JP4956189B2 - Shrinkable laminated film and method for producing the same - Google Patents

Description

  The present invention relates to a specific shrinkable laminated film comprising a polyamide resin layer, an adhesive resin layer, and a heat-sealable resin layer, a method for producing the same, and a method for producing the shrinkable laminated film by coextrusion.

  Various known laminated stretched films have been proposed for laminated stretched films that take advantage of the strength of polyamide resin films and the heat sealability of polyolefin resin films. These laminated stretched films are used for the packaging of processed food products such as processed meat products in the field of food, especially food products, marine products, and processed milk products such as cheese, and mainly for bag packaging, deep drawing packaging and Used as skin pack packaging.

  International Publication No. 2004/028920 pamphlet can be heat-sealed to a slightly shrinkable film (A) having a residual heat shrinkage rate at 100 ° C. of greater than 0 and 15% or less as a bottom material and the slightly shrinkable film (A). Discloses an invention relating to a deep drawing method using a cover film (B). The micro-shrinkable film (A) is stretched at 80 to 95 ° C. in the MD direction by 2.5 to 4.0 times and in the TD direction by 2.5 to 4.0 times, and then stretched at 70 to 98 ° C. It is described that it is obtained by shrinking 10 to 40% in the direction and 10 to 40% in the TD direction.

  Japanese Unexamined Patent Publication No. 63-214445 (Japanese Patent Publication No. 8-5170) discloses a polyolefin system biaxially stretched on one or both sides of a polyamide-based heat-shrinkable base film mainly composed of a specific polyamide-based copolymer. As a heat-shrinkable laminate material laminated with a heat-shrinkable sealant film, a film in which a biaxially stretched L-LDPE film is dry-laminated on one side and both sides of a biaxially stretched nylon 6 / 6-6 film is described.

  JP-A-55-130743 (JP-B-61-53218) relaxes a laminated biaxially stretched film of a polyamide resin sheet and a polyolefin sheet at a heat treatment temperature of 50 to 90 ° C. and 2 to 15% in length and width respectively. The heat treated film is described.

  The present invention, when using a shrinkable laminated film for packaging food such as fish having sharp protrusions, the strength of the film (pinhole resistance) is high, content deterioration due to the occurrence of pinholes can be prevented, In addition, when packaging foods and ingredients that generate a lot of carbon dioxide such as cheese, it is possible to prevent the package from swelling due to the generated gas and keep the package exterior clean, which is a problem when used as a deep drawing film. To provide a shrinkable laminated film with improved properties other than film strength, such as collapse of deep-drawn corners, wrinkles during molding, curling of flanges, etc., and a method for producing the same Objective.

  As a result of intensive studies to solve the above problems, the present inventors have stretched a coextruded laminated film composed of a polyamide resin layer, an adhesive resin layer, and a heat-sealable resin layer, and then have 20 It has been found that a shrinkable laminated film obtained by heat relaxation of ˜40% exhibits low values in both length and breadth with high film strength and a hot water shrinkage of 90 ° C., and the present invention has been completed.

Namely, shrinkable laminated film of the present invention, the outer layer of a polyamide resin, an intermediate layer consisting of acid-modified polyolefin, and a shrinkable laminated film consisting of only three layers of the inner layer made of polyolefin resin, the inflation method It is a stretched coextruded laminated film, and its hot water shrinkage at 90 ° C. is 2 to 15% in length and breadth, and its carbon dioxide permeability at 30 ° C. and 80% relative humidity is 500 cm ³ / m ² · day · atm. The above is for deep drawing .

Further, in the shrinkable laminated film of the present invention, and tensile modulus at 2 3 ° C. is not more than 600 MPa, have preferred that the piercing strength at 23 ° C. is not less than 10 N.

Method for producing a shrinkable laminated film of the present invention, the outer layer of a polyamide resin, an intermediate layer consisting of acid-modified polyolefin, and a coextruded multilayer film of the tubular body consisting of only three layers of the inner layer made of a polyolefin resin, In this method, the film is stretched 2 to 4 times in the vertical and horizontal directions by an inflation method , and then thermally relaxed by 20 to 40% in the vertical and horizontal directions with steam or warm water .

  Embodiments of the present invention will be described below.

