JPH0958646A - Heat-resistant and pressure-resistant self-supporting container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the self-supporting stability of a container from being deteriorated due to projection of a bottom thereof at the time of sterilization of the container under heating and further make chemical resistance excellent by mainly crystallizing a low orientation region at a central part of the bottom, a low orientation region at a peripheral part of the central part of the bottom, low and high orientation regions at each valley line, etc. SOLUTION: (A) which is a portion of a container bottom 2 denotes a central part of the bottom, (B) denotes a peripheral part 4 of the central part of the bottom, (C) denotes each valley line 6, (D) denotes each portion 7 from the edge of the peripheral part of the central part of the bottom to a grounding part, and (E) denotes each valley 9, which is a region surrounded by a grounding part of each leg, an outside part of the leg and the valley line, respectively. Crystallization of each portion of the (A)-(E) may be performed for at least one or more portions. At least one portion selected from among the (A)-(E) is crystallized, or preferably, crystallization is may be performed for the (A), (B) and (C) in combination. By crystallization of the container bottom 2a, creep deformation can be particularly prevented at the time of sterilization under heating, and chemical resistance of a material can be improved by crystallization of the portions 4, 6 which easily craze.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-standing container made of a biaxially stretched blow-molded saturated polyester resin, which is suitable for filling carbonated drinks, soft drinks and the like. The present invention relates to a self-supporting container having excellent heat resistance and pressure resistance during heat sterilization.

[0002]

2. Description of the Related Art Conventionally, as a heat-resistant and pressure-resistant container, in order to improve the internal pressure resistance of the container body, the bottom portion is bulged to form a hemispherical shell, and a base cup molded into a bottomed cylinder is attached to this. Then, the mainstream is a container with a self-supporting function. However, the use of the base cup requires that the base cup be separately formed and fixed, the weight of the container increases, the size of the container increases, and the hot water is sufficiently supplied to the bottom of the container in the heat sterilization process. Therefore, there are various problems such as that the contents cannot be heat-sterilized smoothly, and that water is accumulated in the base cup and it is difficult to quickly drain the contents.

[0003] Further, from the viewpoint of resource saving and environmental issues, it is desired to effectively reuse used empty containers.
For containers equipped with a base cup, the container body and the base are usually
Since the material of the scoop and the adhesive is different from the material of the container body, they must be separated when they are reused, and there is also a problem that the process cost becomes high.

Due to these problems, a heat-resistant and pressure-resistant container that does not require a base cup has been desired. Several proposals have been made for pressure-resistant containers that do not require a base cup, and generally, a plurality of legs are radially bulged around the center of the bottom, and valleys are formed between these legs. It has either a structure in which a line portion is formed or a champagne type structure, and is disclosed in, for example, Japanese Patent Publication No. 48-5708.
Japanese Patent Publication No. 59-40693, Japanese Patent Publication No. 6-9170
JP-A-63-202424 and JP-A-3-43342.

[0005]

However, although the containers described in these items can obtain satisfactory performance as pressure resistant containers, they are used as heat resistant and pressure resistant containers in which a heat sterilization process is carried out. In that case, sufficient performance cannot be obtained. That is, in the containers described in the above items, since the unstretched region or the low stretched region exists in the center of the bottom and the periphery of the center, the temperature of the contents during heat sterilization is about 50 ° C to 70 ° C. When rising,
Since the internal pressure increases and the container material itself tends to undergo creep deformation, the low-stretched region in the center of the bottom and the periphery of the center and the low-stretched region of the valley line and the high-stretched region in the periphery thereof are formed. Creep deformation causes protrusion and the container loses self-supporting stability.

As a method for solving this problem, for example,
It is conceivable to use the container described in JP-A-5-85535. Since this container is a container in which the center of the bottom is crystallized and the periphery of the center is sufficiently stretched, creep deformation of the bottom when the internal pressure increases during heat sterilization can be suppressed to some extent. However, even in the case of this container, it is difficult to sufficiently stretch the valley line portion formed between the leg portions and a low stretched region remains in the portion, so that the portion is not cleared during heat sterilization. -There is a problem in that the bottom portion is projected to lose the self-sustaining stability due to the deformation of the base, or the self-sustaining stability is maintained, but the flavor line is greatly lowered to lose the practicality.

