WO2005102695A1 - Heat shrinkable film - Google Patents

Abstract

Disclosed is a heat shrinkable film comprising a first layer containing a first polymer mainly composed of a thermoplastic polyester and a thermoplastic polyurethane, and a second layer mainly containing a second polymer wherein the main repeating unit substantially has a halogen or a hydrogen bond. In this heat shrinkable film, the first layer is directly disposed on the second layer.

Description

 Specification

 Heat shrinkable film

 Technical field

 The present invention relates to a heat-shrinkable film for shrink wrapping, and more particularly to a film having good appearance even after shrinkage treatment.

 Background art

 [0002] Shrink wrapping has a beautiful package appearance, enhances product value, keeps the contents sanitary, facilitates visual quality confirmation, and enables quick and tight fixation of irregular or multiple products. Because it can be packaged, it is often used for packaging foods and miscellaneous goods. In particular, when impact strength or pinhole resistance is required for a film, a resin having a strong structure, for example, a laminated polyamide resin, having hydrogen bonds in repeating units, is widely known. On the other hand, films having excellent gas barrier properties for suppressing deterioration and decay of packaged materials and improving the storage period thereof are required for packaging of chemicals, especially electronic parts, etc. mainly in the food field. Polymers having excellent gas barrier properties include a salty bililidene-based copolymer and an ethylene-vinyl alcohol-based copolymer (hereinafter referred to as EVOH). The former contains chlorine, and the latter contains a hydroxyl group in a repeating unit. Due to their strength, they have the problem that they are strongly agglomerated after stretching, resulting in a low heat shrinkage of the resulting film. Further, this film has high required characteristics such as pinhole resistance, and as described above, studies have been made on multilayering with a polyamide resin layer (for example, Patent Document 1). However, this polyamide resin (hereinafter, referred to as PA) also forms a hydrogen bond similarly to EVOH, so that the heat shrinkage is further suppressed. As described above, many of the conventional high-strength films and gas barrier shrink films have low heat shrinkage. When the heat shrinkage is low, the display effect of the product is poor, and in the case of packaging that adheres to the contents, the adhesion is poor, and when the contents are food, the freshness may not be sufficiently maintained.

[0003] On the other hand, in order to solve the above-mentioned problems of EVOH, studies have been made to arrange a layer having thermoplastic polyester strength (for example, Patent Document 2). From this study, it was possible to achieve uniform stretching of the EVOH layer with the thermoplastic polyester layer, achieve low-temperature shrinkage, and It is said that it can eliminate the zigzag whitening phenomenon that occurs due to insufficient shrinkage of the EVOH layer, which tends to occur during thermal shrinkage due to the interlayer adhesion. Zigzag whitening means that the shrinkage is small, the resin and the resin with a large shrinkage are heat shrunk when laminated and the resin has a small heat shrinkage as shown in Figure 1 (film cross section). If the layer mainly composed of fat is too large, it will not follow the shrinkage of the layer mainly composed of fat and bends in a zigzag shape. Say. However, when the inventor performed additional tests in accordance with Patent Document 2, it was confirmed that the difference in thermal shrinkage between the two could not be absorbed depending on the shrinkage conditions of the layer structure “used resin” and zigzag whitening occurred.

[0004] Further, a study was conducted in which a mixture of thermoplastic polyester and thermoplastic polyurethane (hereinafter referred to as TPU) was provided on the surface layer, and a PA layer and an EVOH layer were provided on the inner layer via a modified polyolefin of the adhesive layer ( For example, Patent Document 3) has also been made. It is said that low-temperature brittleness could be improved by mixing thermoplastic polyurethane with this surface layer. However, according to an additional test by the inventor, it was found that this material could not achieve a sufficient heat shrinkage under short-time dry heat shrinkage conditions such as 120 ° C for 5 seconds.

 Patent Document 1: Japanese Patent No. 3418204

 Patent Document 2: JP-A-10-34836

 Patent Document 3: JP-A-9-183200

 Disclosure of the invention

 Problems to be solved by the invention

[0005] The present invention provides a heat-resistant film having excellent optical properties without causing delamination or zigzag whitening even in a laminated film having a large difference in shrinkage ability between layers even after being sufficiently heat-shrinked under a wide range of shrinkage conditions. An object is to provide a shrinkable film.

 Means for solving the problem

[0006] The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention.

 That is, the present invention is as follows.

[0007] 1. A first layer containing a first polymer mainly composed of a thermoplastic polyester and a thermoplastic polyurethane, and a second polymer mainly composed of a repeating unit substantially having a halogen or a hydrogen bond. A second layer serving as a main body, wherein the first layer and the second layer are directly A laminated heat shrinkable film.

 [0008] 2. The heat-shrinkable film according to item 1, wherein the second polymer is selected from the group consisting of the following (a) to (d)!

 (a) Polyamide

 (b) Ethylene vinyl alcohol copolymer

 (c) Poly salty duck biylidene

 (d) A mixture comprising a polar group-containing polyolefin and any one of (a) to (c).

[0009] 3. The heat-shrinkable finolem according to item 1, wherein the thermoplastic polyester has a crystallinity of 30% or less.

 [0010] 4. The heat shrinkage force in a dry heat treatment at 120 ° C. The heat shrinkability according to item 1, which is 30% or more in one direction of MD or TD and 20% or more in the other direction. the film

[0011] 5. The heat-shrinkable film according to item 1, comprising a laminate in which the second layer, the first layer, and the second layer are directly laminated in this order.

[0012] 6. From a laminate in which the second layer in which the second polymer is a polyamide, the first layer, and the second layer containing a resin having gas barrier properties are directly laminated in this order. Item 1. The heat-shrinkable film according to item 1.

[0013] 7. Use of the heat-shrinkable film according to item 1 for a gas replacement package.

[0014] 8. A term for a package used for a method of covering a content with a package, depressurizing the inside of the package to bring the package into close contact with the content, and further heat shrinking the package. Use of the heat-shrinkable film described in 1.

 The invention's effect

 [0015] According to the present invention, even in a laminated film having a large difference in shrinkage ability for each layer, even after being sufficiently heat-shrinked under a wide range of shrinkage conditions, zigzag whitening does not occur, and the heat resistance is excellent in optical properties. A shrinkable film can be provided, and a beautiful shrink product can be obtained while satisfying required characteristics such as strength and barrier properties.

 Brief Description of Drawings

FIG. 1 is a cross-sectional view of a film showing an example of zigzag whitening. BEST MODE FOR CARRYING OUT THE INVENTION

 [0017] The heat-shrinkable film of the present invention needs to have a first layer (hereinafter, referred to as layer A) containing a first polymer mainly composed of thermoplastic polyester and thermoplastic polyurethane. Thermoplastic polyester is necessary to exhibit the above-described effects described in Patent Document 2. The thermoplastic polyurethane has a strong adhesive strength with layer B, which is directly laminated on layer A described later, and suppresses delamination after shrinkage and zigzag whitening after shrinkage even under conditions where the shrinkage ability with other layers is different. It has important effects.

 [0018] The thermoplastic polyester in the present invention is classified into an aromatic polyester and an aliphatic polyester according to its chemical structure, and both are suitably used in the present invention. Examples of the aromatic polyester include polyethylene terephthalate, polybutylene terephthalate, and copolymerized polyester. Copolymerized polyesters are often used because their physical properties such as stretchability, shrinkage, and optical properties can be changed depending on the types of monomers and their ratios. For example, when alcohol is used as the copolymerization component, ethylene glycol is generally used. Other copolymerization components include propylene glycol, 1,4-butanediol, 1,5 pentanediol, 1,6 hexanediol, Examples include polyethylene glycol such as neopentyl glycol, dimethylene glycol, and triethylene glycol, polytetramethylene glycol, cyclohexane dimethanol, xylylene glycol, and at least one other diol selected from known compounds. And one of these diols, or one containing the other diol based on any one of the above diols without ethylene glycol. On the other hand, as the acid component of the copolymer, terephthalic acid is generally used, and in addition, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, and other aromatic compounds, or the aromatic ring thereof are subjected to esterification reaction. Examples include dicarboxylic acids having non-contributing substituents. Further, it may contain at least one dicarboxylic acid selected from succinic acid, adipic acid, sebacic acid, other aliphatic dicarboxylic acids, and other known ones. In addition, a mixture of two or more of the above polyesters, or a mixture with other polyesters other than those described above, as long as the mixture is thermoplastic, may be used.

The aliphatic polyester used in the present invention includes polylactic acid-based resin and aliphatic di Aliphatic polyesters obtained by polycondensation of carboxylic acid and aliphatic diol as main components, aliphatic polyesters obtained by ring-opening polymerization of cyclic ratatones, synthetic aliphatic polyesters, poly (hydroxyalkanoic acid) biosynthesized in cells, etc. And aliphatic aromatic polyesters having a structure in which a part of these polyesters is substituted with an aromatic compound. Many of these have recently been known as biodegradable resins.

