JP2002067129A - Biaxially stretched polyester bottle and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester bottle improving appearance characteristics by preventing a warp deformation of a panel part and a method for manufacturing the same. SOLUTION: The heat set biaxially stretched polyester bottle comprises the panel part on the body so that crystallinity of the panel part is 25% or more and is lower than the crystallinity of its periphery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched polyester bottle with a panel capable of hot-filling (hot filling) the contents and a method for producing the same. The present invention relates to a biaxially stretched polyester bottle which prevents outward protrusion deformation, that is, warpage, and a method for producing the same. Further, the present invention can solve the problem of poor appearance due to oligomer adhesion to the mold, reduce the temperature of the mold to be used, simplify the panel shape formed on the bottle, and further reduce the temperature in the mold. The present invention also relates to a method for producing the above polyester bottle with high productivity by shortening the occupation time of the bottle.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
The biaxially stretched blow-molded bottle of thermoplastic polyester has excellent transparency and surface gloss, as well as the necessary impact resistance, rigidity, and gas barrier properties of the bottle. Has been used as.

[0003] However, polyester containers have a drawback of poor heat resistance. For applications such as hot filling and heat sterilization of the contents, thermal deformation and shrinkage of the volume are caused. After molding the blow container, heat set (heat
Set) is required.

[0004] The method of heat fixing is disclosed in JP-B-60-5660.
As disclosed in Japanese Patent Application Publication No. 6 (1999) -6, a method in which a molded product obtained by stretch blow molding is removed from a blow mold and then held in a heat fixing mold to perform heat fixing, and Japanese Patent Publication No. 59-62.
As seen in JP-A-16, a method of performing heat setting simultaneously with a stretch blow mold in a blow mold is known. JP-A-57-53326 discloses a method in which heat treatment is performed simultaneously with stretch blow molding in a primary mold, and a molded product is taken out and cooled in a secondary mold without cooling. Has been described.

Japanese Patent Application Laid-Open No. 63-59 filed by the present applicant
No. 513 discloses that a blow mold is maintained at a temperature of 100 to 120 ° C., and a thermoplastic polyester preform is heated to a specific temperature in relation to its intrinsic viscosity and diethylene glycol content. It is described that a high-temperature hot air is blown into the preform and the preform is stretched at a high speed to produce a heat-resistant polyester hollow molded article by a one-mold method.

[0006] Deformation of the heat-resistant container includes so-called thermal deformation in which the side wall of the container is simply deformed by heat, and pressure reduction caused by a change in the internal volume when the container comes into contact with hot contents and is then cooled. There is deformation. In order to prevent decompression deformation, a concave panel part and a bulging pillar part are provided on the container side wall,
It is common practice to use the deformation caused by the bulging and dent of the panel to absorb the increase and decrease of the internal volume and prevent irregular deformation of the container. If the thickness is not sufficient, the panel portion is thermally deformed, and a disadvantage arises in that the function of adjusting the internal volume due to the bulging and recessing of the panel portion does not function well.

[0007] Patent No. 27 filed by the present applicant
No. 57732 discloses a pillar-shaped convex portion which is formed by stretching blow molding of a thermoplastic polyester and heat-fixed and which is located relatively radially outward on a body portion of a container and has a short circumferential length; And a plurality of panel-shaped concave portions having a long circumferential length are alternately provided in the circumferential direction via short connecting portions,
In a heat-resistant container provided with a label portion above or below the body portion as necessary, the body portion of the container is entirely oriented and crystallized by heat fixing, and the panel-shaped concave portion is a pillar-shaped convex portion or other. A polyester container provided with a body part having a partially different degree of crystallinity, which is characterized by being highly thermally crystallized as compared with the part described in (1).

[0008]

However, in the case of a polyester bottle with a panel in which the body of the bottle is biaxially stretched and heat-set, the center portion is more or less than the upper and lower sides of the panel portion. In addition, there is a need for further improvement in the appearance characteristics and commercial value of the bottle.

In the conventional heat setting method, a method is used in which the entire mold is heated to a high temperature and the side wall (body) of the container to be molded is highly crystallized. The oligomer in the polyester precipitates on the mold surface, and after this deposit (trace) is transferred to the surface of the bottle to be molded,
There is a problem that the gloss and transparency of the bottle are impaired. Since the panel portion of the bottle is a flat and conspicuous portion of the bottle container wall, if the gloss or transparency of the panel portion is reduced as described above, the appearance becomes poor, which is likely to lead to a reduction in commercial value.

