glass composition. Specifically, a glass with little alkali metal oxide, such as an E-glass, can be preferably used. A typical composition of the E-glass is described below. 
     SiO 2 : 52% to 56% by mass 
     Al 2 O 3 : 12% to 16% by mass 
     CaO: 16% to 25% by mass 
     MgO: 0% to 6% by mass 
     Na 2 O+K 2 O: 0% to 2% by mass (preferably, 0% to 0.8% by mass) 
     B 2 O 3 : 5% to 13% by mass 
     F 2 : 0% to 0.5% by mass 
     The glass flakes have a thickness of 0.1 to 4.0 μm and an average particle diameter of 10 to 800 μm. If the glass flakes are too thick or the average particle diameter of the glass flakes is too small, it will be difficult for the resin molded article to obtain high initial strength and a hot-water resistance. The initial strength of the resin molded article is the strength of the resin molded article that has not been exposed to external effects such as light, heat, force, or chemicals. 
     In the present specification, the average thickness of the glass flakes refers to a value obtained by measuring the thickness of 100 or more randomly selected glass flakes with a scanning electron microscope (SEM) and dividing the total thickness by the number of the measured glass flakes. The average particle diameter of the glass flakes refers to a particle diameter (D50) corresponding to the cumulative mass percentage of 50% in a particle diameter distribution of the glass flakes measured through a laser diffraction/scattering method. 
     The coatings of the coated glass flakes contain a glycidyl group-including resin and aminosilane. 
     In the coatings of the coated glass flakes, when the total amount of the glycidyl group-including resin and aminosilane corresponds to 100% by mass, the amount of the glycidyl group-including resin is 30% to 95% by mass, preferably, 50% to 95% by mass. 
     In the coatings of the coated glass flakes, if the amount of the glycidyl group-including resin is too small, the resin molded article will have a low initial strength and a low hot-water resistance. In the coatings of the coated glass flakes, if the amount of the glycidyl group-including resin is too large, the initial strength of the resin molded article will be lowered, the moldability of the resin molded article will be lowered, or the productivity of the glass flakes will be lowered. 
     In the coatings of the coated glass flakes, when the total amount of the glycidyl group-including resin and aminosilane corresponds to 100% by mass, the amount of aminosilane is 5% to 70% by mass, preferably, 5% to 50% by mass. 
     In the coatings of the coated glass flakes, if the amount of aminosilane is too small or too large, the resin molded article will have a low initial strength and a low hot-water resistance. 
     The coated glass flakes have an ignition loss of 0.1% to 2.0% by mass measured pursuant to JIS R3420 (2013). The measurement and calculation processes of the ignition loss specified on page 12 of JIS R3420 (2013) will now be described. 
     A test piece holder holding a test piece is placed in a dryer at 105° C.±5° C. and dried for at least 30 minutes. Subsequent to the drying, the test piece holder holding the test piece is transferred to a desiccator and cooled under room temperature. Subsequently, the test piece with the test piece holder is measured in a unit of 0.1 mg or less. The drying, cooling, and measurement are repeated until the mass becomes constant. The dried test piece with the test piece holder is placed in a muffle furnace, which is adjusted to a temperature selected from 625° C.±20° C. or 500° C. to 600° C. The test piece with the test piece holder is heated for 10 minutes or longer with the door closed. In this case, the test piece with the test piece holder may be heated for 5 minutes with the door of the muffle furnace left open before closing the door. When the temperature is 500° C. to 600° C., the heating time is set to at least 1 hour. Then, the test piece holder holding the test piece is removed from the muffle furnace and transferred to a desiccator and cooled under a standard temperature. The test piece with the test piece holder is measured in a unit of 0.1 mg or less. The heating, cooling, and measurement are repeated until the mass becomes constant. The calculation process is expressed by the following equation, where H 2  represents the ignition loss [mass fraction (%)]: 
       H 2 =[( m   1   −m   2 )/( m   1   −m   0 )]×100.
 