 [0020] The polylactic acid-based polymer is a polylactic acid homopolymer and a copolymer containing 50% by weight or more of a lactic acid monomer unit, and is composed of a polylactic acid homopolymer and lactic acid and other hydroxycarbonic acid. And a copolymer with a compound selected from the group consisting of ratatones. When the content of the lactic acid monomer unit is less than 50% by weight, the heat resistance and transparency of the film tend to decrease. Preferably, it is a polylactic acid homopolymer and a copolymer containing at least 80% by weight of lactic acid monomer units, or a mixture of these copolymers. More preferably, the polylactic acid homopolymer and lactic acid monomer units are 90% by weight. % Or a mixture of these copolymers.

 [0021] Lactic acid has L-lactic acid and D-lactic acid as optical isomers, and polylactic acid formed by polymerizing them has D-lactic acid units of about 10% or less and L-lactic acid units of about 90% or more. Or polylactic acid with L-lactic acid units of about 10% or less and D-lactic acid units of about 90% or more, and crystalline polylactic acid with an optical purity of about 80% or more, and D-lactic acid units of 10% to 90% It is known that there are polylactic acids with L-lactic acid units of 90% to 10% and amorphous polylactic acids with an optical purity of about 80% or less.

[0022] Examples of the monomer used as a copolymer component with lactic acid include hydroxycarboxylic acids such as glycolic acid, ₃ -hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxylvaleric acid, and 6-hydroxy Cabronic acid and the like. In addition, examples of the aliphatic cyclic ester include glycolide, lactide, 13-propiolatatone, γ-butyrolataton, δ-valerolataton, ε-force prolataton, and ratatones in which various groups such as a methyl group are substituted. . Examples of dicarboxylic acids include succinic acid, dataric acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid. Examples of polyhydric alcohols include bisphenol / ethylene oxide addition reaction products such as bisphenol / ethylene oxide addition products. Alcohol, ethylene glycol, propylene glycol, butanediol, hexanediol, octanedi Examples thereof include aliphatic polyhydric alcohols such as all, glycerin, sorbitan, trimethylolpropane, and neopentyl glycol; and ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.

 [0023] As a polymerization method of the polylactic acid-based resin, a known method such as a condensation polymerization method or a ring-opening polymerization method can be employed. Further, a method of increasing the molecular weight by using a binder such as polyisocyanate, polyepoxy compound, acid anhydride, and polyfunctional acid chloride can also be used.

 [0024] The weight average molecular weight of the polylactic acid-based resin is preferably in the range of 10,000 to 100,000. If the molecular weight is less than 10,000, only a film having poor mechanical properties can be obtained. If the molecular weight exceeds 1,000,000, the melt viscosity becomes high, and it is difficult to obtain a film having stable physical properties with a normal processing machine.

 [0025] Examples of the aliphatic polyester obtained by polycondensing an aliphatic dicarboxylic acid and an aliphatic diol as main components include aliphatic acids such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecane diacid. Aromatic power of carboxylic acid, terephthalic acid, isophthalic acid, etc.Rubonic acid and aliphatic diol such as ethylene glycol, 1,3-propion glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, etc. Examples include polycondensations selected from more than one species.

 [0026] Examples of the aliphatic polyester obtained by ring-opening polymerization of cyclic ratatatons include ε-force prolatatatone, δ

 Examples include ring-opened polymers selected from one or more cyclic monomers such as valerolatatone and / 3-methyl- valerataton.

 Examples of the synthetic aliphatic polyester include copolymers of succinic anhydride, a cyclic acid anhydride such as ethylene oxide and propylene oxide, and oxysilanes.

[0028] Examples of poly (hydroxyalkanoic acid) biosynthesized in the cells include poly (3-hydroxybutyric acid), poly (3-hydroxypropionic acid), poly (3-hydroxyvaleric acid), and poly (3-hydroxyvaleric acid). —Hydroxybutyric acid 3-hydroxyvaleric acid) copolymer, poly (3-hydroxybutyric acid 3-hydroxyhexanoic acid) copolymer, poly (3-hydroxybutyric acid 3-hydroxypropionic acid) copolymer, poly ( Examples thereof include 3-hydroxybutyric acid 4-hydroxybutyric acid) copolymer, poly (3-hydroxybutyric acid 3-hydroxyoctanoic acid) copolymer, and poly (3-hydroxybutyric acid 3-hydroxydecanoic acid) copolymer. Can be [0029] Examples of the aliphatic aromatic polyester include polybutylene succinate phthalate copolymer, polyethylene succinate phthalate copolymer, polybutylene adipic phthalate copolymer, and polyethylene adipic phthalate copolymer. Examples thereof include polyethylene glutaric acid terephthalic acid copolymer, polybutylene daltaric acid terephthalic acid copolymer, and polybutylene succinic acid adipate phthalic acid copolymer.

 [0030] The weight average molecular weight of the aliphatic polyester is preferably in the range of 20,000 to 500,000, and more preferably in the range of 50,000 to 250,000. If the molecular weight is less than 20,000, practical properties such as mechanical strength and impact strength cannot be sufficiently improved, and if the molecular weight exceeds 500,000, the moldability may be poor.

 [0031] Among these thermoplastic polyesters, from the viewpoints of stretch processability, shrinkage properties, and optical properties, preferred are copolymerized aromatic polyesters and polylactic acid-based resins. Among them, the crystallinity as a raw material ( (Measured by wide-angle X-ray diffraction method) is preferably 30% or less, more preferably 20% or less, further preferably 10% or less, further preferably 5% or less, and particularly preferably substantially amorphous. Substantially amorphous ones are also preferable in that they can extrude at a lower temperature than the best in the above-mentioned stretch processability, 'shrinkage characteristics' and optical characteristics.

[0032] Examples of such low-crystalline or substantially amorphous materials include those obtained by copolymerizing isophthalic acid in addition to terephthalic acid to an acid component, and alkylene glycol in addition to ethylene glycol as an alcohol component. It can be obtained by copolymerizing another alcohol component such as, for example, ethylene glycol as the main component, 40 mol% or less of 1,4-cyclohexanedimethanol as the alcohol component, and terephthalic acid as the acid component. And the like. In that case, more preferred ratio of Cyclohexanedicarboxylic methanol as the alcohol component to ethylene glycol and 1, 4 Shikuro is 1, 4 Kisanji methanol to Shikuro force 0-40 mole _^0/0, more preferably 25 to 36 mole _^0/0 EastarPETG6763 copolyester (trade name) and Embrace copolyester (trade name) manufactured by Eastman Chemical Japan Co., Ltd. are examples of such amorphous aromatic polyesters. Examples of the non-crystallizable non-crystalline PET include E-01-01-3 (trade name) of non-crystalline PET for extrusion manufactured by Kanebo Gosen Co., Ltd.

[0033] In addition, from the same viewpoint, the polylactic acid-based resin preferably has a D-lactic acid unit content of 3% to 9%. It is preferably 7%, more preferably 4% to 96%, most preferably 10% to 90%.

[0034] As the thermoplastic polyurethane (TPU) used in the present invention, a polyadduct of a polyol and an isocyanate can be used. As the polyol, a polyether polyol such as polypropylene glycol, polytetramethylene ether glycol, or the like, a polyester polyol such as an adipate-based polyol, a polyproprolataton-based polyol or a polycarbonate polyol, or a polybutadiene polyol, an acrylic polyol, or the like is used. be able to. These may be used alone or in combination of two or more. Further, as the isocyanate, diphenolemethanediisocyanate, paraphenylene diisocyanate, diazine diisocyanate, or the like can be used. These may be used alone or in combination of two or more. Further, a diol or triol or the like can be used as a crosslinking chain extender. The melt viscosity can be adjusted by using a crosslinking chain extender.

 [0035] It is preferable that the TPU is an elastomer because of its drawability. Specifically, Kuraray U (trade name) and TU polymer (trade name) manufactured by Kuraray Co., Ltd., Miractran (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd., Rezamin manufactured by Dainichi Seirido Kogyo Co., Ltd. P (trade name) and Esteon (trade name) manufactured by NOVEON. The behavior and melting behavior of the elastomer differ depending on the content of the isocyanate component. When the content of the isocyanate component is represented by the nitrogen content, the nitrogen content in the TPU is preferably 1 to 7% by weight, more preferably 3 to 5% by weight. If the content is less than 1% by weight, the melt viscosity is too small to obtain a sufficient viscosity, and if the nitrogen content exceeds 7% by weight, the melt viscosity becomes too large, which hinders extrudability and stretchability. This is because there is a case where it is exerted.

