JPH07308957A - Polyester bottle and production thereof - Google Patents

Abstract

PURPOSE:To stably produce a polyester bottle not having a flaw such as appearance deficiency or hermetical seal deficiency in its bottle mouth part with high productivity without frequently cleaning a preform injection mold while reducing the closing tendency of the air vent part of the injection mold. CONSTITUTION:In the injection molding and stretching blow molding of a thermoplastic polyester resin, as the thermoplastic polyester resin, ethylene terephathalate type polyester with intrinsic viscosity of 0.6-1.4dl/g and cycle (ethylene/ethylene oxyethylene.diterephthalate) content of 80ppm or less is used and the content of cyclo (ethylene/ethylene oxyethylene.diterephtalate) in a bottle is set to 100ppm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester bottle and a method for producing the same, and more particularly, to a polyester bottle having no mouth defect and a method for stably producing the bottle with high productivity.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Biaxially stretch 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 can be bottled with various liquids. It is used as a container.

Polyester bottles are generally manufactured by injection-molding a thermoplastic polyester resin into a preform and stretch-blowing the preform obtained at a stretching temperature.

Further, the polyester container has a drawback that it is inferior in heat resistance. For the purpose of hot filling the contents, heat deformation or shrinkage deformation of volume occurs, so that the biaxially stretched blow container is heated after molding. It is also fixed (heat set).

For the ethylene terephthalate polyester for forming bottles, a manufacturing method of reacting terephthalic acid with ethylene glycol to form a polymer is adopted. According to this method, except for the polyester mainly containing ethylene terephthalate units. In addition, a low molecular weight substance is generated during the polymerization, and this is attached to the surface of the container during heat setting, which causes roughening or clouding of the surface of the container.

Japanese Patent Laid-Open No. 2-30512 discloses a heat treatment mainly composed of ethylene terephthalate units in order to prevent the deterioration of the commercial value of the container due to the roughening of the surface of the container and the fogging caused by heat fixing with a low molecular weight substance. A container comprising a neck portion, a shoulder portion, a body portion, and a closed bottom portion obtained by stretch blow-molding a plastic polyester preform and heat-setting the orientation, wherein the container has an intrinsic viscosity of 0.70.
To 0.85 dl / g and the content of cyclic trimer is 0.55
It is formed of polyester in an amount of not more than 10% by weight, and the planar portion of the body is molecularly oriented so that the refractive index in the thickness direction is 1.52 or less, and has a crystallinity of 30 by the density method.
% Crystallized and a glossiness of 90% or more (g
A container characterized by having a loss) is described.

[0007]

The heat-set biaxially stretched polyester bottles found in the above proposals are characterized in that the surface of the container is not roughened and the surface smoothness is excellent. However, polyethylene terephthalate is injected and stretched. When manufacturing bottles by the blow molding method, with the operation for a long time,
There is a tendency that a bottle that cannot be used practically is produced due to poor appearance, poor sealing performance, and the like at the mouth of the bottle.

As a result of exploring this cause, the present inventors have found that during injection molding of a preform, dirt begins to accumulate on the air vent portion during continuous operation for a long time and gradually becomes clogged, resulting in poor air escape. I knew there was a cause. Incidentally, the air vent means a passage provided for discharging air and generated gas in the cavity during the process of filling the molding material mold in injection molding. The air vent is provided on the side that becomes the mouth of the preform.

As a result, on the outside of the tip of the mouth portion leading to the air vent portion of the preform, defective filling occurs in which the edge does not follow the mold and is rounded. And sometimes bubbles even come in.

Even when the above-mentioned appearance problem is not particularly observed at the stage obtained by injection molding, a heat treatment for whitening and crystallizing the mouth portion after that, like a heat-resistant bottle, is performed. If necessary, this heat treatment may cause depressions at the tip of the mouth. This is because the peripheral material does not have an indentation in appearance due to defective air removal at the air vent portion, but residual strain is caused, and the resin moves in a direction to alleviate it during heat treatment.

