JP2021112918A - Heat shrinkable laminated film, and packaging material using the film - Google Patents

Abstract

To provide a heat shrinkable laminated film excellent in oxygen gas barrier property, shrinkability and transparency.SOLUTION: A heat shrinkable laminated film is formed of at least three layers having (I) layer and (II) layer on surface and back layers, where each of the layers contain the following resins as main components, oxygen permeability at 23°C 0%RH is 10 cc/m2 day atm or less, and thermal shrinkage of the film when immersed in hot water of 80°C for 10 seconds is 30% or more at least in one direction. (I) A layer is at least one polyester-based resin. (II) A layer is at least one ethylene-vinyl acetate copolymer.SELECTED DRAWING: None

Description

The present invention relates to a heat-shrinkable film having excellent oxygen gas barrier properties, shrinkage, and transparency. Specifically, the present invention has heat-shrinkability suitable for packaging of foods, pharmaceuticals, industrial chemicals, etc. The present invention relates to a laminated film and a packaging material using this heat-shrinkable laminated film.

Conventionally, a film using an ethylene-vinyl acetate copolymer saponified product (EVOH) has been used as a packaging material having a high oxygen barrier property. However, the EVOH single-layer film has problems in printability and pinhole resistance, and it is difficult to use the single-layer film as a base film for packaging materials.
On the other hand, as a method of coating according to the shape of the contents, there is a method of using a heat-shrinkable film. Polystyrene-based resins and polyester-based resins are generally used as the resins constituting the heat-shrinkable film, but since these do not have sufficient oxygen barrier properties, applications requiring oxygen blocking properties. For example, it was difficult to use it for packaging foods, pharmaceuticals, industrial chemicals and the like.

Attempts to use EVOH have been studied in order to impart oxygen barrier properties to heat-shrinkable films. However, since it is difficult to impart shrinkage to EVOH, a film having a sufficient shrinkage rate, a uniform shrinkage finish without wrinkles and unevenness, and no problem with shrinkage stability over time is available. The current situation is that it has not been put into practical use. As a heat-shrinkable film using EVOH, for example, Patent Document 1 describes a multilayer shrink film having a layer in which EVOH having a 1,2-diol structural unit in a side chain and EVOH having no structural unit are blended. Is disclosed. The technique of Patent Document 1 is to improve shrinkage by blending two kinds of EVOH, and although shrinkage is obtained, there is no specification regarding continuity from film formation to stretching, and it is extreme after stretching. It is hard to say that the productivity is sufficient because it is rapidly cooled. Moreover, the oxygen barrier property is 10 cc / m ² , day, atm or more, and it cannot be said that it is sufficient. On the other hand, the transparency has not reached the high level required for the heat-shrinkable film, and improvement has been desired.

Japanese Unexamined Patent Publication No. 2007-261075

The present invention has been made in view of the above problems, and is excellent in oxygen gas barrier property, shrinkage property, and transparency, and has heat shrinkage property suitable for packaging of foods, pharmaceuticals, industrial chemicals, etc., which are reluctant to deteriorate the contents due to oxygen. The purpose is to provide a laminated film.

As a result of diligent studies, the present inventors have succeeded in obtaining a laminated film capable of solving the above-mentioned problems of the prior art, and have completed the present invention. That is, the object of the present invention is achieved by the following heat-shrinkable laminated film (hereinafter, "film of the present invention").

That is, the subject of the present invention is a heat-shrinkable laminated film composed of at least three layers having a (I) layer as a front and back layer and a (II) layer as a central layer, and each layer contains the following resin as a main component. The oxygen permeation rate at 23 ° C. 0% RH is 10 cc / m ² · day · atm or less, and the heat shrinkage rate of the film in at least one direction when immersed in warm water at 80 ° C. for 10 seconds is 30% or more. It is solved by a heat shrinkable laminated film characterized by.
Layer (I): At least one polyester resin (II) Layer: At least one ethylene-vinyl acetate copolymer saponified product

According to the present invention, since a heat-shrinkable laminated film having excellent oxygen gas barrier properties, shrinkage, and transparency can be obtained, it is suitable for packaging foods, pharmaceuticals, industrial chemicals, etc., which are reluctant to deteriorate the contents due to oxygen. Can be used for.

Hereinafter, the film of the present invention and the packaging material of the present invention as an example of the embodiment of the present invention will be described. However, the scope of the present invention is not limited to the embodiments described below.

In addition, in this specification, "as a main component" means that it is allowed to contain other components as long as it does not interfere with the action and effect of the resin contained as the main component. Further, although the term does not limit the specific content, it is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and 100% by mass or less of the total components. It is a component that occupies the range of.

<Film of the present invention>
<Front and back layers: (I) layer>
The layer (I) of the film of the present invention is composed mainly of at least one polyester-based resin.

<Polyester resin>
Examples of the polyester resin in the present invention include terephthalic acid as a dicarboxylic acid component and ethylene glycol as a polyhydric alcohol component, that is, a copolymer having an ethylene terephthalate unit as a main constituent unit.