     Here, m 1  is mass of the dried test piece and test piece holder (g); 
     m 2  is mass of the dried and heated test piece and test piece holder (g); and 
     m 0  is mass of the test piece holder (g). 
     If the ignition loss of the coated glass flakes is too low, it will be difficult for the coated glass flakes to be granular. If the ignition loss of the coated glass flakes is too high, it will be difficult for the coated glass flakes to have a high dispersibility in a thermoplastic resin. This will decrease the initial strength of the resin molded article. Further, a cracked gas is likely to be generated from the coatings of the coated glass flakes in the manufacturing process of the resin molded article. This may adversely affect the manufacturing environment or lower the moldability of the resin molded article. 
     Examples of the glycidyl group-including resin include, for example, a bisphenol A epoxy resin, a phenol novolac epoxy resin, an O-cresol novolac epoxy resin, and a hydrogenated bisphenol A epoxy resin. The glycidyl group-including resin may be used either alone or in combination of two or more types. 
     Examples of aminosilane include, for example, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(animoethyl)-N′-β(aminoethyl)-γ-aminopropyltriethoxysilane, and γ-anilinopropyltrimethoxysilane. Aminosilane may be used either alone or in combination of two or more types. 
     The formation of the coatings on the glass flakes is performed by, for example, adding a treatment agent, which contains aminosilane, a glycidyl group-including resin, and water, to the glass flakes, and then agitating and drying the glass flakes and the treatment agent. This forms the coatings each of which covers at least part of each glass flake. The process of adding the treatment agent for the glass flakes, agitating, and drying is not specifically limited. One example of the process will now be described. 
     For example, a predetermined amount of a bonding agent is added by spraying or the like while the glass flakes are in motion in a mixer, such as a rotating disc mixer or a Henschel mixer including rotating blades in a mixing container. The glass flakes and the bonding agent are then mixed and agitated in the mixer. Subsequently, the glass flakes are dried during the agitation in the mixer. Alternately, the glass flakes are removed from the mixer and dried. This obtains the coated glass flakes. 
     In addition to the above process, the coated glass flakes can be produced by applying a known process such as an agitation granulation process, a fluidized bed granulation process, an injection granulation process, and a rotation granulation process. 
     The treatment agent for the glass flakes may further contain, for example, a surfactant, an antifoam agent, or an antistatic agent when necessary. The obtained coated glass flakes are granular. That is, each coated glass flake may be formed by bonding some glass flakes with the coatings on the surfaces of the glass flakes. 
     Each of the coated glass strands is formed by bonding a plurality of glass filaments (mono-filament) of which the surfaces are coated. That is, each coated glass strand includes a plurality of glass filaments and the coating on the glass filaments. Accordingly, in the coated glass strand, the glass filaments are bonded by the coating. In the present specification, the coatings of the coated glass strands may be referred to as “the second coatings” and distinguished from the coatings of the coated glass flakes. 
     The fiber diameter of the glass filament is, for example, 6 to 24 μm. The number of the glass filaments bonded to form a glass strand is, for example, several hundreds to several thousands. 
     The second coatings contain a glycidyl group-including resin, aminosilane, and a urethane resin. 
     In the second coatings, when the total amount of the glycidyl group-including resin, the aminosilane, and the urethane resin corresponds to 100% by mass, the amount of the glycidyl group-including resin is 10% to 90% by mass. 
     In the second coatings, if the amount of the glycidyl group-including resin is too small, the resin molded article will have a low initial strength and a low hot-water resistance. In the second coatings, if the amount of the glycidyl group-including resin is too large, the dispersibility of the coated glass strands in a thermoplastic resin will be lowered. This will decrease the initial strength of the resin molded article. 
     In the second coatings, when the total amount of the glycidyl group-including resin, the aminosilane, and the urethane resin corresponds to 100% by mass, the amount of aminosilane is 0.10% to 40% by mass. 
     In the second coatings, if the amount of aminosilane is outside the above range, the resin molded article is likely to have a low initial strength and a low hot-water resistance. 
     In the second coatings, when the total amount of the glycidyl group-including resin, the aminosilane, and the urethane resin corresponds to 100% by mass, the amount of the urethane resin is 1% to 50% by mass. 
     In the second coatings, if the amount of the urethane resin is too small, the dispersibility of the coated glass strands in a thermoplastic resin will be lowered. This will decrease the initial strength of the resin molded article. In the second coatings, if the amount of the urethane resin is too large, the initial strength and the hot-water resistance of the resin molded article will be lowered. 
