JP3288809B2 - Heat shrinkable multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent gas barrier properties and is mainly used for various packaging materials (mainly household adhesive wrap films, non-shrink wrapping films utilizing barrier properties, shrink wrapping films) , Laminating films and other uses are not limited). More specifically, a gas barrier mainly comprising a surface layer made of a thermoplastic resin and a polymer containing as a component a copolymer containing hydroxymethylene units obtained by reducing polyketone [mainly barrier properties of O ₂ , CO _{2 and} other (inorganic and organic) gases. : Hereinafter, it is simply referred to as gas barrier. The present invention relates to a heat-shrinkable multilayer film having a polymer layer mainly composed of a thermoplastic polyester different from the main component of the above-mentioned surface layer as another layer. The shrink wrapping film will be described in detail. As the next object, a film suitable for close contact wrap will be described as a typical example, but is not limited thereto.

[0002]

2. Description of the Related Art Film wrapping methods, which take advantage of the characteristics of each film, include, for example, home-use wrap packaging,
Various packaging methods such as overlap packaging, twist packaging, bag packaging, skin packaging, shrink packaging, and stretch packaging are employed. Among them, shrink wrapping is characterized by its beautiful appearance, enhanced product value, sanitary contents and easy visual quality confirmation, and quick and tight fixation of irregular or multiple products. It is widely used for packaging foods and sundries because it can be packaged.However, on the other hand, films that have excellent gas barrier properties to suppress deterioration Mainly, it is required for packaging of chemicals and also electronic parts. In general, the packaged material often does not generate heat, and in the case of a heat-shrinkable film, it has a low-temperature shrinkage property that does not cause a dimensional change in the distribution process including storage, and at the same time, has sufficient heat sealability for practical use. It is also desired to have.

Conventionally, as a heat-shrinkable polymer film,
Films mainly using polyvinyl chloride, polypropylene, polyethylene, etc. are known, but these films are inferior in gas barrier properties, and in heat-shrinkable films using polyvinyl chloride, they are used in combination. Plasticizers and heat stabilizers are not preferred in terms of hygiene, and disposal and incineration are problematic in terms of environmental conservation and hygiene.

On the other hand, polymers having excellent gas barrier properties include vinylidene chloride-based polymers and ethylene-vinyl alcohol-based copolymers (hereinafter abbreviated as EVOH). For sex,
Further, it is usual to add a large amount of a plasticizer or a stabilizer in order to give good stretchability, and these are not preferable in terms of hygiene and have problems of odor and discoloration. In addition, in some cases, in a multilayer film, these additives may be transferred to an adjacent layer, and the barrier properties may become unstable with time. Further, similarly to the above-mentioned polyvinyl chloride, disposal and incineration have problems in terms of environmental protection and hygiene. on the other hand,
The latter EVOH does not have the above-mentioned environmental hygiene problems of the former, and also has a better gas barrier property at the time of drying than the former, and therefore its use in various packaging films is being studied.

[0005] The EVOH referred to here is JP-B-47-3.
No. 8558, U.S. Pat. No. 3,510,464, etc. are copolymers obtained by hydrolyzing or saponifying a copolymer mainly composed of ethylene and vinyl acetate. And a copolymer containing hydroxymethylene units obtained by reducing the polyketone of the present invention. In addition to being crystalline, this EVOH exhibits necking-like stretching (including simultaneously extremely thick and thin portions) during stretching due to the presence of strong hydrogen bonds, and has poor stability and breaks. For example, it is difficult to form a thin film, and the stretch film-forming property is extremely poor. In particular, there is a problem that it is difficult to impart a stretch orientation necessary for a heat-shrinkable film.
Also, the obtained film has poor shrinkage (particularly low-temperature shrinkage) as a shrink film, and there is a problem when high shrinkage is required for practical use. In addition, there is a problem in thermal stability, and gel is easily generated when melt extrusion is performed continuously, which adversely affects subsequent processing (for example, occurrence of breakage during stretching and film formation of a film) and lowers commercial properties. There are problems such as invitation.

To solve this problem, Japanese Patent Laid-Open Publication No.
No. 1 discloses a method of improving the stretchability by adding a specific amount of water to EVOH in accordance with the ethylene content thereof. However, generation of air bubbles during coextrusion molding and stretching during film formation are disclosed. It is complicated to adjust the water content in order to avoid troubles such as breaking of the film, and the decrease in gas barrier properties is unavoidable by further containing water. In addition, before stretching, it is difficult to uniformly control the amount of water serving as a plasticizer throughout the entire surface during stretching, or in the case of tubular stretching, it is difficult to keep the internal pressure constant. There are drawbacks that are difficult to do. Further, if the moisture is removed, the above-mentioned shrinkability is inferior. In addition, JP-A-2-
Japanese Patent No. 251418 discloses that a relatively large amount (5 to 5%) is obtained by extruding EVOH as an inner surface layer into a tube by coextrusion molding, and bringing EVOH into direct contact with cooling water and quenching.
(15% by weight) to improve the stretchability is disclosed. However, since EVOH is present in the surface layer, there is a risk that quality deterioration due to external influences, particularly a decrease in gas barrier properties, may occur. In addition, the inclusion of a relatively large amount of water itself lowers the gas barrier properties. However, in order to cover this, heat treatment is performed at a relatively high temperature (140 to 160 ° C.). Since the orientation is relaxed, a practical heat-shrinkable film cannot be obtained. Further, the shrinkage as a shrink film is also poor.

Japanese Patent Application Laid-Open No. Sho 53-138468 discloses that a laminated film obtained by co-extruding EVOH and an inflation-capable thermoplastic resin (eg, polyethylene, nylon 6, ionomer, etc.) is immediately subjected to gas pressure.
A method is disclosed in which a blown film is obtained by directly blowing 1.2 to 3.5 times in the circumferential direction. However, in this method, it is difficult to give a high degree of orientation, and in the ordinary one-stage inflation method, intermolecular flow is likely to occur during stretch film formation, which is necessary for realizing practical heat shrinkability. It is difficult to provide a proper molecular orientation. Furthermore,
A method in which an EVOH film and another stretchable thermoplastic film (for example, a polyolefin-based resin, a vinyl chloride resin, a polyester resin, an acrylonitrile copolymer, etc.) are closely laminated and then biaxially stretched (Japanese Patent Laid-Open No. 5
However, stretchability is insufficient, and a highly shrinkable film has not been obtained. In addition, a method in which an unstretched or uniaxially stretched polyester film is combined with an EVOH film and then stretched (Japanese Patent Laid-Open No.
No. 86722) has been proposed. However, in order to obtain a highly stretched film for each of the layers constituting the multilayer, the optimum extrusion conditions and stretching conditions for each resin are different. It is not always possible to satisfy the stretched film-forming property due to uneven thickness, puncture, delamination, whitening, etc. during film formation, and as a result, it is difficult to obtain a practical heat-shrinkable film. Another method is disclosed in
103140, 62-113526 and JP-A-1-97623 disclose polyester /
Techniques relating to co-extrusion co-stretching of a multilayer stretched film having a constitution of adhesive resin / EVOH / adhesive resin / polyester have been disclosed. However, in order to make stretchability and thickness unevenness favorable, co-extrusion techniques are disclosed. The raw material molding conditions for obtaining a stable flow of the multilayer at the time are specified, which are insufficient as in the methods described above, and are also excellent in practical heat-shrinkable films, especially in low-temperature shrinkability. It is difficult to obtain a film.

In particular, among the above-mentioned films, the stretched film has poor heat shrinkability (mainly shrinkage), or the shrinkage characteristics of each layer are unbalanced at high shrinkage even when shrinking.
There were defects such as whitening (hereinafter referred to as zigzag whitening) due to bending of the VOH layer. When this occurs, serious drawbacks such as separation of layers, breakage of seals, extreme deterioration of transparency, and deterioration of barrier properties are caused. As a film having improved stretch film forming properties and heat shrinkage properties, and further having excellent heat sealing properties and mechanical properties, the present inventors have disclosed in JP-A-4-364.
948 discloses a multilayer film of a polymer layer mainly composed of EVOH, a specific polymer layer mainly composed of thermoplastic polyester, and a polymer layer composed of a specific thermoplastic resin. Outflow of gel during continuous long-term film formation and its adverse effect on the drawing stability and appearance,
There is still insufficient pinhole resistance, etc.
There are problems such as a drop in merchantability.

