JP2007030893A - Synthetic resin bottle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synthetic resin bottle whose trunk has a shape that inhibits the deformation of the bottom in a retort treatment under temperature of 120-130°C, and which exerts a standing function for use in a retort food to be available for safe use requiring a retort treatment. <P>SOLUTION: The synthetic resin bottle has a ground portion for standing which is formed on the bottom face of the bottom, where bottom face is depressed inwardly to form a bottom-raised portion with a base end formed of the ground portion. When the bottle is subjected to a steam retort treatment under temperatures of 120-130°C, the wall of the trunk can bulge in reversible deformation, which keeps a pressure difference between the interior of the bottle and that of a retort kettle in a range of 0.05 MPa or lower, and more preferably, 0.03 MPa or lower. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a synthetic resin casing used for applications requiring retort processing.

  In recent years, synthetic resin casings such as polyethylene terephthalate (hereinafter referred to as PET) resin casings have been used for foods that require retort treatment. In this case, the retort treatment is performed at 100 ° C. using pressurized heated water or heated steam in the retort kettle with the food filled in the casing at a temperature of about room temperature to 100 ° C. and the mouth tube portion sealed with a cap. Heat sterilization is performed at the above temperature for several tens of minutes.

  And the pressure (internal pressure) in a housing rises by the expansion | swelling of the air of a head space, and the content. Here, when retort processing is performed using pressurized heated water, the bulging deformation of the housing can be suppressed by adjusting the pressure of hot water to balance with the internal pressure. When steam is used, it is necessary to perform heat treatment in the vicinity of the saturated water vapor pressure at that temperature, and cannot be balanced with the internal pressure of the enclosure, and the enclosure is in a pressurized state.

On the other hand, in a pressure-resistant bottle for carbonated drinks, since the standing property of the housing is impaired due to deformation of the bottom due to internal pressure, champagne has a shape in which the bottom of the bottom is recessed inward to prevent the bottom from bulging A casing having a bottom shape or a petaloid type bottom is used.
However, in the above-mentioned retort processing, the processing temperature is higher than the glass transition temperature in a general-purpose resin such as PET, so even if the pressure bottle is used as it is, the bottom portion is deformed in a bulging shape toward the outside of the housing. In other words, so-called “bottom” may occur.

  In addition, the bottom part is greatly deformed and does not cause reversal deformation, and the slight deformation of the bottom part impairs the uprightness, which is one of the most basic functions of the housing, so only the shape of the bottom part including the wall thickness Therefore, it is difficult to reliably control the deformation of the bottom part under severe conditions such as retort processing. In this regard, Patent Document 1 describes a method for increasing the crystallinity by heat-treating the vicinity of the bottom as a method for preventing deformation of the bottom in the retort treatment of the PET resin casing.

However, according to this method, a special heat treatment step is required, which increases the manufacturing cost. Conventionally, PET resin casings are mainly used for retort treatment at a temperature of about 100 to 120 ° C. However, soups and the like are treated at a temperature of about 120 to 130 ° C. in consideration of a realistic treatment time. There is a need for a housing that can be processed at higher temperatures.
JP 2001-150522 A

  Therefore, the present invention has been devised to solve the above-described problems, and suppresses deformation of the bottom portion in the retort process at a temperature of about 120 to 130 ° C., depending on the shape of the casing, particularly the trunk of the casing. With this in mind, the object of the present invention is to provide a synthetic resin casing that can reliably be used for retort foods and can be used safely in applications requiring retort processing.

The means of the invention according to claim 1 for solving the technical problem is as follows:
A synthetic resin casing in which a grounding portion for standing is disposed on the bottom surface of the bottom portion, and the bottom surface is recessed inward with the grounding portion as a base end to form a bottom raised portion,
When steam-type retort treatment is performed at a temperature of 120 to 130 ° C., the wall of the trunk portion can be reversibly bulged and deformed, and the difference between the inside of the casing and the retort pot is caused by the bulging deformation of the barrel wall. The pressure is maintained at 0.05 MPa or less, more preferably 0.03 MPa or less,
It is in.

