Biaxially stretched multilayered film

[0001] [Technical field to which the invention belongs] The present invention relates to a biaxially stretched multilayer film having an outer layer made of a polypropylene resin, particularly heat resistance, retort sterilization treatment characteristics, easy sealing property, moldability, heat shrinkage property, gas barrier property, water vapor barrier property, flexibility, etc. It relates to a well-balanced packaging film (the term "film" is used to mean that the thickness is not particularly limited and more generally includes a film having a thickness called "sheet"). [0002] The biaxially stretched multilayer film of the present invention is a casing film for filling and packaging fluid or semi-fluid foods such as sausages, solid foods such as processed meats and hams, pillow packaging films, and the like. It is particularly suitable as a film for deep drawing packaging. [0003] [Conventional technology] In recent years, technological innovation in the food packaging field has been remarkable, and there is always a demand for the most suitable packaging material for packaging, storage, transportation, etc. of each food. Further, the development of an automatic packaging system is being promoted for the purpose of increasing the production amount and reducing the cost, and the packaging material is required to have excellent suitability for the automatic packaging machine. [0004] Processed livestock products such as sausages, processed marine products such as fish sausages, processed agricultural products such as konjac and uro, fluid / semi-fluid foods such as cooked foods, and solid foods such as processed meats and hams. In the field of casing films, pillow packaging films or sheets, and deep draw packaging films for filling and packaging, single-layer or multilayer films made of various synthetic resins are widely used. For example, in the field of casing films, a film made of a resin composition of nylon and a polyolefin-based resin, or a multilayer film in which a nylon layer and a polyolefin-based resin layer are laminated is often used. [0005] Among these, a multilayer film in which a nylon layer and a polyethylene layer are laminated (hereinafter abbreviated as "Ny / PE film") is widely used because it has good heat-sealing properties and gas barrier properties. .. However, this Ny / PE film has a problem of lacking flexibility. Moreover, although it is possible to apply the gassho-type heat-sealing method (seal surfaces are polyethylene layers) with the polyethylene layer as the seal layer to the Ny / PE film, the so-called envelope sticking type seal method (seal surface is a nylon layer). And polyethylene layer) cannot be applied. Therefore, Ny / PE film could not be applied to an automatic filling and packaging machine equipped with an envelope sticking type sealing mechanism. [0006] Several proposals have been made for polyamide-based resin compositions that satisfy various properties as a casing film with a single layer. For example, Japanese Patent Application Laid-Open No. 4-122732 describes an aromatic copolyamide (hereinafter abbreviated as "nylon 6I / 6T") composed of nylon 6, and a polycondensate of hexamethylenediamine, terephthalic acid, and isophthalic acid. Casing films formed from the mixture have been proposed. However, when this casing film is manufactured by the inflation method, the internal stress of the tubular parison at the time of inflation stretching is high, so that the air pressure in the stretching bubble becomes high, the bubble bursts frequently, and stable inflation stretching is performed. Was difficult. Moreover, when the casing film is filled with sausage by a conventional method, boil-cooked, and then cooled, there is a problem that the surface of the product is wrinkled and the product dimensions are difficult to stabilize. Further, this casing film has high rigidity and poor workability such as shirring and filling property. [0007] In the above-mentioned polyamide-based resin composition, when an aromatic polyamide composed of adipic acid and methoxylylenediamine (hereinafter abbreviated as "nylon MXD6") is used instead of nylon 6I / 6T, the above-mentioned tendency becomes more remarkable. Become. Further, when a film or sheet blow-molded using nylon MXD6 is deep-drawn, the elongation from the bottom corner of the deep-drawing die to the side wall is not uniform, and deep-drawing is difficult. [0008] [Problems to be Solved by the Invention] An object of the present invention is to have an excellent balance of heat resistance, retort sterilization treatment properties, easy sealing property, moldability, heat shrinkage property, gas barrier property, water vapor barrier property, flexibility, etc., and is suitable for use as a packaging material. It is an object of the present invention to provide an axially stretched multilayer film. [0009] Another object of the present invention is to provide a package obtained by forming a casing with the biaxially stretched multilayer film as described above and accommodating a fluid or semi-fluid substance. [0010] [Means to solve problems] According to the present invention, this is a biaxially stretched multilayer film formed by biaxially stretching a laminated film consisting of at least three layers having an intermediate layer sandwiched between outer layers made of a pair of thermoplastic resins.