JPS5911083Y2 - Pressure-resistant plastic containers for carbonated beverages - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a biaxially stretched blow container made of polyethylene terephthalate that has excellent pressure resistance and excellent content retention capacity.

Biaxially stretched blown polyethylene terephthalate containers, as described in US Pat. No. 3,733,309, have not only high pressure resistance, rigidity, and transparency, but also low permeability to gases such as oxygen and carbon dioxide. Due to its excellent product retention ability, it is currently widely used as plastic bottles for carbonated drinks in the United States and some European countries, and as bottles for soybean oil in Japan.

In the case of carbonated beverage bottles, it is required that the container be able to withstand a high pressure of about 11 kg/Cl+'' (gauge pressure), assuming the worst conditions that the container will be subjected to in distribution and consumption mechanisms.

When a plastic bottle is subjected to internal pressure, the weakest part of the bottle is generally around the bottom of the bottle.

For these reasons, two technologies have been developed and put into practical use.

For example, a composite package consisting of a petal-shaped bottom structure described in Japanese Patent Publication No. 48-5708 and a bottle and a support cup (Hakama parts) described in Japanese Patent Application Laid-open No. 51-70086 is one such example.

In addition, various new technologies have been invented from the viewpoint of pressure resistance.

On the other hand, one of the important performances required of plastic bottles for carbonated beverages is to minimize carbonation loss.

The most popular carbonated drink, cola, has a rating of 3.5
It is known that it contains 4 to 4 volumes of carbon dioxide gas.

Plastics permeate or adsorb gases such as oxygen and carbon dioxide to varying degrees.

Therefore, the carbon dioxide gas in the carbonated beverage content is lost over time, and if the absolute amount lost is large, the carbonated beverage loses its marketability significantly.

The amount of carbon dioxide gas lost through the container wall is directly proportional to the surface area of the container (or the contact area between the contents and the container) when comparing the same container material, ambient temperature, and internal pressure.

In addition, the amount of carbon dioxide lost by absorption into the container wall is determined by the weight of the container (
Alternatively, in the case of containers having the same internal volume, the container weight is directly proportional to the surface area of the container, since there is generally a direct correlation with the surface area of the container.

For the above reasons, it is clear that the design of pressure-resistant plastic containers must be determined by evaluating the shape of the container from the perspective of carbonation loss in carbonated beverages.

Furthermore, consideration was given to reducing the surface area of the container by minimizing the amount of oxygen gas in the atmosphere that penetrates the container wall and dissolves into the contents, and by suppressing the migration of acetaldehyde, which is present in the polyethylene terephthalate material, into the contents. This also results in suppressing the deterioration of the flavor of carbonated beverages.

According to the present invention, a hollow container body is formed by biaxial stretch blow molding of polyethylene terephthalate, and the upper and bottom portions of the container have a hemispherical or semi-spheroidal shape, and a container body that surrounds the bottom of the container body. The height of the container body excluding the neck is A.
, when the maximum horizontal diameter of the body is B, it has a dimension that satisfies the following formula 1.0≦A/B≦3.0, and a straight portion that may exist between the top of the container and the bottom of the container. Provided is a pressure-resistant plastic container for carbonated beverages characterized in that the ratio of HR/A is 0.4 or less, where the length is HR and the height of the container excluding the neck portion is A.

A container shape that is considered advantageous from the standpoint of pressure resistance alone is an infinitely long double cylinder.

The reason for this is that when the internal pressure is P, the circumferential principal stress σ generated in the double cylindrical wall of radius γ and thickness μ is expressed by the following equation.

σ=−·P (1) In other words, when considering a constant internal volume, it can be considered as a double cylinder with infinitely small γ and infinitely long length.

However, it can be said that such a container has no practical use.

Therefore, in actual pressure containers, convenience in the distribution and consumption mechanism and ability to hold contents (the physical condition that minimizes the surface area in a double cylinder with a constant internal volume is h/γ = 2 (h is height, γ is 2) (radius of a heavy cylinder) is taken into consideration; a neck of constant diameter, a body substantially straight in the axial direction of the height of the container, an eyebrow connecting the body and the neck with a straight line or a curve, and the above-mentioned Containers have been used that have a bottom with a convex shape as described in Japanese Patent Application Laid-Open No. 51-70086, or a petal-shaped bottom as described in Japanese Patent Publication No. 48-5708.