[0036] Of the resin composition constituting layer A of the present invention, the TPU preferably has a power of 5 to 60% by weight, more preferably 15 to 50% by weight, most preferably 20 to 50% by weight. 40% by weight.割 合 Percentage of the resin composition Within this range, the adhesiveness with the layer B is sufficiently exhibited, and the optical properties are maintained without zigzag whitening even after sufficient heat shrinkage under a wide range of shrinkage conditions. An excellent heat-shrinkable film can be provided, and a shrinkable product having good optical properties can be obtained while satisfying required characteristics such as strength and barrier properties. If the TPU is less than 5%, the adhesiveness to the layer B becomes weak, and zigzag whitening may occur depending on the heat shrinkage conditions. On the other hand, if the TPU exceeds 60%, extrusion processability and stretch processability may become difficult. [0037] In the present invention, a second layer (hereinafter, referred to as a layer B) mainly composed of a second polymer whose main repeating unit substantially has a halogen or hydrogen bond is also required. The resin constituting the layer B has a strong polarity due to its structure, and the resin is more strongly agglomerated after stretching, and is indispensable for improving the strength and developing noria. Here, “substantially has a halogen or has a hydrogen bond” means that the main repeating unit has a halogen or forms a hydrogen bond among the repeating units constituting the polymer, and is chemically treated. In this case, only the terminal or a part of the molecular chain (less than 50 mol% in the repeating unit) is provided with a halogen or a chemical group constituting a hydrogen bond. It is not included in the present invention. Further, “mainly a polymer having a halogen or a hydrogen bond” means that a polymer having substantially a halogen or a hydrogen bond is contained in Layer B in an amount of 50% by weight or more. means.

 The second polymer in which the main repeating unit substantially has a halogen or hydrogen bond is (a) a polyamide, (b) an ethylene-bulcohol copolymer, (c) a poly (vinylidene chloride), or , (D) a polar group-containing polyolefin and any one of (a) to (c), preferably a mixture capable of forming a strong force. Hereinafter, the second polymer will be described in more detail.

[0038] Examples of the resin in which the repeating unit substantially has a halogen include a polychloride-based vinylidene polymer, a polychlorinated vinyl-based polymer, a polyvinylidene fluoride-based polymer, and a polyvinyl fluoride. Among these, the polychlorinated bilidene polymer is preferably applied because it has excellent gas barrier properties. The Shioi匕Biyuriden polymer, Shioi匕Biyuriden and 50 molar _^0/0 following Shioi匕Bulle, methyl Atari rate include copolymers榭脂of butyl Atari rates.

[0039] On the other hand, a hydrogen bond is a bond in which atoms X and Y (nitrogen, oxygen, phosphorus, sulfur, sulfur, halogen, etc.), which are more electronegative than a hydrogen atom, are weakly bound via hydrogen. To tell. Examples of the polymer in which the repeating unit substantially has a hydrogen bond include PA, EVOH, polybutyl alcohol (hereinafter, referred to as PVA), cellulose, and derivatives thereof. Among them, high-strength PA and EVOH having gas barrier properties are suitably used in the present invention. When hydrophilicity is particularly required for the film, PVA is also preferably used. [0040] EVOH used in the present invention has an ethylene copolymerization ratio of less than 50%. From the viewpoint of gas nobility, those having ethylene of 45 mol% or less are preferred. Further, the ethylene copolymerization ratio is preferably at least 25 mol% from the viewpoint of balance between moldability and gas nobility.

 As the PVA used in the present invention, a thermoplastic PVA whose thermoplasticity is enhanced by graft modification in addition to the adjustment of the degree of degradation is preferably used. Specifically, low saponification degree PVA, Ecomaty AX (trade name) (product of Nippon Kasei Chemical Co., Ltd.) (graft of polyoxyalkylene onto butyl alcohol'aryl alcohol copolymer), Kuraray Co., Ltd. Of the Kuraray Povar (trade name) made of clay, the CP series (trade name) for hot melt molding, and the other Kiserene (trade name) made of Kurarene clay (CP polymer) (trade name) for melt molding Have been

[0042] PAs used in the present invention include aliphatic polyamides and semi-aromatic polyamides. Specific examples include polycapramidamide (nylon 6), polyhexamethylene adipamide (nylon 66), polycapramidamide Z polyhexamethyleneazinamide copolymer (nylon 6Z66), and polytetramethylene adipamide. (Nylon 46), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polypromamide Z polyhexamethylene azinamide Z polydodecaneamide copolymer (nylon 6Z66Z12), Polyhexamethylene terephthalamide Z polyforce proamide copolymer (nylon 6TZ6), polyhexamethylene azinamide Z polyhexamethylene terephthalamide copolymer (nylon 66Z6T), polyhexamethylene azinamide / polyhexamethylene isophthalamide Copolymer (nylon 6 6/61), polyhexamethylene Adipamide Z polyhexamethylene terephthalamide Z polyhexamethylene isophthalamide copolymer (nylon 66Z6TZ6I), polyhexamethylene terephthalamide Z polyhexamethylene isophthalamide copolymer (nylon 6TZ6I), polyhexamethylene terephthalamide Z poly (2- Methylpentamethylene) terephthalamide copolymer (nylon 6TZM5T), polyhexamethylene terephthalamide Z polyhexamethylene sebacamide Z polyforce proamide copolymer (nylon 6TZ610Z6), polyhexamethylene terephthalamide Z polydodecaneamide Z polyhexamethylene azi Pamide copolymer (nylon 6TZ12Z66), polyhexamethylene terephthalamide Z polydodecaneamide Z Rihexamethylene isophthalamide copolymer (nylon 6TZ12Z6I), polyxylylene diphthalamide (nylon XD6), polyhexamethylene terephthalamide Z polyhexamethylene isophthalamide (nylon 6TZ6I), and mixtures or copolymers thereof. It is. Among the above PAs, nylon 6/66 having a melting point of 200 ° C. or less is preferable from the viewpoint of cost, extrudability, and stretchability. In order to further improve the stretchability, it is preferable to mix 20 to 100% of nylon 6Z66 with 0 to 80% by weight of PA having a melting point of 180 ° C. or lower or low crystalline or amorphous PA. Examples of PA having a melting point of 180 ° C or lower include nylon 6-69, nylon 6-12, nylon 6-66-610, nylon 6-66-12, nylon 6-66-610-12, etc. sex is, the copolymer with isophthalic acid component 40 to 98 mol% of as PA amorphous aliphatic Jiamin Z isophthalic acid and aliphatic Jiamin Z terephthalic acid, also terephthalic acid component 2-60 mole _^0/0 force are those also comprising an acid component and hexamethylene di § Min 50-99 molar _^0/0 and optionally bis (P-aminocyclohexyl) methane 0-50 mole _^0/0 force, these nylon 61- 6T As amorphous nylons, sealer PA 3426 (trade name) manufactured by Mitsui Dupont Co., Ltd., Daripoli-I G21 (trade name) manufactured by EMS Co., Ltd., Novamit X21 (trade name) manufactured by Mitsubishi Engineering Plastics Co., Ltd. ) And are particularly preferably used; Masui 添力 卩量 is 10-40%, and most preferably 20-30%. Of these, when the amorphous material has the most preferred crystallinity, the PA does not have a crystallization peak temperature within 15 ° C near the stretching temperature, more preferably within 20 ° C. Preferred over sexual perspective ヽ. When it is necessary to impart gas nori properties to the PA layer, nylon XD (for example, nylon MXD6 (trade name) manufactured by Mitsubishi Gasani Corporation) is preferably used mainly or as a mixture.

It is preferable to mix a polar group-containing polyolefin into the layer B of the present invention because the adhesiveness with the layer A can be further improved. Examples of the polar group-containing polyolefin include an ethylene-vinyl ester copolymer, an ethylene unsaturated carboxylic acid copolymer, an ionomer of an ethylene unsaturated carboxylic acid copolymer, and an ethylene unsaturated carboxylic acid ester copolymer. Here, examples of the unsaturated carboxylic acid component include acrylic acid, methacrylic acid, fumaric acid, monomethyl maleate, monoethyl maleate, and maleic anhydride. [0044] Specifically, ethylene vinyl acetate copolymer (EVA) as an ethylene vinyl ester copolymer, ethylene methyl methacrylate copolymer (EMMA) as an ethylene unsaturated carboxylic acid ester copolymer, ethylene methyl acrylate Copolymer (EMA), ethylene ethyl acrylate copolymer (EEA), ethylene unsaturated carboxylic acid copolymer ethylene-methacrylic acid copolymer (EMAA), ethylene acrylic acid copolymer (EAA), ethylene copolymer A modified olefin polymer obtained by modifying a polymer with maleic anhydride or glycidyl (meth) acrylate is exemplified.

[0045] The ionomer used in the present invention is such that at least a part of the carboxyl groups of an ethylene / unsaturated carboxylic acid random copolymer such as an ethylene Z (meth) acrylic acid copolymer contains zinc, sodium, magnesium, and lithium. 0.1 to 90% neutralized by metal ions such as potassium and potassium. In the ionomer, the ethylene component is 75 to 95% by weight, especially 80 to 90% by weight, and the unsaturated carboxylic acid component, that is, the unsaturated carboxylic acid and unsaturated carboxylic acid salt component is 5 to 25% by weight, particularly 10 to 20% by weight. % And other unsaturated monomer components are preferably copolymerized at a ratio of 0 to 25% by weight, particularly 0 to 20% by weight. Further, two or more different unsaturated carboxylic acid components may be used as long as the total satisfies the above requirements. The ethylene 'unsaturated carboxylic acid random copolymer serving as the base polymer of the ionomer can be obtained by random copolymerization of each polymerization component under high temperature and high pressure. Other unsaturated monomer components include, for example, acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, and n-butyl (meth) acrylate ゃ methacrylic acid. An unsaturated ester such as an ester or a butyl acetate may be copolymerized at about S _{0 to} 25% by weight.