[0009]

As described above, there is no problem in terms of environmental hygiene such as disposal and incineration, and it has excellent melt processability and stretch film forming property. It is an object of the present invention to provide a novel gas barrier film that is less likely to cause zigzag whitening during packaging and has excellent mechanical properties, optical properties, and heat sealability.

[0010]

That is, the present invention provides a thermoplastic resin layer (A) forming a surface layer and at least one of the internal layers composed of at least two layers having a hydroxymethylene unit. A gas barrier polymer layer (B) containing a polymer as at least one component, and another layer is a polymer layer (C) mainly composed of a thermoplastic polyester different from the main component of the layer (A). A multilayer film comprising at least four layers, wherein the hydroxymethylene unit is obtained by reducing at least a part of a carbonyl group of a polyketone, and the polyketone is formed of carbon monoxide and at least one kind of a polyketone. Carbon number 2
A copolymer of the above-mentioned α-olefin, or carbon monoxide, at least one kind of the α-olefin, and further, as the following components, vinyl acetate, an aliphatic unsaturated carboxylic acid,
A copolymer with at least one monomer selected from aliphatic unsaturated carboxylic acid esters, or a modified copolymer thereof, wherein the multilayer film has a heat shrinkage of at least 20%, And a heat shrinkage stress of at least 5
A heat-shrinkable multilayer film characterized by being 0 g / mm ² .

In a preferred embodiment of the present invention, the thermoplastic resin constituting the layer (A) is a polypropylene polymer, a poly (4-methylpentene) polymer, a polybutene polymer, or a crystalline 1,2. Polybutadiene, polyethylene polymer, ethylene-α-olefin copolymer, soft polymer composed of α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic Unsaturated carboxylic acid ester copolymers, block copolymers of vinyl aromatic hydrocarbons and conjugated diene derivatives and derivatives thereof, or copolymers of two or more selected freely from the above copolymer monomers At least one selected from polymers or modified polymers of these polymers, and furthermore, hydroxy contained in the polymer layer (B). The ratio of the copolymer having a methylene unit is 10 to 100% by weight, and the content of the hydroxymethylene unit obtained by reducing the ketone of the copolymer contained in the polymer layer (B) is 10 to 10. ~ 50 mol%
The heat-shrinkable multilayer film according to the above, wherein the copolymer having hydroxymethylene units contained in the polymer layer (B) has a hydrogenation conversion of at least 50%.

Hereinafter, the present invention will be described in detail. First, the thermoplastic resin layer (A) forming the surface layer of the present invention is for effectively utilizing the excellent gas barrier properties of the present invention. In addition to ensuring the airtightness of the package by close contact, etc., it also develops practically sufficient sealing strength, and also as a reinforcing layer in terms of mechanical strength such as tear strength, and protection of the gas barrier resin layer As layers
In addition, it also plays a role as a surface layer for bleeding an antifogging agent, an antistatic agent, a lubricant, etc. as an additive by an internal addition method, and optionally, an adhesive layer between each layer, and also a mechanical strength. It is also used as an intermediate layer as a reinforcing layer on the surface, an additive holding layer, and the like. If the practical Vicat softening point of the thermoplastic resin constituting the layer (A) is too high,
High stretching temperature, especially when used for shrink wrapping, impairs low-temperature shrinkage, or when used as a heat-sealing layer, heat-sealing conditions become high-temperature, causing local shrinkage around the seal. As a result, the occurrence of defects increases, resulting in poor sealing or poor finishing. The preferred Vicat softening point of the thermoplastic resin is 130 ° C. or lower, more preferably 120 ° C., and still more preferably 110 ° C.
° C. When the thermoplastic resin layer (A) is composed of a mixed resin, the Vicat softening point of each resin does not need to satisfy the above condition, and the Vicat softening point of the entire (A) layer can satisfy the above condition. Good. However, when it is used for applications other than shrink wrapping, preferable conditions for the above-mentioned Vicat softening point are not limited to these.

The thermoplastic resin constituting the layer (A) includes a polypropylene polymer, a poly (4-methylpentene) polymer, a polybutene polymer, a crystalline 1,2-polybutadiene, a polyethylene polymer, and an ethylene-α-olefin. Copolymer, a soft polymer comprising an α-olefin copolymer,
Ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, block copolymer of vinyl aromatic hydrocarbon and conjugated diene derivative and the same Derivatives, copolymers of two or more freely selected from the monomers of the above copolymers, or modified polymers of these polymers, and at least one selected from these. Although it is used, another polymer may be mixed as long as its properties are not impaired. Its amount is less than 50% by weight, preferably not more than 30% by weight. Preferred examples of the polypropylene-based polymer include known homopolypropylene and a copolymer of propylene with another α-olefin (C ₂ , C _{4 to} C ₈ ). The poly (4-methylpentene) polymer is a copolymer of poly (4-methylpentene) 1, 4-methylpentene 1 and a small amount of another monomer such as another α-olefin (C _{2 to} C ₁₂ ). Usually, for example, a density of 0.83
Near 5 g / cm ³ , the visible light transmittance is 85% or more and the transparency is excellent, and the Tg is about 50 ° C. or less. The polybutene-based polymer refers to a copolymer of a crystalline monomer having a butene-1 content of at least 80 mol% and an olefinic monomer having another carbon number (C ₂ , C ₃ , C _{5 to} C ₈ ). Is different from liquid and waxy low-molecular-weight ones, and has a melt index (190 ° C., 2.16 kg)
However, as the crystalline 1,2 polybutadiene, the crystalline 1,2 polybutadiene is preferably 1,2 by the IR method (Morello method).
Those having a bonding amount of 85% or more and a crystallinity of 10 to 40% are preferred.

Examples of the polyethylene polymer include ordinary high-pressure low-density polyethylene and high-density polyethylene.
Examples of the ethylene-α olefin copolymer include linear low-density polyethylene, ultra-low-density (VL, UL) polyethylene, and the like. These are ethylene and propylene, 1-butene, and 1-pentene. , 4-methyl-1
It is a copolymer with at least one kind of monomer selected from α-olefins having 3 to 18 carbon atoms, such as pentene, 1-hexene and 1-octene. Usually its density is 0.8
It is in the range of 70 to 0.940 g / cm ₃ . or,
As a soft polymer composed of an α-olefin copolymer, for example, ethylene and or propylene and carbon number of 4 to
A soft copolymer comprising one or more α-olefins selected from 12 α-olefins or a free combination, the crystallinity of which by X-ray method is generally 30% or less; This is different from the resin group described above.

The above-mentioned polyolefins have a density of 0.830 to 0.940 g / c in addition to the polymer obtained by the conventional method.
m ³ , which is more uniform than the conventional one in terms of molecular weight and molecular weight dispersion polymerized with a metallocene catalyst represented by a single site catalyst (for example, Mw / M
n is 1.5 to 3.0). Also,
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) 0.2 to 10 are preferred.

The ethylene-aliphatic unsaturated carboxylic acid copolymer and the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer. , ethylene - acrylic acid ester (methyl, ethyl, propyl, selected from alcohol component C ₁ -C ₈ of butyl) copolymer, ethylene - methacrylic acid ester (methyl, ethyl, propyl, C ₁ ~ of butyl selected from alcohol component C ₈₎ copolymer, and the like. A block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene derivative and a derivative thereof are 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. And copolymers obtained by acid-modifying these copolymers, and those obtained by hydrogenating at least a part of the double bonds. These may be at least two or more multi-component copolymers in which the components to be copolymerized are selected from the above or other components.

Further, modified polymers of these polymers may be used.
Representative examples thereof include ion-crosslinkable copolymers, which are ethylene-methacrylic acid ester copolymers, ethylene-acrylic acid ester copolymers, or at least a portion of other suitable copolymers, or At least a portion of at least a portion of the ester derivative of the saponified, ionomer resin ion-bonded, or at least a portion of the copolymer with the carboxylic acid is ion-bonded, or the above multi-component At least a part of the carboxylic acid portion of the copolymer is ionized. The thermoplastic resin constituting the layer (A) is preferably selected from at least one of the above resins or a blended composition as appropriate.

