JPH06166099A - Manufacture of transparent heat-resistant vessel - Google Patents

Abstract

PURPOSE:To provide a manufacture wherein releasing a product from a mold is easy and manufacturing cost is inexpensive, in manufacturing of a transparent vessel to be used for a microwave oven. CONSTITUTION:At the time of molding of a vessel of a transparent sheet which is a resin composition comprised of at least one kind of 10-100 pts.wt. polyethylene terephthalate resin and at least one kind of the 90-0 pts.wt. polyethylene terephthalate resin, has low crystallinity and is transparent sheet 2, the sheet 2 is preheated at a predetermined temperature and a mule mold 4 (or female mold 3) of a mold comprised of the male mold 4 and famale mold 3 is adjusted to a temperature lower than the glass transition temperature of the resin composition. Heat molding is performed further within the female mold 3 (or the male mold 4) by the mold whose female mold 3 (or male mold 4) is adjusted to a specific temperature, then the male mold 4 (or the female mold 3) is inserted into the female mold 3, the female mold 3 (or the male mold 4) is separated from the male mold 4 and cooling is performed by the male mold 4 (or the female old 3).

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 transparent heat-resistant container, and more particularly to a method for producing a transparent heat-resistant plastic container used in a microwave oven and a transparent heat-resistant container capable of heat sterilization and hot filling.

[0002]

2. Description of the Related Art Conventionally, fillers have been used as materials for one-way type plastic containers used in microwave ovens.
Polypropylene (PP) and crystallized polyethylene terephthalate (C-PET) are widely used, but most of these resins are opaque, and as a material for transparent blow molding containers, Amorphous polyethylene terephthalate (A-PET), polyvinyl chloride (PV
Resins such as C) are known, but these have the disadvantage of lacking heat resistance.

Examples of transparent and heat-resistant plastic materials include polyarylate (PAR), polycarbonate (PC) and polymethylpentene (TPX).
However, since containers made of these resins are usually manufactured by injection molding, it is difficult to manufacture a mold and costs are high compared to other molding methods. However, there is a problem that it is not suitable for manufacturing a one-way type container with a small sales lot.

Therefore, a vacuum molding method, a pressure molding method, a vacuum pressure molding method or a press molding method has been studied for such applications. Among the plastic materials used for this molding, polybutylene terephthalate is particularly preferable. Tartrate (hereinafter abbreviated as PBT) -based resin has excellent heat resistance and is relatively inexpensive compared to other engineering plastics, which is a cheaper polyethylene terephthalate (hereinafter abbreviated as PET). The mixed resin composition containing them is preferable for heat-resistant packaging materials, and the inventors of the present invention have also made a resin containing PBT-based resin and PET-based resin. A method has been proposed in which a composition is used as a raw material, and the composition is heat-molded in a heat-controlled mold (see Japanese Patent Laid-Open No. 4-63836).

[0005]

However, since this method uses a heating mold, it is difficult to peel it from the heating mold by an ordinary container molding method, and there is a disadvantage that the container is easily deformed at the time of peeling, and it is for C-PET. If you use a special molding machine that uses separate molds for heating and cooling, peeling can be done without problems, but this molding machine is expensive and at the same time the heating mold and cooling mold are Since they are located at different places, there is a drawback that the equipment area is large and the manufacturing space is not efficient.

[0006]

The present invention relates to a method for producing a transparent heat-resistant container which solves the above disadvantages, which comprises 10 to 100 parts by weight of at least one PBT resin and at least one kind of PBT resin. A resin composition comprising 90 to 0 parts by weight of PET resin is used to preheat a transparent sheet having a low degree of crystallinity to a temperature not lower than the glass transition point of the resin composition and lower than the cold crystallization temperature. A male mold (or a female mold) of a mold consisting of a female mold and a female mold is adjusted to a temperature lower than the glass transition point of the resin composition, and the female mold (or the male mold) is kept at a temperature equal to or higher than the cold crystallization temperature of the resin composition. , Adjust to a temperature lower than the melting point of the resin with the lowest melting point of the resin to be used, then first female (or male)
It is characterized by performing heat molding inside, then inserting or fitting the male mold (or female mold), separating the female mold (or male mold), and cooling with the male mold (or female mold). is there.