[0046] Among them, a zinc ionomer is mentioned as an ionomer that can be particularly preferably used for PA or EVOH. Zinc ionomers are preferred because they form a coordination bond to the amino group and have a high affinity for PA. Examples of this include Himilan AM7315 (trade name) and Himilan 1706 (trade name) manufactured by Mitsui Dupont Polychemical Co., Ltd. In addition, some of them have enhanced affinity for EVOH due to their characteristics and amino groups, and these are preferably used for EVOH. This includes, for example, Himilan AM79261 (trade name) manufactured by Mitsui Dupont Polychemical Co., Ltd. The Further, sodium ionomer has a strong electrostatic interaction with a hydroxyl group, and thus is preferably used for PA and EVOH. As this, for example, Himilan S 1856 (trade name) manufactured by Mitsui Dupont Polychemical Co., Ltd. and the like can be mentioned.

 [0047] The effect of the present invention is particularly apparent in a film having a high shrinkage ratio, where the heat shrinkage ratio is 120 ° C in dry heat in the vertical direction (the line direction during film formation is defined as the vertical direction, MD) or transverse direction (transverse direction to the line direction at the time of film formation, hereinafter referred to as TD) is 30% or more, and the other is 20% or more. is there. Generally, the upper limit of the shrinkage of a heat-shrinkable film is 90%, and often 80%. In order to obtain such a high heat shrinkage, the crystallinity of the thermoplastic polyester used for the layer A is preferably 30% or less, more preferably 20% or less, still more preferably 10% or less, and further preferably 5% or less. Hereinafter, it is particularly preferably substantially amorphous. The low crystallinity resin facilitates a high stretching ratio, and achieves a high shrinkage ratio in a practical shrinkage temperature region above its glass transition point without waiting for the melting of the crystal component.

[0048] Regarding the arrangement of the layer A and the layer B in the present invention, the effect can be exhibited in any of AZB, AE / A, B / A / B, A / 6 ZAZB and the like. The heat-shrinkable film of the present invention is preferably composed of a laminate in which a layer B, a layer A, and a layer B are directly laminated in this order (hereinafter, referred to as a layer BZ layer AZ layer B). In particular, when two or more types of layers B, for example, a layer B in which the second polymer is a polyamide and a layer B containing a resin having gas nolia properties, and a layer A, have three or more layers, the heat of the present invention is used. It is preferable that the shrinkable film also has a laminate strength in which the layer B, the layer A in which the second polymer is polyamide, and the layer B containing the resin having gas nolia property are directly laminated in this order. In addition, examples of the resin having gas nolia property include a resin containing EVOH. Layer B has the disadvantage that the heat shrinkage of the film is low due to strong aggregation after stretching with strong polarity, or zigzag whitening is likely to occur due to the low heat shrinkage of the specific layer. Are arranged separately on both sides of each layer, and the adjacent layer A directly and efficiently acts on each layer B to compensate. By adopting such a layer arrangement, a film having both pinhole resistance and gas nolia property can be obtained without causing delamination or zigzag whitening. In this specification, “adjacent” and “directly laminated” have the same meaning. [0049] Further, in the present invention, an oxygen-absorbing layer having an oxygen-absorbing function can be preferably provided in the gas-barrier resin layer or a layer on the food side therefrom. Oxygen-free resin has an oxygen permeability (cc '25 .4 micron Zm ² '24hr'atm, 25 ° C, ORH%) of 50 or less, preferably 10 or less, more preferably 2 or less, most preferably Is less than or equal to 1. Specific examples include EVOH, vinylidene chloride-based resin, nylon XD, polydalicholic acid, polyglycolic acid-lactic acid copolymer, etc., and from the viewpoint of barrier properties, EVOH, vinylidene chloride-based resin and polydalicholate are preferred. EVOH is more preferred from the viewpoint of coextrudability.

 [0050] As the constituent material of the oxygen absorbing layer, a method of mixing or coating an inorganic or organic substance imparting a deoxygenating function to a resin, or a method in which the resin itself has an oxygen absorbing ability can be used. . Examples of the inorganic substance and the organic substance include iron powder, aluminum powder, ascorbic acid, activated carbon, hindered phenol, polyphenol, and unsaturated fats and oils. Resins having an oxygen-absorbing ability include those having a double bond in the molecule and those containing tertiary hydrogen, and are capable of reacting with a transition metal such as cobalt-silver or a salt or oxide thereof in the presence of an appropriate catalyst. Automatic oxidation is promoted when used together. Among them, those having a double bond and having a low molecular weight due to acid-digestion and having a low molecular weight are not likely to occur, for example, those having a double bond in the cyclic structure of the side chain (for example, described in JP-A-2003-521552). Ethylene Z methyl acrylate / cyclohexene monomethyl phthalate copolymer) is preferably used.

 [0051] In the present invention, a seal layer is further preferably provided.

 [0052] The resin that mainly constitutes the seal layer is not particularly limited as long as it is a thermoplastic resin that can be heat-sealed, but a polyolefin-based resin is preferably used from the viewpoint of the sealing temperature. And polystyrene-based resins.

 [0053] In the present invention, the polyolefin resin used for the seal layer is specifically shown below.

[0054] The ethylene-based polymer is a single-site catalyst, or is polymerized by a multi-site catalyst, and includes ordinary low-density, medium-density, high-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene. Includes copolymers with α-olefins having 3 to 18 carbon atoms, such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-otaten. [0055] As the propylene-based polymer, a copolymer of propylene and another oc-olefin is preferred. In particular, a copolymer of propylene and another α-olefin obtained with a meta-mouth catalyst has a melting point close to that of a polyethylene resin and is preferably used. Specific examples thereof include Wintech (trade name, manufactured by Nippon Polychem Co., Ltd.).

[0056] Polyolefins containing a polar group may also be mentioned, such as an olefin butyl ester copolymer, an olefin unsaturated carboxylic acid copolymer, an ionomer of an olefin unsaturated carboxylic acid copolymer, and an olefin unsaturated carboxylic acid ester copolymer. No. Here, examples of the unsaturated carboxylic acid component include acrylic acid, methacrylic acid, fumaric acid, monomethyl maleate, monoethyl maleate, and maleic anhydride. Specifically, ethylene vinyl acetate copolymer (EVA) is used as an ethylene vinyl ester copolymer, ethylene-methyl methacrylate copolymer (EMMA) is used as an ethylene unsaturated carboxylic acid ester copolymer, and ethylene methyl acrylate copolymer is used. Polymer (EMA), ethylene ethyl acrylate copolymer (EEA), ethylene unsaturated carboxylic acid copolymer ethylene-methacrylic acid copolymer (EMAA), ethylene acrylic acid copolymer (EAA), ethylene copolymer Examples thereof include modified olefin polymers obtained by graft modification of a copolymer or a propylene copolymer with maleic anhydride, glycidyl (meth) acrylate, or the like. Further, at least a part of the carboxyl groups of the ethylene / unsaturated carboxylic acid random copolymer such as ethylene Z (meth) acrylic acid copolymer called ionomer is formed by metal ions such as zinc, sodium, magnesium, lithium and potassium. , 0.1 to 90% neutralized. In the above ionomer, the ethylene component is 75 to 95% by weight, especially 80 to 90% by weight, and the unsaturated carboxylic acid component, that is, the unsaturated carboxylic acid and unsaturated carboxylic acid salt component is 5 to 25% by weight, especially 10 to 20% by weight. %, And other unsaturated monomer components are preferably copolymerized at a ratio of 0 to 25% by weight, particularly 0 to 20% by weight. Further, two or more different unsaturated carboxylic acid components may be used as long as the total sum satisfies the above requirements. The random copolymer of ethylene and unsaturated carboxylic acid as the base polymer of the ionomer can be obtained by random copolymerization of each polymerization component under high temperature and high pressure. Other unsaturated monomer components include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, and n-butyl (meth) acrylate. Acrylates such as tyl ゃ methacrylates or unsaturated ester such as vinyl acetate can be copolymerized in an amount of about ^ 25% by weight.

In the present invention, the polystyrene resin used for the seal layer includes a homopolymer or copolymer of at least one styrene monomer selected from the group consisting of styrene and a derivative thereof, or And styrene and its derivatives. A group of at least one selected styrene-based monomer and another vinyl-based monomer. In the case of a copolymer, it may be a random copolymer or a block copolymer. Polystyrene resin must be extrudable and stretchable. Examples of the styrene-based monomer include styrene, α-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, halogenated styrene, t-butylstyrene, butyltoluene, bulxylene, and dimethyl Examples include benzene. Of these, styrene, α-methylstyrene and p-methylstyrene are preferred, and styrene and a-methylstyrene are particularly preferred. The styrene monomer is usually 25 to: LOO% by weight, preferably 50 to: LOO% by weight, and more preferably 55 to 98% by weight as a percentage of the total amount of the monomers used as the raw material for the polymerization of the polystyrene resin. % Is desirable.

