JP3288810B2 - Shrinkable multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrinkable multilayer film made of an ethylene resin suitable for shrink wrapping and the like.

[0002]

2. Description of the Related Art Conventionally, shrink wrapping is characterized in that the appearance of the wrapping is beautiful, that it has a display effect, and that the value of the product is enhanced. In addition, the contents are kept hygienic and the quality can be easily checked visually. In addition, since irregularly shaped articles and a large number of products can be packaged quickly and tightly, they are widely used for packaging foods and miscellaneous goods. In an automatic packaging machine for shrink wrapping, the contents are wrapped with a little extra space, and the contents are passed through a shrink tunnel heated by a heater, etc., and when heat is applied by a fan motor, the film shrinks and the product shrinks. A tightly packed package can be made, and a tight and beautiful package can be made. The properties required for the film for this use include strength, shrinkage, sealing properties (especially fusing sealing properties), surface display properties such as transparency and anti-fogging properties (especially foods), and heat resistance (microwave ovens). (Characteristics that can withstand use)) are comprehensively required.

As a film suitable for shrink wrapping and the like, a thermoplastic film mainly comprising polyethylene, polypropylene, or polyvinyl chloride is generally known.
In a heat-shrinkable film using polyvinyl chloride, a plasticizer and a heat stabilizer to be added and used in combination are not hygienic,
Disposal and incineration have environmental protection and hygiene problems. For these reasons, polyolefin-based shrink films have been used in recent years.

Japanese Patent Application Laid-Open No. Sho 60-240451 discloses a linear low-density polyethylene (hereinafter referred to as "LLDPE") as a shrink film for packaging particularly used for foods and the like.
And two surface layers comprising linear medium density polyethylene and ethylene-vinyl acetate copolymer (hereinafter referred to as "EVA") and L
A crosslinked film having a layer made of LDPE is disclosed, and JP-A-1-301251 discloses a crosslinked film having a density of 0.
Two surface layers composed of an ethylene-α-olefin copolymer of 870 to 0.915 g / cm ³ and a density of 0.915 to 0.15 g / cm ³ .
A biaxially stretched film having a core layer made of an ethylene-α-olefin copolymer of 930 g / cm ³ is disclosed, and JP-A-3-138148 discloses a film having a density of 0.9.
A multilayer film having two surface layers made of an ethylene-α-olefin copolymer having a thickness of 00 to 0.925 g / cm ³ and EVA, and a core layer made of a high-pressure low-density polyethylene (hereinafter referred to as “LDPE”). Are disclosed.

The film described in JP-A-60-240451 is characterized by having excellent heat sealability and a gradual shrinkage-temperature curve. However, the transparency, particularly the transparency after shrinkage, is low. Has the disadvantage of decreasing,
Further, the bleeding property of the antifogging agent is poor, and it is difficult to impart the antifogging property. The film described in JP-A-1-301251 is said to be characterized by excellent low-temperature sealability and good packaging suitability, but is similarly insufficient in anti-fogging properties and extremely poor in heat resistance. It cannot be used in microwave ovens. As long as the film described in JP-A-3-138148 is cross-linked, the film has sufficient heat resistance and satisfactory overall characteristics, but the film has a weak strength and is not suitable for practical use. On the other hand, when shrink wrapping is performed, problems such as tearing of the film from the air vent hole may occur, and depending on the type of the wrapping machine, the running property is somewhat difficult.

As described above, at present, a shrink wrapping film that satisfies all the characteristics required for efficiently packing foods and the like with an automatic wrapping machine has not been obtained.

[0007]

One object of the present invention is to provide a polyethylene-based multilayer film satisfying characteristics such as packaging suitability and surface display characteristics. An object of the present invention is to provide a shrinkable multilayer film having heat resistance that can endure the use of a microwave oven in addition to the characteristics.

