JPH04364948A - Heat-shrinkable multi layered barrier film - Google Patents

Abstract

PURPOSE:To obtain a gas barrier film with excellent drawing film-formability and heat-shrinkable properties by combining a polymer layer wherein an ethylene-vinyl alcohol copolymer is a main ingredient and a polymer layer wherein a thermoplastic polyester is a main ingredient and having a specified Vicat softening point. CONSTITUTION:A gas barrier film contains a polymer layer A wherein an ethylene-vinyl alcohol copolymer is a main ingredient, a polymer layer B wherein a thermoplastic polyester is a main ingredient and a polymer layer C which is constituted of a thermoplastic resin except polymers used in the polymer layers A and B. The Vicat softening point of the resin constituting the layer B is not lower than the glass transition point of the resin which is the main ingredient of the layer A and not higher than the Vicat softening point of the main ingredient resin. In addition, the Vicat softening point of the thermoplastic resin constituting the polymer layer C is not higher than 130 deg.C. Furthermore, this film has a heat shrinkage at 100 deg.C of not smaller than 20% at least in either longitudinal or transverse direction, pref. not smaller than 25% and more pref. not smaller than 30%.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has excellent gas barrier properties, and is mainly used in various packaging materials (mainly household wrap films, non-shrink packaging films that utilize barrier properties, shrink packaging films, and laminates). This article relates to a heat-shrinkable multilayer film useful as a gas barrier (mainly for O2, CO2 and other gases) using a polymer mainly composed of ethylene-vinyl alcohol copolymer. (hereinafter simply referred to as gas barrier) layer, and other layers include a specific polymer layer mainly composed of thermoplastic polyester and a specific thermoplastic resin layer. Regarding multilayer films.

0002

[Prior Art] Film packaging methods utilize the characteristics of each film, such as household wrap packaging,
Various packaging methods are used, such as burlap packaging, twist packaging, bagged packaging, skin packaging, shrink packaging, and stretch packaging. Among these, shrink wrapping has the characteristics of a beautiful appearance of the package, increasing the product value, keeping the contents hygienic, making it easy to visually check the quality, and fast and tightly fixing even odd-shaped items or multiple items. Films with excellent gas barrier properties are widely used in the food industry to prevent deterioration and spoilage of packaged items and extend their shelf life. It is mainly required for packaging of chemicals and electronic parts. In addition, in general, the items to be packaged are often sensitive to heat, and in the case of heat-shrinkable film,
It is also desired to have low-temperature shrinkability to the extent that dimensional changes do not occur during the distribution process, including storage, and at the same time to have practically sufficient heat sealability.

Conventionally, heat-shrinkable polymer films include:
Films mainly using polyvinyl chloride, polypropylene, polyethylene, etc. are known, but these films have poor gas barrier properties, and heat-shrinkable films using polyvinyl chloride require additives. Plasticizers and heat stabilizers are not sanitary, and disposal and incineration pose problems in terms of environmental protection and hygiene.

On the other hand, there are vinylidene chloride polymers and ethylene-vinyl alcohol copolymers as polymers with excellent gas barrier properties, but the former has good extrusion stability during film production. In order to provide good stretchability, large amounts of plasticizers and stabilizers are usually added, but these agents are not sanitary or cause problems such as odor and discoloration. Additionally, in multilayer films, these additives may migrate to adjacent layers, causing the barrier properties to become unstable over time. Furthermore, like the aforementioned polyvinyl chloride, there are problems in terms of environmental protection and hygiene when it comes to disposal and incineration. On the other hand, the latter ethylene-vinyl alcohol copolymer does not have the above-mentioned environmental health problems of the former, and its gas barrier properties during drying are generally better than the former, so it can be used in various packaging films. It is being considered.

However, ethylene-vinyl alcohol
In addition to being crystalline in itself,
Due to the presence of strong hydrogen bonds, the stretching process exhibits necking (extremely thick and thin areas at the same time), is unstable and easily breaks, and is difficult to make into thin films. The film formability was extremely poor, and in particular, there was a problem in that it was difficult to provide the necessary stretching orientation for a heat-shrinkable film. Furthermore, the obtained film also has poor shrinkability (particularly low-temperature shrinkability) as a shrink film, which poses a problem when high shrinkability is required for practical use.

[0006] Regarding this problem, Japanese Patent Laid-Open No. 62-26862
Publication No. 1 describes saponified ethylene-vinyl acetate copolymer,
A method of improving stretchability by adding a specific amount of water depending on the ethylene content has been disclosed, but this method may cause problems such as the generation of air bubbles during coextrusion molding and breakage of the film during stretch film formation. Adjustment of the moisture content to avoid this is complicated, and further inclusion of moisture inevitably leads to a decrease in gas barrier properties. In addition, it is difficult to uniformly control the amount of water used as a plasticizer over the entire surface before and during stretching, or to maintain a constant internal pressure in the case of tube-shaped stretching. It has the disadvantage that uniform stretching is difficult. Furthermore, once the moisture is removed, the shrinkability described above will be poor. In addition, JP-A No. 2-251418 discloses a method in which a saponified ethylene vinyl acetate copolymer is used as an inner surface layer and extruded into a tube shape by coextrusion molding, and cooling water is directly brought into contact with the saponified ethylene vinyl acetate copolymer. A method has been disclosed in which a relatively large amount of water (5 to 15% by weight) is impregnated by quenching to improve the stretchability, but since the saponified ethylene vinyl acetate copolymer layer is on the surface layer,
There is a risk of quality deterioration due to external influences, especially a decrease in gas barrier properties. In addition, the inclusion of a relatively large amount of water itself reduces gas barrier properties, but to compensate for this, heat treatment at a relatively high temperature (140 to 160°C) promotes crystallization and partially reduces the gas barrier properties. Since relaxation of molecular orientation occurs, a practical heat-shrinkable film cannot be obtained. Moreover, the shrinkability as a shrink film is also poor.

[0007] Furthermore, JP-A-53-138468 discloses a method in which a saponified ethylene-vinyl acetate copolymer and an inflatable thermoplastic resin (for example, polyethylene, nylon 6, ionomer, etc.) are coextruded. The laminated film is immediately and directly circumferentially compressed by gas pressure by 1.2 to 3.5
A method for obtaining a blown film by double blowing is disclosed. However, this method has difficulty in imparting a high degree of orientation, and in the general one-stage inflation method, intermolecular flow tends to occur during stretching film formation.
It is difficult to provide the molecular orientation necessary to develop practical heat shrinkability. Furthermore, after closely laminating a film made of a saponified ethylene vinyl acetate copolymer and another stretchable thermoplastic film (e.g., polyolefin resin, vinyl chloride resin, polyester resin, acrylonitrile copolymer, etc.), Method of biaxial stretching (JP-A-51-
6267), but the stretchability is insufficient and a highly shrinkable film has not been obtained. Also, unstretched or 1
A method has been proposed in which an axially stretched polyester film is composited with a saponified ethylene vinyl acetate copolymer film and then stretched (Japanese Unexamined Patent Publication No. 1986-86722). In order to obtain a highly stretched film, the optimal extrusion conditions, stretching conditions, etc. for each resin are different. The properties are not satisfactory, and as a result, it is difficult to obtain a practical heat-shrinkable film. In addition, as other methods, Japanese Patent Application Laid-open No. 62-103140 and No. 62-1
13526 and JP-A-1-97623 disclose techniques related to coextrusion and co-stretching of a multilayer stretched film having a composition of polyester/adhesive resin/ethylene-vinyl alcohol copolymer/adhesive resin/polyester. However, these specify the raw fabric forming conditions to obtain a stable flow of multilayers during coextrusion in order to improve stretchability and uneven thickness. This method is also insufficient, and it is difficult to obtain a practical heat-shrinkable film, especially a film with excellent low-temperature shrinkability.