However, the present inventor has developed a ball, which is considered to be essentially the most advantageous as a pressure-resistant shape, to improve content retention and marketability for two-wheeled stretch-blown polyethylene terephthalate containers for packaging contents such as carbonated drinks. As a result of comprehensively examining other functional aspects including shapeability and other aspects, it was found that this container is superior as a pressure-resistant container compared to current containers that were developed as an extension of the double cylinder theory.

If the container is made into a sphere, there is an inconvenience that the diameter of the body will increase in the case of a large-capacity container, but the following formula 1<A/B≦3.0・
If we use a spheroid that satisfies (2), this inconvenience can be overcome.

Furthermore, since the shape of the container is spherical or spheroidal, the stretching is relatively uniform and the bottom portion is also relatively easy to stretch. When the standard deviation (Q-,.) of the thickness in the circumferential direction is 50 or less, and the minimum thickness of each part of the container excluding the neck is μmax, and the maximum thickness is μmax, μmax/μmi
A container with a narrow thickness distribution is provided, with n ranging from 1.0 to 8.0.

Reducing the thickness distribution of a polyethylene terephthalate biaxially stretched blow container is extremely important for improving the physical properties of the container, and the container based on the present invention has an extremely small thickness distribution, resulting in a small density distribution in each part of the container. For example, the heat treatment technique described in Japanese Patent Application No. 52-107694 can be easily applied.

Furthermore, it is relatively easy to stretch over the entire area of the container, and the thickness distribution, that is, the density distribution, becomes smaller.
Container shrinkage over time as described in No. 7659 is suppressed.

Another problem that arises when making containers spherical or spheroidal is that labels cannot be attached. As long as the ratio (HR/A) of the container height (HR) to the container height (A) excluding the container neck portion is 0.4 or less, the purpose of the present invention is not impaired.

Since the container of the present invention is not self-supporting, for example,
The bottom needs to be surrounded by the base cup (Hakama part) described in the 0086 publication.

Since these Hakama parts do not come into direct contact with the contents, they only need to have a certain level of strength.

From an economic point of view, it is possible to use scraps generated during the manufacture of containers of the present invention or scraps from other containers.

The connection between the base cup and the container is described in Japanese Patent Application Laid-Open No. 51-7008.
It may be physically fitted using a recessed knot as described in Publication No. 6, or it may be joined using an adhesive. Furthermore, if the container and base cup can be thermally bonded, high frequency Techniques such as gluing may also be applied.

The container of the present invention is generally formed from polyester mainly containing ethylene terephthalate units, and has a sealing neck at one end and a closed parison at the other end using the known forming technique of stretch-blowing. Provided by.

Polyethylene terephthalate is preferably used as the raw material polyester, but isophthalic acid/p-β-oxyethoxybenzoic acid may be copolymerized within a range that does not impair the characteristics of the polyethylene terephthalate container and the gist of the present invention.・Dicarboxylic acids such as naphthalene 2,6-dicanolebonic acid, diphenoxyethane-4,4'-dicanolebonic acid, 5-sodium snorehoisophthalic acid, adipic acid, sebacic acid or their alkyl ester derivatives, propylene glycol Copolyesters containing glycol components such as 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, cyclohexanedimethanol, and an ethylene oxide adduct of bisphenol A may also be used.

Furthermore, this polyester can also contain additives such as coloring agents such as pigments and dyes, ultraviolet absorbers, and antistatic agents.

The polyethylene terephthalate used has an intrinsic viscosity [η] of 0.5 or more, particularly 0.6 or more, from the viewpoint of mechanical strength of the stretch blow container.

Hereinafter, the effects of the present invention will be explained using examples.

Example 1 Phenol/tetrachloroethane weight ratio is 50/50
The intrinsic viscosity (IV) at 30°C in a mixed solvent of
．． 75 polyethylene terephthalate pellets were dried to a moisture content of 0.01% using a nitrogen gas circulating hot air dryer.
It was sufficiently dried until it became below.

