Abuse resistant shrink film

The present invention relates to a thermoplastic stretched film for packaging, and more specifically, a simultaneous extrusion multilayer stretch having oxygen blocking property and improved abuse resistance. Regarding film.

[0002] Thermoplastic films, especially polyolefin materials , require a variety of environmental protections, resistance to physical and environmental abuse during storage and distribution, and a beautiful and attractive appearance. Has been used in the packaging of products, such as perishable foods. In order for a product wrapped in this type of packaging material to have a consumer-eye-catching appearance, it requires optical properties such as high gloss, high transparency and low cloudiness. Abuse resistance is important for the maintenance of the packaging and, in the case of perishable foods, is essential for the storage of the packaged product.

[0003] Oxygen blocking is necessary in the case of foods to extend the shelf life of the packaged product, and various materials are used to reduce the air permeability of the film, thereby reducing the permeation of oxygen. Has been used. For example, ethylene vinyl alcohol copolymer (EVOH) was once known as a good oxygen blocking material and has been used in the field of multilayer packaging films, as described in several patent specifications below. It was. EVOH was also found to exhibit a large blocking property against odors or aromas.

[0004] Shrinkage is imparted to the thermoplastic film by stretching the film during film production. This shrinkage causes the film to shrink when exposed to heat, for example in a hot water bath or hot air, or to generate shrinkage stress in the packaging film if the film is in a constrained state. In a typical operation, the produced film is provided with a desired degree of shrinkage during subsequent heating in either the mechanical direction or the direction orthogonal to the machine, or in these two directions, namely the longitudinal direction and the transverse direction, respectively. It is stretched to various degrees so as to be. Quenching the film after this stretching operation imparts potential shrinkage to the resulting film. Shrinkable films give the products packaged in this type of film a smooth, tight appearance, as well as some toughness to protect the packaged products from abuse.

[0005] U.S. Pat. No. 4,398,635 issued to Hirt discloses a pharmaceutical packaging material that may have a structure in which a coextruded multilayer sheet comprises an ethylene vinyl alcohol copolymer layer sandwiched between adjacent nylon layers. .. One of the nylon layers can further adhere to the tie resin. The nylon layer can either form an outer surface or, in the form of adding yet another polymer material layer to each side of the sandwich structure, form an inner layer.

[0006] U.S. Pat. No. 4,355,721 issued to Knott et al. Has a first nylon layer, an EVOH blocking layer, another nylon layer, an adhesive layer, and another outer layer made of, for example, high density polyethylene. The simultaneous extrusion multilayer sheet is disclosed.

[0007] US Pat. No. 4,284,674 issued to Sheptak has a core layer of ethylene vinyl alcohol copolymer attached to nylon on each side, and each nylon layer is attached to chemically modified polyolefin. Yet another layer of primer material suitable for adhering the modified polyolefin to an outer layer of polypropylene or an outer layer of other material suitable for imparting toughness, flex crack resistance and moisture resistance to the multilayer film. Multilayer films that also have are disclosed.

[0008] US Pat. No. 4,407,873 issued to Christensen et al. Consists of a heat-sealed layer made of linear low-density polyethylene and linear low-density polyethylene arbitrarily blended with 0% to 80% medium-density polyethylene. A second layer, a third layer made of anhydrous modified medium density polyethylene, a fourth layer made of nylon, a fifth layer made of ethylene vinyl alcohol copolymer, and a sixth layer made of nylon. The packaging material for retort having the above is disclosed.

[0009] US Pat. No. 4,501,798 issued to Koschak et al. Discloses the use of blends of EVOH and nylon in non-uniform multilayer polymer films containing either linear low density polyethylene or ethylene vinyl acetate copolymers in the sealant layer. are doing. The film also includes an adhesive layer, preferably made of an anhydride derivative.

[0010] US Pat. No. 4,755,419 issued to Shah states that a core blocking layer made of ethylene vinyl alcohol copolymer and two intermediate layers sandwiching the blocking layer, each made of copolyamide, and a wire. A multilayer stretched film having an outer skin layer which may consist of a blend of low density polyethylene and linear medium density polyethylene and ethylene vinyl acetate or a blend of polypropylene and ethylene propylene copolymer is disclosed. The skin layer is adhered to the copolyamide layer via a modified polymer adhesive material. Films produced in accordance with this Patent Specification '419 have both oxygen barrier properties, shrinkage properties, and toughness suitable for many applications. However, due to the presence of the intermediate layer of nylon 6,66, this type of film must be stretched at a relatively high stretching temperature, which makes it difficult to operate and the optical properties are not ideal.

[0011] An object of the present invention is to provide a heat-shrinkable multilayer film having good oxygen blocking property, good optical properties, and more abuse resistance than the film of the prior art. To provide.

[0012] Another object of the present invention is to provide a film structure that is as thin as possible in order to reduce the bulk of the packaging and increase cost efficiency.

[Means for Solving the Problems] These and other purposes consist of a barrier layer and two core layers attached to the barrier layer, each consisting of a blend of two different copolyamides. Achieved by the realization of a heat shrinkable multilayer film consisting of a layer and a heat sealable outer polymer skin layer.

[0014] These purposes are also from a barrier layer consisting of a blend of ethylene vinyl alcohol copolymer and copolyamide and a blend of two different core layers, each of which is directly attached to the barrier layer, of two different types of copolyamide. By realizing a heat-shrinkable multilayer film including a core layer having substantially the same chemical composition as the copolyamide in which one of the above-mentioned copolyamides is present in the blocking layer, and a heat-sealable outer skin layer. Is also achieved.

【0015】<u style="single">Definition</u>As used herein, the term "monomer" is a relatively simple compound with a low molecular weight, usually containing carbon, that reacts with itself or with other similar molecules or compounds to produce polymers. Means a compound that can.

[0016] As used herein, the term "comonomer" means a monomer that copolymerizes with one or more different monomers in a copolymerization reaction to produce a copolymer.

[0017] As used herein, the term "polymer" means a polymerization reaction product and includes homopolymers, copolymers, terpolymers and the like.

[0018] As used herein, the term "homopolymer" means a polymer resulting from the polymerization of a single monomer, i.e., a polymer consisting essentially of a single type of repeating unit.