The present inventors have found that the dirt accumulated and accumulated in the air vent portion is closely related to a specific oligomer component contained in polyethylene terephthalate, that is, cyclo (ethylene / ethyleneoxyethylene diterephthalate). It was

Accordingly, it is an object of the present invention to provide a polyester bottle having no defects such as poor appearance and poor sealing at the bottle mouth and a method for producing the same. Another object of the present invention is that the air vent portion of the preform injection mold is less likely to be clogged, and the injection mold need not be frequently cleaned.
It is an object of the present invention to provide a method for producing a polyester bottle capable of stably producing a bottle having a mouth portion having dimensional accuracy and appearance as designed and with high productivity.

[0013]

According to the present invention, a thermoplastic polyester resin is injection molded into a preform, and the resulting preform is stretch blow molded at a stretching temperature. Intrinsic viscosity of 0.6 as a plastic polyester resin
To 1.4 dl / g, the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate) is 80 ppm or less, ethylene terephthalate polyester is used, and the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate) in the bottle is 100 ppm. The following provides a method for producing a polyester bottle, which is suppressed.

In the present invention, in order to prevent defects at the mouth of the bottle, it is effective to carry out the injection while maintaining the resin temperature at 310 ° C. or lower, and in the method of the present invention, the preform or bottle Thermally crystallize the mouth by heating,
It is particularly effective in increasing the heat resistance and rigidity of the mouth.

Also according to the present invention, the bottle is made of ethylene terephthalate polyester having an intrinsic viscosity of 0.6 to 1.4 dl / g and the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate) in the bottle is 100.
Provided is a polyester bottle having an excellent mouth-sealing property, which is characterized by being ppm or less.

According to the present invention, further, in a heat-resistant polyester bottle having a mouth whitened by thermal crystallization,
Made from ethylene terephthalate polyester with an intrinsic viscosity of 0.6 to 1.4 dl / g, the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate) in the bottle is 100 ppm or less, and the amount of depression at the tip of the mouth Of 0.50 mm or less is provided.

[0017]

In the bottle-forming polyethylene terephthalate, various oligomers are contained in addition to the high molecular weight ethylene terephthalate. The present inventors have found that, during injection molding of a polyethylene terephthalate preform, the clogging of the air vent of the injection mold is caused mainly by cyclo (ethylene / ethyleneoxyethylene diterephthalate) of these oligomers. I found out that.

The above cyclo (ethylene / ethyleneoxyethylene diterephthalate) is represented by the following formula (1)

[0019]

[Chemical 1]

In the above formula, Φ is a paraphenylene group,
As shown in, a cyclic isomerized dimer (hereinafter referred to as C2 ′) in which one ethylene glycol component of the cyclic dimer of terephthalic acid and ethylene glycol is replaced by a diethylene glycol component.

The above-mentioned cyclic isomerized dimer (C2 ') is completely different from the cyclic trimer, ie, ethylene terephthalate / cyclic trimer, which has been a problem in the prior art, both in the physical properties and in the behavior during bottle molding. It is different. The melting point of ethylene terephthalate / cyclic trimer is about 3
It has a high melting point of 14 to 327 ° C, while the above C
2 ′ has a low melting point of 165 to 167 ° C., and the melting point of ethylene terephthalate / cyclic dimer, whose existence has been recently confirmed, is lower than that of 229 ° C. Furthermore, in the case of ethylene terephthalate / cyclic trimer, migration (plate-out) becomes a problem during crystallization of polyethylene terephthalate (at the time of heat setting), whereas in cyclo (ethylene / ethyleneoxyethylene diterephthalate), injection molding Transition over time is a problem and the behavior is quite different. The transfer of cyclo (ethylene / ethyleneoxyethylene diterephthalate) to the injection mold is low under this molding condition because of its low melting point, therefore low viscosity, high resin temperature and high shear rate. It is related to the tendency to migrate to the melting point component boundary surface, and this seems to be the reason for accumulation in the air vent portion.

