JP2000000876A - Production of polyethylene terephthalate resin bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a PET resin bottle which can give excellent heat resistance and high strength to an underneck part as well as a neck part. SOLUTION: A preform 6 having a whitened/crystallized neck part 1, a barrel part 4, and a weakly whitened part 5 which is thinner than the barrel part 4 is heated to an orientation temperature. The preform is blow-molded, and the weakly whitened part 5 and the barrel part 4 are stretched in order to form a primary bottle 8. The primary bottle 8 is heated, the part 5 is softened, and a blow-molding part is shrunk freely. A secondary bottle 9 which is smaller than a final bottle form 7, has a recessed step parts on the inner and outer surfaces of the boundary part between the part 5 and a free shrinkage part, and is heated to the orientation temperature is formed. The secondary bottle 9 is blow-molded. The weakly whitened part 5 is stretched to eliminate the recessed step parts in order to form an underneck part 11. The free shrinkage part is stretched again in order to form a shoulder part, a barrel part 13, and a bottom part. The underneck part 11, the shoulder part 12, and the barrel part 13 are heat-set in order to mold a final bottle 15. The crystallinity of the oriented parts is at least 30%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyethylene terephthalate resin bottle.

[0002]

2. Description of the Related Art In recent years, bottles made of polyethylene terephthalate resin (hereinafter abbreviated as PET resin) are excellent in various physical properties such as heat resistance, mechanical strength, gas barrier properties, light weight and transparency. It is widely used as bottles for beverages, teas, sports drinks, carbonated drinks and the like. Conventionally, the PET resin bottle is, for example, shown in FIG.
(A) As shown in the figure, a bottomed cylindrical PET resin mold having a screw portion 22 and a support ring 23 on the outer peripheral surface of a neck portion 21 and a cylindrical body portion 24 formed below the neck portion 21. It is manufactured from the reform 25. A conventional PET resin bottle is formed by blow molding a preform 25 shown in FIG. 6A to form a neck 21 as shown in FIG. 6B.
A lower neck portion 26 immediately below the neck portion 21, a shoulder portion 27 that is connected to the lower neck portion 26 and bulges outward, a trunk portion 28 that extends below the shoulder portion 27, and a bottom portion 2 that further extends below the trunk portion 28.
9

[0003] The excellent physical properties of the PET resin bottle are obtained by biaxially stretching the PET resin by the blow molding and orienting and crystallizing it. However, since normal blow molding is performed by gripping the neck 21 of the preform 25, the neck 21 shown in FIG. 6B remains undrawn and in an amorphous state even after the bottle is formed. The lower neck portion 26 just below the neck portion 21 is insufficiently stretched and the degree of crystallization remains low.

An amorphous PET resin generally has low heat resistance and low mechanical strength, and has a glass transition temperature (about 70 ° C.).
Above, it becomes soft and easily deformed. For example,
When the juice drink or the like is filled in a PET bottle, hot pack processing by high-temperature filling in which the juice drink is heated to 80 to 90 ° C., for example, 85 ° C. for sterilization, and is further maintained at the temperature for 10 minutes after filling. However, if such a process is performed, the amorphous neck 21 may be softened and deformed by heat. In addition, the lower neck portion 26 having a low crystallinity also shows the same tendency as the neck portion 21 in the amorphous state,
Thermal deformation may occur during the hot pack process or the like.

Therefore, various methods have been proposed to improve the heat resistance and mechanical strength of the amorphous neck portion 21 or the low crystallinity neck lower portion 26 of the PET bottle.

First, Japanese Patent Publication No. 59-33101 describes a method for manufacturing a PET bottle having a whitened and crystallized neck portion and a non-whitened portion at a part below the neck portion. The PET resin is chemically stabilized by heating to whiten and crystallize, thereby imparting heat resistance, thereby preventing thermal deformation and crazing of the neck portion. However, such PET bottles have insufficient heat resistance due to the unwhitened portion below the neck.

