JP2003062924A - Packaging material for retort - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging material for a retort which keeps taste of the content well because the odor of the packaging material is not transferred to the content even when it is used in the packaging of food, not generating the so-called orange peel and excellent in seal strength and impact resistance. SOLUTION: The packaging material for the retort comprises at least a polyethylene terephthalate film layer, a vapor deposition layer of an inorganic oxide and a film layer comprising a polyethylene film or an ethylene/α-olefin copolymer polymerized using a single site catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material for retorts, and more particularly, for retorts, which can be suitably used for packaging foods, chemicals, beverages, etc., particularly contents to be subjected to pressure heat sterilization. Regarding packaging materials.

[0002]

2. Description of the Related Art For packaging materials for foods, chemicals, beverages, etc., especially those to be subjected to heat and pressure sterilization, the packaging materials are heated and pressurized at a high temperature of about 120 ° C. in a retort. Therefore, as the function of the packaging material, (A). Heat-resistant,
(B). Seal strength, (C). Barrier properties, (D). It is desired to have impact resistance. Conventionally, in order to achieve such an object, as a film having high sealing strength and excellent heat resistance as an innermost layer of a packaging material for a retort, and a film having no odor of the packaging material itself, polypropylene (hereinafter, referred to as “P
P ”) is used. As a specific layer structure, polyethylene terephthalate (hereinafter, referred to as “PET”) / stretched nylon (hereinafter,
“ONy”) / aluminum (hereinafter “Al”) / unstretched PP (hereinafter “CPP”), PE
Laminated films such as T / Al / CPP and PET / ONy / CPP are widely used.

[0003]

However, in the conventional packaging material using PP as the innermost layer, since the PP resin itself is a crystalline resin, the impact resistance is extremely high when the homopolymer is used. Since it is low and has low transparency, it is used as a random copolymer or block copolymer with ethylene to improve impact resistance and transparency. Also,
PP is generally said to have excellent oil resistance,
When used as a random copolymer or a block copolymer with ethylene, crystallization does not occur uniformly and the oil resistance of the packaging material is not constant, so foods with a lot of oil as the content, for example, curry, Chinese as the content. When a sauce or the like is used, there is a place where the oil of the contents soaks into the packaging material and a place where the oil does not soak into it, resulting in unevenness on the resin surface, so-called yuzu, which makes the appearance unsatisfactory. Furthermore, when a barrier property is imparted as a packaging material for a retort, Al is laminated, but when Al is laminated, the unevenness of PP, which is the innermost layer, remarkably appears on the surface of Al, and the appearance is further improved as a packaging material. Becomes worse. Further, when irregularities occur in Al, cracks may occur in Al, so that the barrier properties are poor at the cracks and the barrier properties of the packaging material as a whole are lost.

The present invention was created on the basis of such drawbacks, and an object of the present invention is to have an impact resistance, to prevent the surface of the resin from being dulled, and to further improve the sealing strength. It is intended to provide a film which is expensive, has little odor of the packaging material itself, and does not impair the taste of the contents.

[0005]

[Means for Solving the Problems] In order to achieve such an object, the inventors of the present invention have conducted extensive studies and as a result, have found that ethylene or ethylene-α-olefin copolymer polymerized by a single-site catalyst is the innermost layer. As a result, the packaging material itself has excellent impact resistance, and does not cause rust on the surface of the ethylene or ethylene-α-olefin copolymer that is the innermost layer, and further, the packaging material itself has an odor. Since the odor of the packaging material itself does not transfer to the contents, the taste of the contents is not impaired, and further, it is found that a packaging material for retort having a high sealing strength of the packaging material can be obtained, It was invented in.

That is, the present invention is a packaging material for a retort, which comprises ethylene or an ethylene-α-olefin copolymer polymerized by a single-site catalyst as the innermost layer.

