JP5515670B2 - Polyester resin container excellent in formability and method for producing the same - Google Patents

Description

  The present invention relates to a polyester resin container in which a concave portion for grasping a container is formed in a body portion, and more specifically, a desired shape is shaped with good reproducibility, and occurs with the formation of a concave portion. The present invention relates to a deformed polyester resin container with reduced molding distortion and excellent appearance characteristics, and a method for producing the same.

2. Description of the Related Art Conventionally, containers such as bottles formed by biaxial stretching blow molding a preform made of a polyester resin such as polyethylene terephthalate have been widely used for beverages, seasonings, edible oils, detergents and the like.
In such a polyester resin container, when it is used for the purpose of filling the contents by heat sterilization, since it is required to have heat resistance against heat shrinkage, it is molded by so-called two-stage blow molding. It is known (Patent Document 1).
Among such polyester resin containers, those having a relatively large capacity have been proposed in which the container body is recessed to form a flat area for gripping in order to facilitate carrying (patents) Reference 2).

JP 62-30018 JP JP 2002-283441 A

In the above-described two-stage blow molding, the internal residual stress (residual strain) is relaxed by heat shrinking after the primary blow molding and the heat resistance is improved, but the heat is removed by removing the internal stress by heating. Since the crystallization has progressed and the secondary molded product has become hard, the shapeability in the secondary blow molding process is reduced, so the desired shape cannot be shaped into the container with good reproducibility, and the appearance characteristics I was not satisfied with it. Further, there is a problem that even if the heat resistance is excellent due to the high crystallinity of the final molded product, it becomes inferior in impact resistance.
In addition, in the container in which the flat area for gripping described in Patent Document 2 is formed, heat treatment is performed at a temperature of 110 to 250 ° C. in order to reduce residual stress. In this case, it is molded by pressing a mold. For this reason, the degree of crystallinity is still high, the shapeability and the impact resistance are inferior, and the container described in Patent Document 2 is overstretched because the entire body is crushed. It is easy to cause whitening or bursting.

Accordingly, an object of the present invention is to provide a polyester resin container in which a shape having a concave portion in a body portion is shaped with good reproducibility and excellent in appearance characteristics.
Another object of the present invention is to provide a polyester resin container having a recess in the body and excellent impact resistance, in which molding strain is effectively reduced without increasing the crystallinity.
Still another object of the present invention is to provide a method for producing a polyester resin container having a concave portion in a body portion, which can form a desired shape with good reproducibility without causing molding distortion. .

According to the present invention, it is a polyester resin container having at least a mouth portion, a body portion, and a bottom portion, and the body portion is formed with a recessed portion recessed inward of the container, and the deepest portion of the recessed portion is formed. The ratio Dmax / Wmax of the depth Dmax and the maximum width Wmax of the container body perpendicular to the depth direction of the recess is 0.36 to 0.57 , and the crystallinity in the recess is 25 to 36 %. The ratio tmin / tmax between the thickness tmin of the thinnest part and the thickest part tmax on the circumference of the body part at the deepest part of the recess is 0.60 to 0.77. A featured polyester resin container is provided.

In the polyester resin container of the present invention,
1 . On the circumference of the body portion at the position of the deepest portion of the recessed portion, the ratio Hmin / Hmax circumferential orientation value Hmax of the circumferential orientation value Hmin and the thickest portion of the thinnest portion is at 1.20 to 2.00 about,
2 . The primary molding is performed by first blowing a preform made of polyester resin to form a primary molded product, and then exhausting and depressurizing from the inside of the primary molded product while keeping the body of the primary molded product at a high temperature without applying heat from the outside. The molded product was shrunk to form a secondary molded product, and shaped by pressing the secondary molded product with a mold having a convex portion for forming a concave portion in the container body, and then shaped The secondary molded product is molded by secondary blowing in the mold,
Is preferred.
In the present invention, the orientation value is determined by laser Raman spectroscopy, and methods for measuring the crystallinity, thickness, and orientation value will be described later in Examples.

