JP2003103607A - Bottom structure of heat-resistant bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the bottom structure of a heat-resistant bottle capable of reducing the consumption of a resin and achieving weight reduction while ensuring heat resistance. SOLUTION: The degree of crystallization of the bottom of the heat-resistant bottle 10 is set to 10-45% and the degree of crystallization due to stretching thereof is set to 5-30%. By this constitution, heat resistance is ensured and the wall thickness of this bottle 10 is reduced at the same time to achieve the weight reduction of the bottle as a whole. Further, over-stretching is prevented simultaneously with the enhancement of heat resistance to obtain the heat-resistant bottle excellent in various physical properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant bottle bottom structure, and more particularly to polyethylene terephthalate (P).
It is possible to make the bottle lighter and thinner while maintaining the heat resistance of (ET).

[0002]

2. Description of the Related Art Conventionally, a bottomed tubular preform is injection-molded using a polyester resin such as polyethylene terephthalate, and the obtained preform is heated and heated.
It has been carried out to perform a biaxial stretch blow molding to produce a bottle-shaped container, the obtained bottle-shaped container, transparency,
It has excellent surface gloss, impact resistance, gas barrier properties, etc. and is widely used as a container for various beverages, foods, liquid detergents, etc.

[0003] In such a bottle-shaped container for beverage, the contents are hot filled, or after filling the contents,
In some cases, heat sterilization or heat sterilization is performed, and the bottle-shaped container is required to have heat resistance against these temperatures.

A bottle having such heat resistance cannot be obtained only by molding by a general blow molding method, and various blow molding methods which provide heat resistance have been proposed.

For example, in the method of molding a bottle having heat resistance and pressure resistance described in Japanese Patent Application Laid-Open No. 5-200839, the longitudinal direction is 1.0 to 1.
Using a primary blow molding die having a cavity of 3 times and a lateral direction of 0.6 to 1.0 times, the body part and the bottom part below the neck part are stretch-blown at an area ratio of 4 to 22 times 1.
The secondary blow molding step is followed by a secondary blow molding step in which the primary molded article molded by the primary blow molding is heated at 110 ° C. to 255 ° C. and then blow molded.

According to such a molding method, all the parts except the neck and neck and the whitened part just below the neck are stretched, especially the bottom part which is the weakest part because it is not stretched in the conventional bottle, so that heat resistance The pressure resistance is increased.

Further, the method for producing a heat-resistant and pressure-resistant self-supporting container described in JP-A-8-20064 is a method for producing a container made of a saturated polyester resin composed of a mouth neck portion, a shoulder portion, a body portion and a bottom portion. Then, the body of the bottomed tubular parison, excluding the mouth and neck, is 0.2 to 5.0 times in the longitudinal direction and 0.3 to 5 in the circumferential direction with respect to the size of the body of the container having the final shape. Including a primary blow molding step of stretching to 0.0 times, a secondary blow molding step of performing blow molding after heating the primary blow molded product at 120 to 250 ° C., and a step of crystallizing the bottom of the container. I have to.

According to such a manufacturing method, the body portion is stretched, contracted and re-stretched, and the bottom portion, which is difficult to re-stretch, is partially crystallized, whereby heat resistance and pressure resistance are enhanced.

[0009]

However, it is not possible to provide a secondary blow molding process including a primary blow molding process and a secondary blow molding process.
In the heat-resistant bottle manufactured by the step blow molding method, the body has a high draw ratio and is thinned,
mm, the stretch ratio of the heel part down to the lower part of the torso increases and the wall thickness is reduced, whereas the bottom sloped part and the bottom top face part forming the bottom recessed part formed in the center of the bottom part are sufficiently stretched at the bottom part. However, there is a problem that it becomes relatively thick.

On the other hand, in the case of bottle-like containers such as PET bottles for beverages, there is an increasing demand for reduction of the amount of resin used and weight reduction with the enforcement of the Recycling Law. It is desired to develop a heat resistant bottle that can be used in a reduced thickness by reducing the amount used.