[0008]

That is, the present invention provides an ethylene-α-olefin copolymer of 10 to 90% by weight,
EVA, ethylene-aliphatic unsaturated carboxylic acid copolymer,
10 to 90% by weight of at least one copolymer selected from ethylene-aliphatic unsaturated carboxylic acid ester copolymers
And a surface layer composed of a resin mixture of at least one and an inner layer composed of at least two other layers, at least one of which is a polymer layer mainly composed of a high-pressure low-density polyethylene, Another object of the present invention is to provide a shrinkable film characterized in that one layer comprises at least four layers which are polymer layers containing an ethylene-α-olefin copolymer as a main component.

Hereinafter, the present invention will be described in detail. The ethylene-α-olefin copolymer used for the surface layer of the present invention is a so-called linear ethylene, for example, butene-1, pentene-1, At least one α-olefin having 3 to 18 carbon atoms such as hexene-1, 4-methylpentene-1 and octene-1 and preferably hexene-1, 4-methylpentene-1 and octene-1 are commonly used. It is polymerized. The density of the ethylene-α-olefin copolymer is in the range of 0.870 to 0.940 g / cm ³ , preferably 0.890 to 0.925 g / cm ^3.
cm ³ , more preferably 0.905 to 0.915 g / c
m is ^3. When the density is less than 0.870 g / cm ^{3, the} surface of the film tends to be sticky, which may cause blocking during storage of the film or cause trouble due to similar causes during the packaging operation. 9
If it exceeds 40 g / cm ³ , compatibility with EVA tends to decrease, and transparency (particularly transparency after shrinkage) decreases.

The EVA used in the surface layer of the present invention has a vinyl acetate group content of 5 to 26% by weight, preferably 7 to 2% by weight.
0% by weight, more preferably 10 to 17% by weight. Those having a vinyl acetate group content of less than 5% by weight are inferior in transparency, while those having a vinyl acetate group content of more than 26% by weight are inferior in extrusion moldability, tend to have a strong odor of acetic acid, and tend to be sticky. Further, as the ethylene-aliphatic unsaturated carboxylic acid copolymer and the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, an ethylene-acrylic acid copolymer,
Ethylene-methacrylic acid copolymer, ethylene-acrylate (C such as methyl, ethyl, propyl, butyl, etc.)
₁ chosen from ingredients of alcohol -C ₈₎ copolymer,
Ethylene-methacrylic acid ester (selected from C _{1 to} C ₈ alcohol components such as methyl, ethyl, propyl and butyl) copolymers and the like. These are multi-component copolymers of three or more components further added with other components (for example,
Free tertiary or more copolymers selected from ethylene, aliphatic unsaturated carboxylic acids and the same esters, or modified products thereof). The components to be copolymerized may be at least two or more multi-component copolymers selected from the above or other components. The content of these carboxylic acid or carboxylic acid ester groups is usually 3 to 35% by weight, preferably 3 to 25% by weight in consideration of a reduction in packaging work due to blocking of a film or a decrease in waist. More preferably, it is 3 to 20% by weight.

The ethylene-α-olefin copolymer (former) of the surface layer of the present invention and at least one selected from EVA, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer and the like. The ratio of one type of polymer (the latter) is from 90 to 10% by weight of the former to 10 to 90% by weight of the latter, preferably from 80 to 10% by weight of the former.
The latter is 20 to 65% by weight relative to 35% by weight. When the latter ratio is less than 10% by weight, for example, the kneading property with a surfactant and an antifogging agent and the bleeding property are inferior, so that the antifogging property is deteriorated. On the other hand, if the content of the latter component is more than 90% by weight, the heat sealing properties, particularly the fusing sealing properties, will be poor.