Next, the polymer layer (B) of the present invention comprises O ₂ ,
It has a role as a main gas barrier layer for CO ₂ , N ₂ , and other organic gases, etc., and avoids physical property deterioration such as direct moisture, solvent, external force, heat, etc. from outside. In order to further enhance the stretching orientation effect exerted in combination with the polymer layer (C), at least one layer is disposed inside. The (B) layer contains a copolymer having a hydroxymethylene unit obtained by reducing at least a part of a carbonyl group (mainly having a carbon-carbon bond in a main chain) of the polyketone. A copolymer of carbon monoxide and at least one α-olefin having 2 or more carbon atoms, or carbon monoxide, at least one α-olefin and, in addition, vinyl acetate and aliphatic It is a copolymer with a saturated carboxylic acid and at least one monomer selected from aliphatic unsaturated carboxylic acid esters. The copolymer having a hydroxymethylene unit includes those obtained by additionally undergoing a saponification reaction, or those obtained by modifying (chemical reaction such as ionomerization or grafting).

The copolymer having a hydroxymethylene unit of the present invention is essentially different from the above-described EVOH in the production method and molecular structure, and is used in combination with the (A) layer and the polymer layer (C). In the above method, troubles caused by the generation and outflow of gel are improved, and melt processability is improved, whereby the stretchability and long-term stability of the film are further improved.

The polyketone referred to in the present invention is a copolymer of carbon monoxide and at least one α-olefin having 2 or more carbon atoms, or a mixture of carbon monoxide and at least one α-olefin and vinyl acetate, It is a copolymer with at least one monomer selected from unsaturated carboxylic acids and aliphatic unsaturated carboxylic esters. Examples of the α-olefin having 2 or more carbon atoms include ethylene, propylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-
1, other than octene-1, usually at least one selected from those having up to 12 carbon atoms are used, preferably ethylene alone, a combination of ethylene and propylene, or ethylene or propylene, Carbon number 4
And α-olefins having 4 to 8 carbon atoms in combination. Also, vinyl acetate added in some cases,
Aliphatic unsaturated carboxylic acids and aliphatic unsaturated carboxylic acid esters are useful for improving the flexibility of the polymer after reduction treatment, improving the adhesion to other substrates, and improving the compatibility in blending with other polymers. Has an effect. Also, before and after the reduction treatment, modification treatment such as saponification reaction, graft treatment, ionomerization, etc. is performed, and in addition to the same improvement effect as above, besides, gas barrier property enhancement / control and toughness etc. are further improved. It is useful for the purpose, and is used in an appropriate amount according to the purpose.

The polyketone can be produced by a known method, for example, as described in US Pat.
473,482, JP-B-47-3733, JP-A-53-128690, JP-A-62-5.
No. 3332, JP-A-1-132629, JP-A-1-201333, Journal of American Chemical Society (1982), No. 104
No. 3,520-3522, etc., and there is no particular limitation, and the weight average molecular weight of a commonly used polyketone is 4,000 to 1,000,000, preferably 50 to 100,000.
00 to 500,000. Also, the solution viscosity (η) using m-cresol at 60 ° C. after hydrogenation described below.
_{sp / c} ) is equivalent to about 0.05 to 5.0. Further, the repetition of the alternating unit in which the carbon monoxide unit and the α-olefin unit are bonded is not particularly limited, but those containing a portion having high repetition (alternability) are preferable from the viewpoint of gas barrier properties.

Next, the carbonyl group [> C = O] in the above polyketone is reduced to give a hydroxymethylene unit [-C
As a method for obtaining a copolymer containing H (OH)-], any method including a known method can be used, including a reaction in which a carbonyl group in a polyketone is finally converted to hydroxymethylene by hydrogenation. Good (for example, Ru / α-alumina-based catalyst and others). Pure hydroconversion finally converted into hydroxymethylene units, excluding those remaining unreacted carbonyl groups or those that have undergone an ether bond, deOH reaction, or partial cross-linking reaction by a side reaction At least 50%, preferably at least 70%, more preferably at least 80%, even more preferably at least 90%,
Most preferably, it is 95% or more. When the hydrogenation conversion is less than the above lower limit, gas barrier properties are hardly exhibited.

The copolymer has a content of hydroxymethylene units obtained by reduction of the carbonyl group derived from carbon monoxide of 10 to 50 mol%, a total of α-olefin units of 40 to 90 mol%, and other residues. It is in the range of 0 to 30 mol%. When the content of the hydroxymethylene unit is less than 10 mol%, the gas barrier property is poor, and the upper limit is 50 mol% due to structural restrictions of the raw material polyketone of the present invention. The content of the hydroxymethylene unit is preferably from 20 to 50 mol%, more preferably from 30 to 50 mol%, even more preferably from 40 to 50 mol%. (However, the group derived from a vinyl ester (vinyl alcohol) which has been optionally added is not included in this group but is included in other residues.) The layer (B) is composed of the copolymer and the other group. May be formed in a mixed system with the above resin. In this case, the proportion of the copolymer is 10% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more. As the resin to be mixed, not only resins having the same type of copolymer but different copolymerization component ratios, but also resins having known gas barrier properties (for example, polyamide-based polymers, polyester-based polymers, EVOH, etc., preferably polyamide-based resins) (Polymer, EVOH) or other ethylene content other than the above (ethylene content: about 55 to 80 mol%)
EVOH, or partially saponified products thereof, or modified products thereof, the thermoplastic resin used for the layer (A), or any of these polymers is modified to, for example, form a carboxylic acid group as a polar functional group. Grafted monomers, or polyketones referred to in the present invention, and polymers produced mainly by side reactions (for example, those having an ether ring) during hydrogenation of the polyketones. It is assumed that at least one kind is selected from them. Also, preferably, EVO
H, at least one polymer selected from polyamide polymers, ionomer polymers and the like.

The ratio of the copolymer in the layer (B) is 50%.
When the amount is less than 10% by weight, a mixture containing at least one resin having the above-mentioned known gas barrier properties as another component is preferable. In this case, the ratio of the known gas-barrier resins to be used as the polymer of the entire layer (B) is preferable. Is less than 50% by weight, and a mixture of the copolymer of the present invention and the above-mentioned resin having a known gas barrier property is 50% by weight or more in a ratio that allows the entire layer (B) to be a polymer. Is more preferred. The barrier property of the layer (B) is preferably about 300 cc [25.4 μm / m ² · 24 h in oxygen permeability.
r · atm (25 ° C., 65% RH)], but more preferably 150 cc [25.4 μm].
^{m / m 2 · 24hr · atm} (25 ℃, RH 65%) ]
The following values.

Next, the film of the present invention contains at least one polymer layer (C) containing thermoplastic polyester as a main component as an inner layer, unlike the main component constituting the layer (A). The layer (C) simultaneously achieves both excellent stretch film-forming properties and heat shrinkability, especially low-temperature shrinkage in shrink wrapping applications, and exhibits mechanical and optical properties. The layer (B), which also acts as a protective layer of the layer, and in which it is difficult to form a stable film with sufficient heat shrinkability with a single layer, imparts sufficient stretching orientation to the layer (B). It exerts an effect of synergistically extracting mechanical characteristics and optical characteristics.

The thermoplastic polyester is Vic
Those having an at softening point of usually 45 ° C. or more and 150 ° C. or less are used. If the Vicat softening point is lower than 45 ° C., the stretched film-forming properties tend to decrease, and the occurrence of necking and uneven thickness are apt to occur, making it difficult to impart an effective orientation to the (B) layer. In addition, dimensional changes occur during the storage and distribution of the film. On the other hand, when the Vicat softening point of the thermoplastic polyester exceeds 150 ° C., similarly, it becomes difficult to give an effective orientation to the layer (B). In addition, the mechanical properties and optical properties of the film are reduced in combination with the decrease in the degree of orientation of the film itself, and the low-temperature shrinkability in the case of a shrink film is poor. Due to the imbalance with the properties, there is a large problem that the zigzag whitening peeling phenomenon easily occurs at the time of heat shrinkage. The preferred Vicat softening point range of the thermoplastic polyester is from 50 ° C to 140 ° C, more preferably from 60 ° C to 120 ° C. Where Vicat
The softening point is determined according to ASTM D-1525-76 (Rate
B, load 1 kg).