  The polyamide resin constituting the layer made of the polyamide resin of the shrinkable laminated film of the present invention (hereinafter sometimes referred to as the polyamide resin layer) includes nylon 6, nylon 66, nylon 69, nylon 610, nylon 612, nylon 11 Aliphatic polyamide polymers such as nylon 12, nylon 6-66 (representing a copolymer of nylon 6 and nylon 66, the same shall apply hereinafter), nylon 6-10, nylon 6-12, nylon 6-69, Examples thereof include aliphatic polyamide copolymers such as nylon 6-610 and nylon 66-69. Among these, nylon 6-66 and nylon 6-12 are particularly preferable in terms of moldability. These aliphatic polyamide (co) polymers can be used alone or in combination of two or more.

  Further, blends of these aliphatic polyamide (co) polymers with aromatic polyamides as the main component are also used. Here, the aromatic polyamide means one in which at least one of diamine and dicarboxylic acid has an aromatic unit, and particularly preferably copolyamide. Examples thereof include a copolymer of an aliphatic nylon such as nylon 66-610-MXD6 (MXD6 is an abbreviation for metaxylylene adipamide) and an aromatic polyamide containing an aromatic diamine unit, nylon 6I, nylon 66- 69-6I (6I is an abbreviation for hexamethylene isophthalamide), nylon 6-6I, nylon 6I-6T (6T is an abbreviation for hexamethylene terephthalamide) and other copolymers containing aromatic carboxylic acid units Examples thereof include copolymers with aromatic polyamides.

  These polyamide resins are preferably used singly or mixed to have a melting point of 160 to 210 ° C.

  The polyamide resin layer is made of a polyamide resin having a melting point that is preferably about 15 ° C. or higher, more preferably 20 ° C. or higher, and particularly preferably 60 ° C. or higher than the film heating temperature during secondary molding. Those containing a polyamide resin layer having a melting point of less than the film heating temperature + 15 ° C. cause plastic deformation when melted at the time of packaging, and the film recoverability tends to be insufficient. As a result, wrinkles are likely to occur after packaging.

  The heat-sealable resin constituting the heat-sealable resin layer (hereinafter sometimes referred to as a heat-sealable resin layer) may be any resin that can be heat-sealed. Polymer, linear ultra-low density polyethylene, linear low density polyethylene (the above is either Zigler-Natta type catalyst, metallocene type catalyst, constrained geometric catalyst by Dow, or phenoxyimine complex type catalyst) Low density polyethylene polymerized by high pressure method, ethylene-vinyl acetate copolymer, ionomer resin, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid-unsaturated carboxylic acid. Polyolefin resins such as acid (ester) copolymers and ethylene-ethyl acrylate copolymers ( Styrene copolymerizable with 30 wt% or less of a vinyl comonomer) is preferably used. These may be used alone or in combination of two or more.

  Moreover, it is preferable that melting | fusing point of resin used for a heat sealable resin layer is less than melting | fusing point of resin which comprises an outer layer, for example, comprises a polyamide resin layer. When the melting point of the resin used for the heat-sealable resin layer is higher than the melting point of the resin used for the outer polyamide resin layer, the outer layer also melts when the inner surface melts during sealing after packaging, making it difficult to seal Become.

  The heat-sealable resin preferably has a melting point of 150 ° C. or lower, more preferably 135 to 90 ° C.

  In a preferred embodiment of the present invention, the polyamide resin layer and the heat-sealable resin layer are bonded by a layer made of an adhesive resin (hereinafter sometimes referred to as an adhesive resin layer). As adhesive resins, ethylene / ethyl acrylate copolymer (EEA), ethylene / acrylic acid copolymer (EAA), ethylene / methacrylic acid copolymer (EMAA), ionomer (IO), acid-modified polyolefin (olefins) Or a copolymer thereof, such as a reaction product with an unsaturated carboxylic acid such as maleic acid or fumaric acid, an unsaturated carboxylic acid anhydride, an unsaturated carboxylic acid ester or a metal salt, such as acid-modified VLDPE (Mod-VL ), Acid-modified LLDPE, acid-modified EEA, acid-modified EVA, acid-modified PP, acid-modified PP-Et) and the like. Preferable examples include acid-modified polyolefins modified with acids such as maleic acid or anhydrides thereof.

