JPH0335192B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to an internal pressure heat-sealed package and a method for manufacturing the same, and more particularly, it relates to an internal pressure heat-sealed package and a method for manufacturing the same. The present invention relates to a heat-sealed package and a method for obtaining the package. The present invention further has excellent appearance characteristics,
The present invention also relates to an internal pressure heat-sealed package having high commercial value and a method for manufacturing the same. Prior Art and Technical Problems of the Invention Conventionally, single-layer or multi-layer (laminated) plastic films or sheets have been processed by vacuum forming, pressure forming,
Formed into a cup shape with a flange using plug assist molding, press molding, stretch molding, etc.
Containers in which a heat-sealed seal is formed between the flange of the container body and the lid have come to be widely used as containers for storing various foods and the like. There are various types of heat-sealing between the flange and the lid. For example, heat-sealing resin such as olefin resin is used as the material for the outer surface of the flange and the inner surface of the lid, and the heat-sealing strength of both is 1 to 4 kg/1.5. cm range, and a composition of olefin resin, waxes, and tackifier is used as the inner material of the lid to improve the heat seal strength of both, which is called easy-to-peel adhesion.
Those adjusted to a range of 500g/1.5cm to 1.5Kg/1.5cm are known. Although these heat-sealed containers show almost satisfactory results for contents where the inside of the container is at normal pressure or reduced pressure, they do not work well when the internal pressure is high, such as containers for beer, carbonated drinks, etc., or nitrogen-filled packaging. Even the former heat-seal type container is still not fully satisfactory in terms of high sealing strength, variation in sealing strength, etc., for applications in which containers are used. That is, in the production of this internal pressure package, there is always fluid movement at the interface to be heat-sealed, and heat sealing must be performed while sealing this fluid movement, and even if the fluid can be contained, melting Since shearing force along the heat-sealing interface always acts on the heat-sealable resin in this state, it becomes difficult to form a strong heat-sealing bond. Thus, in the case of an internal pressure package, the seal strength is considerably lower than that of a normal pressure package, and the heat-sealed portion that is formed easily causes problems such as seal breakage and leakage over time. Furthermore, in order to increase the sealing strength of the heat-sealed part, a resin ring is used to reinforce the periphery of the heat-sealed part, but in this case, it inhibits the temperature drop in the sealed part and at the same time directly cools the sealed part. If the pressure required for sealing is released within a short period of time after sealing, the resin in the sealing part will not be sufficiently cooled and solidified.
Stable seal strength cannot be obtained. OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide an internal pressure heat-sealing package that can reliably and firmly seal a container filled with a pressurized content with a heat-seal lid, and a method for manufacturing the same. be. Another object of the present invention is to provide a package in which heat-sealing is performed on an assembly of a container and a lid having the above-mentioned contents, which has excellent sealing strength and sealing reliability over time, and a method for manufacturing the same. is to provide. Another object of the present invention is to provide an internal pressure heat-sealed package with excellent appearance characteristics and a method for manufacturing the same. Yet another object of the present invention is to provide a method for producing internal pressure packages at high production rates. Structure of the Invention According to the present invention, the apparatus includes a circumferential side wall part, a bottom part continuous to the lower end of the side wall part, and a heat sealing circumferential part continuous to the upper end of the side wall part, and heat sealing of at least the inner surface of the container and the circumferential part. A container body whose surface is made of crystalline propylene resin, a lid made of a laminate of metal foil and a heat sealant layer of crystalline propylene resin, and a peripheral part of the container body and the lid. The crystalline propylene-based resin in the heat-sealed portion of the sealed portion is expressed by the following formula Rc=C ₁ /C ₂ ×100 where C ₁ is the crystalline propylene resin. Heat of fusion in the first strand using a differential calorimeter for resins
cal/g, and C ₂ represents the heat of fusion cal/g of the same resin in the second run. The heating rate for measurement was 10deg/min, and the cooling rate from first run to second run was 2.50deg/min.
