JPH07132927A - Heat-resistant self-standing container and manufacture therefor - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a self-supporting container having good heat resistance and pressure resistance at the bottom. A heat-resistant, self-supporting container having a bottom portion in which a plurality of leg portions 11 forming a grounding portion are formed in a circumferential direction, and each leg portion 11 and a valley portion 12 formed therebetween have substantially the same thickness. Is (a)
A plastic parison consisting of a mouth, a body and a bottom is created, and (b) the bison stretch blow molding of the parison is performed so that the valley and the leg are respectively located at the positions corresponding to the leg 11 and the valley 12 of the container. Forming a primary blow molded body having a part,
(c) The primary blow-molded product is shrunk at 80 to 150 ° C, and (d) the shrink-molded product obtained in (c) is placed in a blow mold having a cavity having a shape corresponding to the container. Position so that the legs 11 and valleys 12 of the shrink-formed body correspond to the valleys and legs of the cavity, respectively, and (e) biaxially stretch blow-mold the shrink-formed body to invert the legs and valleys. By manufacturing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-supporting container having good heat resistance and pressure resistance and a method for manufacturing the same, and more particularly to a self-supporting container having good heat resistance and pressure resistance at the bottom and a method for manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION Biaxially stretched blow-molded bottles made of saturated polyester resin represented by polyethylene terephthalate have excellent transparency and surface gloss, and are beautiful and have a gas barrier. Excellent in water resistance, moisture impermeability, content resistance and storage stability. In addition, it has many advantages such as low heat generation during combustion and easy disposal because it does not damage the furnace. Therefore, it is widely used in containers (bottles) for various drinking water, seasonings, alcoholic beverages and other foods.

In recent years, so-called hot fill for filling a liquid such as juice kept at 80 to 95 ° C. into a container made of polyester by this biaxial stretch blow molding, or past-riding by hot shower at 60 to 80 ° C. has been performed. Therefore, not only heat resistance but also pressure resistance due to the pressure caused by the temperature difference between the time of filling the liquid and the time of cooling has been demanded. Further, the capacity of polyester containers made by such biaxially stretch blow molding has been increasing, and large bottles having a capacity of more than 2 liters have been manufactured, which is caused by the weight of the contents. Resistance to pressure is also required. Such an internal pressure is particularly remarkable when a carbonated beverage is used as the filling material.

In such a polyester container, since the weight of the contents is heavily applied to the lower portion of the container body, there is a problem that it is easily deformed during past-riding. Therefore, heat resistance and pressure resistance have been improved by forming irregularities on the wall surface of the lower portion and the bottom portion of the body of the polyester container. However, when unevenness is formed on the wall surface of the container, the wall thickness of that portion becomes thin, so that the heat and pressure resistance is reduced and creep deformation is likely to occur, and there is a possibility that the lower part and the bottom part of the body part may largely swell. is there.

Therefore, when such a biaxially stretch blow-molded container (bottle) is used as a container for contents having a high internal pressure such as carbonated beverages, the bottom is made spherical so as to improve the internal pressure resistance. A so-called base cup is attached to it. The container with a base cup has excellent self-sustaining stability, and the bottom portion is reinforced, but the cost increases because the step of manufacturing the base cup in a separate step and then attaching the base cup to the container body increases. In addition, since the base cup is usually molded with a resin different from that of the container body, the container equipped with the base cup is inferior in recyclability.

Therefore, various irregularities are formed on the bottom of the container to reinforce the bottom of the container, and a container having a structure for ensuring self-standing without a base cup (for example, JP-A-61-91).
70, JP-A-2-57545, etc.) have been developed and put to practical use.

However, in these pressure-resistant self-supporting containers, the wall thickness of the bottom portion is as shown in FIG.
Since it is sandwiched between the leg portions and is not stretched, it is significantly thicker than the leg portions 11 '. That is,
The draw ratio of the valley portion 12 'is extremely small. Therefore, there is a problem in that the heat resistance and pressure resistance of the valley portion at the bottom are not sufficient.

