JPH0939171A - Packaging film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging film having excellent heat shrinkability and property to recover from deformation, with which wrinkles do not remain on a packaged article when it is used for high speed automatic packaging by a shrink method. SOLUTION: On both faces of an inner layer film obtained from an ethylene-α-olefin copolymer copolymerized by using a single site catalyst, ethylene-vinyl acetate copolymer films are laminated and molded by inflation molding at a blow ratio of 2.5-4.5.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a packaging film. Specifically, a film obtained from a specific ethylene-vinyl acetate copolymer is used as an inner layer, and ethylene-vinyl acetate copolymer is laminated on both surfaces of the film, and stretched, and is excellent in resilience to deformation, heat shrinkability, etc. Multi-layer packaging film.

[0002]

2. Description of the Related Art An ethylene resin film such as a low density polyethylene resin or an ethylene-vinyl acetate copolymer resin is used as a stretch packaging film for prepacking fruits and vegetables, fresh fish, meat, prepared foods and the like. However, since these stretch wrapping films have poor flexibility and are difficult to stretch, they often break or show non-uniform stretch when stretched forcibly. In addition, when the food to be packaged is placed on a tray for packaging, there is a problem that the tray cannot be packaged with commercial value due to deformation or destruction of the tray or wrinkles on the packaging film. .

Further, in recent years, high-speed automatic packaging machines have been popularized for the purpose of reducing the packaging cost, and high-speed automatic packaging of various kinds of irregularly shaped products has been implemented in order to achieve high-speed packaging and labor saving.
However, since the ethylene resin film does not have sufficient recovery from deformation, when performing high-speed automatic packaging of various irregularly shaped products, make sure that the packaging has a tight fit that fits the shape of the packaged product without leaving wrinkles. Not only is it difficult, but it is not always satisfactory in terms of the so-called deformation recovery property that recovers the deformation on the film surface without leaving wrinkles when the package is transported or displayed in a store. You don't get it.

Therefore, many packaging films have been proposed which can be packaged without leaving wrinkles and are excellent in recovery from deformation. For example, in JP-A-5-104624, ethylene 60 to 95 is provided on both sides of a resin layer composed of 10 to 90% by weight of butene-1 resin and 90 to 10% by weight of olefin resin and / or olefin thermoplastic elastomer. weight%
And a vinyl resin, an unsaturated unsaturated carboxylic acid, an unsaturated unsaturated monocarboxylic acid alkyl ester and a monomer selected from 5 to 40% by weight of a copolymer resin surface layer coated with a film having a blow ratio of 8 to A film formed by inflation molding at 20 times is disclosed. In addition, Japanese Examined Patent Publication No. 5-85347 and Japanese Examined Patent Publication No. 5
-85348 discloses a wrap film in which an intermediate layer made of a linear ethylene-α-olefin copolymer having a density of 0.910 g / ml or less and an outer layer made of an ethylene-vinyl acetate copolymer are laminated. It is disclosed.

However, the films disclosed in the above publications have good heat sealability, etc., but have a low heat shrinkage ratio and are not sufficiently recoverable against deformation, and when they are used as a packaging film, It cannot be used for high-speed automatic packaging by the shrinkage method because wrinkles remain on the package. In order to prevent wrinkles from remaining, the shrinkage method uses the heat shrinkability of the film to pre-wrap the packaged object in advance with a packaging film to loosely surround the object and then hot air the packaged object. , A method of heating and shrinking with a heat medium such as infrared rays or hot water to tightly adhere the packaging film to the article to be packaged. Since the above film has a low heat shrinkage rate, wrinkles that remain in the package are not eliminated even after the package is heated and shrunk, and the sealing part is removed, so that the film is satisfactory for packaging. Not a film.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to improve the slipping property, self-adhesion property, heat-sealing property, transparency, extensibility, flexibility and the like of a packaging film. While maintaining the same characteristics as the product, excellent heat shrinkability,
It is an object of the present invention to provide a packaging film which has resilience to deformation and, when used for high-speed automatic packaging by a shrinkage method, does not leave wrinkles in the package and does not impair the appearance of the package.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a film obtained from an ethylene-α-olefin copolymer polymerized using a single-site catalyst is used as an inner layer and ethylene is formed on both surfaces of the film. -Lamination of vinyl acetate copolymer film, and a laminate obtained by inflation molding it under specific conditions, found that the stretched film can solve the above problems, the present invention, It was