Further, Japanese Patent Publication No. 2-36455 discloses that
The part immediately below the neck is formed thinner than the other parts of the body, and the preform that has been heated and whitened and crystallized by heating only the neck is housed in a mold having the final bottle outer surface shape. A method for producing a PET bottle to be biaxially stretch blow-molded is disclosed. According to the manufacturing method described in the publication, only the neck of the preform is whitened and crystallized as described above, and biaxial stretch blow molding is performed, whereby the lower neck and the shoulder located between the trunk and the neck are formed. Is stretched so that the entire area is substantially the same thickness as the torso, whereby the entire area of the lower neck and the shoulder is oriented and crystallized, and excellent heat resistance and crazing resistance are given. I have.

However, in the manufacturing method described in the above-mentioned publication, the stretched portion immediately below the whitening neck is relatively thinner than the neck, has poor mechanical strength, and further has a reduced heat resistance of the stretched shoulder and trunk. It is not enough to correspond to the hot pack process described above. In general, when whitening and crystallizing the neck of the preform, even if other parts are shielded, the part directly under the neck is also heated by the heat transfer accompanying the heating of the neck, and it is difficult to whiten only the neck. Usually, it is inevitable that the lower part is slightly whitened. Then, the preform in which the portion immediately below the neck portion is weakly whitened is accommodated in a mold having the outer surface shape of the final bottle, and biaxially stretch blow-molded in one stage to obtain the weakly whitened portion. Becomes insufficiently stretched and remains with low crystallinity. As a result, sufficient heat resistance and mechanical strength cannot be obtained in the neck lower portion 26 of the bottle formed in the shape as shown in FIG. However, there is an inconvenience that heat deformation may occur.

Therefore, the preform having a whitened and crystallized neck portion is housed in a mold having the outer shape of the final bottle, and is subjected to biaxial stretch blow molding, and then formed into a shape as shown in FIG. In general, a manufacturing method has been put to practical use in which the shoulder portion 27 and the body portion 28 of a heated bottle are kept in contact with the inner surface of a heated mold and subjected to heat setting to improve heat resistance. According to the manufacturing method, it is considered that the heat setting relaxes the stress in the shoulder portion 27 and the body portion 28, increases crystallinity, and imparts heat resistance. However, in the lower neck portion 26 located at the boundary between the shoulder portion 27 and the neck portion 21, the effect of the heat setting is not sufficiently obtained, and the heat resistance is higher than that of the shoulder portion 27 stretched and heat set as described above. The lower part of the neck 26 during hot-packing by hot filling, etc.
May be thermally deformed, causing the neck 21 to be distorted.

[0010] Further, according to the above-described manufacturing method in which heat setting is performed in a heated mold, there is also a problem that a manufacturing time is lengthened and productivity is reduced.

On the other hand, a primary bottle is formed by blow molding a preform in which the heat resistance of the neck is improved by whitening crystallization or the like, and the primary bottle is heated and shrunk in a hot air oven or the like to freely shrink. A production method has been put to practical use in which the secondary bottle is again blow-molded to form a final bottle shape after forming the second bottle and increasing the crystallinity. However, even in the manufacturing method of performing the two-stage blow molding, the lower part of the neck is insufficiently stretched, has low crystallinity, and cannot obtain sufficient heat resistance and mechanical strength.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a polyethylene terephthalate capable of imparting excellent heat resistance and mechanical strength capable of being hot-packed to a neck and a lower part of a neck by solving such inconveniences. An object of the present invention is to provide a method for manufacturing a resin bottle.