As a result of earnest research by the researchers of the present invention, a bottom structure in which a plurality of legs are radially bulged around the center of the bottom and a valley line portion is formed between the legs. in the case of,
It was found that the stress due to the internal pressure was concentrated especially on the peripheral part of the bottom center part and the valley line part, and furthermore, in the bottom protrusion during the actual heat sterilization, the creep deformation of the valley line part and its periphery was particularly large. discovered.

The present invention has solved the above problems, and is mainly liable to cause creep deformation due to an increase in internal pressure during heat sterilization, mainly in a low-stretched region in the center of the bottom and in the peripheral region of the center of the bottom. By crystallizing the low-stretched part region, and the low-stretched part region and the high-stretched part region of the valley line part, the bottom part does not lose its self-sustaining stability when the container is heat-sterilized, and further chemical resistance It is intended to provide a heat-resistant and pressure-resistant self-supporting container having excellent properties.

[0009]

Means for Solving the Problems That is, the present invention is a biaxially stretch blow-molded saturated polyester resin hollow container comprising a mouth / neck portion, a shoulder portion, a body portion and a bottom portion. It has a self-sustainable structure in which a plurality of leg portions are radially bulged around and a valley line portion is formed between these leg portions and are selected from the following (A) to (E). A heat-resistant and pressure-resistant freestanding container in which at least one part is crystallized. (A) Bottom center part (B) Bottom center part peripheral part (C) Valley line part (D) Bottom part peripheral part edge to ground contact part (E) Valley part

Hereinafter, the present invention will be described in detail. The saturated polyester resin used in the hollow container of the present invention is preferably a thermoplastic polyester resin whose main repeating unit is ethylene terephthalate, and the thermoplastic polyester resin is preferably one containing a homopolymer of polyethylene terephthalate as a main component.

As this thermoplastic polyester resin,
Some of the terephthalic acid components are aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid; hexahydroterephthalic acid, hexahydroisophthalic acid Alicyclic dicarboxylic acids such as; adipic acid, sebacic acid, azelaic acid and other aliphatic dicarboxylic acids; P-
A copolymer obtained by substituting at least one other difunctional carboxylic acid such as oxyacid such as β-hydroxyethoxybenzoic acid and ε-oxycaproic acid can be used.

In the thermoplastic polyester resin, a part of the ethylene glycol component is, for example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, diethylene glycol, 1,1-cyclohexanedimethylol. , 1,4-cyclohexanedimethylol, 2,2 (4'-β-hydroxyethoxyphenyl)
It may be a copolymer obtained by substituting one or more polyfunctional compounds of other glycols such as sulfonic acid and functional derivatives thereof for copolymerization.

The intrinsic viscosity of the thermoplastic polyester resin used in the container of the present invention is preferably 0.7 to 1.0, particularly preferably 0.75 to 0.90.

Further, for the thermoplastic polyester resin used in the present invention, additives such as a colorant, a heat deterioration preventing agent, an antioxidant, an ultraviolet absorber, an antistatic agent, an antibacterial agent and a lubricant may be appropriately used. it can.

In the present invention, as a method of crystallizing a specific portion of the bottom of the container, (A) a method of crystallizing by heating in a mold during blow molding, and (B) an infrared heater using a blow molded container as a heat source. Using infrared lamps, hot air, quartz tube heaters, high-frequency heating devices, etc., install a shield plate having a slit between the heat source and the bottom of the container, and through the slit provided in this shield plate, the desired part of the bottom of the container There is a method of heating and heat crystallization. The surface shape of the shielding plate preferably has a surface shape substantially similar to the bottom surface of the container. The heat of the heat source reaches the bottom of the container through this slit, and the desired portion can be crystallized by the heat. In addition, by passing cooling water or warm water through the shielding plate, the surface temperature of the shielding plate is maintained at a temperature not higher than the glass transition temperature of the container material, the temperature rise of the non-heated part of the container bottom is suppressed, and it is heated to a high temperature. Can be prevented. Further, it is possible to use two or more kinds of shield plates as necessary and perform crystallization in several stages.