The high-pressure low-density polyethylene used as a main component of the inner layer of the present invention may be a commercially available ethylene homopolymer having a long chain branch or a small amount of α-ethylene.
It contains a copolymer modified with an olefin. or,
Further, those commonly used as modified polyethylene obtained by copolymerizing the following comonomers copolymerizable with ethylene at 10% by weight or less, for example, those containing EVA having a vinyl acetate group content of 10% by weight or less, etc. "Predominantly" means that the high-pressure method low-density polyethylene has a ratio of at least 50% by weight or more, for example, high-density polyethylene, LLDPE, ultra-low density ("VLDPE",
Soft polymers composed of polyethylene, ethylene-aliphatic unsaturated carboxylic acid polymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, α-olefin copolymer (for example, those called “ULDPE”) One or more α-olefins selected from ethylene and / or propylene and an α-olefin having 4 to 12 carbon atoms, or a soft copolymer composed of a free combination,
Its crystallinity by X-ray method is generally 30% or less, which is different from the above-mentioned resin group), olefin-based polymer such as polypropylene, polybutene-based polymer and poly4-methylpentene-based polymer. It is contained in a range of less than 50% by weight.

Next, the linear ethylene-α-olefin copolymer used as a main component in the other inner layer is the same as that used for the surface layer in the case of ethylene and, for example, butene-1, pentene -1, hexene-1, 4
-Having 3 to 3 carbon atoms such as methylpentene-1 and octene-1
A copolymer of at least one α-olefin selected from the group consisting of hexene-1,4-methylpentene-
1, those obtained by copolymerizing octene-1 are more preferred. The density of this ethylene-α-olefin copolymer is 0.87
It is in the range of 0 to 0.940 g / cm ³ , preferably in the range of 0.900 to 0.940 g / cm ³ , more preferably in the range of 0.915 to 0.935 g / cm ³ . If the density is less than 0.870 g / cm ^3, the strength, elastic modulus, stiffness, etc. of the film decrease, and
Those with 40 g / cm ³ or more tend to have poor transparency (especially transparency after shrinkage) even when used as an internal layer. The linear ethylene-α-olefin copolymer as the main component may be mixed with another polymer as long as the original properties are not impaired, as in the case of the high-pressure method low-density polyethylene. It is.

Since the polymer layer mainly composed of the high-pressure method low-density polyethylene and the polymer layer mainly composed of the ethylene-α-olefin copolymer coexist as an internal layer, optical properties such as transparency are improved. Achieves stable stretch film-forming properties while maintaining excellent properties such as anti-fogging properties and sealing properties, especially excellent film forming stability in high-magnification biaxial stretching, and tearing from air holes during shrink packaging. This eliminates troubles such as the above, and has excellent film running properties, and the finished product after shrink wrapping is free from wrinkles at the corners, so that it is much improved as compared with the prior art.

The film of the present invention comprises 10 to 90% by weight of an ethylene-α-olefin copolymer which forms a surface layer, an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, and an ethylene-aliphatic copolymer. A resin layer (A) comprising a mixed resin of 10 to 90% by weight of at least one copolymer selected from unsaturated carboxylic acid ester copolymers;
And a polymer layer (B) mainly composed of a high-pressure low-density polyethylene as an inner layer and an ethylene-α-olefin copolymer layer (C). For example, in the case of four layers:
In the case of five layers such as A / B / C / A: A / B / C / B / A,
In the case of 7 layers such as A / C / B / C / A, A / B / A / C / A, etc .: A / B / A / C / A / B / A, A / B / A / B / C
/ B / A, A / B / C / A / C / B / A, A / C / B /
A / B / C / A, A / C / A / B / A / C / A, A / C
/ B / C / A / C / A, A / B / A / C / A / C / A,
A / B / A / B / A / C / A, A / B / C / A / B / C
/ A, A / B / C / B / A / C / A, and the like, but not limited thereto, and also includes the case of six layers, eight layers, and more.

When two or more layers (A), (B) or (C) are provided, the resins constituting these layers may be the same or different, respectively. The (A) layer is a multilayer of different polymers (copolymer components of each resin, copolymer ratio, mixed composition, etc.), for example, A
₁ / A ₂ or the like, and the same applies to the (B) layer or the (C) layer. In this case, there is no particular limitation on the method of forming the multilayer, and any method may be used from conventional methods such as a coextrusion method, a laminating method, and a coating method. Is preferred.