Let it be min. Provided is an internal pressure heat seal package characterized in that the heat of fusion ratio (Rc) defined by is suppressed to a crystalline state of 95% or less, particularly preferably 90% or less. According to the present invention, the present invention also includes a circumferential side wall, a bottom connected to the lower end of the side wall, and a heat-sealing flange connected to the upper end of the side wall, and at least the inner surface of the container and the surface of the flange to be heat-sealed are made of crystalline propylene. A container body made of a base resin is filled with contents having an autogenous pressure, and the flange portion is engaged with a lid body made of a laminate of a heat sealant layer of a metal foil and a crystalline propylene resin, The flange portion and the lid are subjected to high-frequency induction heating under pressure, and the upper surface of the lid is brought into contact with a cooling medium just before or immediately after the crystalline propylene resin for heat sealing reaches the heat sealing temperature. The crystalline propylene resin is in a crystalline state with a heat of fusion ratio (Rc) defined by the above formula of 95% or less, particularly preferably 90% or less.
Provided is a method for producing an internal pressure heat-sealed package characterized by supercooling and solidifying under pressure due to heat conduction of the lid. According to the present invention, the crystalline propylene resin for heat sealing the container body flange is suppressed to a crystalline state in which the heat of fusion ratio (Rc) defined by the above formula is 95% or less, particularly preferably 90% or less. A method is provided, characterized in that: Preferred Embodiments of the Invention The present invention will be described in detail below based on specific examples shown in the accompanying drawings. Structure of the Packaging Body In FIG. 1 showing an example of the container used in the method of the present invention, the container body 1 is formed as a seamless integral structure made of thermoplastic resin. It consists of a bottom part 3 continuous to the lower end of the circumferential side wall part and a heat sealing flange 4 continuous to the upper end of the side wall part. The cup-shaped container body 1 is formed, for example, by gripping the peripheral edge of a disc-shaped plastic material with an annular gripper and pushing a molding punch (plunger) into it to perform stretch molding. , the flange 4 has approximately the same thickness as the material, but the circumferential side wall 2 is thinned by being stretched in the axial direction in accordance with the indentation dimension of the punch, and has molecules oriented in the axial direction. ing. In this specific example, as shown in the cross-sectional view of FIG. Vinyl alcohol copolymer, vinylidene chloride resin,
The intermediate layer 7 is made of a high nitrile resin or a nylon resin, and these inner and outer surface layers and the intermediate layer are bonded to a resin that exhibits thermal adhesive properties, such as an acid-modified olefin resin or a copolyester adhesive. They may be bonded via adhesive layers 8 and 9 made of adhesive resin, epoxy-modified thermoplastic adhesive resin, or the like. On the other hand, in FIGS. 3-A and 3-B, the lid 10 to be engaged with the flange portion 4 of the container body 1 has a heat-sealable laminate 11 and a peripheral portion used for heat sealing. It consists of a reinforcing resin ring 12, and the resin ring 12
is adhered to the upper surface of the periphery of the laminate 11. In this specific example, the shape of the lid 10 can be changed depending on the position of the surface to be heat-sealed, the width, the reinforcing properties of the resin ring 12, etc., as shown in the figure. Furthermore, as shown in the enlarged sectional view of FIG. 4, the laminate 11 of the lid 10 includes a metal foil substrate 13 that provides gas barrier properties and pressure resistance to the lid, and a heat seal applied to the lower surface of the metal foil substrate 13. Polypropylene resin layer 1
4 and a resin protective coating layer 15 applied to the other surface. The heat-sealable resin layer 14 is
It is combined as the same type of resin layer 5 that forms the upper surface of the flange of the container body 1. Resin protective coating layer 1
5 may be of the same type as the heat-sealable resin or may be of a different type. Heat sealing According to the present invention, beer,
It is filled with contents having autogenous pressure such as low-malt beer, cola, carbonated fruit juice drinks, and other carbonated drinks, or a combination of nitrogen and fruit juice or other contents, and the flange portion 4 of the container body 1 and the lid body are filled. 10 heat-sealable resin layers 14 are engaged with each other. Next, the flange portion 4 and the lid body 10 are pressurized,
Utilizing the conductivity of the metal foil of the lid 10, the assembly of both is heated by high frequency induction under pressure. By induction heating, the heat-sealing resin layer 14 adjacent to the metal foil substrate 13 or the resin layer 5 at the flange portion in contact with the resin layer 14 is heated, and the resins are fused together at the heat-sealing interface. In the present invention, the container flange portion 4 and the lid body 1
From the standpoint of forming a strong heat-sealed sealing structure that can withstand pressure between It is important to use a type resin. In the present invention, the top surface of the lid is brought into contact with a cooling medium just before or immediately after the crystalline propylene resin in the heat seal part reaches the heat seal temperature, and the crystalline propylene resin in the heat seal part is It is supercooled and solidified under pressure by heat conduction through the lid so that the defined heat of fusion ratio (Rc) becomes a crystalline state of 95% or less, particularly preferably 90% or less. FIG. 5 shows a container body 1 whose inner surface and heat-sealing surface are made of polypropylene, filled with beer at a temperature of 5° C., and a lid body 10 having the shape shown in FIG. After engaging the part 4 and pressurizing and fitting the two, the engaging part is heated by high frequency induction, and then the temperature (T°C) of the heat sealing resin layer of the engaging part when the heating is stopped and the time ( t seconds) is a diagram showing the relationship between curve A
is a temperature increase curve, curve B is a temperature decrease curve due to cooling, and curve C is a temperature increase curve of 5° C. immediately after heating the top surface of the lid 10 is stopped.