In particular, among the above-mentioned films, the stretched film does not shrink sufficiently like the film of the present invention, or even if it does shrink, the shrinkage characteristics of each layer are unbalanced at high shrinkage, resulting in whitening (hereinafter referred to as "whitening") due to bending of the EVOH layer. , zigzag whitening). When this occurs, it causes serious drawbacks such as separation of layers, destruction of seals, extreme deterioration of transparency, and deterioration of barrier properties.

[0009]

[Problems to be solved by the present invention] As described above, there is no particular problem in terms of environmental hygiene such as disposal or incineration, and it has excellent stretch film formability and low temperature/high heat shrinkability, and zigzag whitening phenomenon occurs during practical shrink packaging. There is a strong demand for the development of a gas barrier film that is less likely to cause oxidation and has excellent mechanical properties, optical properties, and heat sealability.

0010

[Means for solving the problem] That is, at least one
The layer (A) is a polymer layer mainly composed of an ethylene-vinyl alcohol copolymer, and the other layers have a Vicat softening point of the resin constituting the layer (A). at least one thermoplastic polyester-based polymer layer (B) having a value equal to or higher than the glass transition point of the resin and equal to or lower than the Vicat softening point of the main resin; (A)
, contains a polymer layer (C) composed of a thermoplastic resin other than that mainly used in (B), and has a heat shrinkage rate of 2 at 100°C in at least one of the vertical and horizontal directions.
This is a heat-shrinkable multilayer film characterized by a heat shrinkage ratio of 0% or more.

[0011] The present invention will be explained in detail below. The polymer layer (A) of the present invention has a role as a main gas barrier layer, and has physical properties due to direct heat from the outside, physical and chemical actions, etc. In order to avoid deterioration and make the stretching and orientation effect described later more effective, preferably at least one
Arranged in layers. The main ethylene-vinyl alcohol copolymer constituting this layer (A) is an ethylene-vinyl acetate copolymer with an ethylene content of 15 to 80 mol%, so that the saponification degree is 80 mol% or more. A copolymer obtained by saponifying or derived from another copolymer to which --OH groups are added is used. In this case, if the ethylene content is less than 15 mol%, the melt moldability and stretch film forming properties will be poor, while if it exceeds 80 mol%, the gas barrier properties will be insufficient. In addition, it is preferable that the film has low-temperature shrinkability as much as possible, but this low-temperature shrinkability is influenced by the characteristics of the resin that makes up the multilayer, how the layer structure of the multilayer is combined, and the stretching temperature during film formation. be strongly influenced. Therefore, in order to impart low-temperature shrinkability, it is better to use a material with a low Vicat softening point, but in addition, considering gas barrier properties, it is better to Preferably, it is 95% or more. In addition, as other components, at least one miscible resin may be added to the extent that the barrier properties are not significantly impaired.
The inner layer (A) may be composed of a mixed resin mainly composed of this ethylene-vinyl alcohol copolymer by mixing within a range not exceeding 0 wt%. The amount is preferably 4
It is 0 wt% or less, more preferably 30 wt% or less, and even more preferably 20 wt% or less.

[0012] Examples of the resin to be mixed include, among the above, those with an ethylene content different from that of the ethylene vinyl alcohol copolymer mainly used, such as those with a high ethylene content; such as 55 to 80 mol%, or , ethylene-vinyl alcohol of groups with high ethylene content other than those mentioned above.
copolymers, partially saponified products thereof, modified products thereof, polyamide polymers, polyester copolymers, ethylene-vinyl ester copolymers, ethylene-aliphatic unsaturated fatty acid copolymers , ethylene-aliphatic unsaturated fatty acid ester copolymer, ethylene and aliphatic unsaturated fatty acid and the same ester, a free copolymer of three or more elements (alcohol in the same ester used for the above two and three elements) ionomer resins, styrene-conjugated diene block copolymers, and those obtained by hydrogenating at least a portion of the block copolymers, etc. In addition, these polymers may be modified, for example, by grafting a monomer having a carboxylic acid group as a polar functional group, or a copolymer containing ethylene and carbon monoxide, or a vinyl ester component in addition to these, Or, in addition to those obtained by converting at least a part of the same resin into hydroxyl groups, or those modified in the same manner as above, crystalline 1
, 2-polybutadiene, ethylene-based resins other than those mentioned above, propylene-based resins, polybutene-1-based resins, etc., and at least one type thereof shall be selected from these.

[0013] Also, the barrier property of the layer (A) is preferably 200cc [25.4μ/m2.
24hr・atm (25°C, 65%RH)] or less, more preferably 100cc[25
．． 4μ/m2・24hr・atm] or less. Next, as another layer of the polymer layer (A), the film of the present invention is a polymer layer (A) mainly composed of thermoplastic polyester.
B) contains at least one layer. The Vicat softening point of the resin constituting the layer (B) is higher than the glass transition point of the main resin constituting the layer (A) and lower than the Vicat softening point of the main resin. Only by meeting the requirements will the main objective of the present invention, particularly excellent stretch film formability and heat shrinkability, especially low temperature shrinkability, be achieved at the same time, and it can be used without zigzag whitening, as well as mechanical and optical properties. This led to the completion of a gas barrier film with excellent properties.

[0014] This is because the ethylene-vinyl alcohol copolymer which is the main component constituting the polymer layer (A) is essentially a crystalline resin, and its stretching is carried out to ensure the orientation and crystallization of the amorphous portion. From the viewpoint of gas barrier properties, crystallization in addition to molecular orientation is a favorable phenomenon, but excessive crystallization not only inhibits shrinkage but also significantly deteriorates transparency. . On the other hand, due to the synergistic effect of combining the polymer layer mainly composed of the specific thermoplastic polyester of the present invention, which has excellent mechanical properties and optical properties and has excellent stretchability, By significantly improving the properties, especially the low-temperature stretchability, many crystal nuclei due to molecular orientation are generated in the ethylene-vinyl alcohol copolymer due to the same stretching, and as a result, the heat shrinkability and transparency are adversely affected. Many microcrystals are generated, which improves gas barrier properties and increases the number of tie molecules, resulting in poor mechanical properties and
It is also believed that the shrinkage properties will be improved.

When the Vicat softening point of the resin constituting the polymer layer (B) mainly composed of thermoplastic polyester is lower than the glass transition point of the resin constituting the polymer layer (A), the stretched The film properties tend to deteriorate, and necking, film breakage, and uneven thickness tend to occur, and it becomes difficult to impart effective orientation to the (A) layer, and the resulting film is also difficult to machine. In addition to poor physical properties, problems such as insufficient heat shrinkage tend to occur. On the other hand, if the Vicat softening point of the resin constituting the layer (B) exceeds the Vicat softening point of the main resin constituting the layer (A), the stretching temperature will become too high and at the same time the stability of film formation will deteriorate. At the same time, the slippage between molecules in the layer (A) increases relatively, making it difficult to provide effective orientation. The obtained film also has poor low-temperature shrinkability due to the decrease in the shrinkage performance of both layers, and since the shrinkability of the (A) layer tends to be too insufficient, there is an imbalance with the heat shrinkability of the (B) layer. This accelerates the problem that zigzag whitening phenomenon tends to occur during heat shrinkage.

The Vicat softening point of the resin constituting layer (B) is preferably 40°C or higher and 120°C or lower, more preferably 60°C or higher and 110°C or lower. Vic here
The softening point at is determined according to ASTM D1525-76 (Rat
e B, load: 1 kg), and for the same resin, usually has a value that is approximately equal to or higher than the glass transition point.