In the polyester resin of the present invention, ethylene glycol is used to form an ethylene terephthalate unit in 100 mol% of the polyhydric alcohol component. Other polyhydric alcohol components other than ethylene glycol include triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol. , 3-Methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, 1,10 -Alkylene glycols such as decanediol, 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanediol, 1,4 -Alicyclic diols such as cyclohexanedimethanol, trimethylolpropane, glycerin, pentaerythritol, diethylene glycol, dimerdiol, polyoxytetramethylene glycol, polyethylene glycol, bisphenol compounds or derivatives thereof, such as alkylene oxide adducts. It can be appropriately selected and used in combination with ethylene glycol.

The alicyclic diol component can be combined with a single copolymer by partially mixing the alicyclic diol compound in the diol compound when the dicarboxylic acid compound and the diol compound are reacted to obtain a polyester resin. Can be mentioned. Further, a polyester resin obtained by reacting a dicarboxylic acid compound and an alicyclic diol compound is synthesized, and mixed with a polyester resin obtained by reacting the dicarboxylic acid compound with a diol compound such as ethylene glycol other than the alicyclic diol compound. Can be mentioned.

In the polyester resin of the present invention, terephthalic acid is used to form an ethylene terephthalate unit in 100 mol% of the polyvalent carboxylic acid component. In addition, aromatic dicarboxylic acids, their ester-forming derivatives, aliphatic dicarboxylic acids and the like can also be used in combination. Examples of the aromatic dicarboxylic acid include isophthalic acid, naphthalene-1,4- or -2,6 dicarboxylic acid, 5-sodium sulfoisophthalic acid, 1,4-cyclohexanedicarboxylic acid, orthophthalic acid, phenylenedioxydiacetic acid, 4 , 4'-diphenyldicarboxylic acid, 4,4'-diphenoxyetanedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6- Examples thereof include naphthalenedicarboxylic acid or an ester-forming derivative thereof. Examples of the aliphatic dicarboxylic acid include glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, succinic acid, dimer acid, malonic acid or an ester-forming derivative thereof. These are appropriately selected and can be used in combination with terephthalic acid.

The aromatic dicarboxylic acid component is a single copolymer by partially mixing an aromatic dicarboxylic acid compound with the dicarboxylic acid compound when the dicarboxylic acid compound and the diol compound are reacted to obtain a polyester resin. Can be mentioned. Further, a polyester resin obtained by reacting an aromatic dicarboxylic acid compound with a diol compound is synthesized, and mixed with a polyester resin obtained by reacting the diol compound with a dicarboxylic acid compound such as terephthalic acid other than the aromatic dicarboxylic acid compound. Can be mentioned.

The polyester resin used for the layer (I) in the present invention is composed of a polyethylene terephthalate copolymer (copolymer A) and a polybutylene terephthalate copolymer (copolymer B) from the viewpoint of imparting shrinkage. It is preferable to be done.
When the polyester resin used for the layer (I) is composed of the copolymer A and the copolymer B, various heat shrinkage behaviors of the film of the present invention can be improved. That is, since the Tg of the copolymer A and the Tg of the copolymer B are significantly different, by mixing both, the temperature range in which the heat shrinkage rate of the film increases when used in a heat shrinkable film can be expanded. As a result, the rapid shrinkage of the film from the start of heat shrinkage can be suppressed. That is, by containing a predetermined amount of the copolymer A and suppressing the crystallinity of the copolymer B, a sufficient shrinkage rate of the film is brought about, and a rapid heat treatment without a preheating step in the shrinkage process of the heat-shrinkable film. However, the appearance of the film is not deteriorated, and the film can be suppressed from becoming brittle with time.

<Polyethylene terephthalate copolymer A>
The copolymer A constituting the polyester resin used for the layer (I) of the present invention preferably contains terephthalic acid and isophthalic acid as dicarboxylic acid components. Terephthalic acid is contained in 100 mol% of the total dicarboxylic acid component constituting the copolymer A in a proportion of 85 to 100 mol%, preferably 87 to 93 mol%, and more preferably 88 to 92 mol%. When terephthalic acid is contained in an amount of 85 mol% or more of the total dicarboxylic acid components, high crystallinity can be obtained, so that sufficient strength can be ensured for the heat-shrinkable film.

The copolymer A preferably contains ethylene glycol, 1,4-cyclohexanedimethanol and diethylene glycol as diol components. Ethylene glycol is contained in 65 to 80 mol%, preferably 75 to 80 mol%, and more preferably 76 to 79 mol% in 100 mol% of the total diol components constituting the copolymer A. High crystallinity can be obtained by including 65 mol% or more of ethylene glycol in 100 mol% of the total diol component, so that sufficient strength can be secured in the heat-shrinkable film, and crystallization is performed by setting the upper limit to 80 mol%. Can be reduced and amorphous.