[0019] As used herein, the term "copolymer" means a polymer produced by the polymerization reaction of two or more different monomers. For example, the term "polymer" includes copolymerization products of ethylene with α-olefins, such as 1-hexene. However, the term "copolymer" also includes, for example, copolymer products of mixtures of ethylene, propylene, 1-hexene and 1-octene.

The term "different" as used herein, when used to define the relative properties of two or more polymers or copolymers, is chemical composition, comonomer composition, relative proportions of comonomer, molecular weight, molecular weight. It means that any one or more of various attributes such as distribution, melt flow, density or uniformity are different.

[0021] As used herein, the term "copolymerization" means the simultaneous polymerization of two or more different monomers.

[0022] As used herein, the term "heterogeneous polymer" refers to polymerization reaction products that differ in a relatively wide range of molecular weight and composition distribution, ie, polymers made using, for example, common Ziegler-Natta catalysts. Means. Polymers of this type usually have a relatively wide range of varying chain lengths and comonomer ratios.

[0023] As used herein, the term "heterogeneous catalyst" means a catalyst suitable for use in the polymerization of heterogeneous polymers according to the definitions above. Heterogeneous catalysts contain several active sites with different Lewis acidity and steric environment. The Ziegler-Natta catalyst is a heterogeneous catalyst. Specific examples of the Ziegler-Natta heterogeneous system include a metal halide activated by an organometallic cocatalyst, for example, a complex obtained by binding titanium chloride optionally containing magnesium chloride to trialkylaluminum. Specific examples of this type of system are also found in patent specifications such as US Pat. No. 4,302,565 by GOEKE et al. And US Pat. No. 4,302,566 by KAROL et al. Both of these prior patents are incorporated herein by reference in their entirety.

[0024] As used herein, the term "uniform polymer" means a polymerization reaction product having a relatively narrow molecular weight distribution and a relatively narrow composition distribution. This type of polymer has a relatively uniform comonomer sequence in the chain, a sequence distribution mirroring across all chains, similar lengths on all chains, and is usually metallocene or Manufactured using other single site type catalysts.

[0025] As used herein, the term "uniform catalyst" means a catalyst suitable for use in the polymerization of homogeneous polymers according to the definitions above. Uniform catalysts are also referred to as "single-site catalysts". This is because catalysts of this type usually have only one type of catalyst site, and this fact is believed to be the basis for the homogeneity of the polymers produced by these catalysts.

[0026] As used herein, the term "polyolefin" means any polymerized olefin that can be linear, branched, cyclic, aliphatic, aromatic, substituted or unsubstituted.

[0027] The terms "ethylene α-olefin copolymer" and "ethylene / α-olefin copolymer" as used herein refer to linear low density polyethylene (LLDPE), linear medium density polyethylene (LMDPE), very low density. And heterogeneous materials such as ultra-low density polyethylene (VLDPE and ULDPE), and homogeneous polymers such as metallocene catalytic polymers, such as EXACT material from Exxon and TAFMER material from Mitsui Petrochemical Corporation. These materials are usually ethylene and C₄~ C₁₀A copolymer with one or more comonomer selected from α-olefins, such as butene-1 (ie 1-butene), hexene-1, octene-1, etc., with relatively few side chain branches. Includes copolymers with long chains or crosslinked structures. This molecular structure contrasts with common low or medium density polyethylene, which has a higher degree of branching than its respective counterparts. LLDPE in the present specification usually has a density of about 0.915 g / cc to 0.925 g / cc, LMDPE usually has a density of about 0.926 g / cc to about 0.94 g / cc, and VLDPE or ULDPE usually has a density of about 0.926 g / cc to about 0.94 g / cc. It has a density of 0.915 g / cc or less. Other ethylene / α-olefin copolymers, such as long-chain branched homogeneous ethylene / α-olefin copolymers manufactured by Dow Chemical Company known as AFFINITY resins, are also another type of ethylene α-olefin useful in the present invention. Included as an olefin copolymer.

[0028] The term "EVOH" as used herein means an ethylene vinyl alcohol copolymer. EVOH comprises a saponified or hydrolyzed ethylene vinyl acetate copolymer and means a vinyl alcohol copolymer having an ethylene comonomer, which is produced, for example, by hydrolyzing a vinyl acetate copolymer or reacting with polyvinyl alcohol. The degree of hydrolysis is preferably 50% or more, more preferably 85% or more.

[0029] As used herein for a film and / or a film layer, the terms "shielding" and "shielding layer" refer to the ability of a single-layer or multilayer film to shield one or more gases. The oxygen shielding layer may be made of, for example, polymerized ethylene vinyl alcohol, polyvinyl chloride, polyvinylidene chloride or the like, as is known to those skilled in the art.

[0030] As used herein, the term "polyamide" means a high molecular weight polymer having an amide bond along a branched chain, more specifically a synthetic polyamide such as nylon. The term refers to polymers consisting of repeating units derived from monomers such as caprolactam, which polymerize to produce polyamide, and copolymers of two or more amide monomers, also referred to herein as "copolyamides," and polymerized alone. Also included are copolymers derived from copolymerization of caprolactam with comonomer, which does not produce polyamide when used.

[0031] As used herein, the term "ethylene vinyl acetate copolymer" or "EVA" is a copolymer formed of ethylene and a vinyl acetate monomer, with a large amount of ethylene inducing units, preferably about. It means a copolymer that accounts for 60% to 98% by weight, has a small amount of vinyl acetate inducing units, and preferably accounts for about 2% to 40% by weight.

[0032] As used herein, the term "polypropylene" means any polymer consisting of propylene polymerization units, whether homopolymers or copolymers, of this type of homopolymers and copolymers. Also includes blends. The term "propylene polymerization unit" in this case means a polymerization unit in the polymer chain, the repeating unit is derived from the polymerization of the unsubstituted propylene monomer and / or the substituted propylene polymer, and the double bond is opened by the polymerization reaction. ..

[0033] As used herein, the term "ethylene propylene copolymer" or "EPC" means polypropylene copolymerized with a small amount of ethylene comonomer. The term "ethylene propylene butene terpolymer" or "EPB" means a terpolymer containing these three comonomeres in various proportions.

[0034] The term "anhydride functionality" as used herein is blended with one or more polymers, grafted onto a polymer, or copolymerized with a polymer. It means any form of anhydrous functional group, such as maleic anhydride, fumaric anhydride, etc., and usually derivatives of this type of functional group, such as acids, esters, and metal salts derived from them. Including.

