JPH0557855A - Heat-shrinkable laminated film for heat-seal - Google Patents

Abstract

PURPOSE:To obtain a film having an excellent oxygen gas barrier property, anti-bending pinhole property or the like, having no interlayer separations, and being easy for manufacturing bags and suitable for wrapping by laminating a sealant layer consisting of a double layer onto the biaxially oriented film of a heat-shrinkable polyamide laminate consisting of specific two kinds of layers. CONSTITUTION:The film is manufactured by employing a specific composite polymer A, polymer B and polymer P as materials, wherein one made by mixing the polymer A into the polymer P at 0.3-5wt.% is allowed to be an (a) layer, one consisting of the polymer B is allowed to be a (b) layer, and one made by blending the polymer P into the mixture C of the polymer A and polymer B at 5wt.% or less is allowed to be a (c) layer and, on the biaxially oriented film of a heat-shrinkable polyamide laminate consisting of at least two-kinds of layers among these three-kinds of layers and being in the range of 15-35% in hot water contraction rate, a (d) layer consisting of low density polyethylene polymer and an (e) layer consisting of polymer selected from straight chain low density polyethylene polymer, ethylene-polyvinyl acetate copolymer, or ionomer polymer are laminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable laminated film which is suitable for shrink-wrapping food products and which can be heat-sealed. More specifically, it is excellent in oxygen gas barrier property, bending pinhole resistance, and can be used for manufacturing a bag body that is hermetically sealed by the heat-sealing method, and is resistant to delamination and bag breakage when subjected to hot water treatment. And a heat-shrinkable laminated film which can be obtained.

[0002]

2. Description of the Related Art Conventionally, ham and meat foods are generally vacuum-packed with a heat-shrinkable film, and then the film is shrunk. Further, in the field of packaging foods such as ham, processed meats such as sausages, edible wild plants, thread konjac, anko etc., the food is filled in a bag made of a heat-shrinkable film, sealed, and then the bag is immersed in hot water. Tension wrapping is generally performed in which the bag body is made to contract and the bag body is given tension. At this time, as the heat-shrinkable film used as the base material of the bag body, a film obtained by laminating a polyamide-based film and a film such as low-density polyethylene or ethylene-vinyl acetate copolymer, or polyvinylidene chloride film is used. ing.

However, a heat-shrinkable film made of an aliphatic polyamide polymer which has been conventionally used as a substrate is excellent in mechanical properties such as tensile strength and resistance to bending pinholes, but is excellent in oxygen gas barrier property. Has the drawback of not being enough. Therefore, in order to impart an oxygen gas barrier property to this film, the surface of this film is coated with vinylidene chloride polymer latex,
A method for forming a film having an excellent oxygen gas barrier property has been proposed and put into practical use. However, the film coated with this vinylidene chloride-based polymer latex is excellent in oxygen gas barrier property but inferior in flexure pinhole resistance, and has a drawback that it becomes cloudy when treated with hot water,
In addition, compounds containing chlorine were generated during incineration, causing environmental pollution.

On the other hand, as a film having a good oxygen gas barrier property, an aroma mainly composed of a polyamide structural unit composed of m- and / or p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms. A raw material made from a group polyamide polymer has been proposed. This film is excellent in transparency and oil resistance, but is inferior in bending pinhole resistance, so that its use is limited. In order to improve the bending pinhole resistance of this film, a method of copolymerizing a polyether component is known.
Although it is proposed in Japanese Patent Publication No. 1-84847, there is a problem that the cost is high.

Further, among conventional heat-shrinkable laminated films, for example, a heat-shrinkable polyamide film obtained by extruding and laminating low-density polyethylene is used to make a low-density polyethylene by bag-making using a so-called "seasoning" method. Since the heat-sealing strength is insufficient, there is a serious drawback that the bag is broken from the sealed portion when hot water shrinkage treatment is performed after the bag is filled with the object to be packaged and sealed. When a film made of a linear low-density polyethylene is dry-laminated on a heat-shrinkable polyamide film, when the bag is also made by the palm-sealing method, delamination (also called delamination) occurs at the laminated portion. Occurs,
In some cases, there was a problem that even the bag was broken.

