JPH07102608B2 - Method for manufacturing polyester molded products - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester article and a molding apparatus therefor, which is mainly a heat-resistant polyester obtained by vacuum molding or vacuum-pressure molding an unstretched amorphous sheet between heating dies. It aims to provide food containers at low cost.

[0002]

2. Description of the Related Art It has been already known that a polyester polymer such as a polyethylene terephthal sheet (hereinafter referred to as "PET") is superior in heat resistance and can be widely used as a container for high heat such as a microwave oven or an oven. In fact, there are many publications related to a manufacturing method and an apparatus for manufacturing a transparent molded product without brittleness from an unstretched or amorphous sheet obtained by uniformly blending the above-mentioned PET with a polyolefin at high heat. It is well known that

For example, in molding a PET sheet, in order to ensure good dimensional stability at high temperature, the PET in an amorphous state is oriented and a mold (for example, a female mold) is used to cause partial crystallization. The preferred heating temperature for) is 170 ° C.
It is described in JP-A-59-62660, etc., more specifically, the unstretched, amorphous PET sheet is preheated to the softening point, and another mold (in this case, (Male mold) to draw and biaxially orient, then transfer to a female mold for crystallization, and shrink back to a male mold heated to a temperature not higher than the glass transition temperature of PET, that is, 90 ° C to 100 ° C. It is disclosed in JP-A-58-89319.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the actual molding of the sheet, in either case, only one of the male and female molds in the molding machine (usually the female mold side) was provided with the vacuum or vacuum / pressure air molding function. Not only was the production efficiency extremely poor due to the complicated process such as the drawing of the unstretched sheet, the crystallization by the female mold, and the shrink back to the male mold, but as a mechanical device that can actually mold it. Was limited to expensive and large special molding machines.

Further, as in the prior art, drawing (pressing drawing ) ,
By means of relying only on the shrink back of the molded product to transfer the crystallized PET sheet from the female mold to the male mold, extremely high mold precision is required, and when the precision is low, wrinkles and white turbidity are seen in the product. However, there was a problem of reducing the product value.

[0006]

[Means for Solving the Problems] In view of such a situation,
As a result of earnest and repeated experiments on the PET sheet molding means, the present inventor has performed at least vacuum suction on both the male and female dies of a vacuum molding machine or a vacuum or compressed air molding machine that has been generally used for various plastic moldings. By retaining the function, the problem described above is completely solved.

That is, the present invention relates to a preheating step of preheating an unstretched and amorphous PET sheet to a high temperature sufficient for softening the PET sheet, and a crystallization start temperature (hereinafter referred to as a crystallization start temperature) measured by a differential scanning calorimeter of the PET sheet. , Simply referred to as “crystallization start temperature”), that is, an initial molding step of vacuum suction into a female mold (or male mold) heated to 160 ° C. to 180 ° C., and a crystallization start temperature of the sheet previously in the female mold. Below, namely 80 ° C to 10
The male mold (or female mold) heated to 0 ° C. is fitted and drawn, and then the drawing and crystallization process of crystallizing and the suction of the female mold are stopped, and at the same time the male mold is given a suction action. A means was adopted in which the molded body was transferred to a male mold and a cooling process of opening both molds was adopted.

Further, according to the present invention, as a molding apparatus, a vacuum suction function can be applied to both the male and female dies in a normal plastic vacuum molding machine or a vacuum or pressure air molding machine having male and female dies that can be fitted together and heated. Was used.

Further, a means of providing a compressed air pressing function on each of the above-mentioned molds was used.

[0010]

According to the present invention, by providing at least a vacuum suction function on both male and female molds, the conventional method which relies only on shrinkback to transfer the molded product whose crystallization has been completed to the male mold, It is possible to perform forced transfer by suction of the mold, and in addition to the special effect that the product can be cooled at a temperature below the crystallization start temperature while being restrained by the male mold, its expansion, crystallization and cooling can be performed in the same process. Also has.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be described in more detail below with reference to the process drawings and block diagrams in accordance with the first and second embodiments.

(First Example) In FIGS. 1 to 4, 1 is an unstretched amorphous PET sheet having a thickness of 1.0 mm, and 2 is the P
A female mold having a vacuum suction function, which is heated to 170 ° C. which is higher than the crystallization start temperature of the ET sheet, and 3 is a male type which is heated to 90 ° C. which is also lower than the crystallization start temperature and can be moved up and down. Like the above-mentioned female mold, it has a suction function.