[0035] As used herein, terms such as "modified polymer", more specifically "modified ethylene vinyl acetate copolymer" and "modified polyolefin" are anhydrous functional groups according to the above definitions. Means a polymer grafted and / or copolymerized and / or blended with. The modified polymer of this type is not simply a blend of the anhydride functional groups, but is preferably grafted or copolymerized.

[0036] As used herein, the term "anhydride-containing polymer" refers to (1) a polymer produced by copolymerizing an anhydride-containing monomer with a second different monomer, (2) an anhydride graft copolymer, And (3) one or more of a mixture of a polymer and an anhydride-containing compound.

[0037] As used herein, the term "internal layer" or "interior layer" means any film layer in which two major surfaces are attached to other layers of a multilayer film.

[0038] As used herein, the term "outer layer" means any film layer of a multilayer film in which only one of the major surfaces is directly attached to another layer of the film.

[0039] The expression "directly adhered" to the film layer as used herein means that the subject film layer is the object of the film layer via a tie layer, an adhesive or another layer. It means that it is attached without. On the other hand, the term "adhering" used for the film layer in the present specification refers to a state in which the subject film is directly adhered to the object film, or, for example, a tie layer. It means either a state of being indirectly attached via an adhesive, an adhesive layer or another layer. As used herein, the term "between" as used for a film layer, which is described as being between two other specific layers, has two other layers as the subject. The state of being directly attached to the layer, for example, the structure A / B / C where B is between A and C and is directly attached to A and C, and the subject layer is indirectly attached to two other layers. Includes both structures A / B / D / D / E that are attached to, eg, C is between A and E but is not directly attached to A or E.

[0040] The terms "core" and "core layer" as used herein for a multilayer film have a primary function other than functioning as an adhesive or compatibilizer for adhering the two layers to each other. Means any internal film layer. One or more core layers usually impart a desired level of strength, ie, modulus, to the multilayer film.

[0041] As used herein, the term "sealed" means any means for closing the packaging, such as heat sealing with hot air and / or heating bars, ultrasonic sealing, such as gathering the casing. It even includes techniques such as closing with a clip.

[0042] As used herein for a multilayer film, the term "sealant layer" or "sealing layer" means an outer film layer used to seal a film against itself or another layer. To do. The term "sealant layer" as used herein is used only for the outer layer, no matter how thin it is. In the case of packaging with wrap seals, the term "sealant layer" usually means both the outer film layer of the packaging and the support layer adjacent to these sealant layers.

[0043] As used herein, the term "tie layer" or "adhesive layer" means any inner layer whose primary purpose is to bond the two layers together.

[0044] The term "skin layer" as used in the present invention means the outermost layer of a multilayer film when packaging a product. This skin layer is placed in an overworked environment.

[0045] As used herein, the term "extruded" refers to the process of forming a continuous shape by passing a molten plastic material through a die and then cooling or chemically curing it. The polymer material having a relatively high viscosity is supplied into a variable-pitch rotating screw immediately before extrusion through the die, and is fed to the die by the screw.

[0046] As used herein, the term "simultaneous extrusion" refers to two or more orifices provided so that two or more extruded materials are coalesced and welded together to form a laminated structure prior to cooling, i.e. quenching. Means the process of extruding two or more materials into a single die with. Simultaneous extrusion can be used in inflation, independent film extrusion and extrusion coating processes.

As used herein, the term "mechanical direction", or "MD" for short, refers to the film in the "length-wise" direction, i.e., when the film is formed during extrusion and / or coating. Means the direction of.

[0048] As used herein, the term "transverse direction", or "TD" for short, means a film transverse direction that is orthogonal to the direction or longitudinal direction of the machine.

As used herein, the term "oriented" is used in a stretched form by stretching at a high temperature (stretching temperature) and then cooling while substantially retaining the dimensions of the stretched state. Means a polymer-containing material that has been "cured (set)". When the stretched polymer-containing material in the unrestrained and non-annealed state is later heated to the stretching temperature, heat shrinkage occurs and returns to the original unstretched state, that is, almost the same size as the size before stretching. More specifically, the term "stretching" herein means a stretched film in which stretching can occur in one or more of a variety of methods.

[0050] As used herein, the term "stretching ratio" means the product of the elongations of plastic film materials in multiple directions, usually in two directions orthogonal to each other. Here, the extension in the mechanical direction is referred to as "drawing", and the extension in the transverse direction is referred to as "stretching". The degree of stretch is also referred to as the stretch ratio, or is sometimes referred to as the "racking ratio".

Although most of the definitions described above are substantially the same as those understood by those skilled in the art, one or more of these definitions are unique to the present invention. Because it is described as, it may differ from the meaning normally understood by those skilled in the art.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention preferably has a palindrome or a symmetrical structure and is produced, for example, by a co-extrusion method, which is typically stretched by a blowing bubble process, preferably two. The present invention relates to an axially stretched multilayer film.

[0053] One of the preferred structures is symmetrical with a composition of A / B / C / D / C / B / A and a layer thickness ratio of 3/1/1/1/1/1/3. It is a layered film. D is the core blocking layer, C is the core copolyamide blend layer, B is the adhesive layer, and A is the sealable outer skin layer. Another preferred structure is a composition of A / A'/ B / C / D / C / B / A'/ A and a layer thickness ratio of 3/1/1/1/1/1/1/1. It is a symmetrical 9-layer film of / 3. A, B, C and D have substantially the same meanings as described above, and A'is a subskin layer having substantially the same composition as A but containing no additives that may be optionally contained in A. The presence of the A'layer in this 9-layer structure contributes to the maintainability of the structure by reducing the occurrence of delamination, as will be described in detail later.

[0054] The barrier layer of the film of the present invention is most preferably composed of a blend of ethylene vinyl alcohol (EVOH) copolymer and copolyamide. A preferred copolyamide is nylon 6,12, eg, Emser's Griron CF 6S, a copolymer of caprolactam and laurolactam with a melting point of 266 ° F and a density of 1.05 g / cc. A preferred ethylene vinyl alcohol copolymer resin is a resin having an ethylene content of about 28 mol% to 49 mol%. A typical example of this type of resin is Eval LC-F101A from Eval of America. Normally, EVOH makes up the majority of the blocking blend, most preferably about 90% by weight, and copolyamides make up about 10% of the blend, while EVOH makes up about 80% to 100% of the blocking blends and copolyamides. May make up about 0% to about 20% of the blend. Adding a small amount of copolyamide, which has a melting point of 20 ° F or less higher than the melting point of EVOH, enhances the workability of the barrier layer, and thus the processability of the entire film structure. The thickness of the barrier layer is preferably about 0.05 to 0.15 mil.

