JPH0780502B2 - Heat seal container - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sealing container made of a thermoplastic resin as a constituent material, and more specifically to a heat-sealing having a combination of heat resistance and low-temperature heat-sealing property. Regarding the container.

(Prior art) Thermoplastic polyesters such as polyethylene terephthalate (PET) have excellent physical properties such as mechanical strength, creep resistance, impact resistance, and transparency, and are less extractable by the content, and the flavor of the content. It has excellent retention (flavor retention) and is an excellent container material for foods. Pins made by stretch blow molding of this and containers made of a laminate using this are food-filled sealed containers. Has been put to practical use as.

One of the advantages of containers made of thermoplastic resin is that they can be easily sealed by heat sealing (heat sealing), but heat sealing containers using PET as the inner surface material are still commercially successful. The melting point of PET is about 260 ℃
This is because the PET layer is crystallized during heat-sealing and it is difficult to form a heat-sealing portion having sufficient strength.

In order to improve this drawback, Japanese Patent Publication No. Sho 34-34180 discloses that a crystalline saturated polyester is placed between adherends and is heated to a temperature higher than the melting point to melt it, or the crystalline saturated polyester is melted. After being heated and melted as described above and placed between the adherends, the crystalline saturated polyester is rapidly cooled with a refrigerant of 60 ° C. or less to rapidly pass between 220 ° C. and 67 ° C. A method has been proposed, and in JP-A-62-53817, at least an interface to be sealed has a plurality of portions of a container-forming material formed of thermoplastic polyester, and the outer surface of the portion is made of polyester. While maintaining the temperature lower than the crystallization temperature, the seal interface of the part and its vicinity are heated by internal heat generation so as to reach the fusion temperature and pressure-welded, and then the temperature of the seal interface is melted within 1.0 seconds after melting. Heat dissipation Preparation of a container having a heat-sealed portion has been proposed, characterized in that to pass more crystallization temperature region.

(Problems to be Solved by the Invention) The proposal in the above-mentioned prior art is
For the purpose of suppressing the crystallization of the PET layer and thereby increasing the strength of the heat-sealed part, even if it is satisfactory, the temperature of the polyester heat-sealed interface is
It is still unsatisfactory in that it needs to reach above the melting point of PET.

In particular, it is known that the above-mentioned various properties of PET are remarkably improved by oriented crystallization, and the barrier property and heat resistance to various components are improved. However, it is known that the orientation-crystallized or thermally crystallized PE is
At T, the heat seal temperature becomes extremely high, causing thermal decomposition and thermal deformation of the container material, making it difficult to cool the heat seal part, making commercial heat seal extremely difficult. It will be

Such a problem is similarly observed not only in the case of PET but also in the case of the thermoplastic resin inner surface material in which the melting point of the resin itself is high and the resin is crystallized by the molecular orientation or is thermally crystallized.

Therefore, it is an object of the present invention to provide a heat-sealed container in which the above-mentioned drawbacks of the prior art are eliminated and which has an excellent combination of low-temperature heat-sealing property and heat resistance.

Another object of the present invention is to provide a heat-sealed container capable of forming a stable and high-strength seal portion by low-temperature heat-sealing for a short time, and further capable of withstanding the high-temperature sterilization such as retort sterilization. It is in.

Still another object of the present invention is that the container itself has excellent heat resistance, and even when the contents are sterilized by retort or heated by an electronic oven, an oven toaster or the like, extraction of the inner surface material into the contents. The object is to provide a heat-sealed container in which the above problems are significantly suppressed.

(Means for Solving the Problems) According to the present invention, in a heat-sealing hermetically-sealed packaging container formed by heat-sealing a pair of packaging materials on opposite sides thereof, at least one of the packaging materials is a crystal. The melting temperature in the state is composed of a thermoplastic resin having a temperature of 200 ℃ or more and has an inner surface layer that is oriented crystallized or heat crystallized, and in the heat seal portion of the inner surface layer, the thickness of the inner surface layer from the heat seal surface Provided is a heat-sealed hermetically-sealed packaging container having a low-temperature heat-sealing property, which has a thermoplastic resin portion which is substantially amorphized or low-crystallized with a minute thickness extending in the middle of the direction.

(Operation) The heat-sealing hermetically-sealed packaging material of the present invention is formed by heat-sealing a pair of packaging materials on both sides thereof facing each other. At least one of the packaging materials has the following inner surface layer. It has a remarkable feature. First, the inner surface layer is obtained as a melting temperature in a crystalline state (a crystal melting peak temperature in a differential scanning calorimeter (DSC) ... M
p) must be above 200 °, especially between 200 and 400 ° C. The crystal melting temperature of the inner surface layer resin is defined in the above range from the viewpoint of heat resistance of the inner surface layer of the container, and the container of the present invention is heat sterilized such as retort sterilization in a state where the contents are filled. Or in addition, it is applied to cooking with a microwave oven or an oven and a star, etc. in a state of being filled with the contents, which prevents thermal deformation, strength reduction and extraction or elution tendency of the contents during heating. In order to do so, it must have a crystal melting temperature in the above range.