On the other hand, polyvinylidene chloride is added with a plasticizer before the film is formed for the purpose of compensating the molding processability of the film, so that the obtained film does not show the original performance of polyvinylidene chloride and the oxygen gas barrier is not present. The sex is not enough. In addition, when polyvinylidene chloride film is used as a base material and a bag-making method is made by the palm-sealing method, and when the product to be packaged is filled with it, a method of connecting both ends of a tubular bag body with aluminum metal fittings is usually adopted. However, this tying method also has a problem in that oxygen enters due to insufficient sealing of the bag.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, the present invention does not contain a chlorine compound, exhibits excellent oxygen gas barrier properties and excellent bending pinhole resistance, and is made into a bag by a heat sealing method. It is an object of the present invention to provide a heat-shrinkable laminated film capable of storing foods and the like in a heat-shrinkable package without delamination or bag breakage even if stored for a long period of time and exhibiting effects such as preservation of foods for a long time. And

[0008]

The inventors of the present invention have completed the present invention as a result of intensive studies to solve such problems. Therefore, the gist of the present invention is to use a polymer (A), a polymer (B) and a polymer (P) having the following compositions as raw materials, and to add 0.3% of the polymer (P) to the polymer (A). ˜5% by weight mixed (a)
Layer, a layer comprising the polymer (B) (b) a layer, a layer comprising the mixture (C) of the polymer (A) and the polymer (B) and 5% by weight or less of the polymer (P) ( c) a heat-shrinkable polyamide laminated biaxially stretched film having a structure including at least two of these three layers and having a hot water shrinkage ratio at 95 ° C. of 15 to 35%. , A layer (d) made of a low-density polyethylene polymer, a linear low-density polyethylene polymer, an ethylene-vinyl acetate copolymer, or an (e) layer made of a polymer selected from an ionomer polymer is sequentially laminated. A heat-shrinkable laminated film capable of being heat-sealed. Polymer (A): Aromatic compound containing 70 mol% or more of polyamide constituent units consisting of m- and / or p-xylylenediamine and α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain. Polyamide polymer (B): Aliphatic polyamide polymer (P): Ionomer polymer or polyolefins grafted with unsaturated carboxylic acids, and polyolefins of the former 100 to 5% by weight and the latter 0 to 95% by weight. Mixed in range

The present invention will be described in detail below. The main raw materials of the heat-shrinkable polyamide-based laminated biaxially stretched film according to the present invention are two types of polyamide-based polymers (hereinafter referred to as “polymer (A)” and “polymer (B)”, respectively) and polyolefin. Polymer (hereinafter referred to as "polymer (P)")
Is. Polymer (A), which is one type of polyamide-based polymer
Is a polymer containing 70 mol% or more of a polyamide constitutional unit composed of m- and / or p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain. Specific examples of the polymer (A) include single-weight compounds such as polymeta-xylylene adipamide, poly-meta-xylylene pimeramide, poly-meta-xylylene azamide, poly-para-xylylene azamide, and poly-para-xylylene decanamide. Like coalesce, metaxylylene / paraxylylene adipamide copolymer, metaxylylene / paraxylylene pimeramide copolymer, metaxylylene / paraxylylene azelamide copolymer, metaxylylene / paraxylylene sepacamide copolymer And other copolymers. In addition, a polyamide constituent unit consisting of m- or / and p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms is contained in the molecular chain in an amount of 70 mol% or more. Examples thereof include a copolymer composed of a polyamide constituent component.