When the thermoplastic polyester as the main component constituting the polymer layer (C) is disposed adjacent to the layer (B), the thermoplastic polyester is not particularly limited in consideration of the interlayer adhesiveness. It is preferably a copolyester, more preferably a copolyester having a low crystallinity and a low melting point, and further preferably a substantially amorphous copolyester. Further, there is a copolymer obtained by copolymerizing a component having a higher barrier property (for example, a mixed copolymer of an aromatic monomer as an alcohol component). Specifically, for example,
When alcohol is used as the copolymerization component, ethylene glycol is generally used, but propylene glycol, 1,4-butanediol, 1,5
-Pentanediol, 1,6-hexanediol, neopentyl glycol, polyethylene glycol, polytetramethylene glycol, cyclohexanediol (1
・ Types 4 and 1.2), cyclohexane dimethanol (1 type)
.4 type, 1.2 type), xylylene glycol, or at least one diol selected from other known diols, including ethylene glycol and a combination of one of these diols, or including ethylene glycol Instead, any one of the above diols as a base and at least one of the other diols may be contained.

On the other hand, as an acid component of the copolymer, terephthalic acid is generally used. In addition, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, other aromatic compounds, or an ester having an aromatic ring as an ester. Dicarboxylic acid having a substituent that does not contribute to the chemical reaction. Also, succinic acid,
At least one selected from adipic acid, sebacic acid, other aliphatic dicarboxylic acids, and the like, or other known ones
May contain some dicarboxylic acids.

In particular, when used for shrink wrapping,
Either the alcohol component or the acid component may be copolymerized and used, or both components may be copolymerized and used. Examples of preferred combinations include, for example, ethylene glycol as a main component,
Examples include those containing 40 mol% or less of 4-cyclohexanedimethanol and copolymerized using terephthalic acid as an acid component. In that case, the more preferable ratio of copolymerization is 1,
20 to 40 mol% of 4-cyclohexanedimethanol,
More preferably, it is about 25 to 36 mol%. Of these, those having a crystallinity (measured by a wide-angle X-ray diffraction method) of 30% or less, more preferably 10% or less, and further preferably substantially amorphous as a raw material are preferred. or,
A mixture of two or more kinds, such as a blend of the above polyesters or a blend with another polyester other than the above, may be used.

When a resin other than the above is mixed and used, at least one resin is used as long as the original characteristics are not impaired.
The kinds of resins may be mixed within a range not exceeding 50% by weight, and the amount is preferably 40% by weight or less, more preferably 30% by weight or less, and further preferably 20% by weight or less. Examples of the resin to be mixed include those of the same type as the thermoplastic polyester (for example, those having different molecular weights, the composition of the copolymerization components, the component ratios, etc.), as well as polyamide polymers, EVOH, ethylene-vinyl acetate. Copolymers and partially saponified products thereof, ethylene-aliphatic unsaturated fatty acid copolymers, ethylene-aliphatic unsaturated fatty acid ester copolymers, ionomer resins, polyethylene resins (high-pressure low-density polyethylene, linear low-density polyethylene) , Ultra-low-density polyethylene, high-density polyethylene, etc.), polypropylene-based resin, styrene-conjugated diene block copolymer and at least a part of the block copolymer hydrogenated, or by modifying these polymers, For example, a product obtained by grafting a monomer having a carboxylic acid group as a polar functional group or contained in the layer (B). Copolymers containing hydroxy methylene units of the components, or other polyketones referred to in the present invention, it is possible to use a known resin other than the above selected at least one from among them.

The film of the present invention comprises a total of at least four layers of a thermoplastic resin layer (A) forming a surface layer and polymer layers (B) and (C) as inner layers. Is, for example, in the case of four layers: A / B / C / A
In the case of five layers, such as: A / B / C / B / A, A / C / B / C
/ A, A / B / A / C / A, etc. for 7 layers: A / B / A
/ C / A / B / A, A / B / A / B / C / B / A, A /
B / C / A / C / B / A, A / C / B / A / B / C /
A, A / C / A / B / A / C / A, A / C / B / C / A
/ C / A, A / B / A / C / A / C / A, A / B / A /
B / A / C / A, A / B / C / A / B / C / A, A / B
/ C / B / A / C / A, etc., but is not limited thereto. 6 layers, 8 layers,... Or more. When two or more layers (A), (B), or (C) are provided, the resins constituting the layers may be the same or different. The layer (A) may be a multilayer of a polymer mainly composed of different thermoplastic resins, for example, A ₁ / A ₂ , and the same applies to the layer (B) or the layer (C).

A major feature of the film of the present invention is that the layer (B) and the layer (C) have practically sufficient interlayer adhesion, which is advantageous for the practicality of the film. However, if necessary, an adhesive layer made of another known adhesive resin may be provided if necessary in order to improve the adhesive strength between the layers depending on the use conditions. Examples of the resin used for the adhesive layer include a soft ethylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer, and an ethylene-α-olefin copolymer.
Aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, or a multi-component copolymer consisting of at least two kinds of free combinations of ethylene and each monomer to be copolymerized, Or a partially saponified ethylene-vinyl acetate copolymer, at least one α-olefin having 2 or more carbon atoms and carbon monoxide and vinyl acetate, at least one of polyketones referred to in the present invention, an aliphatic unsaturated carboxylic acid,
A copolymer composed of at least three kinds of monomers composed of at least one kind of monomer selected from aliphatic unsaturated carboxylic acid esters (however, the ratio of each monomer component is limited to the contents described in the present invention) Are not used.), Thermoplastic polyurethane, known acid-modified polyolefins including the above, and the like.

Further, in order to improve the tear resistance, impact resistance, toughness, etc., the film of the present invention further comprises, as an inner layer, a thermoplastic resin used in the layer (A) of the present invention and other resins. Another layer made of a known thermoplastic resin may be provided. These include, for example, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer (for example, ethylene-acrylic acid copolymer, ethylene-
Methacrylic acid copolymer), ethylene-aliphatic unsaturated carboxylic acid ester copolymer (for example, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer), 4-methyl-pentene-1 type A polymer, a polypropylene-based polymer, and a polybutene-based polymer, all of which include a copolymer. Further, an ethylene-based polymer (having a density of 0.870 comprising ordinary low density, medium density, high density polyethylene and ethylene-α-olefin copolymer)
０．９0.940 g / cm ³ linear low density polyethylene, ultra low density polyethylene, etc.), ethylene-α-olefin copolymer or softer polymer composed of different α-olefin copolymer, ion-crosslinkable copolymer , A polystyrene-based polymer, a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene derivative and a derivative thereof, a polyamide-based polymer,
Examples thereof include crystalline 1,2 polybutadiene, and at least one of these is used. Layers made of these resins are (A) layer, (B) layer, (C) layer, each inner layer, or (A) layer and (B) layer, (B) layer and (C) layer, The layers may be arranged between the layers A) and (C), and the above-mentioned adhesive layer may be similarly provided between the layers. These may be freely combined according to the purpose.

Further, the film of the present invention has a heat shrinkage of at least 20% and a heat shrinkage stress of at least 50 g / mm ² . Here, each of the heat shrinkage and the heat shrinkage stress is a value in at least one direction of the warp and the weft, and usually means a value developed and measured at 60 to 220 ° C. When used for shrink wrapping, the temperature is preferably 70 to 150 ° C., more preferably 8 to 150 ° C.
It is a value at 0 to 120 ° C., and preferably 100 to 220 ° C., and more preferably 110 to 200 ° C. when used as an adhesive wrap package.

The reason why the heat shrinkage and the heat shrinkage stress are the above-mentioned values is necessary to satisfy the practicality as one of the objects of the present invention as a film for shrink wrapping, and the heat shrinkage is 20%. If it is less than 10, the fit after shrinkage during shrink wrapping becomes insufficient, which may cause wrinkles and lumps after packing. When the heat shrinkage stress is less than 50 g / mm ^2, the same problem as described above occurs in shrink wrapping, and the heat shrinkage stress is common to all applications in which the film of the present invention is used (including coherent wrap). As a problem, the modifying effects (various mechanical strength, stiffness, transparency, cutability, etc.) by stretching are insufficient.