The polyester resin container of the present invention has a deep recess in the body and is easy to grip, and even if deep recesses are formed and there are parts with different processing amounts, the wall thickness is uniform and buckles. It is difficult and excellent in mechanical strength, and the occurrence of molding distortion is suppressed.
Further, the polyester resin container of the present invention is soft because it has a relatively low crystallinity, and therefore can be easily crushed, folded, or folded, and the amount of waste can be reduced when the container is discarded. It can be reduced and has excellent impact resistance.
Furthermore, the manufacturing method of the polyester resin container of the present invention can be molded with a single mold without using a special mold, even if the container is a flat container with extreme irregularities formed in the body part, And since it shape | molds without raising a crystallinity also in a shaping | molding process, it is excellent in the shapeability and can shape a desired container shape with sufficient reproducibility.

It is a front view of an example of the polyester resin container of the present invention. It is a side view of the polyester resin container shown in FIG. FIG. 2 is an XX cut end view of the polyester resin container shown in FIG. 1. It is a figure which shows the state before the primary blow molding process of the container made from the polyester resin of this invention. It is a figure which shows the primary blow molding process of the polyester resin containers of this invention. It is a figure which shows the shrinkage | contraction process of the container made from the polyester resin of this invention. It is a figure which shows the recessed part formation process of the polyester resin containers of this invention. It is a figure which shows the secondary blow molding process of the polyester resin containers of this invention. It is a figure which shows the state which takes out the polyester resin container of this invention from a metal mold | die.

  In FIGS. 1 to 3 showing an example of the polyester resin container of the present invention, the polyester resin container 20 of the present invention roughly comprises a mouth portion 21, a shoulder portion 22, a trunk portion 23 and a bottom portion 24. 3, the container 20 has a cross-sectional shape from the shoulder 22 to the bottom 24, and the width of the front surface of the container (the front surface having the maximum width and the surface where the recess is formed). It has a flat shape with a side width W2 shorter than W1. A concave portion 25 that is recessed inward of the container is formed in the body portion 23 in front of the container. In the specific example shown in the figure, the front shape of the recess 25 has a spindle shape in which the width w of the recess decreases as it goes to the upper end 25a and the lower end 25b in the axial direction of the recess 25. Absent. The depth d of the concave portion 25 becomes shallower toward the upper end 25a and the lower end 25b of the concave portion 25, and the vertical center (X-X line) of the concave portion 25 is located at a portion where the width W1 of the container becomes the maximum width Wmax. It is formed deepest in this part.

In the present invention, as shown in FIGS. 1 to 3, the depth Dmax of the deepest portion 25 c of the concave portion 25 formed in the trunk portion 23 and the trunk portion orthogonal to the depth direction of the deepest portion 25 c of the concave portion 25 and the concave portion 25. The ratio Dmax / Wmax of the maximum width Wmax (W1 in FIG. 3) is in the range of 0.20 to 0.70, especially 0.36 to 0.57, and the width on the wide side of the horizontal section of the container body The first important feature is that a deep recess is formed. When Dmax / Wmax is smaller than the above range, it is not necessary to form a recess prior to the secondary blow molding step, and the function as a gripping recess cannot be achieved. On the other hand, when the value of Dmax / Wmax is larger than the above range, the processing amount becomes too large, and there is a possibility of whitening or bursting due to excessive stretching, which is not preferable.
In the specific example shown in the figure, Wmax and Dmax are at the same height position, but Wmax and Dmax may be at different height positions. In this case, the direction perpendicular to the Dmax direction is relative to Dmax. The maximum widths Wmax of the body parts of these are compared.