Next, at least the thermoplastic resin forming the inner surface layer must be crystalline, and the inner surface layer must be actually oriented or thermally crystallized. Oriented crystallization and thermal crystallization are the same in terms of crystallization, whereas the former case has three-dimensional crystal anisotropy.
The latter case is different only in that the crystal is isotropic in three dimensions like a spherulite. At least the inner surface layer of the heat-sealed container of the present invention has a thermally stable structure and improved heat resistance as compared with the case where the resin is amorphous because the resin is highly crystallized. , More rigid,
The properties required for the container, such as creep resistance, gas barrier property, and extraction resistance, are improved.

The degree of crystallinity of a thermoplastic resin, that is, the degree of crystallinity, can be generally determined by the density method (density by the density gradient tube method), published by Kyoritsu Shuppan Co., Ltd. II ”, page 305, from formula (6.3), In the formula, ρ is the density of the measured resin sample (g / cm ³ ), ρ _a is the density of the completely amorphous resin (g / cm ³ ), and ρ _c is the density of the completely crystalline resin (g / cm ^3). ), X _cv is the crystallinity (%) of the measured resin sample.

For example, in the case of PET, the values of ρa = 1.335 (g / cm ³ ) and ρc = 1.455 (g / cm ³ ) are generally used.

Given in. In the container of the present invention, if the crystallinity (X _cv ) of the inner surface layer is 20% or more, satisfactory results can be obtained with respect to the above characteristics.

By the way, as described above, in the case where the inner surface layer resin has a high melting point and is highly crystallized, the heat sealing property of the container is high, even if very satisfactory results are obtained with respect to the heat resistance of the container. It becomes extremely poor, and the heat seal strength will never reach a satisfactory level. The heat-sealing portion of the inner surface layer of the container of the present invention is provided with a resin portion that is substantially amorphized or low-crystallized with a minute thickness extending from the heat-sealing surface to the middle in the thickness direction of the inner surface layer. It is the third characteristic and the remarkable one. That is, by providing a substantially amorphized or low-crystallized resin portion in the heat seal portion, at a temperature lower than the melting point (Mp) of this resin, generally at a temperature of Mp-100 ° C to Mp-10 ° C. Not only heat sealing becomes possible and low temperature sealing becomes possible, but also a sealing strength of high sealing strength with a sealing strength of 1.5 kg / 15 mm width or more can be formed, and this heat sealing portion is, for example, at 120 ° C. for 30 minutes. The retort sterilization of can be sufficiently endured. It is also important that the substantially amorphized or low-crystallized resin portion has a minute thickness extending from the heat-sealing surface to the middle of the thickness direction of the inner surface layer. In the case of being low-crystallized, the heat-sealing portion is thermally deformed and the seal strength and the heat resistance of the heat-sealing portion are significantly lowered. By providing the non-crystallized or low-crystallized portion only in a part in the adjacent thickness direction and leaving the oriented crystallization or heat-crystallized portion in the other part in the thickness direction, the low temperature seal can be achieved without the above-mentioned drawbacks. And the easy sealing property can be obtained.

Since the degree of crystallinity of a resin portion that has been amorphized or low-crystallized exists in a very small thickness, it is difficult to measure it by the above-mentioned density method (density gradient tube method). The density distribution is measured by the laser Raman method using the characteristic absorption band depending on the degree, and the crystallinity is calculated from this density based on the above formula (1). For example, in the case of polyester,
This characteristic absorption band is a wave based on stretching vibration of C = 0.
It is a peak at 30 cm ^-1 , In the formula, Δν _1/2 is the full width at half maximum of the above characteristic absorption peak (cm ^-1 ).
Where k ₁ and k ₂ are the half-width values for this resin on the vertical axis,
It is an intercept and a gradient obtained from a calibration curve graph with density as the horizontal axis.

The density (ρ) can be obtained based on In the present invention, the amorphized or low crystallized portion has a crystallinity (X _cv )
Is preferably 20% or less.

Incidentally, in the present invention, the inner surface layer, the entire (single layer) including the inner surface layer may be composed of a resin having a crystallization structure with the melting temperature described above, or, of the laminated structure,
This means that only the inner surface layer may be composed of the above resin.

(Preferable Aspects of the Invention) In FIGS. 1-A and 1-B showing an example of the heat-sealed container of the present invention, the container body 1 has a cup shape (FIG. 1-A) to a tray shape (first). -Fig. B), and has a short body portion 2, a closed bottom portion 3 connected to the lower end portion of the body portion, and a heat-sealing flange portion 4 connected to the upper end portion of the body portion. A heat seal lid 12 is provided separately from the container body 1, and heat sealing is performed between the heat seal lid 12 and the container flange portion 4.