[0055] The core layer made of the copolyamide blend adheres directly to both sides of the blocking layer. These layers also preferably have a thickness of 0.05 to 0.15 mils and consist of a blend of two different copolyamides, one of which is the same as the copolyamide contained in the barrier layer. Preferred blends are nylon 6,66 and nylon 6,12, with nylon 6,12 also contained in small amounts in the barrier layer. Preferred nylon 6,66 is BASF's Ultramid C35, a copolymer of caprolactam, hexamethylenediamine and adipic acid with a melting point of 385 ° F.

A core layer made of a copolyamide blend is present in the film structure primarily for the purpose of enhancing abuse resistance. However, the presence of this type of layer causes various operational problems. This is because this type of nylon has a higher melting point and softening point than the normal olefin-based resin that forms the rest of the structure. Basically, the preferred blend of nylon 6,66 components enhances impact resistance and other abuse-related properties. However, since nylon 6,66 has a melting point of 385 ° F, it is usually too rigid to stretch the entire structure (see Comparative Example 4 below). Nylons 6,12 have a melting point of approximately 266 ° F, which lowers the softening point of the blend, thereby allowing the production of highly abuse resistant films with extremely low thickness (eg, Example 3 and other prior art). See Examples showing comparison with technical films). In general, the second copolyamide in the blend preferably has a melting point at least about 50 ° F lower than the melting point of the first copolyamide. More specifically, the second copolyamide preferably has a melting point of about 320 ° F. or less.

[0057] In some embodiments, the outer skin layer may consist of a blend of at least one ethylene α-olefin copolymer and an ethylene vinyl acetate copolymer. This type of blend preferably consists of two different homogeneous ethylene octene copolymers and an ethylene vinyl acetate copolymer. Preferred ethylene octene copolymers include what is referred to as linear low density polyethylene, such as Dowlex 2045, a uniform ethylene octene copolymer with a density of 0.918 g / cc commercially available from Dow, and linear medium density polyethylene, such as Dow. Examples include Dowlex 2037, a uniform ethylene octene copolymer with a density of 0.935 g / cc commercially available from the company. A preferred ethylene vinyl acetate copolymer is Rexene PE containing 3.3.% by weight of vinyl acetate. It is the 1335. The blend typically contains a small amount of slip and anti-tack, and may also include anti-fog, depending on the intended use. The blend preferably comprises from about 40% to about 60% LLDPE, from about 20% to about 30% LMDPE and from about 20% to about 30% EVA. In another embodiment where the outer skin layer usually occupies 25% to 35% of the total thickness of the film, the outer skin layer can consist of ethylene propylene copolymer, polypropylene or a blend thereof. Polypropylene may have the form of a masterbatch containing about 4% by weight silica-containing anti-adhesive, about 5% by weight amide wax, and about 1% lubricant. Amido waxes and lubricants are well known in the art as slip agents. In the blend, the polypropylene component of the outer skin layer accounts for about 4% to about 15% by weight, most preferably about 8% by weight of the outer layer. A suitable ethylene propylene copolymer is Solvay's Eltex P KS409 containing 3.2% by weight ethylene. Suitable polypropylene is Exxon PD It is 4062E-7. Again, each of the outer skin layers preferably occupies 25% to 35% of the total thickness of the film, but as in the A'layer described above, an intermediate "barefoot" is used to improve adhesion. If subskin layers are preferred, make sure that each of the actual skin layers occupies only 5% to 15% of the total thickness of the film and each intermediate layer occupies about 25% to about 35% of the total thickness. You may.

[0058] The skin layer or skin layer / subskin layer pair is usually adhered to the copolyamide core layer via an adhesive layer or a tie layer. The choice of specific adhesive polymer material is made depending on the blend used for the outer layer. Preferred adhesives usually consist of a blend of a graft copolymer of linear low density polyethylene and one or more unsaturated fused ring anhydrous carboxylic acids mixed with one or more resins such as linear low density polyethylene. Other adhesives, such as low density polyethylene based adhesives, may also be used. Adhesive layers should typically have a thickness of less than or equal to about 5% to about 15% of the total thickness of the film.

[0059] The film produced by the method of the present invention is preferably stretched from hot air by a blow bubble type stretching process. This type of film preferably has a stretch ratio in the longitudinal direction or the mechanical direction of 3.4 to 3.6 and a stretch ratio in the transverse direction of 3.0 to 3.6.

[Examples] The following examples show preferred embodiments of the heat-shrinkable film of the present invention. The following tests were used to evaluate this type of film:<u style="single">Tensile strength</u>: Measurement of the force required to break a film sample. Measured with ASTM D 882.

【0061】<u style="single">Growth</u>: Measurement of elongation required to break a film sample. Measured with ASTM D 882.

【0062】<u style="single">Modulus</u>: The ratio of the change in tensile stress to the change in elongation at the straight part of the Instron tensile test curve. ASTM D 882-Measured by Method A.

【0063】<u style="single">Tear</u>: Force required to widen a crevice through a microslit in a film sample with a sharp blade; measured by ASTM 1938.

【0064】<u style="single">Free contraction</u>10 cm x 10 cm Dimensional change rate when a film sample is subjected to selected heat. Measured with ASTM D 2732.

【0065】<u style="single">Ball burst</u>: Energy required to burst and penetrate a restrained film sample. Measured with ASTM D 3420.

【0066】<u style="single">Instrument impact</u>: Energy required to puncture a constrained film sample similar to the ball rupture. However, the instrument impact tester can also measure the breaking tensile / elongation curve. The "gradient" is the ratio of the change in tensile stress to the change in elongation at the straight line portion of the curve. A "peak" is a measurement of the maximum stress applied to a sample to cause a fracture. "Impact energy" is a measure of the energy absorbed by the sample prior to fracture. Instrument impact is measured with ASTM D 3763.