In the present invention, cyclo (ethylene / ethyleneoxyethylene diterephthalate) (C
By setting the content of 2 ′) to 100 ppm or less, particularly 90 ppm or less, the tendency of the air vent of the preform injection mold to be blocked is significantly reduced, and there is no defect such as poor appearance or poor sealing at the bottle mouth. A polyester bottle can be stably manufactured with high productivity.

That is, as shown in the comparative example described later, when the content of C2 'in the bottle exceeds 100 ppm,
When injection molding exceeds 20,000 shots, the outer edge of the mouth portion is not formed as intended, and when it exceeds 30,000 shots, air bubbles are trapped in the mouth portion.

The influence of the content of C2 'in the bottle is more remarkable in the bottle thermally crystallized so as to whiten the mouth. When the number of shots exceeds 5,000, it becomes 0.
Dimples as large as 5 mm are generated.

On the other hand, according to the present invention, if the content of C2 'in the bottle is suppressed to 100 ppm or less, the molding accuracy of the mouth and the entrapment of air bubbles are still reduced even when 40,000 shots are taken in the injection molding. It is possible to form a mouth portion that is excellent in sealing performance and appearance without causing the occurrence of. Also,
Even if the mouth is thermally crystallized so as to be whitened, no dent is formed in the mouth and the sealing performance and the appearance are excellent.

The content of the C2 'component contained in the bottle is influenced by the resin composition before molding and the injection molding conditions. In order to suppress the C2 'content of the bottle after molding to 100 ppm or less, first, the C in the raw material pellets is
It is necessary to suppress the 2'content to 80 ppm or less, particularly 70 ppm or less. Next, the injection condition is C in the bottle.
It is necessary to set the 2'content so as not to exceed 100 ppm. This is because the highest temperature in the bottle manufacturing process is the injection molding process, and the above-mentioned generation of C2 ′ proceeds due to heating during molding of the preform.

In the present invention, the intrinsic viscosity is 0.6 to 1.4 dl / g, particularly 0.65 to 1.3 dl / g, and the C2 ′ content is 80 ppm or less, especially 70 ppm, although it has a high molecular weight. It is necessary to use the following ethylene terephthalate polyester (PET) for injection molding and biaxially stretch blow molding, and then it is necessary to suppress the C2 'content in the bottle to 100 ppm or less and perform injection molding. Therefore, for this reason, it is preferable to perform injection molding of polyester under the condition that the resin temperature is 310 ° C. or lower, particularly 300 ° C. or lower. Even if the C2 'content of the raw material polyester is 80 ppm or less, the cyclic isomerization dimer C of the bottle
It should be noted that under the condition that the content of 2'exceeds 100 ppm, the tendency of the injection mold to move to the air vent portion is large (see Comparative Example 2).

According to the present invention, by using ethylene terephthalate type polyester, injection molding and stretch blow molding are carried out so that the C2 'content in the bottle is maintained at 100 ppm or less. Manufactures polyester bottles without defects such as defects and poor sealing, reducing the tendency of air vents of preform injection molds to become blocked and maintaining stable and high productivity without the need for frequent cleaning of injection molds. can do.

[0029]

Preferred Embodiment of the Invention

[Polyester] In the present invention, the intrinsic viscosity is 0.6 to 1.4 dl / g, particularly 0.65 to 1.3 dl / g, and the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate), that is, C2 ′ is 80 ppm or less, particularly 70 ppm or less of ethylene terephthalate polyester is selected and used.

