Tohoku Munekata Co., Ltd

Munekata Co., Ltd.

Hirofumi Tateyama

Kiyoshi Sasaki

Hiroshi Katsuta

Kiyoshi Suzuki

Yasumasa Sugiyama

Atsuhiro Suzuki

Yuuji Umino

Kazuyuki Ushizaka

Atsushi Tsuchiya

Hideyuki Ishiyama

Tsuyoshi Kato

A molding method providing a homogeneous surface without any patch by dyeing or reforming a resin surface in a die concurrently to molding, in injection-, blow-, or compression molding, after thermoplastic resin is filled in a die cavity. After blow-molding, or after compression molding, mixture gas of carbon dioxide gas and a dye, or mixture gas of carbon dioxide gas and a reformer is injected between the resin and the die for forming a clearance, and pressure of the mixture gas is kept at a constant level. The mixture gas is dissolved in a molded surface, and a pressure is applied to contact the molded surface to the cavity face. The mixture gas in the clearance is exhausted and cooled, and the molded product is taken out. A dye-permeated layer or a reformer-permeated layer is formed on a surface of the molded product.

Method of dyeing or reforming injection, blow or compression molding

In the filling step, the forward movement speed of the screw is controlled in accordance with a predetermined speed pattern until the screw reaches a deceleration initiation point, LS B. After the screw reaches LS B, a deceleration step is started. In the deceleration step, the forward movement speed of the screw is controlled in a feedback manner such that the internal pressure of the mold reaches a predetermined target pressure. When the screw reaches a pressure holding initiation point, LS (or pressure holding initiation time, TR ), the pressure holding step is started. In the pressure holding step, the target pressure, which is a function of time, is changed with time in accordance with a program. When the operation goes to the pressure holding step, the set of PID coefficients within the feedback control loop are replaced by different set of PID coefficients.

Method for controlling the forward movement speed of the screw in an injection molding machine

The present invention provides an injection molding method for providing a molded product with excellent transcription and an excellent gloss level. In this method, immediately after a resin is filled in a cavity ( ), a carbon dioxide gas is injected or the skin layer is moved back to form a space ( ) between the resin and the die surface ( ), so that growth of the skin layer is hold down, and at the same time the carbon dioxide is dissolved in the skin layer for lowering the glass transition point of skin layer. Then the skin layer is again closely cohered to a surface of the die by increasing the resin pressure and cooling the molded product for solidifying behind the holding pressure. With this method, products with excellent transcription and with an excellent surface gloss level can be obtained.

Resin and gas injection molding method with subsequent cohering

If the surface of metallic mold should not be highly transcribed to the surface of product in injection molding the plastic products, the transcription defects such as weld, shrinkage, etc. are caused to the surface of product. Further, if the resin should be exposed to the surface of high temperature metallic mold more than necessary during the molding, the filler and the like of glass and so forth are contained into the resin, and in this case, they are left over on the surface of metallic mold, resulting in the transcription defect. These problems can be solved by heating the surface temperature of metallic mold higher than the glass transfer temperature of resin if the resin is non-crystal and higher than the fusion point temperature if the resin crystal, with the temperature raising speed of more than 2&deg; C. every second, maintaining this temperature during the resin charging, and by cooling at the lowering speed of more than 2&deg; C. every second after the completion of charging. This temperature control shall be conducted with the feed back control while detecting the surface temperature of metallic mold by the temperature detection sensor mounted at the position close to the surface of metallic mold.

Method for injection molding of plastic products having excellent transcription properties

Growing community of inventors

Fukushima, Japan

Hirofumi Tateyama