【0067】<u style="single">vibration</u>: The package wrapped with the film of the present invention is packed in a box over four stages at a ratio of four per stage, separating each stage by inserting cardboard. This box is placed on a vibration table and subjected to random vibration for 1 hour to simulate the transportation state. Measured by ASTM 4728.

[0068] In the production of the multilayer film of the present invention, the following resins were used as described in Examples described later:<u style="single">EPC1</u>: Solvay Eltex P KS409, ethylene propylene copolymer with 3.2% by weight ethylene content.

【0069】<u style="single">EPC2</u>: Mitsui's Tafmer XR107L, uniform ethylene propylene copolymer with a density of 0.89 g / cc.

【0070】<u style="single">EPC3</u>: Exxon PD9302, ethylene propylene copolymer with 3.3% by weight ethylene content.

【0071】<u style="single">EPB</u>: Himont's KT-021P, ethylene propylene buteneter polymer.

【0072】<u style="single">PC1</u>: Himont KS031P, propylene copolymer with density 0.88g / cc.

【0073】<u style="single">PC2</u>: Mitsui's Tafmer P0480, propylene copolymer with a density of 0.87 g / cc.

【0074】<u style="single">PP1</u>: Polypropylene-based masterbatch with anti-fog and anti-stick agents added.

【0075】<u style="single">PP2</u>: Exxon PD 4062 E-7, polypropylene.

【0076】<u style="single">PP3</u>: Polypropylene-based masterbatch with anti-adhesive agent added.

【0077】<u style="single">SPP</u>: Fina EOD 9306, uniform syndiotactic polypropylene.

【0078】<u style="single">ADH1</u>: DuPont Bynel CXA 4104, anhydrous grafted polyolefin in ethylene butene copolymer.

【0079】<u style="single">ADH2</u>: Mitsui's propylene-based Admer adhesive.

【0080】<u style="single">ADH3</u>: Mitsui's Admer glue.

【0081】<u style="single">CPA1</u>: BASF Ultramid, Nylon 6,66.

【0082】<u style="single">CPA2</u>: Emser Griron CF 6S, Nylon 6,12.

【0083】<u style="single">EVOH1</u>: Eval LC-F101A from Eval of America, ethylene vinyl alcohol copolymer.

【0084】<u style="single">EVOH2</u>: Eval LC-E151A from Eval of America, ethylene vinyl alcohol copolymer.

【0085】<u style="single">EO1</u>: Dowlex 2045, non-uniform ethylene octene copolymer with a density of 0.918 g / cc.

【0086】<u style="single">EO2</u>: Dowlex 2037, non-uniform ethylene octene copolymer with a density of 0.935 g / cc.

【0087】<u style="single">EO3</u>: Dow's Affinity PL1880, uniform branched chain ethylene octene copolymer with a density of 0.902 g / cc.

【0088】<u style="single">EO4</u>: Dow Affinity PL1840, Uniform Branched Chain Ethylene Octene Copolymer with Density 0.908g / cc.

【0089】<u style="single">EO5</u>: Dow Affinity FM1570, Uniform Branched Chain Ethylene Octene Copolymer with Density 0.915g / cc.

【0090】<u style="single">EVA</u>: Rexene PE 1335, ethylene vinyl acetate copolymer with a vinyl acetate content of 3.3% by weight.

【0091】<u style="single">Example 1</u>As described above, the symmetrical 7-layer structure was extruded and stretched from hot air at 255 ° F. The resulting 1 mil film had the following structure: 92% EPC1 + 8% PP1 / ADH1 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH1 / 92% EPC1 + 8% PP1, layer thickness ratio 3/1/1/1/1/1/3. Anti-fog and anti-stick agents were added to the polypropylene support of the skin layer. Although the film of this example was difficult to stretch, it showed significantly improved optical properties as compared with the film of Comparative Example 4.

【0092】<u style="single">Example 2</u>As described above, the symmetrical 7-layer structure was extruded and stretched from hot air at 256 ° F. The resulting 1 mil film had the following structure: 92% EPB + 8% PP1 / ADH1 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH1 / 92% EPB + 8% PP1, layer thickness ratio 3/1/1/1/1/1/3. Anti-fog and anti-stick agents were added to the polypropylene support of the skin layer. The film structure of this example was found to be easier to stretch than the film of Example 1, but some delamination was observed between the skin layer and the respective adjacent adhesive layers.

【0093】<u style="single">Example 3</u>As described above, the symmetrical 7-layer structure was extruded, irradiated and stretched from hot air at 255 ° F. The resulting 1 mil film had the following structure: 50% EO1 + 25% EO2 + 25% EVA / ADH1 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH1 / 50% EO1 + 25% EO2 + 25% EVA, layer thickness ratio 3/1/1/1/1/1/3. Again, a small amount of anti-fog and anti-adhesive was added to the outer skin layer. No delamination was observed, but the optical properties were inferior. This is probably due to the presence of nylon, which had to be stretched at 255 ° F, which is relatively higher than the melting point of the components of the skin layer. The film of this example also had low stretchability.

【0094】<u style="single">Comparative Example 4</u>The following symmetrical 7-layer structure was extruded and irradiated for comparison: 50% EO1 + 25% EO2 + 25% EVA / ADH1 / CPA1 / 90% EVOH1 + 10% CPA2 / CPA1 / ADH1 / 50% EO1 + 25 % EO2 + 25% EVA, layer thickness ratio 3/1/1/1/1/1/3. Again, a small amount of anti-adhesive and anti-fog agents were added to the outer skin layer. Stretching was attempted at various temperatures but was unsuccessful.

【0095】<u style="single">Example 5</u>As described above, the symmetrical 7-layer structure was extruded and stretched from hot air at 245 ° F. The resulting 1 mil film had the following structure: 50% EO1 + 25% EO2 + 25% EVA / ADH1 / 50% CPA1 + 50% CPA2 / 90% EVOH2 + 10% CPA2 / 50% CPA1 + 50% CPA2 / ADH1 / 50% EO1 + 25% EO2 + 25% EVA, layer thickness ratio 3/1/1/1/1/1/3. In this case as well, a small amount of anti-adhesive agent and anti-fog agent were added to the outer skin layer. This structure represented the success of attempts to reduce the stretching temperature required to improve the optical properties. The structure of this example showed improved optical properties compared to the film of Example 3. However, the optical properties were inferior to those of the structure containing the EPC skin layer such as the film of Example 1.

