JPH07309320A - One-piece type heat-resistant polyester bottle and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the bottom strength by specifying a thickness of a bottom center, a birefringence index in a peripheral-thickness direction and a crystallization degree in a heat-resistant polyester bottle formed by draw-blow molding of thermoplastic polyester with a panel-rib structure for vacuum absorbing formed at a body. CONSTITUTION:In a heat-resistant polyester bottle formed by draw-blow molding of thermoplastic polyester and with a panel-rib structure for vacuum for absorbing formed on body parts 3, 4, a bottom 5 is equipped with a bottom center 12 and a peripheral contact part 11 extending outward in an axial direction in a self-standing structure. The bottle is made thin so that thickness is 0.5 to 2 times the thickness of a body center except a gate cut part of the bottom center 12, while molecules are oriented so that a birefringence index in a peripheral-thickness direction is 0.070 or more. In addition, the bottom center 12 has a crystallization degree 0.8 to 1.4 times that of the body center, and a panel 10 is also formed with a crystallization degree equal to that of the bottom center 12 or with a larger degree inside, thereby obtaining a container excellent in bottom strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-piece type heat-resistant polyester bottle excellent in bottom strength, heat resistance, reduced-pressure absorption and self-standing stability, and a method for producing the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Biaxially stretched blow molded containers of thermoplastic polyester such as those have excellent transparency and surface gloss, as well as the impact resistance, rigidity and gas barrier properties required for bottles, and are bottled containers for various liquids. That is, it is used as a bottle.

In this bottled product, a hot filling technique is known as a packaging technique for improving the storability of the contents. However, polyester bottles have the drawback of being inferior in heat resistance. To improve this, in order to prevent thermal deformation during hot filling, heat set (heat set) after molding the biaxially stretched blow container. In addition, in order to prevent deformation under reduced pressure after hot filling, it is widely practiced to form a panel-rib structure for absorbing reduced pressure on the body.

In order to make the bottle self-supporting,
It is also widely practiced to provide legs protruding axially outward and radially outward to the round bottom of the bottle, but since the center of this bottom remains in an unstretched or low stretched state, the bottle bottom is It has a structure that is vulnerable to drop impacts.

In JP-A-5-42536, a bottomed primary molded body is stretch blow molded into a secondary molded body having a hemispherical bottom in a mold, and only the bottom of the secondary molded body is heated. It is described that after shrinking, the bottom portion is further biaxially stretch blow molded into a shape capable of obtaining self-supporting property. In this method, it is also described that the thickness of the peripheral portion of the bottom was 0.36 mm, while the thickness of the central portion of the bottom was 1.16 mm.

[0006]

That is, in the conventional one-piece type self-supporting polyester bottle produced by the stretch blow molding method, the center part of the bottom remains unstretched or low stretched. In the one-piece structure in which a more complicated uneven structure is formed than in the shape, this tendency becomes more remarkable because the draw ratio of each part varies more complicatedly. For this reason, even if the bottle has no problem in terms of heat resistance, it is a problem that when the drop impact is applied to the bottom, the bottom of the bottle is cracked.

Further, in the case of a heat-resistant bottle, the reduced pressure due to the volume reduction after hot filling absorbs the reduced pressure by paneling deformation of the body panel to the inside. When the phenomenon occurs, the paneling deformation to the inside does not work, and the panel of the body part deforms asymmetrically. Known stretch blow
In the heat setting method, the degree of stretch orientation inside and outside the bottle is large, and since a high temperature mold is used, the degree of heat setting (degree of oriented crystallization) is also outside the bottle. There is a problem of going out.

Therefore, the object of the present invention is excellent in the combination of the mechanical strength and heat resistance of the bottom, the vacuum absorption and the self-sustaining stability, and the one-piece heat-resistant polyester bottle capable of hot filling the contents. And to provide a manufacturing method thereof.

