JPH0668817U - Polyester moldings - Google Patents

Abstract

(57) [Summary] [Purpose] To provide high-quality and inexpensive polyester molded products. [Structure] When shifting to the cooling step, a molded product P is obtained by a molding method in which a vacuum is drawn from the male mold 3 side.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a polyester molded product, and more particularly to a heat resistant polyester molded product used for various food containers, disposable containers, packaging containers or toys, signboards and the like.

[0002]

[Prior art]

 BACKGROUND ART Polyester polymers such as polyethylene terephthalate (hereinafter referred to as “PET”) have been excellent in heat resistance and have been widely used as heat-resistant food containers for microwave ovens and ovens. Further, not only heat resistance, but also cold resistance, oil resistance, gas barrier property, etc. are excellent, and since it is light and durable, the PET sheet has a wide range of applications.

For example, Japanese Patent Laid-Open No. 59-62660 discloses an example of such a PET sheet product, and its molding method is also clarified. According to the publication, in order to ensure good dimensional accuracy at high temperature when forming a PET sheet, the amorphous PET is oriented, and in order to cause partial crystallization, a die (for example, It is described that the heating temperature of (female mold) is preferably 170 ° C to 190 ° C.

Further, in Japanese Patent Laid-Open No. 58-89319, an unstretched, amorphous PET sheet is preheated to a softening point and drawn by another die (in this case, a male die) to be biaxially stretched. Regarding the thermally formed PET article obtained by orienting, transferring to a female mold and crystallizing, and shrink-backing this to a male mold heated to a temperature not higher than the glass transition temperature of the PET sheet, that is, 90 ° C to 100 ° C. There is a description.

[0005]

[Problems to be solved by the device]

 However, in the actual molding of these PET sheets, in either case, only one (usually the female mold side) of the male and female molds in the molding machine had the vacuum molding function or the vacuum / pneumatic molding function. It didn't pass. Therefore, not only was the production efficiency extremely poor due to the complexity of the process, such as the need to draw an unstretched sheet by the male mold, crystallization by the female mold, and shrink back to the male mold, and actually The machinery and equipment that can be used for forming the mold was limited to expensive and large special molding machines. Therefore, there was a problem that the product cost was high.

In addition, as described above, when the transfer of the drawn and crystallized PET sheet from the female mold to the male mold is dependent only on the shrink back of the molded product, extremely high mold precision is required. When the accuracy is low, wrinkles and white turbidity are observed in the product, and the product quality deteriorates.

That is, the conventional polyester molded product is expensive and large in cost because it is manufactured in a complicated process by a large apparatus, and it is difficult to stably obtain high quality.

The present invention has been made in view of such circumstances, and an object thereof is to provide a high-quality and inexpensive polyester molded product.

[0009]

[Means for Solving the Problems]

 The present invention has means for solving the above-mentioned problems as follows. That is, in the polyester molded article of the present invention, an amorphous sheet of polyethylene terephthalate softened by preheating is vacuum-sucked into one of the molds heated above the crystallization start temperature of the sheet, and the sheet is preliminarily heated. The other mold heated to the crystallization start temperature or less is fitted to the one mold and the sheet is drawn and continuously crystallized, and then the vacuum suction of the one mold is stopped, while the other mold is stopped. It is obtained by moving the sheet to another mold while applying a vacuum suction action to the mold to separate the two molds, and cooling the sheet while restraining the sheet with the other mold. There is.

[0010]

[Operation] A vacuum suction action is applied to both molds, and by vacuum suction from the other mold side at the time of transition to the cooling step, one mold of the molded body in which crystallization has been completed is transferred to the other mold. Is easily and reliably transferred to the mold, and the molded product is cooled at a temperature below the crystallization start temperature while being constrained by the other mold, resulting in a marked improvement in molding accuracy and the formation of wrinkles and cloudiness. Occurrence is avoided. In addition, companding, crystallization and cooling can be efficiently performed in a series of working steps with a relatively simple device, and the product cost can be significantly reduced.

[0011]

【Example】

 An embodiment of the polyester molded product of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of a standard container made of a polyester molded product of the present invention, showing a food container P with a lid. This food container P has heat resistance (up to 230 ° C) that can withstand use in microwave ovens and gas oven ranges, and also has excellent cold resistance (up to -25 ° C), and other oil resistance. In addition, it has gas barrier properties, is light and durable, and has the features of a conventional PET sheet, such as a ceramic-like appearance and a high-class appearance. Depending on the molding method, there are no wrinkles or cloudiness, and it is much cheaper and has a higher shape accuracy than conventional products.