That is, as a result of various studies on the method for producing a container having excellent transparency and excellent heat resistance, the present inventors mold a resin composition comprising a PBT resin and a PET resin. At this time, the transparent sheet having a low crystallinity formed from this resin composition is preheated to a temperature not lower than the glass transition point of the resin composition and lower than the cold crystallization temperature, and then the male mold ( Or the female type) is adjusted to a temperature lower than the glass transition point of the resin composition, and the female type (or male type) is the resin having the lowest melting point among the resins to be used at the cold crystallization temperature of the resin composition or higher. Adjust to a temperature lower than the melting point of, heat mold in a female mold (or male mold) first,
Next, insert or fit the male mold (or female mold), pull the female mold (or male mold) apart, and cool with the male mold (or female mold), the molded product can be easily peeled from the mold. Therefore, it was found that the molded product can be obtained without deformation, and therefore the desired transparent heat-resistant container can be easily obtained, and the composition of the resin composition used here, preheating, molding temperature Research was advanced to complete the present invention. This will be described in more detail below.

[0008]

The present invention relates to a method for producing a transparent heat-resistant container, which comprises forming a film of a resin composition comprising a PBT resin and a PET resin, and applying the transparent sheet to the glass transition of the resin composition. Pre-heating to a temperature lower than the cold crystallization temperature above the point, and the male mold (or female mold) of this mold is adjusted to a temperature lower than the glass transition point of the resin composition, and a female mold (or male mold) is obtained. Is adjusted to a temperature lower than the cold crystallization temperature of the resin composition and lower than the melting point of the resin having the lowest melting point among the resins used, followed by heat molding with a female mold (or a male mold), and then a male mold ( Or the female mold) is inserted or fitted, and the female mold (or male mold) is separated and cooled by the male mold (or female mold). According to this, the molded product can be easily separated from the mold. Since it can be molded, the desired transparent heat-resistant container can be stored without deformation. Advantage is provided that can be obtained.

The present invention is to produce a transparent heat-resistant container by molding from a resin composition comprising PBT resin and PET resin. This resin composition contains less than 10 parts by weight of PBT resin, that is, PET resin. When it is more than 90 parts by weight, the proportion of the PBT resin is too small and the crystallization speed becomes slow, and it becomes difficult to crystallize in the heating mold,
This is composed of 10 to 100 parts by weight of at least one PBT resin and 90 to 0 parts by weight of at least one PET resin.

Therefore, as the resin composition, specifically, (a) 10 to 99 parts by weight of one kind of PBT resin and 90 to 1 parts by weight of one kind of PET resin, the total amount of resin is 100 parts by weight. , (B) one kind of PBT resin 0-99
A total resin amount of 100 parts by weight consisting of 100 parts by weight of one part of PBT resin having a slower crystallization rate than 100 parts by weight, (c) three or more kinds are selected from PBT resin and PET resin, The total amount of the resin composed of 10 to 100 parts by weight of the PBT resin and 90 to 0 parts by weight of the PET resin is 100 parts by weight, but at least one of them is crystalline. It is assumed to be a resin. The PBT-based resin or the PET-based resin may be either a homopolymer or a copolymer, but the polyvalent carboxylic acid shown in Table 1 Examples are valent alcohols.

[0011]

[Table 1]

The above-mentioned resin composition is formed into a sheet prior to forming a container, which is melt-extruded by, for example, an extruder and immediately cooled by a cooling roll immediately after being discharged from a T-die. The sheet may be formed into a sheet shape, and the formed sheet is solidified in a transparent state with low crystallinity by rapid cooling.

Further, the sheet is softened so that it can be expanded into a container shape for forming the container, which is preheated prior to the forming. However, since the preheating temperature is lower than the glass point transfer of the resin composition, the sheet cannot be sufficiently softened, and above the cold crystallization temperature, the sheet cannot be crystallized and stretched. The temperature above the glass transition point of the resin composition is lower than the cold crystallization temperature. The glass transition point and the cold crystallization temperature mean that a molded article having a low crystallinity is
It refers to the temperature that appears in the DSC curve when measured by SC, the glass transition point is the temperature at which the molded product softens, and the cold crystallization temperature is the temperature at which the molded product begins to crystallize.