Further, in order to crystallize the panel portion to a high degree, a long time is required for heat fixing, and a long time is required for cooling the heat-fixed container, and the occupation time in the mold becomes long. In addition, there is a disadvantage that productivity is reduced.

Accordingly, an object of the present invention is to provide a heat-set biaxially stretched polyester bottle in which the above-described panel portion is prevented from warping and the appearance characteristics are improved, and a method for producing the same. Another object of the present invention is to provide a biaxially stretched polyester bottle with a panel, which prevents the occurrence of mold stains and as a result has excellent appearance characteristics such as gloss and transparency of the bottle, and a method for producing the same. Still another object of the present invention is to reduce the temperature of the mold used and simplify the shape of the panel formed on the bottle, shorten the occupation time in the mold, and reduce the polyester bottle. An object of the present invention is to provide a method which can be manufactured with high productivity.

[0012]

According to the present invention, in a heat-set biaxially stretched polyester bottle having a panel portion in a body portion, the crystallinity of the panel portion is 25% or more, and the crystallization of the peripheral portion thereof is performed. A biaxially stretched polyester bottle is provided, characterized in that the bottle is less than 1%. In the bottle of the present invention, the difference (Co-Cp) between the crystallinity (Co) of the periphery of the panel portion and the crystallinity (Cp) of the panel portion is 3% or more, particularly 4 to 7%. preferable. According to the present invention, there is also provided a method for producing a heat-set biaxially stretched polyester bottle having a panel portion on a body portion, wherein a preform heated to a molding temperature is heated to a temperature of a mold portion excluding a panel corresponding portion by 120. C. or higher, and the panel corresponding portion of the mold is biaxially controlled in a mold whose temperature is controlled to a temperature equal to or higher than the glass transition point (Tg) of polyester and lower than the temperature of the mold portion excluding the panel corresponding portion. There is provided a method for producing a biaxially oriented polyester bottle, which is characterized by being subjected to stretch blow molding. In the manufacturing method of the present invention, the temperature (Tp) of the portion corresponding to the panel of the mold is set to a temperature lower by at least 20 ° C., preferably 30 to 50 ° C. than the temperature (To) of the mold portion excluding the portion corresponding to the panel. It is preferable to control the temperature.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Action] In the bottle of the present invention, the body is oriented and thermally crystallized by biaxial stretch blow molding of polyester and heat setting. It is characterized by being at least 25% and lower than its peripheral part. The manufacturing method is to maintain the temperature of the mold part excluding the panel at 120 ° C. or more and to make the panel part of the mold a glass transition of polyester. It is characterized by performing biaxial stretch blow molding in a mold adjusted to a temperature not lower than the point (Tg) and lower than the temperature of the mold portion excluding the panel. According to the present invention, the warp deformation of the panel portion after hot filling can be effectively prevented by this feature.

Please refer to FIG. 6 of the accompanying drawings. In FIG. 6, after filling hot water into a polyester bottle manufactured by various methods (for details, see examples to be described later), the shape of the vertical cross section and the warpage of the panel portion with the upper side being the outer side and the lower side being the inner side are shown. The amount of generation (unit: mm) is shown. According to this result, in the bottle (C) including the panel portion having a crystallinity lower than 25% without performing the heat fixing in the mold, not only the panel portion but also the entire bottle greatly shrank. Also, 1
In a bottle (D, E) in which the crystallinity of the panel portion is the same as the crystallinity of the other parts in the bottle (D, E), hot filling is performed with hot water before moisture absorption. The amount of warpage after the filling was 1.61 mm, and the amount of warpage after filling with hot water was 2.04 mm in filling the bottle after absorbing moisture. Furthermore, in the bottles (F, G) in which the crystallinity of the panel portion is the same as the crystallinity of the other surroundings at 150 ° C., the filling of the bottle before absorbing moisture is performed with hot water. The amount of warpage after filling was 1.07 mm, and the amount of warpage after filling with hot water was 1.0% in filling the bottle after absorbing moisture.
0 mm. On the other hand, the mold part of the panel part is 9
The bottles (A, B)
Then, the surprising fact that the panel part after hot water filling is extremely flat and does not generate any warp, whether in filling the bottle before absorbing moisture or filling the bottle after absorbing moisture, becomes clear. .

