JPS6239443A - Oriented molded bottle body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the structure of a biaxially stretched blow-molded bottle made of polyethylene terephthalate resin, and the present invention relates to the structure of a biaxially stretched blow molded bottle made of polyethylene terephthalate resin. It is designed to improve performance.

[Conventional technology]

Polyethylene terephthalate resin (hereinafter simply referred to as PET) is used in large quantities in many fields as biaxially stretched blow-molded bottles due to its stable physical properties, non-polluting properties, excellent transparency, and high mechanical strength. This makes it extremely useful, especially as a weight gainer for food.

In this way, PET bottles have many excellent properties, but in order to effectively exhibit these excellent properties, PET bottles should be axially stretched and blow molded. It is required that each part of the crystal be oriented.

By axially stretch blow molding a PET bottle, most of it is oriented and crystallized, thereby effectively exhibiting the above-mentioned excellent properties. The tube part and bottom part are either not stretched at all or are formed into the final shape without being stretched or deformed, so it is difficult to fully demonstrate the characteristics of PET compared to other parts. Due to this problem, it was not possible to fully utilize the special strength of the PEIJJ bottle.

[Problem that the invention seeks to solve]

One way to solve this problem is to heat-crystallize the mouth part, which is the non-stretched part, by heat treatment, thereby improving the heat resistance and mechanical strength stability of the mouth part. and has been shown to be sufficiently effective.

However, since the 9-neck tube part is not related to the biaxial stretching forming operation at all, even if this neck tube part is whitened by thermal crystallization, the biaxial stretching process increases.

Although the blow molding operation does not cause the same disadvantages, applying the same idea, that is, a means of improving the stability of heat resistance and mechanical strength by thermal crystallization, to the bottom of the filler However, this has been impossible because the part is formed into a shape different from the shape of the preform by stretch molding.

Therefore, in this type of PET biaxially stretched blow-molded bottle filler, the properties of the bottom part of the filler remain inferior to the properties of the other parts of the filler, which causes the PET bottle filler to However, it was not possible to fully exhibit the excellent characteristics that could be exhibited.

The present invention was devised to solve the problems and drawbacks of the conventional examples described above, and involves whitening the bottom part of the bulking material to be molded by thermal crystallization to cause sufficient stretching deformation in the bottom part. The purpose is to put the bottom part in a state where it can exhibit the same characteristics as the other parts of the body.

[Means for solving problems]

The present invention will be described below with reference to the drawings showing one embodiment of the present invention.

The stretch-molded bottle 1 according to the present invention is a polyethylene terephthalate resin stretch-molded bottle formed by biaxially stretching blow-molding a preform 6 in the shape of a cylinder with a bottom, and is located at the center of the bottom wall 4. The center portion 5, which is the center of stretching in biaxial stretching and becomes a non-stretched portion, has a thickness approximately equal to that of the preform, and is whitened by thermal crystallization.

The above-mentioned center part 5 is a part that hardly undergoes stretching deformation in the biaxial stretch blow molding of the bulkhead 1, but it is slightly deformed by stretching, but in the present invention, it is a part that is not deformed by stretching at all. It is said that
Therefore, the wall thickness of the center portion 5 is almost the same as the wall thickness of the preform 6.

Therefore, the wall thickness of the bottom wall 4 portion near the center portion 5 is formed by stretching and deforming to the extent that this portion is formed, so it is formed thinner than the center portion 5. Become.

In addition, as mentioned above, the center part 5 is a part that is formed into the final shape without being stretched or deformed at all, so the stretching force acting during biaxial stretch blow molding must not cause stretching deformation, and therefore the center It is necessary to provide this central portion 5 with some means to prevent the portion 5 from being stretched and deformed.

[Effect]

Since the stretch-molded bottle 1 according to the present invention has the above-described structure, the heat resistance of the center portion 5, which is the non-stretched portion, is inferior to the heat resistance of the other stretch-molded portion 1. As a result, the heat resistance of the entire bulkhead 1 can be improved.

Furthermore, since the wall thickness of the center portion 5 is almost equal to the wall thickness of the preform 6, the center portion 5 must be held by some means to prevent stretching and deformation. become.

Due to the action of a local holding force that prevents the center portion 5 from being deformed by stretching, the portion of the bottom wall 4 located around the center portion 5 is provided with a holding force to prevent the center portion 5 from being deformed by stretching. As a reaction to the force, the stretching force acts in a concentrated manner, and as a result, the amount of stretching deformation in this area increases compared to the conventional case, promoting oriented crystallization in this area. It turns out.

Furthermore, as described above, since the oriented crystallization of the bottom wall 4 excluding the center portion 5 is promoted, the density of this bottom wall 4 is improved, and therefore, it is necessary to improve the heat resistance of this bottom wall 4. When the temperature of the bottom mold is raised to heat set the bottom wall 4, the bottom wall 4 does not become white due to the heat of the heat. It becomes possible to apply it to the weir body 1.