When the film of the present invention is used especially for shrink wrapping, the heat shrinkage at a temperature 30 ° C. higher than the Vicat softening point of the thermoplastic polyester which is the main component of the layer (C) is as follows. It is preferably at least 20% in at least one direction, more preferably at least 30%. Here, 30% from the Vicat softening point of the thermoplastic polyester which is the main component of the (C) layer.
The reason for expressing the heat shrinkage of the film at a high temperature is that the layer (C) provides the main stretching orientation for developing the heat shrinkability of the film, so that the shrinkage property of the film is lower than that of the layer (C). The point which is relatively strongly affected by the Vicat softening point of the constituent resin and the practical shrinkage property is 30 ° C. higher than the Vicat softening point of the resin forming the layer (C).
This is because it can be almost expressed by shrinkage characteristics at a high temperature. Further, the film is required to have stability so as not to cause dimensional change during the distribution process including storage, and the shrinkage manifestation temperature of the film is desirably 45 ° C or higher, preferably 55 ° C or higher. However, the shrinkage onset temperature of the film refers to the temperature at which the heat shrinkage becomes 5%.

A preferable heat shrinkage stress is 70 g / mm.
² or more, more preferably 90 g / mm ² or more. Although the upper limit is not particularly limited, it is usually preferably 500 g / mm ² or less when used for shrink wrapping.
If it exceeds 00 g / mm ² , there is a danger that deformation may occur depending on the contents of the package, thereby damaging the appearance or breaking the seal portion. The preferred upper limit of the heat shrinkage stress is 400.
g / mm ² . This upper limit is not limited to the case where it is used for other uses such as close contact wrap. The heat shrinkage stress value may be a part of the heat shrinkage stress value of the shrinkage stress characteristic measured at each temperature at which the heat shrinkage is developed, as long as it falls within the above range.

The polymer layers (A), (B) and (C) of the present invention each contain a plasticizer, an antioxidant, a surfactant, a coloring agent, and an ultraviolet absorber as long as the original properties are not impaired. , A lubricant, an inorganic filler, etc., and one or both sides of the surface of the film of the present invention may have antifogging property, antistatic property, adhesion, lubricity, etc. Surface modification such as corona treatment, plasma treatment, or a coating treatment with a surfactant, an antifogging agent, an antistatic agent, or the like as Group (2) may be used, or a known treatment as Group (3). An adhesive or a pressure-sensitive adhesive may be coated. For example, group (2) includes polyhydric alcohol partial fatty acid esters such as sorbitan fatty acid esters, glycerin fatty acid esters, and polyglycerin fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, and polyoxyethylene. Ethylene oxide adducts such as sorbitan fatty acid esters and polyoxyethylene glycerin fatty acid esters; amines such as alkylamines, alkylamides, alkylethanolamines, and alkylethanolamides; amides; polyalkylene glycols; granidine derivatives; Agents, sulfonate derivatives, quaternary ammonium salts, pyridinium salts, imidazoline derivatives, polyvinyl alcohol,
Acrylic acid-based hydrophilic polymer, a polymer having a pyrrolidium ring in the main chain, and further include silica sol, at least one or more of alumina sol and the like,
Group (3) includes mineral oil, liquid polybutene, fats and oils not included in the former, known plasticizers,
There are other viscous liquids (100 centipoise or more) and the like, which are used alone or in combination as appropriate. Further, the above-mentioned treatments or additives of each group may be freely combined.
Further, in addition to the above, a surface may be improved by mixing a petroleum resin, a hydrogenated petroleum resin, a natural rosin, an esterified rosin or the like.

The overall thickness of the heat-shrinkable multilayer film of the present invention is not particularly limited, but is generally 100 to 1000 μm when used as a sheet, preferably when used as a film. 100μ
m, more preferably 7 to 80 μm. When the thickness is less than 5 μm, the film tends to be insufficiently stiff and tends to be torn.
The possible thickness of the inner layer (B) as the main gas barrier layer is also reduced, which causes practical problems. On the other hand, if the thickness exceeds 100 μm, the film becomes too stiff and has problems such as poor fit and sealability. or,
The responsiveness of shrinkage may be poor or the overall shrinkage force may be too strong, resulting in impaired finish. The thickness of the inner layer (B) as a preferred embodiment is 0.5
To 20 μm, preferably 0.8 to 15 μm.
If the thickness is less than 0.5 μm, there is a risk that the probability of occurrence of pinholes due to foreign substances such as gel increases and the quality of gas barrier properties deteriorates due to the influence of thickness unevenness. On the other hand, if it is 20 μm or more,
The cost is increased due to the use of a high-priced resin, or the performance is excessive. In addition, a problem occurs in the stretchability.

The total thickness of the layer (C) is appropriately selected according to various constitutions of the heat-shrinkable multilayer film of the present invention.
Generally, it is 1 to 60 μm, preferably 2 to 40 μm, more preferably 3 to 30 μm. If it is less than 1 μm, the effect of improving stretching and the effect of imparting orientation are poor, and it is difficult to obtain practical shrinkage characteristics. On the other hand, if it exceeds 60 μm, troubles due to excessively strong waist and contraction force tend to occur.
Further, the ratio of the total thickness of the layer (C) to the total thickness of the layer (B) is 0.3 to 20, preferably 0.5 to 20, more preferably 0.7 to 18, and even more preferably 1.0. ~ 15. The lower limit is mainly limited by stretching improvement properties (stability, expandability of stretching condition range), and the upper limit is limited to avoid saturation and excess performance of stretching improvement effect, orientation imparting effect, and expression effect of shrinkage performance.

The total thickness of the layer (A) 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 60 μm, preferably 3 to 50 μm.
More preferably, it is 5 to 40 μm. (However, when the above-mentioned adhesive layer is used, the thickness used is included in the total thickness of the layer (A).) The lower limit of the total thickness of the layer (A) is the effect of developing mechanical strength such as tear strength. , And sealability, and the upper limit is limited to avoid substantial adverse effects on stretch film forming properties and shrinkage and excessive performance.

Next, an example of a method for producing the multilayer film of the present invention will be described, but the present invention is not limited thereto. First, each layer (A), (B) of the multilayer film of the present invention,
The polymer constituting the (C) layer and other layers used as required) is melted in each extruder, co-extruded with a multilayer die and quenched, and at least the (C) layer is substantially in an amorphous state. To obtain a raw multilayer film. The quenching at the time of co-extrusion and the fact that at least the (C) layer is kept substantially in an amorphous state is for facilitating the subsequent stretching film formation, providing effective molecular orientation and uniformity of thickness. It is important to achieve the same. When the layer (C) is composed of a mixed resin, at least the thermoplastic polyester as a main component is kept in an amorphous state. The extrusion method is
There is no particular limitation, and a multilayer T-die method, a multilayer circular method, or the like can be used, but the latter is preferred. The multilayer film raw material thus obtained is stretched under a temperature condition suitable for heating to give orientation. As a stretching method, a roll stretching method, a tenter method,
Although there is no particular limitation, such as an inflation method (including a double bubble method), a method of forming a film by simultaneous biaxial stretching is more preferable than stretchability and other rationality. The stretching is performed in at least one direction at an area stretching ratio of 5 to 60 times, preferably 8 to 50 times, and is appropriately selected depending on the required heat shrinkage ratio and the like depending on the application. If necessary, post-processing, for example, heat setting, lamination with other kinds of films, etc. may be performed.

Further, in the film of the present invention, at least one layer thereof may be cross-linked. In this case, even if the degree of cross-linking in the thickness direction is substantially uniform, a specific layer is mainly cross-linked. In the case where one surface layer is mainly used and gradually changes in the thickness direction, both surface layers may be mainly used or have a timely distribution in the thickness direction. This cross-linking treatment is performed before and after stretching film formation.
0 kV energy), ultraviolet rays, X-rays, α-rays, γ
One-sided, two-sided irradiation with energy rays such as lines, and irradiation in which energy distribution and inclination occur in the thickness direction, etc.
Alternatively, a method of performing heat treatment after addition of a peroxide or the like (in some cases, a cross-linking aid may be used in a specific layer and a cross-linking retarder or the like may be used in a specific layer), or a combination of both methods, or a known method A reforming treatment may be performed, and a method using an electron beam (for example, by controlling the penetration depth to a predetermined value with energy of 50 to 1000 kV) is preferably clean. Heat treatment, heat sealability,
In particular, it is also possible to improve the sealing property in high-speed packaging and the stretching film forming stability (suppression of necking, uniformity of thickness, improvement of stretching ratio, expansion of stretching temperature condition width, etc.). Used accordingly.