<u style="single">Is good</u>It is made of a gas barrier resin containing a mixture of a fragrant diamine polymer and an aromatic diamine copolymer, at least one outer layer is made of a polypropylene resin, and an adhesive layer is provided between the intermediate layer and the outer layer. Is a biaxial material composed of a mixed resin in which the mixing ratio of the polypropylene-based resin and the polyethylene-based resin on a weight basis is 80/20 to 20/80, and at least one of the polypropylene-based resin and the polyethylene-based resin contains a functional group. Stretched multilayer film is provided<u style="single">。</u> 【0011】<u style="single">Also</u>Another of the present invention<u style="single">According to the preferred embodiment</u>For example<u style="single">the above</u>Of the pair of outer layers, the outer layer in contact with the processed meat food is a resin containing 90 to 80% by weight of polypropylene resin and 10 to 20% by weight of polyethylene resin, and is corona-treated.<u style="single">。</u>[0013] According to still another aspect of the present invention, there is provided a package in which a casing is formed by the biaxially stretched multilayer film and a fluid or semi-fluid substance is contained therein. [0014] The present invention corresponds to the selected invention of the invention according to WO98 / 29250. [0015] BEST MODE FOR CARRYING OUT THE INVENTION (Polypropylene resin) One of the main features of the biaxially stretched multilayer film of the present invention is that at least one of the outer layers made of a pair of thermoplastic resins is made of a polypropylene resin. [0016] The polypropylene-based resin includes a propylene homopolymer (polypropylene) or a copolymer of propylene having a propylene content of 90% by weight or more and another olefin having 4 or less carbon atoms, and these polypropylene-based resins are used alone. Or, it is used in the form of a mixture of a polypropylene-based resin containing 50% by weight or more, preferably 60% by weight or more of a polypropylene-based resin and another thermoplastic resin. [0017] Preferred examples of the polypropylene-based resin include a propylene / ethylene copolymer and a propylene / ethylene / butene-1 copolymer, more preferably a resin having a melting point of 130 to 155 ° C, particularly 130 to 140 ° C. Can be mentioned. [0018] (Other thermoplastic resins) Preferred examples of other thermoplastic resins are ethylene homopolymers (polyethylene) or ethylenes having an ethylene content of 75% by weight or more, more preferably 90% by weight or more, and other olefins having 8 or less carbon atoms. Examples thereof include polyethylene-based resins made of polymers. Preferred examples of polyethylene-based resins are homopolymers such as low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE); linear low density polyethylene (LLDPE), ultra low density polyethylene (VLDPE). ) And other polyethylene / α-olefin copolymers (complexes commercially available from Dow Chemical Co., Ltd. using metallocene catalysts such as "Affinity" and "Elite", especially with a density of 0.900 g / cm.³The above is preferable). [0019] Preferred examples of other thermoplastic resins other than polyethylene-based resins include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), and ethylene. -Examples include a methacrylic acid copolymer (EMAA), an ethylene / acrylic acid copolymer (EAA), an ethylene-based copolymer containing a polar group such as an ionomer, and the like. [0020] (Outer layer) If the propylene content in the polypropylene-based resin constituting the outer layer is less than 90% by weight, or if the polypropylene-based resin content in the outer layer is less than 50% by weight, the heat resistance associated with using the polypropylene-based resin in the outer layer, suitability for retort sterilization, etc. The improvement effect becomes poor. [0021] [0021] A particularly preferable composition of the outer layer is to use a mixture of 95 to 70% by weight of polypropylene resin, particularly 90 to 80% by weight, and 5 to 30% by weight of polyethylene resin, particularly 10 to 20% by weight. As a result, when the outer layer is corona-treated, a remarkably high improvement in meat adhesion can be obtained. In particular, in the case of processed foods such as fish sausage, which are difficult to adhere to meat, corona treatment is effective, and if the polypropylene resin exceeds 95% by weight, the effect of corona treatment tends to be insufficient. On the other hand, if