Other polyamide constituent components include diamine components, dicarboxylic acid components and other components. Specific examples of the diamine component include aliphatic diamines such as hexamethylenediamine and 2,2,4-trimethylhexamethylenediamine, heterocyclic rings or heteroatoms such as piperazine bispropylamine and neopentylglycol bispropylamine. There are diamines and the like, and specific examples of the dicarboxylic acid component include aliphatic dicarboxylic acids such as adipic acid, azelaic acid and sebacic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, 1,
There are cycloaliphatic dicarboxylic acids such as 4-cyclohexanedigalvic acid, and other components include lactams such as ε-caprolactam and ω such as ε-aminocarboxylic acid.
-There are aminocarboxylic acids, etc.

The polymer (A) may contain a polymer (F) compatible with the polymer (A) up to a range of 20% by weight. Examples of the polymer (F) compatible with the polymer (A) include polyamide polymers and other thermoplastic resins not exemplified above. The polymer (A) contains a polyamide structural unit containing m- or / and p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain in an amount of 70 mol% or more. There must be. When it is out of this range, the target value of the oxygen permeability to be imparted to the finally obtained laminated biaxially stretched film (15 cc / m ² under the condition of temperature 25 ° C. and relative humidity 65%)
・ 24H ・ atm or less) is not preferable. Further, when the amount of the polymer (F) when the polymer (F) is contained in the polymer (A) exceeds 20% by weight, it is not preferable for the same reason.

Polymer (B), which is another type of polyamide polymer, is an aliphatic polyamide polymer. The polymer (B) may be a chain polyamide having an amide bond, and specific examples thereof include ε-caprolactam homopolymer, polyhexamethylene adipamide, ε-caprolactam or hexamethylene adipate. Examples thereof include a copolymer containing amide as a main component and 2 to 10 mol% of a compound copolymerizable therewith.

Examples of the compound copolymerizable with ε-caprolactam or hexamethylene adipamide include nylon salts of aliphatic diamines and aliphatic dicarboxylic acids. Specific examples of the aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, decamethylenediamine and the like. Specific examples of the aliphatic dicarboxylic acids include adipic acid, sebacic acid, corkic acid, glutaric acid, azelaic acid, β-methyladipic acid, decamethylenedicarboxylic acid, dodecamethylenedicarboxylic acid, pimelic acid and the like. Among these polymers (B), polyhexamethylene adipamide called nylon 6 or nylon 66, which is a homopolymer of ε-caprolactam, is available at a low price,
In addition, the biaxial stretching operation can be smoothly performed, which is preferable.

The mixture (C) is a mixture of the polymer (A) and the polymer (B), but it may be a mixture of virgin compounds, or may be formed when a laminated film is produced. It may be a nonstandard film or a scrap mixture such as a cut end material (edge trim) at the film side end, or a scrap mixture to which virgin is added. The mixing ratio of these two types of polymers is not particularly limited, but it is preferable to select the polymer (A) and the polymer (B) in a weight ratio of 7: 3 to 1: 9. ..

The polymer (A), the polymer (B) and the mixture (C) are all highly hygroscopic, and if they are used, water vapor and oligomers are generated when the raw materials are melted by heat and extruded. However, since it inhibits film formation, it is preferably dried in advance so that the water content is 0.1% by weight or less. Various additives such as a lubricant, an antistatic agent, an antioxidant, an antiblocking agent, a stabilizer, a dye, a pigment, and inorganic fine particles are added to the polymer (A), the polymer (B) and the mixture (C). It can be added within a range that does not affect the properties of the film.

The polymer (P) means an ionomer polymer or modified polyolefin (P1) and a polyolefin (P2), an ionomer polymer or modified polyolefin (P1) 100 to 5% by weight, a polyolefin ( P2) mixed in the range of 0 to 95% by weight, and if the ionomer polymer or modified polyolefin (P1) is less than 5% by weight, the effect of uniformly dispersing the polymer (P) in the polyamide polymer is poor. It is not preferable.

