JPH0976427A - Stretch packaging laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a well balanced stretch packaging laminated film free from swelling of food or generation of whitening even if hot food is subjected to stretch packaging, in particular high in steam permeability and also excellent in packing aptitude. SOLUTION: A stretch packing laminated film is obtained by laminating a layer (B) composed of an ethylene/vinyl acetate copolymer resin with vinyl acetate content of 5-40wt.% and ethylene content of 95-60wt.% on at least the single surface of a base material layer (A) based on a styrene/butadiene block copolymer with styrene content of 60-95wt.% and butadiene content of 40-5wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch film for packaging foods, and more particularly to a laminate film for stretch packaging having high water vapor permeability and excellent packaging suitability.

[0002]

2. Description of the Related Art In recent years, foods such as fruits and vegetables, fresh fish, fresh meats, side dishes, etc. are placed directly or on a plastic tray, and these are stretch-wrapped with a film, so-called pre-packaging film, which is environmentally friendly. Instead of a conventional polyvinyl chloride film, a linear low-density polyethylene film (Japanese Patent Laid-Open No. 64-14018) or a linear low-density polyethylene is used as an intermediate layer, and an ethylene-vinyl acetate copolymer film is laminated on the front and back surfaces. Three-layer film (Japanese Patent Publication No. 2-18953, JP-A-3-258542)
(See Japanese Laid-Open Patent Publication No. 57-2). A high-density polyethylene film is used as an intermediate layer, and a high-pressure low-density polyethylene film is laminated on the front and back surfaces of the film (Japanese Patent Laid-Open No. 57-2.
For example, a packaging film having an ethylene resin as a base material, such as Japanese Patent No. 10853), has been put into practical use.

[0003] These ethylene resin packaging films are:
Widely used for packaging fruits, vegetables and side dishes. However, in the case of side dishes such as dumplings and croquettes that wrap food while hot, the water vapor permeability of the film is low, so many water droplets are generated in the package, and the water droplets, for example, sprinkle the dumplings, even during croquette. Had problems such as whitening.

For the purpose of improving these drawbacks, Japanese Examined Patent Publication 6
No. 3,560,65 discloses a flexural modulus of 10,000.
On at least one side of a film made of a homopolymer or copolymer resin of ω-laurolactam having a Kg / cm ² or less,
94 to 99.8% by weight of (A ′) ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 5 to 25% by weight, and (B ′) sorbitan fatty acid ester and its ethylene oxide adduct, Described is a laminated film for stretch packaging in which a resin film containing 0.2 to 6% by weight of one selected from mono- and polyglycerin fatty acid ester, sucrose fatty acid ester, glycerin ricinoleic acid ester and glyceryl acetylricinoleate is laminated. There is.

However, when the stretched laminated film is stretched at the time of packaging, it stretches unevenly, and the extremely thin portion has a sharp corner on the food to be packaged or the food to be packaged is placed. If the corner of the placed tray is sharp, there is a drawback that it will break from this contact part,
In addition, there is a problem that the film is wrinkled due to the non-uniform elongation, so that it cannot be packaged with a commercial value. There is also a problem that the intermediate layer resin is expensive.

Furthermore, the laminated film for stretch packaging is
It has not always been possible to sufficiently meet the demands of the market in deformation recovery such as recovery of wrinkles without leaving wrinkles during transportation of packages and deformation of the film surface at the time of store display.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems in laminated films for stretch packaging of foods, and its object is to provide appropriate slipperiness, self-adhesiveness, and anti-fogging property. In addition to having transparency and transparency, it is to provide a stretch wrapping film that has high water vapor permeability and is extremely excellent in wrapping suitability, that is, extensibility, flexibility, and deformation recovery. .