[0017] Furthermore, the glass transition point referred to in the present invention is determined by DSC
It refers to the value measured by the method (heating speed: 10°C/min). The main thermoplastic polyester constituting the polymer layer (B) has heat sealability when the (B) layer is placed on the surface layer, and has heat sealability when it is placed adjacent to the layer (A). is preferably a copolymerized polyester, more preferably a copolymerized polyester with low crystallinity and a low crystal melting point, and still more preferably a substantially amorphous polyester, although it is not particularly limited in consideration of interlayer adhesion. It is a copolymerized polyester. In addition, components with higher barrier properties (for example, alcohol
There are copolymerized copolymers of aromatic monomers (mixed copolymerization, etc.) as a base oil component. Specifically, for example, alcohol
When alcohol is used as a copolymerization component, ethylene glycol is generally used, but other copolymerization components include propylene glycol, 1,4-butanediol, 1,5-pentanediol, At least one kind selected from 1,6-hexanediol, neopentyl glycol, polyethylene glycol, polytetramethylene glycol, cyclohexanedimethanol, xylylene glycol, or other known ones. Diols include ethylene glycol.
A combination of diol and one of these diols, or a combination of one of the above diols without ethylene glycol.
It may also contain one of the other diols as a base.

On the other hand, as the acid component for copolymerization, terephthalic acid is generally used, but other aromatic acids such as isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, or esters in their aromatic rings are also used. There are dicarboxylic acids and the like that have substituents that do not contribute to the reaction. Further, it may contain at least one dicarboxylic acid selected from succinic acid, adipic acid, sebacic acid, other aliphatic dicarboxylic acids, or other known dicarboxylic acids.

[0019] Either one of the above alcohol component and acid component may be used, or both may be used as appropriate. An example of a preferable combination is, for example, ethylene glycol as the main alcohol component and 1,4-
There are copolymerized products containing 40 mol% or less of cyclohexanedimethanol and using terephthalic acid as an acid component. In that case, a more preferable copolymerization ratio of 1,4-cyclohexanedimethanol is about 20 to 40 mol%, more preferably about 25 to 36 mol%. Preferably,
Among these, crystallinity (measured by wide-angle X-ray diffraction) as a raw material in a sufficiently annealed state is 30% or less, more preferably 10% or less, and even more preferably substantially amorphous. It is. Further, the blend of other resins is the same as in the case of the (A) layer (both the amount and the type, except that the main resin of the (A) layer is also added).

[0020] The most important feature of the film of the present invention is (A
) layer and layer (B) do not peel off in practice, which is advantageous for stretchability and practicality as a film. Furthermore,
The film of the present invention includes a polymer layer (C) composed of a thermoplastic resin other than those mainly used in (A) and (B) above and having a Vicat softening point of 130° C. or lower. The (C) layer serves as a reinforcing layer for mechanical strength such as tear strength, whether it is an inner layer or an outer layer, and in addition to the above when placed on the surface layer, it is mainly used as a heat seal layer or as an additive. It serves as a surface layer for bleeding antifogging agents, antistatic agents, slip agents, etc. by internal addition, and is preferably arranged so that at least one of the surface layers is the layer (C).

[0021] The Vicat softening point of the thermoplastic resin constituting this polymer layer (C) is 130°C or less. Vic
If the at softening point is 130° C. or higher, the above-mentioned stretching film-forming properties are adversely affected, the stretching temperature becomes high and the film-forming stability deteriorates, and the resulting film tends to have poor low-temperature shrinkability. Also, when placed on the surface as a heat seal layer,
If the sealing conditions become high temperature conditions, adhesion to the sealer and resulting seal failures may occur easily.
If it is necessary to provide cooling time to maintain the integrity of the sealed portion, the time required for heat sealing becomes longer, which also causes problems in terms of packaging efficiency. Preferred Vic
The at softening point is 120°C or lower, more preferably 110°C or lower. Similarly, the degree of crystallinity of the thermoplastic resin constituting the layer (C) is 65% or less for additive mixability.
It is preferable in terms of bleedability and heat shrinkage characteristics.

The thermoplastic resin constituting this polymer layer (C) includes polypropylene polymer, ethylene polymer, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene - Aliphatic unsaturated carboxylic acid ester copolymer, free tertiary or more copolymer selected from ethylene, aliphatic unsaturated fatty acid and the same ester (C3 or more in the same ester used for the above two or three elements) (Also includes those with a low softening point.) Soft polymers made of α-olefin copolymers, ionic crosslinkable copolymers, block copolymers of vinyl aromatic hydrocarbons and conjugated diene derivatives, and derivatives thereof. Examples include crystalline 1,2 polybutadiene, polybutene-1, etc., and at least one of these is used, but other polymers may be mixed as long as the properties are not impaired. The amount is less than 50% by weight, preferably less than 30% by weight.

A preferred example of the polypropylene polymer is propylene and other α-olefins (C2, C4 to
C8). Ethylene-based polymers include ordinary low-density polyethylene, linear low-density polyethylene, and very low-density (VL, UL) polyethylene, which are composed of ethylene, propylene, 1-butene, 1-butene, etc. Pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, etc. with 3 to 1 carbon atoms
Contains a copolymer with at least one type of monomer selected from α-olefins of 8. The ethylene-vinyl acetate copolymer has a vinyl acetate group content of 5 to 26% by weight and a melt index (190°C, 2.16 kg) of 0.2 to 1.
0 is preferred.

Next, as the ethylene-aliphatic unsaturated carboxylic acid copolymer and the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene - Acrylic acid ester (selected from C1 to C8 alcohol components such as methyl, ethyl, propyl, butyl) copolymer, ethylene-methacrylate ester (selected from C1 to C8 alcohol components such as methyl, ethyl, propyl, butyl, etc.) (selected) copolymers, etc. These may be multicomponent copolymers in which the components to be copolymerized are at least two or more selected from the above or other components. Examples of the soft polymer made of an α-olefin copolymer include one or more α-olefins selected from ethylene and/or propylene and α-olefins having 4 to 12 carbon atoms, or a soft combination thereof. These copolymers generally have a crystallinity of 30% or less as measured by an X-ray method, and are different from the above-mentioned ethylene copolymers. Preferably, as the α-olefin, ethylene and propylene, or ethylene and propylene contain 1
-butene, 1-pentene, 4-methyl-1-pentene,
Binary or ternary or more copolymers selected from 1-hexene, 1-octene, etc., and others, and even those obtained by polymerizing a small amount of non-conjugated diene derivatives as other third components. good.

Next, the ionically crosslinkable copolymer refers to at least a part of an ethylene-methacrylic ester copolymer, an ethylene-acrylic ester copolymer, or other suitable copolymer, or at least one of the above-mentioned ester derivatives. An ionomer resin in which at least a part of the partially saponified one is ionically bonded, or at least a part of the copolymer with the above carboxylic acid is ionically bonded, or the carboxylic acid moiety of the above multi-component copolymer. At least a portion of it is made into an ionomer.

[0026]The block copolymer of vinyl aromatic hydrocarbon and conjugated diene derivative and its derivative are as follows:
A block copolymer consisting of a block mainly composed of a vinyl aromatic hydrocarbon represented by styrene and a block mainly composed of a conjugated diene such as butadiene and isoprene,
Alternatively, these copolymers may be acid-modified, or at least a portion of the double bonds may be hydrogenated.

[0027] Also, as crystalline 1,2 polybutadiene,
Polybutene-1 polymers preferably have a 1,2 bond content of 85% or more and a crystallinity of 10 to 40% as determined by the IR method (Morello method), and as polybutene-1 polymers, crystals with a butene-1 content of 93 mol% or more are preferable. Others (carbon number C2, C3, C5
It is a high molecular weight product that also includes a copolymer with a C8 (alkene type) monomer, and unlike liquid and waxy low molecular weight products, it has a low melt index (190℃
2.16 kg) is preferably 0.2 to 10. (
The thermoplastic resin constituting the layer C) is preferably selected from at least one type of the above-mentioned resins, or an appropriate blend composition.