The inventors of the present application have studied the shape of the bottom part or the body part in various ways, and in conducting experiments related to retort processing, the pressure difference between the inside of the housing and the retort kettle is a predetermined value even in the temperature range of 120 to 130 ° C. By setting it as the following ranges, it discovered that the deformation | transformation of a bottom part could be suppressed in the range which can maintain the stand-up property of a housing | casing by a grounding part practically, and came to the invention of Claim 1.
And the basic idea of the said structure of Claim 1 tries to relieve the pressurization state in the case of a retort process by the volume increase by the bulging-like deformation | transformation of the wall of a trunk | drum, and to suppress a deformation | transformation of a bottom part. Specifically, in the retort treatment at 120 to 130 ° C., by setting the differential pressure between the housing and the retort kettle within a range of 0.05 MPa or less, the range in which the standing property of the housing is not impaired. The deformation of the bottom can be suppressed.
Of course, if the deformation of the bottom portion can be suppressed in the temperature range of 120 to 130 ° C., the housing can be used with a margin even in the temperature range of 100 to 120 ° C. that has been conventionally used. it can.

And the flat cross-sectional shape of the body part is non-circular, such as providing a panel that can be inverted and deformed in a bulging shape on the body part, or making the body part an elliptical cylindrical flat shape. By deforming toward the end, the body wall can be stretched and permanently deformed, so that the cross-sectional area of the body can be increased and the capacity can be increased.
In addition, here, when referring to the resilience of the body wall after the retort treatment, for example, in a case made of PET resin or the like, the diameter of the body part shrinks at a high temperature of about 120 to 130 ° C., although there is a difference in degree. Such deformation is unavoidable, but it is only necessary that the deformation can be restored within a range that does not impair the appearance without leaving the distorted deformation.

  Further, considering the temperature unevenness in the retort pot and the uneven thickness distribution of the casing, the range in which the barrel wall can be bulged and deformed is made sufficiently large so that the differential pressure is 0.03 MPa or less. It is preferable.

  According to a second aspect of the present invention, in the first aspect of the invention, an annular grounding portion is provided on the bottom surface of the bottom portion, and the bottom surface is recessed in a convex shape toward the inside of the casing with the grounding portion as a base end. And forming a bottom raised portion.

  The said structure of Claim 2 concerns on the shape of a bottom part. An annular grounding part is arranged on the bottom surface of the bottom part, and the bottom part of the champagne bottom shape in which the bottom part is convexly convex toward the inside of the casing with the grounding part as a base end is symmetrical with respect to the central axis and is circumferential. The shape is isotropic, and the inner pressure acts uniformly in the circumferential direction, and by raising the bottom raising height, the shape can be made suitable for severe conditions such as retort processing.

  According to a third aspect of the present invention, in the second aspect of the invention, the outer diameter of the ground contact portion after the retort treatment is 85% or more of the outer diameter before the treatment.

  The above-described configuration of the invention described in claim 3 is one of the main factors that determine the limit relating to the deformation of the bottom portion, and the outer diameter of the grounding portion after the retort treatment is 85% or more of the outer diameter before the treatment. As a result, the stand-up of the housing by the grounding part can be sufficiently maintained in practice.

  According to a fourth aspect of the present invention, there is provided a biaxial stretch blow-molded product made of PET resin in the first, second or third aspect of the invention.

  According to the above-described configuration, the biaxial stretch blow-molded casing made of PET resin can have heat resistance sufficiently corresponding to the retort processing temperature by stretch crystallization, and further, By suppressing the deformation of the bottom so that it can bulge and deform, it is possible to provide a housing that can be used with confidence in retort processing at about 120 to 130 ° C.

  As the polyethylene terephthalate resin used in the present invention, PET is mainly used. However, as long as the essence of the PET resin is not impaired, a copolymer polyester mainly containing ethylene terephthalate units and containing other polyester units is also used. In addition, for example, in order to improve heat resistance, a resin such as nylon resin and polyethylene naphthalate resin can be blended and used. Examples of the component for forming the copolyester include dicarboxylic acid components such as isophthalic acid, naphthalene 2,6 dicarboxylic acid, and adipic acid, propylene glycol, 1,4 butanediol, tetramethylene glycol, neopentyl glycol, cyclohexanedimethanol, A glycol component such as diethylene glycol can be mentioned.

  Furthermore, as long as the essence as a PET resin casing is not impaired, the PET resin casing of the present invention is, for example, PET resin / nylon resin / PET resin for improving heat resistance and gas barrier properties. It may have an intermediate layer such as nylon resin.

