Method of producing a molded article using a mold assembly with an insert block

The method of producing a molded article using a mold assembly comprising

• (A) a mold comprising a first mold member and a second mold member and having a structure in which a cavity for molding a thermoplastic resin to form a molded article is formed inside the mold at the time of closing the mold and the cavity is variable in volume at the time of forming the molded article,
• (B) an insert block formed of ceramic or glass having a thermal conductivity of 2.times.10.sup.-2 cal/cm-sec..degree.C. or less, said insert block being disposed inside the first mold member, the second mold member or the first and second mold members, constituting part of the cavity and having a thickness of 0.5 mm to 10 mm, and
• (C) a cover plate for covering a peripheral portion of the insert block, said cover plate being attached to the mold member in which the insert block is disposed, and constituting part of the cavity,
• wherein a clearance between the insert block and the cover plate is 0.001 mm to 0.03 mm, and an amount of overlapping of the cover plate and the insert block is at least 0.1 mm,
• said method comprising the steps of
• (a) closing the first mold member and the second mold member so as to make a cavity volume greater than a volume of the molded article to be produced,
• (b) injecting a molten thermoplastic resin to the cavity,
• (c) decreasing the cavity volume to the volume of the molded article to be produced, concurrently with the initiation of injection of the thermoplastic resin, during the injection, or after completion of the injection, and
• (d) cooling the thermoplastic resin in the cavity and then releasing a molded article from the mold.

The method of producing a molded article using a mold assembly comprising

• (A) a mold having a cavity, for producing a molded article from a thermoplastic resin,
• (B) a pressurized fluid introduction device,
• (C) an insert block formed of ceramic or glass having a thermal conductivity of 2.times.10.sup.-2 cal/cm.sec..degree.C. or less, said insert block being disposed inside the mold, constituting part of the cavity and having a thickness of 0.5 mm to 10 mm, and
• (D) a cover plate for covering a peripheral portion of the insert block, said cover plate being attached to the mold and constituting part of the cavity,
• wherein a clearance between the insert block and the cover plate is 0.001 mm to 0.03 mm, and an amount of overlapping of the insert block and the cover plate is at least 0.1 mm,
• said method comprising injecting a molten thermoplastic resin into the cavity, introducing a pressurized fluid from the pressurized fluid introduction device into the molten thermoplastic resin in the cavity, and then cooling the thermoplastic resin to solidify it, thereby to form a hollow portion inside the thermoplastic resin in the cavity.