JPH0622970B2 - Flavor-barrier multi-layer wrapping material - Google Patents

Description

The present invention relates to a packaging material for beverages such as juice and coffee and retort foods such as curry and soup. In particular, the present invention relates to a flavor barrier multi-layer laminate packaging material for food packaging, in which the preservation property of aroma, which is one of the important commercial value of food, is improved and the deterioration of the food as the content is controlled.

[Conventional technology]

The aroma of foods consists of organic compounds of various carbon numbers. For example, terpene hydrocarbons (d
-Limonene, myrcene etc.), terpene alcohols (α-terpineol, linalool, geraniol etc.), alcohols (octanol, isoamyl alcohol etc.), aldehydes (octanal, citral, trans-2-hexanal etc.) and esters (ethyl) Capreto, amyl benzoate, ethyl cinamate, etc.) and the like. The general constitution of a gas barrier (or flavor barrier) multilayer laminate film for food packaging in which these aromas should be preserved is:
A heat-sealable polyolefin resin layer on the inner surface side in contact with food, an ethylene-vinyl alcohol copolymer resin as a gas barrier layer in the middle, a layer of a gas barrier resin such as polyvinylidene chloride resin and a metal foil such as aluminum, and the like. On the outer side, a synthetic resin layer such as a polyolefin resin or a polyester resin is formed as a support layer or a protective layer. Each of these layers is generally laminated by an adhesive layer.

In particular, the polyolefin resin as the sealant layer on the inner surface side and the gas barrier resin or metal foil used for the gas barrier layer have almost no affinity with each other and cannot be laminated without using an adhesive.

As these adhesives, polyester-based or acrylic-based adhesives are used from the viewpoint of hygiene and water resistance, but polyester-based adhesives are mainly used from the viewpoint of price and the like.

By the way, one of the important commercial values of packaged food is its aroma. This is one element of the flavor of food, and it is no exaggeration to say that the deterioration of aroma itself is the deterioration of food as a product. This fragrance is created by a large number of trace organic components contained in food, and the fragrance peculiar to the food is formed by the balance of vapor concentrations of these trace organic components.

However, since the polyolefin resin as a sealant layer that is in direct contact with foods adsorbs aroma components of foods to a considerable extent, it must be kept thin enough for heat sealing. Furthermore, the adhesive layer that adheres the sealant layer to the gas barrier layer generally has a higher sorption power than the sealant layer, and sorbs the aroma components that are the aroma of foods, reducing the absolute amount of aroma components. At the same time, the balance is lost and the aroma, which is an important commercial value of food, is deteriorated. An object of the present invention is to provide a packaging material that eliminates the sorption of aroma on the adhesive layer, enhances the retention of aroma of food, and thus prevents the commercial value of food from deteriorating.

Further, when a gas barrier resin is used for the gas barrier layer, sorption of the fragrance component still occurs at the same time as sorption to the adhesive layer. If a metal foil such as aluminum is used for the gas barrier layer, sorption of aroma components on the gas barrier layer is almost eliminated. However, when a metal foil is used, the packaging material itself becomes opaque and also sorbs onto the adhesive layer.

For this reason, it has been studied to use an inorganic oxide such as silicon or tin on a synthetic resin by vapor deposition, ion plating or sputtering, and use the inorganic oxide thin layer formed thereby as a gas barrier layer.

However, in the case where an oxide of an inorganic substance is vapor-deposited on a single film as shown in Japanese Examined Patent Publication No. 53-12953, the vapor-deposited surface cannot be heat-sealed. This may cause the barrier layer to peel off.

Also, a method has been devised in which a modified polyolefin having an adhesive property is laminated on an inorganic oxide layer to form a heat-sealing layer as disclosed in JP-A-59-62143, 60-23037, 58-128852. Since the price is high and the resins that can be used are limited, inconvenience occurs when trying to obtain arbitrary heat-sealing characteristics.

[Problems to be solved by the invention]

In a gas barrier multilayer laminate packaging material for food, a polyolefin resin layer as the sealant layer,
Sorption of the aroma components of the food product, which is the content, occurs in both of the adhesive layer that enables the lamination of the sealant layer and the gas barrier layer. This significantly impairs the flavor of the food.

Also, considering the retort treatment of foods, it is necessary to consider the material of the gas barrier layer. In ethylene-vinyl alcohol copolymer resin, the gas barrier property is extremely deteriorated due to moisture absorption during the retort treatment, and in a laminate with a polyolefin resin, it takes a considerable number of days to dry after the retort treatment, so that the gas barrier property is several days. However, it does not recover. The polyvinylidene chloride resin has a drawback that it is relatively inferior in gas barrier properties under normal conditions and is slightly difficult to mold. However, a thin metal such as aluminum does not cause a problem like a gas-barrier resin, but has no transparency and does not allow microwaves to pass therethrough, and therefore cannot be used for re-cooking in a microwave oven together with a container.

Therefore, it is most preferable to use, as the gas barrier layer, an inorganic oxide thin layer formed by vapor deposition or sputtering of an inorganic oxide having excellent gas barrier properties and water resistance and transparency. However, when this is formed on a support such as a polyester film and used as the gas via layer as an integral body, the polyolefin resin as the inner sealant layer has to be laminated with an adhesive, and the food of the adhesive layer is used. The sorption problem of aroma components remains unsolved.