     The coated glass strands have an ignition loss of 0.1% to 2.0% by mass measured pursuant to JIS R3420 (2013). 
     If the ignition loss of the coated glass strands is too low, the bondability of the coated glass strands will be lowered. If the ignition loss of the coated glass strands is too high, the dispersibility of the coated glass strands in a thermoplastic resin will be lowered. This will decrease the initial strength of the resin molded article. Further, in this case, a cracked gas is likely to be generated from the second coatings in the manufacturing processes of the resin molded article. This may adversely affect the manufacturing environment or lower the moldability of the resin molded article. 
     The coated glass strands can be obtained by applying a sizing agent to a plurality of glass filaments (mono-filament) drawn out of a nozzle hole in a bushing and then heating (drying) the sizing agent. The sizing agent contains a glycidyl group-including resin, aminosilane, and a urethane resin. The sizing agent may further contain a surfactant, an antifoam agent, or an antistatic agent when necessary. The coated glass strands may be cut into lengths of approximately 1 to 50 mm, that is, the coated glass strands may be chopped strands. 
     The resin molded article includes a thermoplastic resin and a reinforcing material. The reinforcing material includes the coated glass flakes and the coated glass strands. 
     Preferably, the thermoplastic resin is polyphenylene sulfide. However, other thermoplastic resins may be used. 
     Preferably, the resin molded article include 1% to 35% by mass of the coated glass flakes and 5% to 70% by mass of the coated glass strands when the total amount of the thermoplastic resin, the coated glass flakes, and the coated glass strands corresponds to 100% by mass. 
     If the amount of the coated glass flakes in the resin molded article is too small, the hot-water resistance will easily decrease. If the amount of the coated glass flakes in the resin molded article is too large, the initial strength of the resin molded article will easily decrease. 
     If the amount of the coated glass strands in the resin molded article is too small, the initial strength of the resin molded article will easily decrease. If the amount of the coated glass strands in the resin molded article is too large, the strength subsequent to a hot water test will easily decrease. 
     The resin molded article is used, for example, in an electric component, an electronic component, a precision machinery component, and an automobile component. 
     Next, samples will be described. 
     &lt;Coated Glass Flakes&gt; 
     In samples A1 to A4, glass flakes were mixed and agitated while blowing a glass flake treatment agent, containing aminosilane, a glycidyl group-including resin, and water, against the glass flakes in a Henschel mixer. Then, the glass flakes were dried to obtain coated glass flakes (E-glass), which are granular. 
     Table 1 shows the thickness of the glass flakes, the average particle diameter of the glass flakes, the coating composition, and the ignition loss for the coated glass flakes of samples A1 to A4. 
     &lt;Coated Glass Strands&gt; 
     In sample B1, predetermined amounts of various glass raw materials were weighed and prepared to form the glass composition of an E-glass. Then, the glass raw materials were melted to obtain molten glass. The obtained molten glass was drawn out of a bushing including a plurality of nozzles to obtain mono-filaments having a diameter of 10.5 μm. A sizing agent, containing a glycidyl group-including resin, aminosilane, and a urethane resin, was applied to the surfaces of the obtained mono-filaments. Four thousand mono-filaments were bundled with a bundling device into a glass strand, and the glass strand was wound around a paper pipe in a traversing manner. The glass strand were drawn out of the paper pipe and chopped into lengths of 3 mm. Then, the chopped glass strands were heated with a heating device to harden the sizing agent, which forms coatings (second coatings) on the mono-filaments. Coated glass strands were obtained in this manner. 
     Table 2 shows the coating composition and the ignition loss for the coated glass strands of sample B1. 
     &lt;Resin Molded Article&gt; 
     In sample C1, 10% by mass of the coated glass flakes of sample A1, 30% by mass of the coated glass strands of sample B1, and 60% by mass of a thermoplastic resin (polyphenylene sulfide) were kneaded and pelletized. The pellets serving as a resin material were injection-molded to obtain the resin molded article. 
     In samples C2 to C4, the resin molded articles were obtained in the same manner as sample C1 except in that the type of coated glass flakes were changed as illustrated in table 3. 
     An initial tensile strength and a tensile strength subsequent to a hot-water resistance test of each sample were measured in a manner pursuant to ASTM D638. In the hot-water resistance test, each resin molded article was immersed in hot water of 121° C. for 300 hours. Table 3 shows the initial tensile strength and the tensile strength subsequent to the hot-water resistance test of each sample. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Sample  
                 Sample  
                 Sample  
                 Sample  
               