The present invention has the above-described configuration, and has the following effects.
According to the first aspect of the present invention, the pressurization state during the retorting process at 120 to 130 ° C. is relaxed by the increase in volume due to the bulging deformation of the barrel wall, and the inside of the housing and the retort pot By making the differential pressure within the range of 0.05 MPa or less, more preferably 0.03 MPa or less, deformation of the bottom portion can be suppressed within a range in which the standing property of the housing is not impaired.

  In the invention according to claim 2, the bottom of the champagne bottom shape is symmetrical with respect to the central axis and is isotropic in the circumferential direction, and the internal pressure acts uniformly in the circumferential direction so that the shape is suitable for retort processing. be able to.

  In invention of Claim 3, it is one of the main elements which determine the limit which concerns on a deformation | transformation of a bottom part, By making the outer diameter of the grounding part after a retort process into 85% or more of the outer diameter before a process, The stand-up property of the housing by the grounding part can be sufficiently maintained practically.

In the invention described in claim 4, the biaxial stretch blow-molded casing made of PET resin can have heat resistance sufficiently corresponding to the retort processing temperature by stretch crystallization, and By suppressing the deformation of the bottom by making the portion bulging and deformable, it is possible to provide a housing that can be used with confidence in retort processing at about 120 to 130 ° C.

Embodiments of the present invention will be described below with reference to the drawings.
1 to 4 show an embodiment of the synthetic resin casing of the present invention.
FIG. 1 is a front view of the housing 1, and FIGS. 2A and 2B are outline outline diagrams of plane cross-sections along the lines AA and BB in FIG. 1, respectively. This casing 1 is a biaxially stretched blow molded product made of PET resin, and has a mouth tube part 2, a shoulder part 3, a body part 4 and a bottom part 5, has a height of 130 mm, a body diameter of 66 mm, and a small size for 300 ml. This is a round bottle. Further, the mouth tube portion 2 is in a state of being whitened by the thermal crystallization process, and further, a bottom raised portion 23 is formed in the bottom portion 5 in a depressed shape. 2 (a) and 2 (b), the two-dot chain line indicates a circle in which the outline of the cross section of the body 4 is inscribed.

  Two peripheral step portions 6 are provided above and below the body portion 4, and six panels 7 are formed in parallel between the peripheral step portions 6. And between the adjacent panels 7, the column part 9 of the longitudinal rib shape is formed in the state left without sinking, and the rigidity as the whole housing | casing 1 is ensured.

The panel 7 surrounded by the step portion 10 is composed of a concave portion 7a located above and a convex portion 7b located below. At the boundary between the concave portion 7a and the convex portion 7b, A boundary line 11 is formed.
And the pressure fluctuation inside the housing 1 in the pressurized state during the retorting process and in the decompressed state after cooling can be absorbed by the cooperative deformation of the concave portion 7a and the convex portion 7b.

  FIG. 3 is an explanatory view showing a deformed state of the panel 7 (concave portion 7a, convex portion 7b) in a pressurized state and a decompressed state. FIG. 3A shows a bulging state 15 (a bulging inversion deformed state 15a of the concave portion 7a and a bulging deformed state 15b of the convex portion 7b) in a pressurized state during the retorting process by a two-dot chain line. FIG. 7B shows a depressed state 16 (a depressed deformed state 16a of the concave portion 7a and a depressed inverted deformed state 16b of the convex portion 7b) in a depressurized state by cooling after the retorting process by a two-dot chain line.

4 (a) and 4 (b) are a vertical cross-sectional outline diagram in the vicinity of the bottom 5 of the housing 1 and a bottom view (b), respectively.
The bottom portion 5 has a bottomed cylindrical shape as a whole, has a heel portion 21 connected to the lower end of the body portion 4 and reduced in diameter with an outward curvature radius R1 to reach the bottom surface 5a. A portion 22 is provided, and with the ground contact portion 22 as a base end, a bottom raised portion 23 is formed by recessing the bottom surface 5a into a hemispherical shell with an inward radius of curvature R2 from the vicinity of the base end to the top.
The dimensions relating to the bottom 5 are as follows.
Outer diameter D of grounding part 22 46mm
Bottom height H1 18mm

  In FIG. 4 (a), the force acting on the bottom raising portion 23 in a pressurized state is divided into a pressing force acting in the lateral direction and a pressing force acting outward along the central axis direction, with white arrows. Indicated. Here, when the pressing force acting outward along the central axis direction becomes relatively large, the reverse deformation proceeds from the vicinity of the top portion, and the bottom falls.