[0058] The other vinyl monomer copolymerizable with the styrene monomer is not particularly limited as long as it is a vinyl compound copolymerizable with the styrene monomer. As the other vinyl monomer, ethylene, Orefin such as propylene; butadiene, Polje emissions such as isoprene; acrylonitrile, methacrylonitrile Tali, acrylonitrile-based monomers, such as _a black hole acrylonitrile; Mechirumetatari (Meth) acrylic acid alkyl ester monomers such as acrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and n-butyl acrylate; n-phenylmaleimide, n-methylphenylmaleimide, and n-cyclohexane Maleimide monomers such as xylmaleimide and n-ethylmaleimide; and unsaturated carboxylic acid derivatives such as maleic anhydride, acrylic acid and methacrylic acid. These monomers can be used alone or in combination of two or more. These are listed, for example, as Asaflex (trade name) manufactured by Asahi Kasei Corporation! /

[0059] A rubbery polymer may be mixed with the polystyrene resin. Examples of the rubbery polymer include polybutadiene, isoprene, butadiene copolymer, and styrene-butadiene copolymer. And acrylonitrile-butadiene copolymer, ethylene-propylene copolymer, and ethylene-propylene-gen copolymer. These are, for example, Tuftec (trade name) of Asahi Kasei Corporation, Dynalon (trade name) of JSR Corporation, Clayton (trade name) of shell, Hibler (trade name) of Kuraray Co., Ltd., Septon (Product name) and the like. Polystyrene resin can be used alone or in combination of two or more.

 [0060] The following aliphatic polyesters can also be used for the heat seal layer.

 [0061] For example, aliphatic polyesters polycondensed with an aliphatic dicarboxylic acid and an aliphatic diol as main components include fatty acids such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecane diacid. Aromatic carboxylic acids such as aromatic carboxylic acid, terephthalic acid, and isophthalic acid; and neutral carboxylic acids such as ethylene glycol, 1,3-propion glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol One or more selected polycondensations are mentioned as examples.

 [0062] Aliphatic polyesters obtained by ring-opening polymerization of cyclic ratatatons include ε-force prolatatatone, δ

 Examples include ring-opened polymers selected from one or more cyclic monomers such as valerolatatone and / 3-methyl- valerataton.

 Examples of the synthetic aliphatic polyester include copolymers of succinic anhydride, a cyclic acid anhydride such as ethylene oxide and propylene oxide, and oxosilanes.

 [0064] The weight average molecular weight of the aliphatic polyester is preferably in the range of 20,000 to 500,000, and more preferably in the range of 50,000 to 250,000. If the molecular weight is less than 20,000, practical properties such as mechanical strength and impact strength cannot be sufficiently improved, and if the molecular weight exceeds 500,000, the moldability may be poor.

[0065] The outer surface layer of the present invention, that is, the layer on the side that does not come into contact with the contents, of the surface layer is not particularly limited, and may be any of a seal layer, a polyester layer, a polyamide layer, and a non-ionic resin layer. It may be. When printability is required, the polar group-containing polyolefin, polyester resin and polyamide resin exemplified above can be mainly used. When abrasion resistance of the surface is required, polyamide resin can be mainly used. When the outer surface layer is used as a seal layer, the same resin as the seal layer can be mainly used. Outer surface When polyolefin resin is used, the glass transition point is below room temperature when additives are mixed, so that it can be bleed out appropriately and various surface characteristics can be adjusted according to the application. Further, in the case of polyethylene resin, crosslinking can prevent fusion to a seal bar at the time of sealing, and can impart V, so-called sealing heat resistance.

[0066] When the heat-shrinkable film of the present invention is subjected to a gas-sealing heat-sealing process that requires a heat-sealing layer on only one side, the sealing surface layer and the non-sealing surface layer can be cross-linked with an electron beam such as polyethylene resin. In the case of resin, the sealing surface layer and the non-sealing surface layer preferably satisfy the following formulas.

 10 ≤ G (unsealed surface) ≤ 70 (I)

 0≤G (seal surface) ≤30 (II)

 G (non-seal surface) ≥ 1.2 X G (seal surface) (III)

 Here, G (non-sealed surface layer) and G (sealed surface layer) indicate the gel fraction (% by weight) due to cross-linking of the unsealed surface layer and the sealed surface layer, respectively.

[0067] In this case, the non-seal surface layer has a role as a heat-resistant layer at the time of heat sealing with the joint. In addition, it also has the effect of improving the stretchability of a film containing a PA layer and a gasoline resin layer, which are difficult to stretch. The gel fraction G (non-sealed surface layer) of the unsealed surface layer is preferably from 10% by weight to 70% by weight. When the gel fraction is 10% by weight or more, the effect as a heat-resistant layer and the effect of improving stretchability tend to increase, and when the gel fraction is 70% by weight or less, the effect as a heat-resistant layer and stretchability tend to be good. On the other hand, the gel fraction G (seal surface layer) of the heat seal surface layer is preferably 30% by weight or less. It is preferably at most 20% by weight, more preferably at most 10% by weight. Most preferably, it is substantially uncrosslinked and has a gel fraction of 0%. If the gel fraction exceeds 30% by weight, sealing tends to occur and sealing strength tends to be insufficient.

[0068] Further, the relationship between the gel fraction due to crosslinking of the non-seal surface layer and the seal surface layer is preferably G (non-seal surface layer) ≥ 1.2 XG (seal surface layer). In the case of G (non-sealing surface layer) <1.2 XG (sealing surface layer), heat sealing is performed in such a way that the effect of the heat-resistant layer of the non-sealing surface layer, which is the side to which the heat is applied for sealing, is no longer with the sealing layer. The longer the time required, the more stress or defective packaging becomes noticeable. [0069] Regardless of the presence or absence of cross-linking, the thickness of the non-seal surface layer is not particularly limited, and is satisfactory in many cases even if it is as thin as 1 micron. The thickness of the seal layer is airtight especially at the time of high-speed sealing. If a seal is required, it is preferably at least 5 microns, more preferably at least 8 microns, and most preferably at least 10 microns.

 [0070] In the present invention, the force applied directly adjacent to the front layer A and the layer B without intervening any other layer between the front layer A and the layer B may be adhered if necessary in combination with the other layers. Layers can be provided. As the adhesive layer, the above-mentioned polar group-containing polyolefin can be used.

[0071] As long as the effects of the present invention are not impaired, a known additive such as an acid inhibitor (for example, 2,2 thiobis (4 methyl-6 t Lufenol, etc.), light stabilizers (for example, 2-hydroxy-4-otatobenzobenzophenone, etc.), processing aids (for example, calcium stearate, etc.), lubricants (Examples include L-acid amide, oleic acid amide, stearic acid amide, behenic acid amide, etc.), anti-blocking agents (Examples include natural silica, synthetic silica, or average particle size (Coulter 'Counter one method) m or less, preferably 1 to 4 m of PMMA beads and the like), anti-fogging agents (diglycerin monolaurate and diglycerin monoolate, for example) Diglycerin distearate, polyoxyalkylene ether, polyoxyethylene alkylene ester, etc.), antistatic agent (polyglycerin ester, etc., for example), and other sealability improving functions. Fats and additives (for example, alicyclic saturated hydrocarbon resins (Arakawa Chemical Industries, Ltd., Alcon (trade name) etc.)), hydrogenated terpene resins (Yasuhara Chemical Co., Ltd., Clearon (trade name), Terpene resin (Yashara Chemical Co., Ltd., YS resin (trade name), etc.) Liquid paraffin (Matsumura Petroleum Institute Co., Ltd., Moresco White (trade name), etc.), rosin Rosin ester, coumarone indene resin, etc.), etc. Also, known surface treatments such as corona discharge treatment, fire treatment, and Irradiation treatment including ion plasma or ion etching treatment can be performed.

[0072] An example of the method for producing the heat shrinkable film of the present invention will be described. First, the resin that constitutes each layer Are melted in respective extruders, co-extruded with a multilayer die, and quenched and solidified to obtain a raw multilayer film. As the extrusion method, a multilayer τ die method, a multilayer circuit method, or the like can be used, but the latter is preferable. The raw multilayer film thus obtained is stretched by heating to 50 to 200 ° C. Examples of the stretching method include a roll stretching method, a tenter stretching method, an inflation (including a double bubble method), and a method of forming a film by biaxial stretching is preferable. The stretching is performed at least 1 to 10 times in one direction and 1 to 50 times in area ratio, and the stretching ratio is appropriately selected depending on the heat shrinkage required according to the application. If stretching is insufficient, "shrinkage remaining" due to insufficient shrinkage may occur, and packaging may not be beautiful. In order to obtain a film having a high shrinkage ratio, a stretching ratio of 4 times or more in each of the longitudinal direction and the horizontal direction is preferred, and more preferably, a stretching ratio of one or more is 4 or more and the other is 4.5 or more. The area magnification is preferably 16 times or more, more preferably 18 times or more, and most preferably 20 times or more.

 [0073] Further, if necessary, post-processing, for example, heat setting for dimensional stability, or lamination with various films may be performed.

