JP2998559B2 - One-piece heat-resistant polyester bottle and its manufacturing method - Google Patents

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, vacuum absorption and self-stability, and a method for producing the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
The biaxially stretched blow-molded container made of thermoplastic polyester has excellent transparency and surface gloss, and also has the necessary impact resistance, rigidity, and gas barrier properties for bottles. That is, it is used as a bottle.

[0003] In this bottled product, a hot filling technique is known as a packaging technique for improving the preservability of the contents. However, polyester bottles have the disadvantage of poor heat resistance. To improve this, heat-set (heat-set) the biaxially stretched blow container after molding to prevent thermal deformation during hot filling. 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.

[0004] Also, in order to make the bottle self-sustaining,
It is also widely practiced to provide legs protruding outward in the axial direction and radially outward on the round bottom of the bottle, but since the bottom center remains in an unstretched or low-stretched state, the bottle bottom is The structure is weak against drop impact.

Japanese Patent Application Laid-Open No. Hei 5-42586 discloses that 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 the shrinkage, the bottom portion is biaxially stretch-blow-molded into a shape capable of obtaining autonomy. It is also described that in this method, the thickness near the bottom center is 1.16 mm while the thickness near the bottom is 0.36 mm.

[0006]

That is, in a one-piece type self-supporting polyester bottle obtained by a conventional stretch blow molding method, the bottom central portion is left undrawn or low-stretched inevitably, and a hemispherical shape is required for container self-supporting. In the case of a one-piece structure in which a complex uneven structure is formed as compared with the shape, the draw ratio of each part is more complicatedly different, and this tendency becomes more remarkable. For this reason, even if the bottle has no problem in terms of heat resistance, if a drop impact is applied to the bottom, a problem such as cracking of the bottom of the bottle occurs.

In the case of a heat-resistant bottle, the reduced pressure due to the volume reduction after hot filling is absorbed by the panel of the body being deformed by paneling inward. When the phenomenon occurs, the paneling of the body part is deformed asymmetrically because the inward paneling deformation does not function. Known stretch blow
In the heat setting method, the degree of stretch orientation inside and outside the bottle is large and the inside is large, and a high-temperature mold is used. Therefore, the degree of heat fixation (degree of oriented crystallization) is large outside the bottle. There is a problem of getting out.

Accordingly, an object of the present invention is to provide a one-piece heat-resistant polyester bottle which is excellent in a combination of mechanical strength and heat resistance of a bottom portion, absorbability under reduced pressure, and self-standing stability, and is capable of hot filling contents. And its manufacturing method.

[0009]

According to the present invention, there is provided a thermoplastic resin.
Formed by stretch blow molding of conductive polyester, neck, body
Panel with a bottom and a bottom, and a panel
Heat-resistant polyester bottle
The bottom is located at the center of the bottom and is more axially outward than the center of the bottom.
And the surrounding grounding part that extends to form a one-piece self-supporting structure
The bottom center, except the gate cut,
0.5 to 2 times the thickness of the center of the body
Birefringence in the circumferential direction-thickness direction as well as thinning
Is molecularly oriented so as to be 0.070 or more.
The central part is 0.8 to 1.4 times the crystallinity of the central part of the body.
And the inside and outside of the panel part are almost the same.
Characterized in that the inside has a high degree of crystallinity
Excellent in part strength, heat resistance, reduced pressure absorption and self-supporting stability
A one-piece heat resistant polyester bottle is provided.
By the way, it is said that the crystallinity inside the panel is large.
The effect is that the inner heat-setting effect is
Indicates that it is difficult. Therefore, the panel must not go outside
become.

[0010] The central portion of the bottom excluding the gate cutting portion is 35% or less.
It is preferable that the crystallinity be above 37%.

According to the present invention, there is also provided a thermoplastic polyester.
The preform at least at the stretching temperature
Stretching under free-blow conditions with unrestricted circumference and bottom
Blow molding, neck, smooth body and round bottom
Forming a secondary molded product provided with the secondary molded product;
Heat to fix the body and bottom, and allow shrinkage.
In the blow molding mold
Blow molding with the bottom center and bottom center
Self-supporting bottom consisting of a peripheral ground contact extending outward in the direction
And the body part has a panel-rib structure for absorbing reduced pressure.
And a final forming step.
One piece with excellent heat resistance, reduced pressure absorption and self-standing stability
Provided is a method for producing a hot-type heat-resistant polyester bottle.
You.