That is, according to the conventional common sense, it was believed that highly crystallizing the trunk including the panel was effective in preventing the thermal deformation of the trunk including the panel. However, in the present invention, the crystallinity of the panel portion is 25%.
The orientation thermal crystallization is performed as described above, but by suppressing the crystallinity of the panel portion to a value lower than the crystallinity of the other surroundings, the warpage deformation of the panel portion after hot filling is effectively performed. It has been found to be suppressed.

In the present invention, the fact that the deformation of the panel portion is prevented from being warped by setting the distribution of the crystallinity of the body portion with the panel within the above range has been found as a phenomenon as a result of many experiments. The reason is not speculation, but is considered as follows.

Generally, in heat setting of the stretched polyester,
Since the crystallization speed of polyester is increased by stretching,
It can be performed for a short time or at a relatively low temperature, and since this stretch crystallization does not involve the formation of spherulites, it also has the advantage that the transparency does not decrease. Further, the crystallinity and the glass transition point (Tg) are certainly improved with the heat setting, but the elastic modulus of the polyester is not improved. With respect to the heat setting temperature, the elastic modulus increases with the temperature. It is known that it tends to decrease monotonically. It is said that this is because the extended chain crystal at the time of stretching changes into a folded structure by heat treatment.

In the polyester bottle according to the present invention, the heat setting of the panel portion is performed at a lower temperature than the heat setting of the other peripheral portions, and as a result, the crystallinity of the panel portion is reduced. It is suppressed to a range lower than the crystallinity. Therefore, in the panel portion of the polyester bottle of the present invention, thermal crystallization is performed to the extent that thermal deformation can be prevented, but extended chain crystals formed at the time of stretching also effectively remain, and the elasticity of the panel is reduced. It is recognized that warpage is prevented by the recovery.

Further, according to the present invention, since the temperature of the body mold including the panel portion can be reduced, the occurrence of mold contamination due to the migration of oligomers is prevented, and as a result, the gloss and transparency of the bottle are reduced. There is an advantage that a biaxially stretched polyester bottle with a panel having excellent appearance characteristics can be provided.

Further, according to the present invention, as described above, it is possible to lower the temperature of the mold used, and it is not necessary to provide any special means for eliminating the warpage of the panel. There is an advantage that the shape of the panel to be formed can be simplified. Further, since the cooling time for heat setting and taking out can be shortened, the occupation time of the bottle in the mold is shortened, and the advantage that the polyester bottle can be manufactured with high productivity is also achieved.

[Bottle] In FIG. 1 showing a preferred example of the bottle of the present invention, this heat-set biaxially stretched bottle 1 has an unstretched mouth and neck (neck) 2, a frustoconical shoulder 3, and a substantially truncated conical shoulder 3. It consists of a cylindrical body 4 and a closed bottom 5. In this specific example, the trunk 4 is composed of an upper label 6 and a lower trunk 7, and a waist 8 narrowed to a small diameter exists between the two.

The lower body 7 has a pillar-shaped projection 9 having a relatively large diameter and a short circumference and a panel (mirror) section 10 having a relatively small diameter and a long circumference. A large number of them are provided alternately in the circumferential direction via the connecting portions 11. The pillar-shaped projection 9 extends in the bottle axis direction (height direction), and therefore, the panel section 10 has a substantially rectangular shape with long corners rounded in the bottle axis direction partitioned by the pillar-shaped projection 9. are doing. The panel portion 10 is capable of expanding (projecting) radially outward due to an increase in the internal pressure and contracting (recessing) inward due to a decrease in the internal pressure, thereby having a function of alleviating a change in the internal pressure. I have.

In the heat-set stretched polyester bottle of the present invention, the thickness of the body portion should preferably be in the range of 0.20 to 1.00 mm, particularly 0.25 to 0.80 mm, while the dimensions of the panel portion are Although it varies depending on the size, it is generally desirable that the circumferential dimension is in the range of 10 to 50 mm and the axial (height) dimension is in the range of 40 to 160 mm. Further, it is desirable that the step between the pillar-shaped convex portion having a large diameter and the panel portion having a small diameter, that is, the difference in diameter is in the range of 1 to 8 mm.