Furthermore, the film of the present invention has a heat shrinkage rate at 100° C. of 20% or more, preferably 25% or more, more preferably 30% or more in at least one direction, vertically and horizontally. If the heat shrinkage rate is less than 20%, the fit after shrinkage will be insufficient, causing wrinkles and sagging after packaging. In addition, the film must be stable enough to prevent dimensional changes as much as possible during the distribution process, including storage, and the temperature at which film shrinkage occurs is 45°C.
As mentioned above, it is desirable that the temperature is preferably 55°C or higher. However, the shrinkage onset temperature of the film refers to the temperature at which the thermal shrinkage rate becomes 5%.

Polymer layers (A), (B) and (
C) may contain a plasticizer, an antioxidant, a surfactant, a colorant, an ultraviolet absorber, a lubricant, an inorganic filler, etc., as long as the original properties of each component are not impaired. Group (1) is added to one or both surfaces to provide antifogging properties, antistatic properties, adhesion, slipperiness, etc.
As group (2), surface modification such as corona treatment or plasma treatment, or coating treatment with surfactants, antifogging agents, antistatic agents, etc. as group (2), or those added to resin and allowed to bleed, may also be used. As for 3), known adhesives and adhesives may be treated in the same manner. For example, group (2
) include polyhydric alcohol partial fatty acid esters such as sorbitan fatty acid ester, glycerin fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyethylene glycol fatty acid ester,
Ethylene oxide adducts such as polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, alkylamines, alkylamides,
Amines such as alkylethanolamines and alkylethanolamides, amides, polyalkylene glycols,
In addition to granidine derivatives, phosphate-containing anion activators, sulfonate derivatives, quaternary ammonium salts, pyridinium salts, imidazoline derivatives, polyvinyl alcohol, acrylic acid-based hydrophilic polymers, polymers having a pyrrolidium ring in the main chain, and Group (3) includes silica sol, alumina sol, etc., and group (3) includes mineral oil,
There are liquid polybutene, oils and fats not included in the former, and viscous liquids (500 centipoise or more), etc., and these are used alone or in combination as appropriate. Further, each of the above-mentioned treatments or additives of each group may be freely combined.

The film of the present invention comprises a polymer layer (A), (
It is composed of at least three layers consisting of at least one layer each of B) and (C), but the arrangement of the layers is as follows: (i) In the case of three layers, A/B/C, B/A/C, A/ C/B (ii) In case of 4 layers B/A/B/C, C/A/C/B, C/A/B/C, B
/C/A/B, A/C/B/C, A/B/C/B, A/
B/A/C, A/C/A/B (iii) In case of 5 layers, B/A/C/A/B, B/A/B/C/B, B/C/A
/C/B, C/B/A/B/C, C/A/B/A/C,
C/B/C/A/C, B/A/C/A/C, B/A/B
/A/C, B/C/A/B/C, B/C/B/A/C,
A/B/C/B/C, A/B/A/B/C, A/C/A
/B/C, A/C/B/A/C, A/C/B/C/B,
A/B/C/A/B, A/B/A/C/B, A/C/A
/C/B (iv) For 7 layers C/A/B/A/B/A/C, C/B/C/A/C/B
/C, C/A/C/B/C/A/C, C/B/A/B/
A/B/C, C/B/A/C/A/B/C, C/A/B
/C/B/A/C, C/B/A/C/B/A/C, B/
A/C/B/C/A/B, B/C/A/B/A/C/B
, B/A/B/C/B/A/B, B/C/B/A/B/
C/B, B/C/A/C/A/C/B, B/A/C/A
/C/A/B, B/A/B/A/B/C/B, C/A/
B/A/B/C/B, C/B/A/B/A/C/B, C
/B/A/C/B/A/B, C/A/B/A/B/A/
B, C/B/A/B/A/B/A, C/A/C/B/A
/B/A, C/B/C/A/C/B/A, C/B/A/
Examples include C/A/B/A, etc., but are not limited thereto. In addition, cases of 6 layers, 8 layers, etc. are also included. Further, a preferred layer arrangement is such that at least one of the (A) layers is located as an internal layer, at least one of the (B) layers is adjacent thereto, and at least one of the surface layers is the (C) layer.

When there are two or more layers (A), (B), or (C), the resins constituting these layers may be the same or different. In addition, the (B) layer is a multilayer of polymers mainly composed of different thermoplastic polyesters, for example (B1)/(B2).
) etc., and the same applies to the (A) layer. Further, if necessary depending on the usage conditions, an adhesive layer made of another known adhesive resin may be provided in order to improve the adhesive strength between each layer. The resin used for such an adhesive layer is an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, or a copolymer of ethylene and the above. A multicomponent copolymer consisting of at least two types of free combinations of each monomer, or other partially saponified ethylene-vinyl acetate copolymers, ethylene-carbon monoxide-vinyl acetate copolymers, thermoplastics Polyurethane, known acid-modified polyolefins, etc. are used.

The heat-shrinkable multilayer film of the present invention has a total thickness of 5 to 100 microns, more preferably 7 to 80 microns. If the thickness is less than 5 microns, the film tends to lack stiffness and tear easily, causing problems with workability during packaging, and the possible thickness of the inner layer (A) as the main gas barrier layer becomes thinner, making it impractical for practical use. cause a hindrance. On the other hand, if the thickness exceeds 100 microns, the stiffness of the film becomes too strong, leading to problems such as poor fitting and sealing properties. In addition, the responsiveness of shrinkage may deteriorate, or the overall shrinkage force may become too strong, resulting in poor finish. In a preferred embodiment, the inner layer (A) has a total thickness of 0.5 to 20 microns, preferably 1.0 to 15 microns. If the thickness is less than 0.5 microns, the probability of pinhole formation due to foreign substances such as gel may increase, and the quality of gas barrier properties may deteriorate due to the influence of thickness unevenness. Moreover, if the thickness is 20 microns or more, the cost will increase due to the use of expensive resin, or the performance will be excessive. Moreover, problems may arise in stretchability.

[0033] The total thickness of the layer (B) is appropriately selected depending on the various configurations of the heat-shrinkable multilayer film of the present invention.
Generally 1-60μ, preferably 2-40μ, more preferably 3-30μ. If it is less than 1 μm, the stretching improvement effect is poor or it is difficult to obtain practical shrinkage characteristics. 60 again
If μ is exceeded, troubles may easily occur due to the lower back and contractile force becoming too strong.

Furthermore, the ratio of the total thickness of the (B) layer to the total thickness of the (A) layer is 0.3 to 20, preferably 0.5 to 20.
20, more preferably 0.7 to 20, even more preferably 1
．． 0 to 20, the lower limit is limited from the viewpoint of stretching improvement properties (stability, expandability of the stretching condition range), and the upper limit is limited to avoid saturation of the stretching improvement effect and shrinkage performance expression effect and excessive performance. .

The total thickness of the layer (C) is suitably used in the range of 5 to 90% of the total thickness of the film, depending on the characteristics of the resin used, and is 2 to 50 microns, preferably 3 to 4 microns.
It is 0 micron. (However, if the aforementioned adhesive layer is used, its thickness shall be included in the total thickness of the (C) layer.) Also, if the (C) layer is used as a surface layer, one surface layer is formed by the (C) layer. The thickness of the layer is at least 1 micron, preferably at least 1.5 micron. (C) The lower limit of the total thickness of the layer is necessary to ensure the effect of developing mechanical strength such as tear strength and the sealing property, and the upper limit is necessary to ensure the effect of developing mechanical strength such as tear strength and sealing property. Limited to avoid performance.

Next, an example of the method for manufacturing the multilayer film of the present invention will be described, but the method is not limited thereto. First, each layer of the multilayer film of the present invention ((A), (B)
, (C) layer and, if necessary, an adhesive layer) are melted in respective extruders, coextruded through a multilayer die, and rapidly cooled to maintain at least the (B) layer in a substantially amorphous state. The multilayer film is then cooled and solidified to obtain a multilayer film.