As described above, the film of the present invention is excellent in melt processability and stretch film forming property, has low temperature and heat shrinkability, and has not only mechanical properties and optical properties, but also in practical shrink packaging. Is a novel gas barrier film that does not easily cause the zigzag whitening phenomenon and has excellent heat sealing properties. These are mainly suitable for packaging materials, especially shrink wrapping, and are films that can also be used as home and commercial close-contact wrap films, taking advantage of their excellent gas barrier properties.

[0045]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Hereinafter, measurement and evaluation methods in the present invention and examples will be described. (1) Crystallinity The raw material resin was sufficiently annealed to obtain an equilibrium state, which was determined by a wide-angle X-ray diffraction method. The X-ray apparatus is Rotorflex RV-200B (Rigaku Electric Co., Ltd.)
Acceleration voltage: 50 KV, using a monochromator)
Tube current: 160 mA (target: Cu), 2θ: 5
Performed at ３６36 °. In addition, for simplicity, wide-angle X
A sample whose crystallinity is fixed by X-ray diffraction is determined by the density method (JIS
K7112-D method) or DSC method (JIS K)
7122) to obtain a calibration curve, and the unknown sample may be determined by a density method or a DSC method. (2) Vicat softening point After sufficiently heating and melting the raw material resin, the crystalline resin is rapidly cooled to such an extent that crystallization is suppressed so that it becomes substantially amorphous, and has a thickness of 3 ± 0.2 mm. Sample of AS
TM D1525-76 (Rate: B, load 1kg)
It measured according to. (3) Heat shrinkage rate A 100 mm square film sample is placed in an air oven type constant temperature bath set at a predetermined temperature, and the sample is allowed to shrink freely.
After processing for 0 minutes, the shrinkage of the film was determined and expressed as a percentage of the value divided by the original dimension. In the case of uniaxial stretching, stretch packaging was used, and in the case of biaxial stretching, which is a preferred embodiment, the average in the vertical and horizontal directions was used. (4) Heat shrinkage stress (hereinafter abbreviated as “ORS”) A film was sampled in a strip shape having a width of 10 mm, and the sample was placed between a chuck with a strain gauge and a distance of 50 m.
m was set without loosening, immersed in silicone oil heated to each temperature, and the generated stress was detected. For silicone oil at 80 ° C. or lower, the maximum value within 20 seconds after immersion, and when it exceeds 80 ° C., the maximum value within 10 seconds was adopted, and the average in the vertical and horizontal directions was used. (5) Tensile modulus was performed according to ASTM D-882-67, and expressed as a value obtained by converting stress at 2% elongation to 100%. (6) Haze (HAZE) Measured according to ASTM-D-1003-52. (7) Heat seal strength The film pieces were stacked so that the heat seal layers of the stretched film faced each other, and the pieces sealed with an impulse sealer were used as test pieces having a width of 15 mm, and the peel strength was measured with a tensile tester. (8) Oxygen permeability (O ₂ TR) Measured by the method of ASTM-D-3985. [Unit: cc / m ² · 24 hr · atm (23 ° C.)] (9) Film-forming stability Continuous film-forming stability of the film (continuous film-forming stability of stretched bubbles) when heat stretching is performed in a predetermined method. ) And the thickness unevenness of the resulting film.

Here, the thickness unevenness of the film is determined by using a dial gauge at least 25 points at equal intervals in the entire width (width) direction of the film and at least 25 points at 3 cm intervals in the flow (vertical) direction, for a total of 50 points. The above thickness is measured, and the average value is calculated first. Next, 1/2 of the difference between the maximum value and the minimum value
Is expressed as a percentage with respect to the previously calculated average value, and is indicated with a plus or minus sign. A: The stretching start position of the film (stretched bubble) is almost constant, the stretching pattern is extremely stable, and the continuous stability is good. ：: Film thickness unevenness is within ± 15%. Δ: The stretching start position fluctuates or the stretching pattern is unstable. ×: Film breakage, bubble puncture frequently occurred. Alternatively, even if stretching can be performed, the stretching start position greatly fluctuates, and the thickness unevenness exceeds ± 25%. (10) Gel fraction A sample was extracted in boiling p-xylene (12 hours), and the ratio of the insoluble portion was represented by the following formula, and used as a measure of the degree of crosslinking. Gel fraction (% by weight) = (weight of sample after extraction / weight of sample before extraction) × 100 However, a polymer which has not been cross-linked and which is not completely dissolved in boiling p-xylene is dissolved in p-xylene. Instead, the measurement is carried out by appropriately changing to a solvent which can be completely dissolved at the time of boiling.

Example 1 Ethylene-α-olefin copolymer; a ₁ [comonomer;
1-hexene, density; 0.912 g / cm ³ , Vica
t softening point: 87 ° C, MFR (190 ° C, 2.16 k
g); 2.0] with an additive in which oleic acid monoglyceride and diglycerin monolaurate are in a weight ratio of 1: 1.
The surface layer containing 0% by weight and one of the inner layers are
The acid component is mainly terephthalic acid, and the diol component is 1,
Copolyester consisting of 30 mol% of 4-cyclohexanedimethanol and 70 mol% of ethylene glycol; c
₁ [Vicat softening point: 82 ° C, crystallinity: 0% (amorphous)], a copolymer of ethylene and carbon monoxide as a resin for the core layer, number average molecular weight: about 50,000, solution viscosity: η
_{sp / c} = 1.60 (measured with m-cresol solution at 60 ° C)
A copolymer containing a hydroxymethylene unit obtained by hydrogenating a polyketone having a carbonyl group content of 49 mol%; b ₁ [hydroxymethylene unit is 47 mol%
(In this case, the hydrogen conversion rate is 97%), the ethylene unit is 51
Mol%, with other residues 2 mol%] in the core layer, as further adhesive layers, ethylene - vinyl acetate copolymer; a ₂ Vinyl acetate content: 25 wt%, MFR (190 ° C., 2.16
kg); 2.3], and the layer arrangement is a ₁ / a ₂ / c ₁ /
After extruding using an annular multilayer die so as to have 7 layers of b ₁ / c ₁ / a ₂ / a ₁ , the mixture is rapidly cooled and solidified with a refrigerant, and the folding width is 2
Each of the layers having a thickness of 00 mm and a thickness of 480 μm was used to prepare a tubular raw material having a uniform thickness accuracy. At this time, the inside of the tube was filled with diglycerin oleate and coated with an inner surface by squeezing with a nip roll. The thickness of each layer is 120 μm / 40 μm / 60 in order from the outside of the tube.
μm / 40 μm / 60 μm / 40 μm / 120 μm.

Then, the raw material is passed between two pairs of differential nip rolls, heated to 101 ° C. in a heating zone, and air is injected thereinto in a stretching zone under the same atmosphere to form bubbles. The film was simultaneously biaxially stretched to a stretching magnification of 5 times and a width of 4 times, and cooled by blowing cold air at 20 ° C. in a cooling zone to obtain a film having a thickness of 24 μm. The stretching stability of the film is extremely good (◎), the tensile elasticity of the obtained film is 91 kg / mm ² , and the haze is 1.1.
%, Heat shrinkage (112 ° C) 46%, ORS (100 ° C)
271 g / mm ² , seal strength 1.4 kg / 15 mm
The width and O ₂ TR are also 38 cc / m ² · 24 hr · atm (2
3 ° C., excellent barrier property and RH 65%), also especially c ₁
/ B delamination using a cellophane tape between ₁ also has a practically sufficient interlayer adhesion as a whole difficult, mechanical strength, optical properties and low temperature shrinkability was excellent gas barrier film seal strength . Also, when the film is wound into a single film, the additive on the surface corresponding to the inside of the tube is transferred to the other surface, and the upper open container filled with water at 20 ° C. is sealed with this film. 5 ℃
When stored in a refrigerated showcase, almost no water droplets were found, and it had good anti-fog properties.