The temperature drop curve is shown when the sample is brought into contact with cold water. According to this result, as shown in curve A, the temperature of the heat-sealable resin is set at the optimum heat-sealing temperature (T
m), for example, the temperature reaches 200°C, but when the induction heating current is cut off and the temperature is allowed to cool, the temperature of the resin layer decreases within a short period of 1 to 2 seconds, as shown in curve B. Even if the temperature drops to lower than the melting point or softening point of the resin, the temperature around the seal part
As shown in Figures 3-B, since it is covered with a resin ring, the temperature of the sealed part does not drop easily when left to cool;
It is clear that the cooling temperature (Ts) is kept at a relatively high temperature for a relatively long time. On the other hand, according to the present invention, when the top surface of the lid is brought into contact with cooling water immediately after cutting off the induction heating current, the temperature of the resin layer is reduced due to the excellent thermal conductivity of the metal foil of the lid body 10. , 1 to 2 as shown in curve C
Cooling temperature (Ts) for curve B within a short period of seconds
It is clear that the temperature can be lowered to below. Figures 6-A and 6-B are melting curves of polypropylene in the flange portion of the heat-sealed portion measured using a differential scanning calorimeter. Here, Figure 6-A is a melting curve of polypropylene at the flange part of the heat-sealed part cooled according to curve B in Figure 5, and curve-1 is a heating rate of 10 de.
It represents the melting curve of the first strand measured in g/min, and curve-2 shows the cooling rate after the first strand.
After the temperature was lowered at 2.50deg/min, it also decreased by 10deg/min.
It shows the melting curve of the second run measured at a heating rate _{of min, and the heat of fusion ratio (Rc=C 1 / C 1} × 100) indicates a value of 96%. On the other hand, Figure 6-B is a melting curve obtained by measuring the polypropylene of the flange part of the heat-sealed part that was rapidly cooled according to curve C in Figure 5 in the same manner as in Figure 6-A. The heat of fusion ratio (Rc) is
88%, which is smaller than the value obtained from Figure 6-A. When testing the strength and sealing reliability of the heat-sealed portion of the internal pressure package manufactured in this way, it was found that it had a cooling history of curve B in Figure 5, and curves 1 and 2 in Figure 6-A. The heat-sealed part with the heat of fusion ratio (96%) calculated from
On the other hand, when aged at room temperature, seal failure and leakage occur within 1 to 15 days, whereas it has a cooling history of curve C in Figure 5,
In addition, the heat-sealed part with the heat of fusion ratio (88%) determined from curves 1 and 2 in Figure 6-B is 14 kg/
It exhibits a large seal strength of 1.5cm, and when left at room temperature, no seal failure or leakage occurs even after one month. In the present invention, as is clear from the above facts, the crystalline propylene resin in the heat-sealed portion is expressed by the following formula Rc=C ₁ /C ₂ ×100, where C ₁ is the differential resistance of the crystalline propylene resin. Heat of fusion in the first strand in a calorimeter
cal/g, and C ₂ represents the heat of fusion cal/g of the same resin in the second run. The heating rate for measurement was 10deg/min, and the cooling rate from first run to second run was 2.50deg/min.