[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 (free blow) molding is performed under the condition that at least the outer periphery and the bottom are not constrained,
Form into a secondary molding with a neck, a smooth body and a bottom. By this free blow, the bottom portion is also stretched in a completely unconstrained state, so that it is thinned and molecularly oriented in the same manner as the body portion.

Next, the secondary molded article is heated to heat-fix the body and the bottom, and these are shrunk freely.
By this heat treatment, the residual distortion of the vessel wall of the body and the bottom is alleviated, and the oriented crystallization of the vessel wall polyester proceeds. At this time, the body portion is stretch-blown in a smooth state, and the bottom portion is stretch-blown, and furthermore, in this state, it is subjected to heat treatment and relaxation of strain, so that the orientation crystallization of the vessel wall is extremely uniform. It has become.

Finally, the molded product in the heat treatment step is blow-molded in a blow mold, and the round bottom is formed of a bottom central portion and a peripheral ground contact portion extending axially outward from the bottom central portion. The body is finally molded into a self-supporting bottom shape with a reduced pressure absorbing panel-rib structure. Of course, the mold used in this final blow molding step must match the self-supporting bottom shape of the final container and the reduced pressure absorbing structure of the panel-rib.
In this final blow molding step, the container bottom can be provided with autonomy and the container body can be provided with reduced pressure absorption.

In the present invention, the above-mentioned free blow molding,
By the combination of the heat treatment and the final blow molding, the bottom center portion is made to have a thickness of 0.5 to 2 times, particularly 0.55 to 1.5 times the thickness of the body center portion, excluding the gate cut portion. It is molecularly oriented so as to have a birefringence of 0.070 or more in the circumferential direction-thickness direction, and has a crystallinity of 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 orientation crystallization can be performed as described above, and such a thinned bottom portion and oriented crystallization have been achieved.

By forming a bottom center portion and a peripheral ground portion extending outward in the axial direction from the bottom center portion on the oriented crystallized bottom portion, not only self-standing stability is obtained, but also By uniform orientation crystallization, the bottom becomes excellent in impact resistance, and further, the thermal deformation of the free-standing structure of the bottom is prevented, and excellent self-standing stability is maintained even after hot filling.

Further, by forming a reduced pressure absorbing structure composed of a panel portion and a rib in the final blow molding step on the uniformly oriented and crystallized body portion, the crystallinity inside and outside the panel portion can be reduced. Almost the same or the inside is in a larger range, preventing uneven thermal deformation during hot filling,
The panel effectively generates paneling deformation at the time of decompression due to cooling, thereby preventing asymmetric deformation of the container.

In the present specification, the birefringence refers to a value measured by a method described later. On the other hand, the crystallinity refers to the following equation (1): ρc (ρ-ρam) Crystallinity XC = ─── · ─────── × 100 ‥‥ (1) ρ (ρc−ρam) where ρ: measured density ( g / cm ³ ) Ρam: amorphous density (1.335 g / cm ³ ) Ρc: crystal density (1.455 g / cm ³ The density measurement is performed at 20 ° C. by preparing an n-heptane-carbon tetrachloride-based density gradient tube (Ikeda Rika Co., Ltd.). Means 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, this bottle 1 has a neck 2, a frustum or a rotating body at the neck. It comprises a tubular lower body 4 connected via the upper body 3 and a bottom 5 connected to the lower end of the lower body. The neck portion 2 is formed with a screw portion 6 for fastening a cap and a support ring 7. Between the lower body 4 and the upper body 3, a concave bead portion 8 for buffering at the time of heating and cooling.
Is formed between the lower body portion 4 and the bottom portion 5, and a step portion 9 that performs a buffering action at the time of heating and at the time of cooling is formed.

The lower body 4 has a substantially rectangular panel 10.
And a rib portion 11 as a frame for the panel portion are arranged in a circumferential direction to form a reduced pressure absorbing mechanism. That is, the panel portion 10 is subjected to paneling deformation in which the panel portion 10 retreats inward, so that reduced pressure absorption can be performed.