At the time of coextrusion, at least (B) is rapidly cooled.
Maintaining the layer in a substantially amorphous state is intended to facilitate subsequent film formation by stretching, and is important for providing effective molecular orientation and achieving uniform thickness. When the layer (B) is composed of a mixed resin, at least the thermoplastic polyester that is the main component is kept in an amorphous state. Further, the extrusion method is not particularly limited, and a multilayer T-die method, a multilayer circular method, etc. can be used, and the latter is preferable.

The multilayer film material obtained in this manner is heated to a temperature that is 20° C. lower than the Vicat softening point of the resin forming the (B) layer, and the main resin forming the (A) layer is heated. Stretching is carried out at a stretching temperature below the melting point. Here, the stretching temperature refers to the average value of the surface temperature of the film in the machine direction from the start of stretching to the end of stretching (the average value of the surface temperature of the film at the stretching start point, the stretching end point, and the midpoint between the stretching start point and the stretching end point). Average value of surface temperature).

If the stretching temperature exceeds the melting point of the main resin constituting the layer (A), breakage will easily occur and it will be difficult to impart effective orientation, and the resulting film will also have poor mechanical properties. and heat shrinkability is also impaired. On the other hand, if the stretching temperature is less than 20°C lower than the Vicat softening point of the resin constituting the layer (B), the stretching stress will become too high and may easily cause breakage, uneven thickness, or whitening. Become. The preferred stretching temperature is at least 15°C lower than the Vicat softening point of the resin constituting the layer (B);
(A) The range is below the Vicat softening point of the main resin constituting the layer.

Further, the stretching is carried out in at least one direction at an area stretching ratio of 5 to 50 times, preferably 8 to 36 times, and is appropriately selected depending on the heat shrinkage rate required depending on the application. Stretching methods include roll stretching method, tenter method, bubble method, etc.
Although there are no particular limitations, a method of forming a film by simultaneous biaxial stretching is preferred. Further, if necessary, post-treatments such as heat setting, lamination with other layer films, etc. may be performed, and furthermore, modification treatment may be freely performed with energy rays such as electron beams and ultraviolet rays before and after stretching. It's okay.

The film of the present invention is mainly used as a packaging material,
Although it is particularly suitable for shrink wrapping, it can also be used as a wrapping film for household and commercial use, taking advantage of its excellent gas barrier properties. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

[0042] Measurement and evaluation methods in the present invention and Examples will be described below. (1) Crystallinity The raw material resin was sufficiently annealed to reach an equilibrium state and was determined by wide-angle X-ray diffraction. The X-ray device is Rotaflex RV-200B (graphite) manufactured by Rigaku Denki Co., Ltd.
using a monochromator), acceleration voltage: 50 KV,
Bulb current: 160mA (target: Cu), 2θ: 5
It was performed at ~36°. In addition, it is simple to use wide-angle
The density method (JIS
K7112-D method) or DSC method (JIS
K7122 compliant) to obtain a calibration curve, and an unknown sample may be determined by the density method or DSC method. (2) After sufficiently heating and melting the Vicat softening point raw material resin, it is rapidly cooled to make it into an amorphous state at least if the raw material resin is thermoplastic polyester, and a sample with a thickness of 3 ± 0.2 mm is prepared.
Measured using D1525-76 (Bate: B, load 1 kg). (3) Glass transition point Using a sample (approximately 10 mg) obtained in the same manner as in (2) above, it was measured by the DSC method at a heating rate of 10° C./min under a nitrogen stream. (4) Using melting point DSC, the temperature was raised to 290°C under the conditions of (3) above, then cooled to below room temperature at a cooling rate of 20°C/min, and then heated again at 10°C/min for measurement. The main endothermic peak temperature at that time was taken as the melting point. (5) Film surface temperature Using a contact type surface thermometer using an iron-constantan type thermocouple, bring the tip of the thermocouple into contact with the film surface.
The indicated value after seconds was taken as the film surface temperature. (6) Film Formation Stability The continuous stability of the film (continuous stability of stretching bubbles) and thickness unevenness of the finished film were evaluated when heating and stretching was performed in a predetermined method.

[0043] Symbol
Scale ◎: The stretching pattern of the film (stretched bubble) hardly changes, and the continuous stability is good. ○: Film thickness unevenness is within ±15%. △: The stretching start position is slightly unstable. Thickness unevenness exceeding ±15% and within ±25%. ×: Film runs out and bubble punctures occur frequently.

Alternatively, even if stretching is possible, the stretching start position varies greatly and the thickness unevenness exceeds ±25%. (7) Heat shrinkage rate A 100mm square film sample was placed in an air oven thermostat set at 100°C and allowed to shrink freely for 10 minutes.The amount of film shrinkage was determined and divided by the original dimensions. Expressed as a percentage of the value. In the case of uniaxial stretching, the stretching direction,
In the case of biaxial stretching, which is a preferred embodiment, it is taken as an average in the longitudinal and transverse directions. (8) HAZE Measured according to ASTM-D-1003-52. (9) Tensile modulus It was performed according to ASTM-D-882-67, and the stress at 2% elongation was expressed as a value converted to 100%. (10) O2 TR (oxygen permeability) unit: cc/m2
・24hr・atm Measured by the method of ASTM D3985. (11) Tear strength Measured according to ASTM-D-1922. (12) Heat-sealing strength Film pieces were layered so that the heat-sealing layers of the stretched film faced each other and sealed with an impulse sealer to form a 15 mm wide test piece, and its peel strength was measured using a tensile tester. (13) Zigzag whitening A 100 mm square film sample was allowed to shrink freely in a heated silicone oil bath, and at least one of the vertical and horizontal sides was heat-shrinked by 40% or more, and the adhered oil was wiped off and visually inspected. The presence or absence of whitening and, if so, the degree of whitening, and cross-sectional observation using an optical microscope were evaluated. (If the maximum thermal shrinkage rate was less than 40%, the evaluation was performed using a sample under the maximum thermal shrinkage conditions.) ◎: (A) Bending and whitening of the layer were hardly stopped.

○: Slight bending of layer (A) is observed, but
There is almost no whitening or only a slight amount of whitening is observed, and there is no problem in practical use. Δ: Bending of the layer (A) is clearly observed, and some whitening occurs, which may pose a practical problem. ×: The (A) layer was severely bent and the transparency was significantly reduced due to whitening.

[0046] The resins used in Examples and Comparative Examples are described below. a1; Ethylene-vinyl alcohol copolymer (ethylene content: 44 mol%, saponification degree: 99% or more, MFR (
210°C, 2160g): 3.5, glass transition point: 55
°C, Vicat softening point: 150 °C, melting point: 165 °C)a
2; Same as above (ethylene content: 38 mol%, degree of saponification: 9
9% or more, MFR (210°C, 2160g): 3.2,
Glass transition point: 58°C, Vicat softening point: 154°C,
Melting point: 176°C) a3: Same as above (ethylene content: 29 mol%, degree of saponification:
99% or more, MFR (210°C, 2160g): 3.2
, glass transition point: 62°C, Vicst softening point: 175°C
, melting point: 190°C) a4; Same as above (ethylene content: 49 mol%, degree of saponification:
99% or more, MFR (210°C, 2160g): 5.4
, glass transition point: 48°C, Vicst softening point: 138°C
, melting point: 153°C) b1; Copolymerized polyester mainly composed of terephthalic acid as the acid component, and diol component consisting of 30 mol% of 1,4-cyclohexanedimethanol and 70 mol% of ethylene glycol (Vicat softening point: 82°C, Crystallinity: 0
% (amorphous)) b2; Copolymerized polyester (Vicat softening point: 75°C, (Crystallinity: 20%, melting point 230°C) b3; Acid component: 85 mol% terephthalic acid, 10 mol% isophthalic acid, 5 mol% adipic acid, diol component: 98 mol% ethylene glycol, 2 mol% diethylene glycol. Polymerized polyester (Vicat softening point: 67°C, crystallinity: 10%, melting point 180°C) b4
A copolymerized polyester consisting of 80 mol% of terephthalic acid and 20 mol% of isophthalic acid as acid components, and 97 mol% of tetramethylene glycol and 3 mol% of ethylene glycol as diol components (Vicat softening point: 40°C, crystallinity: 15%) , melting point 193°C) b5; conventional film-forming polyethylene terephthalate (Vicat softening point: 71°C, crystallinity: 45%,
(melting point: 263°C) b6; Copolymerized polyester consisting of 85 mol% of terephthalic acid and 15 mol% of isophthalic acid as acid components, and ethylene glycol as diol component (Vicat softening point: 70
℃, crystallinity: 17%, melting point 220℃) c1; ethylene-vinyl acetate copolymer (VAc 10% by weight, Vica
t Softening point: 74℃, MFR (190℃, 2160g
); 3) c2; Same as above (VAc 15% by weight, Vicat softening point:
67℃, MFR (190℃, 2160g); 2) c3
;Low density polyethylene (density: 0.92g/cm3,
Melting point: 106°C, Vicat softening point: 92°C, MFR (
190°C, 2160g); 2) c4; linear low density polyethylene (comonomer: 1-
Hexene, density: 0.912g/cm3, melting point: 11
7℃, Vicat softening point: 87℃, MFR (190℃,
2160g); 2.0) c5; Ultra-low density polyethylene (comonomer: 1-butene, density: 0.900g/cm3, melting point: 115°C,
Vicat softening point: 67℃, MFR (190℃, 216
0g); 2.0) c6; Polypropylene (density: 0.90g/cm3
, melting point: 162°C, Vicat softening point: 153°C, MF
R (230°C, 2160g); 3.3) d1; Maleic anhydride-modified ethylene-vinyl acetate copolymer (vinyl acetate content: 28% by weight, Vicat softening point: 52°C, MFR (190°C, 2160g); 3 )