[0008]

In order to solve the above problems, the invention according to claim 1 of the present invention provides a styrene content of 6
A vinyl acetate content of 5 to 5 is provided on at least one side of the base material layer (A) containing a styrene-butadiene block copolymer resin of 0 to 95% by weight and a butadiene content of 40 to 5% by weight as a main component.
The present invention relates to a laminated film for stretch packaging, which comprises a layer (B) made of an ethylene-vinyl acetate copolymer resin having an ethylene content of 40 to 40% by weight and an ethylene content of 95 to 60% by weight. The invention according to claim 2 is the base material layer (A).
Has a styrene content of 60 to 95% by weight and a butadiene content of 4
0 to 5 wt% styrene-butadiene block copolymer resin 51 to 99 wt% and styrene content 5 to 40 wt%,
The laminated film for stretch packaging according to claim 1, which comprises 1 to 49% by weight of a styrene-conjugated diene block copolymer elastomer having a conjugated diene content of 95 to 60% by weight.

Hereinafter, the present invention will be described in detail. The laminated film for stretch packaging of the present invention comprises two kinds of layers, a base material layer (A) containing a styrene-butadiene block copolymer resin as a main component and a layer (B) containing an ethylene-vinyl acetate copolymer resin. It is a composition. The main component of the base material layer (A) is a styrene content of 60 to 95% by weight and a butadiene content of 4
It is a styrene-butadiene block copolymer resin of 0 to 5% by weight and has a flexural modulus (ASTM D790) of 10
000 to 20000 Kgf / cm ² is used.

If the styrene content of the styrene-butadiene block copolymer resin is less than 60% by weight, sufficient water vapor permeability cannot be obtained, while if it exceeds 95% by weight, the film becomes hard, which is not preferable. Such a styrene-butadiene block copolymer resin is sold by Asahi Kasei Kogyo Co., Ltd. under the trade name of "Asaflex".

The base layer (A) contains 1 to 49 styrene-conjugated diene block copolymer elastomers having a styrene content of 5 to 40% by weight and a conjugated diene content of 95 to 60% by weight for the purpose of improving packaging suitability. % By weight. It is preferably 20 to 40% by weight. Examples of the styrene-conjugated diene block copolymer elastomer include a styrene-butadiene block copolymer elastomer and a styrene-isoprene block copolymer elastomer.

If the amount of the styrene-conjugated diene block copolymer elastomer blended is less than 1% by weight, the effect is small, and if it exceeds 49% by weight, the water vapor permeability of the obtained film tends to be insufficient. Such a styrene-conjugated diene block copolymer elastomer is sold by Asahi Kasei Kogyo Co., Ltd. under the trade name of "Tafprene".

Further, a hydrogenated product of a styrene-conjugated diene block copolymer can be used in place of the styrene-conjugated diene block copolymer elastomer. Another type of layer of the laminated film for stretch packaging of the present invention is a layer (B) made of an ethylene-vinyl acetate copolymer resin. This ethylene-vinyl acetate copolymer resin has a vinyl acetate content of 5 to 40% by weight and an ethylene content of 95%.
~ 60 wt% ethylene-vinyl acetate copolymer resin, the vinyl acetate content is preferably 5-25 wt%. MFR of ethylene-vinyl acetate copolymer resin (JI
(SK-7210; 190 ° C., 2.16 kg load) is preferably 0.1 to 10 g / 10 min in terms of appearance and suitability for packaging.

If the vinyl acetate content is less than 5% by weight, the resulting laminated film may have a poor appearance, or the film may be too hard to obtain uniform extensibility during stretch packaging.
On the other hand, there are problems such as wrinkles in the package and breaks in extremely thin parts. On the other hand, when it exceeds 40% by weight, the resulting laminated film may be sticky or blocked.

The layer (B) has, for example, an aliphatic group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, in order to impart antifogging property, moderate slipperiness, self-adhesion property and antistatic property. Alcohol and carbon number 10-22, preferably 12-18
Aliphatic alcohol fatty acid ester that is a compound with a fatty acid of, specifically, monoglycerin oleate, polyglycerin oleate, glycerin triricinoleate,
Glycerin acetyl ricinoleate, polyglycerin stearate, polyglycerin laurate, methyl acetyl ricinoleate, ethyl acetyl ricinoleate, butyl acetyl ricinoleate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, Polypropylene glycol oleate, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate, etc., and polyalkylene ether polyols, specifically polyethylene glycol, polypropylene glycol, etc., and paraffinic oils 0.1 to at least one compound selected from
It is preferable to add 10% by weight, preferably 1 to 5% by weight.