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

FIG. 1 and FIG. 2 also show sample positions of the thickness of the bottle container wall, which are substantially at the center at the bottom center, at the periphery at the center at the bottom, and at the middle of these, and at the trunk. There is an intermediate portion d, and these positions are sample positions in an 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 portion a, which tends to be the thickest, is 0.5 to 2 times the thickness of the body center portion d, which is the thinnest, except for the gate cut portion. The surprising fact that it has been clarified becomes clear. In addition, the gate cut part is excluded from the measurement of the thickness, the center of the bottom of the stretch blow molding preform,
This is because a gate (projection) is always formed, and this portion remains in a somewhat thick state even if it is cut off.

Tables 1 and 2 also show the relationship between the wall position of the bottle and the crystallinity and the birefringence in the center of the bottom. The fact that it is highly oriented so as to have a birefringence of 0.07 or more almost in the same manner as the body becomes clear.
The high molecular orientation at the center of the bottom is due to the fact that the central part of the bottom is highly thinned during stretch blow molding. The part can be provided with a crystallinity of 0.8 to 1.4 times the crystallinity of the central part of the body, that is, an oriented crystal.

Referring to the examples described later, it is also clear that the crystallinity of the body panel 10 and the crystallinity of the rib 11 of the body are substantially the same. Become.

In the present invention, the center of the bottom is thinned so as to have a thickness of 0.5 to 2 times, particularly 0.55 to 1.5 times the thickness of the center of the body except for the gate cutting portion. It is especially important that when the thickness is smaller than the above range, the mechanical strength of the bottom becomes insufficient, while when the thickness is larger than the above range, the degree of orientation of the bottom becomes insufficient, so that the impact resistance is reduced. Unsatisfactory results. Similarly, from the viewpoint of impact resistance, it is important that the bottom central portion is molecularly oriented so that the birefringence in the circumferential direction-thickness direction is 0.070 or more. It is also important that the center of the bottom is oriented and crystallized to have a crystallinity of 0.8 to 1.4 times, particularly 0.8 to 1.3 times the crystallinity of the center of the body. When less than the above range, the heat resistance is insufficient, particularly in terms of self-sustainability after hot filling, and when larger than the above range, the shape development of the bottom is insufficient. .

When a mold and a stretching rod are used in stretch blow molding of a polyester preform, the bottom center portion supported by the mold and the stretching rod remains unstretched, that is, in an unoriented state, and is adjacent to these. The remaining portion also remains in a low orientation state, which is unsatisfactory in terms of impact resistance and heat resistance. 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. These disadvantages have been solved without problems in the present invention.

According to the present invention, by combining free blow molding, heat treatment and final blow molding, it is possible to reduce the thickness of the central portion of the bottom and to achieve highly oriented crystallization while forming a self-supporting one-piece bottom shape. In addition, while introducing the reduced pressure absorbing structure of the panel-rib, it is possible to maintain the orientation crystallinity in the thickness direction of the panel portion at the same level or large inside. For this reason, it is possible to prevent thermal deformation and asymmetric deformation when the contents are hot-filled or subsequently cooled, and furthermore, impact resistance and self-standing stability at the bottom and self-standing stability during hot filling. Can be improved. In addition, since the strength and heat resistance are improved while reducing the thickness of the bottom of the container, the weight per unit area of the container is reduced, thereby reducing the cost and weight of the container.

[0028]

FIG. 4 shows a preform used in the present invention. The preform 20 comprises a neck 21, a body 22 and a closed bottom 23, and the neck 21 has a lid fastening mechanism such as a screw. 24 and a support ring 25 for holding the container.

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

Although homopolyethylene terephthalate is preferred in terms of heat resistance, copolymerized polyesters containing a small amount of ester units other than ethylene terephthalate units and polyester blends mainly composed of polyethylene terephthalate can also be used.

Examples of 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, dodecane One or a combination of two or more aliphatic dicarboxylic acids such as diacids, and diol components other than ethylene glycol include propylene glycol,
1,4-butanediol, diethylene glycol, 1,
One or more of 6-hexylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A and the like can be mentioned.

The ethylene terephthalate-based thermoplastic polyester to be 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 to mold the polyester into a preform. That is, the plastic is melt-injected into a cooled injection mold to form a supercooled amorphous plastic preform.