The ionomer polymer is a polymer obtained by crosslinking a copolymer of an α-olefin and an unsaturated carboxylic acid with a metal ion. Ethylene is preferably used as the α-olefin, and acrylic acid and methacrylic acid are preferably used as the unsaturated carboxylic acid, but both are not limited to those exemplified here. The metal ion is an ion such as sodium, calcium, or zinc.

The modified polyolefins (P1) refer to those obtained by graft-polymerizing unsaturated carboxylic acids on the skeleton polyolefins. Modified polyolefins (P1)
Specific examples of the polyolefins (P2) mixed with the polyolefin serving as the skeleton of are olefin homopolymers or copolymers such as ethylene and propylene, for example, high-density polyethylene, low-density polyethylene, Examples thereof include linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene and the like. Specific examples of the unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, carboxylic acids such as citraconic acid, maleic anhydride, citraconic anhydride, acid anhydrides such as itaconic anhydride, Alternatively, a metal salt of an acid such as potassium acrylate or potassium methacrylate can be used.

The modified polyolefins (P1) can be produced by a known method, for example, a method in which a polyolefin and an unsaturated carboxylic acid are reacted in a molten state (for example, Japanese Patent Publication No. 4).
No. 3-27421), a method of reacting in a solution state (see, for example, JP-B-44-15422), a method of reacting in a slurry state (for example, JP-B-43-1).
No. 8144), a method of reacting in a gas phase state (see, for example, JP-A No. 50-77493), and the like.

The content of unsaturated carboxylic acids in the modified polyolefin (P1) is preferably in the range of 0.01 to 5% by weight, particularly preferably 0.1 to 3% by weight. Content of unsaturated carboxylic acids is 0.01
If it is less than 5% by weight, it cannot be uniformly mixed with the polyamide-based mixed polymer, and the obtained film becomes hazy. On the other hand, if it exceeds 5% by weight, not only the production cost is high, but also the obtained film is Since the effect of improving the resistance to bending pinholes is saturated, the content of unsaturated carboxylic acids in the modified polyolefin (P1) need not exceed 5% by weight.

It is not necessary that the polyolefins forming the skeleton of the modified polyolefins (P1) in the polymer (P) and the polyolefins (P2) mixed with the same are the same. Further, in order to uniformly disperse the polymer (P) in the polyamide polymer, it is preferable to knead the ionomer polymer or modified polyolefins (P1) and the polyolefins (P2) in advance and pelletize them. Desirable, but not limited to this, provided that the dispersibility does not change.

The three types of layers constituting the heat-shrinkable polyamide-based laminated biaxially stretched film according to the present invention are a layer (a) and a polymer (B) in which the polymer (P) is mixed with the polymer (A). )
The layer (b) is composed of the layer (c) and the mixture (C) is mixed with the polymer (P). This layer structure is (a)
It is preferable that the layer, the layer (b), and the layer (c) are appropriately selected and combined to include at least two types of layers.
The combination at this time is not particularly limited, and specific examples thereof include (a) / (b), (c) / (b), (a) /
(B) / (c), (b) / (a) / (c), (b) /
(C) / (a), (c) / (a) / (c), (b) /
(C) / (a) / (b), (b) / (c) / (a) /
(C) / (b), (b) / (a) / (c) / (a) /
Examples thereof include (b) and (c) / (b) / (a) / (b) / (c), but are not limited thereto. In addition, if you want to improve the curl property of the film (a phenomenon in which when the film is cut into a certain size and left on a flat surface, the film does not maintain a flat state and the edge or center part rises from the flat surface), c) / (a) / (c), (c) /
(B) / (a) / (b) / (c), (b) / (c) /
It is particularly preferable that the layer structure and layer thickness such as (a) / (c) / (b) are substantially symmetrical.