The amount of 1,4-cyclohexanedimethanol contained in the copolymer A is 20 mol% or more and less than 35 mol%, preferably 20 to 25 mol%, more preferably 20 mol% or more, more preferably 20 to 25 mol% in 100 mol% of all diol components constituting the copolymer A. Can be contained in an amount of 21 to 24 mol%. By setting the content of 1,4-cyclohexanedimethanol in the total diol component to 20 mol% or more, good impact resistance can be exhibited in the heat-shrinkable film, and further, by setting the upper limit to less than 35 mol%. Fluctuations in flow characteristics during melting can be suppressed, and good shrinkage finish can be achieved.

The diethylene glycol contained in the copolymer A is contained in less than 12 mol%, preferably less than 10 mol%, and more preferably less than 8 mol% in 100 mol% of the total diol components constituting the copolymer A. By setting the content of diethylene glycol to less than 12 mol%, the embrittlement of the obtained heat-shrinkable film with time can be suppressed.

The glass transition temperature (Tg) of the copolymer A is 70 to 80 ° C. When Tg exceeds 80 ° C, the shrinkage start temperature is high in the heat-shrinkable film, and the adhesion to the contents is insufficient. When Tg is lower than 70 ° C, the elastic modulus at high temperature is low and wrinkles occur during shrinkage. It will be easier.

<Polybutylene terephthalate copolymer B>
The copolymer B constituting the polyester resin used for the layer (I) of the present invention preferably contains terephthalic acid and isophthalic acid as dicarboxylic acid components. Terephthalic acid is contained in 100 mol% of the total dicarboxylic acid component constituting the copolymer B in a proportion of 85 to 95 mol%, preferably 87 to 93 mol%, and more preferably 88 to 92 mol%. When terephthalic acid is contained in an amount of 85 mol% or more of the total dicarboxylic acid components, high crystallinity can be obtained, so that sufficient strength can be ensured for the heat-shrinkable film.

The isophthalic acid contained in the copolymer B together with the terephthalic acid is 5 mol% or more and less than 15 mol%, preferably 7 to 13 mol%, more preferably 7 to 13 mol% in 100 mol% of the total dicarboxylic acids constituting the copolymer B. Contains 8-12 mol%. If 5 mol% or more of isophthalic acid is contained in the total dicarboxylic acid component, the crystallinity can be lowered and good printing and sealing suitability can be obtained in the heat-shrinkable film. Further, when the upper limit of isophthalic acid is less than 15 mol%, a copolymer having good fracture resistance can be obtained in the heat-shrinkable film, which is preferable.

The copolymer B preferably contains 1,4-butanediol as a diol component. It is preferable that 100 mol% of 1,4-butanediol is contained in the total diol component because sufficient strength can be secured.

The glass transition temperature (Tg) of the copolymer B is preferably as low as possible, and is usually 45 ° C. or lower, preferably 40 ° C. or lower. When Tg exceeds 45 ° C., when a heat-shrinkable film is used, the shrinkage start temperature is high and the adhesion to the contents becomes insufficient.

The polyester resin used for the layer (I) of the present invention is composed of the above-mentioned copolymer A and the copolymer B, and the content of the copolymer A is 80 to 90% by mass, preferably 82 to 88% by mass. More preferably, it is 83 to 87% by mass, and the copolymer B is 10 to 20% by mass, preferably 12 to 18% by mass, and further preferably 13 to 17% by mass. The polyester resin used for the layer (I) of the present invention cannot be obtained as a film composed of the copolymer A alone or the copolymer B alone by mixing the copolymer A and the copolymer B in the above range. It can exhibit low temperature and high shrinkage resistance and fracture resistance. That is, by setting the lower limit of the content of the copolymer A to 80% by mass, when a heat-shrinkable film is produced, fracture resistance with time is suppressed, and the upper limit is set to 90% by mass. By doing so, it is possible to suppress a rapid rise in the shrinkage rate of the film and to prevent appearance defects such as uneven shrinkage. Further, by setting the lower limit of the content of the copolymer B to 10% by mass, shrinkage in a low temperature range can be obtained, and rapid shrinkage in a high temperature range can be suppressed to suppress uneven shrinkage. Further, by setting the upper limit of the copolymer B to 20% by mass, the produced film does not shrink at room temperature, dimensional stability at room temperature can be obtained, and it can be made difficult to break.

Examples of commercially available polyester-based resins include "EMBRACE" (manufactured by Eastman Chemical Co., Ltd.), "Novapex" (manufactured by Mitsubishi Chemical Corporation), and "Novaduran" (manufactured by Mitsubishi Chemical Corporation).

<Other ingredients>
In addition to the polyester-based resin, the (I) layer of the film of the present invention may be mixed with other resins as long as the effects of the present invention are not impaired. Specific examples of other resins include polyethylene, polypropylene, modified maleic anhydrides thereof, polyolefin resins such as ionomer, thermoplastic resins such as polyamide resins and polystyrene resins, and thermoplastic elastomers.

<Central layer: (II) layer>
The (II) layer of the film of the present invention is composed mainly of at least one ethylene-vinyl acetate copolymer saponified product.