The present invention has been made in view of the above problems of the prior art, and it is an object of the present invention to provide a bottom structure of a heat resistant bottle which can reduce the amount of resin used and reduce the weight while ensuring heat resistance. To do.

[0012]

[Means for Solving the Problems] Therefore, as a result of intensive studies on reducing the weight of heat-resistant bottles manufactured by the conventional two-stage blow molding method, it has been possible to reduce the thickness of the bottom of the heat-resistant bottles as final products. It has been found that the aim is to reduce the weight of the entire bottle, and the bottom structure of the heat-resistant bottle of the present invention has been completed.

In order to solve the above-mentioned problems, the bottom structure of the heat-resistant bottle according to claim 1 of the present invention is a heat-resistant bottle obtained by blow-molding a bottomed tubular preform made of polyester resin. Crystallinity of the bottom is 10-45%
By setting the crystallinity of the bottom portion in such a range, it becomes possible to ensure heat resistance and at the same time reduce the thickness and reduce the weight of the entire bottle. .

The bottom structure of the heat-resistant bottle according to claim 2 of the present invention has, in addition to the structure according to claim 1, a crystallinity of 5 to 30% of the crystallinity of the bottom by stretching.
By setting the crystallinity by stretching the bottom portion in such a range, it is possible to improve the heat resistance and at the same time prevent over-stretching and to provide excellent heat resistance in various physical properties. I am making it into a bottle.

Further, the bottom structure of the heat-resistant bottle according to claim 3 of the present invention is a heat-resistant bottle formed by blow molding a bottomed tubular preform made of polyester resin, and the bottom has a mass. It is characterized in that it is 3% or more and less than 8% with respect to the mass of the entire bottle, and by setting the mass of the bottom part in such a range, the bottom part becomes extremely thin and the strength decreases. In addition, it is designed to hold down the necessary thickness of the heel.

Here, the bottom of the heat-resistant bottle means a bottom portion inside from the grounding portion when the bottle is self-supporting, and usually a portion which is blow-molded by a bottom mold.

Further, when the bottom recess is provided as the bottom, it is composed of the ground contact portion, the bottom sloped portion, and the bottom top surface portion, and the sloped peripheral surface of the bottom recessed portion formed at the center of the bottom portion is the bottom sloped portion and the bottom recessed portion. The top surface is called the bottom top surface part.

10 mm from the grounding part of the body
The part following the upper part of the trunk is called the heel part.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a notched part of a body portion according to an embodiment of a heat resistant bottle bottom structure of the present invention, and FIG. 2 is a molding process in each step in the case of two-stage blow molding of a heat resistant bottle. It is explanatory drawing of the schematic shape of a product. In addition, in FIG. 1, the wall thicknesses of the body portion and the bottom portion which are notched and shown are merely schematic and do not show the actual wall thicknesses.

The heat-resistant bottle 10 is composed of, for example, an unstretched mouth portion 11 and a support ring 12, a stretched shoulder portion 13, a body portion 14 and a bottom portion 15 and has a self-sustaining shape. The bottom part 15 is an inner part of the grounding part 16 which is a part of the lower end of the body part 14 that grounds in a self-supporting state, and a bottom recessed part 17 recessed upward is formed in the center part thereof. It is composed of a bottom top surface portion 17b. Further, of the lower end portion of the body portion 14, up to 10 mm above the body portion 14 is referred to as a heel portion 18, which is a portion that needs to secure rigidity and strength in order to make the bottle self-supporting.

Further, a waist portion 14a for constriction is formed on the body portion 14, and a panel-shaped reduced pressure absorbing portion 14b for absorbing deformation due to negative pressure inside the bottle.
Is formed, for example, the waist portion 14a is formed at one central portion, and the depressurized absorption portion 14 is provided at a plurality of locations above and below in the circumferential direction.
b is formed. The position and the number of the waist portion and the reduced pressure absorbing portion for reinforcement are appropriately changed depending on the contents and filling conditions.