Let it be min. By maintaining the crystalline state in which the ratio of heat of fusion (Rc) defined by A strong heat-seal seal is possible even under conditions where gas is flowing through the seal, and this heat-seal part maintains excellent sealing performance over time even under constant pressure. It is something that Generally speaking, the heat of fusion of a crystalline resin depends on the degree of crystallization of the resin, and the lower the degree of crystallization, the smaller the value, but the range of change is not so large. In the present invention, the crystalline state of the crystalline propylene-based resin in the heat-sealed portion is defined by its heat of fusion. This is because it has a critical effect on leakage prevention, and it is also because heat transfer actually has a significant effect on the heat sealing of the resin. for example,
In the case of polypropylene resin, there is a crystallization temperature range in the temperature range of 60 to 70°C where the crystallization rate is quite high. The resin ring reinforcing the heat sealing part shown in Figures -A and 3-B prevents the temperature of the sealing part from decreasing, and as a result, crystallization of the propylene resin occurs to a higher degree. At the same time, it seems that the sealing strength is low and the sealing reliability is not achieved because the cooling and solidification are not sufficiently performed. On the other hand, according to the present invention, when the top surface of the lid 13 is brought into contact with the cooling medium, the resin in the heat-sealed portion is heated to a temperature lower than the crystallization temperature range due to large heat conduction from the metal foil constituting the lid. The crystallization of the resin layer is suppressed as described above, and at the same time, the resin is rapidly solidified under pressure, preventing flow due to internal pressure of the resin and foaming at the heat seal interface. As a result, high sealing strength and sealing reliability over time can be obtained. In other words, by regulating the crystalline state of the crystalline propylene resin in the heat-sealed part,
It is possible to obtain stable and high heat seal strength. In the specific example described above, the top surface of the lid comes into contact with the cooling medium immediately after the resin in the heat-sealing part reaches the heat-sealing temperature, but it is possible to bring the top surface of the lid into contact with the cooling medium earlier. , the contact between the two can be made immediately before the resin in the heat-sealing portion reaches the heat-sealing temperature. Note that immediately before and immediately after this differ depending on the temperature increase rate during induction heating, but it is desirable that it is within ±0.5 seconds, particularly within ±0.1 seconds, based on the time when induction heating is stopped. It may be possible to keep the top surface of the lid in contact with the cooling medium from the start of heating, but in this case, the temperature of the resin in the heat-sealed part will rise slowly,
There is also the disadvantage that heat energy is wasted. In the present invention, any gas, liquid or solid cooling medium can be used as the cooling medium, such as cold air blowing, liquid nitrogen gas blowing, freon gas blowing,
In addition to cold water spraying, cold water immersion, or contact with running water, rapid cooling can be performed by bringing a cooling plate cooled with these refrigerants, Freon, brine, etc. into contact with the top surface of the lid. Among these cooling means, water cooling is particularly desirable. That is, water has large latent heat and sensible heat compared to other media, and is particularly excellent in terms of cooling efficiency. In the present invention, the lid body and the flange are pressurized through the process of high-frequency induction heating and rapid cooling, and the degree of pressurization is sufficient to contain the passage of gas through the sealing part, and the content is Generally, this pressure should be on the order of 1 to 10 kg/cm ² , particularly 3 to 8 kg/cm ² , although it also varies depending on the degree of pressure. In the present invention, by bringing the top surface of the lid into contact with the cooling medium as soon as the resin reaches the heat sealing temperature by high-frequency induction heating, the time required for heat sealing as a whole is reduced compared to when cooling naturally. The time can be shortened to 1/2 to 1/3, and the production speed can be improved by an amount corresponding to this shortened time. Furthermore, a problem that arises when a lid made of a laminate of metal foil and resin is heat-sealed to a container flange is the occurrence of flow marks on the top surface of the lid. The flow mark refers to a ring-shaped pattern on the top surface of the lid inside the inner heat-sealed portion, which is different from the top surface of the central portion of the lid and can be easily identified with the naked eye. The reason for the occurrence of flow marks has not yet been elucidated, but the resin layer close to the heat-sealed portion may melt due to the diffusion of temperature during heat-sealing, or even if it does not melt, it may crystallize. This is thought to be due to the increasing degree of According to the present invention, by bringing the top surface of the lid into contact with the cooling medium as soon as the resin in the heat-sealing portion reaches the heat-sealing temperature, the generation of flow marks is significantly suppressed, and as a result,
This makes it possible to increase the commercial value of the internal pressure package. In FIG. 7, which shows a schematic arrangement of an apparatus suitable for carrying out the invention, a content 1 having an autogenous pressure is shown.