<Ethylene-vinyl acetate copolymer saponified product>
The ethylene-vinyl acetate copolymer saponified product used for the (II) layer of the film of the present invention is obtained by saponifying an ethylene-vinyl acetate copolymer. Further, as a copolymerization component, α-olefins such as propylene, isobutene, octene, dodecene and octadecene; hydroxy groups such as 3-butene-1-ol, 4-pentene-1-ol, 3-butene-1,2-diol Contains α-olefins and esters thereof; hydroxy group-containing α-olefin derivatives such as acylates; unsaturated carboxylic acids or salts thereof, partially alkyl esters, fully alkyl esters, nitriles, amides or anhydrides; unsaturated sulfonic acids or The salt; vinylsilane compound; vinyl chloride; styrene and the like may be contained. Further, the ethylene-vinyl acetate copolymer saponified product may be post-modified such as urethanization, acetalization, cyanoethylation, and oxyalkyleneization. These may be used alone, or if necessary, two or more kinds having different compositions such as ethylene content and saponification degree may be mixed and used.

The ethylene content in the ethylene-vinyl acetate copolymer saponified product is preferably 20 mol% or more and 45 mol% or less. The lower limit is more preferably 25 mol% or more, still more preferably 30 mol% or more. The upper limit is more preferably 40 mol% or less. Generally, when the ethylene content is high, the moldability is excellent, but the gas barrier property tends to decrease, and the ethylene content should be within the above range from the viewpoint of the film moldability and the balance between the shrinkage property of the obtained film and the gas barrier property. Is preferable.

The saponification degree of the ethylene-vinyl acetate copolymer saponification is usually 90 mol% or more, preferably 95 mol% or more, and more preferably 98 mol% or more. When the degree of saponification is within the above range, sufficient gas barrier properties can be obtained, which is preferable.

The MFR (210 ° C., load 2.16 kg) of the ethylene-vinyl acetate copolymer saponified product is usually 1 to 50 g / 10 minutes, preferably 1 to 30 g / 10 minutes, and more preferably 2 to 20 g / 10 minutes. Is. If the MFR is within the above range, there will be no practical problem regarding stretchability and processability when the film is formed.

The content of the ethylene-vinyl acetate copolymer saponified product in the (II) layer of the film of the present invention is preferably 50% by mass or more when the resin composition constituting the (II) layer is 100% by mass. , More preferably 70% by mass or more, still more preferably 90% by mass or more. When the content of the ethylene-vinyl acetate copolymer saponified product in the layer (II) is within the above range, sufficient gas barrier properties can be obtained.

In addition to the ethylene-vinyl acetate copolymer saponified product, the (II) layer of the film of the present invention may be mixed with other resins as long as the effects of the present invention are not impaired. Specific examples of other resins include polyethylene, polypropylene, modified maleic anhydrides thereof, polyolefin resins such as ionomer, thermoplastic resins such as polyamide resins and polystyrene resins, and thermoplastic elastomers.

<Adhesive resin>
The adhesive resin used in the (III) layer of the film of the present invention is not particularly limited as long as it improves the interlayer adhesiveness between the (I) layer and the (II) layer, but among them, the main component of the (I) layer. A resin having both a site having reactivity or affinity with the polyester-based resin and a site having an affinity with the ethylene-vinyl acetate copolymer saponified product of the layer (II) is preferably used.

Here, "having reactivity or affinity with a polyester resin" means having a functional group having a high affinity with the polyester resin or a functional group capable of reacting with the polyester resin. Examples of functional groups having such properties include acid anhydride groups, carboxylic acid groups, carboxylic acid ester groups, carboxylic acid compound groups, carboxylic acid amide groups, carboxylic acid bases, sulfonic acid groups and sulfonic acid ester groups. , Functional groups such as sulfonated groups, sulfonic acid amide groups, sulfonic acid bases, epoxy groups, amino groups, imide groups, or oxazoline groups, among which acid anhydride groups, carboxylic acid groups, or carboxylic acid esters. Groups are preferred.

Further, the "site having an affinity with the ethylene / vinyl acetate copolymer saponified product" means having a functional group or a chain having an affinity with the ethylene / vinyl acetate copolymer saponified product, and more specifically. , Means having a linear or branched saturated hydrocarbon moiety as a main chain, a block chain, or a graft chain.

Other preferable resins used for the adhesive layer include soft polyester-based resins, soft polyolefin-based resins, copolymers of styrene-based hydrocarbons and conjugated diene hydrocarbons, and hydrogenated resins thereof. Specific examples of the soft polyolefin resin include soft linear low-density polyethylene, low crystalline polypropylene resin, ethylene-vinyl acetate copolymer, and the like, and styrene-based hydrocarbons and conjugated diene-based hydrocarbons. Examples of the copolymer with the above include styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-ethylene-butadiene copolymer, styrene-ethylene-propylene copolymer, styrene-ethylene-butylene copolymer and the like. Can be mentioned.