Such a heat-resistant bottle 10 is molded by a two-step blow molding method, for example, after heating the temperature of a bottomed cylindrical preform 20 obtained by injection molding of polyethylene terephthalate (PET), By setting in the primary blow mold 30 and performing biaxial stretch blow molding, an intermediate molded product 31 that is largely stretched compared to the final product is molded, taken out and heat set (thermal crystallization) to heat. After obtaining the contracted intermediate, secondary blow mold 4
By setting it in 0 and performing secondary blow molding, the heat-resistant bottle 10 of the final product having a desired size and shape is molded.

The heat-resistant bottle 10 as the final product is molded by the two-stage blow molding method to ensure heat resistance, and at the same time, the weight is reduced and the amount of resin used is reduced as much as possible. As a structure, the crystallinity of the resin of the bottom portion 15 is set to 10 to 45%, preferably 20 to 43%.

When the degree of crystallinity of the bottom portion 15 of the heat resistant bottle 10 is less than 10%, heat resistance cannot be imparted due to insufficient crystallization by both crystallization by stretching and crystallization by heat. On the other hand, in order to set the crystallinity of the bottom portion 15 of the heat resistant bottle 10 to a value exceeding 45%, the molding itself can be performed by applying heat at a low temperature for a long time, but industrial continuous production is possible. Not applicable to.

Therefore, the crystallinity of the bottom portion 15 which can impart heat resistance and is suitable for industrial production is 10 to 45.
It will be in the range of%.

In order to obtain the crystallinity of the bottom portion 15 of the heat resistant bottle 10 as described above, it can be given by combining crystallization by stretching by two-stage blow molding and crystallization by heat, and a heat resistant bottle is obtained as a final product. The stretched crystallinity of the bottom portion 15 of 10 is 5 to 30%, preferably 10 to 30%.

When the stretched crystallinity of the bottom portion 15 is 5% or less,
The heat resistance cannot be improved by the stretched crystal. If the stretched crystallinity of the bottom portion 15 exceeds 30%, overstretching results in local shrinkage (uneven shrinkage).

Thus, in the heat resistant bottle 10, the bottom portion 1
Since the crystallinity of No. 5 was increased or the stretched crystallinity of the crystallinity was increased, in the conventional heat-resistant bottle in which the preform was biaxially stretch-blow-molded by the single-stage blow molding, almost no stretching was performed. The bottom part that cannot be crystallized can be stretched to increase the degree of crystallinity, and the bottom part 15 can be stretched sufficiently even when compared with the heat-resistant bottles produced by the two-step blow molding that has been performed so far. By doing so, the crystallinity can be increased, and as a result, the wall thickness of the bottom portion 15 can be reduced, so that the weight of the heat resistant bottle 10 itself can be reduced.

For example, in the case of a 500 ml PET bottle, the weight has hitherto been 28 to 28 in the case of single-stage blow molding.
The weight of 32 g can be reduced to 25 to 26.5 g in the heat-resistant bottle 10 that is two-stage blow molded, and the measurement result of the wall thickness of the bottom portion 15 in the case of the PET bottle of 26.5 g is 1 Compared with the case of step blow molding,
As shown in FIG. 3, the average thickness of the preform is 2.0 to
Since it is 3.5 mm, it can be seen that the bottom portion 15 is sufficiently stretched and thinned.

Table 1 shows the result of measuring the crystallinity of each part in the case of the above 500 ml PET bottle. From the table, the grounding part 16 and the bottom recess 17 (constituting the bottom part 15) The bottom concave portion 17 is composed of a bottom inclined portion 17a and a bottom top surface portion 17b) and has a high crystallinity, and for example, a prismatic 26.5 g heat-resistant bottle 1
In the case of 0, the crystallinity of the grounding portion 16 is 4
1.27%, the bottom inclined portion 17a is 39.63%, and the bottom top surface portion 17b is 34.22%.

[0031]

[Table 1]

On the other hand, in this heat resistant bottle 10, the bottom 1
Since the crystallinity of No. 5 is increased to reduce the weight and the thickness, the bottom portion 1 with respect to the total mass of the heat resistant bottle 10 is used.
The mass ratio of 5 is decreased, and the range is 3% or more and less than 8%.