Next, this sheet is a female type (or male type)
It is molded into a container inside, but if the temperature of this female mold (or male mold) is lower than the cold crystallization temperature of the resin composition, the container is not crystallized and has no heat resistance, If this temperature is equal to or higher than the melting point of the resin having the lowest melting point among the resins used, the container will be melted and the container cannot be molded. Therefore, the heating temperature of this female mold (or male mold) is the resin composition. The temperature is lower than the melting point of the resin having the lowest melting point among the resins used above the cold crystallization temperature.

Molding of a container from this sheet may be carried out in a female mold (or a male mold) kept at the above-mentioned temperature, which is then above the glass transition point of the resin composition. And the cooling is insufficient, which is not preferable, so that a male mold (or female mold) adjusted to a temperature not higher than the glass transition point of the resin composition is inserted or fitted, and a female mold (or male mold) heat-controlled is inserted. ) Is drawn in and cooled sufficiently by a male type (or female type).

Therefore, this container molding is performed, for example, by the method shown in FIG. FIG. 1 is a vertical cross-sectional view of a method for manufacturing a transparent heat-resistant container according to an embodiment of the present invention by a vacuum forming method. (A) shows a resin composition containing a PBT resin and a PET resin. A transparent resin sheet 2 made by extrusion molding or the like is heated to the above temperature by a heater-1 and placed on a heated female die, (b) is a female die raised to the sheet. Then, this is vacuumed to mold the molding container 5, (c) vacuumed by inserting a male mold into a female mold, (d) pulled down this female mold, (e) this male The figure shows that the molded container 5 is separated from the mold to collect the molded product.

However, in this case, when the proportion of the PBT resin contained in the resin composition is high, or when a PBT resin having a slow crystallization rate is used,
Since whitening may occur during preheating of container molding, at this time, cooling with a cooling roll is gradually cooled until the sheet does not lose transparency, or after film formation on the sheet. Annealing is required.

As a condition for this slow cooling, if the temperature of the cooling roll is set to a temperature lower than the glass transition point of the resin having the lowest glass transition point among the resins used, suppression of whitening during preheating of container molding is suppressed. Does not appear, and if the temperature is higher than 70 ° C, the cooling of the sheet is incomplete, which may cause peeling from the cooling roll and conveyance, so the temperature of this cooling roll is It is preferable to form a sheet by adjusting the temperature to 70 ° C. or lower, which is equal to or higher than the glass transition point of the resin having the lowest glass transition point among the resins used for the above.

When this is annealed, the roll, belt,
It may be carried out in a drying oven or the like, or it may be carried out off-line using an oven or the like, but the condition is that the resin having the lowest glass transition point among resins using temperatures such as rolls and ovens. A temperature above the glass transition point of the resin and below the glass transition point of the resin having the highest glass transition point among the resins used (when the PBT resin is 100 parts by weight, the temperature above the glass transition point is the cold crystallization temperature. Lower temperature). In the case of off-line, if the time is shorter than 1 minute, the effect of the anneal does not appear, and if it is longer than 500 hours, it is disadvantageous because it is too long.

According to the method of the present invention described above, this is P
Since the BT-based resin is used, the molded container has transparency and heat resistance, and in order to develop the heat resistance, a female mold (or a male mold) is used to form a male mold (or a male mold) after heat molding. (Female mold) makes it easy to separate this container from the mold, and since the heating and cooling are shared between the female mold and male mold, conventional molding machines can be used.
Compared with a molding machine in which heating and cooling are performed in different places, there is an advantage that the manufacturing space can be made more efficient.