【0096】<u style="single">Example 6</u>A symmetrical 7-layer film structure with the same lamination composition and layer thickness ratio as the film of Example 5 was stretched from hot air at 235 ° F. When the stretching temperature was lowered by 10 ° F in this way, a film having further improved optical properties was obtained. However, at this low stretching temperature, it was difficult to maintain a stable stretching bubble.

【0097】<u style="single">Example 7</u>As described above, a symmetrical 7-layer structure was extruded and stretched from hot air at 256 ° F. The resulting 1 mil film had the following structure: EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH2 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / EPB, layer Thickness ratio 3/1/1/1/1/1/3. No delamination was observed.

【0098】<u style="single">Comparative Example 8</u>For comparison purposes, a symmetrical five-layer structure was extruded, irradiated and stretched from hot air at 241 ° F as described above. The resulting 1.5 mil film had the following structure: 50% EO1 + 25% EO2 + 25% EVA / ADH1 / 90% EVOH2 + 10% CPA2 / ADH1 / 50% EO1 + 25% EO2, layer Thickness ratio 3/1/1/1/3.

【0099】<u style="single">Examples 9-14</u>The films of Examples 1-3, 5, 7 and Comparative Example 8 were tested for tensile strength, elongation, modulus, tear, impact resistance, free shrinkage and shrinkage. The results are shown in Table I below. This table shows the impact value for each structure first in peak load (unit pounds) and then in breaking energy (unit foot-pounds).

[0100] [Table 1]<img file="JP3662976B2_D0001.tif" />[0101] Table I shows that the breaking tensile strength, breaking elongation and modulus of the film of the present invention are all improved as compared with the film of Comparative Example 8. There is no significant change in impact characteristics. As described above, the 1 mil film produced in the present invention can obtain superior tensile strength and elongation as compared with the 1.5 mil film of the prior art, and the same impact characteristics.

【0102】<u style="single">Examples 15 and 16</u>The films of Example 2 and Comparative Example 8 were subjected to a use test to examine their abuse resistance. Ninety-six packages were hand-crafted by wrapping, sealing, and heat-shrinking a pound of mass on a meat dish with each of these two films, and then subjected to vibration testing according to ASTM 4728. The results are shown in Table II below.

[0103] [Table 2]<img file="JP3662976B2_D0002.tif" />The sealing defects seen in the film of Example 2 were due to the sealing parameters used. That is, the sealing temperature was set specifically for the sealing layer of the film of Comparative Example 8. If the sealing parameters set specifically for the sealing layer of the film of Example 2 are used, poor sealing will probably be observed on the film of Comparative Example 8.

【0105】<u style="single">Example 17</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 252 ° F. The resulting 1 mil film had the following structure: EPB / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / EPB / EPB, layer thickness ratio 3/1/1/1/1/1/1/1/1/3. Anti-fog and anti-stick agents were blended directly into the ethylene propylene butene copolymer of the outer skin layer. No delamination was observed.

【0106】<u style="single">Example 18</u>A film having a thickness of 1.5 mil was produced by the procedure of Example 7.

【0107】<u style="single">Example 19</u>Extruded symmetrical 9-layer structure with the following composition: EPB / EPB / ADH3 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH3 / EPB / EPB, Layer thickness ratio 3/1/1/1/1/1/1/1/1/3. Anti-fog and anti-stick agents were blended directly into the ethylene propylene butene copolymer of the outer skin layer. This structure could not be stretched under the intended conditions.

【0108】<u style="single">Example 20</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 257 ° F. The resulting 1 mil film had the following structure: EPB / PP2 / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / PP2 / EPB, layer thickness ratio 3/1/1/1/1/1/1/1/1/3. Anti-fog and anti-stick agents were blended into the outer skin layer. No delamination was observed.

【0109】<u style="single">Example 21</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 252 ° F. The resulting 1 mil film had the following structure: EPB / PC1 / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / PC1 / EPB, layer thickness ratio 3/1/1/1/1/1/1/1/1/3. Anti-fog and anti-stick agents were blended into the outer skin layer. No delamination was observed.

【0110】<u style="single">Examples 22-24</u>The films of Examples 17, 20 and 21 were tested for tensile strength, elongation, modulus, tear, impact resistance, free shrinkage and shrinkage. The results are shown in Table III below. This table shows the impact value for each structure first in peak load (unit pounds) and then in breaking energy (unit foot-pounds). For comparison, the results of the same test of Comparative Example 8 shown in Table I are also shown in Table III.

[0111] [Table 3]<img file="JP3662976B2_D0003.tif" />Table III shows that the breaking tensile strength, breaking elongation and modulus of the film of the present invention are all improved as compared with the film of Comparative Example 8. The film of Example 17 also has improved impact characteristics. Thus, the 1 mil film produced in the present invention can provide better tensile strength, elongation and impact properties than the prior art 1.5 mil film.

【0113】<u style="single">Examples 25 and 26</u>The film of Example 18, the same film of Example 17, but 1.5 mil thick, and the film of Comparative Example 8 were subjected to a use test to examine their abuse resistance. Ninety-six packages were hand-crafted by wrapping, sealing, and heat-shrinking a pound of mass on a meat dish with each of these two films, and then subjected to vibration testing according to ASTM 4728. The results are shown in Table IV below.

[0114] [Table 4]<img file="JP3662976B2_D0004.tif" /> 【0115】<u style="single">Example 27</u>An attempt was made to produce a symmetrical 7-layer film with the following structure: 66% EPB + 34% EPC2 / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / 66% EPB + 34% EPC2, layer thickness ratio 3/1/1/1/1/1/3. Anti-adhesive and anti-fog agents were blended directly into the ethylene propylene butene copolymer of the outer skin layer. The structure of this example could not be stretched under the intended conditions.

【0116】<u style="single">Example 28</u>An attempt was made to produce a symmetrical 7-layer film with the following structure: 66% SPP + 34% EPC2 / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / 66% SPP + 34% EPC2, layer thickness ratio 3/1/1/1/1/1/3. Anti-adhesive and anti-fog agents were blended directly into the syndiotactic polypropylene of the outer skin layer. The structure of this example could not be stretched under the intended conditions.

