JP5239480B2 - Polyethylene terephthalate bottle - Google Patents

Description

  The present invention relates to a polyethylene terephthalate bottle, and more particularly to a polyethylene terephthalate bottle that can be thinned including the bottom, has a well-balanced thickness distribution, and is excellent in mechanical strength.

Bottles made of polyester resin typified by polyethylene terephthalate are widely used as containers for beverages, oils, seasonings, etc. due to their excellent properties such as transparency and mechanical strength. From the viewpoint of CO ₂ reduction, further thinning of the bottle is required.
For example, in Patent Document 1 below, the thickness of the stretched and molded vessel wall except for the mouth and neck is almost uniform, and the ratio of the thickest part to the thinnest part is 1.0 to 2. 0.0, a blow-molded container in which the shoulder, body, and bottom are highly stretched, and the vessel wall excluding the mouth and neck is oriented and crystallized, and the stretch orientation of the connection from the shoulder to the mouth and neck A high stretch blow molded container having a crystallinity of 20% or less has been proposed.

However, although it is easy to reduce the thickness of the body portion having a high draw ratio, there is a limit to reducing the thickness in order to ensure the mechanical strength, and it has been difficult to reduce the thickness in a balanced manner including the bottom portion.
In addition, as a polyester bottle having a thin bottom, a plastic bottle having a heat-resistant lightweight bottom having a raised bottom and an annular grounding portion around the raised bottom, and the mass per projected area of the raised bottom is 0.00. A plurality of recesses recessed inward of the bottle in a region from 04 to 0.1 g / cm ² and from the position spaced below the top surface of the raised bottom to the inner periphery of the annular grounding portion; A plurality of convex portions projecting outward from the bottle are alternately provided in a radial pattern, and the plurality of concave portions have an area smaller than that of the plurality of convex portions. Plastic bottles have also been proposed
(Patent Document 2).

Japanese Patent Laid-Open No. 5-442 JP 2005-112361 A

  In the heat-resistant bottle, it is necessary to increase the crystallinity of the polyester resin and improve the heat resistance by thermally crystallizing the mouth portion and performing a two-stage blow molding method. Therefore, the intrinsic viscosity is high and the crystallization speed is high. A slow polyester resin cannot efficiently perform thermal crystallization and heat setting of the mouth. Therefore, an expensive polyester resin produced by a special method such as using a specific catalyst or a crystal nucleating agent has been used.

  Therefore, the object of the present invention is to use a polyester resin whose intrinsic viscosity is increased by solid-phase polymerization as it is, and can be thinned including the bottom, has a well-balanced thickness distribution, and is highly compressed with respect to an axial load. It is to provide a polyethylene terephthalate bottle having strength.

According to the present invention, there is provided a polyester bottle formed by biaxially stretching blow molding polyethylene terephthalate mainly composed of an ethylene terephthalate unit and having an intrinsic viscosity in a range of 0.80 to 1.0 dL / g. )
P = (W ₁ / S ₁ ) / (W ₂ / S ₂ ) (1)
Where W ₁ is the weight of the torso, S ₁ is the surface area of the torso, W ₂ is the weight of the bottom, and S ₂ is the surface area of the bottom.
In represented, the ratio P is 0.45 to 0.85 range near the weight per unit surface area of the weight and the bottom of the per unit surface area of the body is, the average thickness of the body portion of 0.20 to 0 a .50Mm, the thickness of the thinnest portion of the barrel polyethylene terephthalate bottle is provided, wherein 0.20 to 0.35mm der Rukoto.
According to the polyethylene terephthalate bottle of the present invention,
1. Polyethylene terephthalate is a homopolyethylene terephthalate polymerized using a Ti-based catalyst, and the ratio P of the weight per unit surface area of the body portion to the weight per unit surface area of the bottom portion is in the range of 0.50 to 0.70. There is,
2 . The average thickness of the bottom is 0.25 to 0.60 mm, and the thickness of the thickest part outside the ground contact portion of the bottom is 0.30 to 0.60 mm.
3 . Biaxial stretch blow molding by a one-stage blow method,
Is preferred.

According to the polyethylene terephthalate bottle of the present invention, it has a well-balanced wall thickness distribution, in particular, it is possible to reduce the thickness of the bottom, and it is possible to reduce the weight and cost of the bottle, and it is also excellent in moldability. .
Moreover, the polyethylene terephthalate bottle of the present invention is excellent in that it is not deformed even when a high compressive load of 30 kgf or more, particularly 35 kgf or more is applied in the bottle axial direction, even though it is thinned including the bottom. It has mechanical strength.
Polyethylene terephthalate prepared so that the intrinsic viscosity is in the range of 0.80 to 1.0 dL / g by solid-phase polymerization used in the present invention is low molecular weight components such as acetaldehyde that cause a decrease in flavor, Since oligomers such as cyclic trimers that cause mold contamination are sufficiently reduced, flavor retention is excellent, and productivity is excellent because frequent mold cleaning is not required.

