Press Molding Production Method

A method for manufacturing a fiber-reinforced resin molded article by cold press molding a fiber-reinforced resin material including reinforcing fibers and a thermoplastic resin using molds containing an upper mold and a lower mold, the method satisfying the following a) to f) simultaneously:

• a) the internal temperature of the fiber-reinforced resin material immediately after heating before molding (hereafter referred to as T or heating temperature) is in a temperature range higher than the melting point of a crystalline resin by 50 to 100° C. in case where the thermoplastic resin is the crystalline resin, or the heating temperature is in a temperature range higher than a glass transition temperature of an amorphous resin by 125 to 175° C. in case where the thermoplastic resin is the amorphous resin;
• b) a time from the end of heating the fiber-reinforced resin material until the heated fiber-reinforced resin material (hereinafter referred to as tc or a charge time) is arranged on the lower mold is 6.0 to 35.0 seconds;
• c) a cooling rate of the fiber-reinforced resin material from the end of heating the fiber-reinforced resin material to the time point when the fiber-reinforced resin material is arranged on the lower mold and is brought into contact with the upper mold (hereafter referred to as C1 or an air-cooling rate) is 1.0 to 6.5° C./sec;
• d) a time from when the upper mold is brought into contact with the fiber-reinforced resin material until the pressing pressure reaches a specified pressure (hereafter referred to as tp or a pressurization time) is 0.1 to 2.5 sec;
• e) a temperature when the fiber-reinforced resin material stops flowing (hereafter, referred to as Tf or a flow stop temperature) is in a temperature range of 25° C. lower than the melting point of the crystalline resin to 30° C. higher than the melting point thereof in case where the thermoplastic resin is the crystalline resin, or the flow stop temperature is in a temperature range higher than the glass transition temperature by 50 to 105° C. in case where the thermoplastic resin is the amorphous resin;
• f) a time from the time point when the pressure of the press molding machine reaches half of the specified pressure after the upper mold is brought into contact with the fiber-reinforced resin material to the time point when the temperature of the fiber-reinforced resin material reaches the flow stop temperature (hereafter referred to as tm or a moldable time) is 0.01 to 18 sec, the tm satisfying the following formula (1) using the above a) to e),
• tm
• =
• T
• -
• (
• C
• 
• 
• 1
• ×
• tc
• +
• C
• 
• 
• 2
• ×
• 0.5
• ×
• tp
• )
• -
• Tf
• C
• 
• 
• 2
• (
• 1
• )
• in the formula (1), tm represents the moldable time, T represents the heating temperature, tc represents the charge time, C1 represents the air-cooling rate, tp represents the pressurization time, Tf represents the flow stop temperature, and C2 represents a cooling rate of the fiber-reinforced resin material from when the upper mold is brought into contact with the fiber-reinforced resin material to when the fiber-reinforced resin material reaches the flow stop temperature (hereinafter referred to as C2 or a cooling rate during pressing).