Further, the α-olefin of the ethylene-α olefin copolymer film polymerized by using the single site catalyst constituting the innermost layer is propylene, 1-butene,
3-methyl-1-butene, 4-methyl-1-pentene,
A retort packaging material, which is one of 1-hexene, 1-octene, and decene.

In the packaging material for a retort according to the present invention, the innermost layer is composed of ethylene or an ethylene-α-olefin copolymer polymerized by a single site catalyst, and ethylene or ethylene-polymerized by the single site catalyst. Since the α-olefin copolymer film has uniform molecular chains, the molecular weight distribution is narrow, and the comonomer content of each molecule is almost the same, so that the crystallization rate is slow and a package excellent in impact resistance can be obtained.

The ethylene or ethylene-α-olefin copolymer polymerized by a single-site catalyst is
Since the molecular chains are uniform, the molecular weight distribution is narrow, and since the comonomer contents of each molecule are almost the same, a film having excellent oil resistance can be obtained. Therefore, when oily foods are used as the contents, for example, when curry, Chinese sauce, etc. are used as the contents, there is no place where the oil of the contents soaks into the packaging material and a place where it does not soak, and the resin surface There is no unevenness on the surface, so-called yuzu, and the appearance as a package is good.

Therefore, since the surface of the inner layer does not have irregularities, even when Al is laminated, the irregularities do not occur in Al, so that cracks do not occur in Al and the barrier property as a retort packaging material is not deteriorated. .

When an ethylene or ethylene-α-olefin copolymer film polymerized using a single-site catalyst is used, the ethylene or ethylene-α-olefin copolymer film polymerized using this single-site catalyst has a molecular weight distribution. The packaging material itself has a small odor because it is narrow and has a very low content of low molecular weight substances. Therefore, even if a retort packaging material using such a film is formed and the contents are filled, the odor of the packaging material itself does not transfer to the contents and the taste of the contents is not impaired.

Further, since it is composed of an ethylene or ethylene-α-olefin copolymer film polymerized using a single-site catalyst, the ethylene or ethylene-α-olefin copolymer film polymerized using this single-site catalyst is Since the molecular chains are uniform, the molecular weight distribution is narrow, and since the comonomer contents of each molecule are almost the same, a film having excellent heat seal strength can be obtained. Therefore, a package using such a film is excellent in heat-sealing strength and a laminated film having a strong laminating strength can be obtained, so that high bag breaking strength can be obtained.

Further, since the melting point of the ethylene or ethylene-α-olefin copolymer film polymerized by using a single site catalyst can be controlled by the amount of the comonomer, a film excellent in low temperature sealing property can be obtained. That is, when the amount of comonomer is increased, the melting point is lowered, so that a film having a low temperature sealing property can be obtained. Therefore, as a package, it is possible to obtain a package excellent in low-temperature sealing property, so that the contents can be filled at high speed and the productivity is improved.

Further, the ethylene or ethylene-α-olefin copolymer film polymerized using a single-site catalyst has a narrow molecular weight distribution and good transparency, so that a clean film can be obtained and a transparent and clean package as a package. Is obtained.

When an ethylene or ethylene-α-olefin copolymer film polymerized using a single site catalyst is used, the ethylene or ethylene-α-olefin copolymer film polymerized using this single site catalyst has a molecular weight distribution. Since the content of the narrow and low molecular weight substances is very small, there is no odor transfer to the contents, and therefore, a film which is organoleptically good can be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the retort packaging material of the present invention will be described below in detail with reference to the drawings. Figure 1
As shown in FIG. 3, in the retort packaging material, if the innermost layer is ethylene or an ethylene-α-olefin copolymer film layer 1 polymerized using a single-site catalyst,
The configurations of the outermost layer and the intermediate layer are not particularly limited, and various layer configurations can be used depending on the use and purpose of the retort packaging material.

For example, the retort packaging material shown in FIG.
The ethylene or ethylene-α-olefin copolymer film layer 1 polymerized using a single-site catalyst is the innermost layer, the Al layer 2 is the barrier layer, the ONy layer 3 is the intermediate layer, and the PET layer is the outermost layer.