Using a biaxial stretching blow shaping device (ASB 150) manufactured by Nissei Jushi Kogyo Co., Ltd., the pellets were formed into a spheroid with major axis radius a and minor axis radius b (a/b = A/B) as shown in Figure 1. )
produced 10 types of bottles having the dimensions shown in Table 1, a double cylindrical bottle shown in FIG. 2 having the dimensions shown in Table 1, and a regular bottle having the shape and dimensions shown in FIG.

The weight of all bottles is approximately 46g, and the internal volume of the bottle to the bottom of the bottle is approximately 940g, except for the bottle in Figure 3.
I did a round shape to make it cc.

Results of measuring the internal volume of these 12 types of bottles, the external surface area of the bottle, the instantaneous deformation rate of the internal volume of the bottle when an internal pressure of 4 kg/- was applied, and the carbonation loss using the method described in the footnotes in Table 1. are shown in Table 1.

The deformation of a bottle due to internal pressure is greatly influenced by the bottle wall thickness and bottle shape.

In the case of bottles of the same weight, since a bottle with a smaller surface area has a larger wall thickness, the stress generated is smaller and the amount of deformation is smaller, as is clear from the equation described above in this specification.

Further, in the case of the same internal volume, the larger the diameter of the body and the diameter of the bottom of the bottle, the greater the stress generated and the greater the amount of deformation.

The instantaneous deformation rate due to the internal pressure of the internal volume in Table 1 is affected by the interaction of the two factors mentioned above, but the spheroidal bottle of the present invention satisfies the following formula 1≦A/B≦3. In this case, it can be seen that the pressure resistance is excellent compared to a double cylindrical bottle with the smallest surface area and a bottle having substantially the same shape as a commercially available carbonated beverage bottle.

The loss of carbon dioxide (carbonation loss) in a carbonated drink filled in a bottle can be evaluated by measuring the pressure in the head space of a bottle filled with carbonated drink.

This pressure loss is due to permeation of carbon dioxide gas through the bottle wall, sorption to the bottle wall, and increase in bottle internal volume due to internal pressure.

Regarding the sorption of carbon dioxide gas into the polyethylene terephthalate material that is the bottle wall, since all the bottles in Table 1 have the same basis weight, the equilibrium sorption amount of carbon dioxide gas in each bottle is considered to be the same.

From the standpoint of reducing internal pressure due to increased internal volume, it is clear that the spheroidal bottle is superior as described above.

Considering carbonation loss due to permeation of carbon dioxide gas, the amount of permeation of gas after a certain period of time is directly proportional to the permeation area, that is, the surface area of the bottle.

Therefore, in order to reduce the carbonation loss of carbonated beverage bottles, the surface area must be made as small as possible.

From this point of view, as shown in Table F, it can be seen that the spheroidal bottle has a small carbonation loss and is superior.

? 1; 1st. 2. The internal volume of the bottle was calculated from the weight of the water filled up to filling line 6 in Figure 3 with tap water at 4°C.

*2; The neck area is the actual measured value of the outer surface area of the bottle excluding the neck area above the straight line area directly below the neck ring in Figures 1 to 3.

*3; Bottle height is the value obtained by subtracting the length of the neck from the total height of the bottle.

*4; 4kg/an when the bottle is at room temperature of 20'C
The value is expressed as a percentage by dividing the instantaneous increase in bottle volume by applying internal pressure with nitrogen by the internal volume before pressurization.

*5; Repack (refill) a commercially available glass bottle of Coca-Cola after sufficiently cooling it, and store it in a constant temperature room at 24°C for 3 months, then reduce the pressure in the head space inside the bottle to Pkg/cn1.
, P is the pressure when Coca-Cola reaches 24°C after filling.

When kg/c [Il2, the carponation loss is (P
It is expressed as o-P/Po)xlOO.

*6; The charcoal drinking bottles sold in the United States had the same size and shape.

*The total data is shown as the arithmetic mean value of the measurement results of IO bottles.