【0117】<u style="single">Example 29</u>An attempt was made to produce a symmetrical 9-layer film with the following structure: 66% EPB + 34% PC2 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / EPB / 66% EPB / + 34% PC2, layer thickness ratio 3/1/1/1/1/1/1/1/3. Anti-adhesive and anti-fog agents were blended directly into the ethylene propylene butene copolymer of the outer skin layer. The structure of this example could not be stretched under the intended conditions.

【0118】<u style="single">Example 30</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 250 ° F. The resulting 1 mil film had the following structure: 77% EPB + 15% PC2 + 8% PP3 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80 % CPA1 + 20% CPA2 / ADH2 / EPB / 77% EPB + 15% PC2 + 8% PP3, layer thickness ratio 2/2/1/1/1/1/1/2/2.

【0119】<u style="single">Example 31</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 250 ° F. The resulting 1 mil film had the following structure: 50% EO1 + 25% EO2 + 25% EVA / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80 % CPA1 + 20% CPA2 / ADH2 / EPB / 50% EO1 + 25% EO2 + 25% EVA, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the outer skin layer. Some delamination was observed between the skin layer and the adjacent ethylene / propylene / butene copolymer layer.

【0120】<u style="single">Example 32</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 250 ° F. The resulting 1 mil film had the following structure: 50% EPB + 50% SPP / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 50% EPB + 50% SPP, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. The film of this example could be easily stretched.

【0121】<u style="single">Example 33</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 250 ° F. The resulting 1 mil film had the following structure: 66% EPB + 34% SPP / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 66% EPB + 34% SPP, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. The film of this example was difficult to process at the desired stretching temperature.

【0122】<u style="single">Example 34</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 250 ° F. The resulting 1 mil film had the following structure: 50% EPB + 50% PC2 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 50% EPB + 50% PC2, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. The film of this example was difficult to process at the desired stretching temperature.

【0123】<u style="single">Example 35</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 250 ° F. The resulting 1 mil film had the following structure: 66% EPB + 34% PC2 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 66% EPB + 34% PC2, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. Some delamination was observed.

【0124】<u style="single">Example 36</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 248 ° F. The resulting 1 mil film had the following structure: 50% EPB + 50% EPC2 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 50% EPB + 50% EPC2, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. Some delamination was observed.

【0125】<u style="single">Example 37</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 248 ° F. The resulting 1 mil film had the following structure: 66% EPB + 34EPC2 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20% CPA2 / ADH2 / EPB / 66% EPB + 34% EPC2, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. The film structure of this example was difficult to process at the desired stretching temperature.

【0126】<u style="single">Example 38</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 249 ° F. The resulting 1 mil film had the following structure: 50% EPB + 50% EO3 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 50% EPB + 50% EO3, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. The film structure of this example was difficult to process at the desired stretching temperature.

【0127】<u style="single">Example 39</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 249 ° F. The resulting 1 mil film had the following structure: 66% EPB + 34% EO3 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 66% EPB + 34% EO3, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. Some delamination was observed.

【0128】<u style="single">Example 40</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 249 ° F. The resulting 1 mil film had the following structure: 50% EPB + 50% EO4 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 50% EPB + 50% EO4, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. The film could be easily stretched, but had poor optical properties.

【0129】<u style="single">Example 41</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 249 ° F. The resulting 1 mil film had the following structure: 66% EPB + 34% EO4 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 66% EPB + 34% EO4, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer. This film structure was difficult to process at the desired stretching temperature.

【0130】<u style="single">Example 42</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 248 ° F. The resulting 1 mil film had the following structure: 66% EPB + 34% EO5 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80% CPA1 + 20 % CPA2 / ADH2 / EPB / 66% EPB + 34% EO5, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer.

【0131】<u style="single">Example 43</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 248 ° F. The resulting 1 mil film had the following structure: 50% EPB + 25% EO1 + 25% EO3 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80 % CPA1 + 20% CPA2 / ADH2 / EPB / 50% EPB + 25% EO1 + 25% EO3, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer.

【0132】<u style="single">Example 44</u>As described above, a symmetrical 9-layer structure was extruded and stretched from hot air at 248 ° F. The resulting 1 mil film had the following structure: 50% EPB + 25% EO1 + 25% EO5 / EPB / ADH2 / 80% CPA1 + 20% CPA2 / 90% EVOH1 + 10% CPA2 / 80 % CPA1 + 20% CPA2 / ADH2 / EPB / 50% EPB + 25% EO1 + 25% EO5, layer thickness ratio 1/3/1/1/1/1/1/3/1. Anti-fog and anti-stick agents were blended into the ethylene / propylene / butene copolymer of the outer skin layer.

【0133】<u style="single">Examples 45-53</u>The films of Examples 31, 32, 35, 36, 39, 40 and 42-44 were tested for tensile strength, elongation, modulus, tear, impact resistance, free shrinkage and shrinkage. The results are shown in Table V below. This table shows the impact value for each structure first in peak load (unit pounds) and then in breaking energy (unit foot-pounds). For comparison, the results of the same test in Comparative Example 8 shown in Table I are also shown in Table V.

[0134] [Table 5]<img file="JP3662976B2_D0005.tif" />Table V shows that the breaking tensile strength, breaking elongation and modulus of the film of the present invention are all improved as compared with the film of Comparative Example 8. Compared to the physical properties of the films evaluated in Examples 17, 20 and 21 above, the films of these Examples, all of which contained a uniform ethylene α-olefin in the outer skin layer, had tensile strength and modulus values. Is declining and the growth rate is increasing. Thus, the addition of a homogeneous ethylene α-olefin gives a film with greater flexibility. The impact and shrinkage values are also improved compared to the films of Examples 17, 20 and 21.

【0136】<u style="single">Example 54</u>A symmetrical 7-layer structure similar to that described in Example 3 above was extruded, irradiated and stretched from hot air at 253 ° F. The resulting 1 mil film had the following structure: 50% EO1 + 25% EO2 + 25% EVA / ADH1 / 60% CPA1 + 40% CPA2 / 90% EVOH1 + 10% CPA2 / 60% CPA1 + 40% CPA2 / ADH1 / 50% EO1 + 25% EO2 + 25% EVA, layer thickness ratio 3/1/1/1/1/1/3. In this case as well, a small amount of anti-adhesive agent and anti-fog agent were added to the outer skin layer. This film also had poor processability, but its optical properties were improved compared to the film of Example 3.