A holder 17 is provided which supports the assembly of the container body 1 filled with 6 and the lid 10 shown in FIG. 3-B at the flange portion 4. This holder 17
A fluid cylinder 25 for moving the holder 17 up and down relative to the heating and cooling head 18 is provided below. A heating and cooling head 18 is fixed to the machine 24, and this head 18 is attached to the reinforcing ring 12 of the lid 10.
It has a high-frequency induction heating coil 19 that can be engaged with the cooling medium, and a cooling medium outlet nozzle 20 is provided in the center thereof. The nozzle 20 is connected to a normally closed solenoid valve 21 and a refrigerant inlet path 22 . Further, a refrigerant outlet path 23 is provided between the heating coil 19 and the nozzle 20.
During heat sealing, the container 1-lid 10 assembly is supported by the holder 17, and the fluid cylinder 25 is
Activate. As a result, the holder 17 rises, and the lid 10 and the flange portion 4 are pressurized with a constant pressure between the heating coil 19 and the holder 17. In this state, the heating coil 19 is energized for a predetermined set time to heat the heat-sealing resin layer to a predetermined temperature. At the same time as the heating coil 19 is de-energized, the electromagnetic valve 21 is activated, and a cooling medium such as water is supplied to the upper surface of the lid 10 through the passage 22 and the nozzle 20, thereby performing the rapid cooling described in detail above. At the same time, excess cooling medium is discharged to the outside via passage 23. At this point, the operation of the solenoid valve 21 is cut off, and the supply of the cooling medium is cut off. Next, the operation of the air cylinder 25 is stopped, and the holder 17 is lowered accordingly, completing the heat sealing operation. Moreover, FIG. 8 shows the lid body 10 shown in FIG. 3-A.
1 is a schematic diagram of an apparatus in which a heat sealing operation is performed in the same manner. Structure of the container body In the present invention, the container body is formed by the above-mentioned overhang molding (plug and ring forming),
The container is formed by solid phase pressure forming such as plug assist molding and pressure forming, and the side wall of the container has molecules oriented at least in the axial direction of the container, which provides sufficient pressure resistance against the contents that have autogenous pressure. grant,
It is also desirable for imparting transparency to the vessel wall. Of course, by imparting molecular orientation to the vessel wall, gas permeation through the vessel wall can also be suppressed to a small level. In the present invention, it goes without saying that the container body may be made of a single layer of crystalline polypropylene;
By adopting a laminated structure consisting of inner and outer surface layers made of crystalline propylene resin and an intermediate layer of gas barrier thermoplastic resin, the permeation of carbon dioxide gas contained in the contents through the container wall is suppressed to a significantly small level. It becomes possible to do so. In addition to isotactic homopolypropylene, crystalline propylene-based resins include propylene-ethylene copolymer, propylene-butene-1 copolymer, and propylene-ethylene copolymer within the range that satisfies the condition of crystallinity. -Butene-1 copolymer or a blend of two or more thereof can be used. For the purpose of maintaining pressure resistance, it is important that the propylene resin used has a melting index of 0.1 to 10 g/10 minutes, particularly 0.3 to 5 g/10 minutes. In the present invention, the crystalline propylene resin for heat sealing in the flange of the container main body used for manufacturing the package is a crystalline resin having a heat of fusion ratio (Rc) defined by the above formula of 95% or less, particularly preferably 90% or less. It has been found that when the heat-sealing condition is suppressed, significant advantages are achieved both in terms of heat-sealing workability and in terms of the strength of the heat-sealed portion. That is, the heat-sealing surface made of such a propylene-based resin melts with a relatively small amount of heat of fusion, and brings about a remarkable operational advantage in that fusion can be performed within a short period of time. Furthermore, since only a small amount of heat is required for heat-sealing, thermal deterioration of the resin is prevented, cooling is performed in a short time, and heat-sealing strength is also improved. The effects of the present invention will be specifically explained using the following example. Example 1 It has a symmetrical layer structure of polypropylene (PP)/maleic anhydride-modified polypropylene (ADH)/ethylene-vinyl alcohol copolymer (EVOH)/maleic anhydride-modified polypropylene/polypropylene, and the weight composition ratio is PP/ADH. /EVOH=
The cup is molded from a 3.7 mm thick laminated sheet of 92/4/4 and has a flange at the opening as shown in Figure 1 (the flange has an inner diameter of 70 mm and an outer diameter of 75 mm).