By the way, the male and female molds 2 separated from each other
-Vacuum suction of the PET sheet 1 (see FIG. 1) that has been completely softened by being preheated to about 100 ° C. (below the crystallization start temperature) by being moved by a transfer device (not shown) between 3 and to the female mold. The initial vacuum molding is performed with (see Fig. 2). Next, the male die 3 is lowered and fitted into the female die, so that the PET sheet 1 is drawn and biaxially oriented, and the PET sheet 1 is crystallized when continued for 2 to 3 seconds. (See FIG. 3), the suction of the female die 2 is stopped, and simultaneously the male die 3 is switched to the vacuum suction to force the molded body 1 ′ strongly adhered to the female die 2 to the male die 3 side. (See FIG. 4). As a result, the molded body 1'is brought into close contact with the male mold 3 due to the fact that the suction force of the male mold interacts with its own shrinkback performance, so that the male mold 3 is raised (the same applies even when the female mold is lowered). By allowing the mold to cool, waiting for the molded body to solidify, and pulling it out of the male mold 3, the desired molded product can be obtained easily.

(Second Example) This example is the same PE as above.
In obtaining a molded product from the T-sheet 1, according to the process sequence shown in FIGS. 1 to 4, each of the male and female molds 2 and 3 is further provided with a compressed air injection function of 0.7 to 1.0 kg / cm ² . In addition to the vacuum suction of the female mold 2 in addition to the vacuum suction of the female mold 2 in the initial molding of the preheated and softened PET sheet, the initial molding can be more efficiently performed by pressing the compressed air released from the male mold 3. (See FIG. 2) In addition, during the cooling step of transferring the molded body 1 ′ attached to the female mold 2 to the male mold 3, the vacuum suction and the compressed air pressing function of the molds are switched substantially at the same time, so that the molded body is Is reliably transferred to the male mold by the combined effect of the male suction force, the pressing force from the female mold, and its own shrinking properties (see Fig. 4), and the male mold is cooled to obtain a molded product. The whole molding time until it is made shorter than that of the first example It is now possible.

In each of the above embodiments, the mold for heating above the crystallization start temperature of the PET sheet was a female mold. However, in the method and apparatus of the present invention, the reverse method, that is, the male mold is initially used. Needless to say, even if a molding die is used and the cooling step is performed using a female die, a completely equivalent molded product can be obtained.

[0016]

As is clear from the above description, the apparatus of the present invention is not limited to the conventional expensive and large-sized special molding machine, but the conventional vacuum molding machine which has been generally used or Not only can the economical effect that polyester molded products can be provided at low cost simply by modifying one of the molds of the vacuum and air pressure molding machines and imparting suction or pressure air injection functions to both molds, By equipping each mold with vacuum suction function and / or vacuum and pressure molding function, the manufacturing process can be remarkably simplified, and the accuracy and production efficiency of molded products can be improved and the product cost can be greatly reduced. It is possible to bring remarkable profits such as.

[Brief description of drawings]

FIG. 1 is a process diagram showing a preheating process for heating and softening a PET sheet.

FIG. 2 is a process diagram showing an initial molding process of vacuum suctioning a PET sheet into a female mold.

FIG. 3 is a process diagram showing a drawing and crystallization process.

FIG. 4 is a process chart showing a cooling process of a molded body.

FIG. 5 is a block diagram showing a manufacturing process.

[Explanation of symbols]

 1 PET sheet 2 Molded body 3 Female type 4 Male type

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shunichi Yoshioka 1-chome 1-10, Sachimachi, Naniwa-ku, Osaka City, Osaka (72) Inventor Kazuyoshi Yamada 6-16-3 Isokami-cho, Kishiwada-shi, Osaka Yamada Kosakusho Co., Ltd. (56) References JP-A-54-10367 (JP, A) JP-A-1-263024 (JP, A)

Claims (3)

[Claims] 1. A preheating step of heating an amorphous sheet of polyethylene terephthalate to a high temperature sufficient for its softening, and vacuum suction to one of male and female molds which has heated the sheet to a temperature higher than a crystallization start temperature. The initial molding step and the other mold preheated to the crystallization starting temperature or lower in the mold are fitted to each other to draw the sheet, and then the sheet is crystallized. And a cooling step of simultaneously separating the two molds while simultaneously applying a vacuum suction action to the other mold. 2. The method for producing a polyester molded article according to claim 1, wherein a vacuum molding machine provided with a vacuum suction function is used for both the male and female molds. 3. The method for producing a polyester molded product according to claim 1, wherein at least one of the male and female dies is performed by using a vacuum / compressed air type molding machine having a molding function by vacuum and compressed air.