the amount of the polyethylene-based resin is too large, the stretchability of the intermediate layer with the polyamide-based resin composition is slightly lowered, and the retort suitability tends to be insufficient. [0022] (Other outer layers) It is preferable that the pair of outer layers are both made of a polypropylene resin or a thermoplastic resin composition containing 50% by weight or more of the polypropylene resin from the viewpoint of improving the suitability for envelope sticking type sealing and the suitability for retort sterilization treatment. However, one of the pair of outer layers may be composed of a thermoplastic resin other than the polypropylene-based resin. As the thermoplastic resin at this time, those exemplified in the above section (other thermoplastic resins) are preferably used, and polyester resins such as polyethylene terephthalate are also preferably used. [0023] The other outer layer preferably constitutes an outer layer (outer surface layer) opposite to the outer layer (so-called inner surface layer) in contact with the contents made of (semi) fluid-like material or the like. In this outer layer, for example, a granular lubricant composed of silica particles having a particle size of 10 μm or less is contained at a ratio of 1000 ppm or less, preferably 200 to 800 ppm to improve the slipperiness of the obtained multilayer film, and pillow packaging is performed. It is also preferable to improve the aptitude. [0024] (Middle layer) The intermediate layer is composed of aromatic diamine copolymers and aromatics in order to appropriately set the gas barrier property, stretchability, drop or piercing of the package, or the strength at the time of shuttering at high temperature or in the retort. It is preferably composed of a polyamide resin containing a diamine polymer. [0025] (Aromatic diamine) The aromatic diamine, xylylenediamine are preferred, particularly m-xylylenediamine alone or m-xylylenediamine 60 wt% or more, and preferably 70 wt% or more, para-xylylene amine emissions 40% by weight or less, preferably 30 A diamine mixture with a weight% or less is preferably used. [0026] (Aromatic diamine polymer) Examples of the aromatic diamine polymer include the above-mentioned aromatic diamine and an aromatic or aliphatic dicarboxylic acid, preferably an aliphatic dicarboxylic acid, and more preferably an aliphatic dicarboxylic acid having 6 to 12 carbon atoms, for example, adipic acid. A polyamide resin synthesized by a polycondensation reaction with an acid, sebatic acid, suberic acid, undecanedioic acid, dodecanedioic acid and the like is used. More specifically, homopolymers such as polymethoxylylen adipamide, polymethoxylylene sevacamide, and polymethoxylylens veramide, metaxylylene / paraxylylene adipamide copolymer, and metaxylylene / paraxylylenepi. Examples thereof include melamide copolymers, metaxylylene / paraxylylene azelamide copolymers, metaxylylene / paraxylylene adipamide / sebacamide copolymers and the like. Of these, polymethaxylylene adipamide (MXD6) is particularly preferred. These aromatic diamine polymers impart properties such as gas barrier properties to the biaxially stretched multilayer film of the present invention. [0027] (Aromatic diamine copolymer) The aromatic diamine copolymer includes a condensation unit (for example, metaxylylene adipamide) constituting the above-mentioned aromatic diamine polymer and another polyamide, preferably an aliphatic polyamide such as nylon 6, nylon. Co-condensation polymers with one or more of the condensation units such as 11, nylon 12, nylon 66, nylon 69, nylon 610, etc. are mentioned, and the content of the aromatic diamine polymer condensation unit in the aromatic diamine copolymer is 4. It is preferably in the range of ~ 40% by weight. If it is less than 4% by weight, the oxygen gas barrier property of the product multilayer film is lowered, and if it exceeds 40% by weight, the rigidity of the obtained multilayer film becomes too large, and the moldability, heat shrinkage and flexibility tend to be inferior. Preferred examples of the aromatic diamine copolymer include nylon 6/12 / MXD6, nylon 610 / MXD6, nylon 66/610 / MXD6 and the like. [0028] The aromatic diamine copolymer can slow down the crystallization rate of the crystalline polyamide resin composition containing the aromatic diamine polymer as a main component and facilitate the heat stretching operation. That is, the aromatic diamine copolymer contributes to the improvement of stretchability, film forming property, and high frequency sealing property. In addition, this aromatic diamine copolymer improves the flexibility of the film or sheet, thereby improving the filling property of sausages and the like, and further, shirring suitability, ring processability, film cutability, pillow packaging. Improves secondary workability such as machine suitability and deep draw moldability. This aromatic diamine copolymer improves the gas barrier property of the film or sheet