               
                   
                 A1 
                 A2 
                 A3 
                 A4 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Glass 
                 Thickness (μm) 
                 0.7 
                 0.7 
                 0.7 
                 5 
               
               
                 Flake 
                 Average Particle  
                 160 
                 160 
                 160 
                 160 
               
               
                   
                 Diameter (μm) 
                   
                   
                   
                   
               
               
                 Coating  
                 Glycidyl Group- 
                 55 
                 20 
                 55 
                 55 
               
               
                   
                 Including  
                   
                   
                   
                   
               
               
                   
                 Resin (mass %) 
                   
                   
                   
                   
               
               
                   
                 Aminosilane  
                 45 
                 80 
                 45 
                 45 
               
               
                   
                 (mass %) 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Ignition Loss (mass %) 
                 0.6 
                 0.6 
                 5 
                 0.6 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Sample B1 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Glycidyl Group-Including Resin (mass %) 
                 60 
               
               
                   
                 Aminosilane (mass %) 
                 10 
               
               
                   
                 Urethane Resin (mass %) 
                 30 
               
               
                   
                 Ignition Loss (mass %) 
                 0.6 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Sample C1 
                 Sample C2 
                 Sample C3 
                 Sample C4 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Coated Glass Flake 
                 Type 
                 Sample A1 
                 Sample A2 
                 Sample A3 
                 Sample A4 
               
               
                   
                 Mass % 
                 10 
                 10 
                 10 
                 10 
               
               
                 Coated Glass Strand 
                 Type 
                 Sample B1 
                 Sample B1 
                 Sample B1 
                 Sample B1 
               
               
                   
                 Mass % 
                 30 
                 30 
                 30 
                 30 
               
               
                 Tensile Strength of 
                 Initial 
                 180 
                 166 
                 168 
                 155 
               
               
                 Resin Molded Article 
                 Subsequent to Hot- 
                 125 
                 109 
                 119 
                 102 
               
               
                 (MPa) 
                 Water Resistance Test 
                   
                   
                   
                   
               
               
                   
               
            
           
         
       
     
     For sample C2, in the coated glass flakes, the amount of the glycidyl group-including resin was too small and the amount of aminosilane was too large. Thus, the initial strength and the strength subsequent to the hot-water resistance test of the resin molded article of sample C2 were lower than sample C1. 
     For sample C3, the ignition loss of the coated glass flakes was too high. Thus, the initial strength and strength subsequent to the hot-water resistance test of the resin molded article of C3 were lower than sample C1. 
     For sample C4, the glass flakes of the coated glass flakes were too thick. Thus, the initial strength and strength subsequent to the hot-water resistance test of the resin molded article of C4 were lower than sample C1. 
     Modified Example 
     As illustrated in tables 4 and 5, coated glass flakes of samples A5 to A7 and coated glass strands of sample B2 were obtained. Further, as illustrated in table 6, resin molded articles of samples C5 to C10 were obtained. The initial tensile strength and the tensile strength subsequent to the hot-water resistance test of the resin molded article of each sample are illustrated in table 6. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                 Sample A5 
                 Sample A6 
                 Sample A7 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Glass  
                 Thickness (μm) 
                 0.7 
                 1.3 
                 0.7 
               
               
                 Flake 
                 Average Particle  
                 160 
                 160 
                 40 
               
               
                   
                 Diameter (μm) 
                   
                   
                   
               
               
                 Coating 
                 Glycidyl Group-Including  
                 55 
                 55 
                 55 
               
               
                   