FIG. 2 shows another preferred example of the bottle of the present invention.
In this heat-set biaxially stretched bottle 1, the shoulder portion 3 has a truncated pyramid shape, and the cross section of the body portion 4 has a substantially square or rectangular hollow prism shape. The body 4 is provided with an upper part 6a.
And a lower portion 7a, and a narrowed waist portion 8 also exists between the two.

Each of the upper torso 6a and the lower torso 7a
A pillar-shaped protrusion 9 having a small area is provided at one corner portion, and a substantially square or rectangular panel (mirror) portion 10 having a large area is provided between the pillar-shaped protrusions.

The internal volume of these bottles is 180 to 50
It is generally in the range of 00 ml.

In the present invention, the thermoplastic polyester constituting the bottle may be a thermoplastic polyester mainly composed of ethylene terephthalate units, for example, polyethylene terephthalate (PET) or a small amount of other glycols such as hexahydroxyrylene glycol as a glycol component. So-called modified PET or the like containing a small amount of another dibasic acid component such as isophthalic acid or hexahydroterephthalic acid as the dibasic acid component is used. These polyesters can be used alone or in the form of a blend with other resins such as a small amount of nylons, polycarbonate or polyarylate, or in the form of a multilayer structure, as long as the nature thereof is not impaired.

The thermoplastic polyester used has an intrinsic viscosity (η) of at least 0.65 dl / g, especially from 0.70 to 0.5 dl / g.
It is desirable that the content is in the range of 90 dl / g and the content of the diethylene glycol unit is 1.60% by weight or less, particularly 1.50% by weight or less.

In the bottle of the present invention, the entire body 4 is oriented and thermally crystallized by biaxial stretching and heat setting, but the panel portion 10 accounts for 25% or more and other peripheral portions, for example, pillar-shaped convex portions. It has a crystallinity smaller than the crystallinity of No. 9.

The degree of crystallinity in the present specification is the degree of crystallinity determined by the density method, which is published on November 20, 1984 by Kyoritsu Shuppan Co., Ltd., “Polymer Experimental Studies Vol. 17, Polymer Fixed Structure II”. As described on page 305, the formula

(Equation 1) Where ρ is the density of the sample measured in the density gradient tube (g / cm
³ , 25 ° C.), ρ _a is the density of completely amorphous, generally 1.335 g / cm ³ in PET, ρ _c is the density of perfect crystals, generally 1.455 g / cm ³ of PET, and X _cv
Represents the degree of crystallinity (%).

The difference (Co-Cp) between the crystallinity (Co) around the panel portion and the crystallinity (Cp) at the panel portion is preferably 3% or more, particularly preferably 4 to 7%. That is, if the difference in crystallinity (Co-Cp) is smaller than the above range, it becomes difficult to prevent the panel portion from warping, and the periphery of the panel portion, particularly the pillar portion, is thermally deformed. Tend to. More specifically, the crystallinity (Cp) of the panel section 10 is 25 to 33%, particularly 28 to 31%.
The crystallinity (Co) around the panel portion is 30 to 40.
%, Particularly 34 to 38%, is preferable in order to prevent the panel portion from warping while preventing the peripheral portion such as the pillar portion from being thermally deformed.

[Manufacturing Method] In the present invention, a preform heated to a molding temperature, for example, a temperature of 95 ° C. to 115 ° C., is heated to 12 ° C.
In a mold maintained at 0 ° C. or higher, and the temperature of the mold corresponding to the panel is adjusted to a temperature equal to or higher than the glass transition point (Tg) of polyester and lower than the temperature of the mold excluding the mold corresponding to the panel. A bottle is produced by axial stretching blow molding.

In the present invention, for the purpose of adjusting the temperature of the panel-corresponding portion of the mold to the above-mentioned temperature range, a nest for regulating the outer surface of the panel portion of the bottle and a mold body for regulating the outer surface other than the panel portion are used. While adjusting the nest independently of the mold body,
It is preferred to carry out stretch blow molding of the preform.

Further, the mold body has a pillar forming surface and a nest support seat alternately arranged on the inner surface in the circumferential direction, while the panel forming nest is provided on the support seat by the pillar forming surface. It is better to be provided so as to protrude inward. In the nest, a heat medium passage for temperature control is provided,
By passing the heat medium through this passage, the heat setting temperature of the panel section can be controlled within a desired range. Further, by interposing a heat insulating material between the nest for panel formation and the nest support seat or providing a space for heat insulation, it is easy to provide the above-described temperature distribution on the outer surface of the mold.