As described above, since the polyester resin container of the present invention is stretched in a well-balanced manner even in a concave portion with a large processing amount, the ratio tmin / tmax of the thickness tmin of the thinnest portion and the thickness tmax of the thickest portion is: The thickness is in the range of 0.50 to 1.00, particularly 0.60 to 0.77, and the thickness is uniform. Therefore, as is clear from the results of Examples described later, it is clear that the material is not easily buckled and has excellent mechanical strength.
The ratio Hmin / Hmax between the circumferential direction orientation value Hmin of the thinnest part and the circumferential direction orientation value Hmax of the thickest part on the circumference of the body part at the position of the deepest part of the recess (25c in FIGS. 2 and 3). 1.20 to 2.00, particularly 1.43 to 1.82, and there is not much difference in the degree of orientation between the thinnest part and the thickest part. Therefore, as will be apparent from the results of the examples described later, it has an orientation ratio substantially the same as that of a conventional heat-resistant polyester resin container (Comparative Example 1) by two-stage blow molding, without causing an overstretched portion. It is clear that both parts are stretched relatively evenly. As a result, after the heat of about the hot water rinse (about 20 seconds of rinsing with about 65 ° C. warm water) is applied, local heat shrinkage does not occur in the concave portion 25 and the concave portion is not distorted unevenly.
In addition, in the container formed in the Example mentioned later, the site | part of A in FIG. 3 is the thickest part, and the site | part of B is the thinnest part.

  In the present invention, the second important feature is that the degree of crystallinity is in the range of 20 to 40%, particularly in the range of 25 to 36%, in the recesses with the largest processing amount and severe processing. Therefore, it is soft, can be easily crushed, folded or folded, and has excellent impact resistance.

  In the method for producing a polyester resin container of the present invention, after the primary blow molding, the primary molded product is contracted by exhausting and depressurizing from the inside of the primary molded product, thereby reducing the molding distortion without promoting crystallization. Therefore, a soft secondary molded product with low crystallinity can be obtained. This soft secondary molded product has good followability to the molding surface of the mold by pressing with a mold having a convex portion, and it becomes possible to shape a desired shape with good reproducibility. is there.

(preform)
As the thermoplastic polyester used in the polyester resin container of the present invention, an ethylene terephthalate thermoplastic polyester can be particularly preferably used.
The ethylene terephthalate-based thermoplastic polyester used in the present invention occupies most of the ester repeating units, generally 70 mol% or more, particularly 80 mol% or more of ethylene terephthalate units, and has a glass transition point (Tg) of 50 to 90. Thermoplastic polyesters having a melting point (Tm) of 200 to 275 ° C., particularly 220 to 270 ° C., at 55 ° C., in particular 55 to 80 ° C., are preferred.

Homopolyethylene terephthalate is preferred in terms of heat resistance and mechanical strength, but a copolyester containing a small amount of ester units other than ethylene terephthalate units can also be used.
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, dodecanedioic acid, etc. 1 type or combination of 2 or more types of diol components other than ethylene glycol include propylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexylene glycol, cyclohexane di 1 type, or 2 or more types, such as methanol and the ethylene oxide adduct of bisphenol A, are mentioned.
The ethylene terephthalate-based thermoplastic polyester to be used should have at least a molecular weight sufficient to form a film, and an injection grade or extrusion grade is used depending on the application. The intrinsic viscosity (IV) is generally in the range of 0.6 to 1.4 dL / g, particularly 0.63 to 1.3 dL / g.

In the polyester resin container of the present invention, a multi-layered preform can be used in combination with another thermoplastic resin in addition to the above-described single-layer bottle made of a single-layered polyester resin preform.
Other than the above polyester resin, recycled polyester (PCR (resin that has been used bottle regenerated), SCR (resin generated in a production factory), or a mixture thereof) can also be used.

As the preform used in the present invention, a conventionally known bottomed preform comprising a mouth portion, a trunk portion and a closed bottom portion can be used. The mouth portion is provided with a lid fastening mechanism such as a ring-shaped protrusion or a screw according to the structure of the lid to be used, such as a cap or a crown.
The polyester resin can be molded into a preform by a conventionally known method, and can be molded by injection molding or compression molding.
The mouth portion of the preform is desirably thermally crystallized as necessary, and can be performed by selectively heating these portions by means known per se. Since thermal crystallization of polyester or the like occurs remarkably at a specific crystallization temperature, generally a corresponding portion of the preform may be heated to the crystallization temperature. Heating can be performed by infrared heating, dielectric heating, or the like. In general, it is preferable to perform selective heating by blocking a body portion to be stretched from a heat source with a heat insulating material.
The above thermal crystallization may be performed simultaneously with the preheating to the stretching temperature of the preform or may be performed separately. The mouth thermal crystallization can be performed by heating the preform mouth to a temperature of generally 140 to 220 ° C., particularly 160 to 210 ° C. in a state where it is thermally insulated from the other portions. The crystallinity of the preform mouth is preferably 25% or more.
In addition, if the sterilization conditions after filling the contents are about the same as or lower than those in Examples described later, the mouth portion does not necessarily have to be thermally crystallized.

