JP7818886B2 - Packaging film for adhesion of condensation water - Google Patents

Description

The present invention relates to a packaging film for adhering condensed water, which is used to adhere condensed water to the surface of a packaged item when the packaged item is packaged.

Today, packaging film (hereinafter referred to as packaging film) is widely used in homes and restaurants to seal food. The primary purpose is to prevent dirt, dust, and other debris, as well as bacteria, from adhering to the food, and to prevent the food from drying out, losing its flavor, and emitting an odor during storage or food processing such as heating or cooling.

In view of the above-mentioned intended use of packaging films, the packaging films are required to have properties that contribute to the intended use of the packaging films, such as oxygen gas barrier properties, water vapor barrier properties, and heat resistance.
In particular, attention has been focused on water vapor barrier properties, and a packaging film containing a polyvinylidene chloride resin has been proposed (Patent Document 1) with the aim of obtaining a packaging film with high water vapor barrier properties.

Patent Publication No. 2019-151018

Conventionally, as shown in the above-mentioned Patent Document 1, development has focused on improving the water vapor barrier property.
Packaging films are also used to store food in refrigerators and freezers, but if the use of packaging films can make handling food and preparing food before cooking easier, the need for packaging films will expand even further.

After extensive research into various packaging films, the inventors discovered that rather than increasing the water vapor barrier properties, using a packaging film with low water vapor barrier properties and one that allows a certain degree of water vapor permeation makes it easier to handle food and prepare it before cooking when used to preserve food.

The present invention aims to provide a packaging film that satisfies the purpose of a packaging film, which is to prevent the adhesion of dirt, dust, and other debris and bacteria, and that, when used to store food, makes it easier to handle food and prepare it before cooking.

As a result of extensive research into solving the above problems, the inventors discovered that a packaging film with a specific moisture permeability can be used as a packaging film that makes food handling and pre-cooking preparation easier, leading to the completion of the present invention.

The present invention relates to packaging films described in the following [1] to [4].
[1] A packaging film for adhering condensed water, which is used to adhere condensed water to the surface of a packaged item when the packaged item is packaged, and which has a moisture permeability of 400 g/ ^m2 ·24 hr or more under conditions of 40°C and 90% RH.
[2] A packaging film for adhesion of condensation water according to [1], wherein the moisture permeability of the packaging film under conditions of 40°C and 90% RH is 600 to 1000 g/m ² ·24 hr.
[3] The packaging film for adhesion of condensation water described in [1] or [2], wherein the packaged item is a frozen food.
[4] A packaging film for adhesion of condensation water described in [1] or [2], wherein the packaged item is a food product using powder.

The present invention provides a packaging film that satisfies the purpose of a packaging film, which is to prevent the adhesion of dirt, dust, and other debris and bacteria, and that, when used to store food, makes it easier to handle food and prepare it before cooking.

FIG. 1 is a diagram showing the state of condensed water adhering to oil blotting paper made from Japanese paper in an example.

Preferred embodiments of the packaging film of the present invention will be described in detail below.
It should be noted that the embodiments described below do not limit the invention according to the claims, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

(packaging film)
The packaging film for adhering condensed water of the present invention is used to adhere condensed water to the surface of an article when the article is packaged.
The packaging film for adhesion of condensed water of the present invention has a moisture permeability of 400 g/m ² ·24 hr or more under conditions of 40°C and 90% RH.

The packaging film of the present invention has excellent moisture permeability, allowing water vapor to easily pass through. Therefore, by using the packaging film of the present invention to package an item and then storing it under specified conditions, the temperature difference between the packaged item and the outside atmosphere, as well as the difference in saturated water vapor pressure, can be utilized to protect the packaged item from foreign matter such as dirt and dust, while allowing condensation water, which is water produced by condensation, to adhere to the surface of the packaged item.

<Resin composition>
The packaging film of the present invention contains a resin composition as its raw material. In this specification, the term "resin composition" refers to a composition containing a resin as a main component and optionally containing other components. Preferred components of the resin composition will be described below.

<<Resin>>
Resins that can be used in the packaging film of the present invention include, but are not limited to, polyvinyl chloride resins, polyvinylidene chloride resins, polyethylene resins, polybutadiene resins, polypropylene resins, and polyester resins. These can be used alone or in combination of two or more. Among these, polyvinyl chloride resins are preferred from the viewpoint of obtaining excellent moisture permeability.