In the present invention, the parts (A) to (E) are the bottom part of the container. The (A) center portion of the bottom portion is, for example, a portion indicated by 3 in FIG. 12 and is an unstretched or low stretched portion region. (B) The peripheral portion of the central portion of the bottom portion is a portion indicated by 4 in FIG. 12, which is a low stretched portion region. (C) The valley line portion is a strip-shaped portion formed between the leg portions, and is, for example, a portion indicated by 6 in FIG. 12, and a portion near the central portion peripheral portion of the bottom portion is a low extension portion, The degree of stretch orientation becomes higher as it gradually approaches the body side, and it is a high stretch region. (D) The portion extending from the peripheral edge of the center of the bottom portion to the ground contact portion is, for example, the portion indicated by 7 in FIG. 12, and the peripheral portion side of the center of the bottom portion is the low extension portion area, but the ground contact portion. As it approaches, the stretched region becomes high. (E)
The valley portion is a region sandwiched between the ground contact portion of the leg portion, the outer side surface portion of the leg portion, and the valley line portion, and is, for example, a portion indicated by 9 in FIG. 12, and is a low stretch portion region and a high stretch portion. Area exists. In the present invention, each part (A) to (E) may be crystallized if at least a part of each part is crystallized.

The container of the present invention comprises a container bottom (A)-
At least one portion selected from (E) is crystallized, preferably a combination containing (A), (B) and (C), and a particularly preferable constitution is
It is a combination of the following (a) to (e). (B) Combination of (A), (B) and (C) (b) Combination of (A), (B), (C) and (D) (C) (A), (B), (C) , (D) and (E) in combination (d) (A), (B), (C) and (E) in combination By crystallizing the bottom of the container, it is possible to suppress creep deformation particularly during heat sterilization. .

The crystallized portion of the bottom of the container of the present invention is
In the case of polyethylene terephthalate, the density is 1.350g
/ cm ³ ~ 1.385g / cm ^{3 is in} the range, particularly preferred density,
It is 1.350 g / cm ^{3 to} 1.380 g / cm ³ . If the density of the crystallized part is less than 1.350 g / cm ³ , the bottom part of the container may creep and deform due to internal pressure during heat sterilization of the container, and the product may lose its self-standing stability and lose its commercial value. . Also, 1.385g
If it exceeds / cm ³ , the impact strength of the crystallized part will decrease and the bottom part may break when the container is given a drop impact.

Further, in the present invention, the periphery of the central portion of the crystallized container bottom portion and the valley line portion are one of the portions where craze is likely to occur. Claze is further promoted by a lubricant or the like in the conveyor line of the filling factory, causing stress cracks, but by crystallizing this part, it is possible to improve the chemical resistance of the material,
Generation of stress cracks can be suppressed.

The container of the present invention is a self-supporting container suitable for filling carbonated beverages, soft drinks, etc., but the container of the present invention further has at least a container mouth neck portion in order to further enhance its performance. One part selected from the support ring and the lower part of the support ring may be crystallized or stress-relaxed.

[0021]

The present invention will be described in detail below with reference to examples.

Example 1 Polyethylene terephthalate (IV = 0.85) was injection molded to obtain a preform. After reheating this bottomed preform, biaxial stretch blow molding was performed to obtain a self-supporting container. This self-supporting container is, as shown in FIGS.
The individual leg portions 5 bulged around the bottom central portion 3 radially at equal intervals, and the valley line portions 6 were formed between the leg portions 5 to have a self-supporting bottom structure.

Next, the self-supporting container is shown in FIG.
The hatched portion indicates the opening 11a) and the shielding plate 10a as shown in FIG.
When the bottom part of the self-supporting container was heated from below the shielding plate 10a by an infrared heater, the bottom center part 3, the bottom center part 4, and the valley line part 6 were crystallized. A container having a container bottom 2a was obtained (shown in FIG. 5).
The total height of this container was 310 mm and the volume was 1.5 liters. The front view of the obtained self-supporting container is shown in FIG.

Example 2 In the same manner as in Example 1, a shield plate 10b as shown in FIG. 6 was used to heat the bottom of the self-supporting container, and the bottom center part 3, the bottom center part peripheral part 4, the valley line part were used. 6, and a container bottom 2 in which a portion 7 from the peripheral edge of the center of the bottom to the grounding portion is crystallized
b was obtained (shown in FIG. 7).

Example 3 In the same manner as in Example 1, a shield plate 10c as shown in FIG. 8 was used to heat the bottom of the self-supporting container, and the center 3 of the bottom, the peripheral 4 of the center of the bottom, and the valley line portion were used. 6, a container 7 having a container bottom 2c (shown in FIG. 9) in which a part 7 extending from the peripheral edge of the center of the bottom to the ground contact part and a part 9 of the valley was crystallized was obtained.