(Production method)
The manufacturing method of the container made from the polyester resin of this invention is demonstrated along an accompanying drawing.
Prior to being subjected to the primary blow molding process, the preform 10 is supported on the mandrel 5 so that the opening side is positioned below, and is placed between the cavity molds 3a and 3b in the mold open state. (See FIG. 4).

[Primary blow molding process]
In the primary blow molding process, the preform 10 is heated so that the body portion has a stretchable temperature equal to or higher than the glass transition point. However, the preform 10 is in a state immediately after the preform 10 is molded by injection molding or compression molding. If so, the temperature may be the above-described residual heat during molding. In such a case, the preform 10 can be used as it is without being heated in the primary blow molding process.
The preform 10 arranged between the cavity molds 3a and 3b is fixed at the mold closing position by the fixed molds 2a and 2b on the opening side. At the same time, or before and after this, the base mold 4 moves down to the mold closing position, and the press rod 6 provided through the inside of the base mold 4 so as to be movable up and down is moved downward. The rod 6 is placed on standby at a position where the tip of the rod 6 approaches or contacts the preform 10 (see FIG. 4).

  Next, as shown in FIG. 5, while keeping the cavity molds 3a and 3b in the open state, the stretch rod 7 penetrating the inside of the mandrel 5 and being vertically movable is moved up, Blow molding is started by blowing blow air through the inside of the mandrel 5 into the preform 10 via a blow air supply source and a valve mechanism (not shown). As a result, the preform 10 is stretched to form the primary molded body 11. At this time, by extending the press rod 6 in synchronization with the stretch rod 7 so that the front end side of the preform 10 to be stretched is sandwiched between the press rod 6 and the stretch rod 7, the stretching direction of the preform 10 is increased. It is possible to regulate so as not to shift.

In the specific example shown in the figure, primary blow molding is performed without forming a mold (blow mold), so that the preform 10 is stretched by so-called free blow molding to form the primary molded body 11. Of course, ordinary blow molding using a mold can also be performed.
The size of the primary molded body 11 is such that the body portion of the preform 10 has a length of 1.2 to 5.2 times and a width of 2 to 7 times from the viewpoint of preventing uneven thickness in the primary molded body 11. It is preferable to mold into a size that can be sufficiently stretched.

[Shrinking process]
As shown in FIG. 6, in the shrinking process, the primary molded body 11 is contracted to form the secondary molded body 12 by removing the blow air pressure in the primary molded body 11 obtained in the primary blow molding process. .
That is, the primary molded body 11 immediately after being formed in the primary blow step is usually heat generated by the preform 10 when subjected to blow molding and heat generated by stretching depending on conditions such as stretching speed. Due to the shear heat generation of the plastic resin, a temperature higher than the glass transition point of the polyester resin used is maintained. Under such a high temperature, sufficient internal pressure remains in the primary molded body 11 to keep the shape in balance with the contraction force generated by the residual stress generated when the preform 10 is stretched. The primary compact 11 is depressurized.
In order to depressurize the inside of the primary molded body 11, the inside of the primary molded body 11 that is in a positive pressure state immediately after the primary blow process is released to the atmosphere via a valve mechanism (not shown). It may be connected to forcibly exhaust the interior of the primary molded body 11. At this time, if the pressure is reduced so as to be lower than the pressure in the primary molded body 11 immediately after the blow molding, and contracts to a size that can be accommodated in the product shape portion of the cavity molds 3a and 3b, at that time, the primary The secondary molded body 12 formed by shrinking the molded body 11 can be subjected to the next secondary blow molding process.