These additives may be added to the base material layer (A) containing a styrene-butadiene copolymer resin as a main component in an amount of 0.1 to 10% by weight. The stretch packaging laminated film of the present invention is a co-extrusion method in which the resin constituting the base material layer (A) and the resin constituting the layer (B) are subjected to inflation molding or T-die molding using a plurality of extruders. Alternatively, it is laminated and formed by a known method such as an extrusion laminating method.

Among them, the coextrusion method by inflation molding is preferable in order to obtain a laminated film in which mechanical strength such as tear strength in the machine direction and the transverse direction are sufficiently balanced.
The blow ratio at that time is 3 to 20 times, preferably 5 to 18 times. The blow ratio here means a ratio of the circumferential length of the final blown film to the circumferential length of the die slit of the die.

Further, the film obtained as described above is heated to a temperature not higher than the crystallization temperature of the resin and drawn 1.2 to 5 times in the machine direction of the film by utilizing the speed difference between the nip rolls. I don't mind. Regarding the thickness of the laminated film for stretch packaging, the total thickness is 8 to 30 μm, of which the base material layer (A) is 1 to 10 μm and the layer (B) is 3 to 3 as a single layer.
It is preferably 10 μm.

The laminated film for stretch packaging of the present invention has a water vapor permeability of 300 to 1000 g / m ² · 2.
It is preferably 4 hours · atm, and even when hot side dishes such as dumplings and croquettes are packaged, the contents do not become fuzzy or whiten, which is suitable as such a packaging film.

[0020]

EXAMPLES The contents and effects of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The physical properties, practicality and packaging suitability of the film are as follows.

<Tensile Rupture Strength and Tensile Rupture Elongation> JIS Z-1702 <Tensile Elastic Modulus> JIS K-7113 <Water Vapor Permeability> JIS Z-0208 <Deformation Recovery Strain Amount> Using the device shown in FIG. , Diameter 20
After pressing a mmφ piston rod into the center of the film at a speed of 500 mm / min, the piston rod was retracted and the amount of strain at which the scratches caused by the piston rod disappeared after 3 minutes was taken as the deformation recovery strain amount.

<Preservability> After placing a croquette having a surface temperature of 60 ° C. on a tray made of expanded polystyrene, stretch wrapping with a laminated film and observing the state of the croquette after 1 hour with the naked eye, the results are as follows. Evaluated to. When there is no particular change: ○, when the croquette is whitened by water droplets: ×.

<Expandability> The croquettes are placed on trays made of expanded polystyrene, expanded polystyrene, and impact-resistant polystyrene, respectively, and packed by a stretch automatic packing machine, A-18X [trade name] manufactured by Fujikikai Co., Ltd. The result of visually observing the stretched state of the film at that time was evaluated as follows. When the film stretched almost uniformly: ○, when the film stretched unevenly: ×.

<Rate of Occurrence of Breakage> Packaging was performed in the same manner as in the extensibility evaluation, and the presence or absence of breakage of the film at that time was visually observed. <Situation of Wrinkles> Packaging was performed in the same manner as in the extensibility evaluation, and the presence or absence of wrinkles in the film at that time was visually observed.

Example 1 As a resin for the base material layer (A), a styrene-butadiene copolymer resin [density 1.01 g / cm ³ , flexural modulus 120] was used.
00 Kgf / cm ² , styrene content 70% by weight; product name "Asaflex 810F" manufactured by Asahi Kasei Corporation.]
With an extruder having a diameter of 65 mm and an L / D25 of 200.
Kneading at a temperature of ℃, on the other hand, as a resin for the layer (B), ethylene-vinyl acetate copolymer resin [vinyl acetate content 15 wt%, density 0.938 g / cm ³ , melting point 97 ℃; Mitsubishi Chemical Corporation, Product name "Mitsubishi Polyechie EVA LV44
0 "] 98.5% by weight and sorbitan oleate [manufactured by Riken Vitamin Co., Ltd., trade name" Rikemar O250 "]
A resin composition consisting of 1.5% by weight has a caliber of 50 mm and L
/ D25 extruder at 170 ° C., and both are supplied to one annular three-layer die to form a 5.5 μm-thick layer on each side of a 2 μm-thick base layer (A). B) is laminated so that the die temperature is 200 ° C. and the blow ratio is 10 times, so that the total thickness is 13 μm.
A laminated film for stretch packaging (5.5 μm / 2 μm / 5.5 μm) was produced. Table 1 shows the physical properties, practicality and packaging suitability of this film.