  If there is no adhesive resin layer, peeling between the polyamide resin layer and the heat-sealable resin layer is likely to occur. For example, the polyamide resin layer is a resin layer mainly composed of nylon 6, nylon 6-66 (copolymerization ratio 85-15% by weight), nylon 6-12 (copolymerization ratio 90-10% by weight), and the like, and a heat seal resin. When the layer is a two-layer laminated film using polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, etc., peeling may easily occur between the two layers when an impact is applied to the film.

  In the above layer structure, a lubricant or an antistatic agent can be added to any layer. Examples of the lubricant used include hydrocarbon lubricants, fatty acid lubricants, aliphatic amide lubricants, ester lubricants, metal soaps, and the like. The lubricant may be liquid or solid. Specific examples of the hydrocarbon lubricant include liquid paraffin, natural paraffin, polyethylene wax, and micro wax. Examples of fatty acid lubricants include stearic acid and lauric acid. Aliphatic amide lubricants include stearic acid amide, palmitic acid amide, N-oleyl palmitic acid amide, behenic acid amide, erucic acid amide, arachidic acid amide, oleic acid amide, erucic acid amide, methylene bisstearamide, ethylene Examples thereof include bisstearoamide. Examples of ester lubricants include butyl stearate, hydrogenated castor oil, ethylene glycol monostearate, and stearic acid monoglyceride. The metal soap is derived from a fatty acid having 12 to 30 carbon atoms, and representative examples thereof include zinc stearate and calcium stearate. Among these lubricants, fatty acid amide lubricants and metal soaps are preferably used from the viewpoint of excellent compatibility with polyolefin resins.

  As the inorganic lubricant (anti-blocking agent), known ones such as silica and zeolite can be added to the outer layer and / or the inner layer.

  Lubricants such as aliphatic amides and silica can be added in the form of a masterbatch. The preferable addition amount is 0.1 to 10% by weight in the master batch with respect to the resin of the layer to be added in the case of the master batch containing 20% by weight of the lubricant.

  As the antistatic agent, a surfactant is preferably used. As the surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant and a mixture thereof can be used. The antistatic agent is added in an amount of 0.05 to 2% by weight, more preferably 0.1 to 1% by weight, based on the resin of the layer to be added.

  The shrinkable laminated film of the present invention is obtained, for example, as follows.

  Tubular body of outer layer made of polyamide resin, intermediate layer made of adhesive resin, and heat-sealable resin layer made of heat-sealable resin through an annular die from the number of extruders corresponding to the number of laminated resin types constituting the laminated film ( (Parison) is co-extruded and taken up with a pinch roller while cooling to a temperature lower than the melting point of the main resin in each layer, preferably 40 ° C. or less, with a water bath or the like. Next, it is introduced into a hot water bath of, for example, 80 to 95 ° C. below the melting point of the main resin occupying each layer while enclosing an opening agent typified by soybean oil or the like into the taken-up tubular body film as necessary. Then, the heated tubular film is drawn upward, and a bubble-shaped tubular body is formed by air introduced between a pair of pinch rollers, and cooled with an air ring of 10 to 20 ° C. ) And the transverse direction (TD), respectively, 2 to 4 times, preferably 2.8 to 3.5 times each.

  Next, the stretched tubular body film is drawn downward, and a bubble-like tubular body is formed again by the air introduced into the pair of pinch rollers, and held in the heat treatment cylinder. Then, steam is sprayed from the outlet of the heat treatment tube (or sprayed with warm water), and the tubular film after biaxial stretching is preferably 60 to 98 ° C, more preferably 70 to 95 ° C, most preferably 75 to At 95 ° C., heat treatment is preferably performed for about 1 to 20 seconds, more preferably about 1.5 to 10 seconds, and the tubular film is 20 to 40% each in the machine direction (MD) and the transverse direction (TD), preferably each Heat relax 20-30% in the direction. The tubular film after the heat treatment corresponds to the film used in the present invention, and is wound on a winding roll.

  When the stretching is performed at a lower stretching ratio (less than 2 times), the necessary film strength cannot be obtained after the heat treatment, and the uneven thickness of the film also increases, so that packaging suitability is difficult to obtain. On the other hand, when the draw ratio exceeds 4 times, in the case of the above-described inflation stretching, the bubble bursts, and in the case of the conventional tenter stretching, the film is broken and it becomes difficult to produce a stretched film. Thermal relaxation tends to be difficult to increase the relaxation rate when a medium with a small heat capacity such as heated air or a lower heat treatment temperature of less than 60 ° C. is used, while high temperatures exceeding 100 ° C. When heat-treating, the heat-sealable resin tends to melt, and as a result, the orientation of the heat-sealable resin layer is broken and it tends to be difficult to obtain excellent strength. Here, the heat treatment for heat relaxation can be performed by infrared heating, air (blow) heating, steam heating or the like, but steam heating is preferable when the polyamide resin layer is provided as in the present invention.