The retort packaging material shown in FIG. 2 has an ethylene or ethylene-α-olefin copolymer film layer 1 polymerized using a single-site catalyst as the innermost layer,
It has an Al layer 2 as a barrier layer and a PET layer 4 as an outermost layer.

Further, in the retort packaging material shown in FIG. 3, the ethylene or ethylene-α-olefin copolymer film layer 1 polymerized using a single-site catalyst is used as the innermost layer, the intermediate layer is the ONy layer 3, and the outermost layer is the outermost layer. PET layer 4
Is to have.

Here, first, ethylene or ethylene-polymerized using the single-site catalyst used in the innermost layer 1 is used.
The α-olefin copolymer film will be described. A single-site catalyst (including metallocene catalyst, so-called Kaminsky catalyst) has uniform active sites (single-site)
It has the characteristic of being This single-site catalyst is
It is a catalyst composed of a metallocene-based transition metal compound and an organic aluminum compound, and may be supported on an inorganic substance.

Examples of the metallocene-based transition metal compound include transition metals selected from the IVB group [titanium (Ti), zirconium (Zr), hafnium (H
f)] is a cyclopentadienyl group, a substituted cyclopentadienyl group, an indenyl group, a substituted indenyl group, a tetrahydroindenyl group, a substituted tetrahydroindenyl group,
A fluorenyl group or a substituted fluorenyl group has 1 to 2 bonds, or two of these groups are crosslinked by a covalent bond to each other, and also has a hydrogen atom, an oxygen atom, a halogen atom, an alkyl group. , An alkoxy group, an aryl group, an acetylacetonate group, a carbonyl group, a nitrogen molecule, an oxygen molecule, a Lewis base, a substituent containing a diatom atom, and an unsaturated hydrocarbon.

As the organoaluminum compound,
Examples include alkylaluminum, chain-like or cyclic aluminoxane, and the like.

Here, as the alkylaluminum,
Examples thereof include triethyl aluminum, triisobutyl aluminum, dimethyl aluminum chloride, diethyl aluminum chloride, methyl aluminum dichloride, ethyl aluminum dichloride, dimethylaluminium fluoride, diisobutyl aluminum hydride, diethyl aluminum hydride, ethyl aluminum sesquichloride.

The chain or cyclic aluminoxane is produced by contacting alkylaluminum and water. For example, it can be obtained by adding alkylaluminum at the time of polymerization and then adding water, or by reacting water of crystallization of a complex salt or adsorbed water of an organic / inorganic compound with alkylaluminum.

Examples of the inorganic material supporting the single-site catalyst include silica gel, zeolite, diatomaceous earth and the like.

Polymerization methods include bulk polymerization, solution polymerization,
Examples thereof include suspension polymerization and gas phase polymerization, and these polymerizations may be performed by a batch method or a continuous method.

The polymerization conditions are usually polymerization temperature; -1
00-250 degreeC, superposition | polymerization period; 5 minutes-10 hours, reaction pressure; Normal pressure-300 Kg / cm < ² >.

Further, the α-olefin which is a comonomer copolymerized with ethylene includes propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and decene. Etc. These α-olefins may be used alone,
You may use it in combination of 2 or more. Further, the mixing ratio of α-olefin is preferably 1 to 50 mol%.

The physical properties of the ethylene-α-olefin copolymer polymerized using the above single-site catalyst are, for example, molecular weight: 5 × 10 ^{3 to} 5 × 10 ⁶ , density: 0.89 to 0.
95 (g / cm ³ ), melt index [MI];
It is 0.1 to 50.

Further, the resin obtained has a comonomer content which is smaller than that of linear low-density polyethylene (LLDPE) in that the copolymerization ratio of ethylene and α-olefin is uniform in every molecule and the content of comonomer is high. It has less high molecular weight.

