JPH05278058A - Molding method for synthetic resin - Google Patents

Abstract

PURPOSE:To obtain a molding method in which a thick-wall molded piece, esp., by low-foam molding can be cooled in a short time related to a synthetic resin injection molding method. CONSTITUTION:A molding machine consists of a device 2 for supplying a gaseous body to a mold device 1; a device 3 for causing the mold device 1 to exhaust the gaseous body from the mold device 1; a product cavity 1a where a synthetic resin is injected into the mold device 1 to be molded; and a gaseous body flow path 1c which is disposed along the product cavity 1a so as to be connected to the product cavity 1a, the gaseous body supply device 2, and the exhaustion device 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin injection molding method, and more particularly to a molding method suitable for a thick molded article such as low foam molding.

[0002]

2. Description of the Related Art A conventional molding method is disclosed in JP-A-62-645.
As described in No. 18, the gas body is supplied to the mold device only once before injection of the synthetic resin and exhausted only once after the injection.

[0003]

The above-mentioned prior art does not take into consideration the cooling of the synthetic resin after the completion of injection and inflow, and in particular, a thick-walled molded product such as a low-foaming molded product, that is, a smooth molded product. A molded product composed of an unfoamed outer shell on the surface and a foam-expanded core has a problem of long cooling and solidification time.

It is an object of the present invention to cool and solidify a synthetic resin after injection and inflow in a short time.

[0005]

The above object is to provide a device for supplying a gas body to a mold device and a device for discharging a gas body from the mold device independently of each other, and the mold device is provided with a synthetic resin. A product cavity that is injected into the product to form a molded product, and a gas body flow path that is located around the product cavity and that communicates with the product cavity and the gas body supply device and discharge device, and pressurizes by supplying the gas body Inject synthetic resin into the cavity, discharge the gas body from the product cavity during or after the injection injection to communicate the product cavity below atmospheric pressure, and then re-inject the gas body into the gas body flow path of the mold device. This is achieved by continuously supplying and discharging the gas body at the same time.

[0006]

The gas body supplied under pressure to the closed type product cavity by the gas body supply device has a function of suppressing foaming or the like on the resin surface at the time of injection injection of the synthetic resin containing the foaming agent or the like. When the gas body is exhausted from the product cavity by the gas body exhausting device during or after the injection injection to make the product cavity communicate with the atmospheric pressure or below, foaming or the like occurs in the synthetic resin to obtain a desired molded product. After that, again, the gas body is continuously supplied to the gas body flow path of the mold apparatus by the gas body supply device, and at the same time, the gas body is discharged by the gas body exhaust device. That is, when the gas body is made to pass through the inside of the mold device, the mold device is cooled by the gas body, and the synthetic resin is cooled accordingly.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The mold apparatus 1 is provided with a closed product cavity 1a. The product cavity 1 a communicates with the injection nozzle 4. Further, the gas body flow path 1c located around the product cavity is also communicated with the gas body flow path 1c through the vent 1b. The gas body flow path 1c communicates with the gas body supply device 2 and the gas body exhaust device 3.

Next, the operation will be described.

The closed product cavity 1a is pressurized and filled from the gas body supply device 2 through the gas body flow passage 1c and the vent 1b. At this time, the gas body exhaust device 3 does not operate, and the gas body is held in the product cavity 1a.

Next, the supply of the gas body is stopped and the injection nozzle 4 injects and injects the synthetic resin containing the foaming agent into the product cavity 1a. At this time, the foaming agent in the synthetic resin is suppressed by the pressure of the gas body in the product cavity 1a.

Next, when the product cavity 1a is almost completely filled with the synthetic resin, or when the product cavity 1a is completely filled, the gas exhaust unit 3 is operated to operate the product cavity 1a.
The gas body therein is opened to the atmosphere via the vent 1b and the gas body flow path 1c. The vent 1b has a size that allows a gas body to pass therethrough but does not allow a synthetic resin to pass therethrough.

When the product cavity 1a is at atmospheric pressure, the foaming agent in the synthetic resin foams, and a low-foam molded product composed of an unfoamed outer shell having a smooth surface and a foam-expanded core is obtained.

Next, the gas body is continuously supplied again to the gas body flow passage 1c from the gas body supply device 2 and is exhausted by the gas body exhaust device 3, so that the gas body continuously flows through the gas body flow passage 1c. It is possible to cool down the mold device and cool the synthetic resin molded product in the product cavity 1a accordingly.

The mold device is cooled by cooling water (not shown)
May be done at the same time.

According to the present invention, since the synthetic resin can be cooled by the gas body, there is an effect that a thick low-foam molded article can be cooled and solidified in a short time.

[0016]

According to the present invention, in the injection molding method of synthetic resin of the type in which the closed mold device is pre-pressurized with the pressurized gas body before the injection of the molding material, the pre-pressurization gas body is used. Since it can be used for cooling the synthetic resin, it has an effect of shortening the molding time, that is, improving the molding productivity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold, 1a ... Product cavity, 1b ... Vent, 1c ... Gas body flow path 2 ... Gas body supply device, 3 ... Gas body exhaust device, 4 ... Injection nozzle.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29C 45/73 6949-4F 45/74 8824-4F // B29K 105: 04

Claims (1)

[Claims] 1. An injection molding method of synthetic resin of a type in which a closed mold device is pre-pressurized with a pressurized gas body before injecting a molding material, a device for supplying a gas body to the mold device, and the mold. A device that discharges a gas body from the mold device is provided independently, and a product cavity that is a synthetic resin is injected into the mold device to form a molded product, and a product cavity and a gas body that are located around the product cavity Providing a gas body flow path that communicates with the device and the discharge device, the synthetic resin is injected and injected into the product cavity pressurized by the supply of the gas body, and the gas body is discharged from the product cavity during or after the injection injection and the product cavity To the atmospheric pressure or less, and then, in the cooling step of the synthetic resin, the gas body is continuously supplied again to the gas body flow path of the mold device, and at the same time, the gas body is discharged. Molding method of fat.