In the manufacturing method of the present invention, the temperature (Tp) of the portion corresponding to the panel of the mold is at least 20 ° C. lower than the temperature (To) of the mold portion excluding the portion corresponding to the panel, preferably 30 to 50 ° C. It is preferable to adjust the temperature to the temperature, whereby it is possible to form the crystallinity distribution in the above-described range on the heat-fixed bottle panel portion and its peripheral portion.

The main part of the mold (cavity mold) for biaxial stretching blow and heat fixing used in the present invention is shown by a line A in the bottle of FIG.
In FIG. 3, which is a cross section corresponding to FIG.
Numeral 0 is openable and closable on a parting surface (not shown), and comprises a mold body 21 and a panel forming nest 22 which is circumferentially distributed on the inner surface side. The lower torso forming surface 23 includes a panel forming surface 24 and a pillar forming surface 25 alternately arranged in the circumferential direction. In the present invention, the mold body 21 can be maintained at a predetermined temperature by providing a heating heater (not shown) inside.

In FIG. 3, the lower body forming surface 23 is formed.
Only shown, but in connection with the bottle structure of FIG.
Inside the cavity mold 20, a surface for molding a lower part of the mouth and neck, a surface for molding a shoulder, a surface for molding a label, and a surface for molding a waist are respectively formed.
It should be understood that at one end (lower end in the figure) of the 0 there is an opening for the bottom mold insertion through which a bottom mold with a bottoming dome can enter and exit. is there. Also, at the other end (the upper end in the figure) of the cavity mold 20, there is an opening for accommodating a portion close to the mouth of the preform (not shown), and the core mold ( It should also be understood that the preform supported by the not shown) is adapted to be mounted in a cavity mold.

The panel forming nest 22 is mounted in a nest supporting seat 26 of the mold body, and the nest has a mechanism for controlling the temperature. FIG. 4 is a side view (A) and an external view (B) of the nest 22 for forming a panel. Inside the nest 22, a passage 30 for a heat medium formed of a thermally conductive pipe such as copper is provided. A heat medium inlet 31 and a heat medium outlet 32 are formed. By passing a medium such as water through the passage 30, the nest 22 can be adjusted to the above-mentioned predetermined temperature. A heat insulating material 33 is attached to the outer surface of the panel forming nest 22 with a fastener 34 so as to block heat conduction between the mold body 21 and the nest 22.

The panel forming surface 24 of the insert 22 may be a flat surface in the vertical direction, or may be a surface whose central portion is slightly bulged outward in the vertical direction. As shown in FIG. 4 (A), if the shape is warped outward,
This is preferable because the panel surface of the bottle is less likely to be taut. The amount of warpage on the panel forming surface varies depending on the size of the panel surface, but is generally preferably in the range of 0.5 to 1.0 mm in the radial direction.

According to the production method of the present invention, a preheated thermoplastic polyester preform is mounted in the mold, and the preform is expanded and stretched in the circumferential direction.
The bottle is stretched and stretched in the axial direction, and then the bottle is held in a mold for heat setting.

The bottomed preform used for the stretch blow molding can be prepared by any method known per se, for example, injection molding,
It is manufactured by a pipe extrusion method or the like. In the former method, molten polyester is injected, and a preform having a bottom and a neck corresponding to a final bottle is produced in an amorphous state.
In the latter method, an extruded amorphous pipe is cut, a mouth and a neck are formed at one end by compression molding, and the other end is closed to form a bottomed preform. In general, it is preferable to manufacture by an injection molding method. Injection conditions and the like are not particularly limited, but generally, a bottomed preform can be molded at an injection temperature of 260 to 300 ° C. and an injection pressure of 30 to 60 kg / cm ² .

In order to impart heat resistance and rigidity to the neck of the preform thus obtained, the mouth and neck having a screw portion, a fitting portion, a support ring, etc. may be crystallized by heat treatment and whitened in the preform stage. On the other hand, after the completion of the biaxial stretching blow described below, the bottle and neck of the unstretched portion may be crystallized and whitened after completion of bottle molding.