[0013]

In order to achieve the object, a production method of the present invention comprises a whitened and crystallized neck,
A bottomed cylindrical body having a cylindrical body formed below the neck, and a polyethylene terephthalate resin mold having a weaker whitening portion thinner than the body between the neck and the body; A step of heating the reform to the stretching temperature, applying the heated preform to the first blow molding, stretching the weak whitening portion and the trunk connected to the weak whitening portion, and moving the trunk outward. Swelling to form a primary bottle larger than the final bottle shape, and heating the primary bottle,
Softening the weak whitening portion and freely shrinking the portion that bulges outward in the process, the shape is smaller than the final bottle shape, and the boundary between the weak whitening portion and the free shrinking portion Forming a secondary bottle having concave steps on the inner and outer surfaces, wherein the degree of crystallinity of the free-shrinked portion is increased, and the whole is heated to the stretching temperature; and While being heated to a final temperature, housed in a heated mold having the outer shape of the final bottle and subjected to the second blow molding to re-stretch the weakly whitened portion and the freely shrunk portion. Then, while forming the lower part of the neck where the concave step on the outer surface side of the boundary has disappeared, and heat setting in a state where the lower part of the neck, the shoulder and the body are in contact with the inner surface of the mold, the final bottle shape is formed. And a step of molding into a.

According to the production method of the present invention, a preform having a weak whitening portion thinner than the body portion between the neck portion which has been whitened and crystallized in advance and the body portion formed below the neck portion. And by heating it to a stretching temperature and subjecting it to the first blow molding, the main body is stretched and swelled outward to form a primary bottle having a shape larger than the final bottle shape. In addition, the thinned weak whitened portion also undergoes stretching. At this time, it is necessary that the primary bottle has a shape larger than the final bottle shape in order to reduce the thick portion as much as possible so that the thickness except for the neck portion of the preform is as small as possible.

Next, when the primary bottle is heated, the weak whitening portion is softened by heating. At the same time, the portion that swells outward in the above-described process is freely contracted by stress relaxation, and the degree of crystallinity is increased by heating. As a result, a secondary bottle having a shape smaller than the final bottle shape and having concave steps on the inner and outer surfaces of the boundary between the weakly whitened portion and the freely contracted portion is formed.

[0016] The secondary bottle can be accommodated in a mold having the outer shape of the final bottle, and the second bottle is placed in the mold.
It is necessary to make the shape smaller than the final bottle shape so that it can be further stretched and oriented by subjecting it to blow molding. Further, the heating of the primary bottle needs to be performed such that a concave step is formed on the inner and outer surfaces of the boundary between the weakly whitened portion and the freely contracted portion in the secondary bottle. The concave step is formed as a result of stress relaxation resulting from the heating of the weakly whitened portion and progress of crystallization of the outwardly bulging portion. When the concave step is not formed,
In some cases, the crystallization has not progressed due to insufficient heating, and the primary bottle has insufficient shrinkage, so that the formed secondary bottle may not be accommodated in the mold having the outer shape of the final bottle. Further, when the concave stepped portion is not formed, sufficient heat resistance may not be obtained in each portion of the final bottle obtained by subjecting the secondary bottle to the second blow molding in the mold. .

The entire secondary bottle is heated to the stretching temperature by the heating, and in this state, the secondary bottle is housed in a mold having the outer shape of the final bottle and subjected to the second blow molding. At this time, since the weak whitening portion is heated and softened as described above, it is stretched again by the second blow molding. At this time, a re-stretched lower part of the neck is formed such that the concave step on the outer surface of the boundary with the free-shrink portion disappears. The free-shrinked portion is re-stretched by the second blow molding to form a shoulder portion extending to the lower portion of the neck and bulging outward, a trunk portion extending below the shoulder portion, and a bottom portion extending further below the shoulder portion. .

Since the neck lower portion is re-stretched as a result of the second blow molding as described above, the neck and the shoulder formed by the re-stretching of the free-shrinked portion together with the mold are used in the mold. Is in contact with the inner surface of the. Therefore, by heating the mold, the lower part of the neck, the shoulder, and the body can be heat-set in a state of being in contact with the inner surface of the mold, and the crystallization of each part further proceeds. be able to.

As a result, according to the manufacturing method of the present invention, excellent heat resistance and mechanical strength are imparted to the lower part of the neck, as well as to the neck part which has been imparted with heat resistance and mechanical strength by whitening and crystallization in advance. The obtained PET bottle can be obtained.