[0009]

According to the present invention, a thermoplastic polyester preform is stretch blow-molded at a stretching temperature under conditions where at least the outer periphery and the bottom are not constrained to give a smooth neck and smooth surface. A step of molding into a secondary molded product having a body and a bottom, a step of heating the secondary molded product to heat-fix the body and the bottom, permitting shrinkage thereof, and a molded product in a heat treatment step. Is blow-molded in a blow-molding die, and the bottom portion has a self-supporting bottom shape including a bottom center and a peripheral grounding portion extending axially outward from the bottom center, and the body portion is a panel for absorbing reduced pressure. A method for producing a one-piece heat-resistant polyester bottle, which is excellent in the combination of bottom strength, heat resistance, reduced-pressure absorption and self-standing stability, characterized in that it comprises a step of final forming into a rib structure.

A heat-resistant polyester bottle formed by stretch blow molding of thermoplastic polyester, having a neck portion, a body portion and a bottom portion, and having a panel-rib structure for absorbing reduced pressure in the body portion, wherein the bottom portion is the bottom portion. The center part and the peripheral grounding part that extends axially outward from the center part of the bottom part are formed in a one-piece self-supporting structure.
Except for the gate cut portion, the thickness is reduced to 0.5 to 2 times, particularly 0.55 to 1.50 times the thickness of the central portion of the body portion, and the thickness is in the circumferential direction-thickness direction. Has a birefringence of 0.070 or more, particularly 0.100 or more, and the center of the bottom has a crystallinity of 0.8 to 1.4 times the crystallinity of the center of the body. Bottom strength, heat resistance, and reduced pressure absorbency, characterized by having a crystallinity of 8 to 1.3 times and a crystallinity inside or outside of the panel portion being substantially the same or larger inside. Provided is a one-piece heat-resistant polyester bottle that is excellent in combination with self-sustaining stability. By the way, the fact that the crystallinity on the inside of the panel portion is large means that the heat setting effect on the inside is large and the heat shrinkage is difficult. Therefore, the panel portion does not go out.

The central portion of the bottom excluding the gate cut portion preferably has a crystallinity of 35% or more, particularly 37% or more.

[0012]

In the production of the one-piece type heat-resistant polyester bottle of the present invention, a thermoplastic polyester preform is used.
At the stretching temperature, stretch blow molding (free blow) molding is performed under conditions where at least the outer periphery and the bottom are not constrained,
It is molded into a secondary molding with a neck, a smooth body and a bottom. By this free-blowing, the bottom portion is also stretched in an unrestrained state, so that it is thinned and molecularly oriented in the same manner as the body portion.

Then, the secondary molded product is heated to heat-fix the body and the bottom and to shrink them freely.
By this heat treatment, in the body and the bottom, the residual strain of the vessel wall is relaxed and the oriented crystallization of the vessel wall polyester proceeds. At this time, the body is stretch-blown in a smooth state, the bottom is also stretch-blown, and in this state, heat treatment and strain relaxation are performed, so that the oriented crystallization of the vessel wall is extremely uniform. Has become.

Finally, the molded product in the heat treatment step is blow-molded in a blow molding die, and the round bottom part is composed of a central part of the bottom part and a peripheral ground part extending axially outward from the central part of the bottom part. The body is finally formed into a self-supporting bottom shape into a vacuum-absorbent panel-rib structure. Of course, the mold used in this final blow molding process must match the free-standing bottom shape of the final container and the reduced pressure absorption structure of the panel-rib.
In this final blow molding step, it is possible to impart self-supporting property to the bottom of the container and absorb the reduced pressure to the body part of the container.

In the present invention, the above-mentioned free blow molding,
Through the combination of heat treatment and final blow molding, the thickness at the center of the bottom is 0.5 to 2 times, especially 0.55 to 1.5 times the thickness of the center of the body, excluding the gate cutting part. Is thinned and molecularly oriented so that the birefringence index in the circumferential direction and the thickness direction is 0.070 or more, and the crystallinity is 0.8 to 1.4 times the crystallinity of the central portion of the body. It is a remarkable feature of the present invention that the oriented crystallization can be performed as described above, and such thinning of the bottom portion and oriented crystallization are achieved.

By forming the central portion of the bottom portion and the peripheral ground portion extending axially outward from the central portion of the bottom portion on the oriented and crystallized bottom portion, not only self-sustaining stability is obtained, but also Due to the uniform oriented crystallization, the bottom portion has excellent impact resistance, and further, thermal deformation of the self-supporting structure of the bottom portion is prevented, and excellent self-sustaining stability is maintained even after hot filling.