The intrinsic viscosity of the ethylene terephthalate polyester used for molding the bottle is higher than that of a normal film in view of mechanical strength, impact resistance, pressure resistance and heat resistance (creep resistance) of the bottle. High ones are required.
Therefore, it is necessary to use an ethylene terephthalate-based polyester having an intrinsic viscosity of 0.6 dl / g or more.
On the other hand, in terms of moldability of the polyester resin, particularly injection moldability and shape reproducibility in stretch blow molding, it is necessary that its intrinsic viscosity be in the range of 1.4 dl / g.

The methods for producing ethylene terephthalate type polyesters are roughly classified into two methods, a transesterification method and a direct polymerization method. In the former case, dimethyl terephthalate (D
By reacting MT) with ethylene glycol (EG),
Bishydroxyethyl terephthalate (BHT), that is, formula (2),

[0032]

[Chemical 2]

In the above formula, Φ is a paraphenylene group,
Alternatively, an oligomer thereof is formed, and this is polycondensed while removing EG. In the latter case, terephthalic acid (TA) is reacted with ethylene glycol (EG) to produce bishydroxyethyl terephthalate (BHT) or its oligomer, which is polycondensed while removing EG. In the direct polymerization method, the acidic group of terephthalic acid serves as a catalyst, and the reaction proceeds even without a catalyst.

In the above-mentioned reaction for producing bishydroxyethyl terephthalate (BHT) or its oligomer, diethylene glycol (DEG) is always by-produced by the condensation reaction of ethylene glycol (EG). Suppressing this by-product of diethylene glycol (DEG) is basically important in suppressing the production of the cyclic isomerized dimer (C2 ′) of the above formula (1).

Further, it is difficult to take out the once produced diethylene glycol (DEG) out of the system, and further, the formed diethylene glycol (DEG).
Since its reactivity is similar to that of ethylene glycol (EG), it is difficult to exclude it from the polyester system.

Even more troublesome is the inclusion of a diethylene glycol (DEG) component in the polyester, which results in the formation of cyclo (ethylene / ethyleneoxyethylene diterephthalate) during various heating processes. In a sense, diethylene glycol (DE
It is especially important to reduce the content of G).

Therefore, regardless of the transesterification method or the direct polymerization method, it is preferable to carry out the polycondensation in a high-vacuum atmosphere and immediately remove the generated EG out of the system. The content of the DEG component contained in the polyester is preferably 1.2% by weight or less, more preferably 1.1% by weight or less.

Polyesters suitable for bottles have a very high degree of polymerization, which is generally obtained by solid-state polymerization of polyester obtained by transesterification or direct polymerization. During this solid-state polymerization, the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate) in the DEG component increases, so solid-state polymerization at too high temperature should be avoided.
Solid phase polymerization at 40 ° C. or lower, particularly 180 to 220 ° C. for about 4 to 24 hours is desirable.

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. For example, a small amount of polybutylene terephthalate or liquid crystal polyester can be blended.

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 0.65 to 1.3 dl / g are desirable.

Injection molding is 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. At the time of this injection molding, the C2 'content in the bottle, that is, the preform was adjusted to 10%.
It is necessary to perform injection molding while suppressing the amount to 0 ppm or less, particularly 90 ppm or less. That is, substantially no cyclo (ethylene / ethyleneoxyethylene diterephthalate) formation occurs during injection molding into the preform. Since it is the temperature that has the greatest effect on C2 'as a by-product, injection molding should be carried out at a resin temperature as low as possible, preferably at 310 ° C or lower, particularly 270 to 300 ° C. .

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 an air vent in the cavity corresponding to the shape of the container and the portion corresponding to the preform mouth is used, but it is preferable to use the one-gate type or the multi-gate type. On the other hand, the injection pressure is preferably about 28 to 110 kg / cm ² .

Of course, the present invention may be applied to an ordinary bottle whose bottle mouth is not thermally crystallized.
Particularly great advantages are achieved when the preform mouth is thermally crystallized in order to increase the heat resistance and rigidity of the bottle mouth. This thermal crystallization of the mouth generally takes place between 140 and 22 with the mouth of the preform thermally insulated from the other parts.
It can be carried out by heating to a temperature of 0 ° C., particularly 160 to 210 ° C. The crystallinity of the preform mouth is preferably 25% or more.