0
047]

[Example 1] Ethylene-vinyl alcohol copolymer; a
1 (Ethylene content: 44 mol%, degree of saponification: 99% or more, MFR (210°C, 2160g): 3.5, glass transition point: 55°C, Vicat softening point: 150°C, melting point:
(165°C) is layer (A), a copolymerized polyester mainly composed of terephthalic acid as an acid component and a diol component consisting of 30 mol% of 1,4-cyclohexanedimethanol and 70 mol% of ethylene glycol; b1 (Vicat softening point: 82°C, crystallinity: 0% (amorphous)) (B) layer, linear low density polyethylene; C4 (comonomer: 1-hexene, density: 0.912 g/cm3, melting point: 117
°C, Vicat softening point: 87 °C, MFR (190 °C, 2
160g); 2.0) containing 2.0% by weight of an additive containing oleic acid monoglyceride and diglycerin monolaurate in a weight ratio of 1:1, and a layer (C) containing ethylene-acetic acid as an adhesive layer. Vinyl copolymer; C2 (VAc1
5% by weight, Vicat softening point: 67°C, MFR (190
℃, 2160g); 2) was used, and the layer arrangement was (C)/(adhesive layer)/(B)/(A)/(B)/(adhesive layer)/(C).
After extruding using an annular multilayer die to form 7 layers,
The material was rapidly cooled and solidified using a refrigerant to produce a tube-shaped original fabric with a folded width of 200 mm and a thickness of 320 μm, each layer having uniform thickness accuracy. The thickness of each layer is 64μ/32 from the outside of the tube.
μ/48μ/32μ/48μ/32μ/64μ. Next, this raw fabric is passed between two pairs of differential nip rolls, heated to 115°C in a heating zone, and stretched at a stretching ratio of 4.0 times in length and 4.0 times in width in a stretching zone (under a multistage hood) under the same atmosphere.
The film was simultaneously biaxially stretched to 0x, and then cooled with air at 20°C in a cooling zone to perform bubble stretching. The stretching temperature at this time was 10
The temperature was 3°C. The edges (both ends) of the obtained film were slit, and two films were wound up into a roll using a winder.

The obtained film was 4μ/2μ/3μ/2μ/3μ/2μ/4μ in the same order as the original film described above, and had a total thickness of 20μ. (Run-1) Next, using the same original fabric, stretching was performed in the same manner as above, changing the stretching temperature and stretching ratio, but in all cases, there was almost no breakage due to punctures, and the film formation stability was good. Met. (Run-2
34) Table 1 shows the layer structure, stretching conditions, and physical property evaluation results of the obtained film. The films of Run-1 to Run-4 were all evaluated as excellent with respect to the zigzag whitening phenomenon.

As described above, the film of the present invention has extremely good film forming stability during stretching, has practically sufficient heat sealing properties, is resistant to zigzag whitening during heat shrinkage, and has excellent gas barrier properties and optical properties. , low-temperature shrinkage, mechanical properties, etc. Also, using cellophane tape, (
An attempt was made to separate the A) layer and the (B) layer, but it was extremely difficult.

Note that Run ratios -1 and 2 are Run-ratios -1 and -2.
Stretching was carried out using a tube-shaped original fabric having the same layer structure as in 1 at a stretching temperature of 165°C and 76°C, respectively, but punctures occurred frequently in both cases, making it difficult to form films stably. Ta.

[0051]

[Table 1]

[0052]

Example 2 A film having the layer structure shown in Table 2 was obtained in the same manner as in Example 1. (In addition, each (C) forming the surface layer
Each layer contains an additive treated in the same manner as in Example 1 in an amount of 1 to 3% by weight based on each surface layer. ) The stretching conditions and physical property evaluation results are shown in Table 2. Stretching film formability was good, and the obtained film was also good in terms of zigzag whitening (R
All ○~◎) except un ratio -3), gas barrier property,
It had excellent low-temperature shrinkability.

Note that Run ratio-3 has the same thickness composition ratio as Run-5, and the surface layer resin is polypropylene; C6 (
Density: 0.90g/cm3, Melting point: 162°C, Vic
at Softening point: 153℃, MFR (230℃, 2160g
); Using the original fabric produced by changing 3.3), we tried stretching film formation by changing the stretching temperature from 80°C to 170°C, but in both cases there were many punctures, and we could barely stretch the film. A film was obtained in spots under the conditions of magnification of 3x vertically and 2.5x horizontally, but the thickness unevenness was large (±25%), and although some attempts were made to heat seal, the sealing conditions were quite high and within the range of conditions. Also, the shrinkability of the surrounding area including the sealing area was poor, making it unsuitable for use as a shrinkable barrier film having heat-sealing properties, which is the object of the present invention.

Note that c24 in Table 2 is a blend of the following resins. c24; (c2: 40% by weight + c4: 60% by weight)

[0055]

[Table 2]

[0056]

Example 3 A film having the layer structure shown in Table 3 was obtained in the same manner as in Example 1 using a three-type, five-layer die. (Each surface layer contained 1 to 3% by weight of additives treated in the same manner as in Example 1.) Film forming stability was good, and zigzag whitening hardly occurred in any case. (◎) Stretching conditions and physical property evaluation results are also shown in Table 3. (In addition, c24 in Table 3 is the same blend as that used in Run-7 of Example 2.)