The method for forming such a film is not particularly limited, and examples thereof include an extrusion method, a T-die method, an inflation method and the like. These films may be appropriately stretched before use. Further, this film is laminated with another film by dry lamination or sand lamination.

The thickness of the ethylene or ethylene-α-olefin copolymer film layer 1 polymerized using a single-site catalyst is difficult to determine uniformly because the film thickness varies depending on the application, but it is usually Is 1
The thickness is 1000 μm, and preferably 10 to 100 μm. If the thickness is 10 μm or less, sufficient heat sealability and seal strength may not be obtained. on the other hand,
This is because, even if this thickness is made thicker than 100 μm, the effect corresponding to it does not change, and it is rather disadvantageous in terms of manufacturing cost.

The ethylene of the present invention or ethylene-
Anti-fogging agent, antioxidant, ultraviolet absorber, antistatic agent, antiblocking agent, flame retardant, inorganic and organic filler, dye, pigment, etc. may be appropriately added to the α-olefin copolymer film. Good.

In the retort packaging material shown in FIG. 1 or 2, the Al layer 2 has a barrier function or function of mainly preventing the inflow of gas or water vapor from the outside. Specifically, as the barrier resin layer, in addition to Al, saponified ethylene-vinyl acetate copolymer (hereinafter,
"EVOH"), polyvinylidene chloride (hereinafter,
"PVDC"), a vapor deposited film of an inorganic oxide can be used. Here, the deposition film of an inorganic oxide means a silicon oxide (hereinafter referred to as “SiOx”), tin oxide, zinc oxide, indium oxide, with respect to a thermoplastic resin film such as polyolefin, nylon, polyester, or polyvinyl alcohol. A thin film layer made of an inorganic material such as titanium oxide or aluminum oxide is formed by vacuum vapor deposition, sputtering, plasma CVD, chemical vapor deposition, or the like.

Among the above-mentioned barrier resin layers, a vapor deposited film of an inorganic oxide is desirable from the viewpoints of environmental friendliness after disposal and transparency of the packaging material. Furthermore, among these, when silicon oxide is used as the inorganic oxide, since such a film is inferior in light-shielding property, white printing is performed on the base film, or polyethylene naphthalate is laminated, Alternatively, it is desirable to stack a base material containing a white pigment. Furthermore, as a vapor deposition method, a more transparent film can be obtained by plasma CVD than by vacuum vapor deposition.

In the retort packaging material shown in FIG. 1 or 3, the intermediate layer ONy3 has a function or action of improving strength. Specifically, in addition to ONy, polycarbonate (hereinafter referred to as “PC”), unstretched nylon (hereinafter referred to as “CNy”) and the like can be mentioned. Its thickness is usually about 10 to 40 μm. In addition, this ON
The method of processing ONy for forming the y layer 3 is not particularly limited,
For example, a tubular method, a tenter method, a sequential biaxial stretching method, a simultaneous biaxial stretching method, or the like may be used.

In the retort packaging materials shown in FIGS. 1 to 3, the outermost layers are all formed of the PET layer 4. Since the film layer 4 constituting the outermost layer is a retort packaging material, it is heated and pressed at about 120 ° C. at a high temperature, so that the packaging material is exposed to heating and hot water, and is resistant to water. Moreover, heat resistance is required. As a specific film forming the outermost layer, in addition to PET, vinylidene chloride-coated polyethylene terephthalate (K-PET), vinylidene chloride-coated biaxially oriented polyvinyl alcohol (K-OV), vinylidene chloride-coated cellophane, cellophane, oriented polypropylene. (OPP), vinylidene chloride coated polypropylene (K-OPP), polycarbonate (PC) and the like. The film thickness is usually 10 to 30 μm.
Is.

Further, the back surface of the outermost layer film 4 may be printed or the like, if necessary. The printing method may be conventionally known gravure printing, flexographic printing, or the like. In addition, in order to impart printability, the film surface may be previously subjected to corona treatment.