Further, as long as the characteristics of the film of the present invention are not impaired, at least one other layer composed of another resin may be used inside.

These layers may have a gas barrier property of an ethylene-vinyl alcohol copolymer, a polyamide polymer, a polyester polymer, or an acrylonitrile polymer. A combination of a layer and an adhesive layer may be used.

When a heat-shrinkable film is to be obtained, it is preferred that the film be stretched and oriented, and depending on the shrinkage required according to a commonly used method, about 2 to 10 times per uniaxial or biaxial direction. Stretching is preferred.
Commonly used methods include a roll stretching method, a tenter method,
Although there is no particular limitation, such as a bubble stretching method, a method of forming a film by simultaneous biaxial stretching is preferable. Also, if necessary, after processing,
For example, heat setting, lamination with another film, or the like may be performed.

The total thickness of the heat shrinkable film of the present invention is not particularly limited, but is usually 100 to 1000 μm when used as a sheet, and preferably 5 to 100 μm when used as a film. If the thickness is less than 5 μm, the film tends to have insufficient stiffness and is easily torn, which causes a problem in workability during packaging. The thickness of the layer (A) on the surface is preferably 5 to 60% of the entire film,
Preferably it is 10 to 50%. If it is less than 5%, the seal strength is low, and the transparency is reduced. If it is more than 60%, the performance is excessive. The thickness of the layer (B), which is one of the intermediate layers, is suitably used in the range of 10 to 80%, and preferably in the range of 20 to 60%. If it is 10% or less, stretching stability, uneven thickness, and low-temperature shrinkage are poor. Further, the thickness of the layer (C) is suitably used in the range of 10 to 80%, and preferably in the range of 20 to 60%. If it is less than 10%, the film will have poor mechanical strength such as tear strength and elastic modulus.

As a preferable method for imparting heat resistance in addition to heat shrinkability, a crosslinking treatment is carried out so that the gel fraction of the film becomes 1 to 50% before or after stretching or both. preferable. As a crosslinking method,
First, energy beam irradiation is mentioned. As the energy beam, there are ionizing radiations such as ultraviolet rays, electron beams, X-rays, α-rays, γ-rays, and neutron rays, and preferably electron beams. It is also possible to carry out crosslinking by adding a crosslinking agent and heating it to a temperature not lower than the decomposition temperature of the crosslinking agent. Combination with energy beam irradiation may be used, and other known crosslinking methods may be used.
At this time, preferably, an electron beam (energy: 100 KV
１1 MV) to freely crosslink the surface layer (one or both), the inner layer, and the like. In that case, the gel fraction is 1-3
More preferably, the content is 5% by weight. Further, the polymer layer of the present invention may contain a surfactant and an anti-fogging agent to such an extent that each intrinsic property is not impaired, for example, a polyhydric alcohol moiety such as sorbitan fatty acid ester, glycerin fatty acid ester, and polyglycerin fatty acid ester. Fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, and other ethylene oxide adducts, alkylamines, alkylamides, alkylethanols Amine,
Amines such as alkylethanolamides, amides, polyalkylene glycols, granidine derivatives, phosphate-containing surfactants, sulfonic acid derivatives, quaternary ammonium salts, pyridinium salts, imidazoline derivatives, polyvinyl alcohol, acrylic acid hydrophilicity It may be a polymer, a polymer having a pyrrolidium ring in its main chain, or a mixture containing at least one or more of silica sol, alumina sol, etc., and these surfactants and antifogging agents may be added to the surface layer. It is used in the range of 0.2 to 5% by weight, preferably in the range of 0.4 to 4% by weight. When it is less than 0.2% by weight, effects such as antifogging property and antistatic property are not sufficient, and %, The kneading property is reduced and the surface is stained. These additives may be added to at least one of the inner layers. It is preferred. In particular, in order to exhibit properties such as anti-fogging property and antistatic property at an early stage, and to improve the durability, it is preferable to add a large amount to the inner layer rather than the surface layer. Is preferably 0.5 to 6% by weight. Further, depending on the case, the surface layer may be subjected to various coating treatments with a known treatment agent including the above-mentioned additives by a known method separately from (or in addition to) the above.