In the polyethylene terephthalate (hereinafter, also referred to as “PET”) bottle of the present invention, polyethylene terephthalate mainly composed of ethylene terephthalate units and having an intrinsic viscosity in the range of 0.80 to 1.0 dL / g is biaxially stretched. The first feature is that it is blow-molded, and the ratio P of the weight per unit surface area of the body and the weight per unit surface area of the bottom represented by the above formula (1) is 0.45 to 0.85. The second characteristic is that it is within the range.
Polyethylene terephthalate having an intrinsic viscosity of 0.80 to 1.0 dL / g, which is in a high range, can obtain a high stretching tension, so that it can be thinned not only at the body but also at the bottom in biaxial stretch blow molding. Yes, a well-balanced wall thickness distribution can be obtained as a whole bottle. In the present invention, in particular, in a PET bottle in which the ratio P of the weight per unit surface area of the body part represented by the above formula (1) to the weight per unit surface area of the bottom part is in the range of 0.45 to 0.85. The inventors have found that a high compressive strength is obtained with respect to the axial load, and that it has excellent mechanical strength while being thin and lightweight.

  That is, as is clear from the results of the examples described later, when the ratio P of the weight per unit surface area of the body and the weight per unit surface area of the bottom represented by the above formula (1) is larger than the above range. If the barrel is too thick and the bottom is too thin, a satisfactory bottle cannot be formed (Comparative Example 1). On the other hand, when the ratio P is smaller than the above range, the bottom portion is too thick to reduce the weight, and a satisfactory compressive strength is not obtained (Comparative Example 3). On the other hand, when the ratio P is in the above range, it has a compressive strength of 35 kgf or more with respect to the axial load, and clearly has an excellent mechanical strength (implementation). Examples 1-3).

(polyethylene terephthalate)
The polyethylene terephthalate used in the present invention is a polyethylene terephthalate having an intrinsic viscosity of 0.80 to 1.0 dL / g, particularly 0.80 to 0.85 dL / g.
The intrinsic viscosity is measured at a temperature of 25 ° C. using a phenol / tetrachloroethane mixed solvent having a weight ratio of 1: 1.
Polyethylene terephthalate is generally produced through liquid phase polymerization and, if necessary, solid phase polymerization, but is prepared by liquid phase polymerization and solid phase polymerization so that the intrinsic viscosity is in the range of 0.80 to 1.0 dL / g. Polyethylene terephthalate has low molecular weight components such as acetaldehyde that cause a decrease in flavor, and oligomers such as cyclic trimers that cause mold contamination during molding, and has a large stretch tension. The thickness distribution is easily controlled.

In general, polyester resins obtained using Sb-based catalysts, Ge-based catalysts, Ti-based catalysts, etc. are used as polyester resins used for the production of containers by biaxial stretch blow molding. As long as the viscosity and the ratio P are in the above ranges, polyethylene terephthalate by any polymerization catalyst can be used. However, homopolyethylene terephthalate polymerized using a Ti-based catalyst is preferable.
That is, as is clear from the results of Examples described later, a bottle made of polyethylene terephthalate obtained using a Ti-based catalyst has a bottom portion lower than that of polyethylene terephthalate obtained using an Sb-based catalyst or a Ge-based catalyst. In addition, it has a well-balanced thickness distribution that can be thinned, and a value with the highest compressive strength against an axial load is obtained.
In general, a polyester resin obtained using an Sb-based catalyst is used by being copolymerized because of its high crystallization speed due to the nature of the catalyst, and obtained using a Ge-based catalyst and a Ti-based catalyst. Since the obtained polyester resin is excellent in hygiene, it is often used for heat-resistant bottles. For this reason, high crystallinity is required, and those having low intrinsic viscosity are generally used.

The polyethylene terephthalate used in the present invention is mainly composed of ethylene terephthalate units, and preferably 80% or more of the ester repeating units are occupied by ethylene terephthalate units, and particularly homopolyethylene terephthalate in which all of them are occupied by ethylene terephthalate units is optimal. However, it is not excluded to include diol components other than ethylene glycol and dicarboxylic acids other than terephthalic acid as impurities, and preferably prepared by a conventionally known polymerization method except that a Ti-based catalyst is used. Can do.
The polyethylene terephthalate used in the present invention is not limited to this, but preferably has a glass transition point (Tg) of 50 to 90 ° C. and a melting point (Tm) of 200 to 275 ° C.
The polyethylene terephthalate used in the present invention contains known resin compounding agents such as colorants, antioxidants, stabilizers, various antistatic agents, mold release agents, lubricants, nucleating agents, etc. Can be blended in accordance with a known formulation within a range that does not impair.