An example of a commercially available resin having a functional group having a high affinity with the polyester resin or being reactive with the polyester resin and compatible with the ethylene / vinyl acetate copolymer saponified product is an acid-modified polyolefin resin. "Admer" (manufactured by Mitsui Chemicals), "Modic" (manufactured by Mitsubishi Chemicals), "Modiper" (manufactured by Nichiyu), "Bondain" as an ethylene-vinyl acetate-maleic anhydride copolymer (manufactured by Alchema) , Ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate ternary copolymer, ethyl ethylene-glycidyl methacrylate ternary copolymer as "Bond First" (manufactured by Sumitomo Chemical Co., Ltd.), As an acid-modified styrene-based thermoplastic resin, "Tough Tech M" (manufactured by Asahi Kasei Chemicals Co., Ltd.), "Epofriend" (manufactured by Daicel Co., Ltd.), a copolymer of a styrene-based hydrocarbon and a conjugated diene-based hydrocarbon, or hydrogenation thereof. As resins, "Tough Tech H" (manufactured by Asahi Kasei Chemicals), "Clayton" (manufactured by Clayton Polymer Japan), "Dynaron" (manufactured by JSR), "Septon" (manufactured by Clare), "Hybler" (manufactured by Clare) ), "Tough Plain" (manufactured by Asahi Kasei Chemicals), "Primaloy" (manufactured by Mitsubishi Chemicals), etc.

<Layer structure>
The structure of the film of the present invention is such that it has at least three layers having a (I) layer on the front and back layers and a (II) layer on the central layer, and further (between the (I) layer and the (II) layer ( III) A structure having at least 5 layers provided with layers is preferable. Further, if necessary, other layers can be further laminated in order to impart various functions.

<Layer ratio>
The thickness ratio of each layer of the film of the present invention is not particularly limited, but preferably, the ratio of the thickness of the layer (II) to the total thickness of the film of the present invention is 10% or more, more preferably 15. % Or more, and the upper limit is preferably 60% or less, more preferably 50% or less. When the thickness ratio of the layer (II) is within the above range, the film has excellent oxygen barrier properties and shrinkage properties, which is preferable.
The total thickness of the film of the present invention is not particularly limited, but it is preferably thin from the viewpoint of transparency, shrinkage characteristics, raw material cost, etc., and the upper limit is preferably 80 μm or less, more preferably 70 μm. Below, it is more preferably 50 μm or less. The lower limit is not particularly limited, but 20 μm or more is preferable in consideration of the handleability of the film.

<About contractility>
In the present invention, in order to obtain a film capable of achieving adhesion according to various shapes of the contents, it is necessary that the heat shrinkage rate of the film described later satisfies a specific range.

<Heat shrinkage rate>
It is important that the film of the present invention has a heat shrinkage rate of 30% or more in at least one direction when immersed in warm water at 80 ° C. for 10 seconds. The heat shrinkage rate is preferably 32% or more, more preferably 35% or more. The upper limit is not particularly limited, but is about 80%. When the heat shrinkage rate is within the above range, it is preferable that the adhesion to various shapes, particularly the contents having a large difference between the thick portion and the thin portion, can be improved. In order to keep the heat shrinkage of the film of the present invention within the above range, it can be adjusted by the stretching temperature and the stretching ratio.

Further, the shrinkage rate in the direction orthogonal to the direction in which the shrinkage rate is developed is not particularly limited. In order to improve the adhesiveness according to the shape of the object to be packaged, a high value may be preferable or a low value may be preferable, and it is necessary to appropriately select the material. Further, the heat shrinkage rate in the direction orthogonal to the direction in which the shrinkage rate is developed can be adjusted in the same manner as the heat shrinkage rate in the shrinkage direction.

<Shrink stress>
It is important that the film of the present invention has a maximum shrinkage stress of 8 MPa or more and 14 MPa or less when immersed in silicon oil at 80 ° C. for 1 minute. The lower limit of the shrinkage stress is preferably 8.5 MPa or more, more preferably 9.0 MPa or more, and the upper limit is preferably 13.5 MPa or less, more preferably 13.0 MPa or less. If the shrinkage stress is less than 8.5 MPa, the excess wrinkles that are about to occur at the initial stage of shrinkage on the coating cannot be eliminated during the shrinkage process, and the shrinkage finish appearance is not good. Deformation of the container occurs, which is not preferable.
In order to keep the shrinkage stress of the film of the present invention within the above range, the composition of each layer can be adjusted to the composition specified in the present invention, and the shrinkage stress can be adjusted by the draw ratio and the heat treatment temperature.

<All haze>
The heat-shrinkable film of the present invention preferably has a total haze value of 10% or less, more preferably 8% or less, and more preferably 7% or less when measured in accordance with JIS K7136. More preferred. When the total haze value is 10% or less, the visibility of the covering body to which the film is attached can be sufficiently obtained.