[0074] In particular, heat setting is performed when it is necessary to reduce the contraction force. In many cases, the processing temperature is selected from 60 ° C to 100 ° C. The temperature is preferably lower than the melting point of the resin in the surface layer in order to prevent fusion of the film, which is preferably treated at a temperature higher than the glass transition point of the polyamide for stress relaxation. Further, in order to suppress the reduction in shrinkage, it is preferable to perform the treatment at a temperature lower than the glass transition point of the polyester resin. In the case of tray packaging described below, it is particularly effective to reduce the shrinkage force in the horizontal direction. In this case, the dimensional relaxation of 0 to 30% in the horizontal direction is positively taken during heat setting. In this case, the dimensional relaxation rate in the vertical direction is selected from -20% to + 20%. In the case of tray packaging, it is possible to achieve both high shrinkage and low shrinkage by combining the above-described high stretching ratio and heat setting under specific conditions. The preferred heat shrinkage in this case is that at dry heat of 120 ° C, either MD or TD is 30% or more, the other is 20% or more, and more preferably both MD and TD are 30% or more, Most preferably, either MD or TD is 35% or more, and the other force is 30% or more. The preferred shrinkage stress is that the maximum stress (average value of MD and TD) when immersed in an oil bath at 120 ° C is 3.OMPa or less, more preferably 2.5MPa or less. And most preferably 2. OMPa or less.

[0075] The film of the present invention is preferably used so as to be thermally shrunk by dry heat treatment such as hot water or a shrink tunnel. For example, the heat-shrinkable film of the present invention is a method for covering the contents with a package, reducing the pressure inside the package to bring the package into close contact with the contents, and further heat shrinking the package. It is preferable to use it for the package used. This makes it possible to obtain a package that is tightly adhered to the contents. Another use is to use a horizontal pillow shrink packaging machine without adhering the film to the entire contents, put the contents on a tray, and obtain a heat shrinkable package in a shrink tunnel. Can be In particular, when the heat-shrinkable film of the present invention has gas-nolia property, it is preferable to use it for a gas replacement package. Above all, the air inside the package is replaced by inert gas, that is, nitrogen, carbon dioxide and a mixture thereof, and, if necessary, a gas obtained by mixing oxygen at a partial pressure of 20% or less or 21% or more. It is preferably used for a gas replacement package.

 [0076] The thickness of the packaging film of the present invention can be set according to the purpose, but when it is usually used for tray packaging, preferably 5 to 50 / ζπι, more preferably 15 to 40 / ζπι is used. When the film is not used and is used for packaging in which the film is in close contact with the contents, preferably 20 to: LOO m, more preferably 30 to 70 / ζπι.

 Example

 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not particularly limited to the examples. The measuring method and evaluation method in the examples are as follows.

 [0078] (1) Dry heat treatment

 30% vertical x 20% horizontal, that is, a 13cm x 12cm film sample is attached to a 10cm square frame, and placed in an air oven type thermostat set at a predetermined temperature (100 ° C or higher). Minutes. The same applies to the margin 20% horizontal X 30% vertical.

 The margin (X) is represented by the following equation.

Margin (%) = ιοοχ (length of film pasted on frame-frame length) Z frame length [0079] (2) Hot water treatment

 Margin 30% vertical x 20% horizontal, that is, a 13cm x 12cm film sample is attached to a 10cm square frame, placed in a hot water bath set to a specified temperature (95 ° C or less), and processed for 4 seconds did. The same was done for the margin of 20% width and 30% height.

[0080] (3) Interlayer adhesion

 Under the conditions of (1) or (2) above, the shrinkage temperature is 80 ° C to 160 ° C in 10 ° C increments. After checking the voids from the film surface for the presence of delamination at the time after the treatment, the cross section of the film was tipped with tweezers or hand as interlayer adhesion, and the peeling was smooth when trying to peel the entire surface. Was evaluated based on the following criteria. The evaluation was made with the worst result among the above conditions. If the heat shrinkage did not reach 30% on one side and 20% on the other, the sample was subjected to free shrinkage at that temperature and evaluated.

 AA: No delamination can be confirmed in the film. Complete peeling with tweezers is extremely difficult.

A: No delamination can be confirmed in the film. Although the whole surface can be peeled off with tweezers, it shows resistance.

 B: Delamination in the film can be partially confirmed, and the entire surface can be peeled by hand without using tweezers, showing a little resistance.

 C: A considerable part of the film is delaminated, and it can be easily peeled off by hand without using tweezers, showing almost no resistance.

[0081] (4) Zigzag whitening

 A 10 cm square film sample is placed in an air oven type constant temperature bath set at a predetermined temperature, treated for 30 minutes in a freely shrinking state, and then the film is taken out and visually observed for whitening. The cross section was observed to confirm whether or not the layer was bent, and evaluated based on the following criteria. The heat shrinkage was performed at 10 ° C intervals from 80 ° C to 160 ° C, and the evaluation was made with the worst result among the above conditions.

 AA: Almost no whitening of film and no bending of layer B!

A: Force with slight bending of layer B Little or no slight whitening, practically hindered, B: Bending of layer B is clearly observed, causing slight whitening, which may be a practical problem

C: Transparency is remarkably reduced due to whitening where layer B is severely bent.

(5) Heat Shrinkage

 A 10 cm square film sample is passed through a hot air shrink tunnel MODEL MS8441 (trade name, manufactured by K & U System Co., Ltd.) set at a temperature of 120 ° C while freely shrinking. The lateral shrinkage was determined and expressed as a percentage of the value divided by the original dimensions. The maximum wind speed at the center was 4.5 mZsec, and the passage time was 5 seconds.

(6) Crystallinity (Xc)

 The crystallinity is calculated from the heat of fusion (hereinafter, A H CiZg) by the DSC method. Set the sample for measurement (film) in a lOmg DSC device, hold at 10 ° C for 1 minute, then raise the temperature at 10 ° CZ, and use the endothermic peak derived from the resin to calculate the theoretical heat of fusion of the crystal H CiZg) The crystallinity is obtained from the following equation. In the case of crystallization during heating, the calorific value corresponding to the crystallization is subtracted from the crystal melting endotherm to determine the crystallinity before heating.

 Crystallinity (Xc,%) = 100 Χ Δ Η / Η

 In the case of a copolymer, Η of the homopolymer having the largest component is used as a numerical value. (4) Theoretical crystal fusion heat of fat is as follows.

 Thermoplastic polyester = 14 j / g

 The specific resin among the thermoplastic polyesters is determined as follows.

 Polylactic acid = 100jZg

 The crystallinity shown in the examples of the present invention is such that layer A is made of a mixture of a thermoplastic polyester and a thermoplastic polyurethane, but the thermoplastic polyurethane used in the examples of the present invention is substantially Since the heat of fusion can be regarded as zero, the heat of fusion obtained by measuring Layer A by DSC is divided by the mixing ratio of the thermoplastic polyester to obtain the heat of fusion of the thermoplastic polyester, and the crystal of the thermoplastic polyester is obtained. The degree of conversion was determined.

 [0085] (7) Gel fraction

It was determined by the following operation based on ASTM D2765. Weigh a sample of about 5 Omg from the specified place using a balance with an accuracy of 0.1 mg or less (Sg). Combine the sample with the patch on a 150 mesh SUS screen from which oil has been removed by immersing it in acetone for 24 hours beforehand, and weigh using the same balance (Wig). Wrap the sample in a voucher. The wrapped sample is kept in boiling para-xylene for 12 hours using a separable flask and a condenser. The sample wrapped in the voucher is dried using a vacuum drier to constant weight. Weigh the sample wrapped in the voucher with the same balance (W2g). Gel fraction (% by weight) = [1− (W1−W2) / S] × 100 The gel fraction is calculated by the following formula. For the sample, use the force obtained by peeling off the specific surface layer of the raw material, or if it is difficult to peel, cut out a section that occupies 80% or more of the thickness of the surface layer. Alternatively, in some cases, the predetermined layer may be formed as a single-layer film and used as a substitute. Regarding the stretched film, a film that has been heat-shrinked and returned to an original fabric can be used as a sample in the same manner as described above. When it is difficult to separate the surface layer and the inner layer of the film by fusion, it is assumed that the resin of the inner layer has poor adhesion to the surface layer and has the same density as possible. Irradiation experiments are repeated under the same conditions after preparing a raw material having a fat and a surface layer thickness, and after peeling, the gel fraction is measured, whereby the gel fraction of the film can be obtained. For non-crosslinked resins other than polyethylene that do not completely dissolve in boiling para-xylene and do not have a gel fraction of 0%, it is possible to select a solvent that is completely dissolved as appropriate and has a gel fraction of 0%.

 The resins used are described below.

 PES 1: Copolymerized aromatic amorphous polyester, EastarPETG6763 copolyester (Yeastman Chemical Japan Co., Ltd.)

 PES2: Copolymerized aromatic polyester, Bellpet IFG8L (Kanebo Synthetic Co., Ltd.) PES3: Aromatic polyester, EFG85A (Kanebo Synthetic Co., Ltd.)

 PES4: Polylactic acid, Latati # 5000 (manufactured by Shimadzu Corporation)

 PES5: Polylactic acid (amorphous), Latati # 9800 (manufactured by Shimadzu Corporation)

 PES6: Polybutylene succinate 'adipate, Pionole # 3001 (Showa Kogaku Co., Ltd.