Further, in the final blow molding step, the reduced pressure absorbing structure composed of the panel portion and the ribs is formed on the body portion which is uniformly oriented and crystallized, so that the crystallinity inside and outside the panel portion can be improved. Since it is almost the same or the inside is larger, uneven heat deformation during hot filling is prevented.
When the reduced pressure occurs due to cooling, the panel effectively causes paneling deformation, which prevents asymmetric deformation of the container.

In the present specification, the birefringence means the value measured by the method described later, while the crystallinity means the following formula (1). In the formula, ρ: measured density (g / cm ^-3 ) ρam: amorphous density (1.335 g / cm ^-3 ) ρc: crystal density (1.455 g / cm ^-3 ) Density measurement is n-heptane-carbon tetrachloride A system density gradient tube (Ikeda Rika Co., Ltd.) is prepared and is performed at 20 ° C. The value obtained by

In FIG. 1 (side sectional view) and FIG. 2 (bottom view) for explaining an example of the structure of the polyester bottle of the present invention, the bottle 1 has a neck portion 2, and a frustum or a rotary body in the neck portion. It is composed of a tubular lower body portion 4 connected through the upper body portion 3 and a bottom portion 5 connected to the lower end of the lower body portion. A screw portion 6 for fastening a cap and a support ring 7 are formed on the neck portion 2. Between the lower body portion 4 and the upper body portion 3, a concave bead portion 8 that cushions during heating and cooling is provided.
Is formed, and a stepped portion 9 is formed between the lower body portion 4 and the bottom portion 5 to provide a cushioning function during heating and cooling.

The lower body portion 4 has a substantially rectangular panel portion 10
The rib portion 11 as a frame body for the panel portion is arranged in the circumferential direction to form a reduced pressure absorbing mechanism. That is, the panel portion 10 is deformed by the paneling in which the panel portion 10 is retracted inward so that the reduced pressure can be absorbed.

The bottom portion 5 comprises a bottom central portion 12 and a peripheral grounding portion 13 extending axially outwardly from the bottom central portion. In this specific example, the bottom portion 5 comprises a ring-shaped peripheral grounding portion 13 and a dome-shaped inwardly recessed bottom central portion 1
It consists of 2. Bottom central part 10 is a peripheral grounding part 11
It is recessed upward by a height H, and as long as this height is maintained, the self-sustaining stability of the bottle is maintained.

FIGS. 1 and 2 also show a sample position of the thickness of the bottle container wall. The center part of the bottom part is approximately the center part, the center part of the bottom part is the peripheral part c, and the middle part thereof and the body part. There are intermediate portions D, and these positions are sample positions in the example described later. See Tables 1 and 2 in the examples below. In the bottle of the present invention, the thickness of the bottom center part a, which is most likely to be thick, is 0.5 to 2 times the thickness of the body center part d, which is most likely to be thin, except for the gate cutting part. The surprising fact that it has been realized becomes clear. In addition, what is excluded from the measurement of the thickness of the gate cutting portion, the bottom center of the stretch blow molding preform,
This is because a gate (protrusion) is always formed, and even if it is cut off, this portion remains in a slightly thick state.

Tables 1 and 2 also show the relationship between the position of the wall of the bottle and the crystallinity and the birefringence of the center of the bottom. Even in the center of the bottom where the most unoriented state is likely to remain. The fact that it is highly oriented so as to have a birefringence of 0.07 or more becomes almost the same as that of the body.
The high degree of molecular orientation in the center of the bottom is due to the fact that the center of the bottom is highly thinned during stretch blow molding. A crystallinity of 0.8 to 1.4 times the crystallinity of the central portion of the body, that is, an oriented crystal can be imparted to the portion.

Further referring to the example described later, it is also clear that the crystallinity of the panel portion 10 of the body portion and the crystallinity of the rib portion 11 of the body portion are substantially the same. Become.