Therefore, it is an object of the present invention to provide a self-supporting container having good heat resistance and pressure resistance at the bottom.

Another object of the present invention is to provide a method for manufacturing the above container.

[0010]

As a result of earnest research in view of the above-mentioned object, the present inventor has found that in a heat-resistant pressure self-supporting container having a bottom portion in which the leg portions of the container bottom portion are formed in the circumferential direction, each leg portion and the space between the leg portions are provided. If the wall thicknesses of the valleys are made approximately equal, the heat resistance and pressure resistance of the bottom can be improved, and such a container cannot be formed by a single biaxial stretch blow molding process. Manufacture by heat-shrinking a primary blow-molded product obtained by biaxial stretch blow-molding, and then performing biaxial stretch blow-molding again so that the legs and valleys of the primary blow-molded product are inverted. I found that I can do it. The present invention has been made based on the above findings.

That is, the heat and pressure freestanding container of the present invention has a bottom portion in which a plurality of leg portions forming a ground contact portion are formed in the circumferential direction, and each leg portion and the valley formed between them are formed. It is characterized in that the thickness of the parts is almost equal.

The method of the present invention for producing the above heat-resistant and pressure-free container is (a) a plastic parison made of a mouth portion, a body portion and a bottom portion is prepared, and (b) the parison is biaxially stretch blow molded. To form a primary blow-molded body having a valley and a leg at positions corresponding to the leg and the valley of the container, respectively.
Shrink at 150 ° C, and (d) place the shrink-molded body obtained in (c) in a blow mold having a cavity having a shape corresponding to the container, in which case the leg and valley of the shrink-molded body are placed. The parts are positioned so as to correspond to the valley and the leg of the cavity, respectively, and (e) the shrink-molded body is biaxially stretch-blow-molded to invert the leg and the valley, and thus the desired shape is obtained. It is characterized by molding a container.

The present invention will be described in detail below. [1] Resin Component First, the resin that constitutes the heat resistant and pressure independent container of the present invention will be described.

A polyester resin is suitable as the resin constituting the biaxially stretch blow molded heat resistant pressure vessel of the present invention. As the polyester resin, a thermoplastic resin composed of saturated dicarboxylic acid and saturated dihydric alcohol can be used. Saturated dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyldicarboxylic acids, diphenoxyethanediethanedicarboxylic acids Aromatic dicarboxylic acids such as adipic acid,
Aliphatic dicarboxylic acids such as sebacic acid, azelaic acid and decane-1,10-dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used. Further, as the saturated dihydric alcohol, ethylene glycol,
Propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol,
Uses aliphatic glycols such as dodecamethylene glycol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) propane, and other aromatic diols can do. The preferred polyester is
Polyethylene terephthalate composed of terephthalic acid and ethylene glycol.

The polyester resin used in the present invention has an intrinsic viscosity of 0.5 to 1.5, preferably 0.55 to 0.8. Further, such polyesters are produced by melt polymerization and subjected to a reduced pressure treatment or a heat treatment in an inert gas atmosphere at a temperature of 180 to 250 ° C., or a low molecular weight oligomer or acetaldehyde of a low molecular weight polymer obtained by solid state polymerization. Those with a reduced content are preferable.

Further, in the present invention, a portion such as a mouth portion, which is particularly required to have heat resistance, can have a multilayer structure of the above-mentioned polyester and heat-resistant resin. Examples of the heat-resistant resin include polyarylate, polycarbonate, polyethylene naphthalate, polyacetal, polysulfone, polyether ether ketone, polyether sulfone, polyetherimide, polyphenylene sulfide, and a blend polymer of these resins and polyethylene terephthalate, and the above. Blend polymer between heat resistant resins, further blend polymer of two or more kinds of the above heat resistant resins with polyethylene terephthalate, U polymer (Unitika, blend polymer of polyarylate and polyethylene terephthalate), J320 (Mitsui Petrochemical Industry) (A blended polymer of polyarylate, polycarbonate and polyethylene terephthalate manufactured by K.K.) can be used. U polymers are preferably used.

