JPH0479901B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polyethylene terephthalate bottle with a whitened spout.

(Prior Art and Problems to be Solved by the Invention) Recently, biaxially stretched blow-molded polyethylene terephthalate bottles have begun to be used as containers for items that are filled and sterilized at high temperatures, such as alcoholic beverages, sauces, and fruit juices.

This polyethylene terephthalate bottle is made by melt injection molding polyethylene terephthalate resin.
It is obtained by molding a preform by melt extrusion molding, etc., and pressing this preform against the inner surface of a mold by blowing high-pressure gas at a stretching temperature.Oriented crystals are likely to occur in the body part that is subjected to strong stretching. , by heat treatment and crystallization, fine crystals are produced, transparent,
High strength can be obtained. However, since the spout of a blow-molded bottle is not stretched, crystallization does not proceed and the bottle lacks heat resistance, making it unusable as is. Therefore, one way to improve the heat resistance of the spout is to heat the entire spout, which consists of the part that covers the cap and the subsequent bulge that is provided for supporting the bottle. Crystallization and whitening are carried out. However, although whitening does improve heat resistance,
This whitening is due to the large development of spherulites, so as the degree of crystallinity increases, the impact resistance deteriorates, and there is a problem that the spout part will be damaged if it is dropped when it is filled with contents. . In particular, the bulge at the bottom end of the spout, which supports the bottle during filling, is susceptible to strong impacts and is easily damaged.

(Means for Solving the Problems) The present invention has improved heat resistance and impact resistance by whitening the portion of the spout portion that covers the cap to a specific value and not whitening the bulging portion that follows. The object of the present invention is to provide a polyethylene terephthalate bottle having an excellent spout in both of the above.
The following description will be made based on the attached drawings.

Fig. 1 is a partially cutaway front view showing an example of the plastic bottle of the present invention, and Fig. 2 shows the relationship between heat resistance, impact resistance, and crystallinity of the whitened portion of the spout. This is a graph.

In the present invention, an unstretched spout 1 is whitened by crystallization except for a bulging portion 3 at the lower end of the spout, and a whitened portion 2 having an average crystallinity of 28 to 36 volume percent is formed. The present invention also relates to a polyethylene terephthalate bottle characterized in that the unstretched bulge 3 at the lower end of the spout 1 is an unwhitened portion.

If the average crystallinity of the whitened portion 2 is less than 28 volume percent, the heat resistance of the spout 1 will be insufficient and the cap will become loose due to deformation of the spout 1 during high-temperature filling. Furthermore, if the degree of crystallinity exceeds 36%, impact resistance will deteriorate. It is preferable that the crystallinity is 30 to 36 percent by volume because the loosening of the cap is particularly small. The degree of crystallinity of the spout can be adjusted by the temperature and time for heating the spout.

In addition, the unstretched bulge 3 at the lower end of the spout
Since it is a non-whitened part, it has good impact resistance, and since it bulges outward, it is difficult for the heat of the contents to be transmitted and does not soften, so it is extremely difficult to break and provides stable support during filling. It has characteristics.

As a specific heating means, for example, a method of heating the spout part with a far-infrared heater to whiten it can be adopted, and in this case, the bulging part 3 at the lower end of the spout is covered with a shielding plate to prevent it from being heated. As a result, only the mouth plug part becomes white, and the bulge part remains unwhitened.

Hereinafter, it will be explained in more detail with reference to Examples.

(Example) By whitening and crystallizing the unstretched spout part,
As shown in Figure 1, the average crystallinity of the whitened area 2 is
Pour 1 liter of warm water at 95℃ into a polyethylene terephthalate blow bottle (capacity 1 liter, spout length 22.4 mm, screw thread diameter 28 mm) containing 28 to 40 volume percent polyethylene terephthalate.
After filling a small bottle, a 28 mm aluminum cap (polyvinyl chloride gasket) was attached, and the opening torque after heating was measured as an index of heat resistance, and a drop test was performed as an index of impact strength. The results are shown in FIG. Figure 2 shows the opening torque [Kg・cm] in the lower half of the vertical axis, and the drop test results in the upper half of the vertical axis.
The horizontal axis represents the average crystallinity of the whitened portion 2 of the plug portion 1. Here, the evaluation method is as follows.

(1) Drop test After filling, cool it down and drop it 10 times from a height of 1 m onto the concrete floor with the plug part 1 facing down. If there is even a slight crack in the plug part, it will be considered damaged. In this test, if even one item was damaged, it was marked as ×, and if no damage was found, it was marked as ○.

(2) Opening torque After filling, the spout part 1 is heated and sterilized by leaving it on its side for 20 minutes, then cooled down.
Measure the opening torque using Model 2-0T).
The opening torque immediately after filling is 17Kg・cm.

(3) Average crystallinity of the whitened part of the spout part In Fig. 1, three parts of the whitened part 2 of the spout part 1, the upper part 21, the middle part 22, and the lower part 23, are separated from the wall within a 2 mm square area. Cut out to the full thickness,
The density was measured using a density gradient tube, and the three portions were averaged to calculate the degree of crystallinity by proportioning the density when polyethylene terephthalate was completely amorphous to 1.335 and the density when crystallized at 100 volume percent to 1.455.

As is clear from FIG. 2, the bottle of the present invention, in which the average crystallinity of the whitened portion of the unstretched spout is 28 to 36 volume percent, has an opening torque of 6 kg cm or more and after heating. In addition to maintaining sufficient airtightness for practical use, it did not break during drop tests and has good impact strength. In addition, when the average crystallinity is 30% by volume, the opening torque is 9 kg·cm, which shows that the heat resistance is particularly improved.

(Effects of the Invention) As explained above, in the polyethylene terephthalate bottle of the present invention, the average crystallinity of the whitened portion of the spout that has not been stretched is 28 to 36 volume percent, so the heat resistance of the spout is improved. At the same time, it also has sufficient impact resistance, and since the unstretched bulge at the lower end of the spout is made into an unwhitened part, it retains a suitable degree of flexibility, and as before, this bulge can be used as a support part. It has excellent effects such as there is no risk of damage even if excessive force is applied during filling, capping, or gripping and transporting this part.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view showing an example of the plastic bottle of the present invention, and Fig. 2 shows the opening torque [Kg cm] in the lower half of the vertical axis, and the drop test results in the upper half of the vertical axis. This is a graph showing the relationship between the two, with the horizontal axis representing the average crystallinity of the whitened portion of the spout. 1... Mouth plug part, 2... Whitening part, 3... Bulging part.

Claims (1)

[Claims] 1. Whiten the unstretched spout part by crystallization except for the bulging part at the lower end of the spout part to obtain a whitened part with an average crystallinity of 28 to 36 volume percent, and A polyethylene terephthalate bottle characterized in that an unstretched bulge at the lower end of the bottle is an unwhitened portion.