As described above, these layers are laminated by dry lamination, sand lamination or the like. As an adhesive that can be suitably used for this lamination, for example, a urethane adhesive can be mentioned.

As a specific layer structure, in the case of a three-layer structure, for example, from the outer layer side to the inner layer, PET / A
Ethylene or ethylene-α-olefin copolymer film polymerized by using 1 / single-site catalyst (hereinafter,
"SSC"), PET / EVOH / SSC, PE
T / SiOx-PET / SSC, PET / ONy / SS
A laminated film such as C can be used.

In the case of a four-layer structure, for example, PET / ONy / Al / SS from the outer layer side toward the inner layer.
C, PET / ONy / EVOH / SSC, PET / ON
Examples include laminated films such as y / SiOx-PET / SSC.

In addition to the above examples, other layers may be provided on the film layer in order to have various other functions.

For example, when such a laminated material has an ultraviolet blocking function, a film having an ultraviolet blocking function, for example, a polyethylene terephthalate film, a polyethylene naphthalate film, a resin containing a titanium oxide powder or a zinc oxide powder. You may utilize what was formed with the thermoplastic resin film etc. which formed the coat layer.

The retort packaging material configured as described above can be made into bags by a conventionally known bag-making method. Specifically, for example, three-way seal, standing, gusset,
It has various shapes such as vertical pillow and horizontal pillow.

[0045]

〔Example〕

Example 1 Preparation of sample In order from the outermost layer to the innermost layer, a PET layer [thickness 12 μm] /
ONy layer [thickness 15 μm] / Al layer [thickness 7 μm] / ethylene layer polymerized using a single-site catalyst [thickness 7]
0 μm] (density: 0.945) was laminated with a urethane adhesive to form a packaging material for a retort, which was three-sided into a bag of 150 mm × 180 mm to form a pouch. Example 2 Preparation of Samples PET layer [thickness 12 μm] /
ONy layer [thickness 15 μm] / Al layer [thickness 7 μm] / ethylene layer polymerized using a single-site catalyst [thickness 8]
0 μm] (density: 0.926) was laminated with a urethane-based adhesive to prepare a retort packaging material, which was three-sided bag-shaped to 200 mm × 300 mm to form a pouch.

Preparation of Comparative Example 1 Sample A pouch was prepared in the same manner as in Example 1 except that the innermost layer of the sample of Example 1 was a linear low density polyethylene layer. Preparation of Sample of Comparative Example 2 A pouch was prepared in the same manner as in Example 1 except that the innermost layer of the sample of Example 1 was a high-density polyethylene layer. Comparative Example 3 Preparation of Sample A pouch was prepared in the same manner as in Example 1 except that the innermost layer of the sample of Example 1 was a block copolymer layer of polypropylene and ethylene. Preparation of Sample of Comparative Example 4 A pouch was prepared in the same manner as in Example 1 except that the innermost layer of the sample of Example 2 was a linear low density polyethylene layer. Preparation of Sample of Comparative Example 5 A pouch was prepared in the same manner as in Example 1 except that the innermost layer of the sample of Example 2 was a high-density polyethylene layer. Comparative Example 6 Preparation of Sample A pouch was prepared in the same manner as in Example 1 except that the innermost layer of the sample of Example 1 was a block copolymer layer of polypropylene and ethylene.

[Experiment 1] With respect to the example sample 1 and the comparative examples 1, 2 and 3 prepared as described above, water and pasta meat sauce (oil-based food) were added to this pouch.
And sterilization by heating under pressure (retort) at a temperature of 120 ° C. for 30 minutes to evaluate the taste change of water as the content,
Further, the surface of the meat sauce pouch was evaluated. The results are shown in Table 1 below.