That is, according to the present invention, an ethylene-vinyl acetate copolymer film is laminated on both sides of an inner layer film obtained from an ethylene-α-olefin copolymer polymerized using a single-site catalyst, and blown. Ratio 2.5
It is a film for packaging characterized by being inflation-molded in a range of up to 4.5.

The packaging film of the present invention is characterized in that a specific ethylene-α-olefin copolymer film is used as the inner layer film, and the recoverability against deformation,
It is a film having improved heat shrinkability, and when it is used for high-speed automatic packaging by the shrinking method, no wrinkles remain in the package and the appearance of the package is not impaired. Therefore, the appearance of the package is beautiful, the product value is increased, and the quality of the package can be visually and tactually maintained while keeping the package hygienic. It can be tightly fixed and packaged with a previously unexpected effect.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The packaging film of the present invention will be described in detail below. The packaging film of the present invention is obtained by laminating an ethylene-vinyl acetate copolymer film on both sides of an inner layer film obtained from an ethylene-α-olefin copolymer polymerized using a single-site catalyst, and under specific conditions. Manufactured by inflation molding below.

The ethylene-α-olefin copolymer polymerized using a single-site catalyst (hereinafter referred to as S-LLDPE) used in the present invention is ethylene and another α-olefin polymerized using the catalyst. It is a copolymer with an olefin. S-LLDPE is a linear low-density polyethylene resin having a narrower molecular weight distribution and a uniform comonomer distribution than conventional linear low-density polyethylene. Other α-olefins include butene-1, hexene-1, octene-1 and the like. Preferably octene-1
It is. The α-olefin content in the copolymer is usually
It is 1 to 40% by weight, preferably 2 to 30% by weight. Among these, a copolymer in which an α-olefin is introduced as a long-chain branch in a main chain composed of ethylene units is preferable.

In consideration of moldability, transparency, toughness, flexibility, impact resistance, heat shrinkability, etc., the melt index (measured by the method specified in ASTM D-1238, hereinafter referred to as MI) is 0.5-10g / 10mi
n. , Preferably 0.5 to 5 g / 10 min. It is.
Further, the density (measured by the method specified in ASTM D-792, hereinafter referred to as density in units) is 0.863 to
It is preferably 0.935 g / cm ³ . Such S
-By forming the inner layer film from LLDPE,
A packaging film excellent in recovery from deformation, heat shrinkability, extensibility, and flexibility can be obtained.

Commercial products include, for example, EG8 manufactured by The Dow Chemical Company (Headquarters: Michigan, USA).
Engage system (trade name) such as 150, EG8100, EG8200, and PF1140, PL1880, PL
Affinity systems (trade name) such as 1840 and PM1570 can be mentioned.

Ethylene laminated on both sides of the inner layer film
The vinyl acetate copolymer film has MI at 190 ° C.
Is 0.3-5 g / 10 min. Those obtained from the copolymer of More preferably 0.5 to 3 g /
10 min. It is. MI is 0.3 g / 10 min. When it is less than the above range, the strength of the obtained film becomes high, and the function as the packaging film for the purpose of the present application is not satisfied. or,
5 g / 10 min. If it exceeds, the resilience to deformation and the shrinkage rate upon heating decrease, and wrinkles and the like after packaging cannot be eliminated, which is not preferable. Further, those having a vinyl acetate content of 5 to 25 wt% are preferable. More preferably, it is 10 to 15 wt%. If it is less than 5% by weight, proper self-adhesiveness is deteriorated and a problem such as detachment of the seal portion occurs. When it exceeds 25 wt%, the heat resistance is lowered and problems such as holes being formed in the film during heating for heat shrinkage occur, and the function as the packaging film for the purpose of the present application is not satisfied.