Example 2 In Example 1, the resin for the base material layer (A) was 60% by weight of the styrene-butadiene copolymer resin used in the same example, the styrene-butadiene copolymer elastomer [density 0.95].
g / cm ³ , styrene content 40% by weight; Asahi Kasei Kogyo Co., Ltd., trade name "Tafpren 125"] 40% by weight
A laminated film for stretch packaging having a three-layer structure was produced in the same manner as in the same example except that the resin composition was replaced by the following resin composition.
Table 1 shows the physical properties, practicality and packaging suitability of this film.

Example 3 In Example 1, the resin for the base material layer (A) was the same as the styrene-butadiene copolymer resin 78.5% by weight used in the same example.
Hydrogenated product of styrene-butadiene block copolymer [density 0.89 g / cm ³ , styrene content 20% by weight;
Product name "Tuftec H105" manufactured by Asahi Kasei Corporation
2 "] 20% by weight and diglycerin oleate [manufactured by Riken Vitamin Co., Ltd., trade name" Rikemar O71D "]
Instead of the resin composition of 5% by weight, the resin for layer (B) was replaced by the ethylene-vinyl acetate copolymer resin 9 used in the same example.
Three-layer structure in the same manner as in the same example except that the resin composition was 8.5 wt% and diglycerin oleate [manufactured by Riken Vitamin Co., Ltd., trade name "Rikemar O71D"] 1.5 wt%. A laminated film for stretch packaging was manufactured. Table 1 shows the physical properties, practicality and packaging suitability of this film.
Shown in

Comparative Example 1 In Example 1, the resin for the base material layer (A) was nylon 1
2/6 copolymer resin [density 1.02 g / cm ³ , melting point 1
55 ° C .; manufactured by Daicel Huls Co., Ltd., trade name “DAIAMIDE N1901”], except that a laminated film for stretch packaging having a three-layer structure was manufactured in the same manner as in the same example. Table 1 shows the physical properties, practicality and packaging suitability of this film.
Shown in

[0029]

[Table 1]

[0030]

EFFECT OF THE INVENTION The laminated film for stretch packaging of the present invention has a high water vapor permeability, and even when hot side dishes such as dumplings and croquettes are packaged, the contents do not become fuzzy or whiten, and the packaging suitability is high. It is an excellent and well-balanced laminated film for stretch packaging.

[Brief description of drawings]

FIG. 1 is a plan view of an apparatus for measuring a deformation recovery strain amount of a film.

[Explanation of symbols]

 1 piston rod 2 film (sample) 3 load cell

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08L 53/02 LLY C08L 53/02 LLY

Claims (3)

[Claims] 1. A vinyl acetate content of 5 to 5 is provided on at least one side of a base material layer (A) mainly comprising a styrene-butadiene block copolymer resin having a styrene content of 60 to 95 weight% and a butadiene content of 40 to 5 weight%. A laminated film for stretch packaging, comprising a layer (B) made of 40% by weight ethylene-vinyl acetate copolymer resin having an ethylene content of 95-60% by weight. 2. The base material layer (A) has a styrene content of 60-9.
5% by weight, styrene-butadiene block copolymer resin 51-99% by weight, styrene content 5-40% by weight, butadiene content 40-5% by weight, conjugated diene content 95-60
The laminated film for stretch packaging according to claim 1, which comprises 1 to 49% by weight of a styrene-conjugated diene block copolymer elastomer. 3. The laminated film for stretch packaging according to claim 2, wherein the styrene-conjugated diene block copolymer elastomer is a hydrogenated product of a styrene-conjugated diene block copolymer.