Bottom deformation test (model test)
In order to observe and measure the deformation of the bottom when the pressure in the housing was changed at the predetermined retorting temperature using the housing 1, a model test according to the following procedure was performed.
1) Fill the mixture with a high temperature filling ratio of glycerin and water of 8: 1 to 3: 1 at a temperature of 100 ° C., cap and seal. At this time, the head space HS is set to 21 ml.
2) Dipping test As described in 1) above, the case in which the mixed solution is filled at high temperature is dipped in a glycerin solution at 120 to 130 ° C for 60 minutes. By changing the mixing ratio of the mixture from 8: 1 to 3: 1, the internal pressure is about 0.02 to 0.07 MPa with respect to the external pressure (atmospheric pressure (0.101 MPa)) in the range of 120 to 130 ° C. It changes in the range of the pressurized state.
In the following description, the pressure is described as a differential pressure with respect to atmospheric pressure (0.101 MPa).
3) Observation and measurement of deformation at the bottom after the test After cooling the casing after the test at 2), the deformation at the bottom is observed and measured.

Model Test Results The following results were obtained from the model tests as described above.
1) By setting the internal pressure to be in the range of 0.05 MPa or less in the temperature range of 120 to 130 ° C., the body panel 7 bulges and deforms as in the bulging state 15 in FIG. In the cooled state, it became like a depressed state 16 in FIG. 3B, and there was no permanent deformation that impairs the appearance accompanying the bulging deformation at high temperature.
2) On the other hand, when the internal pressure exceeds 0.05 MPa, the panel 7 of the body 4 is in the bulging state 15 as shown in FIG. Deformation became larger and the fall angle was reduced.
Here, the above-mentioned fall angle is an inclination angle at which the case falls when the case is placed upright on a horizontal stand and the stand is gradually inclined from the horizontal direction. It is a measure of sex.

Retort treatment test A retort treatment test was conducted to confirm the model test. 1 was filled with water at a temperature of 90 ° C. at a temperature of 90 ° C. (head space was 21 ml), and the temperature was 124 ° C. for 42 minutes (the time range indicated by the white arrow in the graph). The retort treatment was carried out by the steam method under the conditions of FIG. 5 is a graph showing changes in temperature and pressure during the retort treatment test, where Tre and Pre indicate the temperature and pressure in the retort kettle, and Pb indicates the pressure in the enclosure. When the temperature Tre of the retort kettle was stable at 124 ° C., the pressure inside the retort kettle was 0.130 MPa, the pressure inside the casing was 0.159 MPa, and the differential pressure was 0.029 MPa.
Note that the condition of the temperature of 124 ° C. and 42 minutes is a condition corresponding to the sterilization conditions of soup and the like.

The falling angle after the test was not changed from the value before the test, the outer diameter D of the ground contact portion 12 was 42 mm, and the raised height H1 was 16 mm, respectively 91% and 89% before the test.
Although the shrinkage of the outer diameter D of the grounding portion 12 and the bottom raising height H1 is considered to be thermal shrinkage accompanying the progress of crystallization at 124 ° C., it is not a distorted deformation but is deformed uniformly. There was nothing.
In addition, as for the body 4, when it is cooled after the test, the panel 7 of the body 4 is in a depressed state 16 in FIG. 3B, and is permanently deformed so as to impair the appearance accompanying the bulging deformation at a high temperature. There was no.

  On the other hand, in the trunk portion 4 of the embodiment shown in the casing 1 of FIG. 1 as a comparative example, the above-mentioned retort processing test is performed on the casing when the panel 7 is not formed, that is, the casing having a cylindrical portion 4. A similar test was conducted. As a result, the housing pressure Pb was 0.196 MPa, the differential pressure was 0.066 MPa, and the bottom 5 was bulging and deformed, so-called bottom-down state.