(PET bottle)
In the PET bottle of the present invention, it is possible to adopt various shapes of conventionally known polyester bottles having a mouth portion, a shoulder portion, a trunk portion, and a bottom portion, and the size can be adjusted to all the conventionally known contents. It can take the form provided.
FIG. 1 is a side view showing an example of the PET bottle of the present invention obtained by the embodiment. This PET bottle has a mouth portion 1, a shoulder portion 2, and a trunk portion 3 with a waist portion 4 and an upper trunk portion 3a. The lower body 3b is partitioned. The bottom portion 5 includes a heel portion 5b that extends from the lower end of the body portion 3 to the bottle ground contact portion 5a, and a bottom portion 5c that protrudes inward from the bottle ground contact portion 5a.
In the present invention, it is preferable that the average thickness of the body is in the range of 0.20 to 0.50 mm, particularly 0.30 to 0.35 μm, and the thickness of the thinnest part of the body is 0. It is preferably in the range of 20 to 0.35 mm, particularly in the range of 0.25 to 0.30 μm.
The average thickness of the bottom is preferably in the range of 0.25 to 0.80 mm, particularly 0.45 to 0.70 μm, and the thickness of the thickest portion on the outer side (the heel portion) outside the grounding portion of the bottom is preferred. The thickness is preferably in the range of 0.30 to 0.60 mm, particularly 0.40 to 0.50 μm.
In the present invention, the trunk portion refers to the shoulder portion (the portion whose inner diameter increases as it goes downward from the mouth portion) and the bottom portion (the portion whose inner diameter increases as it goes upward outside the grounding portion ( The part located between the said heel part) and the part inside a grounding part).
The surface area of the bottle can be calculated by measuring the surface shape of the bottle three-dimensionally, but can also be calculated from electronic data of a product drawing. In addition, minute irregularities due to the surface treatment of the mold do not affect the wall thickness and are ignored.

The PET bottle of the present invention is particularly suitable for the use of an aseptic bottle that sterilizes each of the bottle and the contents and then fills the contents in an aseptic state, or a pressure-resistant bottle for filling the contents having an autogenous pressure. . When used for a pressure-resistant bottle, it is formed into a conventionally known bottom shape such as a so-called petaloid shape or champagne shape.
The PET bottle of the present invention is preferably a single-layer bottle made of the above-mentioned polyethylene terephthalate, but is a multilayer bottle having the above-mentioned polyethylene terephthalate as the inner and outer layers and another thermoplastic resin as the intermediate layer. Also good.
Other thermoplastic resins that can be used as an intermediate layer in multilayer bottles are not limited to these, but gas barrier resins such as ethylene vinyl alcohol copolymers and polyamide resins, and oxidation to such gas barrier resins. A conventionally well-known thing, such as an oxygen absorptive resin composition mix | blended with an organic component and a transition metal catalyst, can be used.
In the case of a multilayer bottle, the thickness of the intermediate layer is preferably in the range of 0.5 to 25% of the average thickness of the body and 0 to 25% of the average thickness of the bottom.
In addition, the other thermoplastic resins described above can be blended within a range that does not affect the appearance of the container, and in that case, it is preferably blended within a range of 0.5 to 25% by weight.

(Molding bottle)
The polyethylene terephthalate bottle of the present invention uses a single layer preform made of the above-mentioned polyethylene terephthalate or an inner / outer layer made of the above-mentioned polyethylene terephthalate and uses a multilayer preform having another thermoplastic resin as an intermediate layer. It can be molded by a biaxial stretch blow molding method.
As can be seen in Patent Document 2, if the two-stage blow method is used, the bottom can be uniformly thinned. However, two-stage blow molding requires special equipment and is widely used for one-stage blow. The present application is significant in that it can be implemented with a biaxial stretch blow molding apparatus.