In this case, the polymer (P) contained in the layer (a)
The mixing ratio in the range of 0.3 to 5% by weight based on the total amount of all the polymers contained in the layer (a),
If it is less than 3% by weight, there is no effect of improving the bending pinhole resistance of the obtained film, while if it exceeds 5% by weight, the obtained film becomes hazy, which is not preferable. Particularly preferred in the above range is 0.5 to 4% by weight. Further, the layer (c) contains a polymer (P) in the ear trim or the like when the ear trim or the like produced during the production of the laminated film is used, and therefore the polymer (P) need not be newly added thereto. However, when the amount of the polymer (P) contained in the layer (c) is adjusted, it may be newly added. The mixing ratio of the polymer (P) contained in the layer (c) is 5% by weight or less based on the total amount of all the polymers contained in the layer (c), and is obtained when it exceeds 5% by weight. The resulting film becomes hazy, which is not preferable. Particularly preferred in the above range is
It is 0.1 to 3% by weight.

In order to mix the polymer (A) and the polymer (P) constituting the layer (a), pellets of the respective polymers are uniformly dry blended in the above mixing ratio. The method of melting the dry blend with an extruder and pelletizing the dry blend may be used.

The heat-shrinkable polyamide laminated biaxially stretched film according to the present invention can be manufactured by a known method. First, a raw material composed of the polymer (B), the polymer (A) in which the polymer (P) is mixed, and the mixture (C) in which the polymer (P) is mixed is substantially amorphous and not oriented. An unstretched laminated film is manufactured. The unstretched laminated film does not require an adhesive for adhering the single films to each other, and it is preferable to adopt a co-extrusion method that can obtain a laminated film having excellent performance. The manufacturing method by the co-extrusion method is such that the above raw materials are melted by at least two extruders, and a flat die,
Alternatively, it is extruded from an annular die and then rapidly cooled to obtain a flat or annular unstretched laminated film.

Next, the above-mentioned unstretched laminated film is biaxially stretched 2.5 to 5 times in the film flow (vertical axis) direction and in the direction (horizontal axis) perpendicular thereto. The draw ratio is 2.5 in each of the vertical and horizontal directions of the film.
If it is less than twice, the effect of stretching is not obtained and the strength of the film is poor. On the other hand, if it is more than 5 times in each axial direction, the film tends to tear during stretching, which is not preferable. As the biaxial stretching method, known stretching methods such as tenter type sequential biaxial stretching, tenter type simultaneous biaxial stretching, and tubular type simultaneous biaxial stretching can be used without departing from the spirit of the present invention. For example, in the case of the tenter type sequential biaxial stretching method, the unstretched laminated film is heated to a temperature range of 50 to 110 ° C. and stretched to 2.5 to 5 times in the longitudinal direction by a roll type longitudinal stretching machine, Then, 60 to 1 by a tenter type horizontal stretching machine
It can be manufactured by stretching the film in the transverse direction in the temperature range of 20 ° C. by 2.5 to 5 times. In the case of the tenter simultaneous biaxial stretching method or the tubular simultaneous biaxial stretching method, for example, in a temperature range of 60 to 110 ° C., it is produced by simultaneously stretching in the longitudinal and transverse directions 2.5 to 5 times in each axial direction. can do.

The film stretched by the above method is then heat treated. By appropriately selecting the heat treatment temperature, a film having a desired shrinkage can be obtained.
The temperature at the time of heat treatment is 130 ° C. as the lower limit and 50 ° C. lower than the melting point of the polymer (B) as the upper limit, so that a stretched film having an arbitrary heat shrinkage rate can be obtained. it can. When the film is heat-treated at a temperature of 130 ° C. or less, the film naturally contracts due to the humidity in the air while being left unattended, and the film is wound tightly in a rolled state, which is not practical. When heat-treated at a temperature of 130 ° C. or less, the hot water shrinkage rate becomes 35% or more, and a sealant layer is laminated on the heat-shrinkable laminated film to shrink the film with hot water. When this happens, the film is wrinkled, which is not desirable in appearance, and peeling easily occurs from the wrinkled portion at the interface with the sealant. The heat-treated film is subjected to corona discharge treatment on one side or both sides of the film and wound into a roll by a conventional method. The degree of corona discharge treatment is such that the surface wetting tension measured according to JIS K-6768 method is 52 to 54 dyne /
It is preferable to select in the range of cm. Further, after the production of the heat-shrinkable polyamide laminated biaxially stretched film, the surface of the film may be printed.