In addition, the effect of this invention is not limited to the housing of the said Example, For example, the shape of the panel of a present Example is an example for enabling reversible bulging deformation.
Basically, the upper cross section of the upper and lower ends of the body is made into a perfect circle without deformation with respect to the internal pressure as in the case 1 shown in FIG. 1, and the height between them is required by bulging deformation. In consideration of the capacity increase, for example, the Rs value (Sc) which is the ratio of the plane cross-sectional area Sa at an arbitrary intermediate height of the body and the area Sc of the perfect circle having the same circumference as the circumference of this section. In consideration of / Sa), the shape of the trunk can be determined while harmonizing with the overall appearance of the bag.

  That is, the required capacity increment ΔC due to the bulging deformation of the body portion in order to make the pressure in the housing at 0.05 MPa or 0.03 MPa or less at a predetermined temperature is obtained by the above-described model test method or the approximate value is obtained by calculation. You can also Then, an Rs value capable of this capacity increment ΔC can be calculated, and the flat cross-sectional shape of the body portion can be determined so as to satisfy the Rs value.

  For example, in the retort test, in the case 1 of FIG. 1, the capacity increment for making the differential pressure between the inside of the case and the retort pot at 0.03 MPa at 124 ° C. is about 23 ml. Since the volume before the test between the upper and lower peripheral step portions 6 is about 190 ml, the average cross-sectional area is increased by about 1.12 (213/190) times due to the bulging deformation between the upper and lower peripheral step portions 6. There is a need to. That is, the plane cross-sectional shape can be determined so that the Rs value is 1.12 or more on average between the upper and lower peripheral step portions 6.

  Incidentally, Rs values for some shapes are shown. The regular polygons are a regular triangle 1.62, a regular tetragon 1.27, a regular hexagon 1.08, and a regular octagon 1.05. The ellipse has a major axis / minor axis of 1.5 and an ellipse of 1.06, and the major axis / minor axis of 2.0 has a value of 1.19. Of course, like the concave portion 7a of the panel 7 of the embodiment, the Rs value of the portion that bulges by being inverted and deformed can be made a considerably large value. For example, the Rs value in a plane cross section (see FIG. 2A) along the line AA in FIG. 1 is about 1.19.

  The synthetic resin casing of the present invention can be used for steam heating type retort processing even at 120 to 130 ° C., and can be expected to be used in a wide range of applications.

It is a whole front view which shows the Example of the synthetic resin casings of this invention. It is the plane sectional view along the AA line of the housing of Drawing 1, and (b) the plane outer contour line figure along the BB line. 1A is an explanatory view showing a deformed state of a panel in a swelled state, and FIG. 2B is an explanatory view showing a deformed state of the panel in a depressed state. It is the (a) vertical section outside outline figure near the bottom of the case of Drawing 1, and (b) the bottom view. It is a graph which shows the change of temperature and pressure during a retort processing test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Housing 2; Mouth part 3; Shoulder part 4; Trunk part 5; Bottom part 5a; Bottom face 6; Circumferential part 7; Panel 7a; Concave part 7b; Convex part 9; Boundary line 15; bulging state 15a; bulging inversion deformation state 15b; bulging deformation state 16; depression state 16a; depression deformation state 16b; depression inversion deformation state 21; heel portion 22; grounding portion 23; bottom raising portion R1, R2 ; Radius of curvature H1; raised height D; outer diameter Tre; retort kettle temperature Pre; retort kettle pressure Pb;

Claims (4)

A grounding portion (22) for standing is arranged on the bottom (5) bottom surface (5a), and the bottom surface (5a) is recessed inward with the grounding portion (22) as a base end, and a bottom raising portion (23) is formed. The formed casing (1), when the steam retort treatment at a temperature of 120 to 130 ° C. is performed, the wall of the trunk (4) is reversibly bulged and deformable, and the trunk (4 ) A synthetic resin casing configured such that the differential pressure between the casing (1) and the retort kettle is maintained within a range of 0.05 MPa or less, more preferably 0.03 MPa or less by wall bulging deformation. An annular grounding portion (22) is arranged on the bottom (5) bottom surface (5a), and the bottom surface (5a) is recessed inwardly into the housing (1) with the grounding portion (22) as a base end. The synthetic resin casing according to claim 1, wherein a bottom raised portion (23) is formed. The synthetic resin casing according to claim 2, wherein the outer diameter of the ground contact portion (22) after the retort treatment is 85% or more of the outer diameter before the treatment. The synthetic resin casing according to claim 1, 2, 3, or 4, which is a biaxially stretched blow molded product made of polyethylene terephthalate resin.

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