<Low temperature tensile elongation at break>
The film of the present invention has a tensile elongation at break in a direction orthogonal to the main shrinkage direction of the film, which is measured under the conditions of an atmospheric temperature of 0 ° C. and a tensile speed of 100 mm / min, preferably 100% or more and 800% or less. .. The lower limit is more preferably 150% or more, still more preferably 200% or more. When the tensile elongation at break in an environment of 0 ° C. is within the above range, problems such as film breakage during processes such as printing and bag making are unlikely to occur, which is preferable. Further, it is preferable that bag breakage or the like is less likely to occur from the portion in close contact with the covering.
In order to set the tensile elongation at break of the film of the present invention in the above range in the above range, adjustment of the composition of each layer, adjustment of extrusion conditions and extension conditions in the film forming process, adjustment of stretching conditions, adjustment of heat shrinkage, It can be adjusted by appropriately adjusting the stacking ratio.

<Oxygen permeability>
It is important that the film of the present invention has an oxygen permeability of 10 cc / m ² , day, atm or less at 23 ° C. and 0 ° C. RH. Oxygen permeability is preferably not more than ^{5cc / m 2 · day · atm} , more preferably not more than ^{2cc / m 2 · day · atm} . If the oxygen permeability is within the above range, the oxygen barrier property is sufficient.

<Manufacturing method>
The method for producing the film of the present invention is not particularly limited, and the film can be produced by a conventionally known method. The form of the film may be either flat or tubular, but from the viewpoint of productivity (several pieces can be taken as a product in the width direction of the raw film) and printing on the inner surface is possible, the film is flat. Is preferable. As a method for producing a flat film, for example, the resin is melted using a plurality of extruders, co-extruded from a T-die, cooled and solidified by a chilled roll, rolled in the vertical direction, and tentered in the horizontal direction. A method of obtaining a film by annealing, cooling, and winding with a winder can be exemplified. Further, a method of cutting open a film produced by the tubular method to make it flat can also be applied.
The extrusion temperature is preferably about 180 to 260 ° C, more preferably 190 to 250 ° C. Controlling the dispersed state of the material by optimizing the extrusion temperature and the state of shearing is also effective in setting various physical and mechanical properties of the film described below to desired values.

The draw ratio is preferably 2 to 10 times in the vertical direction, 2 to 10 times in the horizontal direction, more preferably 3 to 6 times in the vertical direction, and 3 to 6 times in the horizontal direction in applications for shrinking in two directions. Is. On the other hand, in applications where the contraction is mainly in one direction, the direction corresponding to the main contraction direction is preferably 2 to 10 times, more preferably 4 to 8 times, and the direction orthogonal to it is preferably 1 to 2 times, more. It is desirable to select a magnification ratio of 1.01 to 1.5 times, which is substantially in the category of uniaxial stretching. In addition, 1 times means the case which is not stretched.

In the present invention, the stretching temperature is preferably 70 ° C. or higher and lower than 90 ° C. The lower limit is more preferably 72.5 ° C. or higher, further preferably 75 ° C. or higher. The upper limit is more preferably less than 87.5 ° C, still more preferably less than 85 ° C.
The heat treatment temperature is preferably 70 ° C. or higher and lower than 90 ° C. The lower limit is more preferably 72.5 ° C. or higher, further preferably 75 ° C. or higher. The upper limit is more preferably less than 87.5 ° C, still more preferably less than 85 ° C.

<Other additives>
In addition to the above-mentioned components, each layer constituting the film of the present invention contains inorganic particles such as silica, talc and kaolin calcium carbonate, and pigments such as titanium oxide and carbon black, as long as the effects of the present invention are not impaired. , Flame retardants, weather resistance stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, cross-linking agents, lubricants, nucleating agents, antiaging agents and the like can be appropriately added.

<Other processing>
The film of the present invention can be subjected to surface treatment such as corona treatment, printing, coating, and vapor deposition, surface treatment, and bag making with various solvents and heat seals, if necessary.

<Packaging material of the present invention>
The film of the present invention can be suitably used as various packaging materials. As a specific example of use as a packaging material, for example, a bag is formed using the film of the present invention, and contents such as foods, pharmaceuticals, and industrial chemicals are stored in the bag, and the air inside is removed as needed. After sealing, it can be heat-treated and shrunk to form a package.

Hereinafter, the present invention will be described with reference to examples.
The measured values and evaluations shown in the examples were performed as follows. In the embodiment, the take-up (flow) direction of the laminated film is described as the "vertical" direction (or MD), and the direction perpendicular to the take-up (flow) direction is described as the "horizontal" direction (or TD).
<Measurement method>

(1) Oxygen Permeability The obtained film was measured at 23 ° C. and 0% RH using an OXY-TRAN100 type oxygen permeability measuring device manufactured by Modern Control Co., Ltd. to obtain an oxygen permeability.

(2) Heat Shrinkage Rate The obtained film was cut into a size of 10 mm in length and 200 mm in width, and immersed in a hot water bath at 80 ° C. for 10 seconds, respectively, and the amount of shrinkage was measured. For the heat shrinkage rate, the ratio of the amount of shrinkage to the original size before shrinkage was expressed as a% value in the lateral direction (TD).