Example 2 Ethylene-α-olefin copolymer;
₃ [comonomer; 4-methyl-pentene-1, density;
0.910 g / mm ³ , Vicat softening point; 82 ° C., M
FR (190 ° C., 2.16 kg); 3.2], a copolymer containing hydroxymethylene units obtained by hydrogenating a polyketone having a carbonyl group content of 47 mol% to a resin for the core layer; b ₂ (39 mol% of hydroxymethylene units (hydrogen conversion in this case: 83%), solution viscosity; η _{sp / c} = 1.
53, 47 mol% of ethylene units, 6 mol% of propylene units, and 8 mol% of other residues) were co-extruded and co-stretched under the same conditions as in Example 1 to obtain a film having a thickness of 24 μm. (At this time, the additive treatment was performed on each surface layer in the same manner.) Stretching film formation stability was also good (◎),
The resulting film had a haze of 1.2% and a heat shrinkage (11
2%) 44%, ORS (100 ° C.) 265 g / mm ² ,
O ₂ TR is 55 cc / m ² · 24 hr · atm (23
° C, 65% RH), the tensile modulus was 89 kg / mm ² , and the seal strength was 1.3 kg / 15 mm width.

Next, the same raw material was used and in the same manner as in Example 1, the heating and stretching temperature was 122 ° C., the stretching ratio was 4 ×,
Stretch film formation is performed under the conditions of 4 times the width, and the thickness is similarly 30 μm.
Was obtained stably. This film has a haze of 1.9%, a heat shrinkage (130 ° C.) of 26%, and an ORS
(100 ° C) 93 g / mm ² , O ₂ TR 46 cc / m
^{2 · 24hr · atm (23 ℃} , RH 65%), tensile modulus is 78kg / mm ^2, even seal strength 1.6k
g / 15 mm in width, and was a gas barrier film having excellent heat shrinkage and excellent optical properties and mechanical properties as in the case of the above film.

Example 3 An ethylene-methacrylic acid copolymer; a ₄ [methacrylic acid content; 9.0% by weight, Vicat softening point; 80 ° C., MFR (190 ° C.
2160 g); 3], the solution viscosity η _{sp / c} =
1.65, a copolymer containing hydroxymethylene units obtained by hydrogenating a polyketone having a carbonyl group content of 48 mol%; b ₃ (46 mol% of hydroxymethylene units, 52 mol% of ethylene units, and 2 mol of other residues) %), a thermoplastic polyester used in example 1 as a core layer resin; a c ₁ using, further acid modified as an adhesive layer was linear low density polyethylene; a ₅ [density; 0.92 g / cm ^3, MFR (1
3.5 °], each resin is melted by an extruder, and the layer arrangement is a ₄ / a ₅ / b ₃ / c ₁ / b ₃ / a using an annular multilayer die. After extruding into 7 layers of ₅ / a ₄ , it is quenched and solidified with a refrigerant and folded at 20 cm.
Each of the layers having a thickness of 0 mm and a thickness of 198 μm was formed into a tube-shaped raw material having uniform thickness accuracy. (Incidentally, each surface layer contains the same additives as in Example 1 in an amount of 2.5% by weight.) The thickness of each layer of the obtained raw material is 36 μm in order from the outside of the tube.
/ 18μm / 18μm / 54μm / 18μm / 18μm
/ 36 μm.

Then, the raw material was stretched three times in the vertical and horizontal directions at a heating and stretching temperature of 104 ° C. in the same manner as in Example 1 to stably obtain a film having a thickness of 22 μm. The heat shrinkage (112 ° C.) of this film was 34%, and the ORS (1
00 ° C) 195 g / mm ² , haze 1.8%, O ₂ T
R is ^{23cc / m 2 · 24hr · atm} (23 ℃, 65
% RH), seal strength was 1.5 kg / 15 mm width, and tensile modulus was 125 kg / mm ² .

(Comparative Example 1) An ethylene-vinyl alcohol copolymer obtained by saponifying a copolymer of ethylene and vinyl acetate; EVOH-1 (ethylene content: 29 mol%,
Degree of saponification: 99% or more, MFR: 210 ° C., 2.16 k
g); 3.2) a copolymer containing a hydroxy-methylene units obtained by hydrogenating polyketones; except for changing the b ₁ are the same conditions as in Example 1 (drawing ratio also coextruded co stretching the same) Initially, stretchability was relatively stable,
Four hours after the start of extrusion film formation, bubble puncture occurred four times (no puncture occurred in Example 1), and the stretching film formation stability was inferior to that of Example 1; After the lapse of time, the number of gels having a diameter of 2 mm or less observed in the extruded raw material was about 27 per m ² of the raw material, which was about twice that of Example 1.

[0055] (Comparative Example 2) thermoplastic polyester of the inner layer; instead of c _1, 80 mol% acid component of terephthalic acid,
Isophthalic acid 20 mol%, diol component is tetramethylene glycol 97 mol%, ethylene glycol 3 mol%
A 7-layer tubular raw material was obtained in the same manner as in Example 1 except that c ₂ (Vicat softening point: 40 ° C., crystallinity: 15%, melting point: 193 ° C.) was used. . (The thickness of each layer is the same as in Example 1.) Thereafter, stretching was performed in the same manner, but the stretching start position fluctuated and puncture occurred frequently.
The film was barely obtained with a width of 2.4 times, but the heat shrinkage was as low as about 18%, and the thickness unevenness of the film (± 28%)
Uneven wrinkles and streaks after shrinkage
Also, formation of a partially opaque portion was observed, and the stretched film-forming stability and the merchantability were poor.

(Example 4) Polypropylene resin as a resin for the surface layer; a ₆ [ethylene content: 4.5 mol%, M
FR (230 ° C., 2.16 kg); 4, Vicat softening point; 120 ° C.], 30% by weight, acid-modified polypropylene resin; a ₇ [MFR (230 ° C., 2.16 kg); 3, V
icat softening point; 114 ° C.] 40% by weight, polybutene
1; a ₈ [copolymer with propylene; density: 0.910
g / cm ³ , MFR (190 ° C., 2.16 kg);
Vicat softening point; 87 ° C.] using a mixture of 30% by weight, as one of the inner layers, thermoplastic polyester; c ₁ ,
A copolymer containing hydroxymethylene units obtained by hydrogenating a polyketone having a solution viscosity η _{sp / c of} 1.75 and a carbonyl group content of 47 mol% as a resin for the core layer; b ₄ (40 mol of hydroxymethylene units) %, Ethylene units 50 mol%, propylene units 3 mol%, and other residues 7 mol%), each resin is melted by an extruder, and the layer arrangement is (a ₆ + a ₇ + a ₈ ) using an annular multilayer die. ) / C ₁ / b ₄ /
After being extruded into five layers of c ₁ / (a ₆ + a ₇ + a ₈ ), the mixture was rapidly cooled and solidified with a refrigerant, and folded 200 mm in thickness and 4 in thickness.
A tubular raw material having a uniform thickness accuracy of each layer of 00 μm was produced. At this time, the inside of the tube was filled with diglycerin oleate and coated with an inner surface by squeezing with a nip roll. The thickness of each layer of the raw material is 120 μm / 60 μm / 40 μm in order from the outside of the tube.
/ 60 μm / 120 μm.

Next, a film having a thickness of 20 μm was obtained from the raw material in the same manner as in Example 1 by heating at a stretching temperature of 105 ° C., a stretching ratio of 5 times, and a width of 4 times. The stretching film-forming stability is good (）), the heat shrinkage (112 ° C.) is 41%, the haze is 1.9%, the ORS (120 ° C.) is 284 g / mm ² , the tensile modulus is 117 kg / mm ² , and the seal is used. Strength 1.2kg /
15mm width, O ₂ TR is 77cc / m ²・ 24hr ・ a
tm (23 ° C., 65% RH).

Examples 5 to 10 In the same manner as in Example 1, seven-layer films shown in Tables 1 and 2 were obtained. The thickness of the produced raw material is 300
μm, and the stretching was performed at a heating stretching temperature of 96 to 111 ° C., respectively. The stretching ratio (length × width) was 3.1 × 3.0, 3.1 × 3.0, 4 × in the order from Example 5.
3.1, 4.5 × 3.7, 3.3 × 3.0, 4.5 ×
4.2. All of these were excellent in stretch film-forming properties (○ to ◎), and the obtained films were gas barrier films having excellent low-temperature shrinkage and sealing properties, and were excellent in various packaging suitability such as shrink wrapping.