In the present invention, the thickness of the central portion of the bottom is 0.5 to 2 times, especially 0.55 to 1.5 times the thickness of the central portion of the body, excluding the gate cutting portion. When the wall thickness is thinner than the above range, the mechanical strength of the bottom part becomes insufficient.On the other hand, when the wall thickness is thicker than the above range, the orientation of the bottom part becomes insufficient. The result is unsatisfactory. Similarly, from the viewpoint of impact resistance, it is also important that the bottom central portion be molecularly oriented so that the birefringence index in the circumferential direction and the thickness direction is 0.070 or more. It is also important that the central portion of the bottom portion is oriented and crystallized so as to have a crystallinity of 0.8 to 1.4 times, particularly 0.8 to 1.3 times as high as that of the central portion of the body. When it is less than the above range, it is insufficient in terms of heat resistance, especially in self-standing stability after hot filling, while when it is more than the above range, it is insufficient in terms of shape development of the bottom portion. .

When a mold and a stretching rod are used in the stretch blow molding of the polyester preform, the center of the bottom portion supported by the mold and the stretching rod remains unstretched, that is, unoriented, and adjacent to them. The portions to be left also remain in a low orientation state, which is unsatisfactory in terms of impact resistance and heat resistance. Further, if there is a substantial difference in crystallinity between the panel portion and the rib portion of the body, thermal deformation is likely to occur during hot filling. In the present invention, these drawbacks are eliminated without any problem.

According to the present invention, by combining free blow molding, heat treatment and final blow molding, it is possible to achieve a self-supporting one-piece bottom shape while reducing the thickness of the center of the bottom and highly oriented crystallization. Further, while introducing the reduced-pressure absorption structure of the panel-rib, the oriented crystallinity in the thickness direction of the panel portion can be maintained at the same level or large inside. Therefore, it is possible to prevent thermal deformation and asymmetrical deformation when the contents are hot-filled or subsequently cooled, and further, the impact resistance and self-sustaining stability of the bottom and the self-sustaining stable retention during hot-filling are possible. Can be improved. Further, since the strength and heat resistance are improved while reducing the thickness of the bottom of the container, the weight of the container is reduced, which makes it possible to reduce the cost and weight of the container.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to FIG. 4 showing a preform used in the present invention, the preform 20 comprises a neck portion 21, a body portion 22 and a closed bottom portion 23. The neck portion 21 has a lid fastening mechanism such as a screw. 24 and a support ring 25 for holding the container are provided.

The thermoplastic polyester used in the present invention is preferably composed mainly of an ethylene terephthalate type thermoplastic polyester, and most of the ester repeating units, generally 70 mol% or more, particularly 80 mol% or more, are ethylene terephthalate units. Glass transition point (T
g) 50 to 90 ° C., especially 55 to 80 ° C., and melting point (Tm) 200 to 275 ° C., especially 220 to 270.
Thermoplastic polyesters at ° C are preferred.

Although homopolyethylene terephthalate is preferable in terms of heat resistance, a copolymerized polyester containing a small amount of ester units other than ethylene terephthalate units and a polyester blend containing polyethylene terephthalate as a main component can also be used.

Dibasic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; succinic acid, adipic acid, sebacic acid and dodecane. Aliphatic dicarboxylic acids such as dionic acid; and combinations of two or more thereof. As the diol component other than ethylene glycol, propylene glycol,
1,4-butanediol, diethylene glycol, 1,
One or more of 6-hexylene glycol, cyclohexanedimethanol, and an ethylene oxide adduct of bisphenol A can be used.

The ethylene terephthalate type thermoplastic polyester used should have at least a molecular weight sufficient to form a film, and an injection grade or an extrusion grade is used depending on the application. Its intrinsic viscosity (IV) is generally 0.6 to 1.4 dl / g,
In particular, those in the range of 0.63 to 1.3 dl / g are desirable.

Injection molding can be used for molding the polyester into a preform. That is, plastic is melt-injected into a cooled injection mold to form a supercooled amorphous plastic preform.

An injection machine known per se equipped with an injection plunger or a screw is used, and the polyester is injected into an injection mold through a nozzle, a sprue and a gate. As a result, polyester or the like flows into the injection mold cavity and is solidified to form a stretch blow molding preform.