When shrink-wrapping is applied and the object to be packaged is film-wrapped, wrinkles formed on the film surface of the package are eliminated by heat treatment. Whether or not the wrinkles are eliminated is affected by the heat shrinkability of the packaging film. When the heat shrinkage is high, the wrinkles formed on the surface of the packaging film are easily eliminated by heating after packaging. Since the shrinkage ratio is affected by the stretching conditions such as the stretching ratio of the film, if only the shrinkage ratio is considered,
It is preferably stretched at a high ratio. However, it is necessary to stretch under appropriate conditions because the film may be broken by stretching. From this viewpoint, the shrinkage rate of the packaging film on an area basis is at least 15 at 80 ° C.
%, At least 25% at 100 ° C. and at least 35% at 120 ° C. In consideration of breakage of the film due to stretching, the upper limit of the shrinkage ratio at 120 ° C or lower is preferably 60% or lower.

Incidentally, it is optional to add additives such as an antioxidant, a lubricant, an antiblocking agent and a surfactant to each resin forming the inner layer and the outer layer of the packaging film of the present invention. Examples of the antiblocking agent include inorganic compounds such as silica, diatomaceous earth, clay, talc, and zeolite. In addition, in order to impart appropriate slipperiness and antifogging property, the following additives can be added depending on the application.

As the surface active agent, a surface active agent conforming to the PL standard (list of food additives), glycerin fatty acid (C
₈ -C ₂₂₎ esters, sorbitan fatty acid (C ₈ -C ₂₂₎ esters, propylene glycol fatty acid (C ₈ -C ₂₂₎ esters, sucrose fatty acid (C ₈ -C ₂₂₎ esters, citric acid mono- (di- or tri-) stearic acid esters, pentaerythritol fatty acid (C ₈ -C ₁₈₎ esters, polyglycerin fatty acid (C ₈ -C ₁₈₎ esters, polyoxyethylene (20) glycerin fatty acid (C ₁₂ -C ₁₈₎ esters, polyoxyethylene (20 ) Sorbitan fatty acid (C
₁₂ -C ₁₈₎ esters, polyethylene glycol fatty acid (C ₈ ~C ₂₂₎ esters, polypropylene glycol fatty acid (C ₈ ~C ₁₈₎ esters.

Examples of the lubricant include paraffin wax, microcrystalline wax, liquid paraffin,
Paraffins such as polyethylene wax and polypropylene wax, hydrocarbon resins, fatty acids such as stearic acid and hydroxystearic acid, stearoamide, oxystearoamide, oleylamide, erucylamide, ricinolamide, methylenebisstearamide, methylenebisstearo. Examples thereof include fatty acid amides such as behenamide and ethylene bis stearamide, and fatty acid esters such as n-butyl stearate and methyl hydroxy stearate.

These additives may be added singly or as a mixture of two or more kinds to any layer of the laminate. The addition amount of these additives is preferably 15 parts by weight or less based on 100 parts by weight of the total amount of the resin forming the inner layer or the outer layer of the laminate.

The method for producing the resin composition for the inner layer and the resin composition for the outer layer containing the above additives is not particularly limited, and a known method can be applied. For example, using a ribbon blender, a Henschel mixer, a high-speed mixer, etc., a method of mixing each resin and additives at room temperature or a temperature in the vicinity thereof, kneading using an extruder, melting and extruding, and forming into pellets. And the like.

The packaging film of the present invention is produced by inflation molding the resin composition prepared by the above method under specific conditions. The blow ratio in inflation molding is preferably in the range of 2.5 to 4.5 in consideration of the strength, heat shrinkability, extensibility, resilience to deformation, flexibility and the like of the obtained film. The blow ratio means the ratio of the diameter of the blow-up film to the diameter of the die slit of the annular die installed in the extruder.