to some extent. Blends of aliphatic polyamides such as nylon 6 and aromatic polyamides, rather than copolymers, do not balance these characteristics. [0029] The polyamide-based resin composition constituting the intermediate layer contains 50 to 99% by weight of the aromatic diamine polymer, particularly 60 to 95% by weight, and 1 to 50% by weight of the aromatic diamine copolymer described above. In particular, it is preferably formed by mixing at a ratio of 5 to 40% by weight. If the blending ratio of the aromatic diamine copolymer is too small, the effect of delaying the crystallization rate of the polyamide resin composition becomes small, and conversely, if it is too large, the film becomes too soft, resulting in a casing film made of a film. When filling sausage or the like, the film is stretched due to the filling pressure, the dimensions of the product are not constant, the shape varies, and the dimensional stability and the shape stability are impaired. [0030] (Other polyamides, etc.) In addition to the above aromatic diamine polymer and aromatic diamine copolymer, the polyamide resin composition constituting the intermediate layer contains up to 20% by weight of an aliphatic polyamide and up to 20% by weight of an amorphous polyamide. , Arbitrary components such as polyolefin resins up to 30% by weight can be included up to 30% by weight in total. [0031] Examples of the aliphatic polyamide include nylon 6, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 6/66, nylon 6/12, and the like. [0032] Amorphous polyamide is a polyamide having an aromatic ring in the main chain and / or side chain and having no crystallinity or very poor crystallinity. Specific examples thereof include a polycondensate of a dicarboxylic acid such as terephthalic acid and isophthalic acid and a diamine such as hexamethylenediamine, or a copolymer thereof. For example, a polyamide (nylon 6I / 6T) obtained by polycondensing a dicarboxylic acid composed of 10 to 50% by weight of terephthalic acid and 90 to 50% by weight of isophthalic acid and hexamethylenediamine can be mentioned. [0033] Examples of the polyolefin-based resin mixed in the intermediate layer include ethylene and α-olefin homopolymers such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and polypropylene; linear low-density polyethylene (LLDPE), ultra-low density. Copolymer of ethylene such as polyethylene (VLDPE) and α-olefin (commodator obtained by using metallocene catalyst such as Affinity, trade name); Ionomer resin, polyamide-modified ionomer resin, ethylene / vinyl acetate copolymer, Examples thereof include ethylene / ethyl acrylate copolymer, ethylene / acrylic acid copolymer, ethylene / methyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / methacrylic acid copolymer and the like. These polyolefin-based resins can be used alone or in combination of two or more. [0034] The polyolefin resin to be mixed in the polyamide resin composition is an ethylene / acrylic acid copolymer, an ethylene copolymer such as an ethylene / methacrylic acid copolymer, and a polyamide-modified ionomer resin mixed with each polyamide component. It is preferable from the viewpoint of sex. [0035] Polyamide-modified ionomer resin is an ionomer in which a copolymer of ethylene and α, β-unsaturated carboxylic acid is ionized with metal ions such as zinc, lithium, potassium, magnesium, calcium, and sodium, and polyamide is added and mixed. It is a resin obtained by melt-kneading and modifying at a high temperature of 200 to 350 ° C. Examples of the polyamide used here include nylon 6, nylon 66, nylon 6/66, nylon 6/10, nylon 6/12, nylon 11, nylon 12, and a mixture of two or more of these. .. Among these, nylon 6 and its copolymer are preferable. [0036] The inclusion of these polyolefin resins reduces the water permeability of the intermediate layer, and thus the product multilayer film, and prevents weight loss of the contents such as sausages through the packaging film during storage of the packaged product. It is effective for. The blending ratio of the polyolefin-based resin is usually 10 to 30% by weight in the polyamide-based resin composition. If this blending ratio is too small, the moisture permeability of the film becomes too large, and when sausages and the like are packaged and stored, the content is greatly reduced. If this blending ratio is too large, in addition to poor stretchability, oxygen permeability increases, and putrefaction due to oxidative deterioration of the contents is likely to occur. [0037] (Polyamide-based resin composition) The polyamide-based resin composition constituting the intermediate layer can be prepared by mixing each component by a known method. For example, a uniform composition can be obtained by mixing raw materials such as pellets, granules, and powders of each polymer at the time of extrusion molding. If desired, various additives such as plasticizers, stabilizers, lubricants, antioxidants, pigments, and dyes can be added to the polyamide-based resin composition as long as the characteristics of the film are not impaired. [0038] (Adhesive resin layer) The multilayer film of the present invention comprises at least the above-mentioned pair of outer layers and intermediate layers.