As the injection mold, one having a cavity corresponding to the shape of the container is used, but it is preferable to use a one-gate type or a multi-gate type injection mold. Injection temperature is 270 ~ 310 ℃, pressure is 28 ~ 110kg / c
About m ² is preferable.

According to the present invention, the polyester preform is stretch blow molded (free blow molded) at a stretching temperature under conditions where at least the outer periphery and the bottom are not constrained, so that the neck, the body and the bottom are formed. Mold into the provided secondary molded product.

For stretch blow molding from a preform,
The heat applied to the preform molded article to be molded, that is, residual heat, can be used to perform stretch blow molding following preform molding, but generally, a preform molded article once in a supercooled state is used. A method of producing and heating the preform to the above-mentioned stretching temperature to perform stretch blow molding is preferable.

The stretching temperature of the preform is generally 85 to 135 ° C., particularly 90 to 130 ° C., and the heating is carried out by means known per se such as infrared heating, hot air heating furnace, dielectric heating and the like. be able to. Also,
In order to improve the heat resistance and rigidity of the bottle mouth portion, it is preferable to preliminarily thermally crystallize the preform mouth portion. This thermal crystallization of the mouth can be carried out by heating the mouth of the preform to a temperature of generally 140 to 220 ° C., particularly 160 to 210 ° C. while being thermally insulated from other portions. The crystallinity of the preform mouth is preferably 25% or more.

In the present invention, by free blow molding, 2
The next molded article is manufactured. The preform at the stretching temperature is stretched and stretched in the axial direction with a stretching rod without using a blow molding die, and is expanded and stretched in the circumferential direction by blowing a fluid. As for the draw ratio, the axial draw ratio is 2 to 3.6 times, particularly 2.2 to 3 times, and the circumferential draw ratio is 3 to 6.6 times, and particularly 3.5 to 6 times. The axial stretch ratio is determined by the axial length of the preform molded product and the stroke length of the stretch rod,
The draw ratio in the circumferential direction is determined by the blowing pressure of the fluid.

The free blow molding has an advantage over the conventional die molding in that the bottom and the body can be formed into a secondary molded product having a relatively uniform wall thickness, and the bottom is as thin as the body. It was made possible by free blow.

In general, in mold molding at room temperature, the temperature of the secondary molded product drops to around room temperature. On the other hand, in the present invention, the secondary molded product obtained by free-blow molding of the preform heated to 85 to 135 ° C. is in a state in which about 20 ° C. is further added due to self-heating due to stretching. Therefore,
The free-blow molding has an advantage that the temperature range raised by the subsequent heating of the secondary molded product can be made relatively small, which contributes to shortening the heating time.

According to the present invention, the secondary molded product is then heated to heat-fix the body and the bottom, and the shrinkage thereof is allowed. A suitable heating temperature is generally 120 to 230 ° C., particularly 130 to 220 ° C., and this heating can be performed by infrared rays or the like. By heating the secondary molded product, the polyester forming the container wall, including the bottom and body, is oriented and crystallized, and the residual stress is relieved, and the volume becomes a slightly contracted tertiary molded product. .
During this heat treatment, the fluid in the secondary molded product may be released, or the fluid having a low degree of pressurization may be trapped in the secondary molded product.

The heating and heating process of the secondary molded product can be started in the middle of free blow molding, and the production efficiency can be further improved as compared with the case of performing infrared heating after the completion of the primary blow molding.

According to the present invention, finally, a molded product (tertiary molded product) in the heat treatment step is blow-molded in a blow molding die, and the round bottom portion is located at the center of the bottom and axially outward from the center of the bottom. Final forming into a self-supporting bottom shape consisting of an extending peripheral ground. In this final blow molding, of course, the cavity of the blow molding die used is larger than the tertiary molded product, and the size and shape of the final molded product, including the self-supporting bottom shape and the panel rib decompression absorbing structure, are matched. Must.

The temperature of the final blow molding has a temperature tolerance as compared with that of the free stretch blow molding, and may be lower or higher than that. Generally, the temperature is 120 to 220 ° C., particularly 130 to 210 ° C. Is appropriate.