  If the relaxation rate during heat treatment is less than 20%, the hot water shrinkage at 90 ° C may exceed 15%, and the shrinkage stress becomes too large. In the case of bag packaging, surface sterilization, boil sterilization, etc. are performed. In such a case, the contents are crushed, and in deep-drawn packaging, the contents, particularly the corners, are crushed during vacuum sealing. When the relaxation rate during the heat treatment exceeds 40%, for example, when forming an inflation film, the hot water shrinkage rate is too low, the bubbles are not stable, easily cause uneven spots or thick spots, and the transparency of the film is poor. Become.

  The tensile elastic modulus of the shrinkable laminated film of the present invention is preferably 600 MPa or less at 23 ° C. If the tensile modulus is too high, the fit with the contents and the self-weld property are lacking, and the filled contents tend to be crushed.

  The puncture strength is preferably 10 N or more, more preferably 15 N or more, and most preferably 20 N or more at 23 ° C. If this value is too low, it tends to lead to pinholes and bag breakage due to impact.

  The shrinkable laminated film obtained as described above is obtained as a result of the subsequent high thermal relaxation treatment while maintaining a high basic strength represented by tensile strength as a result of the high stretching treatment of the polyamide resin layer. The heat shrinkability is inevitably lowered, and as a result, the seal portion does not curl more than necessary and the appearance is improved. In addition, when the deep-drawn portion efficiently expresses the heat shrinkage rate, it is possible to improve the appearance such as prevention of wrinkles in the packaged product.

  In the present invention, the 90 ° C. hot water shrinkage suitable as a more specific packaging material is 2 to 15%, preferably 2 to 10%. The heat shrinkage rate in such a stretch-oriented laminated film can be set to the required 90 ° C. hot water shrinkage rate by adjusting the relaxation rate in relation to the stretch orientation ratio. When the heat shrinkage ratio in such a stretch-oriented laminated film is less than 2%, for example, when deep drawing is performed, there are many wrinkles in boil cooking after filling the contents, and the tight fit property to the contents is unsatisfactory. It becomes.

The carbon dioxide gas permeability of the obtained shrinkable laminated film is 300 cm ³ / m ² · day · atm or more at 30 ° C. and 80% relative humidity, preferably 400 cm ³ / m ² · day · atm or more, and more Preferably it is 500 cm < ³ > / m < ² > * day * atm or more. If the carbon dioxide gas permeability is less than 300 cm ³ / m ² · day · atm, when packaging foods such as natural cheese and kimchi that generate carbon dioxide during fermentation, the package expands with gas and may burst in some cases To do.

On the other hand, when the content of the mold causes mold generation by contact with air (oxygen gas), the oxygen gas permeability is preferably 30 ° C. and a relative humidity of 80% in order to prevent mold generation. Is 500 cm ³ / m ² · day · atm or less, more preferably 400 cm ³ / m ² · day · atm or less, and most preferably 300 cm ³ / m ² · day · atm or less.

  As the shrinkable laminated film, the thickness (total thickness) of all layers is preferably in the range of 15 to 150 μm, more preferably 20 to 120 μm. More specifically, the polyamide resin layer preferably has a thickness of 3 to 50 μm, more preferably 5 to 30 μm, and the heat-sealable resin layer has a thickness of 10 to 100 μm, and more preferably 20 to 80 μm. It is preferable. The adhesive resin layer is preferably in the range of 0.5 to 10 μm, more preferably 1 to 10 μm.

  Examples of the use of the shrinkable laminated film of the present invention include deep drawing packaging, frozen food packaging, pillow packaging, etc., but when used as a deep drawing bottom material, the film for the lid material is the present invention. It is a film that can be adhered to the shrinkable laminated film, preferably heat-sealable, and may be any of the shrinkable laminated film, other non-shrinkable film, and the shrinkable film of the present invention.