In this contraction step, the primary molded body 11 is contracted by depressurizing the inside of the primary molded body 11, so that the primary molded body naturally contracts naturally and becomes the secondary molded body 12. For this reason, it becomes possible to reduce the residual distortion caused by the blow molding generated in the primary molded body 11 and prevent such residual distortion from being handed over to the secondary molded body 12 as it is.
The size of the secondary molded body 12 is preferably such that the circumferential length of the maximum circumferential length portion of the secondary molded body 12 is slightly smaller than the maximum circumferential length of the product shape portion of the cavity molds 3a and 3b. This is preferable because the stretched amount of the secondary molded body 12 in the secondary blow step described later can be reduced and a large amount of new residual strain does not occur. Specifically, the peripheral length of the maximum peripheral length portion of the secondary molded body 12 is preferably 85 to 99% of the maximum peripheral length of the product appearance portion of the cavity molds 3a and 3b.
In the example shown in FIG. 6, an example in which the primary molded body 11 is contracted in the radial direction (width direction) is shown, but the primary molded body 11 may be contracted appropriately in the height direction.

  In the present invention, when the primary molded body 11 is contracted, it is preferable to form the secondary molded body 12 by simply depressurizing the inside of the primary molded body 11 without applying heat from the outside. When contracted by heating from the outside, the degree of crystallinity of the secondary molded body 12 becomes high and the secondary molded body 12 becomes hard, but this is prevented by contracting without applying heat from the outside. In the secondary blow molding process of the next process, the followability to the molding surface when shaping the inner surface shape of the blow molding die 1 becomes good.

[Recess formation step]
Next, the secondary molded body 12 is housed in the blow mold 1 and again subjected to blow molding in that state, thereby shaping the inner shape of the blow mold 1 to form a predetermined container shape. In the present invention, prior to the secondary blow molding, as shown in FIG. 7, the protrusions 30 projecting into the cavity space formed on the inner surfaces of the cavity molds 3 a and 3 b (blow molding mold 1), The secondary molded body 12 is pressed and deformed.
As described above, in the shrinking process, by not applying heat to the primary molded body 11 from the outside, the followability to the molding surface when shaping the inner surface shape of the blow molding die 1 is improved. be able to.

[Secondary blow molding process]
When the mold closing operation is completed and a concave portion is formed in the secondary molded product, the press rod 6 is retracted into the base mold 4 and the secondary molded body 12 is moved through a blow air supply source and a valve mechanism (not shown). Blow air is blown through the inside of the mandrel 5 so that the secondary molded body 12 is brought into close contact with the inner surface of the blow mold 1, and the inner surface shape of the blow mold 1 is shaped to form a final molded product container M. (See FIG. 8).

  Further, when the mold closing operation of the blow mold 1 is performed, it is preferable to seal the inside of the secondary molded body 12. In this way, when the secondary molded body 12 is pressed and deformed, the inside of the secondary molded body 12 is moderately pressurized, and the pressurization and the movement of the cavity molds 3a and 3b are synergistically effective. Thus, the meat of the secondary molded body 12 suitably wraps around the portions other than the projecting portions 30, and the followability to the molding surface becomes better.

  Next, after undergoing post-treatment such as cooling blow, the inside of the container M is evacuated, and then the stretch rod 7 is retracted. Thereafter, the fixed molds 2a and 2b, the cavity molds 3a and 3b, and the base mold 4 are moved to the mold opening position to perform the mold opening of the blow molding mold 1, and then the molded container M is taken out (see FIG. 9). .

  According to the manufacturing method described above, a container having a recessed portion that is deeply recessed in the container body through the steps of the primary blowing step, the shrinking step, the recessed portion forming step, and the secondary blowing step is used as the inner surface of the blow mold 1. It is possible to efficiently mass-produce a polyester resin container having a good shape, good moldability, and a barrel holding recess formed in the barrel.