In the polyester resin and heat-resistant resin used in the present invention, additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, UV deterioration inhibitors, antistatic agents, antibacterial agents, etc. An appropriate amount of the resin or the like can be added.

[2] Heat Resistant Freestanding Container FIG. 1 shows a bottom structure of the heat resistant freestanding container 1 according to one embodiment of the present invention, (a) is a bottom view, and (b) is (a). It is an AA sectional view.

Although only the bottom structure of the container 1 is shown in FIG. 1, the shape of parts other than the bottom, such as the mouth, shoulders, and body of the container 1, depends on the purpose of use of the container. It may be appropriately set to various shapes found in conventional plastic containers. A feature of the container of the present invention is its bottom shape.

In the embodiment shown in FIG. 1, at the bottom of the container 1,
Five leg parts 11 and a valley part 12 between them are formed. The five leg portions 11 and the valley portions 12 have almost the same thickness except for the central portion S. For example, the thickness T ₁ of the leg portion 11, the thickness T ₂ of the valley 12 are approximately equal. The wall thickness T ₃ of the central portion S is larger than the wall thicknesses T ₁ and T ₂ of the leg 11 and the valley 12.

In this way, in the bottom portion having the body portion and the valley portion having the substantially equal wall thickness, the average stretch ratio (expressed by the area magnification) is substantially equal over the body portion 11 and the valley portion 12,
Specifically, it is preferably 1.5 to 14 times, particularly 3 to 10 times. If the draw ratio is less than 1.5 times, the bottom portion having sufficient heat resistance and pressure resistance cannot be formed, which is not preferable.

In such a heat and pressure freestanding container of the present invention, since the valley portion also has a sufficient stretch ratio, the valley portion is not deformed by hot fill or the like and has excellent heat resistance and pressure resistance.

[3] Manufacturing Method (a) Manufacturing of Parison FIG. 2 is a sectional view schematically showing an example of the parison that can be used in the present invention. Parison 20 shown in Figure 2
Comprises a mouth portion 21 having a support ring 24, a substantially cylindrical body portion 22, and a bottom portion 23. Parison 20 body 22
And the thickness of the bottom portion 23 may be substantially the same. This parison
20 can be formed by injection molding the above-mentioned polyester resin.

(B) Manufacture of Primary Blow Molded Body In the primary blow molding of the parison 20, the entire parison is 80 to 15
Perform by heating to 0 ° C. This parison 20 is biaxially stretch blow molded to obtain a primary blow molded body 30 having a bottom shown in FIG. In this primary blow-molded body, the valley portions 32 are thicker than the leg portions 31. For example, the wall thickness T ₅ of the valley portion 32
Is larger than the wall thickness T ₄ of the leg portion 31. The thickness T ₆ of the central portion S is slightly larger than the thickness T ₅ of the valley 32,
It is significantly larger than the wall thickness T ₄ of the leg portion 31.

Such a primary blow-molded body is blow-molded so that the positions corresponding to the leg portion and the valley portion of the final product are the valley portion and the leg portion, respectively, in the mold of the primary blow-molded body. It can be obtained by The primary biaxial stretching blow molding method itself of the parison 20 can be performed by a usual method. In the primary biaxial stretch blow molding, the stretch ratio (expressed by surface area ratio) is preferably 1.5 to 14 times.

(C) Manufacture of shrink-molded article Next, the primary blow-molded article obtained as described above is used.
When the internal pressure is reduced while heating to ˜150 ° C., preferably 100 to 130 ° C., the primary blow molded product shrinks as shown by the dotted line. In the shrink molding 40 thus obtained,
The wall thickness of the bottom portion is larger than that of the primary blow-molded body at any place. Further, the relationship of the wall thicknesses of the leg portion, the valley portion, and the central portion is the same as that of the above primary blow-molded body. At this time, it is preferable that the pressure in the primary blow-molded body is gradually reduced.