According to the present invention, the polyester preform is stretch blow molded at the stretching temperature to give a neck,
Mold into a bottle with a barrel and bottom.

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.

In the stretch blow molding, the preform at the stretching temperature is stretched and stretched in the axial direction by a stretch rod with or without a blow molding die, and
The fluid is blown to expand and stretch in the circumferential direction. 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. Axial stretch ratio is determined by the axial length of the preform molded product and the stroke length of the stretching rod, the circumferential stretch ratio is determined by the relationship between the preform diameter and the mold cavity diameter, In the case of free blow, it is determined by the blowing pressure of the fluid.

The present invention is equally applicable to the production of ordinary bottles, pressure resistant bottles, heat resistant bottles, heat resistant pressure bottles and the like. In the case of heat resistant bottles, in order to absorb the reduced pressure after filling the contents with heat, a reduced pressure absorption mechanism is provided in the container body, such as a rib and a panel, and the reduced pressure is absorbed by the paneling deformation of the panel inside the container. You can
In a heat-resistant bottle, the container wall is heat-fixed to prevent thermal deformation of the container wall during heating. On the other hand, in a heat-resistant pressure bottle, after filling contents such as carbonated drinks having an autogenous pressure, heat sterilization by a pasteurizer etc., but in order to prevent creep deformation of the bottom part due to heat and pressure during this sterilization, It is preferable that the stretched portion or the low stretched portion is thermally crystallized, or the bottom portion is stretched and oriented and crystallized similarly to the case portion.

The heat setting of the bottle can be carried out by various means. For example, the blow molding die can be heated or a high temperature fluid can be blown into the bottle to perform heat setting simultaneously with stretch blow molding. Further, in addition to the blow molding die, a heat setting die can be used, and the bottle after blow molding can be placed in a heated heat setting die and heat fixed while blowing. Furthermore, the blow-molded bottle is taken out of the blow-molding mold, heat-set in a state where it can freely shrink, and then the heat-fixed bottle is put into the secondary blow-molding mold and blow-molded again to finish. Blow containers can also be manufactured.

The heat fixing of the container wall is generally 120 to 22.
It is suitable to carry out heating at a temperature of 0 ° C., particularly 130 to 210 ° C., and it can be carried out by heating the mold electrically or by heating the bottle directly with infrared rays or the like.

In the polyester bottle according to 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, particularly 250.
To 450 mm, while the basis weight is 2
It is preferably in the range of 5 to 45 g / l, particularly 30 to 40 g / l.

The polyester bottle according to the present invention is useful as a container for filling liquid contents, and a heat-resistant heat-resistant bottle is hot-filled with various beverages or liquid seasonings,
It is useful as a container for storing contents after sealing. The hot filling temperature is suitably 50 to 110 ° C. The heat-resistant pressure bottle can be used for the purpose of filling a carbonated beverage, sealing and then heat sterilizing, and a sterilizing temperature of 60 to 80 ° C. is suitable. In any of these cases, it is a remarkable advantage of the present invention that excellent sealing performance, pressure resistant sealing performance, heat resistant pressure sealing performance and continuous sealing performance can be obtained by plugging the sealing cap.

[0056]

The present invention will be further described in the following examples.