In this specific example, the entire container body 1 is made of a resin having a crystal melting temperature (Mp) of 200 ° C. or higher and which is oriented or thermally crystallized. In FIG. 2 showing the heat sealing flange portion 4 of the container body 1 in an enlarged manner, the flange portion 4 has a heat sealing surface 5, and the heat sealing surface 5
To the middle of the flange portion 4 in the thickness direction, a substantially amorphous or low-crystallized resin portion 6 having a minute thickness d is provided, and oriented crystallization or thermal crystallization is provided below the resin portion 6. There is a resin portion 7 that has been removed. The substantially amorphous or low-crystallized resin portion 6 is provided only on the portion to be heat-sealed (the whole or a part of the flange portion), and the other portion of the resin container 1, for example, the inner surface 8 is the orientation container 1. It is to be understood that the other parts, such as the inner surface 8, are composed of oriented or thermo-crystallized resin.

The container shown in FIGS. 1 and 2 is an example of the container made of the resin single layer, but the container can be a container having a multilayer laminated structure. In FIG. 3 showing an example of the multilayer container, The multi-layer container 1 includes a gas barrier intermediate layer 9 and resin inner and outer layers.
It consists of 10a and 10b. At least the inner layer 10 of the inner and outer layers
a, preferably both resin layers 10a, 10b are formed from resin layers satisfying the requirements of the present invention, and the heat seal portion has a heat seal structure similar to that shown in FIG. 2 of the present invention. 6,7 are formed. Gas barrier intermediate layer 9
As the material, a metal foil or a gas barrier resin described later is used.

In FIG. 4 showing another example of the container, the container is composed of two pieces of sheet-like packaging materials 11a and 11b facing each other in a bag shape, and a heat-sealed bag-like container around the periphery of the container. 11a and 11b also consist of resin inner and outer layers 10a and 10b and a gas barrier intermediate layer sandwiched therebetween. The same heat seal structure 6 as described in FIG. 2 is applied to the heated parts of these sheets 11a and 11b.
7 is formed.

Of course, in the present invention, the heat-seal lid 12 (Fig. 1)
It should be understood that, however, it may have the laminated structure and the heat seal part structure shown in FIG.

In the present invention, as the crystallizable resin having a crystal melting temperature (Mp) of 200 ° C. or higher, polyethylene terephthalate (PET), polybutylene terephthalate (PBT),
Mention may be made of thermoplastic polyesters derived from dibasic aromatic carboxylic acids such as polyethylene naphthalate (PEN) and diols. This polyester is a dibasic acid such as isophthalic acid, adipic acid, decanecarbenoic acid, and succinic acid, and diols such as diethylene glycol, triethylene glycol, propylene glycol, and neopentanediol as long as the essence of the polyester is not impaired. However, these copolymerization components are preferably present in an amount of 20 mol% or less based on the acid component or the diol component.
The polyester used is generally 0.4 to 1.8 dl / g, especially 0.
It is preferable to have an intrinsic viscosity [η] of 5 to 1.5 dl / g.
Polyethylene terephthalate is particularly preferred for the purposes of the present invention.

The resin used as the inner surface layer is not limited to polyester as long as the above conditions are satisfied. For example, nylon 6, nylon 6,6, nylon 6,8, nylon 4,6, and other aliphatic nylons; polyamides derived from aromatic dibasic acids and aliphatic diamines, such as polyhexamethylene terephthalamide, Polyhexamethylene terephthalamide / isophthalamide, polyoctamethylene terephthalamide, polybutylene terephthalamide; polyamides derived from aliphatic dibasic acids and araliphatic diamines, eg polyxylylene adipamide, polyxylylene Sebacamide; etc. are used. These nylons preferably have a relative viscosity (ηrel) measured in 98% sulfuric acid at a concentration of 1.0 g / dl and a temperature of 20 ° C. of 1.6 to 3.5, particularly 2.0 to 3.0.

Of course, these resins may be used alone, or may be used in a blend of two or more kinds within the range satisfying the above-mentioned conditions. It goes without saying that a curable resin, a crystallization nucleating agent, a coloring agent, a filler, a powdery or fibrous reinforcing agent, a lubricant, an antiblocking agent, an ultraviolet absorber, an antioxidant and a heat stabilizer can be added.

Molding from the resin to a material for forming a container includes, for example, extrusion molding, injection molding, compression molding, hollow molding, biaxial stretch blow molding, pressure molding from a sheet or film, plug assist molding, stretch molding, press molding, It is carried out by any forming means known per se, such as drawing, drawing and ironing.