In addition, since the elastic modulus of the tertiary molded product increases due to crystallization by heat treatment, it is better to use a fluid pressure higher than that of free stretch blow molding, and in general, 1
It is preferable to use a pressure of 5 to 45 kg / cm ² .

In the final blow molding, the temperature of the mold is
The temperature may be maintained at 50 to 135 ° C. and cooling may be performed immediately after molding, or cooling may be performed by passing cold air or the like through the final molded product.

In the heat-resistant polyester bottle of the present invention, the thickness of the body of the container varies depending on the volume of the bottle and the use, but is generally 200 to 500 mm, and particularly 250.
To 450 mm, while the basis weight is 2
It is preferably in the range of 5 to 38 g / l, particularly 28 to 35 g / l, and it is possible to save the basis weight by 5% or more as compared with the conventional bottle.

The heat-resistant polyester bottle of the present invention is useful for hot filling of liquid contents, and is useful as a container for filling and storing various beverages, liquid seasonings and the like. The hot filling temperature is suitably 50 to 110 ° C.

[0050]

The present invention will be further described in the following examples. The methods for evaluating and measuring the characteristic values of the containers described in Examples and Comparative Examples are as follows.

(A) Wall Thickness The wall thickness of the sample was measured using a micrometer (a ball measuring element having a diameter of 2.38 mm).

(B) Crystallinity n-heptane-carbon tetrachloride density gradient tube (made by Ikeda Rika)
Was prepared and the density of the sample was determined under the condition of 20 ° C.
From this, the crystallinity was calculated according to the following formula. ρ: measured density (g / cm ³ ) ρ _am : amorphous density (1.335 g / cm ³ ) ρ _c : crystal density (1.455 g / cm ³ )

(C) Birefringence A retardation R was measured using a polarizing microscope S type (using a direct-reading Babinet type compensator, manufactured by Nikon Corporation). Birefringence The birefringence was calculated from Δn = R / d (d: thickness). In measuring the retardation, the sample is a microtome (Reichert-Jung
Sliced) was used.

(D) Drop test A bottle was filled with water. The insertion position was 40 mm from the tip of the mouth of the bottle. This filled bottle at room temperature,
It dropped vertically from a height of 1.2 m to the concrete floor surface five times. However, if cracking occurred before the 5th time, vertical drop was performed up to that number of times. Bottles manufactured under the same conditions were tested with n = 3.

(E) Heat resistance test A mark 30 mm in height from the bottom of the bottle was filled with water, and the capacity V ₀ up to the mark was measured. Then, the water was discarded, and water at 85 ° C. was added up to a position 40 mm from the tip of the bottle mouth, a cap was put, the product was laid down for 1 minute, and left upright for 4 minutes. After cooling it with water at room temperature, discard the contents,
The volume V ₁ up to the previously marked position was measured with water.
Using these values, the volume shrinkage ratio V'of the bottom and its periphery
= Was calculated _{(V 0 -V 1) / V} 0 * 100 (%).

Example 1 Polyethylene terephthalate resin (Mitsui PET Resin,
Using J125TKL, intrinsic viscosity 0.78 dl / g, DEG copolymerization rate 1.3% by weight), a bottomed preform having a weight of 49 g was produced by injection molding. Next, the mouth was thermally crystallized and whitened by heat treatment. After heating this preform with an infrared heater, without restraining the outer periphery and bottom,
With only the mouth fixed, a stretched rod and an air blow were blown to obtain a primary blow bottle (free blow bottle). Next, the internal pressure is released, the product is inserted into a cylindrical heater, heat-shrinked, and then stretch blow is performed using a mold having a cavity corresponding to FIGS. 1 and 2 (mold temperature 70 ° C.). Then, a self-supporting one-piece bottle (FIG. 1) having a content of about 1.51 was obtained. The temperature immediately before each blow was measured as a preform temperature and a bottle heating temperature with an infrared radiation thermometer at the position of the center of the height of the preform and the bottle. These temperatures were changed and the bottle surface temperature immediately before the secondary blowing was carried out at 200 ° C. and 165 ° C. to obtain bottles A and B.

