Method of producing glass-fiber-reinforced thermoplastic resin molded object and glass-fiber-reinforced thermoplastic resin molded object obtained by the method

A method of producing a glass-fiber-reinforced polyamide-based resin molded object, comprising:

• directly loading a polyamide-based resin and glass fiber chopped strands subjected to a surface treatment with at least one of a urethane-based sizing agent and an acrylic urethane-based sizing agent, the glass fiber chopped strands each having a fiber length of from 1.2 mm to 1.8 mm into an injection molding machine, and
• injection molding thereof to provide a glass-fiber-reinforced polyamide-based resin molded object,
• wherein the polyamide-based resin molded object has dispersed therein fibrous fillers including glass fibers,
• wherein the content of all glass fibers in the glass-fiber-reinforced polyamide-based resin molded object is from 25 wt. % to 65 wt. %,
• wherein the glass fibers in the glass-fiber-reinforced polyamide-based resin molded object have a fiber length described in the following (A) to (D), and are dispersed at ratios with respect to a total number of the fibrous fillers described in the following (A) to (D), and
• wherein, in the glass-fiber-reinforced polyamide-based resin molded object, a property described in the following (β) is satisfied together with a physical property described in the following (α):
• (A) 0.05 mm or more and less than 0.3 mm:
• from 30% to 60%;
• (B) 0.3 mm or more and less than 0.6 mm:
• from 30% to 60%;
• (C) 0.6 mm or more and less than 1.2 mm:
• from 3% to 20%;
• (D) 1.2 mm or more:
• 0% or more and less than 1%;
• (α) the glass-fiber-reinforced polyamide-based resin molded object has, when formed as an ISO multipurpose dumbbell by injection molding, a tensile strength (MPa) under an atmosphere at 25° C. of more than a value Y (MPa) represented by the following equation (1):
• Y=−0.05X2+6X+70 (1)
• where X represents a content (wt. %) of all the glass fibers in the glass-fiber-reinforced polyamide-based resin molded object;
• and
• (β) unopened glass fibers are absent on a surface of a plate material, the plate material being obtained by forming the glass-fiber-reinforced polyamide-based resin molded object by injection molding as the plate material measuring 170 mm long by 50 mm wide by 12 mm thick.