【0137】<u style="single">Example 55</u>A symmetrical 7-layer structure similar to that described in Example 3 above was extruded and stretched from hot air at 245 ° F. The resulting 1 mil film had the following structure: 92% EPC3 + 8% PP1 / ADH1 / 70% CPA1 + 30% CPA2 / 90% EVOH1 + 10% CPA2 / 70% CPA1 + 30% CPA2 / ADH1 / 92% EPC3 + 8% PP1, layer thickness ratio 3/1/1/1/1/1/3.

【0138】<u style="single">Example 56</u>A symmetrical 7-layer structure with the same laminated composition as the film of Example 3 was extruded, irradiated and stretched from hot air at 245 ° F to a thickness of 1 mil, a layer thickness ratio of 6/2/1 /. A 2/1/2/6 film was produced.

【0139】<u style="single">Example 57</u>A symmetrical seven-layer structure having the same laminated composition as the film of Example 56 was extruded, irradiated and stretched from hot air at 240 ° F. to produce a 1 mil film.

【0140】<u style="single">Example 58</u>A symmetrical seven-layer structure having the same laminated composition as the films of Examples 56 and 57 was extruded, irradiated and stretched from hot air at 235 ° F to produce a 1 mil film. This structure could be stretched at the low temperature due to the reduced thickness of the nylon layer, resulting in improved optical properties and stretchability.

【0141】<u style="single">Example 59</u>As described above, a symmetrical 7-layer structure was extruded, irradiated and stretched from hot air at 235 ° F. The resulting 1 mil film had the following structure: 50% EO1 + 25% EO2 + 25% EVA / ADH1 / 60% CPA1 + 40% CPA2 / 90% EVOH1 + 10% CPA2 / 60% CPA1 + 40% CPA2 / ADH1 / 50% EO1 + 25% EO2 + 25% EVA, layer thickness ratio 6/2/1/2/1/2/6. That is, the film of this example has the same composition and layer thickness ratio as the films of Examples 56-58, except for the blend ratio of copolyamide sandwiching the barrier layer. This film was stretched at the same low temperature as the film of Example 58 and therefore exhibited excellent optical properties and stretchability.

【0142】<u style="single">Comparative Example 60</u>For comparison, a film having the same lamination composition and layer thickness ratio as the film of Comparative Example 8 was produced at a thickness of 1 mil.

【0143】<u style="single">Comparative Example 61</u>For comparison, films having the same laminated composition as the films of Comparative Examples 8 and 60 were produced at a thickness of 1 mil, provided with a layer thickness ratio of 5/1/1/1/5.

【0144】<u style="single">Examples 62-68</u>The films of Examples 54, 55, 58, 59 and 3 and Comparative Examples 60 and 61 were tested for tensile strength, elongation, modulus, tear, impact resistance, free shrinkage and shrinkage. The results are shown in Table VI below. This table shows the impact value for each structure first in peak load (unit pounds) and then in breaking energy (unit foot-pounds). For comparison, the results of the same test in Comparative Example 8 shown in Table I are also shown in Table VI.

[0145] [Table 6]<img file="JP3662976B2_D0006.tif" />Table VI shows that the breaking tensile strength and modulus values of the films of Examples 3, 54, 55 and 58 are improved compared to the films of Comparative Example 8.<u style="single">Examples 69-82</u>The film sealability of Examples 3, 54, 56, 58, 59 and Comparative Examples 60 and 61 was tested on an Ilapak Delta P sealing machine. The number of packages formed, the sealing temperature used, and the number and proportion of airtight packages obtained are shown in Table VII below.

[0147] [Table 7]<img file="JP3662976B2_D0007.tif" /> 【0148】<u style="single">Examples 83-87</u>The films of Examples 3, 54, 58, 59 and Comparative Example 8 were subjected to use tests to examine their abuse resistance. Ninety-six packages were hand-crafted by wrapping, sealing, and heat-shrinking a pound of mass on a meat dish with each of these two films, and then subjected to vibration testing according to ASTM 4728. The results are shown in Table VIII below.

[0149] [Table 8]<img file="JP3662976B2_D0008.tif" />As confirmed in this table, the 1 mil film of Example 3 has similar abuse resistance to the 1.5 mil film of Comparative Example 8. The film of Example 54 is not significantly lower than the abuse resistance of the prior art structure.

【0151】<u style="single">Examples 88-92</u>The antifogging properties of the films of Examples 3 and 54 and Comparative Example 60 were evaluated by the water-in-beaker method. That is, the film was placed on a beaker containing water and fixed, and the occurrence of fogging was examined at 1 hour, 24 hours, and 48 hours. The film of the present invention was subjected to a fogging inspection on both the inner surface layer, that is, the layer constituting the inner surface of the bubble during stretching and the outer surface layer. All films were graded on a scale of 1-5. Stage 1 represents a completely cloudy film in a duplicate blind examination, and stage 5 represents a completely transparent film. The results are shown in Table IX below.

[0152] [Table 9]<img file="JP3662976B2_D0009.tif" />[0153] As described above, the film of the present invention showed superior antifogging property to the structure of the prior art of the comparative example.

【0154】<u style="single">Examples 93-96</u>The fogging of the films of Examples 3 and 54 and Comparative Examples 8 and 60 was examined by a double blind inspection and graded on a scale of 1 to 4. Stage 1 represents the maximum haze and Stage 4 represents the most transparent film. The results are shown in Table X below.

[0155] [Table 10]<img file="JP3662976B2_D0010.tif" />[0156] In this case, the score of the film of the present invention was significantly lower than that of the 1 mil prior art film of Comparative Example 60. However, the film of Example 3 is compared to the film of Comparative Example 8, i.e., a 1.5 mil prior art structure that must be used to obtain abuse resistance similar to that of the structures of the present invention. It only showed a slightly higher degree of cloudiness.

[0157] The preferred embodiments of the present invention described above are for clarifying the present invention and are not allowed to be modified, or are limited to the exact forms disclosed herein. Rather, various modifications are possible from the teachings described above, or can be realized on the basis of the practice of the present invention. The examples are selected to illustrate the principles of the invention and its practical application so that those skilled in the art can use the invention in various aspects and in various variants suitable for the intended specific application. explained. The scope of the present invention is defined by the "claims" and their equivalents.