The film of the present invention can be used as an antioxidant, an ultraviolet absorber, a plasticizer, a blocking inhibitor, and the like, which are usually used for plastic films as long as the intended purpose is not impaired.
A slip agent, a lubricant, an antistatic agent, an inorganic filler, and the like may be contained as desired. These are contained in at least one of the resin layers constituting the film of the present invention. When it is necessary to prevent slippage and blocking with the packaged object while maintaining the above, it is also effective to use an antiblocking agent, a slip agent, a lubricant, etc. only on one surface layer in contact with the packaged object. .

The film of the present invention is suitable mainly for packaging materials, particularly shrink wrapping, but is also a film that can be used as a wrap film for home use or business use.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

The measuring method and evaluation method in the examples are as follows. (1) Gel fraction A sample was extracted with boiling p-xylene, and the ratio of the insoluble portion was represented by the following formula (1), and used as a measure of the degree of crosslinking.

[0026]

(Equation 1) However, for a polymer that has not been cross-linked and is not completely dissolved in boiling p-xylene, the measurement is performed by appropriately changing to a solvent that can be completely dissolved at the time of boiling instead of p-xylene. (2) Film-forming stability The stability at the time of inflation film-forming of a film was evaluated according to the following criteria, depending on the thickness of the film.

◎: Uneven thickness less than ± 10% and bubble does not sway ○: Uneven thickness ± 10 to 20% and slightly bubble swaying Δ: Larger than ± 20% and large bubble sway × : Inflation-insensitive (3) Anti-fogging property A film beaker containing 20 ° C. water was covered with a film 3 days after the film formation, and left in a refrigerator at 5 ° C. for 1 hour. The evaluation was made based on the following criteria.

5: Mirror-like water film formed 4: Slightly uneven water film 3: Spread water droplets attached 2: Small water droplets attached 1: White cloudy, content (4) Tensile modulus was measured according to ASTM-D-882-81 method. (5) Tear strength Measured according to JIS-P-8116 using a light load tear tester (manufactured by Toyo Seiki). The value was the average value of the tear strength in the longitudinal and transverse directions. The reading of the measurement here is
The measurement was performed so as to fall within the range of 20 to 60 on the scale. If there was a difference in the measured value depending on the measurement range, the higher value was adopted. (6) Fusing seal strength 0.5mmR × 280mm for Sentinel heat sealer
Attach L fusing blade, 140-240 ° C, 30psi,
Fusing and sealing two 15mm-wide films under the condition of 0.5 seconds, immediately fix one end of the film, apply a load to the other end, and measure the load when peeling off the seal at 20 ° C intervals The maximum load was defined as the strength. (7) Haze after shrinkage Using a hot air tunnel, the film was shrunk at an area shrinkage ratio of 30%, and then measured by ASTM-D-1003 method. In addition,
As the temperature, a minimum temperature (90 to 150 ° C.) at which the above-described shrinkage can be achieved in a hot air tunnel passing time of 5 seconds was employed. (8) Suitability of packaging machine Using a linear packaging machine (manufactured by Omori Machinery Co., Ltd.), a packaging test was carried out under the condition of 40 packs / min using a lunch box and chopsticks as contents. This packaging machine supplies the contents at a constant pitch from the film to the place where it became cylindrical via a former,
After the center sealing is performed continuously, the top sealing is performed, and after rough packaging, the film is shrunk by hot air to tightly package. The air holes were formed by a mechanical drilling method using a pin having a sharp tip of about 0.4 mmφ. Evaluation of packaging suitability was performed according to the following criteria.