<u style="single">, Ko</u>An adhesive resin layer is interposed between these layers to form a multilayer film with good adhesion between layers.<u style="single">。</u>[0040] Especially at least one<u style="single">An unsaturated carboxylic acid such as maleic acid, fumaric acid, or acrylic acid, an acid anhydride, or an ester is graft-copolymerized to introduce a functional group.</u>The adhesive resin layer composed of a mixture of 20 to 80% by weight of the modified polypropylene resin and 80 to 20% by weight of the polyethylene resin exhibits strong adhesive strength and also exhibits strong heat resistance even in retort sterilization treatment and the like. It is preferably used. If the mixing ratio of the (modified) polypropylene-based resin is too large, the polypropylene-based resin layer and the polyamide-based resin composition layer are likely to be peeled off at the creases of the casing or the creases during shirring. On the other hand, if the mixing ratio of the (modified) polyethylene-based resin is too large, delamination may occur during the stretching process, and the polypropylene-based resin layer or the polyamide-based resin layer may be slightly scratched and burst. [0041] (Other resin layer) In addition to the above, the multilayer film of the present invention has other resin layers and additional resin layers such as a saponified (EVOH) layer of an ethylene-vinyl acetate copolymer and a gas barrier resin layer such as nylon MXD6. Etc. may be adjacent to the intermediate layer, for example, via an adhesive resin layer, if necessary. [0042] (Film manufacturing) The method for forming a multilayer film of the present invention is not particularly limited, but the multilayer film is formed as a multilayer film by a coextrusion or a laminating method. [0043] The film forming method is not particularly limited, and for example, a T-die method, an inflation method, or the like can be adopted. Usually, the inflation method is used. The melting temperature of the resin is usually 160 to 220 ° C, preferably 180 to 200 ° C for the polypropylene-based resin constituting each layer, and usually 300 ° C for the polyamide-based resin constituting the intermediate layer. Below, it is preferably 240 to 280 ° C, more preferably 250 to 270 ° C. The unstretched film obtained by the T-die method is usually biaxially stretched simultaneously or sequentially by the tenter method at a stretching temperature equal to or lower than the melting point of the polypropylene resin (for example, 130 ° C or lower). The tubular parison obtained by the inflation method is biaxially stretched by blowing air at a stretching temperature equal to or lower than the melting point of the polypropylene resin (for example, 130 ° C or lower). The draw ratio is usually 2.0 to 10.0 times, preferably 2.2 to 8.0 times, and more preferably 2.2 to 6.0 times, respectively, in both the vertical and horizontal directions. By stretching, dimensional stability such as appropriate heat shrinkage and creep characteristics can be obtained. [0044] (Laminated structure) Through the above-mentioned production method, the biaxially stretched multilayer film of the present invention includes a single layer having the following thickness including an arbitrary layer, and is formed as a multilayer film having a total thickness of 10 to 250 μm, preferably 15 to 200 μm. Ru: First outer layer (outer surface layer in the case of a cylinder): 5 to 100 μm, preferably 5 to 80 μm Intermediate layer: 2-50 μm, preferably 2-20 μm Gas barrier layer (optional): 1 to 20 μm, preferably 2 to 10 μm Second outer layer (inner surface layer in the case of a tubular body): 5 to 100 μm, preferably 5 to 80 μm Adhesive resin layer (optional): 0.5 to 30 μm, preferably 1 to 20 μm [0045] (Characteristic) In the packaging of processed meat products, from the viewpoint of product aesthetics, we dislike the occurrence of wrinkles in the packaging products such as sausages. In order to prevent the occurrence of wrinkles, it is necessary to keep the film in a taut state by shrinking the film due to heat during the boil cooking or sterilization process. The stretched film of the present invention usually has a shrinkage rate (hot water shrinkage rate) of 5% or more, preferably 8% or more, more preferably 10% or more in each of the vertical and horizontal directions when immersed in hot water at 80 ° C. .. [0046] In the casing film of the present invention, when the hot water shrinkage rate at 80 ° C is less than 5%, for example, a fluid or semi-fluid sausage is filled and cooked, and then wrinkles are generated on the product surface, which is preferable. Absent. [0047] Hot water creep at 80 ° C. for 10 seconds can be used as an evaluation standard for the dimensional stability of the film. The hot water creep of the stretched film of the present invention is preferably 20% or less, more preferably 18% or less. If the hot water creep is too large, for example, after filling and cooking the sausage, the variation in product dimensions becomes too large, which is not preferable. Hot water creep is a film with a trial width of 20 mm and a trial length of 100 mm, and a load of 1 kg / mm.