In the first blow molding, the preform heated to the stretching temperature may be stretch blown in a mold, or may be so-called free blow without using a mold. However, the shape of the primary bottle changes depending on the preform shape, heating temperature, its temperature distribution, and fluctuations in various conditions such as blow pressure.If the final bottle shape is a complex shape with many irregularities, It is advantageous to manage the shape to some extent at the stage, and it is preferable to use a mold for the shape management.

The heating of the primary bottle can be performed by radiant heating represented by hot air or infrared rays. As a means for heating a relatively transparent non-crystalline PET resin, infrared rays penetrate into the resin, so that the efficiency is high, and it is more advantageous than a hot air system relying solely on heat conduction from the resin surface.
However, since the amount of heat applied to the surface to be heated greatly changes depending on the angle between the heat source and the surface to be heated, the heating of the body and shoulders of a bottle having a three-dimensional and complicated shape is extremely uneven. It is necessary to take care not to create a part to be heated, and to shield a part that does not require heating.

The heating of the primary bottle does not require pressurizing the inside of the bottle and holding it for a long time unlike the conventional heat treatment for holding the bottle in a heating mold. By reducing the cost, the cost required for the equipment can be reduced and the productivity can be improved.

Further, in the production method of the present invention, in the final bottle obtained as described above, the stretched portion has a crystallinity of 30% or more. When the crystallinity is less than 30%, heat resistance becomes insufficient,
If pressure is applied during the high-temperature treatment, there is a risk of deformation. Also,
The crystallinity is preferably 40% or more in order to obtain sufficient heat resistance.

[0024]

Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. 1 (a) to 1 (d) are explanatory views showing a manufacturing method of the present embodiment, and FIGS. 2 to 5 are enlarged views of main parts of FIGS. 1 (a) to 1 (d), respectively. .

In the manufacturing method of the present embodiment, first, PET
By extrusion molding of the resin, as shown in FIG.
A bottomed cylindrical preform 6 having a screw portion 2 and a support ring 3 on the outer peripheral surface thereof and a cylindrical body portion 4 formed below the neck portion 1 was formed. Preform 6 is shown in FIG.
As shown, a portion 5 thinner than the trunk 4 is provided at the boundary between the neck 1 and the trunk 4.

Next, the preform 6 is heated and the neck 1
The portion from the upper end to the portion directly below the support ring 3 is whitened and crystallized, and the space between the whitened portion 5a and the body portion 4 is made low crystallized, so that the weak whitened portion 5 thinner than the body portion 4 below the neck portion 1 is formed.
b was formed. The heating for whitening and crystallizing the neck portion 1 and forming the weakly whitened portion 5b can be performed by a known method.

Next, the preform 6 was heated from the outer surface thereof to a stretching temperature using an infrared heater, the neck 1 was gripped and mounted on a mold (not shown), and subjected to first blow molding.
As a result, as shown in FIG. 1 (b), the body 4 is mainly stretched and bulged outward, and the primary bottle 8 having a shape larger than the final bottle shape 7 shown in phantom in FIG. 1 (b). Was formed. In the primary bottle 8, as shown in FIG. 3, the body 4 is rapidly extended from the end of the weakly whitened portion 5b, but the thinly formed weakly whitened portion 5b is also slightly stretched. I have.

Next, while holding the neck portion 1 of the primary bottle 8 in an open state and rotating it, it is heated in an oven using an infrared heater to soften the weakly whitened portion 5b and bulge outward. The body 4 was freely contracted by stress relaxation.
As a result of the free shrinkage, a secondary bottle 9 smaller than the final bottle shape 7 was obtained as shown in FIG. In the secondary bottle 9, as shown in FIG.
Recessed steps 10a and 10b are formed on the inner and outer surfaces of the boundary between the b and the body 4 which has been freely contracted. At this time, the portion that has been freely shrunk becomes thicker than when the primary bottle was formed (FIG. 3).

In the secondary bottle 9, the distortion of the orientation of the body 4 which has been freely contracted by the stress relaxation is alleviated, and the degree of crystallinity of the body 4 is increased to 30% or more by the heating, and the tough sheet-like shape is obtained. Had become. Also, the secondary bottle 9
The whole was heated to the stretching temperature by the heating.