The measurement in the following examples was performed as follows. a) Intrinsic viscosity: 200 mg of a sample collected from a preform or a bottle is dissolved in 20 ml of a phenol / tetrachloroethane mixed solvent (weight ratio 1: 1) at 130 ° C. for 20 minutes with stirring. The solution viscosity is measured with an Ubbelohde viscometer in a constant temperature water bath at 30 ° C., and the intrinsic viscosity is calculated from this. t: drop time of solution (sec) to: drop time of solvent (sec) Specific viscosity ηSP = ηrel −1

B) Crystallinity: An n-heptane-carbon tetrachloride-based density gradient tube (Rika Ikeda Co., Ltd.) was prepared and
The density of the sample was determined under the condition of ° C. Thus, the crystallinity was calculated according to the following formula. ρ: Measured density (g / cm ³ ) ρam: Amorphous density (1.335 g / cm ³ ) ρC: Crystal density (1.455 g / cm ³ )

C) Content of C2 'in the bottle: The bottle was cut out and about 500 mg was precisely weighed to the nearest 0.1 mg. This was dissolved in 5 ml of a chloroform / hexafluoroisopropanol mixed solution (volume ratio 1: 1), diluted with 20 ml of chloroform, and then polyethylene terephthalate was reprecipitated using tetrahydrofuran to obtain a filtrate. After the filtrate was evaporated to dryness, the liquid dissolved in 10 ml of N, N-dimethylformamide was quantitatively analyzed by liquid chromatography.

D) Amount of depression at the tip of the mouth: As shown in FIG. 1, an enlarged photograph of the tip of the mouth is taken from the side, flat parts of the upper surface are designated as A and B, and they are connected by a straight line. The distance to the most depressed point C was measured as the amount of depression.

E) Resin temperature during injection molding Before starting injection molding, let the resin flow out from the nozzle tip,
The temperature is measured by a surface thermometer (HL-20, manufactured by Anritsu Keiki Co., Ltd.).
It was measured at 0).

Example 1 Polyethylene terephthalate resin (intrinsic viscosity 0.85d
1 / g, diethylene glycol copolymerization ratio 1.1% by weight,
A C2 ′ content of 52 ppm) was injection-molded at a resin temperature of 290 ° C. to prepare a bottomed preform having a weight of 49 g. This was heated to 105 ° C. with an infrared heater and stretch blow-molded to obtain a bottle having an internal capacity of about 1.5 l.

1 for every 10,000 shots of injection molding
Observe the mouth of each bottle at 0 bottles, and see if the tip of the mouth is clearly rounded compared to the first shot.
I checked if there were bubbles.

In Table 1, "roundness" indicates the occurrence of occurrence,
It is described as "bubble". In Table 1, “◯” indicates a state in which there is no “roundness” or “air bubbles” and the shape of the mouth tip is excellent. The content of C2 'was measured for each one.

Comparative Example 1 Molding, observation and analysis were carried out in the same manner as in Example 1. However, the material used has an intrinsic viscosity of 0.85 dl / g, a diethylene glycol copolymerization ratio of 2.0% by weight, and a C2 ′ content of 163 pp.
m. The results are shown in Table 1.

Comparative Example 2 Molding, observation and analysis were performed in the same manner as in Example 1 except that the resin temperature was changed to 315 ° C. The results are shown in Table 1.

As can be seen from Table 1, in Comparative Example 1, 200
At 00 shot, the outer peripheral corner of the tip of the mouth became rounded. Further, at 30,000 shots, air bubbles also came in. It is considered that these phenomena occurred because dirt was accumulated in the air vent portion and became clogged due to long-term continuous operation of the injection molding machine, resulting in poor air release. When the content of C2 'in the bottle is measured, it is found that it is 200 to 235 ppm, which is considerably higher than 100 ppm or less.

On the other hand, in Example 1, the C2 'content was as small as 60 to 78 ppm, and the state of the tip of the mouth was as good as that of the first shot even after 50,000 shots.

Comparative Example 2 was different from Example 1 only in that the resin temperature at the time of injection molding was changed, but was rounded at 30,000 shots. At this time, the C2 'content is 112 to 128 pp
It can be seen that m is about twice as large as that in the first embodiment.

This means that even if the same material is used, the content of C2 'will change if the injection molding conditions change. Since it is the same material, the C2 'content should be the same at the pellet stage, so the difference at the bottle stage is considered to be the difference in the increase in oligomers due to thermal decomposition during injection molding, that is, during resin melting. . C2 'increased because the resin temperature increased.