mm, height 156 mm, body thickness 0.5-1.0 mm), ethylene-propylene random copolymer (20 μm)/urethane adhesive/soft aluminum (150 μm)
m)/Maleic anhydride modified polypropylene + ethylene/propylene random copolymer (15μ
Regarding the concave circular lid material with a diameter of 75 mm punched from a laminated film having a layer structure of m) / ethylene propylene block copolymer (70 μm),
Ethylene is applied to the outer surface of the periphery to be heat-sealed.
The lid shown in Figure 3-B has a resin ring made of propylene block copolymer temporarily attached (ring inner diameter 65 mm, ring outer diameter 76 mm, ring height 10 mm).
I got it. After filling the cup with beer at a temperature of approximately 5°C and fitting the lid to the opening flange thereof, high-frequency heating is performed using the apparatus shown in Fig. 7 under the set output, heating time, and sealing pressure. Thermal fusion was performed using induction heating. After the high frequency induction heating, while maintaining the sealing pressure, using the cooling device shown in Figure 7,
The sealing operation was completed by cooling the vicinity of the sealing portion on the top surface of the lid body for 1 second using water as a medium, and then releasing the pressure. Immediately after filling the sample thus obtained, we conducted an instantaneous pressure test and a seal strength (T-peel strength) test.As shown in Table 1, the average instantaneous pressure resistance was 6.0Kg/cm. ^2. The seal strength was 14Kg/1.5cm, and the variation between samples was small, resulting in a stable and high seal strength. Furthermore, when we observed the fracture locations in each test, we found that in both tests, the fracture occurred due to a rupture of the lid material along the inner circumference of the seal part, or
This was due to cohesive failure of the inner surface material of the lid, and no seal failure was observed in the seal portion. In addition, as a result of similarly filling a heavy sodium citric acid aqueous solution adjusted to exhibit an internal pressure of 1.5 kg/cm ² at 15°C and conducting a storage test at 15°C, it was found that even after one month had passed after filling, There were no samples that resulted in leakage, and no peeling between the lid material and the flange at the sealing part, peeling inside the lid material, or foaming was observed, demonstrating high sealing reliability over time. In addition, similar to those used in the instantaneous compressive strength and seal strength tests, for samples filled with beer at approximately 5°C, the polypropylene on the top surface of the flange of the seal part was peeled off, and the heat of fusion was measured using a differential calorimeter. When measured in the temperature range from 50° C. to 200° C. using a heating rate of 10 deg/min, the ratio of heat of fusion between first run and second run was 88%. Here, the second run was measured immediately after the first run, after lowering the temperature to 50° C. at a cooling rate of 250 deg/min. Example 2 Regarding the cup and lid described in Example 1, after filling the cup with beer at a temperature of about 5°C and fitting the lid into the opening flange, a mist was applied to the top of the lid as a cooling medium. Water was sprayed and heat fusion was carried out in the same manner as in Example 1. After heating, the sealing pressure was maintained and allowed to cool for 1 second, then the pressure was released and the sealing operation was completed, but the sealing conditions at this time were the same as in Example 1.