PES7: Polybutylene succinate, Pionore # 1001 (manufactured by Showa Polymer Co., Ltd.) PES8: Copolymerized aromatic amorphous polyester, E-03 (manufactured by Kanebo Gosen Co., Ltd.) TPU1: Thermoplastic polyurethane, chlamiron U1195 (Kuraray Co., Ltd.) TPU2: Thermoplastic polyurethane, E598 (Nippon Polyurethane Industry Co., Ltd.)

 TPU3: Thermoplastic polyurethane, Esten 58277NAT021 (NOVEON) EVOH: Ethylene bulcohol-based polymer, XEP915 (Kuraray clay) Nyl: Polyamide-based polymer, Novamid 2430 (Mitsubishi Engineering Plastics)

 Ny2: Polyamide polymer, Novamid X21 (Mitsubishi Engineering Plastics Co., Ltd.)

 Ny3: polyamide polymer, UBE nylon 7028B (Ube Industries, Ltd.)

 PVDC1: Shiridani Biylidene Mono-Shidani Bulle copolymer (22 wt% of Shiridani Bulle component) PVDC2: Bilidene chloride-methyl acrylate copolymer (Methyl acrylate component 10 wt%)

 PVA: Polybutyl alcohol polymer, Ecomaty AX400TNG (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

 IR: Ionomer resin, Himilan AM79261 (Mitsui's DuPont Polychemical Co., Ltd.)

)

 EMA: Ethylene methyl acrylate copolymer, Lettuce Pearl RB3240 (manufactured by Nippon Polio Refin Co., Ltd.)

 EVA: Ethylene butyl acetate copolymer, Ultracene 635 (manufactured by Tosoichi Co., Ltd.) MPOl: Acid-modified polyolefin-based resin admer NF731 (Mitsui Chemicals, Inc.) MP02: Acid-modified polyethylene-based resin admer NF587 (manufactured by Mitsui Chemicals, Inc.) MP03: Acid-modified polyethylene-based resin Ubebond F3000 (manufactured by Ube Industries, Ltd.) 75% and linear low-density polyethylene, Umerit 2040F (manufactured by Ube Industries, Ltd.) 25% mixture MP04: 50% mixture of acid-modified polyethylene resin Ubebond F3000 (Ube Industries, Ltd.) and 50% low-density polyethylene, Suntech LD1920F (Asahi Kasei Chemicals Corporation)

 EEA: Ethylene ethyl acrylate copolymer, EVAFLEX703A (Mitsui DuPont Polychemical Co., Ltd.)

VL1: Linear low density polyethylene, Umerit 1520F (Ube Industries, Ltd.) VL2: Linear low-density polyethylene, Ultzettas 2022L (manufactured by Mitsui Chemicals, Inc.) VL3: Linear low-density polyethylene, affinity FP1140 (manufactured by Dow Chemical Japan Co., Ltd.)

 VL4: Linear low-density polyethylene, kernel KF270 (manufactured by Nippon Polyethylene Co., Ltd.) PP1: Polypropylene-based polymer, Wintech WFX4TA (manufactured by Nippon Polychem Co., Ltd.) PP2: Polypropylene-based polymer, sun-alomer PF621S (sun-alomer) Petroleum resin: alicyclic saturated hydrocarbon resin, Alcon PI 15 (manufactured by Arakawa Chemical Industry Co., Ltd.) [0087] In addition, in VL1-4 and PP2, polyoxy as an anti-fog agent was used. Ethylene (5 mol) lauryl ether = 0.6%, diglycerin laurate = 1.2%, and glycerin monoolate = 0.2% were added to each resin in advance.

[Example 1]

 Using a resin having the composition shown in Table A, two extruders were used to melt-extrude a two-layer tube from an annular die, and the tube was quenched using a water-cooled ring to obtain a 220 / zm thick tube. A stretch tube was obtained.

 The unstretched tube thus obtained is heated by an infra heater by heating the unstretched tube by radiation so that the temperature immediately before bubble formation (bubble neck portion) becomes the maximum temperature, and the temperature (this is referred to as the stretching temperature and the stretching temperature). While heating to 100 ° C, air is injected into the tubular parison to form a bubble, which is stretched 5.0 times in the vertical direction and 4.4 times in the horizontal direction. And cooled. Then, the stretched film was folded and slit to a predetermined width to obtain a shrink film having a thickness shown in Table A.

 Next, the shrink film was evaluated for interlayer adhesion and zigzag whitening described in the text. Table A shows the results. As a result, the resulting shrink film did not undergo delamination or zigzag whitening even after heat shrinkage, and was excellent in appearance and excellent in commercial value.

 [Comparative Example 1]

The same experiment as in Example 1 was repeated using the resin having the configuration shown in Table A. Next, the shrink film was evaluated for interlayer adhesion and zigzag whitening described in the text. Table A shows the results. As a result, the resulting shrink film is delaminated after heat shrink. And zigzag whitening were observed, and the product value was inferior. From this experiment, it is evident that in the present invention, the addition of thermoplastic polyurethane is essential to the thermoplastic polyester resin.

 [0092] [Comparative Example 2]

 The same experiment as in Example 1 was repeated using the resin having the configuration shown in Table A. However, in this case, an unstretched tube having a thickness of 330 / zm was obtained using three extruders. Next, the obtained shrink film was evaluated for interlayer adhesion and zigzag whitening described in the text. Table A shows the results. As a result, in particular, MPOl, which is used as an adhesive resin for non-shrinkable or low-shrinkable films to polyester resin, can achieve the delamination after heat shrinking of the obtained shrinkable film by hand. Zigzag whitening was observed, and the product value was inferior. This experiment shows that in the present invention, it is necessary that the thermoplastic polyester resin to which the thermoplastic polyurethane is added is adjacent to a resin having a hydrogen bond such as nylon.

[Example 2]

 The same experiment as in Comparative Example 2 was repeated using the resin having the configuration shown in Table A. However, the unstretched tube was 308 m thick and stretched 5.0 times vertically and 4.4 times horizontally. Next, the obtained shrink wrapping film was evaluated for interlayer adhesion and zigzag whitening described in the text. Table A shows the results. As a result, in the obtained shrink film, delamination did not occur even after the heat shrinkage, and the curve of the layer B was slightly caused, but was at a level that was not problematic in practical use.

[Example 3]

 The same experiment as in Example 2 was repeated using the resin having the configuration shown in Table A. Next, the shrink film was evaluated for interlayer adhesion and zigzag whitening described in the text. Table A shows the results. As a result, the obtained shrinkable film was excellent in appearance and excellent in commercial value without delamination or zigzag whitening even after heat shrinkage.

 [0095] Comparing Example 2 and Example 3, it can be seen that, when there are two layers B, it is preferable that the layer A is located between the two layers B for zigzag whitening.

 [Example 4]

The same experiment as in Example 2 was repeated using the resin having the configuration shown in Table A. But here Used seven extruders and set the thickness of the unstretched tube to 550 m. Next, the shrink film was evaluated for interlayer adhesion and zigzag whitening described in the text. Table A shows the results. As a result, the obtained shrinkable film was excellent in appearance and excellent in commercial value without delamination or zigzag whitening even after heat shrinkage.

 [Example 5-LO]

 The experiment was repeated, except that PES1 of Example 4 was changed from PES2 to PES7, and EEA was changed to MP02. However, the stretching temperature was set to 80 for PES4 to PES7. In Examples 5 to 10, the thickness of the unstretched tube was 360 m, and the stretching ratio was 4.1 times vertically and 3.5 times horizontally. In any case, the obtained shrink films did not cause delamination or zigzag whitening even after heat shrinkage, and were excellent in appearance and excellent in commercial value. The heats of fusion of Examples 4 to 10 were measured, the crystallinity of the thermoplastic polyester resin was determined, and the heat shrinkage at 120 ° C. was measured.

 [Examples 11 and 12]

 The experiment was repeated, except that TPU1 of Example 4 was replaced with TPU2 or TPU3. The resulting shrink film did not undergo delamination or zigzag whitening even after thermal shrinkage, and was excellent in appearance and excellent in commercial value.

 [Example 13]

 The same experiment as in Example 2 was repeated using the resin having the configuration shown in Table A. However, here, the thickness of the unstretched tube was 940 m, and the longitudinal and transverse stretching magnifications were 5.0 times and 4.0 times, respectively. The stretching temperature was 75 ° C. Next, the shrink film was evaluated for interlayer adhesion and zigzag whitening described in this document. Table A shows the results. As a result, the obtained shrinkable film was excellent in appearance and excellent in commercial value without delamination or zigzag whitening even after heat shrinkage.

 [0100] [Comparative Example 3]

The same experiment as in Example 13 was repeated, except that PES5 was set to 100% for the fourth layer of Example 13. Next, the shrink film was evaluated for interlayer adhesion and zigzag whitening described in the text. The resulting shrink film was inferior in commercial value due to delamination and zigzag whitening after heat shrinkage. [0101] After side-sealing the film of each of Example 13 and Comparative Example 3, 5 kg of pork was put in, vacuum-packed, and then immersed in hot water of 80 ° C for 4 seconds. When whitening was confirmed, Example 12 showed AA for interlayer adhesion and zigzag whitening, and Comparative Example 3 showed Zigzag whitening for interlayer adhesion C and B. .