Prior to biaxial stretching blow molding, the preform is preheated to a stretching temperature of 85 to 135 ° C. by means of hot air, infrared heater, high frequency induction heating or the like. This heated preform is supplied into a stretch blow molding machine known per se, set in a mold, stretched in the axial direction by pushing a stretching rod, and stretched in the circumferential direction by blowing fluid. To do.
The draw ratio of the polyethylene terephthalate bottle, which is the final product, is in the range of 1.5 to 25 times in area magnification, 1.2 to 6 times in axial direction draw ratio, and 1.2 to 4.5 times in circumferential direction draw ratio. Preferably there is.
In the polyethylene terephthalate bottle of the present invention, it is not always necessary after biaxial stretch blow molding, but it may be heat-set (heat set) depending on the application. The mold temperature in the heat setting is preferably in the range of 130 to 160 ° C. for 1 to 5 seconds.
When adjusting the bottle thickness distribution at the time of biaxial blow molding, a method of appropriately adjusting the output of a plurality of heaters arranged in the height direction, or by blowing cold air to a desired position of the preform after heating A method of locally cooling is generally used.

  The polyethylene terephthalate bottle of the present invention is industrially suitable for the use of an aseptic bottle or a pressure-resistant bottle, in which thermal crystallization and heat setting of the mouth are not essential, because the crystallization speed of polyethylene terephthalate used is slow. However, it does not mean that the steps of thermal crystallization and heat setting cannot be performed, and it is possible to form a heat-resistant bottle or a heat-resistant and pressure-resistant bottle by taking time.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.
1. [Measurement of intrinsic viscosity]
Polyester resin pellets were frozen and ground, and 0.20 g of polyester resin dried at 140 ° C. for 15 minutes was weighed, and a mixed solvent of 1,1,2,2-tetrachloroethane / phenol (1/1) (weight ratio) was added. Using 20 ml, stir at 120 ° C. for 15 minutes to completely dissolve. After dissolution, the solution was cooled to room temperature, and the intrinsic viscosity [η] was determined by the following formula using an Ubbelohde viscometer (manufactured by Kosei Co., Ltd.) whose temperature was adjusted to 25 ° C. through a glass filter.
[Η] = (− 1 + √ (1 + 4K′η _Sp )) / 2K′C
η _Sp = (τ−τ ₀ ) τ ₀
here,
[Η]: Intrinsic viscosity (dl / g)
η _Sp : specific viscosity (−)
K ′: constant of Haggins (= 0.33)
C: Concentration (= 1 g / dl)
τ: Sample drop time (sec)
τ ₀ : solvent falling time (sec)
2. [Measurement of compressive strength]
For a bottle filled with a predetermined amount of water and sealed, compression is started at a compression speed of 50 mm / min using an autograph manufactured by Shimadzu Corporation. The measurement is complete when buckling occurs and the compressive load decreases. The inflection point at this time is defined as the compressive strength.
3. [Molding of bottles]
A 55 g weight preform molded by an injection molding machine using the polyethylene terephthalate shown in each example and comparative example was heated to about 126 ° C. and set in a mold heated to about 120 ° C. Biaxial stretch blow molding was performed at a longitudinal draw ratio of 2.22 times, a transverse draw ratio / long side of 4.41 times, and a short side of 3.67 times by a step blow method to form a square polyethylene terephthalate bottle shown in FIG. . This bottle is a Contents 2L, collar under height 284 mm, barrel width and long side 105 mm, a short side 87 mm, surface area 739cm ² of the body surface area of the bottom 146cm ^2.
In the biaxial stretch blow molding, the stretching temperature is measured at a position about 30 mm below the flange of the preform immediately after the end of heating, and the output of the eight infrared heaters arranged in the height direction is 126 ± 1 ° C. Within each range, the thickness distribution (= weight distribution) of the bottle was adjusted.

[Example 1]
A preform was molded using a Ti-based catalyst homopolyethylene terephthalate having an intrinsic viscosity of 0.85 dL / g, and the bottle was biaxially stretch blow-molded while adjusting the heating conditions with the aim of an average body thickness of 0.34 mm. .
When the obtained bottle was actually measured, P = 0.67, the trunk average thickness 0.334 mm, the thinnest part 0.285 mm, the bottom average thickness 0.506 mm, and the heel thickest part 0.420 mm. Met.
Table 1 shows the compression strength and weight distribution of the bottles obtained.

[Example 2]
Using the same preform as in Example 1, the bottle was biaxially stretch blow-molded by adjusting the heating conditions so that the average thickness of the body portion was slightly thicker than in Example 1.
When the obtained bottle was measured, P = 0.65, the trunk average thickness 0.336 mm, the thinnest part 0.290 mm, the bottom average thickness 0.522 mm, and the heel thickest part 0.429 mm. Met.
The thickness distribution of the obtained bottle is shown in FIG. 2, and the compressive strength and weight distribution are shown in Table 1.