The amount of heat required for sealing was approximately 10% higher than that for the conventional method. The samples obtained in this way were subjected to the same tests as in Example 1, and as shown in Table 1, they showed stable and high sealing strength and sealing reliability over time that were almost the same as in Example 1. Obtained. Further, as in Example 1, the heat of fusion of the polypropylene on the upper surface of the flange in the sealed portion after sealing was measured under the same measurement conditions, and the heat of fusion ratio was 89%. Comparative Example 1 Regarding the cup and lid described in Example 1, after filling the cup with beer at about 5°C and fitting the lid into the opening flange, using the apparatus shown in FIG. 7, Thermal fusion was carried out by high frequency induction heating under the same sealing conditions as in Example 1. After the high-frequency induction heating, the sealing pressure is maintained and the area near the top seal part of the lid body is left to cool for one second without using water as a medium, and then the pressure is released to complete the sealing operation. did. Immediately after filling the samples thus obtained, peeling occurred at the seal interface due to the pressure of the contents, resulting in leakage. This seems to be because the polypropylene resin in the heat-sealed seal portion was not sufficiently cooled and solidified under the cooling conditions of leaving it to cool for 1 second after heating. As in Example 1, the heat of fusion of the polypropylene on the upper surface of the flange in the sealed portion after sealing was measured, and the heat of fusion ratio was 98%. Comparative Example 2 The cup and lid described in Example 1 were filled with beer at approximately 5°C in the same manner as in Comparative Example 1, and the fitting portion was sealed, but after heat fusion, the cup and lid were left to cool. The time was set to 2 seconds. The sample obtained in this way did not leak immediately after filling as in Comparative Example 1, but as a result of conducting the same test as in Example 1, the average value The instantaneous compressive strength is 3.7Kg/
cm ² and seal strength were 8.2 Kg/1.5 cm, which were lower than those of Example 1, and furthermore, because the variations in each value were large, the seal strength was low and unstable. Furthermore, it was observed that the failure point in each test was separation of the lid material and flange part at the seal part. In addition, in the same storage test at 15°C as in Example 1, all samples were stored for 1 day or more after sealing.
After 10 days, peeling between the lid and the flange at the sealing part, as well as peeling and foaming inside the lid, were observed, and after about 2 weeks, all of them had leaked. In all of these samples, after the sealing operation was completed, an annular pattern with a width of about 5 to 10 mm was observed near the sealing part on the top surface of the lid, but this was due to the heat generated during sealing on the top surface of the lid. It seems to be the traces of melted resin. Although such a pattern may reduce its commercial value, it was not observed in Examples 1 and 2. As in Example 1, the heat of fusion ratio of the polypropylene on the upper surface of the flange in the sealed portion after sealing was measured, and the heat of fusion ratio was 96%. Example 3 A cup molded from the laminated sheet described in Example 1 and having a flange at the opening and the shape shown in Fig. 1 (flange inner diameter 70 mm, outer diameter 77.5 mm, height
156 mm, body thickness 0.5 to 1.0 mm) and a circular lid member with a diameter of 76.5 mm punched from the laminated film described in Example 1, the outer surface of the periphery to be heat-sealed was made of ethylene-propylene block copolymer. Figure 3 with the resin ring temporarily attached.
A lid body having the shape shown in A (ring inner diameter 70 mm, ring outer diameter 79 mm, ring thickness 3 mm) was obtained. After filling the cup with beer at about 5°C and fitting the lid, using the apparatus shown in FIG.
Thermal fusion was performed using high-frequency induction heating under the set output, heating time, and sealing pressure. After the high-frequency induction heating, while maintaining the sealing pressure, the area around the top seal of the lid is cooled for one second using water as a medium using the cooling device shown in Figure 8, and then the pressure is released to seal the area. The operation has ended. The samples obtained in this way were subjected to the same tests as in Example 1, and as shown in Table 2, they exhibited stable and high sealing strength and sealing reliability over time that were almost the same as in Example 1. Obtained. The heat of fusion of the polypropylene on the top surface of the flange part corresponding to the seal part of the cup used in this example was measured in the same manner as in Example 1. When expressed as a heat of fusion ratio, the value was 91% before sealing and 91% after sealing. It was 86%. Example 4 Regarding the cup described in Example 3, a hot plate and a cooling plate were alternately brought into contact with the upper surface of the flange used for heat sealing under constant pressure, and immediately after melting the polypropylene on the upper surface of the flange, quenching was performed. It was processed to solidify it. The cup processed as described above and the lid described in Example 3 were filled with beer at approximately 5°C in the same manner as in Example 3, and the fitting portion was sealed. Compared to Example 3, the conditions are as follows:
The amount of heat required for sealing was approximately 20% lower. Further, the cooling operation after heating was performed in the same manner as in Example 3. The evaluation results of the samples obtained in this way are the second
As shown in the table, the stable and high sealing strength and sealing reliability over time are almost the same as in Example 3, but the fact that the amount of heat required for the seal can be reduced compared to Example 3 is that This has advantages such as shortening heating time and preventing thermal deterioration of the resin near the sealing part. The heat of fusion of the polypropylene on the top surface of the flange part corresponding to the seal part of the cup used in this example was measured in the same manner as in Example 1. When expressed as a heat of fusion ratio, it was 86% both before and after sealing. It was hot.