 [0102] [Examples 14 to 15]

 The experiment was repeated by replacing PVDC1 of Example 12 with PVDC2 (Example 14) and PVDC1 (80%) + EVA (20%) (Example 15), and the obtained shrink film was delaminated even after heat shrinkage. No peeling or zigzag whitening occurred, and the product was excellent in appearance and excellent in commercial value.

 [0103] [Examples 16 to 17]

 The experiment was repeated with the mixing ratio of PES 1 and TPU1 of Example 4 changed as shown in Table A. It can be seen that the amount of TPU is a major factor in the results of delamination and zigzag whitening of the obtained shrink film after heat shrinkage.

 [Examples 18 to 20]

 The experiment was repeated in the same manner as in Example 4 with the layer configuration shown in Table A. The obtained shrink film did not undergo delamination or zigzag whitening even after heat shrinkage, and was excellent in appearance and excellent in commercial value.

 [Example 21]

 An unstretched tube (with a thickness of 450 μm) obtained in the same manner as in Example 4 with the same layer configuration as in Example 18 was accelerated by an electron beam irradiation device (trade name, CUR ETRON, manufactured by NHV Corporation) Irradiation was performed at a voltage of 150 keV and an irradiation dose of 90 kGy. Because of the tube-shaped raw material, irradiation was performed from both sides of the folded tube so that the irradiation dose was 90 kGy on the entire outer peripheral surface of the tube.

[0106] Next, the unstretched tube is heated by irradiation with an infra-heater to adjust the temperature immediately before bubble formation (bubble neck portion) to the maximum temperature, and while heating the temperature to 100 ° C, the tubular parison is heated. Air was injected into the inside to form bubbles, and the bubbles were stretched 4.6 times in both the vertical and horizontal directions, and the air bubbles were cooled by applying cooling air to the bubbles. Then, after the stretched film is folded, it is heated again so that the film temperature becomes 78 ° C and heat-set so that the dimensional relaxation rate becomes 15% in the horizontal direction. Then, a shrink film having the same thickness as in Example 18 was obtained. The gel fraction of boiling paraxylene according to ASTM-D2765 was 15% on average for the first and second layers, and 0% for the sixth and seventh layers. The resulting shrink film did not undergo delamination or zigzag whitening even after heat shrinkage, and was excellent in appearance and excellent in commercial value. The heat shrinkage of this film at 120 ° C was 35Z31% in the vertical and horizontal directions. The maximum value of shrinkage stress due to immersion in an oil bath at 120 ° C was 1.9 / 1.5MPa in the vertical and horizontal directions.

 [Example 22]

 The same experiment as in Example 21 was repeated using six extruders with the layer configuration shown in Table A. The resulting shrink film was excellent in appearance and excellent in commercial value without delamination or zigzag whitening even after heat shrinkage.

 [Example 23]

 The same experiment as in Example 1 was repeated using five extruders with the layer configuration shown in Table A. The resulting shrink film was excellent in appearance and excellent in commercial value without delamination or zigzag whitening even after heat shrinkage.

 [Example 24]

 The same experiment as in Example 1 was repeated using four extruders with the layer configuration shown in Table A. The resulting shrink film was excellent in appearance and excellent in commercial value without delamination or zigzag whitening even after heat shrinkage. The heat shrinkage of this film at 120 ° C. was 38Z44% in the vertical and horizontal directions.

 [Comparative Example 4]

 The same experiment as in Example 1 was repeated using four extruders with the layer configuration shown in Table A. The obtained shrink film was the same as Comparative Example 2, and delamination and zigzag whitening occurred after heat shrinkage, and the commercial value was poor. The heat shrinkage of this film at 120 ° C. was 53Z55% in the vertical and horizontal directions.

[0111] Solid tray Q-15-15 (trade name) (manufactured by Chuo Pearl Co., Ltd.) was manufactured using a gas pack shrink wrapping machine CFP-3000 (trade name) (manufactured by Ibaraki Seiki Co., Ltd.). Was wrapped with the film of Example 21 and Example 24 and the film of Comparative Example 4 so that the length was 30% length and 20% width. At this time, the filling gas was nitrogen. It passed through a shrink tunnel with a hot air temperature of 150 ° C. This At that time, the transit time was 5 seconds. When the delamination and zigzag whitening of the packaged product were evaluated, the films of Examples 21 and 24 were AA for both items, and Comparative Example 4 was C for both items. The same result was obtained when the same experiment was repeated with a margin of 20% vertically and 30% horizontally.

[table 1]

T6.00 / S00Zdf / X3d 88 S69Z0l / S00Z OAV Continuation of Table A 1st layer 2nd layer 3rd layer 4th layer 5th layer 6th layer 7th layer Adhesion between layers Zigzag whitening

 5 μm

 4 ^ m 3 μm

 1 m 1 m Nyl (60%) + 1 μm 10 μτη

Example 1 Ί PES 1 (92%) EVOH (80%) + A A

 VL1 MP03 Ny2 (20%) + MP03 VL1

 + TPU1 (8%) IR (20%)

 IR (20%)

 5 m 4 μm

 1 μm 1 μm 3 μm 1 μ 10 μm

Example 18 Nyl (80%) + PES 1 (77%) A A AA

 VL4 MP02 EVOH MP02 VL4

 Ny2 (20%) + TPU3 (23%)

1 μm 1 / m 5 μm 4 μm 1 μm 10 μπι

 3 μm

Example 1 9 VL1 (90%) + MPO2 (90%) + Nyl (80%) + PES1 (77%) MPO2 (90%) + VL1 (90%) + AA A A

 EVOH

 Petroleum resin (10%) Petroleum resin (10%) Ny2 (20%) + TPU3 (23%) Petroleum resin (10%) Petroleum resin (10%)

5 μm 4 ^ m

 1 m 1 μm 3 μm l μm 10 μm

Example 20 0 Nl (80%) + PES1 (77%) + AA AA

 PP1 MP02 EVOH MP02 PP2

 Ny2 (20%) TPU3 (23%)

5 μm 4 m

 1 μm 3μm 1 μm 11 / m

Example 2 2 Nyl (80%) + PES1 (78%) + A A AA

 MP02 EVOH MP02 VL1

 Ny2 (20%) TPU3 (22%)

5 μm 4 μm

 3 μm \ μ12 μm

Example 2 3 Nyl (80%) + PES1 (92%) A A

 EVOH MP04 VL1

Ny2 (20%) + TPU1 (8%)

T6.00 / S00Zdf / X3d 8 S69Z0T / S00Z OAV Continuation of Table A

[Table 4] Table B

[0112] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Is.

 [0113] The present application was filed on April 27, 2004 in Japanese Patent Application (Japanese Patent Application No. 2004-132023), which was filed on April 27, 2004, and was filed in Japanese Patent Application No. 2004-132024 (April 2004). 27 is based on Japanese Patent Application (Japanese Patent Application No. 2004-132025) filed by No. 27, the contents of which are incorporated herein by reference.

 Industrial applicability

[0114] The shrinkable film of the present invention has a zigzag shape after the resin having poor stretchability and shrinkage is eliminated by disposing the thermoplastic polyester resin layer, and is sufficiently shrunk under a wide range of shrinkage conditions. It is a practical high-strength, high-barrier and high-shrink film that does not cause problems such as whitening and delamination, and can be suitably used as a packaging film.

Claims

The scope of the claims

 [1] A first layer containing a first polymer mainly composed of a thermoplastic polyester and a thermoplastic polyurethane, and a second polymer mainly composed of a repeating unit mainly containing a halogen or a hydrogen bond. A heat-shrinkable film having a second layer, wherein the first layer and the second layer are directly laminated.

 [2] The heat-shrinkable film according to claim 1, wherein the second polymer is any one selected from the group consisting of the following forces (a) to (d).

 (a) Polyamide

 (b) Ethylene vinyl alcohol copolymer

 (c) Poly salty duck biylidene

 (d) a mixture comprising a polar group-containing polyolefin and any one of (a) to (c)

[3] The heat-shrinkable film according to claim 1, wherein the thermoplastic polyester has a crystallinity of 30% or less.

 [4] The heat shrinkability according to claim 1, wherein a heat shrinkage rate in a dry heat treatment at 120 ° C is 30% or more in one direction of MD or TD and 20% or more in the other direction. the film.

 [5] The heat-shrinkable film according to claim 1, comprising a laminate in which the second layer, the first layer, and the second layer are directly laminated in this order.

[6] The laminate strength in which the second layer in which the second polymer is polyamide, the first layer, and the second layer containing resin having gas barrier properties are directly laminated in this order. The heat-shrinkable film described in 1.

[7] Use of the heat-shrinkable film according to claim 1 for a gas replacement package.

[8] The package according to claim 1, wherein the content is covered with a package, and the inside of the package is depressurized to bring the package into close contact with the content. Use of the heat-shrinkable film described in 1.