Examples of polyvinyl chloride resins include polyvinyl chloride and copolymers of vinyl chloride monomers and copolymerizable monomers. Copolymers may be binary, ternary, or higher-component systems, and may be random or block copolymers. Examples of copolymers include vinyl chloride-vinyl acetate copolymers, vinyl chloride-(meth)acrylic acid copolymers, vinyl chloride-methyl (meth)acrylate copolymers, vinyl chloride-ethyl (meth)acrylate copolymers, vinyl chloride-maleic ester copolymers, vinyl chloride-ethylene copolymers, vinyl chloride-propylene copolymers, vinyl chloride-styrene copolymers, vinyl chloride-isobutylene copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-styrene-maleic anhydride terpolymers, vinyl chloride-styrene-acrylonitrile terpolymers, vinyl chloride-butadiene copolymers, vinyl chloride-isoprene copolymers, vinyl chloride-chlorinated propylene copolymers, vinyl chloride-vinylidene chloride-vinyl acetate terpolymers, vinyl chloride-acrylonitrile copolymers, and vinyl chloride-various vinyl ether copolymers. These can be used alone or in combination of two or more.

When a polyvinyl chloride resin is used as the resin, the degree of polymerization of the polyvinyl chloride resin is not particularly limited, but is preferably 800 or more, more preferably 950 or more, from the viewpoint of the mechanical properties of the film. If the degree of polymerization of the polyvinyl chloride resin is 800 or more, there is no risk of the film becoming brittle. On the other hand, the degree of polymerization of the polyvinyl chloride resin is preferably 2500 or less, more preferably 1500 or less. If the degree of polymerization of the polyvinyl chloride resin is 2500 or less, there is no risk of the melt viscosity of the polyvinyl chloride resin becoming too high, and there is no risk of poor hot melt moldability.
The degree of polymerization of the polyvinyl chloride resin is an average degree of polymerization measured in accordance with JIS K 6720.

When a polyvinyl chloride resin is used as the resin, the content of the polyvinyl chloride resin is not particularly limited, but is preferably 90% by mass or more, and more preferably 95% by mass or more, relative to the total amount of the packaging film. Furthermore, the content of the polyvinyl chloride resin is not particularly limited, but is preferably 99.5% by mass or less, and more preferably 99% by mass or less, relative to the total amount of the packaging film. By setting the content of the polyolefin resin to be equal to or greater than the above lower limit and equal to or less than the above upper limit, a packaging film with particularly desirable moisture permeability tends to be obtained.

<<Other additives>>
As other additives, various additives that are commonly used in the production of packaging films can be used arbitrarily.
Examples of additives include plasticizers, stabilizers such as calcium/zinc-based metal soaps and hydrotalcites, chlorine scavengers (hydrotalcite compounds, zeolite compounds, metal soaps, etc.), antioxidants (phosphorus-based, phenol-based, sulfur-based, etc.), light stabilizers (hindered amine-based, etc.), epoxy compounds (epoxidized soybean oil, etc.), β-diketone compounds, perchlorates, polyhydric alcohols, pigments, lubricants, crosslinking agents, antistatic agents, antifogging agents, plate-out prevention agents, surface treatment agents, flame retardants, fillers, fluorescent agents, antifungal agents, disinfectants, metal deactivators, release agents, and processing aids.

(Physical properties of packaging film for adhesion of condensation water)
<Moisture permeability>
The moisture permeability of the packaging film is preferably 400 g/ ^m² ·24 hr or more, more preferably 500 g/ ^m² ·24 hr or more, and even more preferably 600 g/ ^m² ·24 hr or more. The moisture permeability of the packaging film is preferably 1,500 g/ ^m² ·24 hr or less, more preferably 1,200 g/ ^m² ·24 hr or less, and even more preferably 1,000 g/ ^m² ·24 hr or less. If the moisture permeability is above the lower limit, air in the internal space can move easily, allowing sufficient condensation water to form inside the packaging film. If the moisture permeability is below the upper limit, the packaged item can be prevented from drying out.
The moisture permeability in the present invention is a value measured in accordance with JIS Z 0208:1976 under conditions of a temperature of 40° C. and a relative humidity (RH) of 90%.

<Thickness>
The thickness of the packaging film of the present invention is not particularly limited as long as the moisture permeability is within the above range, but is usually 5 μm to 30 μm. If the thickness is equal to or greater than the above lower limit, the barrier properties required for packaging are easily obtained, and if the thickness is equal to or less than the above upper limit, sufficient flexibility is easily obtained.