As the inflation molding method, a known method is adopted. For example, the following method can be exemplified as a method for forming a laminated film composed of three layers according to the present invention. Using three extruders, 15 layers of raw material resin were prepared for each layer.
After kneading and melting at 0 to 250 ° C., preferably 170 to 220 ° C., the mixture is supplied to an annular die, laminated in the die, and extruded in a tubular shape from the annular die lip. Then, from the inside of the annular die to the inside of the tubular molding,
It is drawn by a take-up machine while being supplied with air or the like at a temperature of about -40 ° C and stretching. As a cooling method at the time of picking up, an air cooling type, a water cooling type, or the like is used. Usually, the stretching conditions (blow ratio) are adjusted by the supply rate of air or the like and the temperature (cooling rate).

The thickness of the packaging film of the present invention is not particularly limited, but is usually 5 to 30 μm, and the proportion of the inner layer film is 10 to 90% of the total thickness.

[0024]

The present invention will be described below in further detail with reference to examples. The characteristic values shown in the examples were evaluated by the following methods. (1) Recovery from deformation Automatic packaging machine [Push-up type made by Ishida Co., Ltd., type: Mar
Styrofoam tray (25 cm)
3 tomatoes placed on (× 15 cm) are packaged to form a package. After applying a concave deformation to the film surface of the package with fingers, the recoverability is visually observed. The evaluation criteria are as follows. ◯: No concave deformation remains. X: A slight amount of concave deformation remains.

(2) Suitability for automatic packaging 100 packages are obtained in the same manner as in the preceding paragraph. The film surface of the obtained package is observed for wrinkles, tears, and tray deformation. The evaluation criteria are as follows. ◯: No wrinkles, tears in the film, and no deformation of the tray. X: One or more packages in which wrinkles, tears in the film, and deformation of the tray were observed.

(3) Heat shrinkage rate (%) The sample film was cut into 10 × 10 cm, and the film was cut at 80 ° C. and 100%.
After leaving it in an oven heated to 120 ° C. for 5 minutes, it is allowed to cool to room temperature. The shrinkage rate (area) of the film after heating is measured.

(4) Wrinkle Remaining Area (cm ² ) A package is obtained in the same manner as in the item (1) except that wrinkles having a total area of 375 cm ² are left on the film surface. The obtained package is passed through a tunnel at 80 ° C. for 1 second, and the area where wrinkles remain is examined.

Example 1 S-LLDPE (manufactured by The Dow Chemical Company: trade name: ENGAGE-EG-8200, MI: 5 g / 1
0 min, density: 0.87 g / cm ³ ) as a raw material for the inner layer, and kneading and melting at 190 to 215 ° C. by using an extruder (manufactured by Alpine Co., Ltd.) having a caliber of 50 mm and L / D: 21 to form an annular three layer It was supplied to the inner layer supply part (190 ° C.) of the die. On the other hand, 100 parts by weight of ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar Co., Ltd., trade name: NUC3722) and 1.5 parts by weight of monoglycerin oleate (manufactured by Riken Vitamin Co., Ltd., trade name: OL-100). The raw material containing is kneaded and melted at 170 to 200 ° C. using an extruder (manufactured by Alpine Co., Ltd.) having a diameter of 35 mm and L / D: 21 to form a ring 3
It was supplied to the outer layer supply section (190 ° C.) of the layer die. Each molten resin layer supplied to the annular three-layer die is
The inner layer was made of S-LLDPE film, and the ethylene-vinyl acetate copolymer film was laminated on both sides of the film so as to be the outer layer, and was extruded into a cylindrical shape from the die lip (205 ° C.) at a blow ratio of 4.2. Stretched, 3
The thickness of the laminated layers is 12 μm (inner layer: 4 μm, outer layer:
A packaging film having 4 μm of 2 layers) was obtained. Each property of the obtained packaging film was evaluated by the above methods. The results obtained are shown in [Table 1].

