Process for producing molded item of thermosetting resin and injection molding machine therefor

Abstract

A process for producing a molded item of thermosetting resin, and injection molding machine therefor, capable of preventing burring and bubble inclusion at molding operation. There is provided a process for producing a molded item of thermosetting resin with the use of a mold having a cavity for forming a product part, a gate forming a gate part, a runner forming a runner part and an overflow catcher communicating with the cavity and forming an overflow part, which process comprises the injection step of injecting a liquid resin until filling the region from the runner through the gate to the cavity and further the region from the cavity to the overflow catcher; the hardening step of heating the liquid resin within the mold so as to effect hardening; the demolding step of detaching a resin molded item having the runner part, gate part, product part and overflow part from the mold; and the cutting step of cutting the gate part and overflow part off the product part of the demolded resin molded item.

Description

[0001] Technical division [0002] The present invention relates to a method of manufacturing a molded article made of a thermosetting resin and an injection molding apparatus for molding a molded article made of a thermosetting resin by liquid resin injection molding. Background technique [0003] In general, injection molding is known as a method of molding plastic products (or parts). In addition, in the case of injection molding a thermosetting resin, there is known a liquid resin injection molding method (LIM: Liquid Injection Molding), which injects a liquid thermosetting resin (liquid raw material resin, hereinafter sometimes referred to as liquid resin) into a high-temperature mold. Then it is heat cured. This method is a molding method in which liquid raw material resin is injected into a high-temperature mold and then heated and solidified. [0004] In addition, in order to prevent the gas in the cavity of the mold from remaining in the molded product when injectin...

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Problems solved by technology

[0005] Here, when the viscosity of the raw material resin is high during injection molding, even if a large-diameter vent hole is provided for sufficient gas removal, the raw resin with high viscosity will not enter the vent hole; In the resin injection molding method, the viscosity of the raw material resin is low, so if the hole diameter of the vent hole is increased, there is a problem that the raw material resin flows into the vent hole, and burrs formed by the resin flowing into the vent hole tend to be formed on the molded product.

Therefore, it is necessary to remove the burrs after molding, but there is a problem that it takes time to remove the burrs

[0006] In addition, if the diameter of the vent hole is reduced to prevent burrs, it may be difficult to completely remove the gas, resulting in air bubbles in the molded product, resulting in a decrease in the strength and quality of the molded product

In particular, when the molded product (product part) is an optical part, if air bubbles are contained inside, there is a problem that desired optical characteristics cannot be obtained

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