With respect to the bottom of these bottles, the positions 5 mm, 15 mm, and 25 mm outward from the center of the bottom are defined as a, a, and u, respectively, and the body of the bottle has a center in the height direction (150 mm from the tip of the mouth). The position) was set to D, and the center of the panel was set to O (FIG. 1), and the thickness and crystallinity of each part were measured. For E, the sample was halved inside and outside. The results are shown in Table 1. About part a,
A microtome was used to slice 10 μm so that the cross section was in the circumferential direction of the bottle versus the thickness direction, and the birefringence Δn in the (circumferential direction-thickness direction) was measured.

The drop test was carried out with n = 3, and when there were no cracks in all three, it was ◯, when there were no cracks in two, Δ2.
Table 2 shows the case where more than two pieces are broken. Also, Table 1
Table 2 also shows the wall thickness ratio and the crystallinity ratio of the bottom and the center of the body calculated from

Comparative Example 1 The preform weight was set to 59 g, the preform heating operation was carried out in the same manner as in Example 1, and then the blow rod was blown with a stretching rod and an air blow to obtain the same result as in FIG. A bottle was made. Mold temperature is 140 ℃ for the body and 7 for the bottom
Bottle C was run at 0 ° C and the bottom of the body was 16
Bottle D was run at 0 ° C. The same measurement as in Example 1 was performed, and the results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, bottle C,
In the heat resistance test, D has a large volume shrinkage ratio V ′ at the bottom and its periphery. The center part of the bottom of C is a low stretched part, orientation crystallization did not occur, and since the bottom of the mold is as low as 70 ° C, heat setting is not performed, so the volume shrinkage ratio by heat resistance test is large. Seem. The bottom of D is C
More stretched, but still fairly thick and low stretched. In addition, a slight whitening was observed. This is a mold 160 ℃
This is probably because spherulites were generated in the low-stretched portion due to thermal crystallization due to the high temperature. Therefore, the drop impact resistance is poor.

Bottles A and B show good drop impact resistance and heat resistance. This is because these bottles have a wall thickness ratio, a crystallinity ratio and a birefringence which are within the scope of the present invention.

Further, the crystallinity of the panel portions of the bottles A and B is higher inside than that of the outside, while the crystallinity degree of the panel portions of the bottles C and D is smaller inside than that of the outside. Showed the value. The heat resistance test of (e) above is 1
As a result of carrying out about 00 bottles,
The number of asymmetric deformation occurrences in B, C, D is 0/100, 0/1
It was 00,18 / 100,7 / 100.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

According to the present invention, by combining free blow molding, heat treatment and final blow molding, the thickness of the central portion of the bottom portion is reduced while forming a self-supporting one-piece bottom shape.
It is possible to perform a high degree of oriented crystallization, and it is possible to maintain the oriented crystallinity of the panel and the rib at the same level while introducing the reduced-pressure absorption structure of the panel-rib. For this reason, it is possible to prevent thermal deformation and asymmetrical deformation when the contents are hot-filled or subsequently cooled, and further the impact resistance and self-sustaining stability of the bottom part and the self-sustaining stable holding property when heated are improved. Can be made. Further, since the strength and heat resistance are improved while reducing the thickness of the bottom of the container, the weight of the container is reduced, which makes it possible to reduce the cost and weight of the container.

[Brief description of drawings]

FIG. 1 is a side sectional view for explaining an example of a structure of a polyester bottle of the present invention.

2 is a bottom view of the bottle of FIG. 1. FIG.

FIG. 3 is a side view showing a preform used in the present invention.