The oriented crystallization of the resin is carried out by stretching the molded body in at least uniaxial direction, preferably biaxially, in at least uniaxial direction in the above-mentioned molding step or stretching step following the molding step, and if necessary, this molecular This is done by heat-fixing the orientation. The effective stretching ratio is in the order of 2 to 15 times, particularly 3 to 13 times in terms of area ratio. Although heat setting differs depending on the resin, it is desirable to carry out at 150 ° C. or higher for polyester and 180 ° C. or higher for polyamide.

The thermal crystallization of the resin is performed by holding the material for forming the container at the crystallization temperature of the resin. The crystallization temperature range is peculiar to the resin used, but it is generally a temperature above the glass transition point (Tg) of the resin and below the melting point (Mp), and particularly in the range of Tg + 20 ° C to Mp-20 ° C. Appropriate. Although the crystallization rate depends on the crystallization temperature, the presence or absence of an engraving agent, and the crystallization atmosphere, heat treatment for 1 to 2 minutes is generally suitable. With the progress of crystallization, spherulites grow, the transparency of the resin is lost, and white turbidity progresses. Therefore, the end point of the heat treatment can be known from this change.

As shown in the figure, the container material of the present invention can be composed of a laminate of a high melting point and high crystalline resin and another material. For example, as the metal foil or metal sheet used in the production of this laminate, an aluminum foil, an iron foil, a steel foil, a tin foil or an aluminum plate, a surface-treated steel sheet similar to the foil, or the like can be given. The lamination of the sheet and the resin can be carried out by an extrusion coating method, a dry lamination method, a sandwich lamination method, or the like by interposing an adhesive between them or by utilizing the thermal adhesiveness of the resin.

Further, as other materials, high gas barrier resin, for example, ethylene-vinyl alcohol copolymer, vinylidene chloride copolymer, high nitrile resin, high barrier polyester, high barrier nylon resin and the like can be mentioned. It can also be obtained by directly molding into a material for forming a container by a laminate with this high gas barrier resin, a coextrusion molding method, a coinjection molding method, or the like, or by any of the lamination methods described above.

Molding into a container material of a laminate and oriented crystallization or thermal crystallization can be performed in the same manner as in the case of the container material having a single layer structure described above, but according to the present invention, oriented crystals of a high melting point highly crystalline resin It should be understood that the crystallization or thermal crystallization can be carried out at any stage, for example before lamination, after lamination before molding, during molding or at any stage after molding.

Examples of the container material include an inner surface-covered seamless squeezed or squeezed ironing metal can, a plastic can, a cup-shaped container, a tray-shaped container, a bottle-shaped container, a tank-shaped container, a flexible pouch, and a heat-seal lid. Either one or both may have the heat seal structure defined in the present invention.

In the present invention, the thickness of the substantially amorphized or low-crystallized resin portion existing in the heat-sealed portion is equal to 1 of the thickness of the oriented crystallized or heat-crystallized resin layer in the vicinity of this portion.
It should have a thickness of -30%, especially 3-20%, most preferably 5-10%. That is, if the thickness of the amorphized or low-crystallized portion is smaller than the above range, it tends to be difficult to obtain low-temperature sealability or easy sealability. Tends to decline.
The thickness of the portion is preferably at least 1 μm or more, and particularly preferably 2 μm or more.

The width of the substantially amorphized or low-crystallized resin portion provided in the heat seal portion can be arbitrarily changed, but generally 1
The width is preferably 10 to 10 mm, particularly 2 to 6 mm.
The present invention is characterized in that even if the heat seal width is small as described above, it is possible to form a heat seal having excellent sealing reliability and a seal strength of 1.5 kg / 15 mm width. An easily openable heat seal can be formed by suppressing the width of the heat seal portion to 5 mm or less. Of course, the amorphized or low-crystallized resin portion may be provided as one in the portion to be heat-sealed, or may be provided as a plurality at a small interval.

To provide an amorphized or low-crystallized resin portion in the portion of the inner surface layer to be heat-sealed, the orientation-crystallized or heat-crystallized resin is a very limited portion from the surface to the middle in the thickness direction. Is rapidly heated to a temperature equal to or higher than the melting point within a short time, and is rapidly cooled to a temperature lower than the crystallization temperature when the heating is stopped.

For such limited rapid heating and rapid cooling, for example, scanning irradiation of a carbon dioxide gas laser beam can be used. In this case, by changing the output and scanning speed of the laser beam, amorphization or low crystallinity is achieved. The thickness of the chemical resin portion can be controlled. Further, the width can be controlled by changing the diameter of the laser beam. For more limited rapid heating and rapid cooling, it is possible to use a combination of a forcibly cooled high frequency induction heating coil and a conductor mold having a heat seal pattern. In this case, the mold is rapidly heated by the energization of the coil, the resin that comes into contact with the coil is rapidly heated, and the energization is interrupted to rapidly cool the resin through the mold. Thus, the thickness is controlled by controlling the energization time.