If the mass distribution of the bottom portion 15 is less than 3%,
The bottom portion 15 becomes too thin, resulting in extremely low strength. When the mass distribution of the bottom portion 15 is 8% or more, the meat to be applied to the heel portion 18 tends to be biased toward the bottom portion 15 side, which adversely affects the strength of the heel portion 18.

In the conventional heat-resistant bottle, the mass distribution at the bottom is 11 to 12%, and the heat-resistant bottle 10 of the present invention is designed to reduce the weight of the heat-resistant bottle as a whole by reducing this. By increasing the crystallinity by stretching and reducing the thickness, weight reduction is achieved while ensuring heat resistance.

From the strength required for the heat-resistant bottle 10, the mass distribution of the bottom portion 15 is set to a range of 3% or more and less than 8%, and the mass distribution of the heel portion 18 is set larger than the value of the bottom portion 15. is there.

In a conventional two-stage blow-molded heat-resistant bottle, the heel portion is more easily stretched and thinner than the bottom portion, and the mass of the heel portion is usually smaller than the value of the bottom portion. Met. In other words, conventional heat-resistant bottles have to be stretched to a thickness that can secure the necessary strength in the heel portion, and for this reason, the bottom portion cannot be stretched sufficiently, resulting in a thick wall. It was

On the other hand, in the heat resistant bottle 10,
At the stage of the primary blow molding in the two-stage blow molding, the bottom portion 15
To allow the mass of the bottom portion 15 to be reduced, and the shape of the preform 20 to ensure the wall thickness of the heel portion 18. In the heat-resistant bottle 10 as the final product, the heel portion 18 is Mass is bottom 1
The mass is larger than that of No. 5, so that the required strength can be secured.

For example, Table 2 shows the measurement results of the mass of each part of a 500 ml heat resistant PET bottle and its distribution in comparison with the case of a conventional heat resistant bottle.

As is clear from this table, the bottom mass is 11.07% of the total mass of the heat resistant bottle.
It is significantly smaller than 3.47 to 4.19%, and in the conventional heat resistant bottle, the mass of the heel part is smaller than that of the bottom part. It can be seen that, even though the weight is reduced and the overall mass is reduced, the mass itself of the heel portion 18 is equal to or more than that, and is larger than the bottom portion 15.

That is, in this heat-resistant bottle 10, as is clear from comparison with a bottle having the same capacity, for example, 500 ml, the bottom portion 15 can be made lighter and thinner, and the heel portion 18 that requires strength can be It can be seen that it is possible to secure the same thickness as before and prevent deterioration of strength.

[Table 2]

Next, the molding of the heat resistant bottle 10 having such a bottom structure by the two-stage blow molding method will be specifically described with reference to FIGS. 2 and 4.

The following preform 20 is used for the two-step blow molding of the heat resistant bottle 10.

In the preform 20, the lower part (corresponding to the lower part of the body) 21a of the side wall part 21 of the preform 20 corresponding to the lower part of the body part 14 (the lower part of the body) from the grounding part 16 of the heat-resistant bottle 10 after blow molding. As shown in FIG. 2 (a), a thick portion 22 that is thick without steps is provided, and this thick portion 22 is a line parallel to the central axes of the outer surface and the inner surface of the side wall portion 21 (vertical line). By changing the inclination with respect to (), it is formed so as to thicken toward the bottom portion 23 without a step.

Further, using this preform 20 1
In the next blow molding, in order to ensure heat resistance,
1 and the support ring 12 of the other portion to be stretched, the portion corresponding to the waist portion 14a for reinforcement should be thickened to some extent, and the other portion should be stretched as uniformly as possible so that uneven thickness does not occur. Along with
The bottom portion 15 of the heat resistant bottle 10 also needs to be uniformly and sufficiently stretched so that uneven thickness does not occur.

Therefore, in this two-stage blow molding method, at the stage of the intermediate molded product 31 obtained by the primary blow molding,
Reinforcing waist portion 14a of the heat-resistant bottle 10 of the final product
The cavity 32 of the primary blow mold 30 is provided so that the portion corresponding to
In addition, an annular protruding portion 33 is formed corresponding to the reinforcing waist portion 14a formed on the body portion 14 of the heat resistant bottle 10 which is the final product, and the protruding portion 33 is formed in the cavity 32 of the primary blow mold 30. Size and heat-resistant bottle of final product 10
It is formed at a position corresponding to the ratio of the size of, for example, a position corresponding to the ratio of the height from the ground portion 16.