²It is measured as the elongation rate with respect to the original film length when it is immersed in warm water at 80 ° C for 10 seconds. [0048] The film of the present invention has a haze of preferably 20% or less. Due to the low degree of cloudiness, the contents such as sausage can be visually recognized from the outside of the packaging film. [0049] The film or sheet of the present invention has an oxygen permeability of 200 cm measured under conditions of 30 ° C and 80% RH (relative humidity).³(NTP) / m² Day atm or less, more preferably 135 cm³(NTP) / m² Day atm or less, and the permeation rate measured at 40 ° C and 90% RH is preferably 70 g / m.²-It is less than a day, and during long-term storage of packaged foods, it is possible to suppress spoilage and loss of water due to oxygen in the contents, and to retain the flavor of the contents. [0050] The film of the present invention has excellent high frequency sealing properties. Conventionally, many films made of a resin composition of a polyamide and a polyolefin-based resin or the like have been proposed and used, but there is no particular mention of a high-frequency seal. As a result of diligent studies on this sealing property, the present inventors perform high-frequency sealing of a film made of a single polyamide, for example, a nylon 6 film, using an automatic filling and packaging machine (KAP, an automatic filling and packaging machine for sausages manufactured by Kureha Chemical Co., Ltd.). Then, a discharge was generated in the seal portion, and good sealing performance could not be obtained. On the other hand, the film having an outer layer made of the polypropylene-based resin and an intermediate layer made of the polyamide-based resin composition of the present invention is discharged even if high-frequency sealing is performed using an automatic filling and packaging machine having a high-frequency sealing mechanism. No stable continuous sealing is possible. The film of the present invention has good sealing properties such as heat sealing and ultrasonic sealing as well as high frequency sealing. [0051] The multilayer film of the present invention can be suitably used as a casing film. The multilayer film of the present invention has good film forming property and stretchability during film production, and also has appropriate flexibility, hot water shrinkage rate, creep property, toughness, gas barrier property, dimensional stability, and suitability for automatic packaging machine. Because it has such characteristics, it is filled with processed livestock products such as ham and sausage, processed marine products such as fish sausage, processed agricultural products such as konjac and uro, and fluid / semi-fluid foods such as cooked foods. It is particularly suitable as a casing film for packaging. [0052] In particular, prior to filling the contents of processed meat products such as sausages and ham, the outer layer surface in contact with the contents is corona-treated to improve the so-called meat adhesion of the film, and at the interface between the film and the contents. It is preferable to prevent the formation of a liquid pool from the viewpoint of maintaining the quality of the contents as well as the appearance of the packaged product. [0053] Corona processing generally uses a corona generator having a high-frequency power source equipped with a high-frequency transmitter and a high-voltage transformer. For example, the output performance is a voltage of 18 kV or less, a power of 4 kW or less, a frequency of 5 to 120 kHz, a waveform, preferably. By arranging the film on the processing roll (silicon coating) surface with sinusoidal voltage and current and treating the surface of the corona discharge film between the discharge electrode and the processing roll, the surface tension of the processing surface is 34 dyne / cm.