<Thermal conductivity>
In general, the thermal conductivity of the packaging film is preferably low in order to allow condensed water to adhere to the surface of the packaged item.
The thermal conductivity of the packaging film is preferably 0.01 to 3.0 W/m K. If the thermal conductivity is equal to or greater than the lower limit of the above range, the heat insulating properties of the packaging film can be kept low, and sufficient condensation water can be easily formed inside the packaging film. If the thermal conductivity is equal to or less than the upper limit of the above range, heat dissipation from the packaging film can be suppressed, and the formation of condensation water on the outer surface of the packaging film can be easily suppressed.

(Method for manufacturing packaging film)
The packaging film of the present invention is not particularly limited, and various conventionally known methods can be used, such as a cast molding method in which a molten resin is extruded into a sheet using a single-layer or multi-layer T-die or I-die connected to a screw-type extruder, an inflation molding method in which a molten resin is extruded into a tubular shape using a circular die and expanded by the air pressure inside, a calendar molding method in which a kneaded material is rolled with a plurality of heated rolls to form a sheet, and a solution method in which a material is dissolved in a solvent such as water, the solution is poured onto a drum with a smooth surface (casting drum) or a smooth stainless steel belt to adhere to the material, and the resulting material is dried by a heating process.
The packaging film of the present invention can be produced, for example, by extruding the resin composition using an inflation extruder to obtain a raw film, which is then rewound using a rewinder to produce the packaging film. The stretching ratio of the packaging film can be appropriately adjusted to obtain a specific moisture permeability. Furthermore, in order to impart or promote antifogging properties, antistatic properties, adhesive properties, etc., the film may be subjected to treatments such as corona treatment and aging, or may be subjected to surface treatments and finishes such as coating.

(Use of packaging film)
The packaging film of the present invention described above has excellent moisture permeability, so by using the packaging film of the present invention to package an item and then storing it under specified conditions, condensed water can be attached to the packaged item.
A preferred method of using the packaging film for adhesion of condensed water of the present invention will now be described in detail.

<Glazing of low-temperature packaged items such as frozen foods>
It has been known that frozen foods tend to deteriorate during long-term frozen storage. To prevent this deterioration, frozen foods are usually sprayed with water or immersed in water to form a thin ice coating (glaze) on their surfaces.
Conventional glazing processes require spraying with water or immersion in water, making it difficult to form an ice coating on foods that easily absorb moisture or contain powder.

The packaging film of the present invention is used to package a low-temperature packaged item such as a frozen food, which is at a temperature lower than the outside atmosphere (e.g., room temperature), and the packaged item is left standing in the outside atmosphere for a predetermined period of time to allow condensation water to adhere to the surface of the low-temperature packaged item.The adhered condensation water is then frozen at a low temperature, thereby forming a glaze on the low-temperature packaged item such as a frozen food.
That is, by using the packaging film of the present invention, glaze treatment of frozen foods and the like can be easily carried out.
Furthermore, since the packaging film of the present invention does not require conventional treatments such as spraying with water, it can be particularly suitably used as a packaging film for glazing foods that easily absorb moisture or foods that contain flour.

<Improvement of handling of packaged food products, etc.>
BACKGROUND ART Conventionally, when removing a package such as a packaging film from a packaged item such as food, it has sometimes been difficult to remove the packaged item if the packaged item has a strong adhesive bond to the film.
Furthermore, when removing packaging such as packaging film from packaged items such as food, there are cases where the packaged items are directly touched with hands to remove them. In particular, in the case of foods that are not heat-treated after being removed from the packaging film, touching the food with hands can transfer bacteria or viruses to the food, which can cause food poisoning, so there is room for improvement in terms of hygiene.

The packaged item of the present invention can be stored, for example, in a low-temperature atmosphere that is lower than the external atmosphere, and then placed in an environment that is higher in temperature and more humid than the low-temperature atmosphere, thereby forming a water film on the surface of the packaged item.
By placing a film of water between the surface of the packaged item, such as food, and the packaging film, the slipperiness of the packaged item is improved, making it easier to remove the packaged item from the packaging film and making it easier to remove the packaged item.
Furthermore, since a water film can be formed on the packaged item such as food without direct hand contact, the transfer of bacteria or viruses from the hands to the packaged item can be inhibited, making it highly hygienic.
The packaging film of the present invention allows packaged items such as food to be easily and hygienically removed, and therefore can be suitably used as a packaging film for improving the handling of packaged items such as food.