In the heat-sealing container of the present invention, a heat-sealing mechanism known per se, for example, a hot plate, an impulse seal, an induction heating seal, an ultrasonic sealing, a high-frequency induction heating sealing can be used to perform the heat sealing, but in any case. The outstanding feature is that heat sealing can be performed at a temperature lower than the melting point (Mp) of the high melting point and high crystallization resin.

(Effects of the Invention) According to the present invention, at the time of heat-sealing a pair of materials on both surfaces facing each other, at least one inner surface layer of at least one of the materials has a crystal melting temperature of 200 ° C. or higher and is oriented and crystallized. A thermoplastic resin which is a heat-crystallized resin and is substantially amorphized or low-crystallized in the heat-sealing portion of the inner surface layer with a minute thickness extending from the heat-sealing surface to the middle in the thickness direction of the inner surface layer. By having the portion, it was possible to provide a heat seal container having a combination with low temperature heat sealability. Furthermore, this container can form a stable and high-strength seal portion by low-temperature heat sealing for a short time, and this seal portion can withstand high temperature sterilization such as retort sterilization, and the container itself is heat resistant. In addition to being excellent, it has an advantage that even when the contents are sterilized by retort or cooked with a microwave oven or an oven toaster, extraction of the inner surface material into the contents is significantly suppressed.

(Example) Example 1, Comparative Examples 1, 2, 3 Polyethylene terephthalate (density 1.34 g / cm ³ ), crystallinity 4.5%, intrinsic viscosity 0.61, thickness 0.7 mm) to 210 mm × 210
A mm blank was cut out and a round container having an outer diameter of 80 mm, an inner diameter of 66 mm, a flange width of 7 mm, a height of 35 mm, and a full-filled volume of 85 cc was formed by a thermoforming method. At this time, the density and crystallinity of the flange were measured with a density gradient tube 1.
It was 376 cm ³ and 36.1%. The melting temperature was 255 ° C as measured by a differential scanning calorimeter (DSC) at a heating rate of 20 ° C / min.

Next, carbon dioxide laser oscillator (Toshiba Corporation, 1.2K)
w Carbon dioxide laser oscillator, model: TOSLASERCO12-PSSB,
Method; high-speed axial flow type), a laser beam with a diameter of about 18 mm was used as a defocused beam from a condenser lens with a focal length of 127 mm, and a beam with a spot diameter of about 7.5 mmφ was obtained on the irradiation surface. Further, as described above, the round container is rotated at a peripheral speed of 60 m / min, the time required for one rotation (about 0.22 seconds), output 25
A laser beam of 0 W was applied to the container flange portion.

A cross section of this container flange was cut out with a microtome and observed under a polarizing microscope. The part that is not affected by the laser beam is whitened by thermal crystallization during molding of the container, while the laser irradiation part is transparent and the irradiation part can be easily identified. Here, in order to clarify the difference between the laser-irradiated part and the non-irradiated part, a micro Raman spectroscopic device was used to
The laser beam is focused to a beam with a spot diameter of 1 μm by a 100 × objective lens, and the surface layer of the cross section of the irradiated part that appears transparent under a polarizing microscope and the part that is whitened by thermal crystallization without being affected by the laser beam are irradiated. Then, the Raman intensity of each was measured. Further, by utilizing the relationship that the Raman intensity due to the stretching vibration of the carbonyl group at 1730 cm ^-1 is inversely proportional to the density, both densities were obtained from the above equation (2). Each density ρ (g / cm ³ ) and the crystallinity X _cv obtained by substituting this density into the equation (1) are as shown in Table 1, and the laser irradiation portion is low crystallized. I understand. still,
The following values were used for the intercept k _{1 and the} gradient k ₂ used when the density was calculated by the equation (2).

k ₁ = 114.37 k ₂ = −75.95 Furthermore, a cross-sectional photograph of this sample was taken under a polarizing microscope,
From the photograph, the thickness ratio of the low crystallized portion to the thickness of the flange resin was calculated to be about 7%,
The irradiation width was a circular ring with a width of about 2 mm.

As the lid material, the bright surface of soft aluminum foil with a thickness of 50 μm was coated with epoxy / urea-based paint as the overcoat material and baked at 230 ° C for 60 seconds. After the treatment, an epoxy / phenolic coating material containing a bisphenol A type epoxy resin and a resole type phenol / formaldehyde resin composed of a binuclear component in a weight ratio of 80:20 (specific gravity d ₁ = 1.20 g / cm ³ , A solid content of 30%) was applied by a gravure coater to a coating amount of about 40 mg / dm ^2, and dried at 120 ° C. for 60 seconds for the purpose of making the surface tack-free. Further, a copolyester solution is applied thereon so that the coating amount is about 90 mg / dm ² , and the coating is cured,
And for the purpose of removing the solvent in the copolyester solution 23
Baking was performed at 0 ° C. for 60 seconds.