  The contents packed with the shrinkable laminated film of the present invention are processed meat products such as sliced bacon, sausage, ham, grilled pork, hamburger and meat; processed dairy products such as cheese; marine products such as kamaboko and kadodori; Processed processed products such as processed noodles, konjak, ganmodori, fried chicken, etc .; processed foods such as powdered or liquid foods; other non-foods such as machine parts and electronic parts; These contents include processed meat products that are subjected to boil treatment for the purpose of surface sterilization after packaging, and marine product products that are frozen and distributed.

  The packaging body deep-drawn and packaged using the shrinkable laminated film of the present invention is filled with the contents such as the processed food in the concave container portion formed by forming the shrinkable laminated film, and the lid material is placed thereon. Packaging with less curl when guided to a specific vacuum packaging device and heat-shrinks the side and bottom surfaces of the concave container part so that it does not cause wrinkles or voids and is heat-sealed with the lid. When a food product that generates carbon dioxide such as cheese is packaged, a package that does not swell due to the generated gas is provided.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

  In addition, the measuring method of the physical property described in this specification is as follows.

  Hot water shrinkage: A sample cut out with a cutter knife with a size of 10 cm in the machine direction (longitudinal MD) and the direction perpendicular to the machine direction (transverse direction TD) is immersed in hot water at 90 ° C. for 10 seconds. After taking out, it was cooled with water at room temperature. Thereafter, the vertical and horizontal directions were measured with a scale, and the ratio of the decrease value from 10 cm to the original length of 10 cm was calculated as a percentage. The hot water shrinkage rate was displayed as an average value of the number of measurements n = 5. The unit is%. In the table, it is indicated by (measured value in the vertical direction / measured value in the horizontal direction).

  Tensile modulus: The length and width of the film are each cut with a cutter knife into a width of 20 mm and a length of 200 mm, and a chuck-to-chuck distance of 100 mm (width) using a tensile tester (Orientec, “Tensilon RTM-100”). 20%), 2.5% Secant Modulus was measured under the conditions of a tensile speed of 10 mm / min, 23 ° C., and 50% RH. The average value of the number of measurements n = 5 was displayed as the tensile modulus. The unit is MPa. In the table, it is indicated by (measured value in the vertical direction / measured value in the horizontal direction).

  Puncture strength: Using a tensile tester (Orientec Co., “Tensilon RTM-100”) equipped with a puncture pin having a radius of curvature of 0.5 mmR and a tip diameter of 1.0 mm, the puncture pin was moved at a speed of 50 mm / min. In the center of the surface from the front surface side (outer layer side) and the back surface side (seal layer side) close to the sample shrinkable laminated film fixed as a circular surface having a diameter of 4.5 cm at 23 ° C. and 50% RH. The value of the maximum point until puncture and rupture was measured, and the puncture strength was displayed as an average value of the number of measurements n = 5. The unit is N. In the table, it is expressed as (measured value on the outer layer side / measured value on the seal layer side).

Measurement of carbon dioxide and oxygen gas permeability:
Carbon dioxide gas permeability and oxygen gas permeability were measured in the state of the laminate. Using a mixed gas permeability measuring device (GL Science Co., Ltd., film double-side humidified gas permeation tester), the measurement was performed under conditions of a temperature of 30 ° C. and a relative humidity of 80%. A mixed gas (CO ₂ : O ₂ = 20: 80% by volume) was used as the test gas. A gas chromatograph (GC-390) manufactured by GL Science Co., Ltd. was used as the permeating gas detector, and PorapakN was used as the column. The average value of the number of measurements n = 3 was displayed as carbon dioxide gas permeability and oxygen gas permeability. The unit is cm ³ / m ² · day · atm.

Haze:
According to JIS K-7105, the average value of the number of measurements n = 5 was displayed as the haze value at room temperature using a haze measuring device (NDH2000, manufactured by Nippon Denshoku Co., Ltd.). The unit is%.

Deep drawability test:
In order to see the secondary moldability, the appearance of the package, the practical strength, etc., the film of Examples 1 to 3 as the bottom material, and the thickness from the first layer with the same resin configuration as Example 1 as the lid material A film having a thickness of 15/3/32 μm (total thickness of 50 μm) was produced, and a deep drawing formability test was performed using a deep drawing machine “FV603” manufactured by Omori Machine Industry Co., Ltd.