Then, while the secondary bottle 9 is maintained at the above-mentioned stretching temperature, the secondary bottle 9 is mounted on a heating mold (not shown) and high-pressure air is blown thereinto to perform second blow molding. went.

By the second blow molding, the weak whitening portion 5b of the secondary bottle 9 heated and softened as described above
Was re-stretched to form a neck lower part 11 shown in FIG. 1 (d). The body 4 of the secondary bottle 9 heated as described above is also stretched again, and the shoulder 12 and the body 1 shown in FIG.
3 and bottom 14 were formed.

The lower neck portion 11, the shoulder portion 12, and the torso portion 13
Is heat-set in contact with the inner surface of the heating mold by the stretching, and the final bottle 1 shown in FIG.
5 was obtained.

In the bottle 15, the weak whitened portion 5b is stretched again, and the neck lower portion 11 is stretched greatly as compared with the stretching ratio of the body portion 13. As shown in FIG. The concave step portion 10b on the outer surface side of the boundary between the weak whitening portion 5b of No. 9 and the shoulder portion 12 (the body portion 4 of the secondary bottle 9) had disappeared.

As a result, the crystallinity of the lower part 11, the shoulder part 12, and the body part 13 of the bottle 15 is increased to 30% or more.
Sufficient heat resistance and strength are imparted together with the whitened and crystallized neck portion 1, and no thermal deformation is caused by hot pack treatment by hot filling.

[Brief description of the drawings]

FIGS. 1A to 1D are explanatory views illustrating a manufacturing method according to an embodiment.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an enlarged view of a main part of FIG. 1 (b).

FIG. 4 is an enlarged view of a main part of FIG. 1 (c).

FIG. 5 is an enlarged view of a main part of FIG. 1 (d).

FIG. 6 is an explanatory view showing a conventional manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... neck part, 4 ... trunk | drum, 5 ... weak whitening part, 6 ... preform, 8 ... primary bottle, 9 ... secondary bottle, 10
a, 10b: concave step, 11: lower neck, 12: shoulder, 13: trunk, 14: bottom, 15: final bottle.

 ────────────────────────────────────────────────── ─── Continued on front page F term (reference) 3E033 AA02 BA18 CA01 CA04 CA07 CA16 CA18 DA03 DB01 DD05 EA04 EA12 FA02 FA03 GA02 4F208 AA24 AG07 AH55 AR06 AR12 LA02 LA03 LA05 LB01 LG03 LG28 LG35 LG39 LH02 LH03 LH12 LH10 LHN LW01 LW07

Claims (2)

[Claims] 1. A bottomed cylindrical body having a whitened and crystallized neck and a cylindrical body formed below the neck, wherein the body is located between the neck and the body. Heating the polyethylene terephthalate resin preform having a thinner weak whitening portion to a stretching temperature, subjecting the heated preform to first blow molding, and connecting the weak whitening portion and the weak whitening portion. Extend the torso,
Forming a primary bottle having a shape larger than the final bottle shape by expanding the body outward, and heating the primary bottle to soften the weakly whitened portion and expand outward in the process. The exposed portion is freely shrunk, has a shape smaller than the final bottle shape, and includes concave steps on the inner and outer surfaces of the boundary between the weakly whitened portion and the freely shrunk portion, and the A step of forming a secondary bottle in which the degree of crystallinity is increased and the whole is heated to the stretching temperature; and in a state where the secondary bottle is heated to the stretching temperature, the final outer shape of the bottle And then subjected to the second blow molding to re-stretch the weakly whitened portion and the freely shrunk portion, so that the concave step on the outer surface side of the boundary disappears. Forming a lower portion, the lower neck, shoulders and torso Polyethylene terephthalate resin bottle manufacturing method characterized by comprising the step of forming a final bottle shape by heat-set in a state in contact with the mold inner surface a. 2. The method for producing a polyethylene terephthalate resin bottle according to claim 1, wherein the crystallinity of the stretched portion is 30% or more.