As the injection machine, a known injection machine 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, the polyester or the like flows into the injection mold cavity and is solidified to form a preform for stretch blow molding.

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

According to the present invention, the polyester preform is subjected to stretch blow molding (free blow molding) at a stretching temperature under the condition that at least the outer periphery and the bottom are not constrained, and the neck, body and bottom are formed. It is molded into a secondary molded article provided.

For stretch blow molding from a preform,
A method of performing stretch blow molding following preform molding using heat given to the preform molded article to be molded, that is, residual heat, can be used, but generally, a preform molded article in a once supercooled state is used. It is preferable that the preform is manufactured, and the preform is heated to the above-described stretching temperature to perform stretch blow molding.

The stretching temperature of the preform is generally from 85 to 135 ° C., preferably from 90 to 130 ° C., and the heating is performed by means known per se such as infrared heating, hot air heating furnace, and dielectric heating. be able to. Also,
In order to increase the heat resistance and rigidity of the bottle mouth, it is preferred that the mouth of the preform be thermally crystallized in advance. The thermal crystallization at the mouth can be performed 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 at the mouth of the preform is preferably at least 25%.

According to the present invention, free blow molding is used to
Next, a molded article is manufactured. The preform at the stretching temperature is stretched and stretched in the axial direction by a stretching rod without using a blow molding die, and expanded and stretched in the circumferential direction by blowing fluid. The stretching ratio is preferably such that the axial stretching ratio is 2 to 3.6 times, especially 2.2 to 3 times, and the circumferential stretching ratio is 3 to 6.6 times, especially 3.5 to 6 times. The axial stretching ratio is determined by the axial length of the preform molded article and the stroke length of the stretching rod,
The stretching ratio in the circumferential direction is determined by the blowing pressure of the fluid.

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

In general, in mold molding at room temperature, the temperature of the secondary molded product decreases to near room temperature. On the other hand, in the present invention, a secondary molded product obtained by free blow molding a preform heated to 85 to 135 ° C. is in a state where about 20 ° C. is added due to self-heating caused by stretching. Therefore,
In the free blow molding, the temperature range to be increased by the subsequent heating of the secondary molded product can be made relatively small, and there is an advantage that the heating can be shortened.

According to the present invention, the secondary molded article is then heated to heat-fix the body and the bottom, while allowing its shrinkage. The heating temperature is generally in the range of 120 to 230 ° C., particularly 130 to 220 ° C., and the heating can be performed by infrared rays or the like. By heating the secondary molded product, the polyester constituting the container wall is oriented and crystallized, including the bottom and the body, and the remaining stress is also relaxed, so that a tertiary molded product with a slightly reduced volume is obtained. .
During this heat treatment, the fluid in the secondary molded product may be released, or a fluid with a low degree of pressurization may be trapped in the secondary molded product.

The step of heating and heating the secondary molded article can be started in the middle of free blow molding, so that the production efficiency can be increased as compared with the case where infrared heating is performed after the end of primary blow molding.

According to the present invention, finally, the molded article (tertiary molded article) in the heat treatment step is blow-molded in a blow mold so that the round bottom is located at the bottom center and axially outward from the bottom center. Final shaping into a self-supporting bottom shape consisting of an extended peripheral ground. In this final blow molding, naturally, the cavity of the blow molding die used is larger than that of the tertiary molded product and conforms to the dimensions and shape of the final molded product, including the self-supporting bottom shape and the panel rib decompression absorption structure. Must.

The temperature of the final blow molding is more tolerant to the temperature of free stretch blow molding and may be lower or higher, and is generally between 120 and 220 ° C., especially between 130 and 210 ° C. Is appropriate.

In the tertiary molded product, since the elastic modulus is increased by crystallization by heat treatment, it is preferable to use a fluid pressure higher than that in the free stretch blow molding.
Preferably, a pressure of 5 to 45 kg / cm ² is used.

In the final blow molding, the temperature of the mold is
Cooling may be performed immediately after molding while maintaining the temperature at 50 to 135 ° C., or cooling may be performed by flowing cold air or the like into the final molded product.

In the heat-resistant polyester bottle of the present invention, the thickness of the container body is generally 200 to 500 μm , especially 250
To 450 μm , while the basis weight is 2
It is preferably in the range of 5 to 38 g / l, particularly in the range of 28 to 35 g / l, and the weight per unit area can be reduced by 5% or more as compared with a 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. An appropriate hot filling temperature is 50 to 110 ° C.