[0057]

[Table 3]

[0058]

Example 4 A film having the layer structure shown in Table 4 was obtained in the same manner as in Examples 1 and 3. (The surface layer of each film was treated in the same manner as in Example 3 and contained the same additives.) The stretching conditions and physical property evaluation results are shown in Tables 4 and 5. All evaluations of zigzag whitening were good, ranging from ◎ to ◎, and all were excellent in low-temperature shrinkability and the like. The following symbols in Tables 4 and 5 represent blends.

a11; (a1: 90% by weight + b1: 10% by weight)
a12; (a1: 80% by weight + b1: 20% by weight)
a13; (a1: 80% by weight + SEBc: 20% by weight
) SEBc; (Styrene-butadiene block copolymer hydrogenated butadiene block acid modified (maleic anhydride 2 wt%). Styrene content approximately 40 wt%, MFR (230°C, 2.16 Kg) 1.
0) a14; (a1: 80% by weight + EVOH Note): 20% by weight) Note EVOH; (saponified ethylene vinyl acetate copolymer. Ethylene content approximately 89 mol%, degree of saponification 99% or more, MF
R (090°C, 2.16Kg) 5) a15; (a1: 80% by weight + EVC: 20% by weight)
EVC; (ethylene-vinyl acetate-carbon monoxide copolymer. MFR (190°C, 216Kg) 3.5, melting point 66°C
) a16; (a1: 85% by weight + Ny6: 15% by weight)
Ny6; (relative viscosity 2.8 measured in 6.98% nylon sulfuric acid solution (25°C)) a17; (a1: 85% by weight + Ny6/66: 15% by weight) Ny6/66; (copolymerized nylon 6/ 66. Nylon 6
6 content; 15% by weight, relative viscosity measured in 95% sulfuric acid solution (25°C) 3.0) a18; (a1: 85% by weight + IR: 15% by weight) I
R: (30% neutralization of partial saponification degree (saponification degree 40%) of ethylene-methyl methacrylate ester copolymer (methyl methacrylate content 20% by weight) with Mg ions. MFR (190 °C, 2.16Kg)1.5)a
19; (a1: 70% by weight + IR: 15% by weight + Ny
6/66: 15% by weight) IR and Ny6/66 are the same as above (used in Run Nos. 20 and 21).

b11; (b1:90% by weight+a1:
10% by weight) (Vicat softening point; 87°C) c24; (c2: 40% by weight + c4: 60% by weight)

[0061]

[Table 4]

[0062]

[Table 5]

[0063]

[Comparative Example 1] Ethylene-vinyl alcohol copolymer; a
1 (Ethylene content: 44 mol%, degree of saponification: 99% or more, MFR (210°C, 2160g): 3.5, glass transition point: 55°C, Vicat softening point: 150°C, melting point;
165°C) as the (A) layer, and terephthalic acid 80 as the acid component.
copolymerized polyester consisting of mol%, isophthalic acid 20 mol%, diol component 97 mol% tetramethylene glycol, 3 mol% ethylene glycol; b4 (Vic
at Softening point: 40°C, crystallinity: 15%, melting point: 193
C) layer (B), linear low density polyethylene; c4 (
Comonomer: 1-hexene, density: 0.912g/cm
3. Melting point: 117°C, Vicat softening point: 87°C, M
FR (190°C, 2160g); 2.0) containing 2.0% by weight of an additive containing oleic acid monoglyceride and diglycerin monolaurate in a weight ratio of 1:1 (C)
layer, and further as an adhesive layer, an ethylene-vinyl acetate copolymer; c2 (VAc 15% by weight, Vicat softening point: 67
℃, MFR (190℃, 2160g); 2), the layer arrangement was (C)/(adhesive layer)/(
A seven-layer tube-shaped original fabric of B)/(A)/(B)/(adhesive layer)/(C) was produced. The thickness of each layer was the same as in Example 1, and the film was formed by stretching under the same conditions. However, the stretching start position varied and punctures occurred frequently, so the stretching ratio was reduced to 3.2 times in the vertical direction and 3.2 times in the horizontal direction. Although a film was barely obtained at 2.4 times, the film thickness was uneven (±28%), the heat shrinkage rate was about 17%, and uneven wrinkles and undulations were observed.

[0064]

[Comparative Example 2] Ethylene-vinyl alcohol copolymer; a
2 (Ethylene content: 38 mol%, degree of saponification: 99% or more, MFR (210°C, 2160g): 3.2, glass transition point: 58°C, Vicat softening point: 154°C, melting point;
(A) layer, conventional film-forming polyethylene terephthalate; b5 (Vicat softening point: 71°C
, crystallinity: 45%, melting point: 263°C) as the (B) layer, maleic anhydride modified ethylene-vinyl acetate copolymer: d1 (vinyl acetate content: 28% by weight, Vica
t Softening point: 52°C, MFR (190°C, 2160g);
3), the layer arrangement is (B)/(adhesive layer)/(A)/(
Adhesive layer) / (B) were melted and composited in a die to form 5 layers, and a sheet-like original fabric with a thickness of 234 μm and each layer having uniform thickness accuracy was produced using a cooling roll controlled at 60 ° C. . The thickness of each layer is 64μ/32μ/4 in the order of the layer arrangement above.
They were 2μ/32μ/64μ. Next, this original fabric was sequentially biaxially stretched 3 times in the vertical direction and 3 times in the horizontal direction at 85° C. under condition (2). In addition, as condition ①, first, at 95℃,
Biaxial stretching was carried out successively by 3 times, then 3 times horizontally at 130°C, but under condition ①, the stretching in the vertical direction was relatively smooth, but the film teared frequently during stretching in the horizontal direction. By slowing down the speed, a film barely having the predetermined stretching ratio was obtained. However, local whitening was observed in the obtained film, and its heat shrinkage rate was as low as about 11%. This is because crystallization progresses due to the long thermal history from heating the original fabric to stretching, which is necessary for stretching film formation.
This seems to be due to a decrease in heat shrinkability.

On the other hand, under condition (2), compared to condition (2), vertical,
Although the stretching was relatively smooth in both the horizontal and vertical directions, the heat shrinkage rate of the resulting film was as low as 8%, and even though both films were heat-treated at at least 150°C or higher, the heat shrinkage rate was less than 2%. Therefore, it was unsuitable as a heat-shrinkable film. As described above, it has been difficult to obtain a film with excellent heat shrinkability, which is the object of the present invention, using the known prior art.

[0066]

[Example 5] The layer structure obtained in Example 1 was (linear low density polyethylene; c4)/(ethylene-vinyl acetate copolymer; c2)/(copolyester; b1)/(ethylene-vinyl alcohol Copolymer; a1 )/(b1
) / ( c2 ) / ( c4 ) irradiated. ASTM D276
The gel fractions of each surface layer measured in accordance with No. 5 were all equivalent to about 6%. Using this original fabric, stretching film formation was performed in the same manner, and the stretching temperature was 101°C and the stretching ratio was vertical,
A film with a thickness of 20 μm was obtained under conditions of 4.0 times the width. The film formation stability was good, the heat shrinkage rate of the obtained film was 55%, and the O2 TR was 22cc/m2・24hr・
Atm, the heat sealing strength was 0.83 kg/15 mm, and the film had excellent heat shrinkability and heat sealing properties, and had no zigzag whitening (◎). (Run-33)

[
0067

[Example 6] Linear low density polyethylene; c4 contains oleic acid monoglyceride, diglycerin laurate and mineral oil in a weight ratio of hydrogenated petroleum resin (hydrogenated cyclopentadiene resin) of 1:1:1:0.5. Additives 3.
The same resin as in Example 1 was used for the other layers, and the layer structure was (c4)/(c2)/(b1) using the same resin as in Example 1. )/(
A 7-layer tubular original fabric with a thickness of 160 μm was obtained using a1)/(b1)/(c2)/(c4). The thickness of each layer is 24μ/16μ/32μ/16μ from the inside of the tube.
/32μ/16μ/24μ. This original fabric was subjected to electron beam irradiation treatment (8 Mrad) using an electron beam irradiation device (manufactured by Nissin High Voltage Co., Ltd.) with an accelerating voltage of 500 kV. The gel fraction of each surface layer measured according to ASTM D2765 was 9.0% for the inner surface layer of the tube and 8.5% for the outer surface layer, which were almost the same. Using this original fabric, a film was formed by stretching in the same manner at a stretching temperature of 112°C and a stretching ratio of 4.0 times in both length and width.
A film of 0μ was stably obtained. (Run-34) The heat shrinkage rate of the obtained film was 27%, and almost no zigzag whitening was observed. (Evaluation: ◎) Also, when this film was evaluated for its suitability as a wrap film, it was found that the film of the present invention has firmness, good cuttability, and less clinging between films, making workability easier. . In addition, the self-adhesiveness was good, and even when heated in a microwave oven, there was no peeling of the film, no holes caused by melting, and no whitening phenomenon, and the suitability for microwave ovens was also good.