<Improvement of pre-cooking preparation for packaged foods, etc.>
In recent years, there has been a trend to reduce calorie intake in order to prevent adult diseases and other problems. For example, powders such as breadcrumbs used in deep-fried foods absorb a large amount of oil during frying. Therefore, the resulting fried foods tend to be high in calories, and there has been a need to prevent excessive adhesion of powders such as breadcrumbs used in deep-fried foods to foods. One cooking method for deep-fried foods involves sprinkling the powder directly on the food to reduce the amount of powder used, and then frying the food in oil. However, it is difficult to coat the entire food with the powder evenly.

The packaging film of the present invention can be used to package fried or baked foods coated with breadcrumbs or other powder, store them in a low-temperature atmosphere that is lower than the ambient atmosphere, and then place them in a humid environment that is higher than the low-temperature atmosphere. This causes condensation to form on the surface of the food, causing the powder to absorb moisture, and allowing the powder to adhere tightly and uniformly to the entire food. Because the powder is tightly adhered, any excess powder can be easily removed by simply applying moderate vibration.
Furthermore, even if the powder itself has been seasoned, when the food is fried or baked, the powder, which absorbs a large amount of oil due to condensation, does not adhere excessively to the food, and therefore the resulting fried or baked food can be kept low in calories.
Therefore, the packaging film of the present invention can simplify the effort required for pre-cooking preparation of foods and other foods that use powder, and can be suitably used as a packaging film for improving pre-cooking preparation of packaged items such as foods.

(Packaged item)
The article to be packaged in the packaging film of the present invention described above is not particularly limited and can be appropriately selected depending on the application and purpose. From the viewpoint of maintaining a large temperature difference with the outside air, it is usually preferable that the article to be packaged has a low thermal conductivity.
The packaging material is preferably food, but can also be used for items other than food. Among foods, frozen foods, foods containing powder, and foods that require particular hygiene control are more preferred.
Frozen foods are foods that are stored at temperatures typically found in domestic and industrial freezers (about -5°C or below), and are not limited to any particular type of food.
The powder used in the food product is not particularly limited as long as it is in powder form, and examples thereof include wheat flour, bread crumbs, starch, rice flour, tempura flour, salt, pepper, powdered sugar, and the like.
Foods that particularly require hygiene management include, for example, foods for people with weakened immune systems, such as nursing care foods and foods for infants and toddlers.

The present invention will be specifically explained below using examples. Note that the materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples.

(Evaluation of packaging film using metal balls as packaged items)
First, the test results will be described using a metal ball as an example of the packaged item. The resin and moisture permeability of the resin composition of the film used for the evaluation are shown in Table 1. The moisture permeability values were calculated in accordance with JIS Z 0208:1976 under conditions of a temperature of 40°C and a relative humidity of 90%.

[Evaluation method]
The packaging films in the examples and comparative examples were evaluated by the following methods.
<Whether or not condensation occurs>
A metal ball (1 cm in diameter) was wrapped in a Japanese paper blotting paper (10 cm x 10 cm), and the wrapped Japanese paper blotting paper was then wrapped in the packaging film (15 cm x 15 cm) of each Example and Comparative Example and stored frozen in a -20°C freezer for one day. After frozen storage, the paper was left to stand for another minute at room temperature (26°C, 57% RH), the packaging film was peeled off, and the presence or absence of condensation was evaluated according to the following criteria. Figure 1 shows the state of condensation water adhering to the Japanese paper blotting paper. The results are shown in Table 2.
○: Good (Condensed water adheres to the washi oil blotting paper)
×: Poor (Condensed water does not adhere to the washi oil blotting paper)

<Amount of condensation>
In the above evaluation of the presence or absence of condensation water, when condensation water adhered to the Japanese paper oil blotting paper, the amount of condensation was evaluated according to the following criteria. The results are shown in Table 2.
○: Good (the area wetted by condensation water is 80% or more of the area of the washi paper)
△: Fairly good (the area wetted by condensed water is 30% or more of the area of the washi paper blotting paper)
×: Poor (the area wetted by condensed water is 10% or more of the area of the washi oil blotting paper)

As is clear from Table 2, with the packaging films of Comparative Examples 1 to 7, which had a moisture permeability of 126 g/ ^m² ·24 hr or less, no condensation was observed on the Japanese paper blotting paper, whereas with the packaging films of Examples 1 to 4, which had a moisture permeability of 400 g/ ^m² ·24 hr or more, condensation was observed on the Japanese paper blotting paper, and the amount of condensation was good or somewhat good.
Therefore, the packaging films of Examples 1 to 4 can form a water film on the surface of the packaged item by, for example, storing them in a low-temperature atmosphere that is lower than the external atmosphere, and then placing them in an environment that is higher in temperature and more humid than the low-temperature atmosphere.
The packaging films of Examples 1 to 4 allow packaged items such as food to be easily and hygienically removed, and can therefore be suitably used as packaging films for improving the handling of packaged items such as food.