(1) Running stability (running failure is expressed as a variation in the fusing seal interval was used as an evaluation criterion) A: The fusing seal interval is constant and stable O: The fusing seal interval slightly varies △: Large variation in fusing seal interval ×: Film tearing during packaging (2) Slippery ◎: Film is slippery with machine and contents ○: Film is caught by machine Sounding △: Film is caught by the machine, causing packaging loss of 5% or more. ×: Same as above, loss of 10% or more. (3) Puncture (opens when heated with hot air or tears from air holes.) : No puncture is generated. の も の: Puncture less than 3% when heated with hot air. △: Puncture is 3% or more and less than 10% when heated with hot air. X: All punctured after fusing seal ( Four ) Finish (wrinkles, tears) ◎: A film that can be tightly packaged without wrinkles or tears ○: Somewhat loose packaging or tears are rarely observed △: Some wrinkles or tears in the package × : Wrinkles or tears in the package Next, the resins used in Examples and Comparative Examples are described below.

VLDPE-1: ethylene-α-olefin copolymer (density = 0.910 g / cm ³ , MI = 3.6 g / 10
Min, comonomer = 4-methylpentene) VLDPE-2: ethylene-α-olefin copolymer (density = 0.890 g / cm ³ , MI = 3.3 g / 10
Min, comonomer = 1-octene) LLDPE-1: ethylene-α-olefin copolymer (density = 0.930 g / cm ³ , MI = 2.1 g / 10
Min, comonomer = 4-methylpentene) LLDPE-2: ethylene-α-olefin copolymer (density = 0.920 g / cm ³ , MI = 2.1 g / 10
Min, comonomer = 1-octene) LLDPE-3: ethylene-α-olefin copolymer (density = 0.926 g / cm ³ , MI = 2.0 g / 10
Min, comonomer = 1-octene) LLDPE-4: acid-modified ethylene-α-olefin copolymer (density = 0.920 g / cm ³ , MI = 3.5 g /
LDPE-1: high pressure method low density polyethylene (density = 0.10 minutes, comonomer = 1-octene)
LDPE-2: High-pressure low-density polyethylene (density = 0.09 g / cm ³ , MI = 2.0 g / 10 min)
LDPE-3: high-pressure low-density polyethylene (density = 0.9 g / cm ³ , MI = 0.5 g / 10 min)
920 g / cm ³ , MI = 0.4 g / 10 min) EVA-1: ethylene-vinyl acetate copolymer (density =
EVA-2: ethylene-vinyl acetate copolymer (density = 0.935 g / cm ³ , vinyl acetate content = 15% by weight, MI = 2.3 g / 10 min)
EVA-3: ethylene-vinyl acetate copolymer (density = 0.930 g / cm ³ , vinyl acetate content = 10% by weight, MI = 1.3 g / 10 min)
0.940 g / cm ³ , vinyl acetate content = 18% by weight, MI = 2.5 g / 10 min) EMA-1: ethylene-methyl acrylate copolymer (density = 0.940 g / cm ³ , methyl acrylate) Content =
8.9% by weight, MI = 3.0 g / 10 min) EAA-1: Ethylene-acrylic acid copolymer (density =
0.920 g / cm ³ , acrylic acid content = 6.4 wt%, MI = 3.5 g / 10 min) EVOH-1: Ethylene-vinyl alcohol copolymer (density = 1.140 g / cm ³ , ethylene content) Amount = 3
EVOH-2: ethylene-vinyl alcohol copolymer (density = 1.170 g / cm ³ , ethylene content = 2) 3.3% by weight, MFI = 3.5 g / 10 min
8.1 wt%, MFI = 3.5 g / 10 min) PA-1: Nylon-6 (density = 1.140 g / c)
m ³ ) (Examples 1 to 12, and Comparative Examples 1 to 5) 40% by weight of VLDPE-1 and EVA- were added to the surface layer extruder.
60% by weight of the mixture of 1 in the extruder for the inner layer (1)
DPE-1 was added to the extruder for the inner layer (2) by LLDPE-1.
, And co-extruded using a five-layer die and rapidly cooled to obtain a surface layer / inner layer (1) / inner layer (2) / inner layer (1) / surface layer = 70 μ / 110 μ / 90 μ / 110 μ.
/ 70μ, a total of 450μ of a tubular film was formed. At that time, 2% by weight of diglycerin monooleate as a nonionic surfactant and 3% by weight of the inner layer (1) were injected into the extruder and kneaded. This tubular film was flattened and subjected to irradiation crosslinking by an electron beam irradiation device having an acceleration voltage of 500 KV. At this time, after adjusting the degree of cross-linking so that the gel fraction of all layers becomes 20%, the mixture was heated so that the temperature at the stretching start point became 150 ° C., and stretched MD 6.8 times and TD 6.6 times. 10
A film having a thickness of μ was obtained, and this was designated as Example 1.