[0071]

[Table 1]

Example 2 Polyethylene terephthalate resin (intrinsic viscosity 0.77d
1 / g, diethylene glycol copolymerization rate 1.0% by weight,
A C2 ′ content of 59 ppm) was injection molded at a resin temperature of 290 ° C. to prepare a bottomed preform having a weight of 59 g. After whitening and crystallizing the mouth of this by heat treatment, the parts other than the mouth are heated to 100 ° C. by an infrared heater,
Stretch blow molding was performed in a mold at 0 ° C. to obtain a bottle having an internal volume of about 1.5 l. Continuously operating this injection molding machine, about 100 shots, about 5000 shots, about 1000 shots
With respect to the 0th shot bottle, quantitative analysis of C2 ′ in the bottle and measurement of the amount of depression at the tip of the mouth were performed. The results are shown in Table 2.

Comparative Example 3 Bottle molding and measurement were carried out in the same manner as in Example 2. However, the material used has an intrinsic viscosity of 0.78 dl / g, a diethylene glycol copolymerization rate of 1.3% by weight, and a C2 ′ content of 103 pp.
It was m.

[0074]

[Table 2]

From Table 2, it can be seen that in the case of Example 2, no dent was formed in the mouth. At this time, C in the bottle
The 2'content is within the claimed range of 100 ppm or less.

On the other hand, in Comparative Example 3, the dent at the tip of the mouth does not yet appear at about the 100th shot, but the pit started to appear at about the 5,000th shot, and about 1
At the 0000th shot, the amount of depression is considerably large. The content of C2 'is larger than the range of the present invention.

If it is more than 100 ppm, the air vent will become clogged after a long time of operation, and residual strain will be generated around the part communicating with the air vent, which will be alleviated when the mouth is whitened by heat treatment. It seems that it will be moved, resulting in a depression.

[0078]

According to the present invention, an ethylene terephthalate polyester is used to carry out injection molding and stretch blow molding so that the C2 'content in the bottle is maintained at 100 ppm or less. A polyester bottle that does not have defects such as poor appearance or poor sealing, reduces the tendency of the preform injection mold to block the air vent,
Further, it is possible to manufacture the injection mold stably and with high productivity, without having to frequently clean the injection mold.

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Claims (5)

[Claims] 1. A method for producing a polyester bottle comprising injection-molding a thermoplastic polyester resin into a preform and stretch-blowing the obtained preform at a stretching temperature, wherein the thermoplastic polyester resin has an intrinsic viscosity of 0.6. To 1.4 dl / g and the content of cyclo (ethylene / ethyleneoxyethylene diterephthalate) is 80 ppm or less, ethylene terephthalate polyester is used, and cyclo (ethylene /
A method for producing a polyester bottle, which comprises suppressing the content of (ethyleneoxyethylene diterephthalate) to 100 ppm or less. 2. The method according to claim 1, wherein the polyester is produced under the condition that the resin temperature during injection molding is 310 ° C. or lower. 3. The method for producing a polyester bottle according to claim 1, wherein the preform or the mouth of the bottle is thermally crystallized by heating. 4. An ethylene terephthalate-based polyester having an intrinsic viscosity of 0.6 to 1.4 dl / g and a cyclo (ethylene / ethyleneoxyethylene diterephthalate) content in the bottle of 100 ppm or less. Polyester bottle to do. 5. A heat-resistant polyester bottle having a mouth whitened by thermal crystallization, which is formed from ethylene terephthalate-based polyester having an intrinsic viscosity of 0.6 to 1.4 dl / g and has a cyclo (ethylene / Content of ethylene oxyethylene diterephthalate) is 100p
pm or less and the amount of depression at the tip of the mouth is 0.50 m
A heat-resistant polyester bottle characterized by being m or less.