In the present invention, the preform having a bottom is preheated to a molding temperature, for example, a temperature of 95 to 115 ° C., and the preheated preform is biaxially stretch blow-molded in a mold shown in FIG. I do. Mold surface temperature (To)
Is 120 ° C. or higher, but is more preferably maintained at a temperature of 130 to 140 ° C. When the heating temperature is lower than the above range, it is not sufficient to remove the strain due to stretching, the heat resistance is poor, and it is difficult to increase the crystallinity as in the present invention. On the other hand, if the temperature is too high, the impact resistance tends to decrease and the productivity tends to deteriorate. On the other hand, the temperature of the nesting surface (Tp)
The temperature is at least 20 ° C., preferably 40 ° C. lower than the temperature of the mold body surface, and specifically, it is preferably in the temperature range of 90 to 100 ° C.

According to the present invention, a thermoplastic polyester preform preheated to the above temperature is mounted in a blow mold maintained at the above temperature, and the preform is expanded and stretched in the circumferential direction. Pull and stretch in the axial direction. In the stretching operation, generally, a pressurized fluid is blown into the preform, and the stretching in the axial direction and the expansion in the circumferential direction are performed by a stretching rod. The stretching speed in the initial stage of the stretching may be high. Further, prior to blowing by blowing high-pressure gas, pre-blowing can be performed with a fluid having a low pressure. In the present invention, as the pressurizing fluid, unheated air or an inert gas, or heated air or an inert gas may be used, but when a heated fluid is used, the time for heat fixing is reduced. The advantage is that

The pressure of the pressurized fluid used varies depending on the capacity of the final bottle and the thickness of the preform. Generally, the initial pressure of the gas used is at least 25 kg / cm ² , especially within the range of 30 to 40 kg / cm ² . Is preferred. Also, the temperature of the fluid is preferably in the range of 20 to 250 ° C.

The stretching ratio in the final bottle is suitably 5 to 20 times, particularly 7 to 15 times, in area ratio, while the linear stretching ratio in the axial direction is 1.2 to 4 times, especially 1.5 to 3 times.
And the drawing ratio in the circumferential direction is preferably 2 to 7 times, particularly 2.5 to 5 times.

The thermoplastic polyester on the wall of the stretch-blown preform comes into contact with the heated inner surface of the mold, and heat setting (heat setting) is started. The heat treatment time varies depending on the thickness and temperature of the blow molded body,
This heat setting brings about the above-mentioned crystallinity, and generally, the order of 0.5 to 10 seconds, particularly 1 to 5 seconds is appropriate.

After the completion of the heat setting, the pressurized fluid trapped in the molding bottle in the blow mold is released outside the bottle, and the bottle can be cooled by introducing cold air into the bottle. In the present invention, since the heat setting temperature of the panel portion is set low, the advantage that the time required for cooling can be shortened is achieved.

Examples of the cooling fluid include various cooled gases such as nitrogen, air and carbon dioxide at −40 ° C. to room temperature, as well as chemically inert liquefied gases such as liquefied nitrogen gas and liquefied carbon dioxide gas. Also, liquefied trichlorofluoromethane gas, liquefied dichlorodifluoromethane gas, other liquefied aliphatic hydrocarbon gases and the like are used. This cooling fluid includes
A liquid mist having a large heat of vaporization such as water can coexist. By using the cooling fluid described above, a significantly higher cooling rate can be obtained. However,
ADVANTAGE OF THE INVENTION According to this invention, even if it uses the air of room temperature, there exists an advantage that sufficient cooling is performed in a short time.

[0050]

The present invention is further described in the following examples.