[0068] The method for evaluating wrap suitability will be described below. ■ Cutting performance: When cutting a 300mm wide film with a serrated cutter (box for Saran Wrap R manufactured by Asahi Kasei Industries, Ltd.), there is no tearing in the opposite direction from the middle of the cut, and the film runs smoothly along the serrations without any waste. Those that could be cut to a certain extent were considered good. (2) Adhesion: A china teacup (diameter approximately 60 mm) was wrapped in a 200 mm x 200 mm film, and the adhesion was visually evaluated after 24 hours. ■ Microwave suitability: Wrap approximately 40g of pork belly in a film and heat it in a microwave oven with a rated high frequency output of 600W.
The film was processed for 1 minute and changes in the film were visually determined.

[0069]

[Example 7] In the same manner as in Example 1 and Example 3,
A film having the layer structure shown in Table 6 was obtained. Table 6 shows the stretching conditions and physical property evaluation results. Run No. The crystallinity of each thermoplastic polyester layer after stretching film formation in Nos. 37 and 38 was 7% and 11%, respectively. (Measurement was carried out by immersing the obtained film in methanol at room temperature or below for 10 hours or more, then peeling off the thermoplastic polyester layer, air drying, measuring the density using a density gradient tube, and using wide-angle X-ray diffraction in advance. (It was determined from a calibration curve prepared by similarly measuring samples whose crystallinity was fixed by the density method.) The evaluation of zigzag whitening of these films was ◎ to ◎.

[0070] Both sides of these films were coated almost uniformly over the entire surface with a coating amount of about 150 mg/m2 of diglycerin monooleate, and the suitability as a wrap film was evaluated in the same manner as in Example 6. It had good cuttability, self-adhesiveness, etc., and was also satisfactory in microwave oven suitability.

[0071]

[Table 6]

[0072]

[Example 8] Ethylene-vinyl acetate copolymer; C1 containing 1.5% by weight of an additive containing oleic acid monoglyceride and diglycerin monolaurate in a weight ratio of 1:1 was used as the (C) layer. A three-layer tubular original fabric having a layer structure of (copolyester; b1)/(ethylene-vinyl alcohol copolymer; a4)/(c1) and a thickness of 126 μm was obtained in the same manner as in Example 1. The thickness of each layer is b
1 layer was 36μ, A4 layer was 18μ, and C1 layer was 72μ. Hereinafter, in the same manner as in Example 1, the stretching temperature was 98°C.
Stretch film formation was carried out under the conditions that the stretching ratio was 3 times both in the length and width to obtain a uniform film with a thickness of 14 μm. The heat shrinkage rate of the obtained film was 39%, and the O2 TR was 49cc/m2.2
4hr・atm, the heat sealing strength using the C1 layer as the heat sealing layer is 0.61 kg/15 mm, which has sufficient heat sealing properties for practical use, and zigzag whitening is not a practical problem (rating: ○). The film had excellent shrinkability. (Run-39)

[0073]

[Example 9] Ethylene-vinyl alcohol copolymer; a
1 as (a) layer, copolymerized polyester; b1 as (B) layer
layer and ethylene-vinyl acetate copolymer; c1 (C
) layer to obtain a four-layer tube-shaped original fabric in the same manner as in Example 1, and then heated and stretched in the same manner to obtain a film having the layer structure shown in Table 7. In all cases, the film formation stability was good. The stretching conditions and physical property evaluation results are also shown in Table 6. Furthermore, although some zigzag whitening was observed in Run-41 (evaluation: △ to ◯), the films of Run-40 and 42 were good (evaluation: ◯), and were films with excellent shrinkage properties.

[0074] The ethylene-vinyl acetate copolymer c1 used in Run-40 and Run-41 contained the same additive (1.5% by weight) as used in Example 8.
In Run-42, when producing a tube-shaped original fabric, a mixture of mineral oil and diglycerin monooleate (50:50 by weight) was sealed inside the tube and squeezed with nip rolls to perform inner coating treatment.

[0075]

[Table 7]

[0076]

[Comparative Example 3] Among the polymer layers used in Run-8 of Example 2, (B) is composed of copolymerized polyester; b1
A 5-layer tubular original fabric was obtained in the same manner as in Example 1 except for the layer structure. The thickness composition ratio is (c4:74μ)/
(c2:37μ)/(a2:49μ)/(c2:
37μ)/(c4:74μ) and the original film thickness is Run-8
It was 271μ, which is almost the same as that of 271μ. Attempts were made to form a film by stretching using the same method with various stretching conditions ranging from approximately 70°C to 170°C, but the bubbles were unstable and punctured frequently, making it extremely difficult to form a film by stretching. Met.

Next, using the same tube-shaped original fabric, it was irradiated with an electron beam of 12 Mrad using an electron beam irradiation device with an accelerating voltage of 750 kV (manufactured by Nissin High Voltage Co., Ltd.), and then the same method was used again. Attempting stretching film formation, stretching temperature 1
A film with a thickness of 22 μm was almost stably obtained at 34° C. and at a stretching ratio of 3.5 times in both length and width. However, the heat shrinkage rate of this film at 100° C. was as low as 19%, which caused problems such as poor low-temperature shrinkability, a clear zigzag phenomenon, and deterioration of transparency (rating: ×).

[0078]

Effects of the Invention As described above, the heat-shrinkable multilayer barrier film of the present invention has a polymer layer mainly composed of an ethylene-vinyl alcohol copolymer, which has sufficient adaptability in terms of environmental hygiene, as the main gas barrier layer. In relation to the ethylene-vinyl alcohol copolymer that is the main component of the polymer layer, by combining a polymer layer that is mainly composed of thermoplastic polyester and has a specific Vicat softening point, excellent stretching properties can be achieved. It simultaneously achieves film properties and heat shrinkability, especially low-temperature shrinkability, and also exhibits an extremely effective accompanying effect in practice, such as preventing the zigzag whitening phenomenon of the gas barrier layer during heat shrinkage, which was a conventional problem. Furthermore, by disposing a specific thermoplastic resin layer that does not inhibit stretchability, it has excellent gas barrier properties, heat sealability, mechanical properties, and optical properties, making it extremely useful mainly for various packaging materials. .

Claims (3)

[Claims] Claim 1: At least one polymer layer (A) mainly composed of an ethylene-vinyl alcohol copolymer, and the other layers have a Vicat softening point of the resin constituting the layer (A). At least one thermoplastic polyester-based polymer layer (B) having a value higher than the glass transition point of the main resin constituting the layer and lower than the Vicat softening point of the main resin, and a Vicat softening point A polymer layer composed of a thermoplastic resin other than those mainly used in (A) and (B) above with a temperature of 130°C or less (
A heat-shrinkable multilayer film comprising C) and having a heat shrinkage rate at 100° C. of 20% or more in at least one of the vertical and horizontal directions. 2. The thermoplastic resin constituting the polymer layer (C) is a polypropylene polymer, an ethylene polymer, an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-vinyl acetate copolymer, or an ethylene-vinyl acetate copolymer. Aliphatic unsaturated carboxylic acid ester copolymers, soft polymers consisting of α-olefin copolymers, ionic crosslinkable copolymers, block copolymers of vinyl aromatic hydrocarbons and conjugated diene derivatives and their derivatives, crystals 1,2 polybutadiene, polybutene-1
The heat-shrinkable multilayer film according to claim 1, which is at least one kind of polymer selected from the group of polymers. 3. At least one polymer layer (A) is located in the inner layer, at least one polymer layer (B) is adjacent thereto, and at least one of the surface layers is located in the inner layer, and at least one of the polymer layers (C
) The heat-shrinkable multilayer film according to claim 1 or 2.