The heat-shrinkable polyamide laminated biaxially stretched film (base film) of the present invention has a thickness of 10 μ or more and 40 or more.
It is preferably μ or less. If the total thickness is less than 10 μ, the oxygen gas barrier property and the flex pinhole resistance are poorly balanced and the abrasion resistance is also poor, so that a satisfactory film for packaging cannot be obtained. When it exceeds 40 μ, the film becomes hard, and when a sealant layer is further adhered, the whole film becomes very thick, which makes it unsuitable for soft packaging.

The heat-shrinkable laminated film capable of being heat-sealed according to the present invention comprises, on the above-mentioned base film, a layer (d) consisting of a low-density polyethylene polymer, a linear low-density polyethylene polymer and an ethylene-vinyl acetate copolymer. It is essential to laminate a layer (e) made of a polymer selected from a polymer or an ionomer polymer. The low-density polyethylene polymer constituting the layer (d) is a polymer obtained by polymerizing ethylene by a high pressure method. Further, the polymer constituting the (e) layer is a polymer selected from a linear low-density polyethylene polymer, an ethylene-vinyl acetate copolymer or an ionomer polymer. The linear low-density polyethylene polymer means an ethylene / α-olefin linear copolymer, and may be a single one or a mixture of two or more thereof. Examples of the α-olefin copolymerized with ethylene include butene-1, pentene-1, heptene-1, octene-1, 4 methylpentene-1, decene-1, undecene-1, dodecene-1 and the like. Content of copolymerized α-olefin is 0.5 to 10 mol%
It is preferable to select within the range. The ethylene-vinyl acetate copolymer is a copolymer of ethylene and vinyl acetate, and the content of vinyl acetate is in the range of 3 to 20% by weight.

Next, a method for producing the heat-shrinkable laminated film capable of being heat-sealed by laminating the layer (d) and the layer (e) (sealant layer) on the base film will be described. In order to sequentially laminate the (d) layer and the (e) layer as the sealant layer on the base film, the extrusion lamination method (extrusion lamination method) is preferable. In the extrusion lamination method, an adhesion promoter (anchor coating agent) is applied to a base film, the coated surface is dried, and then the same surface (d) layer made of low density polyethylene melted by an extruder and a linear A low density polyethylene polymer, ethylene-vinyl acetate copolymer or one kind of polymer selected from ionomer polymers is melted by an extruder and directly and sequentially extruded, pressure-bonded and cooled (tandem method), and base film There is a method (polysand method) in which a low-density polyethylene melted between the film and the film-formed (e) layer is extruded to form the (d) layer, which is pressure-bonded and cooled. Here, as the anchor coating agent, an adhesive agent that is usually used when adhering a resin film and what is known as an anchor coating agent are used, and these can be used as they are without any limitation. Molds are preferred.

There is a so-called dry laminating method as a method for laminating the (d) layer and the (e) layer on the base film, but when this method is used, the shrinkage ratio between the bonded sealant layer and the base film is reduced. If the difference between
When the laminated film having the sealant layer is hot water-shrinked, a shearing force is generated at the adhesive interface, the adhesive layer is destroyed, and the base film and the sealant layer are separated, which is not preferable. On the other hand, when the film laminated by the polysand extrusion method or the tandem extrusion method is subjected to hot water shrinkage, peeling does not occur between the base film and the sealant layer. In the polysand extrusion method, a film formed in advance is used,
If the surface on which the sealant layer is laminated is subjected to corona discharge treatment, the heat seal strength can be greatly improved. Further, in the tandem extrusion method, since the second extrusion is performed on the low density polyethylene as the (d) layer,
The temperature condition of melt extrusion can be set to 300 ° C. or less, oxidation of the surface of the base film can be suppressed, and high heat seal strength can be maintained. Therefore, even if the packaging body in the bag shape and filled with the contents is treated with hot water, the packaging body is not broken.