(D) Secondary Stretch Blow Molding Subsequently, as illustrated in FIG. 4, the shrink-molded body 40 (broken line in the figure) is biaxially stretch-blow molded again to form a heat-resistant pressure container 50 of interest. To manufacture. At this time, the legs 41 of the shrink molding 40
And the troughs 42 are positioned so as to correspond to the troughs and legs of the mold of the heat-resistant pressure container 50.

By carrying out the biaxial stretch blow molding by positioning in this way, the valley portion 32 which is not sufficiently stretched in the primary blow molded product is stretched by the secondary biaxial stretch blow molding and finally obtained. It becomes the leg part 51 of the container that can be
The bottom of the container where the leg 31 of the next blow-molded body is finally obtained
Since the thickness is 52, the wall thickness (T ₅ ) of the leg portion 31 at the bottom of the primary blow-molded body is almost unchanged, and the wall thickness (T ₅ ) of the valley portion 32 (T ₅ ).
_{Since 8} ) is greatly reduced, T ₁ ≈T ₂ .

Although the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. For example, as illustrated in FIG. 5, a recess is formed in the center of the bottom of the container.
By forming 61 and increasing the draw ratio of the central portion of the bottom of the container, the heat resistance and strength of the central portion of the bottom of the container can be further improved.

[0030]

The present invention will be described in more detail by the following examples.

Example 1 Polyethylene terephthalate resin (Mitsui PETJ125 (manufactured by Mitsui Petrochemical Industry Co., Ltd.) as a crystalline plastic
Was used to mold the parison shown in FIG. 2 by the injection molding method.

After heating and holding this parison at 100 ° C.,
By the biaxial stretch blow molding method, a primary blow-molded product was produced in which the legs and valleys of the final product corresponded to the valleys and legs, respectively. The draw ratio at this time was about 10 times.

From the center of the bottom of this primary blow-molded product, 1
The wall thickness along lines OX and OY at a distance of 0-40 mm was measured at 5 mm intervals. Moreover, the difference in these wall thicknesses was calculated. The results are shown in Table 1.

Next, the inside of the primary blow-molded product was depressurized while the lower part and the bottom part of the body were heated and maintained at 80 ° C. to shrink the entire container by about 40%.

This shrink-molded body was installed in the mold for the heat-resistant pressure-resistant free-standing container described above so that the legs of the shrink-molded body corresponded to the valleys and the valleys corresponded to the legs, respectively, and kept at 80 ° C. Second stretch blow molding was performed. The average draw ratio of the bottom portion of the heat-resistant, self-supporting container thus obtained was about 5 times.

Thus, a container having a bottom shape shown in FIG. 1 (capacity 1.5 liters, diameter 10 cm) was obtained. Line OX at a distance of 10-40 mm from the center of the bottom of this container
And the wall thickness along OY was measured at 5 mm intervals. Moreover, the difference in these wall thicknesses was calculated. The results are shown in Table 2.

1st thickness from the center O at the bottom of the surface to the following position ^* region of the center S primary blow molded product 10mm 15mm thickness along line OX ^** 3.2 2.8 thickness along line OY ^*** 2.6 2.1 Thickness difference 0.6 0.7

Table 1 (Continued) Thickness from the center O of the bottom at the following position ^* Area with legs and valleys Primary blow molded product 20 mm 25 mm 30 mm 35 mm 40 mm Thickness along line OX ^** 0.7 0.4 0.5 0.45 0.4 Wall thickness along line OY ^*** 2.6 1.2 0.6 0.45 0.4 Wall thickness difference −1.9 −0.8 −0.1 0.00 Note) *: Unit is mm. **: Legs in the area 20 mm or more from the center O. ***: In the area 20 mm or more from the center O, there is a valley.