(3) Shrinkage stress The film was cut out in the TD direction to a width of 10 mm and a length of 70 mm, and fixed at 50 mm so that the chuck load cell had no tarmi. Then, the sample piece was immersed in a silicon bath at 80 ± 0.5 ° C., and the maximum stress in 1 minute was measured. The contraction stress was calculated by applying the following formula.
Shrinkage stress (MPa) = stress applied to load cell (N) / cross-sectional area of sample piece (mm ² )

(4) Total haze value In order to evaluate the transparency of the obtained film, the total haze value was measured by JIS K7136.

(5) 0 ° C. Tensile elongation at break The obtained heat-shrinkable laminated film was cut into a size of 120 mm in the take-up direction (MD) and 15 mm in the perpendicular direction (TD), and in accordance with JIS K7127, the tensile speed was 100 mm / The tensile elongation at break in the film pick-up direction (MD) at an atmospheric temperature of 0 ° C. was measured in min, and the average value of the measured values of 10 times was measured.

The raw materials used in each of the examples and comparative examples are as follows.
<Polyester resin>
-Consists of 1,4-cyclohexanedimethanol: 21.8 mol%, ethylene glycol: 76.1 mol%, diethylene glycol: 2.0%, terephthalic acid: 90.5 mol%, isophthalic acid: 9.5 mol%. Polyester contained as an ingredient (abbreviated as copolymer A "PET1")
-Polyester containing 1,4-cyclohexanedimethanol: 23.5 mol%, ethylene glycol: 65.0 mol%, diethylene glycol: 11.5%, terephthalic acid: 100.0 mol% as constituents (copolymer A). Abbreviated as "PET2")
-Polyester containing 1,4-butanediol: 100 mol%, terephthalic acid: 90 mol%, isophthalic acid: 10 mol% as constituents (abbreviated as copolymer B "PBT").
<Ethylene-vinyl acetate copolymer saponified product>
-Product name: SP482B Ethylene content 32 mol%, MFR = 4.1 g / 10 minutes, density = 1.16 g / cm3 (abbreviated as "EVOH1")
-Manufactured by Nippon Synthetic Chemistry Co., Ltd. Product name: GC3304B Ethylene content 33 mol%, MFR = 4.0 g / 10 minutes, Density = 1.17 g / cm3 (abbreviated as "EVOH2")
<Other resins>
-Made by Ube-Maruzen Polyethylene Product name: Ube-Maruzen 0540F Linear low-density polyethylene polymerized using a metallocene catalyst, MFR = 4.0 g / 10 minutes, density = 0.904 g / cm3, melting point = 113 ° C. ("" (Abbreviated as PO1)
-Product name made by Japan Polypropylene Corporation Product name: propylene / ethylene random copolymer polymerized using Wintech WFX4T metallocene catalyst, ethylene content = 4%, MFR = 7.0 g / 10 minutes, density = 0.90 g / cm3 , Melting point = 125 ° C., Mw / Mn = 2.8 (abbreviated as "PO2")
-Product name manufactured by Dow Chemical Co., Ltd .: Versify DE2400.05, propylene-ethylene random copolymer propylene / ethylene = 88/12, density = 0.868 g / cm3 (abbreviated as "PO3")
-Manufactured by Polyplastics Product name: TOPAS9506F Ethylene-norbornene copolymer, MFR = 1.0 g / 10 minutes, density = 1.02 g / cm3, glass transition temperature Tg = 65 ° C (abbreviated as "COC")
<Adhesive resin>
-Modified polyolefin-based thermoplastic elastomer manufactured by Mitsui Chemicals, Inc. Product name: Admer SF725 (abbreviated as "AD1")
・ Mitsubishi Chemical's modified polyester-based thermoplastic elastomer Product name: Primaloy AP
GK320 (abbreviated as "AD2")

<Example 1>
In order to produce a 3 type 5 layer laminated film, each raw material is mixed according to the composition shown in Table 1, and then the (I) layer / In a facility capable of laminating and coextruding the (III) layer / (II) layer / (III) layer / (I) layer, the extruder set temperature of the (I) layer is 240 ° C., and the (II) and (III) layers are After melt-mixing at the extruder set temperature of 190 to 200 ° C., the thickness ratio of each layer is (I) layer / (III) layer / (II) layer / (III) layer / (I) layer = 14/3/6 / It was co-extruded to 3/14, taken up with a cast roll at 50 ° C., and cooled and solidified to obtain an unstretched laminated sheet. Next, this sheet was stretched at a stretching temperature of 80 ° C. at a stretching ratio of 5 times in the width direction using a film tenter, and then heat-treated at a heat treatment temperature of 80 ° C. to obtain a heat-shrinkable film having a thickness of about 40 μm. Obtained. This was evaluated. The results are shown in Table 1.

<Example 2>
After mixing each of the raw materials with the formulations shown in Table 1, a heat-shrinkable film having a thickness of about 40 μm was obtained by the same method as in Example 1 except that the adhesive resin was changed. This was evaluated. The results are shown in Table 1.

<Example 3>
After mixing each of the raw materials with the formulations shown in Table 1, a heat-shrinkable film having a thickness of about 40 μm was obtained by the same method as in Example 1 except that the resin used for the front and back layers was changed. This was evaluated. The results are shown in Table 1.