²Above, especially 36dyne / cm²The above is preferable. [0054] The multilayer film of the present invention is also suitable for a mode in which a casing is formed by a back seal (a so-called envelope-attached seal in which edges are overlapped so that a pair of outer layers are in contact with each other). For example, a back seal forms a tubular casing with a folding width of 260 mm or less, preferably 15 to 160 mm and a seal width of 0.1 to 15 mm, and (semi) fluid products are filled by automatic packaging and then both ends are heat-sealed. The product packaging is formed by sealing. [0055] [Example] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Each physical property measurement is as follows. [0056] (1) Oxygen permeability According to ASTM D3985-81, the measurement was performed using a MOCON OXTRAN-2 / 20 type manufactured by MODERN CONTROL under the conditions of 30 ° C and 80% RH. [0057] (2) Moisture permeability Measurements were made using MODERN CONTROL's PERMATRAN-W3 / 31 under the conditions of 40 ° C and 90% RH according to ASTM F372-73. [0058] [0058] (3) Adhesive strength between layers TOYO Using TENSILON RTM-100 type manufactured by BALDWIN, prepare a test piece with a test width of 15 mm and a test length of 100 mm, and peel off a part of the outer layer // core layer or inner layer // core layer with the cutting edge of the cutter. Using the peeled edge, the T-peeling force between the outer layer // core layer and the inner layer // core layer was measured for one sample, respectively. [0059] (4) Shrinkage rate After immersing the film in hot water at 80 ° C for 3 seconds, the shrinkage in the vertical and horizontal directions was measured. [0060] (5) Tensile elastic modulus Using TENSILON RTM-100 type manufactured by TOYO BALDWIN, the film is a test piece with a test width of 20 mm and a test length of 100 mm, and the stress at 1% tensile strain is calculated at a tensile speed of 10 mm / min. The tensile modulus in the lateral direction was measured. [0061] (6) Meat adhesion, film peeling power Made by Leotech, FUDOH RHEO Using METER, make a cut in the length direction of the sausage in a part of the test piece cut out at a width of 3 cm at right angles to the length direction of the sausage, peel the film about 2 cm in advance, chuck the part, and then chase the sausage again. Insert a rod-shaped shaft into the center of the circumference of the sausage, and peel off the length of about 3 cm at a speed of 6 cm / min so that the sausage rotates during measurement and the tensile peeling direction is always vertical during film peeling measurement. The average value of the peeling force was taken as the film peeling force. [0062] (7) Crystal melting point (Tm) The crystal melting point was measured using DSC7 manufactured by PerkinElmer. The measurement conditions were as follows: a sample of 5 to 10 mg was weighed, the resin was melted once, and the resin was held at a temperature 40 ° C higher than the melting point at that time for 2 minutes, then rapidly cooled to 0 ° C at 200 ° C / min and held for 2 minutes. Then, the temperature was raised at 20 ° C./min, and the melting peak temperature in the process was taken as the crystal melting point. [0063] (Example 1) As the composition of the multilayer film, in the 5-layer laminated film of outer layer / adhesive layer / core layer / adhesive layer / inner layer, nylon MXD6 (Polyamide MXD6 # 6007 manufactured by Mitsubishi Chemical Co., Ltd., melting point (Tm) = 240 ° C, glass transition) as the core layer. Point (Tg) = 75 ° C, Density (d) = 1.22) 95% by weight and nylon 66/610 / MXD6 (Ms Chemical, Glylon BM-18SBH, Tm = 181 ° C, Tg = 57 ° C, d = 1.12) Using a mixture with a ratio of 5% by weight, PP-based adhesive resin (manufactured by Mitsubishi Chemical Co., Ltd., Modic P504V, Tm = 140 ° C, d = 0.89, MI = 4g / 10min, Vicat softening point (Tv) ) = 100 ° C) 50% by weight and LLDPE adhesive resin (manufactured by Mitsubishi Chemical Corporation, Modic OM-101, Tm = 120 ° C, d = 0.93, MI = 3.2g / 10min, Tv = 56 ° C) 50 weight %% Mixed resin layer, 93% by weight propylene, 2% by weight ethylene and butene-1 as outer and inner layers Ethylene-propylene-butene-1 copolymer consisting of 5% by weight (Sumitomo Chemical, Sumitomo Noblene, FL851, Tm = 139 ° C, d = 0.90, MI = 6g / 10min, Tv = 128 ° C) 90% by weight And SSC polyethylene (Made by Dow Chemical Co., Ltd., Elite 5100, Tm = 121 ° C, d = 0.92, MI = 0.85g / 10min, Tv = 107 ° C) Using 10% by weight mixed resin, 4 extruders (Outer layer, inner layer, core layer; 40φ, adhesive layer; 30φ) and 4 types of 5 layers of annular die, co-extruded in a ring shape at a resin temperature of 250 ° C, cooled by water shuffling at 10 ° C, and thickness. A parison with a folding width of 850 μm and a folding width of 70 mm was obtained. Next, the parison was reheated to a surface temperature of 150 ° C with a far-infrared heater, stretched 4.5 / 4.5 times in length / width by an inflation method, and had a thickness structure of 15/2/8/2/15 μm (total thickness). A film of 42 μm) was obtained. Next, the surface of the stretched film was measured with an infrared thermometer and heat-treated at 140 ° C. to prepare the film of the present invention. The laminated resin and thickness structure of the obtained multilayer film are shown below. [0064] [Number 1]<img file="JP4397461B2_D0001.tif" />[0065] The oxygen permeability, moisture permeability, interlayer adhesive strength, shrinkage rate, and tensile elastic modulus of the obtained film were measured by the above methods, and are shown in Table 1 below together with the results of the following Examples and Comparative