                 Resin (mass %) 
                   
                   
                   
               
               
                   
                 Aminosilane (mass %) 
                 45 
                 45 
                 45 
               
            
           
           
               
               
               
               
            
               
                 Ignition Loss (mass %) 
                 1.5 
                 0.6 
                 0.6 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                   
                 Sample B2 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Glycidyl Group-Including Resin (mass %) 
                 80 
               
               
                   
                 Aminosilane (mass %) 
                 10 
               
               
                   
                 Urethane Resin (mass %) 
                 10 
               
               
                   
                 Ignition Loss (mass %) 
                 0.6 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 Sample C5 
                 Sample C6 
                 Sample C7 
                 Sample C8 
                 Sample C9 
                 Sample C10 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Coated Glass 
                 Type 
                 Sample A5 
                 Sample A6 
                 Sample A7 
                 Sample A1 
                 Sample A1 
                 Sample A1 
               
               
                 Flake 
                 Mass % 
                  10 
                  10 
                  10 
                  10 
                  5 
                  15 
               
               
                 Coated Glass 
                 Type 
                 Sample B1 
                 Sample B1 
                 Sample B1 
                 Sample B2 
                 Sample B1 
                 Sample B1 
               
               
                 Strand 
                 Mass % 
                  30 
                  30 
                  30 
                  30 
                  35 
                  25 
               
               
                 Tensile Strength 
                 Initial 
                 179 
                 177 
                 178 
                 182 
                 187 
                 175 
               
               
                 of Resin Molded 
                 Subsequent to 
                 127 
                 123 
                 124 
                 126 
                 122 
                 127 
               
               
                 Article (MPa) 
                 Hot-Water 
               
               
                   
                 Resistance Test 
               
               
                   
               
            
           
         
       
     
     As illustrated in table 6, for the resin molded articles of samples C5 to C10, similar to the resin molded article of sample C1, the initial tensile strength was greater than or equal to 175 MPa, and the tensile strength subsequent to the hot-water resistance test was greater than or equal to 122 MPa. 
     The above described embodiment has the following advantages. 
     (1) A reinforcing material is for use with a thermoplastic resin. The reinforcing material includes coated glass flakes and coated glass strands. The thickness of glass flakes of the coated glass flakes is 0.1 to 4.0 μm, and the average particle diameter of the glass flakes is 10 to 800 μm. The coatings of the coated glass flakes contain the glycidyl group-including resin and aminosilane. When the total amount of the glycidyl group-including resin and the aminosilane corresponds to 100% by mass, the amount of the glycidyl group-including resin is 30% to 95% by mass. The ignition loss of the coated glass flakes measured pursuant to JIS R3420 (2013) is 0.1% to 2.0% by mass. 
     Each coated glass strand includes a plurality of glass filaments and the coating formed on the glass filaments. The coatings of the coated glass strands contain a a glycidyl group-including resin, aminosilane, and a urethane resin. In the coatings of the coated glass strands, when the total amount of the glycidyl group-including resin, the aminosilane, and the urethane resin corresponds to 100% by mass, the amount of the glycidyl group-including resin is 10% to 90% by mass, the amount of aminosilane is 0.1% to 40% by mass, and the amount of the urethane resin is 1% to 50% by mass. The ignition loss of the coated glass strands measured pursuant to JIS R3420 (2013) is 0.1 to 2.0% by mass. 
     This structure increases the strength of the resin molded article in a preferred manner. For example, this structure maintains the strength of the resin molded article when in use. Further, this structure increases the initial strength that is the strength of the resin molded article prior to use. 
     (2) The resin molded article includes a thermoplastic resin and the reinforcing material described in the above item (1). Preferably, the thermoplastic resin is polyphenylene sulfide. When the total amount of the thermoplastic resin, the coated glass flakes, and the coated glass strands corresponds to 100% by mass, it is preferred that the resin molded article include 1% to 35% by mass of the coated glass flakes and 5% to 70% by mass of the coated glass strands. The resin molded article having such a structure easily further increases the initial strength of the resin molded article and the strength of the resin molded article subsequent to the hot water test. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
         
           
               1 ) glass flake.