A method for producing a continuous fiber-reinforced molded resin comprising a continuous fiber-reinforced molded resin comprising continuous reinforcing glass fibers with approximately circular cross-sections and a synthetic resin, wherein at an interface between each continuous reinforcing glass fiber and the synthetic resin in a cross-section perpendicular to a lengthwise direction of the continuous reinforcing fiber, at least 90% or higher of the continuous reinforcing glass fibers are present with a void percentage of 10% or lower at the interface between a continuous reinforcing glass fiber and the synthetic resin in a cross-section perpendicular to a lengthwise direction of the continuous reinforcing glass fiber,
- wherein the void percentage is determined by the following formula:
- Void percentage (%)=(area of voids in region of outer peripheral edge separated from perimeter of continuous reinforcing fiber by 1/10 of radius of continuous reinforcing fiber)/(area of region of outer peripheral edge separated from perimeter of continuous reinforcing fiber by 1/10 of radius of continuous reinforcing fiber)×100, after rotating a lengthwise-perpendicular cross-section of a continuous reinforcing fiber of the continuous fiber-reinforced molded resin cut to 1 cm-square with a band saw, on a polishing table rotating at 100 rpm, with a force of 400 g/cm2 applied to the polishing surface, polishing it at approximately 7 mL/min in the order:
- 10 minutes with #220 waterproof paper, 2 minutes with #400 waterproof paper, 5 minutes with #800 waterproof paper, 10 minutes with #1200 waterproof paper, 15 minutes with #2000 waterproof paper, 15 minutes with 9 μm silicon carbide film particles, 15 minutes with 5 μm alumina film particles, 15 minutes with 3 μm alumina film particles, 15 minutes with 1 μm alumina film particles and 10 minutes with 0.1 μm colloidal silica particles with buffing paper foamed polyurethane, while adding water, observing the polished sample with a scanning electron microscope (SEM) and performing image analysis,
- the method comprising:
- a step of hot pressing reinforcing fibers that have addition of a sizing agent comprising a coupling agent, binding agent and lubricating agent, with a thermoplastic resin that has a terminal functional groups that are reactive with the coupling agent and has a μ-drop formation coefficient with the reinforcing fibers of 10 or greater, at above the melting point of the thermoplastic resin, wherein a flow rate of the thermoplastic resin during the hot pressing is 10% or lower, and
- a step of cooling to below the melting point of the thermoplastic resin to obtain a continuous fiber-reinforced molded resin,
- wherein the flow rate of the thermoplastic resin during hot pressing is determined as (weight of thermoplastic resin burrs produced during hot pressing)/(weight of thermoplastic resin before hot pressing),
- wherein the hot pressing is carried out by either a molding method allowing a die interior to be sealed during molding, including using an inlay die, or a molding method using a double belt press with adjustable pressure, whereby leakage of the resin is prevented and variation in the volume of the continuous fiber-reinforced molded resin occupied by the glass fibers before and after molding is reduced, and
- wherein the μ-drop formation coefficient is measured using a composite material boundary interface property evaluator, with the resin set in the heating furnace unit and the furnace temperature set to 40° C. below the melting point of the resin, the resin is adhered to each of the individual reinforcing fibers set in the evaluator, and when the resin is unmelted and cannot adhere onto the reinforcing fiber, the furnace temperature is increased 10° C. at a time until the resin melts to adhere the resin onto the reinforcing fiber, and the resin fused onto the reinforcing fiber is touched 4 times to adhere the resin and then allowed to stand for 1 minute, the number of μ-drops generated is counted, and calculation is performed using the following formula:
- μ-drop formation coefficient={number of μ-drops generated/4}×10.