(Table 1) Change in taste of water in pouch filled with water and pouch surface after sterilization of pouch filled with meat sauce

As is clear from Table 1, in the sample of Example 1 of the present invention, there was no change in the taste of water in the pouch, and even in the case of an oily food whose content was meat sauce, the occurrence of yuzu on the surface, that is, unevenness on the surface. It can be seen that did not occur. On the other hand, in Comparative Examples 1, 2 and 3, the packaging material odor is transferred to the contents and the taste of the contents is impaired, or the surface is fine after filling and sterilizing the oily food (meat sauce). Unevenness (citrus skin) appeared or either phenomenon appeared.

[Experiment 2] For the sample 2 of Example and the samples of Comparative Examples 4, 5, and 6, water (800
ml) and cooked rice (800 g),
The change in taste of water, which is the content, was evaluated, and further, the surface of the pouch filled with the cooked cooked rice was evaluated. The results are shown in Table 2.

(Table 2) Change in taste of water in pouch filled with water and surface of pouch after sterilization of pouch filled with cooked rice

As is clear from Table 2, in the sample of this Example 2, there is no change in the taste of water in the pouch, and even if the content is an oily substance which is the basis of cooked rice, the occurrence of yuzu on the surface It can be seen that no unevenness was generated on the surface. On the other hand, in Comparative Examples 4, 5 and 6 samples, the packaging material odor is transferred to the contents and the taste of the contents is impaired, or after filling and sterilization of the oily food (boiled rice base),
Fine irregularities (citrus skin) appeared on the surface, or either phenomenon appeared.

[0053]

From the above results, the effect of the present invention is clear. That is, by using ethylene or an ethylene-α-olefin copolymer polymerized by a single-site catalyst as the innermost layer, since such a film has little odor of the packaging material itself, the odor of the packaging material itself may be transferred to the contents. In addition, the taste of the contents is not impaired.
Further, since such a film has excellent oil resistance, even when the content contains a large amount of oil, the surface of the packaging material does not have irregularities, and so-called citrus skin does not occur. Further, since such a film has a low crystallization rate, the packaging material itself has excellent impact resistance, and a packaging material for a retort having a high sealing strength of the packaging material itself can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a layer structure of a packaging material for a retort according to the present invention.

FIG. 2 is an explanatory diagram showing another example of the layer structure of the packaging material for a retort according to the present invention.

FIG. 3 is an explanatory diagram showing still another example of the layer structure of the packaging material for a retort according to the present invention.

[Explanation of symbols]

1 Ethylene or ethylene-α-olefin copolymer film layer polymerized using a single-site catalyst 2 Aluminum layer (Al layer) 3 Stretched nylon layer (ONy layer) 4 Polyethylene terephthalate layer (PET layer)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3E067 AB01 AB26 AB81 BA12A                       BA17A BB14A BB25A CA04                       CA17 EA06 EE48 FA01 FB13                       FC01 GC02 GD01 GD07 GD10                 3E086 AB01 AC07 AD01 BA04 BA13                       BA15 BB01 BB41 BB51 BB85                       CA01 CA11 CA28 DA08                 4F100 AA17C AK04D AK42A AK46B                       AK51G AK62D BA04 BA07                       BA10A BA10D EC18 EC182                       EH66C EJ37B GB15 GB16                       GB23 GB66 JA13D JC00                       JD02 JJ03 JK10 JL11 JM02C

Claims (2)

[Claims] 1. At least polyethylene terephthalate
Ethylene film or ethylene-α-olefin copolymer having a density of 0.926 to 0.945 g / cm ³ which is polymerized by using a single film catalyst layer, a stretched nylon film layer, an inorganic oxide vapor deposition film layer, and a single-site catalyst. A packaging material for a retort, comprising a film layer, and further, each layer is sequentially laminated by dry lamination through an adhesive layer. 2. At least polyethylene terephthalate
Film layer, a vapor deposition film layer of an inorganic oxide, and
Polymerized using a single-site catalyst with a density of 0.926
To 0.945 g / cm ³ of an ethylene or ethylene-α-olefin copolymer film layer, and the layers are sequentially laminated by dry lamination with an adhesive layer interposed therebetween. Material.