<Example 4>
After mixing each of the raw materials with the formulations shown in Table 1, a heat-shrinkable film having a thickness of about 40 μm was obtained by the same method as in Example 1 except that the resin used for the intermediate layer was changed. This was evaluated. The results are shown in Table 1.

<Comparative example 1>
After mixing the raw materials with the formulations shown in Table 1, the extruder set temperature of the (I) layer is 240 ° C., the extruder set temperature of the (II) and (III) layers is 190 to 200 ° C., and the thickness ratio of each layer is changed. , (I) layer / (III) layer / (II) layer / (III) layer / (I) layer = 6/3/22/3/6, except for the same method as in Example 1. A heat-shrinkable film having a thickness of about 40 μm was obtained. This was evaluated. The results are shown in Table 1.

<Comparative example 2>
After mixing each raw material with the formulation shown in Table 1, the extruder set temperature of each layer is 240 ° C., and the thickness ratio of each layer is (I) layer / (II) layer / (I) layer = 14/12/14. A heat-shrinkable film having a thickness of about 40 μm was obtained by the same method as in Example 1 except that the film was co-extruded so as to have a stretching ratio of 5.9 times in the width direction. This was evaluated. The results are shown in Table 1.

<Comparative example 3>
After mixing each raw material with the formulation shown in Table 1, the extruder set temperature of each layer is 240 ° C., and the thickness ratio of each layer is (I) layer / (II) layer / (I) layer = 14/12/14. A heat-shrinkable film having a thickness of about 40 μm was obtained by the same method as in Example 1 except that the film was co-extruded so as to have a stretching ratio of 5.1 times in the width direction. This was evaluated. The results are shown in Table 1.

<Comparative example 4>
After mixing the raw materials with the formulations shown in Table 1, the extruder set temperature of the (I) layer is 210 ° C, the extruder set temperature of the (II) and (III) layers is 190 to 200 ° C, and the thickness ratio of each layer is determined. , (I) layer / (III) layer / (II) layer / (III) layer / (I) layer = 14/3/6/3/14, except for the same method as in Example 1. A heat-shrinkable film having a thickness of about 40 μm was obtained. This was evaluated. The results are shown in Table 1.

The films of the present invention obtained in Examples 1 to 4 had good shrinkage, shrinkage finish, transparency, and fracture resistance, and had excellent oxygen barrier properties. On the other hand, all of Comparative Examples 1 to 4 were inferior in shrinkage and shrinkage finish / or oxygen barrier property.

As described above, the present invention has been described in relation to the most practical and preferable embodiments at present, but the present invention is not limited to the embodiments disclosed in the present specification. A heat-shrinkable laminated film accompanied by such a change, and a packaging material using the film, can be appropriately changed within the scope of the claims and the gist of the invention that can be read from the entire specification, or within a range not contrary to the idea. It must be understood as being included in the technical scope of the present invention.

Since the heat-shrinkable laminated film of the present invention is excellent in oxygen gas barrier property, shrinkage property, and transparency, the contents are altered by being used for packaging of foods, pharmaceuticals, industrial chemicals, etc., which dislike the alteration of the contents due to oxygen. It can be suitably used as a packaging material for shrink wrapping, shrinkage bundling wrapping, shrink wrapping label, etc. for these uses.

Claims (8)

A heat-shrinkable laminated film consisting of at least three layers having a layer (I) on the front and back layers and a layer (II) on the center layer, each layer containing the following resin as a main component, and oxygen at 23 ° C. and 0% RH. The heat shrinkage is characterized in that the transmittance is 10 cc / m ² , day, atm or less, and the heat shrinkage of the film in at least one direction when immersed in warm water at 80 ° C. for 10 seconds is 30% or more. Laminated film.
Layer (I): At least one polyester resin (II) Layer: At least one ethylene-vinyl acetate copolymer saponified product The heat-shrinkable laminated film according to claim 1, wherein the ethylene-vinyl acetate copolymer saponified product has an ethylene content of 20 to 45 mol%. The heat-shrinkable laminated film according to claim 1 or 2, wherein the ratio of the film thickness of the layer (II) is 10 to 60%. The heat shrinkage according to any one of claims 1 to 3 , further comprising a layer (III) containing an adhesive resin as a main component between the layer (I) and the layer (II). Laminated film. The heat-shrinkable laminated film according to any one of claims 1 to 4 , wherein the total haze value of the film conforming to JIS K7136 is 10% or less. Ambient temperature 0 ° C., according to any one of claims 1 to 5, the tensile breaking elongation in the direction orthogonal to the main shrinkage direction measured at a tensile rate of 100 mm / min under conditions is characterized in that 100% or more Heat shrinkable laminated film. The heat-shrinkable laminated film according to any one of claims 1 to 6 , wherein the shrinkage stress in the main shrinkage direction when immersed in a silicon bath at 80 ° C. is 8 MPa or more. A packaging material using the heat-shrinkable film according to any one of claims 1 to 7.