A round lid material having a diameter of 85 mm and having a knob for opening was punched out from the coating material thus created.

Next, fill the round container with cream corn soup
100 pieces were filled at 65 ° C. and a filling amount of 70 cc, and the lid material was heat-sealed under the conditions shown in Table 2 by 50 pieces each for heat-sealing times of 1 second and 2 seconds. At this time, the distance from the soup surface to the flange surface was measured and found to be about 5 mm. In order to check the sealing performance of 100 containers thus filled and sealed, 15 cylinders were used for each heat-sealing time, and a cylindrical weight of 70 mm in diameter and 20 kg was placed on the sealed lid for 1 minute. Then, a compression resistance test was conducted by a method of checking whether or not the contents leaked. 15 each (total 30
None of the samples (1) had leaked contents, and the hermeticity was perfect. In addition, 10 pieces each (total 20 pieces)
From the seal part of the sample
Cut 15 mm wide strips into 4 pieces per sample, 40 pieces in total, sandwich the lid side of the strip in the upper chuck and the side wall of the cup in the lower chuck, and pull it up and down at a speed of 300 mm / min. The heat seal strength from the inside was measured, and the average value was obtained. As shown in Table 2, even when heat-sealing at a temperature of 200 ° C, which is 60 ° C lower than the melting point of PET, the heat-sealing strength between the container body and the lid material is 2.3 kg / 15 on average in a heat-sealing time of 2 seconds.
mm, and peeling was easily possible. Also, after performing retort sterilization treatment on the remaining 50 pieces at 120 ° C for 30 minutes, the same compression resistance test was performed on 15 pieces (total 30 pieces) and the remaining 10 pieces (total 20 pieces) on the container body. The heat seal strength with the lid material was measured by the same method. The heat-sealing strength was 1.9 kg / 15 mm on average for a heat-sealing time of 2 seconds, and when the lid member was opened from the knob portion of the opening portion, peeling was easily possible.

In addition, as Comparative Example 1, the crystallinity X _cv = 3 of the heat seal part
At 100% of the containers, which did not have a low crystallization part as obtained in the present invention at 7.2%, heat sealing was attempted with the same lid material as above, and the same test was tried. Even before the retort treatment, leakage of the contents was observed from most of the samples, and the heat seal strength was very low, about 1.0 kg / 15 mm at 200 ° C for 2 seconds. Further, after the retort treatment, leakage was observed in all, and the hermeticity could not be secured.

Next, as the comparative example 2, the lid member was heat-sealed at a melting point of PET or higher with respect to the container used in the comparative example 1, and the surface temperature was immediately adjusted to 10
A test was conducted in which a cooling bar set at ℃ was pressed against the seal portion for rapid cooling. In this case, the deformation of the flange portion and the foaming of the flange surface during heat sealing were severe, and the sealing strength was obtained, but the variation was severe, and the contents were leaked over several times. Further, leakage was observed even after the retort treatment, and the sealing performance could not be secured.

Further, as Comparative Example 3, the crystallinity of the heat seal part is 3.3.
We tried heat-sealing under the same conditions as above for a container that is not heat-crystallized, but the sealing strength is obtained, but the flange part deforms significantly during sealing and the container also deforms during retort sterilization. Vigorously container practicality,
It lacked heat resistance. The heat seal strength results of these Comparative Examples 1, 2, and 3 are also shown in Table 2.

Example 2 and Comparative Example 4 A 25 μm biaxially oriented polyethylene terephthalate film (density 1.40 g / cm ³ , crystallinity 56.3%, melting temperature 2) on one side of a rolled steel foil of 75 μm having chromate surface treatment layers on both sides.
(55 ° C) was coated with a yellow-colored epoxyphenol-based paint on the other surface of the laminated plate with the epoxy / phenolic paint applied, and then the paint was cured in an oven at 205 ° C for 10 minutes. . Next, the steel foil is punched into a blank with a blank diameter of φ140 mm, so that the film is on the container inner surface side by a drawing method using an elastic punch, height 30 mm, outer diameter 78 mm, inner diameter 65 mm, corner R1 mm,
A round container having a full-filled volume of 85 cc with its flange curled outward was formed. At this time, the density and crystallinity of the flange were almost the same as those of the film before lamination.

Next, a carbon dioxide gas laser was applied to the flange portion of the container under the same conditions as in Example 1. When the density of the surface layer in the cross section of the irradiated part was measured by the laser Raman method, the density was 1.349 g / cm ³ , and the crystallinity was 12.6%. The values used in Example 1 were used for the intercept k ₁ and the gradient k ₂ used at this time. Further, the thickness ratio of the amorphized portion to the film thickness of the flange portion was measured to be about 8%,
The irradiation width consisted of a circular ring with a width of about 2 mm.