[Comparative Example 1]
Using the same preform as in Example 1, the bottle was biaxially stretch blow-molded by adjusting the heating conditions so that the bottom was thinner than in Example 1.
When the obtained bottle was measured, P = 0.87, the trunk average thickness 0.360 mm, the thinnest part 0.322 mm, the bottom average thickness 0.419 mm, and the heel part the thickest part 0.390 mm Met.
Table 1 shows the weight distribution of the obtained bottles. A compression test was not performed because a molding failure was observed in the heel portion.

[Example 3]
A bottle was obtained in the same manner as in Example 1 using Ti-based catalyst homopolyethylene terephthalate having an intrinsic viscosity of 0.80 dL / g. Biaxial stretch blow molding was performed with the average thickness of the body portion being 0.30 mm or more.
When the obtained bottle was actually measured, P = 0.52, the trunk average thickness 0.316 mm, the thinnest part 0.271 mm, the bottom average thickness 0.624 mm, and the heel thickest part 0.470 mm. Met.
Table 1 shows the compression strength and weight distribution of the bottles obtained.

[Comparative Example 2]
A bottle was obtained in the same manner as in Example 1 using 1.5 mol% copolymerized polyethylene terephthalate of Sb-based catalyst isophthalic acid having an intrinsic viscosity of 0.85 dL / g. Since stable molding was difficult when the average thickness of the body portion was 0.34 mm, biaxial stretch blow molding was performed by adjusting the heating conditions with the average thickness of the body portion being 0.30 mm or more.
When the obtained bottle was measured, P = 0.46, the trunk average thickness 0.305 mm, the thinnest part 0.260 mm, the bottom average thickness 0.665 mm, and the heel thickest part 0.485 mm. Met.
The thickness distribution of the obtained bottle is shown in FIG. 2, and the compressive strength and weight distribution are shown in Table 1.

[Comparative Example 3]
A bottle was obtained in the same manner as in Example 1 using a Ge-based catalyst homopolyethylene terephthalate having an intrinsic viscosity of 0.75 dL / g. Since stable molding was difficult when the average thickness of the body portion was 0.34 mm, biaxial stretch blow molding was performed by adjusting the heating conditions with the average thickness of the body portion being 0.30 mm or more.
When the obtained bottle was actually measured, P = 0.40, the trunk average thickness 0.293 mm, the thinnest part 0.235 mm, the bottom average thickness 0.752 mm, and the heel thickest part 0.523 mm. Met.
The thickness distribution of the obtained bottle is shown in FIG. 2, and the compressive strength and weight distribution are shown in Table 1.

式中、Ｗ_１は胴部の重量、Ｓ_１は胴部の表面積、Ｗ_２は底部の重量、Ｓ_２は底部の表面積
以上の実施例の中でも特に実施例１，２は胴部の肉厚に余裕があり、更に軽量化を進めることが可能と見込まれる。

In the formula, W ₁ is the weight of the body, S ₁ is the surface area of the body, W ₂ is the weight of the bottom, and S ₂ is the surface area of the bottom. It is expected that further weight reduction will be possible.

It is a side view of an example of the polyethylene terephthalate bottle of the present invention. It is a figure which shows the thickness in each site | part of a bottle about the bottle obtained by the Example and the comparative example.

Claims (4)

A bottle formed by biaxially stretching blow molding polyethylene terephthalate mainly composed of an ethylene terephthalate unit and having an intrinsic viscosity in a range of 0.80 to 1.0 dL / g, and having the following formula P = (W ₁ / S ₁ ) / (W ₂ / S ₂ )
Where W ₁ is the weight of the torso, S ₁ is the surface area of the torso, W ₂ is the weight of the bottom, and S ₂ is the surface area of the bottom.
In represented, the ratio P is 0.45 to 0.85 range near the weight per unit surface area of the weight and the bottom of the per unit surface area of the body is, the average thickness of the body portion of 0.20 to 0 a .50Mm, polyethylene terephthalate bottle wall thickness of the thinnest portion of the body portion, wherein 0.20 to 0.35mm der Rukoto.   The polyethylene terephthalate is a homopolyethylene terephthalate polymerized using a Ti-based catalyst, and the ratio P of the weight per unit surface area of the body portion to the weight per unit surface area of the bottom portion is 0.50 to 0.70. The polyethylene terephthalate bottle according to claim 1. The polyethylene terephthalate bottle according to claim 1 or 2, wherein an average thickness of the bottom portion is 0.25 to 0.60 mm, and a thickness of a thickest portion outside the ground contact portion of the bottom portion is 0.30 to 0.60 mm. . The polyethylene terephthalate bottle according to any one of claims 1 to 3 , wherein the polyethylene terephthalate bottle is biaxially stretch blow molded by a one-stage blow method.

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