〔Example〕

In the illustrated embodiment, a weir body 1 according to the present invention is formed into a primary molded product 7 from a preform 6 having a short cylindrical shape approximately in the shape of a dish by a double blow molding method, that is, by the same biaxial stretch blow molding. This secondary molded product 7 is heated and forcibly subjected to heat shrinkage deformation to form a secondary molded product 8, and this secondary molded product 8 is formed into the weir body 1 by stretch blow molding with a small amount of stretching. An example of molding using the following molding method is shown.

The method for forming the weir body 1 shown in this example is as follows:
When molding into the secondary molded product 8, the internal residual stress is completely eliminated by heating, so there is almost no internal residual stress in the weir body 1, which is the molded product. This means that it is possible to obtain a weir body 1 with extremely high properties.

Of course, the method for forming the weir body 1 is not limited to the above-described double blow molding method, but may be achieved by a biaxial stretch blow molding method.

In any case, since biaxial stretch blow molding means is always used to mold one workpiece 1 from the preform 5 into the weir body 1, there is no way to prevent stretching deformation from occurring in the center part 5. , it becomes a means compatible with this biaxial stretch blow molding method.

The simplest means to prevent stretching deformation from occurring in the center portion 5 is to whiten the center portion 5 by heat treatment at the time of forming the preform 6.

In the case of this means, since it is necessary to specify the center part 5 before stretch forming, it is easy to specify the center part 5, and
The preform 6 is required to have a shape that can be accurately specified.

If the center portion 5 is whitened at the time of forming the preform 6 in this way, the stretching deformation force acting on the bottom wall 4 during stretch forming will be applied to the portions of the bottom wall 4 adjacent to the center portion 5 that cannot be stretched and deformed.
In other words, the conventional amount acts concentratedly on the portion that was considered to be prone to stretching deformation, and therefore gives a stretching deformation amount close to the stretching amount to the body tube 3 to the bottom wall 4 portion close to the center portion 5. You will be able to do that.

In addition, when molding the weir body 1 by the double blow molding method shown in FIG.
When performing biaxial stretch blow molding.

The preform 6 is stretched and deformed in the axial direction while the stretched center part of the preform 6, that is, the center part 5 is held between a stretching rod (not shown) and a bottom mold, and the mold temperature of the bottom mold is adjusted to the PET material. By setting the temperature to be higher than the thermal crystallization temperature, whitening of the center portion 5 can be achieved during the biaxial stretch blow molding operation from the preform 6 to the primary molded product 7.

That is, the center portion 5 is heated to a temperature higher than the whitening temperature of PET during biaxial stretch blow molding of the preform 6 into the primary molded product 7, and the center portion 5 is not deformed by stretching at all. , other parts are stretched and deformed 2 As a result, the density is increased due to oriented crystallization, so
Thermal crystallization occurs only in the central region 5 where no improvement in density has been achieved.

In the case of this second means, the identification of the center part 5 is accurate and reliable, and no special heat treatment is required, so there is no need for an independent heat treatment for the center part 5, and furthermore, the shape of the preform 6 is On the other hand, there is a problem in the molding operation that the center part 5 must be held between the stretching load and the bottom mold.

The effect of this second means on the bottom wall 4 is almost the same as that of the first means described above, but as shown in FIG. Since the wall is thick and protrudes downward, when blow molding the secondary molded product 8 onto the weir body 1 in the double blow molding method, the central part of the secondary molded product 8 formed by free shrinkage deformation. 5 can be accurately positioned using this protruding center portion 5, which is extremely effective in achieving good double blow molding of the weir body 1.

Note that the mouth tube 2 of the extension 1 is preferably whitened by heat treatment at the time of forming the preform 6, so that it will not be improperly deformed by the heat treatment during stretch-forming of the preform 6 into the extension 1. can be prevented.

〔Effect of the invention〕

As is clear from the above description, in the thickening according to the present invention, the center part located at the center of the bottom wall, which is the center of stretching, is whitened by heat treatment, so it is possible to eliminate the inconvenience caused by non-stretching of the center part. In addition, since this central portion is held so as not to be deformed by stretching, the bottom wall portion around the central portion is semi-forced to be deformed by stretching, thereby making it possible to significantly increase the amount of stretching deformation of the bottom wall. Done.

It can improve the heat resistance, mechanical strength, and transparency of the bottom wall, and it can be molded using conventional blow molding operation methods and blow molding equipment, so it is easy to mold. It exhibits excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the enlargement according to the present invention. FIG. 2 is a longitudinal cross-sectional view for explaining the molding operation when the bulking material shown in FIG. 1 is molded by the double blow molding method. Explanation of symbols: 1; Addition; 2; Round part; 3; Trunk; 4; Bottom wall; 5; Center; 6; Preform; 7; - Next molded product. 8; Secondary molded product.

Claims (1)

[Claims] This is a polyethylene terephthalate resin stretch-molded bottle that is formed by biaxial stretch blow molding a preform in the shape of a cylinder with a bottom. A stretch-molded bottle formed by whitening a center portion, which is a stretched portion and has a wall thickness approximately equal to that of the preform, by thermal crystallization.