Example 2 As the resin for the inner layer, S-LLDPE (manufactured by The Dow Chemical Company: trade name: ENGAGE-EG-810)
0, MI: 1 g / 10 min, density: 0.87 g / cm
¹² μm in the same manner as in Example 1 except that ³ ) was used.
m packaging film was obtained. Each property of the obtained packaging film was evaluated by the above methods. The results obtained are shown in [Table 1].

Example 3 As the resin for the inner layer, S-LLDPE (manufactured by The Dow Chemical Company: trade name: ENGAGE-EG-815)
0, MI: 0.5 g / 10 min, density: 0.868 g
/ Cm ³ ) was used in the same manner as in Example 1 to obtain a packaging film having a total thickness of 12 μm. Each property of the obtained packaging film was evaluated by the above methods. The results obtained are shown in [Table 1].

Example 4 As the resin for the inner layer, S-LLDPE (manufactured by The Dow Chemical Company: trade name: AFFINITY-PF-1)
140, MI: 1.6 g / 10 min, density: 0.89
A packaging film having a total thickness of 12 μm was obtained in the same manner as in Example 1 except that 5 g / cm ³ ) was used. Each property of the obtained packaging film was evaluated by the above methods. The results obtained are shown in [Table 1].

Comparative Examples 1-2 As inner layer resins, PP, Z-LLDPE, polybutene-1 (manufactured by Shell Chemical Co., trade name: M0200, density: 0.915 g / cm ³ , MI: 1.8 g / 10 mi)
n, hereinafter referred to as PB-1), propylene-ethylene-
Butene-1 random copolymer (ethylene content: 2% by weight, butene-1 content: 13% by weight, density 0.896 g
/ Cm ³ , hereinafter referred to as P-E-B-1), or ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar Co., Ltd.,
A packaging film having a total thickness of 12 μm was obtained in the same manner as in Example 1 except that the trade name: NUC3722) was used in parts by weight shown in [Table 1]. However, the kneading and extrusion temperature in Comparative Example 2 was 160 ° C, and the die temperature was 185 ° C. Each property of the obtained packaging film was evaluated by the above methods. The results obtained are shown in [Table 1].

[0033]

[Table 1]

[0034]

The packaging film of the present invention has a slipping property as a packaging film, self-adhesion, heat-sealing property, transparency,
It retains the same properties as conventional products in terms of extensibility and flexibility. Further, it has excellent heat shrinkability and resilience to deformation, and when used for high-speed automatic packaging by the shrinking method, no wrinkles are left on the package, so that the appearance of the package is not impaired. Very useful as a packaging film.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location B32B 27/32 103 B32B 27/32 103 (72) Inventor Ikuo Akai 2-chome Tango-dori, Minami-ku, Aichi Prefecture Address Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Yasuo Sasaki 2-1, Tango Dori, Minami-ku, Aichi Prefecture Nagoya Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. An ethylene-vinyl acetate copolymer film is laminated on both sides of an inner layer film obtained from an ethylene-α-olefin copolymer polymerized using a single-site catalyst, and a blow ratio of 2.5. A film for packaging, which is inflation-molded at a pressure of up to 4.5. 2. The melt flow rate at 190 ° C. of the ethylene-α-olefin copolymer polymerized by using a single-site catalyst is 0.5 to 10 g / 10 minutes. Packaging film. 3. The total thickness of the packaging film is 5 to 30 μm.
And the ratio of the inner layer film to the total thickness is 10
The packaging film according to claim 1, wherein the packaging film is about 90%. 4. The areal shrinkage of the packaging film is 80 ° C.
2. The packaging film according to claim 1, wherein the packaging film is at least 15%, at 100 ° C. is at least 25%, and at 120 ° C. is at least 35%.