[Means and Actions for Solving Problems]

Therefore, the inorganic oxide is directly vapor-deposited or ion-plated on the surface of the polyolefin resin layer as the sealant layer, which is opposite to the sealing surface (that is, the surface which directly contacts the food) (that is, the adhesive layer in the conventional structure). Alternatively, the thin inorganic oxide layer is formed by sputtering. As a result, the sealant layer and the gas barrier layer can be integrally laminated without using the adhesive layer. Therefore, there is no sorption of the aroma components of food by the adhesive layer. Further, since the inorganic oxide layer is used as the gas barrier layer, the gas barrier property is maintained excellent even by the retort treatment, and the transparency is also excellent.

To describe the present invention in more detail, as the sealant layer,
Polyolefin resin-that is, polyethylene, polypropylene and their copolymers and modified resins are used. It is necessary to make the sealant layer as thin as possible and to consider the crystallinity of the resin used. Specifically, when the carbon number of the organic compound that is the main component of the aroma component is 3 to 5, the crystallinity of the sealant resin is preferably 40% or more. When the carbon number of the organic compound is 6, 50% or more, the carbon number is 7
In the case of the above, the crystallinity is preferably 55% or more. The sealing property must be a resin capable of exhibiting a sealing strength of 500 g / 15 mm width or more as a multilayer laminate packaging material when heat-sealing for 1 second at a pressure of 1 kg / cm ² at a temperature of 150 ° C.

Next, as an inorganic oxide, an oxide of silica, tin, titanium or indium is used in consideration of transparency. Silica oxide is particularly preferable because it is superior in gas barrier property. Thin film formation by vapor deposition or sputtering of these inorganic oxides is by a known method.

Further, on the outer side thereof, a synthetic resin layer is provided as a support of the multilayer laminate packaging material and a protective layer of the inorganic oxide thin film via an adhesive layer. As the synthetic resin, polyethylene, polypropylene and their copolymers and modified products, polyvinyl chloride, polyester, nylon and their copolymers, modified products and mixtures are used.

〔Example〕

Example 1 High-density polyethylene Shorex S 6008FD (Showa Denko
(Manufactured by Co., Ltd.) was formed into a single layer film having a thickness of 20 μm by an inflation method. Vacuum 2 × a SiO ₂ using a SiO ₂ 99.99% of tungsten boat as a heating element on one side
Vacuum deposition was performed under the condition of 10 ⁻⁴ Torr, and a vapor deposition film of 500 Å was laminated. Further, a 50 μm polypropylene film allomer ET (manufactured by Showa Denko KK) was dry-laminated to form a protective layer. For the dry laminate, polyester adhesive AD950A / B manufactured by Toyo Morton Co., Ltd. was used, and the coating amount was adjusted to be 4 g / m ² when dried. After laminating, aging was performed for 4 days at a constant temperature of 40 ° C.

This multi-layer film was heat-sealed with the high-density polyethylene side as the inner surface to prepare a 18 cm x 10 cm pouch. An aqueous solution of a surfactant in which various flavor components are dissolved in this pouch (ryoto sugar ester S 1170
300 ml of a 0.5% aqueous solution, manufactured by Mitsubishi Kasei Foods Co., Ltd. was enclosed and stored at a constant temperature of 23 ° C. for 52 days. After that, the pouch was opened, the flavor component sorbed by the high-density polyethylene on the inner surface of the pouch was extracted with ether, and the flavor component remaining in the aqueous solution was also extracted with ether. The sorption amount and residual amount converted to the original aqueous solution concentration were quantified for each flavor component using gas chromatography for each, and the distribution ratio of flavor sorption was calculated according to the following formula from the obtained results.

That is, the larger the distribution ratio is, the stronger the flavor sorption is, and when it is 1, half of the flavors contained in the aqueous solution before encapsulation are sorbed on the inner surface film, and the larger the ratio becomes, the more the flavor remains in the aqueous solution. The flavor density decreases.

The results are shown in Table 1. Comparing the concentration at the time of encapsulation and the total amount of recovery, which is the sum of the amount of sorption and the amount of remaining, there is almost no difference, and it can be seen that the SiO ₂ vapor deposition film is effective as a flavor barrier layer.

Comparative Example 1 SiO ₂ was vapor-deposited on one surface of a polypropylene film Allomer ET (manufactured by Showa Denko KK) having a thickness of 50 μm under the same conditions as in Example 1, and a high density polyethylene Shorex S was formed on the surface.
An inflation film (20 μm thick) of 6008 FD (Showa Denko KK) was dry laminated. The dry lamination was performed in the same manner as in Example 1.

The same flavor sorption test as in Example 1 was performed. The results are shown in Table 1. Since the total recovery rate is almost the same as the concentration at the time of encapsulation, the SiO ₂ sputtering layer is also
It can be seen that it has an effective flavor barrier property.
However, in this case, in addition to the high-density polyethylene, the adhesive layer also contributes to flavor sorption, so that the sorption amount (distribution ratio) is large.

〔The invention's effect〕

As described above, by stacking a gas barrier layer consisting of a sealant layer and a thin inorganic oxide layer without an adhesive, it is possible to withstand a retort that suppresses the sorption of aroma components of foods. A barrier multi-layer laminate packaging material can be provided.

Claims (2)

[Claims] 1. A heat-sealable sealant resin layer is laminated with an inorganic oxide on a surface opposite to a sealing surface, and at least one synthetic resin layer is provided on the inorganic oxide through an adhesive layer. A multi-layer laminate packaging material with a flavor barrier property for food products. 2. The packaging material according to claim 1, wherein the sealant resin is polyolefin.