【table】

【table】 [Brief explanation of drawings]

Fig. 1 is a side sectional view of a container used in the present invention, Fig. 2 is an enlarged sectional view showing the cross-sectional structure of the container, and Fig. 3-
Figures A and 3-B are side sectional views showing two examples of the lid body used in the present invention, Figure 4 is an enlarged sectional view showing the cross-sectional structure of the lid body, and Figure 5 is the seal temperature during heat sealing. A diagram showing the relationship between and over time,
Figures 6-A and 6-B are melting curves of polypropylene in the heat-sealed flange section measured by a differential scanning calorimeter, and Figure 6-A is the melting curve of polypropylene cooled according to curve B in Figure 5. , FIG. 6-B shows cooling according to curve C of FIG. layout drawing. DESCRIPTION OF SYMBOLS 1... Container body, 2... Circumferential side wall part, 3... Bottom, 4... Heat sealing flange, 5... Inner surface layer, 6... Outer surface layer, 7... Intermediate layer, 8... Adhesive layer, 9... Adhesive layer, 10... Lid, 11...
...Heat sealable laminate, 12...Resin ring, 13...Metal foil substrate, 14...Heat sealable resin layer, 15...Resin protective coating layer, 16...Contents having autogenous pressure, 17... ...Holder, 18
... Heating and cooling head, 19 ... High frequency induction heating coil, 20 ... Cooling medium outflow nozzle, 21 ...
Normally closed solenoid valve, 22... Refrigerant inlet, 23... Refrigerant outlet, 24... Seal machine, 25... Fluid cylinder.

Claims (1)

[Scope of Claims] 1. A container comprising a circumferential side wall, a bottom portion continuous to the lower end of the side wall, and a heat-sealing circumferential portion continuous to the upper end of the side wall, and at least the inner surface of the container and the circumferential portion should be heat-sealed. A container body whose surface is made of crystalline propylene resin, a lid made of a laminate of metal foil and a heat sealant layer of crystalline propylene resin, and a space between the circumferential part of the container body and the lid. The crystalline propylene resin in the heat sealed portion of the sealed portion is expressed by the following formula: Rc=C ₁ /C ₂ ×100 where C ₁ is the crystalline propylene resin. Heat of fusion in the first strand in a differential calorimeter
cal/g, and C ₂ represents the heat of fusion cal/g of the same resin in the second run. An internal pressure heat-sealed package characterized by being suppressed to a crystalline state with a heat of fusion ratio (Rc) defined as 95% or less. 2. A container comprising a circumferential side wall, a bottom connected to the lower end of the side wall, and a heat-sealing flange connected to the upper end of the side wall, and at least the inner surface of the container and the surface of the flange to be heat-sealed are made of crystalline propylene resin. The flange portion is engaged with a lid body made of a laminate of metal foil and a heat sealant layer of crystalline propylene resin, and the flange portion and the lid body are filled with a content having a self-generating pressure. The crystalline propylene resin in the heat-sealed part is brought into contact with a cooling medium just before or after the crystalline propylene-based resin in the heat-sealed part reaches the heat-sealed temperature, and the crystalline propylene-based resin in the heat-sealed part is , so that the crystalline state is such that the heat of fusion ratio (Rc) defined by the above formula is 95% or less,
A method for producing an internal pressure heat-sealed package characterized by supercooling and solidifying under pressure due to heat conduction of the lid. 3. The crystalline propylene resin for heat sealing the container body flange is suppressed to a crystalline state in which the heat of fusion ratio (Rc) defined by the above formula is 95% or less. Claim 2 Method described.