As a comparison, a commercially available heat-shrinkable composite having a symmetrical five-layer structure in which an ethylene-vinyl alcohol copolymer is disposed as a barrier resin in a core layer, linear low-density polyethylene is a surface layer, and both are bonded by an adhesive resin. Crosslinked film (thickness 25
μm) was thermally shrunk in the same manner, and a phenomenon in which the core layer was bent and whitened was observed.
All of the films including the films Nos. To 4 did not have such a phenomenon even after heat shrinkage, and were excellent in optical characteristics.

[0060]

[Table 1]

[0061]

[Table 2]

This tubular material was flattened and crosslinked by an electron beam irradiator (500 kV) so that the gel fraction of both surface layers was equal to about 28%. Film formation was performed 6 times each in the vertical and horizontal directions, and a film having a thickness of 10.5 μm was stably obtained. Heat shrinkage of this film is 21% (130 ° C), ORS
Is a level of 175 g / mm ² (140 ° C.). When the suitability as a wrap film was evaluated, a saw blade cutter (a box for Saran Wrap (registered trademark) manufactured by Asahi Kasei Kogyo Co., Ltd.) was used. Good cutability, good adhesiveness when wrapping using Setomono and glass containers, and even turning the film against microwave heating when pork belly is wrapped, perforation due to melting There was no whitening phenomenon and the suitability for a microwave oven was good.

Example 12 An extruded tube-shaped raw material was produced in the same manner as in Example 1 except that the thickness of each layer (same as the raw material thickness) was changed. At this time, the thickness of each layer of the web is
144 μm / 72 μm / 90 μ in order from the outside of the tube
m / 72 μm / 90 μm / 72 μm / 144 μm. Using this tubular material, the accelerating voltage is 200k
V irradiation, and the gel fraction of one surface layer was 27
%, And the gel fraction of the other surface layer was 0%. The raw film was stretched and formed into a film in the same manner as in Example 1 to stably obtain a film having a thickness of 19 μm (heating and stretching temperature: 127 ° C., stretching ratio vertically and horizontally 6 times each). This film has a heat shrinkage of 49% (120 ° C.) and an ORS (110
° C) 148 g / mm ² , O ₂ TR 43 cc / m ² · 24
It had physical properties of hr.atm. In addition, the gel fraction is 0%
In the case where the outer layer is used as a heat seal layer and the side in contact with the seal bar is used as a highly cross-linked layer for packaging, breakage or wrinkles in the seal portion, which conventionally occurred when increasing the packaging speed, were used. Troubles such as occurrence of cracks were eliminated, and high-speed packaging workability was significantly improved.

Example 13 A terpolymer (containing 39 mol% of carbonyl group) of ethylene, carbon monoxide and vinyl acetate (3 mol%) was hydrogenated (hydrogen conversion: 96).
%), A tubular raw material was prepared under the same conditions as in Example 1 except that a gas barrier resin obtained by saponifying a vinyl acetate group was used as a core layer, and stretched film formation was performed. The stretch film forming property is good (（), the heat shrinkage is 43% (112 ° C.),
ORS (100 ° C.) 249 g / mm ² , O ₂ TR59c
It had excellent physical properties of c / m ² · 24 hr · atm, haze 1.9%, and seal strength 1.3 kg / 15 mm width.

(Examples 14 and 15) An ethylene-α-olefin copolymer containing 2% by weight of glycerin diacetomonolaurate in the resin for the surface layer; a ₃ , c _{3 in} the thermoplastic polyester layer, and ethylene acetic acid as the adhesive layer between them. a copolymer containing an a ₂ and hydroxymethylene units polyketone the core layer resin obtained by hydrogenating,; vinyl copolymer b ₁
In the same manner as in Example 11, and a cross-linking treatment was performed by electron beam irradiation (the gel content of both surface layers was about 26% each). The thickness of each layer is 32 μm / 16 μm / 24 μm / 24 μm / 24 in order from the outside of the tube.
μm / 16 μm / 32 μm. This raw material was stretched by a similar method at a heating and stretching temperature of about 101 ° C. four times each in the vertical and horizontal directions to stably obtain a uniform film having a thickness of about 10.5 μm.

The haze of this film was 1.2%, the heat shrinkage (100 ° C.) was 31%, and the ORS (120 ° C.) was 24%.
1g / mm ² , O ₂ TR is 56cc / m ² · 24hr ·
atm (23 ° C., 65% RH). As Example 14 The film, in the same manner, a thermoplastic polyester; instead of c _3, a polyethylene terephthalate (Vi
Cat softening point: 71 ° C, crystallinity: 45%, melting point: 245
C.), a stretched film was formed under substantially the same conditions as in Example 14 to obtain a film having a thickness of about 10.5 μm.
The haze of this film was 1.1% and the heat shrinkage (101
° C) 22%, ORS (120 ° C) 312 g / m
m ² , O ₂ TR is 54 cc / m ² · 24 hr · atm
(23 ° C., 65% RH). This is Example 15. The films of Examples 14 and 15 were used for another one of home-use contact wraps and subjected to a predetermined heat treatment to reduce the crystallinity of the thermoplastic polyester layer to 1 each.
It was adjusted to 5% and 35%. Apply this film to each 14
-A, 15-a. The heat shrinkage of the film of 14-a is 31% at 120 ° C, and the ORS is 286 g / m at 120 ° C.
m ² . Similarly, the 15-a film has a heat shrinkage of 20% at 185 ° C, and an ORS of 221 g / 180 ° C.
mm ² .

When the suitability of each of the heat-treated films 14-a and 15-a as Examples 14 and 15 and the heat-treated films 14-a and 15-a as wrap films was evaluated, a saw blade cutter [Saran Wrap (registered trademark) manufactured by Asahi Kasei Kogyo KK) was used. ) Box, and good adhesion when wrapped in wrapping with setomono and glass containers. In particular, the heat-treated 14-a and 15-a films are made of pork. There is no roll-up of film, no delamination, no perforation or whitening due to melting, and good suitability for microwave ovens, and good smell barrier properties, especially for acetic acid-based and ester-based products. It had good odor barrier properties and was superior to vinylidene chloride wrap.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-226925 (JP, A) JP-A-6-255057 (JP, A) JP-A-4-276441 (JP, A) JP-A-4-276 364948 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (5)

(57) [Claims] 1. A thermoplastic resin layer (A) forming a surface layer
And at least one of the internal layers composed of at least two layers is a gas barrier polymer layer (B) containing at least one component containing a copolymer having a hydroxymethylene unit, and the other layer is the above-mentioned ( A) A multilayer film comprising at least four layers, which is a polymer layer (C) mainly composed of a thermoplastic polyester different from the main component of the layer, wherein the hydroxymethylene unit is at least one of the carbonyl groups of the polyketone. Part of the polyketone, and the polyketone is a copolymer of carbon monoxide and at least one α-olefin having 2 or more carbon atoms, or carbon monoxide and at least one α-olefin. An olefin and at least one component selected from the group consisting of vinyl acetate, an aliphatic unsaturated carboxylic acid and an aliphatic unsaturated carboxylic acid ester as the following components. Or a modified copolymer thereof, wherein the multilayer film has a heat shrinkage of at least 20% and a heat shrinkage stress of at least 50 g / mm ² . A heat-shrinkable multilayer film characterized by the above-mentioned. 2. The thermoplastic resin constituting the layer (A) is a polypropylene-based polymer, poly4-methylpentene-based polymer, polybutene-based polymer, crystalline 1,2-polybutadiene, polyethylene-based polymer, ethylene-α. Olefin copolymer, soft polymer composed of α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, vinyl A block copolymer of an aromatic hydrocarbon and a conjugated diene derivative and a derivative thereof, or a copolymer of two or more freely selected from monomers of the above copolymer, or a modified polymer of these polymers 2. The heat-shrinkable multilayer film according to claim 1, wherein the heat-shrinkable multilayer film is at least one member selected from the group consisting of a united film and a united film. 3. The heat-shrinkable multilayer film according to claim 1, wherein the proportion of the copolymer having hydroxymethylene units contained in the polymer layer (B) is 10 to 100% by weight. 4. The content of hydroxymethylene units obtained by reducing the ketone of a copolymer having hydroxymethylene units contained in the polymer layer (B) is 10 to 50 mol%.
The heat-shrinkable multilayer film according to claim 1, wherein 5. The heat-shrinkable multilayer film according to claim 1, wherein the copolymer having hydroxymethylene units contained in the polymer layer (B) has a hydrogenation conversion of at least 50%.