An intermediate molded product 3 to be primary blow-molded by using the primary blow mold 30 having such a protruding portion 33 formed therein.
In the case of No. 1, the protrusion 33 suppresses the stretching of the portion corresponding to the waist portion 14a during the primary blow molding, and can be stretched to be thicker than the other portions.

If the inner diameter of the annular protruding portion 33 becomes smaller, the flow of resin may be obstructed and the resin may not reach the bottom of the cavity 32. Conversely, if the inner diameter of the protruding portion 33 becomes large. Since it becomes impossible to increase the thickness by suppressing the stretching, for example, by setting the inner diameter of the protruding portion 33 of the primary blow mold 30 to 75% of the body diameter of the cavity 32, the final product The waist portion 1 of the heat-resistant bottle 10 that can be made to have a substantially uniform thickness and has a height of 80 mm from the ground portion 16 for reinforcement 1
4a could be made thicker than the body portion 14 without being thinner.

The size of the cavity 32 of the primary blow mold 30 is required for the heat-resistant bottle 10 of the final product obtained through the primary blow molding, the subsequent heat setting, and the secondary blow molding in the final step. The degree of crystallinity or stretched crystallinity is determined so that, for example, 1
Biaxially stretch blow-molding with a draw ratio of the intermediate molded product 31 to be biaxially stretch-blow molded as the next blow molding, the longitudinal ratio being 2.5 to 3.5 times, and the transverse ratio being 3.5 to 5 times. In order to reduce the wall thickness by making it highly stretched, especially the intermediate molded product 3
1. It should be possible to obtain a completely stretched state in which no meat remains at the bottom of 1.

As such a primary blow mold 30,
For example, the cavity 3 of the heat-resistant bottle 10 for 500 ml
As shown in FIG. 2B, the shape of No. 2 is, for example, a stretched length of 240 mm, a body diameter of 82 mm, and a protrusion 33 corresponding to the reinforcing waist portion 14a.

Then, the preform 20 is heated to 110 ° C. and the cavity 32 excluding the bottom portion of the primary blow mold 30.
To 140 ° C. and the bottom of the cavity 32 to 30 ° C.,
Blow gas (compressed air) at room temperature is blown for 2 seconds to perform biaxial stretch blow molding.

This biaxially stretch blow-molded intermediate molded product 31, as shown in FIG.
After shrinking in the mold at a mold temperature of 140 ° C., the product is taken out as an intermediate molded product 34 after shrinking in the mold.

For example, the stretched crystallinity of the intermediate molded product 34 thus taken out is 24.5% in the portion corresponding to the bottom portion 15 of the heat-resistant bottle 10 and the portion corresponding to the bottom inclined portion 17a of the bottom recessed portion 17. There are 2 parts corresponding to the bottom surface part 17b.
It was 2.5%.

In such a primary blow molding, if the draw ratio is small, the meat remains at the bottom of the intermediate molded product 31 and the weight of the heat resistant bottle 10 cannot be reduced, and the thick part of the bottom of the intermediate molded product 31 cannot be achieved. Becomes white due to heating during heat setting. Further, in order to secure the heat resistance of the heat resistant bottle 10 of the final product, it is necessary to set the heating temperature for heat setting within the range of 190 to 200 ° C. Even with blow molding, the heat-resistant bottle 10 of a predetermined size cannot be molded. Therefore, the stretch ratio by the primary blow molding is determined so as to satisfy these conditions.

On the other hand, in terms of the surface area of the intermediate molded article 31 which is primary blow molded by the biaxial stretch blow molding method, the surface area of the cavity 32 of the primary blow mold 30 is the final surface area. It is obtained by setting the surface area of the heat-resistant bottle 10 of the product to 1.3 to 2.0 times, preferably 1.4 to 2.0 times. Since the in-mold shrinkage occurs in the primary blow molding, the intermediate molded product 34 after the in-mold shrinkage occurs.
The surface area of 1 is 1.5 to 1.5 times, preferably 1.1 to 1.5 times the surface area of the heat resistant bottle 10 of the final product.