Example 2 The wall thickness distribution in the circumferential direction of the bottle of the two types of bottles used in Example 1, excluding the neck, was measured at equal intervals in the axial direction from the cut line just below the neck to the center of the bottom of the bottle. Measurements were taken at five equally divided positions and the standard deviation was determined.

Furthermore, the maximum thickness of each part of the bottle excluding the neck (μ
max) and the minimum value (μ?n) were measured to determine μmax/μ?n.

Separately, immediately after bottle shaping, these 12 types of bottles were stored in an atmosphere at a temperature of 3TC and a relative humidity of 60%, and changes in the filled volume over time were measured using a 4°C water displacement method.

These results are summarized in Table 2.

As is clear from Table 2, for spheroidal bottles with a value of bottle height/bottle maximum body diameter of 3.0 or less, the standard deviation of the thickness in the bottle circumferential direction is 50 or less, and μmax/μ/n is As a result of the thickness distribution being more uniform at 8.0 or less, the shrinkage rate over time, which is considered to be one of the drawbacks of biaxially stretched blown polyethylene terephthalate bottles, is suppressed to a low level.

*1; Numbers 1 to 5 indicate the positions in the axial direction of the bottle height, divided into 5 equal intervals from just below the neck to the center of the bottom of the bottle, and at each position, there are 8 points equally spaced in the circumferential direction of the bottle. was measured and the standard deviation was determined.

The standard difference in thickness at each position 1 to 5 for 10 bottles is determined and expressed as an arithmetic mean value.

*2; Represented by the formula (Vo-V/Vo)X100.

■o indicates the full volume of the bottle immediately after a certain shape, ■ is 3T
C shows the full volume of the bottle after two weeks of storage in an atmosphere of 60% relative humidity.

Example 3 Using the same materials and forming equipment as in Example 1, a spheroidal bottle having a straight section in the body of FIG. 4 and dimensions as shown in Table 3 was formed.

The measured external surface area of these bottles and the 4 kg/(
Table 3 also shows the instantaneous deformation rate of the internal volume at the cutting line when an internal pressure of m'' is applied.

As is clear from Table 3, the ratio of the straight part of the bottle body to the bottle height (HR/ (HR + 2a) is 0.
．． 4 or less and the ratio of the bottle height to the maximum bottle body diameter (': 2 a + HR)/2 b ) is found to be excellent as a pressure-resistant container.

$1.2,3: Shown in Figure 3.

*4: Ratio of the straight part of the body to the height of the bottle excluding the neck.

*5; Bottle height excluding neck/maximum bottle diameter.

*6; Same as footnote (1) in Table 1 *7; Same as footnote (2) in Table 1 *8; Same as footnote (4) in Table 1.

In the containers shown in FIGS. 1 and 4 of the accompanying drawings, the major axis radius a of the ellipse in the upper and lower portions of the spheroidal container wall is the same, but the inequality (2)
Within the range that satisfies However, it should be understood that the purpose of the present invention can be achieved in the same manner.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a spheroidal bottle according to the present invention in the bottle height axis direction, Fig. 2 is a similar sectional view of a double cylindrical bottle, and Fig. 3 is a 3202 bottle for carbonated beverages commercially available in the United States.
FIG. 4 shows a similar cross-sectional view of a spheroidal bottle having a straight section in the body according to the present invention. 1...Spheroidal bottle, 2...Hakama parts (base cup), 3...Neck part, 4
...Neck screw, 5...Neck ring, 6...Setting line, 7...Double cylindrical bottle, 8...Body A spheroidal bottle with a straight section.

Claims (1)

[Claims for Utility Model Registration] A hollow container body formed by biaxially stretched blow molding of polyethylene terephthalate and having a hemispherical or semi-spheroidal top and bottom, and a container body surrounding the bottom of the container body. Remove from the hakama parts fixed to the container body so that
The container body has dimensions that satisfy the following formula 1.0≦A/B≦3.0, where A is the height excluding the neck portion, and B is the maximum diameter of the body in the horizontal direction. A carbonated beverage characterized in that the ratio of HR/A is 0.4 or less, where HR is the length of the straight part that may exist between the bottom of the container and A is the height of the container excluding the neck part. Pressure-resistant plastic container.