[Explanation of symbols]

 1 Bottle 2 Neck Part 3 Upper Body Part 4 Lower Body Part 5 Bottom Part 6 Screw Part for Cap Fastening 7 Support Ring 8 Concave Rib 9 Step Part 10 Panel Part 11 Rib Part 12 Bottom Center Part 13 Peripheral Ground Part 20 Preform 21 Neck Part 22 Body 23 Closed bottom 24 Lid fastening mechanism such as screws 25 Support ring

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 18, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

In Japanese Unexamined Patent Publication (Kokai) No. 5-42586 , a bottomed primary molded body is stretch blow molded into a secondary molded body having a hemispherical bottom in a mold, and only the bottom of the secondary molded body is heated. It is described that after shrinking, the bottom portion is further biaxially stretch blow molded into a shape capable of obtaining self-supporting property. In this method, it is also described that the thickness of the peripheral portion of the bottom was 0.36 mm, while the thickness of the central portion of the bottom was 1.16 mm.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

In the present specification, the birefringence means the value measured by the method described later, while the crystallinity means the following formula (1). In the formula, ρ: measured density ( g / cm ³ ) ρam: amorphous density (1.335 g / cm ³ ) ρc: crystal density (1.455 g / cm ³ ) Density measurement is an n-heptane-carbon tetrachloride density gradient A tube (Ikeda Rika Co., Ltd.) is prepared and performed at 20 ° C. The value obtained by

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

In the heat-resistant polyester bottle of the present invention, the thickness of the body of the container varies depending on the volume of the bottle and the use, but is generally 200 to 500 μm , and particularly 250.
To 450 μm , while the basis weight is 2
It is preferably in the range of 5 to 38 g / l, particularly 28 to 35 g / l, and it is possible to save the basis weight by 5% or more as compared with the conventional bottle.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0058

[Correction method] Change

[Correction content]

The drop test was carried out with n = 3, and when there were no cracks in all three, it was ◯, when there were no cracks in two, Δ2.
Table 2 shows the case where more than two pieces are broken. Also, Table 1
Table 2 also shows the wall thickness ratio and the crystallinity ratio of the bottom and the center of the body calculated from There may be a distribution in the thickness direction
Therefore, the birefringence Δn at the center of the thickness is measured.
And

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Matsuno Kenji Matsuno 3-85-6 Mutsukawa, Minami-ku, Yokohama-shi Kanagawa No. H-705 Yokohama Park Town H-705 (72) Hideo Kurashima 3-26-16 Iwato, Yokosuka City, Kanagawa Prefecture ( 72) Inventor Hiroo Ikegami 3-5-21 Nishihashimoto, Sagamihara City, Kanagawa Prefecture (72) Inventor Kimio Takeuchi 2297-5 Nogawa, Miyamae-ku, Kawasaki City, Kanagawa Prefecture

Claims (3)

[Claims] 1. A secondary molded article having a neck portion, a smooth body portion and a bottom portion, which is obtained by subjecting a thermoplastic polyester preform to stretch blow molding at a stretching temperature under conditions where at least an outer periphery and a bottom are not constrained. The step of molding into
The secondary molded product is heated to heat-set the body and the bottom, and the shrinkage is allowed, and the molded product in the heat treatment process is blow-molded in a blow molding die so that the bottom is centered on the bottom. Bottom forming a self-supporting bottom shape consisting of a peripheral grounding portion extending axially outward from the center of the bottom and finally forming the body into a panel-rib structure for absorbing reduced pressure. A method for producing a one-piece heat-resistant polyester bottle which is excellent in strength, heat resistance, reduced-pressure absorption, and self-sustaining stability. 2. A heat-resistant polyester bottle which is formed by stretch blow molding of a thermoplastic polyester and has a neck portion, a body portion and a bottom portion, and a panel-rib structure for absorbing reduced pressure is formed in the body portion. The bottom center part and the peripheral grounding part extending axially outward from the bottom center part are formed in a one-piece self-supporting structure, and the bottom center part is the meat of the body center part except the gate cutting part. 0.5 to 2 thick
It is thinned to have double the thickness and molecularly oriented so that the birefringence index in the circumferential direction-thickness direction is 0.070 or more, and the bottom center part is crystallized in the body center part. Has a crystallinity of 0.8 to 1.4 times the degree of crystallinity, and the inner and outer sides of the panel part have substantially the same crystallinity or the inner part has a large crystallinity. One-piece heat-resistant polyester bottle with excellent self-standing stability. 3. The central portion of the bottom excluding the gate cut portion is 35%.
The one-piece heat-resistant polyester bottle according to claim 2, which has the above crystallinity.