By molding the intermediate molded product 31 by the primary blow molding having such a surface area, a heat resistant bottle having a predetermined heat resistance and a desired size can be blow molded in two steps. it can.

For example, in the shape of the cavity 32 shown in FIG. 2 (b), the surface area is 624.007 cm ² , and the surface area of the intermediate molded product 34 after in-mold shrinkage in FIG. ² (c) is 471. 58 cm ² and the surface area of the heat-resistant bottle 10 of the final product of FIG. 6E is 420.1 cm ² , the ratio of each to the final product is 1.49 for the intermediate molded product (cavity) 31, The intermediate molded product 34 after inner shrinkage has a value of 1.12.

Reinforcing waist portion 14 thus obtained
An intermediate molded product 31 in the primary blow molding in which a is thick and other stretched portions including the bottom are thinned to be substantially uniform.
Is heat set to the intermediate molded product 34 after shrinkage in the mold.

For this heat setting, for example, a panel heater 35 is used, the surface temperature is 700 to 800 ° C., and the body surface temperature of the intermediate molded product 34 after shrinking in the mold is 190 to 90 ° C.
It is heated to 200 ° C. and the bottom surface temperature is 150 to 160 ° C., and heat set for 7.5 to 8 seconds to perform thermal crystallization. This heat setting causes heat shrinkage,
For example, the surface area of the intermediate molded product 34 after shrinking in the mold is about 0.77 times.

In the intermediate body 36 thus obtained after heat setting, the waist portion 14a for reinforcement is in a depressed state, and the heat-resistant bottle 10 of the final product has a body diameter of 67 mm in the case of a round bottle, and in the case of a rectangular bottle. The body diameter is 50 to 60 mm.

For example, the crystallinity of the bottom portion of the intermediate body 36 thus taken out after the heat setting is determined by the heat-resistant bottle 1
Bottom inclined portion 1 of bottom concave portion 17 in a portion corresponding to bottom portion 15 of 0.
The portion corresponding to 7a was 39.0%, and the portion corresponding to the bottom top surface portion 17b was 35.0%. After that, secondary blow molding is performed as a final step.

In this secondary blow molding, the secondary blow mold 4 in which the cavity 41 corresponding to the reinforcing waist portion 14a is formed in the shape of the heat resistant bottle 10 of the final product is formed.
0 is used, and blow molding is performed by blowing blow gas. Here, heated gas is used as the secondary blow gas, for example, heated air of 100 to 200 ° C. is used.

The molding conditions of this secondary blow molding are, for example, in the secondary blow mold 40, the cavity 41 is heated to 160 ° C. and the bottom of the cavity 41 is 30 to 10.
Blow molding is performed in about 2 to 2.5 seconds by heating to 0 ° C. and blowing heated air at 100 to 200 ° C. as blow gas.

In the heat resistant bottle 10 thus obtained,
The bottom portion 15 has a high degree of crystallinity and a high degree of stretched crystallinity, has no problem of whitening and has excellent heat resistance, and can be made lighter and thinner.

For example, the measurement result of the wall thickness distribution of the bottom portion obtained by blow molding the heat resistant bottle 10 for 500 ml, as described above with reference to FIG. Although omitted, it was possible to secure the strength by increasing the wall thickness of the heel portion 18.

Further, the body portion 14 can be made to have a substantially uniform thickness, and the waist portion 14a for reinforcement having a height of 80 mm from the ground contact portion 16 can be made thicker than the body portion 14.

Further, a small intermediate body 36 which is heat-shrinked by heat setting as compared with the cavity 41 of the secondary blow mold 40 is set in the secondary blow mold 40, and therefore corresponds to the waist portion 14a for reinforcement. The secondary blow molding can be performed easily without being bitten by a part and easily set in the mold 40.

Further, by using heated air as the blowing gas, shrinkage of the heat-resistant bottle when the obtained heat-resistant bottle 10 is filled with the heated contents or heat sterilization is performed after filling the contents. Can be suppressed.