Example 1 Intrinsic viscosity (IV) was 0.7
8 dl / g of polyethylene terephthalate was injection-molded to obtain a preform having a diameter of 28 mm and a weight of 32 g, and the mouth and neck of the preform were heated and thermally crystallized. Using this preform and the cavity mold shown in FIGS. 3 and 4, a bottle having the shape and structure shown in FIG. 1 was manufactured. The dimensions of the bottle were set as follows. Inner volume: 540 ml (full capacity) Bottle height: 209 mm Maximum diameter of the lower body: 69 mm Height of the lower body: 186 mm Circumferential dimensions of the panel: 31 mm Panel height: 86 mm Circumferential of the pillar Dimensions: 69mm Thickness of lower torso: 300-500μm Maximum step between panel and pillar: 4.5mm The surface temperature of the mold body of the cavity mold is set to 130 ° C, the nesting surface temperature for panel formation is set to 90 ° C In this mold,
The preform preheated to 105 ° C. was mounted, blown with pressurized air (35 kg / cm ² gauge) at room temperature, expanded and stretched, and stretched and stretched with a stretching rod. The circumferential stretching ratio was set to 3.3 times at the maximum, and the axial stretching ratio was set to 3.5 times. Heat setting was performed with the bottle holding time in the mold after the start of blow stretching at 1.5 seconds, and then room temperature air was circulated in the bottle, and cooling was completed in 0.5 seconds. The mold was opened, and the bottle taken out was further cooled in the air to obtain a product. Further, the surface of the mold insert after the production of 50,000 bottles was observed, but no stain was generated due to oligomer precipitation.

With respect to this bottle, the crystallinity of the panel portion and the crystallinity of the other body portion (including the pillar portion) were measured by changing the measurement position from the neck ring. The result is shown in FIG. In FIG. 5, the symbol ○ indicates the crystallinity of the panel portion, and the symbol ● indicates the crystallinity of the body other than the panel portion. According to this result, it can be seen that the crystallinity of the panel portion is suppressed to be considerably lower than that of the other body portions.

Next, the bottle produced by the above method was filled with hot water (temperature 87 ° C.), left at this temperature for 5 minutes, and sprayed with hot water 75 ° C. to perform pastelization. Then, after cooling to room temperature by spraying cold water, the vertical cross-sectional shape of the panel portion was measured. The obtained result is shown in FIG.
Shown in The panel portion was flat, and no warpage was observed.

[Example 2] The bottle of Example 1 was left in the air and filled with hot water in the same manner as in Example 1 for a bottle having a moisture absorption of 5000 ppm per polyester, and after cooling, the bottle was placed in the vertical direction. Was measured.
The obtained result is shown in FIG. The panel portion was flat, and no warpage was observed.

Comparative Example 1 An unheated, biaxially stretched blow-molded bottle was prepared in the same manner as in Example 1 except that the temperatures of the mold body and the nest for forming the panel were lower than the crystallization temperature. Was manufactured. With respect to this bottle, the crystallinity of the panel portion and the crystallinity of the other body portion (including the pillar portion) were measured by changing the measurement position from the neck ring. The result is shown in FIG. In FIG. 5, the symbol ◇ indicates the crystallinity of the panel portion, and the symbol ◆ indicates the crystallinity of the body portion other than the panel portion. According to this result, the crystallinity of the panel portion was lower than 25%. As a result of filling the bottle with hot water in the same manner as in Example 1,
Not only the panel but also the entire bottle shrank significantly. This is presumably because the heat setting (heat setting) by the mold was not performed, and the molding strain in the biaxial stretch blow molding was not sufficiently removed.

Comparative Example 2 A heat-set biaxially stretch blow-molded bottle was produced in the same manner as in Example 1, except that the temperature of the mold body and the nest for forming the panel was set to 120 ° C. . With respect to this bottle, the crystallinity of the panel portion and the crystallinity of the other body portion (including the pillar portion) were measured by changing the measurement position from the neck ring. The result is shown in FIG. In FIG. 5, the symbol □ indicates the crystallinity of the panel portion, and the symbol ■ indicates the crystallinity of the body portion other than the panel portion. According to this result, the crystallinity of the panel portion was almost the same as that of the body portion. After filling the bottle with hot water in exactly the same manner as in Example 1, the vertical cross-sectional shape of the panel portion was measured. The obtained result is shown in FIG. Warpage was observed in the panel portion, and the amount of warpage was 1.61 mm.

[Comparative Example 3] The bottle of Comparative Example 2 was left in the air and filled with hot water in the same manner as in Example 1 for a bottle whose water content was absorbed by 5000 ppm per polyester, and then cooled. Was measured.
The obtained result is shown in FIG. Warpage was observed in the panel portion, and the amount of warpage was 2.04 mm.