(Evaluation of packaging films using powdered food as the packaged item)
The test results will be explained below using the packaging films of the Examples and Comparative Examples listed in Table 1 and food products containing powder as the packaged items.

<Amount of condensation>
Powdered sugar was spread thinly on a wrapping film as a powder, and frozen cookie dough was placed on top of that, packaged, and stored frozen in a -20°C freezer for one day. After frozen storage, the cookie was left to stand at room temperature (25°C, 55% RH) for another 10 minutes, after which the wrapping film was removed and the amount of condensation was evaluated according to the following criteria. The results are shown in Table 3.
○: Good (the entire surface of the cookie dough was covered in condensation)
△: Fairly good (there was a little condensation on the surface of the cookie dough)
×: Poor (there was almost no condensation on the surface of the cookie dough)
<Amount of powder adhesion>
When the condensation water was evaluated as being good or fairly good in the above evaluation of the presence or absence of condensation water, the amount of powder adhesion was evaluated according to the following criteria. The results are shown in Table 3.
○: Good (The powdered sugar was wet and adhered to the entire surface of the cookie dough)
△: Fairly good (the powdered sugar was wet and attached to almost the entire surface of the cookie dough)
×: Poor (The powdered sugar had become translucent due to the oil in the cookie dough and was stuck to the cookie)

As is clear from Table 3, in the packaging films of Comparative Examples 1 to 7, which had a moisture permeability of 126 g/ ^m2 ·24 hr or less, condensation occurred on the cookie dough and no powdered sugar adhered to it, whereas in the packaging films of Examples 1 to 4, which had a moisture permeability of 400 g/ ^m2 ·24 hr or more, condensation occurred on the powdered sugar and it was observed that the powder adhesion amount was good or somewhat good.
Therefore, the packaging films of Examples 1 to 4 can be used to package fried or baked foods coated with breadcrumbs or other powder, store them in a low-temperature atmosphere that is lower than the ambient atmosphere, and then place them in a humid environment that is higher than the low-temperature atmosphere, causing condensation to form on the surface of the food and absorbing moisture, allowing the powder to adhere tightly and uniformly to the entire food. Because the powder is tightly adhered, any excess powder can be easily removed by simply applying moderate vibration.
The packaging films of Examples 1 to 4 can simplify the labor required for pre-cooking preparation of foods and other foods that use powder, and can be suitably used as packaging films for improving pre-cooking preparation of packaged items such as foods.

As is clear from the above results, the packaging films of Examples 1 to 4, which have a moisture permeability of 400 g/ ^m² ·24 hr or more, have good or somewhat good condensation amounts and powder adhesion amounts, and are found to have superior performance as packaging films for adhesion of condensation water compared to the packaging films of Comparative Examples 1 to 7, which have a moisture permeability of 126 or less.
That is, it is clear that the packaging films of Examples 1 to 4 exhibit excellent performance as packaging films for preventing condensation water adhesion, because the moisture permeability is within a specific range.

As is clear from the above results, the packaging film of the present invention satisfies the purpose of a packaging film, which is to prevent the adhesion of dirt, dust, and other debris and bacteria, and also has the characteristic of making food handling and pre-cooking preparation easier when used to preserve food.

The packaging film of the invention satisfies the purpose of a packaging film, which is to prevent the adhesion of dirt, dust, and other debris and germs, and when used to preserve food, makes it easier to handle the food and prepare it before cooking.

Claims (2)

It is a packaging film for storing items (excluding mushrooms) in a low-temperature atmosphere that is lower than the external atmosphere.
A packaging film for glazing , wherein the packaged item is a frozen food,
The packaging film has a moisture permeability of 600 to 1000 g/m ² ·24 hr under conditions of 40°C and 90% RH,
The packaging film is a film made of a polyvinyl chloride resin.
Packaging film for glazing . 2. The packaging film for glazing according to claim 1, wherein the packaged item is a food product containing powder.