Embodiment 4 Similar to Embodiment 1, a shielding plate 10d as shown in FIG. 10 is used.
By heating the bottom of the container to crystallize the bottom center part 3, the bottom center peripheral part 4, the valley line part 6, and part of the valley part 2d (shown in FIG. 11). A self-supporting container having

Comparative Example 1 In Example 1, the bottom of the container was not heated and crystallized. The obtained hollow container had no bottom crystallized at all.

(Evaluation Method and Results) Twelve containers obtained in each of the examples and comparative examples were prepared, and 2.5 m of gas volume carbonated water was added at 5 ° C.
After filling up to m and capping, a hot water shower at 70 ° C. was applied for 30 minutes, and then showering was performed with water at 20 ° C. for 10 minutes to cool and evaluate. 1) Evaluation of self-sustaining stability When the center part of the bottom part did not project below the ground contact surface of the leg part, it was evaluated as ◯, and when it protruded it was evaluated as x. 2) Evaluation of amount of drop in taste line Before and after the evaluation, the difference in height from the tip of the mouth and neck of the hollow container to the liquid surface of the content was measured. A descending amount of 20 mm or less is regarded as good. 3) Total deformation amount The height of the hollow container before and after the evaluation was measured to obtain the difference.

[0029]

[Table 1]

From the test results of Examples 1 to 4 and Comparative Example 1 described above, the self-standing container of the present invention controls the bottom protrusion due to the creep deformation during heat sterilization to prevent the drop of the flavor line and the self-standing stability. It is understood that it is excellent to hold.
The structure of the container bottom in the present invention is not limited to the structure of the embodiment of the present invention, and similar effects can be obtained in other structures similar to those of the embodiment of the present invention.

[0031]

As described above, the self-supporting container of the present invention is a heat-resistant and pressure-resistant self-supporting container which suppresses the bottom projection during heat sterilization of the container contents to maintain self-sustaining stability and has excellent chemical resistance. is there. Further, since the container according to the present invention does not require a base cup, hot water at the time of heat sterilization reaches the bottom of the container sufficiently, and heat sterilization of the contents can be smoothly performed. Reuse becomes easy.

[Brief description of drawings]

FIG. 1 is a front view of a self-standing container of the present invention.

FIG. 2 is a bottom view before crystallization of the bottom of the self-supporting container of the present invention.

FIG. 3 is a sectional view of the bottom of the self-standing container of the present invention.

FIG. 4 is a plan view of a shielding plate used in Example 1.

5 is a bottom view of the self-supporting container of Example 1. FIG.

FIG. 6 is a plan view of a shielding plate used in Example 2.

FIG. 7 is a bottom view of the self-supporting container according to the second embodiment.

FIG. 8 is a plan view of a shielding plate used in Example 3.

FIG. 9 is a bottom view of the self-supporting container of Example 3.

FIG. 10 is a plan view of a shielding plate used in Example 4.

FIG. 11 is a bottom view of the self-supporting container of Example 4.

FIG. 12 is a view showing each part of the container bottom of the present invention.

[Explanation of symbols]

1 Self-supporting container 2 Bottom parts 2a, 2b, 2c, 2d, partially crystallized container bottom part 3 (A) Bottom center part 4 (B) Bottom center part peripheral part 5 Legs 5A Ground part 6 (C) Valley Line portion 7 (D) Bottom portion from the peripheral edge of the central portion to the grounding portion 8 Outside surface portion of the leg portion 9 (E) Valley portion 10a, 10b, 10c, 10d Shielding plate 11a, 11b, 11c, 11d Slit 11 Shoulder 12 Body 13 Mouth and neck

Claims (1)

[Claims] 1. A biaxially stretch blow-molded hollow container made of saturated polyester resin comprising a mouth, a neck, a shoulder, a body and a bottom, wherein the bottom has a plurality of legs radially around a center of the bottom. It has a structure in which it bulges out and forms a valley line portion between these leg portions so that it can stand on its own.
At least one portion selected from (E) is crystallized, which is a heat-resistant and pressure-resistant freestanding container. (A) Bottom center part (B) Bottom center part peripheral part (C) Valley line part (D) Bottom part peripheral part edge to ground contact part (E) Valley part