Examples. [0066] (Examples 2 and 3) A biaxially stretched multilayer film of the present invention was obtained in the same manner as in Example 1 except that the mixing ratio of the core layer resin was changed as follows. [0067] [Number 2]<img file="JP4397461B2_D0002.tif" /> 【0068】 (<u style="single">Example</u>4<u style="single">(Reference example)</u>) Resin composition In the PP / Ad / MXD6 + M-PA / Ad / PP 5-layer film, the adhesive resin (Ad) is a PP adhesive resin (manufactured by Mitsubishi Chemical, Modic P504V), and other than that, it is the same as in Example 1. An attempt was made to prepare a stretched polypropylene film by the manufacturing method. [0069] (Example 5) Resin composition In a 5-layer film of PP / Ad / MXD6 / Ad / PP, the adhesive resin (Ad) is 50% by weight of PP adhesive resin (Mitsubishi Chemical, Modic P504V) and LLDPE adhesive resin (Mitsubishi Chemical, Modic OM). -101) As a mixed resin of 50% by weight, an attempt was made to prepare a stretched multilayer film by the same manufacturing method as in Example 1 except that. [0070] (Comparative Examples 1 and 2) Resin composition In a 5-layer laminated film of PP / Ad / MXD6 / Ad / PP, the adhesive resin (Ad) is a PP-based adhesive resin (manufactured by Mitsubishi Chemical Corporation, Modic P504V) (Comparative Example 1), and an LLDPE-based adhesive resin (Mitsubishi). As Modic OM-101) (Comparative Example 2) manufactured by Kagaku Co., Ltd., an attempt was made to prepare a stretched polypropylene film by the same manufacturing method as in Example 1 except for the above. [0071] In Comparative Example 1, a multilayer film was obtained, but in Comparative Example 2, a multilayer film could not be obtained due to partial peeling between layers during inflation stretching and bursting of bubbles. [0072] Table 1 shows the measured values obtained only for the film of Comparative Example 1. [0073] [table 1]<img file="JP4397461B2_D0003.tif" />[0074] (Example 6) Using the film of Example 3, the paste-like livestock meat sausage is filled in a casing obtained by an automatic filling and packaging machine (manufactured by Kureha Chemical Co., Ltd., KAP2000 type) including a casing process by attaching a film to an envelope, and further 120 ° C, 15 minutes, steam pressure 2 kg / cm²Retort sterilization was performed under the condition of (gauge), and 100 cannonball-shaped sausage packages (dimensions: about 22φ x 140 mm length, weight: about 55 g / piece) were prepared. The puncture rate of the package during this retort sterilization treatment was 0%, the sausage was not spoiled after storage at room temperature for 2 weeks, and the sausage was good, and the amount of loss was as low as 0.18%. [0075] (<u style="single">Example</u>7<u style="single">(Reference example)</u>)<u style="single">Example</u>Using the film of No. 4, a casing was formed in the same manner as in Example 6, filled with livestock sausage, and retort-sterilized. The puncture rate of the package was 0%, the sausage was not spoiled after being stored at room temperature for 2 weeks, and the sausage was good, and the amount of loss was as low as 0.17%. [0076] (Example 8) Using the film of Example 5, a casing was prepared in the same manner as in Example 6, filled with livestock sausage, and retort-sterilized. The puncture rate of the package was 5%, the sausage was not spoiled after being stored at room temperature for 2 weeks, and the sausage was good, and the amount of loss was as low as 0.17%. [0077] (Comparative example 3) Using the film of Comparative Example 1, a casing was prepared in the same manner as in Example 6, filled with livestock sausage, and retort-sterilized. As a result of evaluating the puncture occurrence rate of the package, the puncture rate was 40%. [0078] (Example 9) Using the film of Example 3, the surface of the sausage package in contact with the sausage was previously corona-treated, and the surface tension of the treated surface was 36 dyne / cm.²I got the film. Using this film, a casing was formed in the same manner as in Example 6, filled with fish sausage, and retort-sterilized to obtain a fish sausage package. The obtained package has a puncture rate of 0% during retort sterilization, no sausage spoilage after storage at room temperature for 2 weeks, a low loss of 0.15%, and good meat adhesion (film peeling power; 100 g). / 3 cm width, peeling speed; 6 cm / min). [0079] [Effect of the invention] As described above, according to the present invention, not only is the balance of moldability, heat shrinkage, easy sealing, gas barrier, steam barrier, flexibility, etc. excellent, but also excellent heat resistance particularly suitable for retort sterilization. A biaxially stretched multilayer film exhibiting properties can be obtained. In particular, by using this as a casing and filling it with (semi) fluid foods such as fish meat, livestock meat, or processed products thereof, a package having excellent appearance and strength can be obtained. Obtainable.