For example, as a general heat resistance test, after filling at 85 ° C., shower sterilization at 75 ° C. for 3 minutes and as a high heat resistance test at 91 ° C. after shower sterilization at 75 ° C. for 3 minutes For each of the above, the results of measuring the amount of shrinkage of the bottle when the temperature of the blow gas used for the secondary blow molding was 110 ° C. and 160 ° C. and when using the blow gas at room temperature were also measured. It was found that the shrinkage amount after filling the contents can be suppressed by using it, and the shrinkage amount becomes smaller as the temperature of the blow gas is higher.

According to such a bottom structure of the heat resistant bottle 10, it is possible to reduce the weight and the amount of the resin used,
Moreover, since it is in a continuous stretched state, even when the intermediate molded product after the primary blow molding is heated and heat set, it is possible to prevent the local heat shrinkage and carry out the secondary blow molding, which results in heat resistance. Excellent bottles can be molded.

Furthermore, since the heat-resistant bottles such as PET bottles thus obtained can be made thinner,
It can be easily crushed when it is discarded, and can be easily collected for recycling.

In the above embodiment, the case of molding a plastic bottle of 500 ml has been described as a specific example, but the present invention is not limited to this and can be similarly applied to a bottle-shaped container for other volumes. .

[0072]

According to the bottom structure of the heat-resistant bottle of the present invention as specifically described above with reference to the embodiment, heat resistance can be ensured, and at the same time, the wall thickness can be reduced and the weight of the entire bottle can be reduced. Can be realized.

Further, at the same time as improving the heat resistance, it is possible to obtain a heat resistant bottle excellent in various physical properties by preventing overstretching.

Further, it is possible to obtain a heat-resistant bottle in which the bottom is prevented from being extremely thin and its strength is not lowered, and moreover, the heel portion has a necessary thickness.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a notch of a body part according to an embodiment of a bottom structure of a heat resistant bottle of the present invention.

FIG. 2 is an explanatory view of a schematic shape of a molded product in each step in the case of performing a two-stage blow molding of a heat resistant bottle according to one embodiment of the heat resistant bottle bottom structure of the present invention.

FIG. 3 is a graph showing the measurement results of the thickness of the bottom portion according to the embodiment of the bottom portion structure of the heat resistant bottle of the present invention.

FIG. 4 is a process explanatory view in the case of performing the two-stage blow molding of the heat resistant bottle according to the embodiment of the bottom structure of the heat resistant bottle of the present invention.

[Explanation of symbols]

10 Heat-resistant bottle 11 mouth 12 Support ring 13 shoulder 14 torso 14a Reinforcing waist 14b Decompression absorber 15 bottom 16 Grounding part (bottom part) 17 Bottom recess (bottom) 17a Bottom inclined part 17b Bottom surface 18 Heel part 20 preform 21 Side wall 21a Lower part (corresponding to the lower part of the body) 22 Thick part 23 bottom 30 Primary blow mold 31 Intermediate molded products 32 cavities 33 Projection 34 Intermediate product after shrinkage in mold 35 panel heater 36 Intermediate 40 Secondary blow mold 41 cavity

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 67:00 B65D 1/00 BRBA B29L 22:00 BSF F term (reference) 3E033 AA02 BA18 CA06 CA07 DA03 DA08 DB01 DD01 EA04 FA02 FA03 4F208 AA24 AG07 AG23 AH55 AR15 LA02 LA04 LG15 LG18 LG28 LH08

Claims (3)

[Claims] 1. A heat resistant bottle obtained by blow molding a bottomed tubular preform made of polyester resin, wherein the bottom has a crystallinity of 10 to 45%. Bottom structure. 2. The crystallinity of the bottom portion is 5 to 30% of the crystallinity by stretching.
Bottom structure of the heat resistant bottle described. 3. A heat-resistant bottle obtained by blow-molding a bottomed tubular preform made of polyester resin, wherein the weight of the bottom is 3% or more and 8% of the weight of the entire bottle.
Bottom structure of heat resistant bottle characterized by less than.