Further, 100 round containers were filled with cream corn soup, and the lid material used in Example 1 was heat-sealed under the conditions shown in Table 3, and the heat-sealing strength was measured by the same evaluation method as in Example 1. did. The heat seal strength was 1.8 kg / 15 mm after a heat seal time of 2 seconds, and there was no leakage of the contents. In addition, the heat-sealing strength between the container body and the lid after the retort sterilization treatment was measured to be 2.5 kg / 15
mm, and when the lid material is opened from the opening knob,
It was possible to peel off easily. Also, there was no leak at this time.

As Comparative Example 4, the heat-sealing strength of a container not subjected to laser irradiation was also measured, but the sealing strength was 1.0K.
It was less than g / 15 mm and could not maintain the hermeticity during or after retort treatment.

Example 3 and Comparative Example 5 A 75 μm rolled steel foil having chromate surface-treated layers on both sides was coated with a yellow colored epoxyphenol-based coating on one side and cured at 205 ° C. for 10 minutes in an oven. 25 μm biaxially oriented polyethylene terephthalate film (density 1.40 g / cm ³ , crystallinity 56.
3%, melting temperature 255 ° C.) were laminated via a urethane adhesive, and the adhesive was cured at 50 ° C. for 3 days to prepare a laminated plate. The laminated board, blank diameter φ140m
Punch it into a blank of m and draw it with a height of 30 so that the film is on the inner surface of the container by the drawing method using an elastic punch.
mm, outer diameter 78 mm, inner diameter 65 mm, corner R1 mm, full capacity
A round container was formed in which the flange of 85cc was curled to the outside. At this time, the density and crystallinity of the flange are
It was almost the same as that of the film before lamination.

Next, a carbon dioxide gas laser was applied to the flange portion of the container under the same conditions as in Example 1. When the density of the surface layer in the cross section of the irradiated part was measured by the laser Raman method, the density was 1.349 g / cm ³ , and the crystallinity was 12.6%. The values used in Example 1 were used for the intercept k ₁ and the gradient k ₂ used at this time. Further, the thickness ratio of the amorphized portion to the film thickness of the flange portion was measured and found to be about 8%, and the irradiation width formed a circular ring of about 2 mm.

Further, 100 round containers were filled with cream corn soup, the lid material used in Example 1 was heat-sealed under the conditions shown in Table 4, and the heat-sealing strength was measured by the same evaluation method as in Example 1. did. The heat seal strength was 1.8 kg / 15 mm after a heat seal time of 2 seconds, and there was no leakage of the contents. In addition, the heat-sealing strength between the container body and lid after the retort sterilization treatment was measured to be 2.4 kg / 15.
mm, and when the lid material is opened from the opening knob,
It was possible to peel off easily. Also, there was no leak at this time.

As Comparative Example 5, the heat-sealing strength of a container not subjected to laser irradiation was also measured, but the sealing strength was 1.0K.
It was less than g / 15 mm and could not maintain the hermeticity during or after retort treatment.

Example 4 A high frequency oscillator having an oscillation frequency of 400 KHz and an oscillation output of 5 KW was used on the flange portion of the round sealed container made of polyethylene terephthalate used in Example 1, and the oscillation time was 0.3 sec and the applied pressure was 5.
A Teflon-coated 0.24 mm steel plate was induction-heated under the conditions of 3 Kg / cm ² , a pressure cooling time after pressurization of 0.3 sec, and a voltage of 110 V, and the container flange portion was reformed by heat conduction. When the density of the surface layer in the cross section of this modified portion was measured by the laser Raman method, the density was 1.352 g / cm ³ , and the crystallinity was 15.2%. The values used in Example 1 were used for the intercept k ₁ and the gradient k ₂ used at this time. Further, the thickness ratio of the low crystallized portion to the thickness of the flange resin was measured and found to be about 5%.

Furthermore, 100 round containers were filled with cream corn soup, the lid material used in Example 1 was heat-sealed under the conditions shown in Table 5, and the heat-sealing strength was measured by the same evaluation method as in Example 1. did. The heat-sealing strength was 2.3 kg / 15 mm after the heat-sealing time of 2 seconds, and there was no leakage of the contents. In addition, the heat-sealing strength between the container body and the lid material after the retort sterilization treatment was measured and found to be 2.1 kg / 15.
mm, and when the lid material is opened from the opening knob,
It was possible to peel off easily. Also, there was no leak at this time.

Examples 5 to 10 and Comparative Example 6 In Example 1, samples were prepared by changing the irradiation output of the carbon dioxide gas laser to change the thickness of the amorphous portion as shown in Table 6.

