JPH0710692B2 - Heat resistant container - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a transparent heat-resistant container suitable as a container for contents that require heat sterilization during filling of fruit juice beverages and the like.

(Prior art and problems) Conventionally, a biaxially stretched blow container made of polyethylene terephthalate resin has been used as a container for fruit juice beverage, but since the contents are sterilized at high temperature and filled,
The production thereof requires various heat resistance steps, and the cost thereof is high.

For example, a method has been proposed in which the mouth of the container is crystallized and whitened to make the mouth heat resistant (Japanese Patent Publication No. 59-3310).
1) However, the whitening requires long-time holding at the crystallization temperature, it is difficult to secure the dimensional accuracy of the mouth, and it is necessary to devise various measures to seal the mouth with a cap. In addition, if you do not apply such heat resistance, fill the contents of the container at a high temperature (for example, 85 ° C), and sterilize the container, and then lay the container on its side to sterilize the mouth, the heat resistance of the neck of the mouth will be reduced. Due to the lack, the cap and the neck of the container are loosely fitted and often cause liquid leakage. In addition, a multi-layered structure in which a heat-resistant resin layer is provided in order to impart heat resistance to the container has also been proposed, but since the container body portion also has the heat-resistant resin layer, it has excellent transparency. Even when a polyethylene terephthalate resin or the like is used, its transparency is impaired, which makes it unsuitable as a container for storing products requiring transparency, and there is a problem that its application range is restricted.

(Means for Solving Problems) The present invention has been conceived in order to solve the above problems of the prior art, in which both the inner and outer surface layers of the neck of the container are coated with polyethylene terephthalate resin, and a heat-resistant intermediate layer is used. It is characterized in that it is formed of a resin layer mainly composed of a conductive resin, and the body of the container is formed of a polyethylene terephthalate resin alone. The polyethylene terephthalate applied to the outer layer (1) and the inner layer (3) in FIG. 1 may be any resin suitable for ordinary biaxially stretch blow molding.
A value (fixed viscosity) of 0.5 or more is preferable. Further, since this polyethylene terephthalate resin is mainly used for the body of the container, the blow mold is heated to about 100 ° C during stretch blow molding, and heat setting after stretch molding is performed for 10 to 50 seconds, and the residual A step of removing stress and increasing the heat resistance of the container may be taken.

On the other hand, a resin having sufficient heat resistance is used as the intermediate layer (2) of the container neck, and when the container is filled with the heated contents, and after capping, it is laid over and sterilized to perform internal sterilization, the cap and the neck of the container mouth are closed. Make sure that there is no accident such as weak fitting and leakage of contents. The first condition is that the resin that can be used as the intermediate layer (2) has good adhesion to the polyethylene terephthalate used as the outer layer (1) and the inner layer (3), and if the adhesion is weak. When the material itself has good heat resistance, the interface with polyethylene terephthalate becomes weak, and heat resistance as a container cannot be ensured. Examples of the resin having heat resistance and having good adhesion to the polyethylene terephthalate resin include polycarbonate resin, aromatic polyester carbonate, wholly aromatic polyester, and the like. These resins may be used alone or in a mixture of two or more kinds, or polyethylene. A mixture with a terephthalate resin can be used as the intermediate layer (2). In addition, polyetherketone resin, polyethersulfone resin, and the like, which are known as heat-resistant materials, may be usable by mixing with a polyester resin.

In producing the container of the present invention, a small amount of polyethylene terephthalate resin is first injected into a cavity for molding the bottomed parison (4) by a multi-stage two-color injection molding machine, and then a heat-resistant resin to be an intermediate layer. The layer is injected from the second cylinder, and then the polyethylene terephthalate resin corresponding to the body of the container is injected again, and the bottomed parison is molded so that its cross section becomes as shown in Fig. 1. Biaxially stretch blow to form a container. This time,
Since the body of the container is thin and residual stress is likely to remain when it is stretch-blown, it is necessary to remove this residual stress and prevent deformation of the container when heat-filled as much as possible. Therefore, the blow molded container has a mold temperature of about 100 ° C.
Hold the heat for 10 to 50 seconds to remove residual stress, then cool and remove from the mold. Here, it is preferable to devise the shape of the body of the container so that it can cope with the reduced pressure deformation after heat filling. Further, if the ratio of the thickness of the middle layer of the neck to the total thickness of the neck is small, it does not contribute to the improvement of heat resistance.
The thickness of the intermediate layer is 30 to 90% because the intermediate layer may be exposed if the thickness exceeds 30% of the total thickness and if it exceeds 90% of the total thickness. Is preferred.

<Example 1> Using a multi-stage two-color injection molding machine, the outermost and innermost layers of the bottomed parison neck, the bottom bottom of the bottomed parison were polyethylene terephthalate resin (IV = 0.65), and the bottomed parison neck middle layer was a polycarbonate resin layer. (Contains 2% transparent dye)
Make a bottomed parison with a thickness of 1.7 m in the middle layer of the neck.
m, the inner and outer layers of the neck are 0.4 mm, the bottomed parison body is 3.5 mm thick, and the bottomed parison is about 110 mm.
The temperature was adjusted to 0 ° C., and stretch blow molding was performed in the longitudinal and transverse directions to obtain 1 self-supporting container. The average thickness of the body of this container is about 370
It was μ. The blow mold of this container had a mold surface temperature of about 100 ° C., and was heated and pressed for about 40 seconds while applying a blow pressure to remove residual stress during stretching. Further, when the container was taken out from the mold, the mold was cooled to sufficiently lower the temperature of the container. Fill the container obtained as described above with hot water of 85 ° C, fit it on the neck of the mouth with an aluminum cap, lay it sideways, leave it upside down, etc. and let it stand naturally,
When the fitting state between the container neck and the aluminum cap was examined, the neck was not deformed, and there was no liquid leakage, which was good.

(Effect of the invention) Since the container body is made of polyethylene terephthalate resin alone, and the middle layer of the neck is made of heat-resistant resin, the heat deformation temperature, which is a weak point of the conventional stretch-blow container, is dramatically improved. In addition, the transparency required for the container is not impaired and the commercial value is excellent. Further, since there is no need for a special process such as neck whitening (crystallization) used as a part of the conventional technique, the production speed is improved, the cost is reduced, and the quality is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a bottomed parison of a container according to the present invention. (1) …… Outer layer (2) …… Intermediate layer (3) …… Inner layer (4) …… Bottomed parison

Claims (3)

[Claims] 1. A container mainly composed of polyethylene terephthalate resin, wherein the container body is made of polyethylene terephthalate resin alone, and the middle part of the container neck is made of a heat-resistant synthetic resin such as polycarbonate resin, aromatic polyester resin or aromatic polyester carbonate. A heat-resistant container comprising a single resin or a mixture of resins, wherein an inner layer and an outer layer made of polyethylene terephthalate resin are laminated on the inner and outer surfaces of the intermediate layer. 2. The heat resistant container according to claim 1, wherein the middle layer of the neck has a thickness of 30 to 90% of the total thickness of the neck. 3. The intermediate layer of the neck has a heat distortion temperature of 120 ° C. (ASTM-
The heat-resistant container according to claim 1, which is made of a resin of D-648) or more.