Comparative Example 4 A heat-set biaxially stretch blow-molded bottle was manufactured in the same manner as in Example 1, except that the temperature of the mold body and the nest for forming the panel was set to 150 ° C. . With respect to this bottle, the crystallinity of the panel portion and the crystallinity of the other body portion (including the pillar portion) were measured by changing the measurement position from the neck ring. The result is shown in FIG. In FIG. 5, symbol △ indicates the crystallinity of the panel portion, and symbol ▲ indicates the crystallinity of the body other than the panel portion. According to this result, the crystallinity of the panel portion was almost the same as that of the other body portion. After filling the bottle with hot water in exactly the same manner as in Example 1, the vertical cross-sectional shape of the panel portion was measured. The obtained result is shown in FIG. Warpage was observed in the panel portion, and the amount of warpage was 1.07 mm.

[Comparative Example 5] The bottle of Comparative Example 4 was left in the air and filled with hot water in the same manner as in Example 1 for a bottle having a moisture content of 5000 ppm per polyester. Was measured.
The obtained result is shown in FIG. The panel portion was warped, and the warpage was 1.00 mm.

[0060]

According to the present invention, according to the present invention, the preform heated to the molding temperature is maintained at a temperature of the mold portion other than the panel corresponding portion at 120 ° C. or more, and the panel corresponding portion of the mold is formed of polyester. By performing biaxial stretch blow molding in a mold adjusted to a temperature equal to or higher than the glass transition point (Tg) and lower than the temperature of the mold portion excluding the portion corresponding to the panel, the panel portion is equal to or greater than 25% and its periphery. Thus, a heat-set biaxially stretched polyester bottle having a low degree of crystallinity as compared with the crystallinity of the part is obtained. In this bottle, the warpage of the panel portion when heat sterilization such as hot filling is performed is effectively prevented, and the advantage of excellent appearance characteristics is achieved.
Also, by lowering the heat setting temperature of the panel,
Occurrence of mold contamination due to oligomer precipitation is prevented, and as a result, appearance properties such as gloss and transparency of the bottle can be further improved. Furthermore, the temperature of the mold used can be reduced, and the shape of the panel formed on the bottle can be simplified, and the occupation time in the mold can be shortened, so that the polyester bottle can be manufactured with high productivity.

[Brief description of the drawings]

FIG. 1 is a side view showing a preferred example of a bottle of the present invention.

FIG. 2 is a side view showing another preferred example of the bottle of the present invention.

FIG. 3 is a partial sectional view showing a main part of a mold for stretch blow and heat fixing used in the present invention.

FIG. 4 is a side view (A) and an external view (B) of a panel forming nest used in the mold of FIG. 3;

FIG. 5 is a graph showing the crystallinity of each part of the bottles of Examples and Comparative Examples.

FIG. 6 is a view showing the shape and the amount of warpage of the panel portion of the bottles of the example and the comparative example.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65D 1/02 B29K 67:00 // B29K 67:00 B29L 22:00 B29L 22:00 B65D 1/00 C F-term (reference) 3E033 AA01 BA17 CA07 DA03 DB01 DD03 FA03 GA02 4F202 AA24 AF01 AG05 AG07 AG22 AG26 AH55 AR06 AR20 CA15 CB01 CK11 CL01 CN01 4F208 AA24 AF01 AG05 AG07 AG22 AG26 AH55 AR06 AR20 LA04 LA07 LB01 L08 L08 LH LGH LN21

Claims (4)

[Claims] 1. A heat-set biaxially stretched polyester bottle having a panel portion on a body portion, wherein the crystallinity of the panel portion is 2
A biaxially stretched polyester bottle which is at least 5% and lower than the crystallinity of the peripheral portion. 2. The bottle according to claim 1, wherein the difference between the crystallinity at the periphery of the panel portion and the crystallinity at the panel portion is 3% or more. 3. A method for producing a heat-set biaxially stretched polyester bottle having a panel portion on a body portion, wherein a preform heated to a molding temperature is heated to a temperature of 120 ° C. or higher except for a portion corresponding to a panel. Biaxial stretching blow in a mold whose temperature is adjusted to a temperature equal to or higher than the glass transition point (Tg) of the polyester and lower than the temperature of the mold portion excluding the panel corresponding portion. A method for producing a biaxially stretched polyester bottle, comprising molding. 4. The method according to claim 3, wherein the temperature of the panel-corresponding portion of the mold is adjusted to a temperature at least 20 ° C. lower than the temperature of the mold portion excluding the panel-corresponding portion.