[0021]

EXAMPLES Next, examples of the present invention will be given. Example 1 70 parts by weight of PBT resin / Duranex 600FP [trade name of Polyplastics Co., Ltd.] and PET resin / FFS-
A resin composition consisting of 30 parts by weight of 30M [trade name of Kanebo Co., Ltd.] was supplied to an extruder having a diameter of 40 mmφ, and 650 m
An m-width T die was attached, the temperature of the cooling roll was adjusted to 10 ° C., and a film having a thickness of 0.5 mm was formed. Then,
This sheet was preheated to a sheet temperature of 60 ° C. and then vacuum-molded in a female mold whose temperature was adjusted to 180 ° C. When the container was sufficiently crystallized, the vacuum was stopped. After inserting the male mold attached to the plug mounting part and vacuum piping and adjusted to 35 ° C, this time the male mold side is evacuated, the female mold is separated from the container, and the male mold is sufficiently cooled. A transparent heat-resistant container was obtained, and this container could be easily peeled from the mold without deforming the container, as compared with a container which was not cooled by a male mold.

Example 2 50 parts by weight of pellets of PBT resin / Duranex 600FP (described above) and PET resin / Dianite MA-53
A resin composition consisting of 50 parts by weight of OH [trade name of Mitsubishi Rayon Co., Ltd.] was supplied to a 40 mmφ twin-screw extruder, and 650
Attaching a T-die with a width of mm, the temperature of the cooling roll is 10 ° C
The film was formed into a sheet having a thickness of 0.6 mm. Then, this sheet was left in an oven at 40 ° C for 120 hours for annealing, and then preheated by a vacuum pressure air molding machine so that the sheet temperature was 70 ° C, and the plug was plugged. Insert the male mold attached to the mounting part and adjusted to 40 ℃,
Simultaneously with the plug assist, vacuum pressure forming was performed in a female mold heated to 180 ° C., and then the pressure was stopped while the vacuum was kept to separate the male mold. Then, when the container was fully crystallized, the vacuum was stopped, the male mold was inserted again, this time the male mold side was evacuated, the female mold was pulled away from the container, and the male mold was sufficiently cooled. A heat-resistant container was obtained, which could be easily peeled from the mold without deformation of the container, as compared with the case where cooling was not performed by the male mold.

[0023]

The present invention relates to a method for producing a transparent heat-resistant container, which comprises at least one PB as described above.
10 to 100 parts by weight of T-based resin and at least one PET
A transparent composition having a resin composition consisting of 90 to 0 parts by weight of a resin composition and having a low crystallinity is preheated at a temperature not lower than the glass transition point of the resin composition and lower than the cold crystallization temperature to obtain a male mold and a female mold. Resin in which the male mold (or female mold) of the mold consisting of and is adjusted to a temperature lower than the glass transition point of the resin composition, and the female mold (or male mold) is used at the cold crystallization temperature of the resin composition or higher. Adjust the temperature lower than the melting point of the resin with the lowest melting point, heat-mold in the female mold (or male mold) first, and then insert or fit the male mold (or female mold) into the female mold (or Male type)
It is characterized in that the male mold (or female mold) is separated to cool it. However, this uses a PBT resin with excellent heat resistance, so it has good transparency and excellent heat resistance. It is advantageous in that it is possible to easily obtain a container, and in this case, a molded product, which is difficult to peel from the mold by the usual method when molding the container, can be easily peeled using a conventional molding machine. Gender is given.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a molding apparatus using a vacuum molding machine showing an embodiment of the present invention, in which (a) is a transparent sheet set in a mold, (b), (c), (d). ) Is a molding method (e) of the molded product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heater 2 ... Transparent sheet 3 ... Female mold 4 ... Male 5 ... Molding container.

Claims (1)

[Claims] 1. A resin composition comprising 10 to 100 parts by weight of at least one polybutylene terephthalate resin and 90 to 0 parts by weight of at least one polyethylene terephthalate resin and having a low crystallinity. The transparent sheet is preheated to a temperature lower than the cold crystallization temperature above the glass transition point of the resin composition, and the male mold (or female mold) of the mold composed of the male mold and the female mold is formed into the resin composition. The temperature is lower than the glass transition point of, and the female type (or male type) is adjusted to a temperature lower than the melting point of the resin having the lowest melting point among the resins used above the cold crystallization temperature of the resin composition, First, heat-mold in the female mold (or male mold), then insert or fit the male mold (or female mold), pull the female mold (or male mold) apart, and cool with the male mold (or female mold). A method for manufacturing a transparent heat-resistant container, which is characterized by carrying out.