  The molding temperature was 100 ° C., and a drawing mold having a diameter of 98 mm and a depth of 50 mm was used. The contents were filled with natural cheese (about 250 g) having a diameter of 90 mm and a height of 40 mm. During filling, the vacuum and the bottom mold of the seal part were heated to 100 ° C. to obtain a deep drawn package. The appearance of the package was observed, and the presence or absence of crushing corners, expansion, and mold was observed.

Corner collapse:
“Excelent” was defined as a corner deformation of 5 mm or less with respect to the original corner portion filled with natural cheese. When there was a crushing deformation exceeding 5 mm with respect to the original size of the corner of the contents, it was determined as “Failure”.

Expansion of packaging:
The case where the package filled with natural cheese did not expand when stored in an oven at 15 ° C. for 1 week was defined as “Excellent”. The case where there was expansion was designated as “Failure”.

Observation of mold development:
It went about the natural cheese package. The natural cheese package was stored at 15 ° C. for 2 weeks, and the presence or absence of mold on the cheese surface was visually observed. The case where no mold was observed was designated as “Excellent”. The case where occurrence of mold was observed was designated as “Failure”.

Hexagonal rotation test:
In order to check the strength of the package, the drawing depth in the moldability test by the FV603 was 30 mm, and five circular rubber plates (weight: about 60 g / sheet) having a thickness of 5 mm and a diameter of 98 mm were packaged. The package is placed in a hexagonal tubular box (rotatably supported by a shaft extending horizontally by piercing the centers of two hexagonal sides parallel to each other), and a hexagonal rotation test for 10 minutes in an atmosphere at 5 ° C ( Abuse test, n = 10) was conducted, and the incidence (%) of pinholes in the package after the test was examined and shown in Table 2.

In a bowl:
The package before the hexagonal rotation test in which the circular rubber plate used for the hexagonal rotation test described above was packaged was boiled at 90 ° C. for 30 minutes, and the package was observed for wrinkles. The case where the package had 5 or less wrinkles having a length of 5 mm and a depth of 2 mm or less was defined as “Excellent”. “Failure” was defined when the package had more than 5 wrinkles having a length of 5 mm and a depth of 2 mm or more.

Curl property:
The package before the hexagonal rotation test in which the circular rubber plate was packaged was boiled at 90 ° C. for 30 minutes, and the curl of the flange portion was observed. When the flange portion was in a curled state of 10 mm or less from a flat state, it was set as “Excellent”. When the flange portion was in a curled state of 10 mm or more from a flat state, it was determined as “Failure”.

(Examples 1-3)
Using three extruders, a polyamide resin, an adhesive resin, and a polyethylene resin are sequentially laminated from the outer layer through an annular die, melt extruded at the die temperature of 245 ° C., cooled by a water-cooled shower ring, and a tubular body sheet is obtained. Obtained. Next, after heating in a hot water bath at 80 to 95 ° C., inflation stretching was performed at the stretching ratio shown in Table 2. Next, air is again introduced into the stretched tubular film in the heat treatment cylinder to form tubular bubbles, steam is blown in, the temperature in the heat treatment cylinder is adjusted to 90 to 95 ° C, and the shrinkable laminated film is relaxed by 30% in length and breadth respectively. Was prepared. The resin materials used are shown in Table 1.

  Table 2 shows the measurement results of hot water shrinkage, tensile elastic modulus, puncture strength, carbon dioxide permeability and oxygen gas permeability, deep drawability test filled with natural cheese, and hexagonal rotation test. Indicated. The number shown after the material / of each layer is the thickness (unit: μm).

  Further, as the curling property, the package in which the circular rubber plate was packaged was boiled at 90 ° C. for 30 minutes, and the curling of the flange portion was observed. The results are shown in Table 2.

(Comparative Examples 1 and 2)
Using the number of extruders corresponding to the type of laminated resin constituting the laminated film shown in Table 2, a laminated film was produced under the film forming conditions shown in Table 2 according to Example 1. Comparative Example 1 had a low carbon dioxide gas permeability, and Comparative Example 2 had a high hot water shrinkage rate.

(Comparative Example 3)
A non-shrinkable laminated film having the same resin configuration as that of Example 1 was produced by a direct inflation method.

Example 4
Using the packaging material obtained in Example 1, the same dried fish was filled with a deep-drawing vacuum packaging machine manufactured by Multi-Back Co., Ltd. to obtain a package. This package was free from pinholes during vacuum packaging and hexagonal rotation tests.