In addition, the same as in Example 1 according to the types and blending ratios of the resins, the types and amounts of the nonionic surfactants, and the gel fractions as shown in Tables 1, 2 and 3. I got a film. This was applied to Examples 2 to 12 and Comparative Example 1.
To 5.

Explaining these films, Examples 1 to 9 and 11 are five-layer films having respective layer ratios, and Example 10 is a surface layer / inner layer (1) / inner layer (2).
/ Inner layer (3) / Inner layer (2) / Inner layer (1) / Surface layer = 67.5μ / 67.5μ / 67.5μ / 45μ / 6
7.5μ / 67.5μ / 67.5μ, total 450μ
This is a 7-layer film prepared by preparing a tube-shaped film of Example 2 above, subjecting it to electron beam irradiation treatment in the same manner as in Example 1, and stretching and forming a film. In Example 12, the surface layer / the inner layer (1) / the inner layer (2) were used.
/ Inner layer (3) / Inner layer (2) / Inner layer (1) / Surface layer = 67.5μ / 90μ / 45μ / 45μ / 45μ / 90
Example 1 except that a tube-shaped film of μ / 67.5μ and a total of 450μ was prepared and electron beam irradiation was not performed.
The film is stretched and formed in the same manner as described above, and is a 20 μm film. Comparative Examples 3, 4, and 5 correspond to the prior art, respectively.
138148, JP-A-1-301251,
This is a film corresponding to JP-A-60-240451, and has a surface layer / inner layer (1) / surface layer = 1.5 μ / 7 μ.
/1.5μ This is a three-layer film with a total of 10μ. Tables 1, 2 and 3 show that these films have film forming stability, anti-fogging property, transparency after shrinkage, tensile elastic modulus, tear strength, and fusing seal, which are important values for machine packaging. The strength and suitability of the packaging machine are also described.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3] The films of Examples 1 and 2 of the present invention were excellent in stretch film forming property, that is, high in productivity, and had little variation in film thickness. In addition, the film has stiffness, non-ionic surfactant which has the effect as a slip agent and anti-fogging agent is moderately bleed, running stability and slipperiness are good, and fusing seal can be firmly performed Was something. In the packaging test, it was possible to perform packaging stably, tightly package without wrinkles or tears, and was extremely excellent in packaging workability.

In Comparative Example 1, although the surface layer was made of only VLDPE, the fusing sealability was good, but the antifogging property was poor and the transparency after shrinkage was poor, and it was difficult to use as a film. . In addition, regarding the suitability of the packaging machine, the bleeding of the nonionic surfactant is bad,
The film was inferior in slipperiness, wrinkled in the packaged film, and poor in transparency.

In Comparative Example 2, the bleed of the nonionic surfactant was good because the surface layer was only EVA, and the transparency and antifogging property after shrinkage were good, but the fusing seal strength was low.
Since the fusing seal strength was lower than the shrinkage stress at the time of shrinkage after packaging with a margin, almost no seal was peeled off and packaging was impossible. There was a problem that the seal was peeled off during packaging.

The film of Comparative Example 3 had good stretch film forming properties, fusing seal strength, transparency after shrinkage, and anti-fogging properties, but had poor tear strength, so that air was evacuated when shrinking depending on the size of the lunch container. Some of the films caused tearing of the film from the holes for use, and all of Comparative Examples 1 to 3 were inferior in packaging workability and were difficult to use.