In the specific example shown in the figure, the container shape is a flat shape having the largest body width at the central portion in the axial direction of the container and narrowing as it goes upward and downward. After passing through the shoulder from the mouth, it may be of a straight line where the diameter of the torso hardly changes, and the cross section is not only elliptical, but also round and rectangular corners are rounded Various changes such as a substantially rectangular shape can be made.
Further, the shape of the recess is not limited to that shown in the figure, and various changes such as a hemispherical shape and a substantially pyramidal shape can be made. In addition, the recesses may be formed not only in the case where they are provided symmetrically at a position orthogonal to the maximum diameter of the body part, but also in a portion having a narrow width.

Example 1
Polyester resin has a glass transition point of about 75 ° C., a melting point of about 250 ° C., an IV of 0.80, and polyethylene terephthalate (PET) (occupying 95% by mole or more of ethylene terephthalate units). A preform having a diameter of 30 mm, a body length of 125 mm, and a body thickness of 3 mm was prepared.
Next, after the preform body is heated to about 100 ° C. in the primary blow molding process, the stretch rate of the stretch rod is about 500 mm / sec, and the air pressure is about 0.1 MPa (gauge pressure) at normal temperature (about 25 ° C) air, and blow-molded to a primary molded body of about 2.0 times in length and about 3.5 times in width.
In this process, stretching in the longitudinal direction is regulated by a stretch rod and a press rod, and the stretching length is also regulated.

Immediately (after about 1 second) after the primary blow molding step, the primary molded body whose internal pressure immediately after the primary blow molding was about 0.1 MPa (gauge pressure) was removed in the contraction step to obtain 0.0 MPa (gauge pressure). And a secondary molded body having a barrel outer diameter φ of about 80 mm and a barrel length of 250 mm to be blow-molded.
Immediately after the shrinking step (after about 1 second), in the recess forming step, the secondary molded body was pressed by a blow molding die (set at a mold temperature of 120 ° C.) to form a recess.
Immediately (after about 1 second) after the recess forming step, the secondary blow molding step is performed by blow molding at an air pressure of 3.0 MPa (gauge pressure), and the pressure is reduced by performing cooling blow at 25 ° C. air. After circulating and cooling the air, the pressure is released and the atmospheric pressure is released, and then the blow molding die is opened and taken out, the concave side maximum barrel width (Wmax) is 71.2 mm, the concave portion depth (Dmax) is 25.6 mm, A container having a height of 280 mm and a maximum width of 103 mm was used.

As a result of measuring the degree of crystallinity of this container, the thickest part of the deepest concave part was 25%, and the concave slope of the thinnest part was 30%.
The crystallinity was obtained by measuring the density ρ [g / cm ³ ] of the test piece cut out from the container body and substituting it into the following equation.
Crystallinity (%) = {ρc · (ρ−ρa)} / {ρ · (ρc−ρa)} × 100
ρc: Crystal density (1.455 g / cm ³ )
ρa: amorphous density (1.335 g / cm ³ )
In measuring the density ρ, a density gradient tube method prepared with an aqueous calcium nitrate solution was used.

As a result of measuring the wall thickness of this container, the deepest thickness portion (tmax) of the deepest concave portion was 0.25 mm, and the concave slope (tmin) which was the thinnest wall portion was 0.15 mm.
A micrometer was used for measuring the wall thickness.
As a result of measuring the orientation value in the circumferential direction of this container, the thickest portion (Hmax) of the deepest concave portion was 1.7, and the concave slope (Hmin) which was the thinnest portion was 3.0.
The orientation value was measured by laser Raman spectroscopy.
A cross section in the circumferential direction of the bottle was cut out to obtain a test piece. The Raman spectrum of the test piece was measured, and the orientation value was calculated from the peak intensity derived from the benzene ring skeleton vibration near 1620 cm ⁻¹ by the following equation.
Orientation value = (Peak intensity at 0 ° polarization of incident laser / peak intensity at 90 ° polarization of incident laser)
The orientation value was measured at an equal distance with respect to the wall thickness of the bottle body at five points, and the average value was taken as the orientation value of the bottle.
Equipment: JASCO / Laser Raman spectrophotometer NRS-1000
The instrument measurement conditions are as follows.
Laser used 532 nm Measurement wavelength range: 1800 to 600 cm ⁻¹
Measurement seconds: 5 sec. Number of integrations: 2