(Examples 5 to 9)
The layer configuration and the stretching ratio were stretched under the same conditions as in Example 1, and each layer thickness configuration was the same as in Example 1. The stretch rate after stretching of this film was 20% in length and 30% in width (Example 5). ), Vertical 25%, horizontal 25% (Example 6), vertical 25%, horizontal 30% (Example 7), vertical 25%, horizontal 35% (Example 8), vertical 20%, horizontal 20% (implemented) A shrinkable laminated film was prepared as Example 9). The hot water shrinkage rate, tensile modulus, puncture strength, carbon dioxide gas permeability, and oxygen gas permeability of these films were measured. Moreover, the deep-drawing formability test filled with natural cheese and a rubber plate was conducted in the same manner as in Example 1, and the expansion of the package, the generation of pinholes by the hexagonal rotation test, and wrinkles were observed. These results are shown in Table 3.

(Examples 10 to 13)
Using the same resins as in Example 1 and Example 3, shrinkable laminated films with different layer thicknesses were prepared. Table 4 shows the measurement results of the film forming conditions and film properties, and the deep drawability test filled with natural cheese and rubber plate, the expansion of the package, the generation of pinholes by the hexagonal rotation test, and the evaluation results of wrinkles. Indicated. In Examples 10 and 12, during a deep drawing moldability test in which about 200 g of natural cheese was filled, a drawing mold having a molding temperature of 100 ° C., a diameter of 98 mm and a depth of 20 mm was used. In the hexagonal rotation test, a circular shape having a diameter of 98 mm, a drawing depth of 20 mm, and 3 pieces of circular rubber plate (weight of about 60 g / sheet) were packaged and tested. Examples 11 and 13 were based on the method of Example 1. Table 4 shows these results.

(Examples 14 and 15 and Comparative Example 4)
An example in which the relaxation rate was changed using the same resin configuration as in Example 3 (Example 14), and an example in which the relaxation rate and the layer thickness of each layer and consequently the total thickness were changed (Example 15) Prepared according to 3. Further, an unstretched film having the same resin configuration as that of Example 3 was prepared by a multilayer inflation method, and used as Comparative Example 4. Measurement results of film forming conditions and film characteristics at this time, deep drawability test filled with natural cheese, expansion of packaging, presence of mold, occurrence of pinholes by hexagon rotation test, evaluation results of wrinkles Table 5 shows.

According to the present invention, when the shrinkable laminated film is used for packaging food such as fish having sharp protrusions, the film has high pinhole resistance, and can prevent deterioration of contents due to the occurrence of pinholes. When packaging foods and ingredients that generate a large amount of carbon dioxide such as cheese, the package can be prevented from swelling due to the generated gas, and the appearance of the package can be kept clean, which is a problem when used as a deep drawing film. There is provided a shrinkable laminated film in which other properties other than film strength, such as crushing of deep-drawn corner portions, wrinkles during molding, and curling of flange portions are improved.
Therefore, even if the shrinkable laminated film having a low hot water shrinkage provided by the present invention is stretched, it can be deep-drawn with a deep bottom using the stretched film. Thus, it is possible to provide a package with improved resistance to pinholes, crushing of corners, wrinkles at the time of molding, swelling of food packages that generate carbon dioxide, and the like.

Claims (3)

Outer layer comprising a polyamide resin, an intermediate layer consisting of acid-modified polyolefin, and a shrinkable laminated film consisting of only three layers of the inner layer made of a polyolefin resin, a co-extruded laminate film stretched by an inflation method, 90 Shrinkable laminated film for deep-drawing molding having a hot water shrinkage rate of 2 to 15% in both longitudinal and lateral directions and a carbon dioxide gas permeability at 30 ° C and 80% relative humidity of 500 cm ³ / m ² · day · atm or more. .   The shrinkable laminated film according to claim 1, wherein the tensile elastic modulus at 23 ° C is 600 MPa or less and the puncture strength at 23 ° C is 10 N or more. Outer layer comprising a polyamide resin, an intermediate layer consisting of acid-modified polyolefin, and a coextruded multilayer film of the tubular body consisting of only three layers of the inner layer made of a polyolefin resin, by an inflation method to two to four times each in the horizontal and vertical directions The method for producing a shrinkable laminated film according to claim 1, wherein the film is stretched and then thermally relaxed by 20 to 40% in the longitudinal and lateral directions with steam or warm water .