The cross section of the flange portion of this sample was cut with a microtome and the amorphous portion was observed with a polarizing microscope. As shown in Comparative Example 5, when the output is less than 200 W, it is difficult to observe the amorphous part, and when a heat sealing with the container body was attempted with the same lid material as used in Example 1, the sealing strength was extremely high. It was weak and could not secure hermeticity.

On the contrary, at an output of 350 W or more, as shown in Examples 8 to 10, the thickness ratio of the amorphous part has a thickness ratio of 13% or more with respect to the thickness of the flange heat-crystallized resin layer, The foaming phenomenon occurs in the layer. Therefore, the peel strength after heat sealing becomes unstable, which is not preferable.

Under the irradiation conditions as in Examples 5 to 7,
By creating an amorphous part with a thickness ratio of about 10%, there is no foaming of the surface layer and the heat sealing strength with the lid material is 2.3 kg /
It was stable at 15 mm, and was capable of retort resistance and subsequent peeling. Further, when the density ρ (g / cm ³ ) of the surface layer portion in the cross section of the irradiated portion before the retort treatment was measured by the laser Raman method as in Example 1, there was some variation with each sample, but ρ = 1.351 g / cm ³ , and the crystallinity X _cv was × _cv = 14.4%.

Example 11 Biaxially oriented polyethylene terephthalate film having a thickness of 16 μm and 25 μm (both having a density of 1.40 g / cm ³ and a crystallinity of 56.3).
%, Melting temperature 255 ° C) with urethane adhesive 20
It was laminated on both sides of a μm aluminum foil.

The portion to be sealed was polyethylene terephthalate having a thickness of 25 μm, and the portion was irradiated with a carbon dioxide laser under the same conditions as in Example 1. When the density of the surface layer in the cross section of the irradiated part was measured by the laser Raman method, the density was 1.349 g / cm ³ , and the crystallinity was 12.6%. The values used in Example 1 were used for the intercept k ₁ and the gradient k ₂ used at this time. Further, the thickness ratio of the low crystallized portion to the film thickness was measured and found to be about 8%.

Next, face the irradiated parts together under the conditions shown in Table 7, and measure a total of 50 bags on each of the three sides of the outer circumference for each heat-sealing time.
100 bags heat-sealed and bag-shaped container (pouch) 130 mm x 170 mm
It was created. 100 pouches of this pouch were filled with cream corn soup under the same conditions as in Example 1, and the open ends were heat-sealed under the same conditions as the heat-sealing of the three outer peripheral sides. Thereafter, 15 bags each (30 bags in total) were subjected to the same compression resistance test as in Example 1 to check the contents for leakage, but none of them resulted in leakage. Further, from 10 bags (20 bags in total), 4 points per bag, 40 points in total, 15 mm wide strips are cut out, the heat seal strength is measured by the T peel method at a pulling speed of 300 mm / min, and the average value is obtained. It is shown in Table 7.

Furthermore, the remaining 50 pouches were subjected to retort sterilization treatment at 120 ° C. for 30 minutes, and the same compression resistance test and heat seal strength as above were measured, and the results are also shown in Table 7. Further, after the retort treatment, no damage was found on the seal portion, and the sealing property was perfect.

In addition, it was tried to make a pouch with a laminated sheet having no low crystal part, but the adhesion between polyethylene terephthalates is very weak below the melting temperature, making the pouch difficult, and a compression resistance test before and after retort treatment,
It was impossible to measure the heat seal strength.

[Brief description of drawings]

FIGS. 1-A and 1-B are perspective views showing a cup-shaped container and a tray-shaped container of the present invention, respectively, and FIG. 2 is an enlarged sectional view of a heat-sealing flange portion. FIG. 3 is a sectional view showing an example of a multi-layer container, and FIG. 4 is a sectional view showing another example of a multi-layer container. 1 is a container or a container body, 2 is a body, 3 is a bottom, 4 is a heat-sealing flange, 5 is a heat-sealing surface, 6 is an amorphous or low-crystallized resin portion, and 7 is oriented crystallization or thermal crystallization. Section, 8 inner surface, 9 gas barrier intermediate layer, 10a, 10
b indicates the inner and outer layers, and 12 indicates the heat seal lid.

Claims (1)

[Claims] 1. A heat-sealed hermetically-sealed packaging container obtained by heat-sealing a pair of packaging materials on opposite sides thereof, wherein at least one of the packaging materials has a melting temperature in a crystalline state of 200 ° C. or higher. It has an inner surface layer made of a thermoplastic resin and oriented or crystallized or heat crystallized, and in the heat-sealing portion of the inner surface layer, it has a very small thickness from the heat-sealing surface to the middle in the thickness direction of the inner surface layer. A heat-sealed hermetically-sealed packaging container having a low-temperature heat-sealing property, which has an amorphous or low-crystallized thermoplastic resin portion.