(Example 2)
Molding was performed in the same manner as in Example 1, except that the container-shaped recess depth (Dmax) was changed to 29.6 mm.
As a result of measuring the crystallinity of this container, the thickest portion of the deepest concave portion was 29%, and the slope of the concave portion being the thinnest portion was 33%.
As a result of measuring the wall thickness of this container, the deepest thickness portion (tmax) of the deepest concave portion was 0.23 mm, and the concave slope (tmin) which was the thinnest portion was 0.15 mm.
As a result of measuring the circumferential orientation value of this container, the thickest part (Hmax) of the deepest concave part was 1.7, and the concave slope (Hmin) of the thinnest part was 3.1.

(Example 3)
Molding was performed in the same manner as in Example 1, except that the container-shaped recess depth (Dmax) was changed to 31.6 mm.
As a result of measuring the degree of crystallinity of this container, the thickest part of the deepest concave part was 33%, and the concave slope of the thinnest part was 35%.
As a result of measuring the wall thickness of this container, the deepest thickness portion (tmax) of the deepest concave portion was 0.22 mm, and the concave slope (tmin) which was the thinnest portion was 0.15 mm.
As a result of measuring the circumferential orientation value of this container, the thickest portion (Hmax) of the deepest concave portion was 2.1, and the concave slope (Hmin) which was the thinnest portion was 3.0.

Example 4
Molding was performed in the same manner as in Example 1 except that the recess depth (Dmax) of the container shape was changed to 40.6 mm.
As a result of measuring the degree of crystallinity of this container, the thickest part of the deepest concave part was 34%, and the concave slope of the thinnest part was 36%.
As a result of measuring the thickness of this container, the thickest portion (tmax) of the deepest concave portion was 0.22 mm, and the concave slope (tmin) which was the thinnest portion was 0.17 mm.
As a result of measuring the orientation value in the circumferential direction of this container, the thickest portion (Hmax) of the deepest concave portion was 2.2, and the concave slope (Hmin) being the thinnest portion was 3.3.

(Comparative Example 1)
Polyester resin has a glass transition point of about 75 ° C., a melting point of about 250 ° C., an IV of 0.80, and polyethylene terephthalate (PET) (occupying 95% by mole or more of ethylene terephthalate units). A preform having a diameter of 30 mm, a body length of 125 mm, and a body thickness of 3 mm was prepared. (This is the same preform as in Example 1.)
Next, the preform body is heated to about 100 ° C. in the primary blow molding step, and then stretched at a stretch rod stretching speed of about 500 mm / sec. Blow molding was performed at an air pressure of 3.0 MPa using a draw ratio of 2.0 times in length, 4.0 times in width, and a mold temperature of 120 ° C., and after cooling with cooling blow, air pressure (internal pressure) ) Was taken out of the blow mold and used as a primary intermediate having the same shape as that of the blow mold for the primary intermediate.

After the primary blow molding process, in the shrink oven process, reheating was performed so that the temperature of the primary intermediate was 180 ° C., thereby causing thermal shrinkage due to residual strain of the resin.
Immediately after the shrinking process, in the secondary blow molding process, blow molding is performed on the secondary blow mold set at a mold temperature of 25 ° C. with an air pressure of 3.0 MPa (gauge pressure) (then, cooling blow, release of atmospheric pressure, mold) And a container having a maximum trunk width (Wmax) of 71.2 mm, a recess depth (Dmax) of 25.6 mm, a trunk height of 280 mm, and a maximum trunk width of 103 mm.
As a result of measuring the degree of crystallinity of this container, the thickest portion of the deepest concave portion was 42%, and the concave slope of the thinnest portion was 46%.
As a result of measuring the wall thickness of this container, the deepest thickness portion (tmax) of the deepest concave portion was 0.25 mm, and the concave slope (tmin) which was the thinnest wall portion was 0.15 mm.
As a result of measuring the circumferential orientation value of this container, the thickest portion (Hmax) of the deepest concave portion was 2.4, and the concave slope (Hmin) which was a thin-walled portion was 3.5.