[0050]

The present invention is further described by the following examples. The methods for evaluating and measuring the container characteristic values described in the examples and comparative examples are as follows.

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

(B) Crystallinity n-heptane-carbon tetrachloride density gradient tube (manufactured by Ikeda Rika)
Was prepared, and the density of the sample was determined at 20 ° C.
From this, the crystallinity was calculated according to the following equation. 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 was a microtome (Reichert-Jung
Was sliced.

(D) Drop test The bottle was filled with water. The insertion position was 40 mm from the tip of the mouth of the bottle. At room temperature,
It dropped vertically five times from a height of 1.2 m onto the concrete floor. However, if a crack occurred before the fifth time, it was regarded as a vertical drop up to that number. Performed with n = 3 using bottles prepared under the same conditions.

(E) Heat resistance test A mark was placed at a height of 30 mm from the bottom of the bottle, water was poured into the mark, and the volume V ₀ up to the mark was measured. Next, the water was discarded, and water at 85 ° C. was put to a position 40 mm from the tip of the mouth of the bottle, capped, turned over, and left standing for 1 minute and upright for 4 minutes. After cooling this with room temperature water, the contents are discarded,
The volume V ₁ up to the previously marked position was measured with water.
Using these values, the volume shrinkage V ′ at the bottom and its surroundings
= Was calculated _{(V 0 -V 1) / V} 0 * 100 (%).

Example 1 Polyethylene terephthalate resin (manufactured by Mitsui Pet Resin,
Using J125TKL, intrinsic viscosity 0.78 dl / g, and DEG copolymerization ratio of 1.3% by weight), a bottomed preform weighing 49 g was produced by injection molding. Next, the mouth portion was thermally crystallized and whitened by heat treatment. After heating this preform with an infrared heater, do not restrain the outer periphery and bottom,
With only the mouth fixed, a primary blow bottle was obtained by blowing a stretch rod and air blow (free blow bottle). Next, the internal pressure was released, and the sample was inserted into a cylindrical heater and shrunk by heating. Then, stretch blow was performed using a mold having a cavity corresponding to FIGS. 1 and 2 (mold temperature: 70 ° C.). Thus, a self-supporting one-piece bottle having an internal capacity of about 1.51 (FIG. 1) was obtained. In addition, the temperature immediately before each blow was measured as the preform temperature and the bottle heating temperature with an infrared radiation thermometer at the center of the height of the preform and the bottle. The bottles A and B were obtained by changing the temperature and changing the bottle surface temperature immediately before the secondary blow to 200 ° C. and 165 ° C.

In the bottom of these bottles, positions of 5 mm, 15 mm and 25 mm outward from the center of the bottom are designated as a, a and c, respectively, and the center of the bottle body in the height direction (150 mm from the tip of the mouth). ) And the center of the panel was set to E (FIG. 1), and the thickness and crystallinity of each part were measured. In the case of E, the sample was folded inward and outward and measured. Table 1 shows the results. About part A,
Using a microtome, the slice was sliced to 10 μm so that the cross section was in the circumferential direction to the thickness direction of the bottle, and the birefringence Δn of (circumferential direction−thickness direction) was measured.

The drop test was carried out with n = 3. When no cracks were found in all three pieces, ○ was given, and when no cracks were found in two pieces, Δ was given.
Table 2 shows the case where the number of pieces is broken by more than X. Table 1
Table 2 also shows the thickness ratio and crystallinity ratio between the bottom and the center of the body calculated from the above.

COMPARATIVE EXAMPLE 1 The preform weight was set to 59 g, the operation up to the preform heating operation was performed in the same manner as in Example 1, and then the same process as in FIG. A bottle was made. The mold temperature was 140 ° C for the body and 7 for the bottom.
Bottle C was run at 0 ° C.
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
D has a large volume shrinkage V ′ at the bottom and its periphery in the heat resistance test. The central part of the bottom of C is a low-stretched part, orientation crystallization has not occurred, and since the bottom of the mold has a low temperature of 70 ° C., it is not heat-set, so that the volume shrinkage by the heat test is large. Seem. The bottom of D is C
Although it is more stretched, it is still quite thick and low stretch. Also, slight whitening was observed. This is 160 ° C mold
This is probably because spherulites were generated by thermal crystallization in the low-stretched portion due to the high temperature. Therefore, the drop impact resistance is poor.