Second wall thickness from the center O of the bottom of the table to the following position ^* region of the center S heat resistant and pressure freestanding container 10mm 15mm wall thickness along the line OX ^** 2.8 2.4 wall thickness along the line OY ^*** 3.0 2.2 Thickness difference −0.2 0.2

Table 2 (Continued) Thickness from the center O of the bottom to the following position ^* Area with legs and valleys Heat resistant pressure resistant freestanding container 20mm 25mm 30mm 35mm 40mm Thickness along line OX ^** 0.4 0.4 0.4 0.4 0.35 Wall thickness along line OY ^*** 0.4 0.1 0.45 0.4 0.35 Wall thickness difference 0 0.3 -0.05 0.00 Note) *: Unit is mm. **: Legs in the area 20 mm or more from the center O. ***: In the area 20 mm or more from the center O, there is a valley.

As is clear from Tables 1 and 2, the heat-resistant and pressure-standing container of Example 1 has a lower leg than a primary blow-molded body (corresponding to a container molded by a single biaxial stretch blow molding). There is only a slight difference in wall thickness between the valley and the valley.

[0042]

As described above in detail, in the present invention,
The primary blow-molded product obtained by biaxial stretch blow molding is heat-shrinked, and then the biaxial stretch blow-molding is again performed so that the legs and the valleys of the primary blow-molded product are reversed. Since the container is manufactured, the thickness of each leg and the valley between them is substantially equal, and the heat resistance and pressure resistance of the bottom are good.

The pressure-resistant container of the present invention as described above is suitable for a bottle of juice or the like which is subjected to past-rising by hot fill or hot shower, a container of carbonated drink, retort food or the like.

[Brief description of drawings]

FIG. 1 shows a bottom structure of a container according to an embodiment of the present invention, (a) is a bottom view of the container, and (b) is a vertical cross-sectional view of the bottom of the container.

FIG. 2 is a cross-sectional view schematically showing an example of a preformed body forming the container shown in FIG.

FIG. 3 is a vertical cross-sectional view showing a bottom portion of a primary blow-molded body.

FIG. 4 is a vertical cross-sectional view showing a state in which a heat-shrinkable molded body is subjected to biaxial stretch blow molding again.

FIG. 5 is a vertical sectional view showing a bottom structure of a container according to another embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view of a bottom portion of a conventional heat-resistant and pressure-standing container.

[Explanation of symbols]

 1,50 ・ ・ ・ Heat-resistant freestanding container 11,31,51 ・ ・ ・ Legs 12,32,52 ・ ・ ・ Valley 20 ・ ・ ・ Parison 21 ・ ・ ・ Mouth 22 ・ ・ ・ Body 23 ・ ・・ Bottom 24 ・ ・ ・ Support ring 30 ・ ・ ・ Primary blow-molded body 40 ・ ・ ・ Shrinkage-molded body 61 ・ ・ ・ Center recess at the bottom

Claims (2)

[Claims] 1. A heat-resistant pressure self-supporting container having a bottom portion in which a plurality of legs forming a grounding portion are formed in the circumferential direction,
A heat-resistant pressure self-supporting container, wherein the leg portions and the valley portions formed between them are substantially equal in wall thickness. 2. The method for manufacturing a heat and pressure free-standing container according to claim 1, wherein (a) a plastic parison having a mouth portion, a body portion and a bottom portion is prepared, and (b) the parison is biaxial. By stretch-blow molding, a primary blow-molded body having a valley portion and a leg portion at positions corresponding to the leg portion and the valley portion of the container is formed, and (c) the primary blow-molded body is
Shrink at ~ 150 ° C, (d) place the shrink-molded body obtained in (c) above in a blow mold having a cavity having a shape corresponding to the container, in which case the shrink-molded body's legs and Positioning so that the valley corresponds to the valley and the leg of the cavity, respectively, (e) by biaxially stretch blow molding the shrink-molded body, the leg and the valley are inverted,
A method comprising molding a container having a desired shape.