(Comparative Example 2)
Polyester resin has a glass transition point of about 75 ° C., a melting point of about 250 ° C., an IV of 0.80, and polyethylene terephthalate (PET) (occupying 95% by mole or more of ethylene terephthalate units). A preform having a diameter of 30 mm, a body length of 125 mm, and a body thickness of 3 mm was prepared. (This is the same preform as in Example 1.)
Next, in the blow molding process, the preform body is heated to about 100 ° C. and then stretched at a stretch rod stretching speed of about 500 mm / sec. Blow molding at 0.0 MPa (gauge pressure) (afterwards cooling blow, release of atmospheric pressure, mold opening), maximum recess width (Wmax) 71.2 mm, recess depth (Dmax) 17.6 mm, barrel height An attempt was made to form a container having a width of 280 mm and a maximum body width of 103 mm. However, the thinnest part is as thin as 0.1 mm, and it is thin enough to be overstretched, whitening and sinking, and soft enough to buckle when touched lightly, so that it can withstand external factors of transportation and transportation Was not provided. Therefore, since it was not worthy of evaluation as a product at this time, other measurements were omitted.

In the containers of Examples 1 to 4 and Comparative Example 1, the shapeability and volume reduction of the bottle (ease of crushing the container) were examined.
The formability was evaluated by observing the corners of the molded container and evaluating the appearance of the contours by.
For volume reduction, the container after molding was crushed, and the ease of crushing was evaluated by ○ △ ×.
The above is summarized as shown in Table 1.

  In the containers of Examples 1 to 4 and Comparative Example 1, the dimensional ratio, crystallinity, thickness ratio and orientation value ratio (Hmin / Hmax) of the recesses are summarized in Table 2.

In the present invention, since the concave portion for grasping the container is formed with good shapeability in the body portion, it is easy to grasp and can be suitably used for a large-capacity container or the like.
In addition, since the degree of crystallinity is low, it can be easily crushed, folded, folded or folded, and the volume of waste can be reduced. Therefore, it can be suitably used for a disposable container or the like.
Furthermore, since it is excellent in impact resistance and suitable for distribution and carrying, it can be suitably used for beverage containers and the like.

DESCRIPTION OF SYMBOLS 1 Blow mold, 3a, 3b Cavity mold, 10 preform, 11 primary molded body, 12 secondary molded body, 20 polyester resin container, 21 mouth part, 23 trunk | drum, 24 bottom part, 25 recessed part, 30 protrusion part .

Claims (3)

A polyester resin container having at least a mouth part, a body part, and a bottom part, wherein the body part is formed with a recessed part recessed inward of the container, and the depth Dmax of the deepest part of the recessed part and the recessed part The ratio Dmax / Wmax of the maximum width Wmax of the container body perpendicular to the depth direction of the container is 0.36 to 0.57 , and the crystallinity in the recess is in the range of 25 to 36 %. The ratio tmin / tmax between the thickness tmin of the thinnest part and the thickest part tmax on the circumference of the body part at the position of the deepest part is 0.60 to 0.77 . container. The ratio Hmin / Hmax of the circumferential direction orientation value Hmin of the thinnest part and the circumferential direction orientation value Hmax of the thickest part on the circumference of the body part at the position of the deepest part of the recess is 1.20 to 2.00. polyester resin container of a certain claim 1 Symbol placement. The primary molding is performed by first blowing a preform made of polyester resin to form a primary molded product, and then exhausting and depressurizing from the inside of the primary molded product while keeping the body of the primary molded product at a high temperature without applying heat from the outside. The molded product was shrunk to form a secondary molded product, and shaped by pressing the secondary molded product with a mold having a convex portion for forming a concave portion in the container body, and then shaped It claims 1 or 2 Symbol mounting process for producing a polyester resin container of the molding by secondary blow the secondary molded product in the mold.

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