The bottles A and B show good drop impact resistance and heat resistance. This is because these bottles have wall thickness ratios, crystallinity ratios and birefringences that fall within the scope of the present invention.

The crystallinity of the panel portions of the bottles A and B is larger on the inside than on the outside, while the crystallinity of the panel portions of the bottles C and D is smaller on the inside than on the outside. The value was shown. The heat resistance test of (e) was performed by
The results for 00 bottles show that bottles A,
The number of asymmetric deformation occurrences in B, C and D is 0/100, 0/1
00, 18/100 and 7/100.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

According to the present invention, it is possible to reduce the thickness of the central portion of the bottom while forming a self-supporting one-piece bottom shape by a combination of free blow molding, heat treatment and final blow molding.
A high degree of oriented crystallization can be achieved, and the oriented crystallinity of the panel and the rib can be maintained at the same level while introducing a reduced pressure absorption structure of the panel-rib. For this reason, it is possible to prevent thermal deformation and asymmetric deformation when the contents are hot-filled or subsequently cooled, and further improve the impact resistance and self-standing stability at the bottom and the self-standing stability when hot. Can be done. In addition, since the strength and heat resistance are improved while reducing the thickness of the bottom of the container, the weight per unit area of the container is reduced, thereby reducing the cost and weight of the container.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bottle 2 Neck 3 Upper torso 4 Lower torso 5 Bottom 6 Screw part for fastening a cap 7 Support ring 8 Concave rib 9 Stepped part 10 Panel part 11 Rib part 12 Bottom center part 13 Peripheral grounding part 20 Preform 21 Neck part 22 Body 23 Blocking bottom 24 Screw fastening mechanism such as screw 25 Support ring

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Matsuno 3-85-6, Muttsugawa, Minami-ku, Yokohama, Kanagawa Prefecture Yokohama Park Town H-705 (72) Inventor 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, Miyama-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-5-42586 (JP, A) JP-A-62-30019 (JP, A) JP-A-60-171124 (JP, A) JP-A-62-238730 (JP, A) JP-A-63-191737 (JP, A) JP-A-64 -85733 (JP, A) JP-A-54-88481 (JP, A) JP-A-57-24219 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65D 1/00- 1/46 B29C 49/00-49/08

Claims (3)

(57) [Claims] 1. A heat-resistant polyester bottle formed by stretch blow molding of a thermoplastic polyester and having a neck, a body, and a bottom, and a body having a panel-rib structure for absorbing reduced pressure. The bottom center part and the peripheral grounding part extending outward in the axial direction from the bottom center part are formed in a one-piece self-supporting structure, and the bottom center part is the meat at the center part of the trunk except for the gate cutting part. 0.5 to 2 thick
In addition to being thinned so as to have a double thickness, it is molecularly oriented so that the birefringence in the circumferential direction-thickness direction is 0.070 or more, and the bottom central part is crystallized in the body central part And a bottom portion having a degree of crystallinity of 0.8 to 1.4 times the degree of crystallinity, and the inside and outside of the panel portion having substantially the same or a large degree of crystallinity inside the panel portion. One-piece heat-resistant polyester bottle with excellent self-standing stability. 2. The bottom central portion excluding the gate cutting portion is 35%.
The one-piece heat-resistant polyester bottle according to claim 1, which has the above crystallinity. 3. A stretch blow molding of a thermoplastic polyester preform at a stretching temperature under free blow conditions in which at least the outer periphery and the bottom are not restricted,
A step of forming a neck, a smooth body, and a secondary molded article having a round bottom, a step of heating the secondary molded article, thermally fixing the body and the bottom, and allowing the shrinkage thereof; Blow molding the molded product in the heat treatment step in a blow mold, and forming the bottom into a self-supporting bottom shape including a bottom center and a peripheral grounding portion extending axially outward from the bottom center. And a step of finally forming a part into a panel-rib structure for absorbing reduced pressure, a method for producing a one-piece heat resistant polyester bottle excellent in bottom strength, heat resistance, reduced pressure absorption and self-supporting stability.