The film of Example 3 was prepared by adding a mixture of oleamide: erucamide = 1: 1 to the surface layer resin for the purpose of improving the releasability and slipperiness. This film is stretched and formed by the same method as described above, and this film has good stretch film forming properties and good fusing seal strength, and is particularly excellent in the slipperiness and peelability of the film and the lunch box. The film could be opened.

A film stretched and formed in the same manner as in Example 1 except that a tubular film was formed in the same manner as in Example 1 with the resin and nonionic surfactant shown in Tables 1 and 2 was used. Examples 4 to 9 and 11 will be described. Examples 4 to 9 and 11
Has excellent film-forming stability, high productivity, excellent transparency and antifogging properties, and has a high display effect at the time of packaging. Further, the film was excellent in fusing seal strength and tear strength, and had good running stability and slipperiness even in a packaging test, and could achieve tight packaging without wrinkles or tears.

In Comparative Examples 4 and 5 corresponding to the prior arts of JP-A-1-301251 and JP-A-60-240451, although the fusing seal strength was fair, the transparency of the film was poor. In particular, the antifogging property was poor, and the surface display properties were poor. Further, in the packaging test, running stability and slipperiness were poor due to poor bleeding of the nonionic surfactant, many wrinkles were observed after packaging, and packaging workability was poor.

Examples 10 and 12 which are four-type seven-layer films
Also, it was excellent in film-forming properties, surface display properties, and fusing seal strength, and was able to be stably packaged without wrinkles or tears even in a packaging test. Furthermore, since a resin having excellent gas barrier properties is used for the inner layer, the film has high gas barrier properties.

(Example 13) A film was formed by stretching in the same manner as in Example 3 except that dimethylpolysiloxane was added to the surface layer in an amount of 0.1% by weight based on the resin. This film was also excellent in film formability (◎), surface display properties, and fusing seal strength as in Example 3. In addition, since the film has excellent slipperiness and adhesion, it can be stably packaged without wrinkles or tears even in the packaging test, and the film can be easily opened without the sticking of the lunch box and the film. there were.

(Example 14) As an additive to be used for the surface layer, a fine powdered silica was used in combination with 0.1% by weight based on the resin of the surface layer, and was stretched in the same manner as in Example 3 to produce a product. The membrane was made. Stretched film is stable (◎), especially in the subsequent packaging test, almost no tearing from air holes and little wrinkling, excellent continuous packaging workability, and openability after packaging lunch box case It was excellent.

(Example 15) The same resin as in Example 1 was used for each surface layer resin, and one more surface layer extruder was further added. A surface layer on one side was formed with a composition containing 1.5% by weight of diglycerin monooleate, and 1.5% by weight of diglycerin monooleate was added as an additive to the other surface layer extruder. Each surface layer was formed, and the other steps were carried out in the same manner as in Example 1 to obtain a five-layer tube-like film. Thereafter, a film having a thickness of 10 μm was stably obtained. This film was subjected to a packaging test in which the surface layer to which silica was added was brought into contact with a lunch box, and the finished product was extremely good, excellent in gloss and transparency, and had an appropriate anti-fog property (4). However, it was also easy to open.

[0046]

The film of the present invention has a high degree of suitability for packaging machine such as slipperiness and mechanical strength, and is excellent in surface display characteristics such as transparency and anti-fogging property. And a beautifully finished package.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-138148 (JP, A) JP-A-1-301251 (JP, A) JP-A-60-240451 (JP, A) JP-A-60- 154065 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. An ethylene-α-olefin copolymer 10
And 90% by weight of at least one copolymer selected from ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic acid ester copolymer. A surface layer composed of a mixed resin of 90% by weight and an internal layer composed of at least two other layers, at least one of which is a polymer layer mainly composed of a high-pressure low-density polyethylene, A shrinkable multilayer film comprising at least four layers, wherein at least one other layer is a polymer layer mainly composed of an ethylene-α-olefin copolymer.