2 to 5 are views for explaining a molding process, in which the reference numeral 1 denotes a thickness 1. A 0 mm unstretched and amorphous PET sheet, 2 is a female mold having a vacuum suction function heated to 170 ° C. above the crystallization start temperature of the PET sheet, and 3 is also below the crystallization start temperature. It is a male type that is heated to a certain temperature of 90 ° C. and can be moved up and down, and has a suction function like the female type.

Explaining the molding process, first, the PET sheet 1 is separately moved by a transfer device (not shown) between the female mold 2 and the male mold 3 that are separated from each other (see FIG. 2). The PET sheet 1 is preheated to about 100 ° C. (below the crystallization start temperature) to be completely softened, and the PET sheet 1 is vacuum sucked into the female mold 2 to perform the initial vacuum molding (see FIG. 3).

Next, by lowering the male mold 3 and fitting it into the female mold 2 (see FIG. 4), the PET sheet 1 is expanded and biaxially oriented, and heated for 2-3 seconds as it is. Then, the crystallization of PET sheet 1 is completed.

Then, when the crystallization is completed, the suction of the female die 2 is stopped and the vacuum suction of the male die 3 is started to force the molded body 1 ′ strongly adhered to the female die 2 to the male die. Move to side 3 (see Figure 5). As a result, the molded body 1 ′ comes into close contact with the male mold 3 due to the suction force of the male mold 3 and its own shrink back characteristics acting together, so that the male mold 3 is raised (even if the female mold 2 is lowered). The molded body 1 ′ is cooled under the constraint of the male mold 3, is allowed to solidify, and is then pulled out from the male mold 3 to obtain a high-quality molded product P.

As described above, when the molded body 1 ′ attached to the female mold 2 is moved to the male mold 3, vacuum suction is performed from the male mold 3 side, so that the mold release from the female mold 2 is extremely easy. It becomes easy and reliable, and the molded body 1'is cooled at a temperature below the crystallization start temperature while being restrained by the male mold 3. Therefore, the molding accuracy is significantly improved, wrinkles and white turbidity are avoided, and high quality molded products can be obtained.

Further, the drawing, crystallization and cooling can be efficiently performed in a series of working steps by a device simpler than the conventional one, and the product cost is remarkably reduced.

By the way, in order to perform molding more efficiently, while the vacuum suction is performed by the female die 2, compressed air jet is applied from the male die 3 to the PET sheet 1, and the vacuum suction is performed by the male die 3. It is also possible to apply compressed air injection from the female mold 2 to the molded body 1'during this.

In the molding method described above, the mold for heating above the crystallization start temperature of the PET sheet 1 was the female mold, but the reverse method, that is, the male mold was the initial molding mold, and was cooled by the female mold. It goes without saying that even if the steps are carried out, a completely equivalent molded product can be obtained.

Needless to say, the present molded article is not limited to food containers but can be widely used in disposable containers, packaging containers, toys, signboards, and the like.

[0021]

[Effect of device]

 As described above, the polyester molded product of the present invention is molded by an efficient molding method in which vacuum suction is performed from the other mold side even when shifting to the cooling step, so there are no wrinkles or cloudiness, In addition to being high in shape accuracy and high quality, it can be obtained at a much lower cost than conventional products. It is needless to say that the present invention does not limit the shape and usage of the molded product to those of the embodiment, and these may be set appropriately.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a standard container for a polyester molded product of the present invention.

FIG. 2 is an explanatory view showing the preheating step.

FIG. 3 is an explanatory view showing the initial molding step.

FIG. 4 is an explanatory view showing the same crystallization step.

FIG. 5 is an explanatory view showing the same cooling step.

[Explanation of symbols]

 1 ... Amorphous sheet, 2, 3 ... Mold.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shunichi Yoshioka 1-10, Sachimachi, Naniwa-ku, Osaka City, Osaka Prefecture Yoshida Co., Ltd. Yamada Manufacturing Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. An amorphous sheet of polyethylene terephthalate softened by preheating is vacuum-sucked into one of the molds heated above the crystallization start temperature of the sheet, and the crystallization start temperature of the sheet is kept below the crystallization start temperature. The other mold heated is fitted to the one mold, the sheet is drawn and continuously crystallized, and then the vacuum suction of the one mold is stopped, while the vacuum suction action is applied to the other mold. A polyester molded article obtained by moving the sheet to the other mold while separating the two molds, and cooling the sheet while restraining the sheet with the other mold.