The thickness of the layer (d) made of a low density polyethylene polymer as the sealant layer is preferably 15 to 30 μm, and is made of a linear low density polyethylene polymer, an ethylene-vinyl acetate copolymer or an ionomer polymer. The thickness of the (e) layer made of the selected polymer is preferably 25 to 60 μm. The heat-shrinkable laminated film of the present invention has a layer (d) and a layer (e) as a sealant layer.
A low density polyethylene polymer, an ethylene-vinyl acetate copolymer, an ionomer polymer, or the like can be laminated on the side where no layer is formed by an extrusion laminating method.

The heat-shrinkable laminated film according to the present invention can be used as a bag by bonding end portions of sealant layers to each other. There is no limitation on the method for manufacturing the bag body, and the pillow method which has been conventionally known,
Either a three-way seal system or a gusset system can be used. For example, when a pillow wrapping machine is used, a series of steps of bag making, filling of a packaged object, and sealing are performed with high productivity,
It can be done continuously and automatically. A packaging machine that can be used in the case of this pillow packaging may be either a vertical pillow packaging machine or a horizontal pillow packaging machine, and may be selected depending on the type and property of the article to be packaged. The heat sealing temperature during bag making and sealing is preferably selected in the range of 150 to 200 ° C. In addition, a package in which a processed meat product or the like is filled in a bag has no slack by immersing it in hot water of 80 to 95 ° C and is heat-shrinked, and is a tightly packaged product, which can be easily crushed. Protected from external force. Furthermore, after vacuum packaging, pinholes are less likely to occur even when contracted with hot water or steam, so
It is possible to keep the life of the stored food for a long time.

The heat-shrinkable heat-shrinkable laminated film according to the present invention can be produced by the above-mentioned method, but has the following physical properties, that is, oxygen transmission rate under the conditions of temperature 25 ° C. and relative humidity 65%. There 15cc / m ² · 24
H · atm or less, and bending pinhole resistance is 23
When the number of pinholes after flexing 3000 times by the Gelbo flex tester at 15 ° C. and 50% relative humidity is 15/77 inch ² or less, the oxygen gas barrier property and the flexing pinhole resistance are excellent.

[0035]

EXAMPLES The contents and effects of the present invention will be described below in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following examples, the film was evaluated by the following methods. Further, Table 1 and Table 2 show the constitution, measurement and evaluation results of the film.

<Oxygen permeability (cc / m ² · 24H · at
m)> Modern control company OXY-TRAN10
It was measured under the conditions of a temperature of 25 ° C. and a relative humidity of 65% using a 0 type oxygen permeability measuring device.

<Bending pinhole resistance (piece / 77 inch
² )> Under conditions of a temperature of 23 ° C. and a relative humidity of 50%, the conditioned film that has been left standing for 24 hours or more is cut into an 8 inch × 11 inch rectangular film, and the rectangular film is a gel manufactured by Rigaku Kogyo Co., Ltd. With the Boflex tester (No.901 type), it rotates 440 ° while advancing 3.5 inches, goes straight for 2.5 inches, then
On the contrary, the bending operation test was performed 3000 times with one operation of returning. After the completion of this test, the number of pinholes formed on the tested film was visually observed and measured.

<Hot water shrinkage rate> A square film having a side length of about 15 cm was used as a sample, and this sample was heated at a temperature of 2
After controlling the humidity for 24 hours or more in an atmosphere of 3 ° C. and a relative humidity of 50%, the vertical and horizontal lengths of the sample film were accurately measured. (The average value is Lo.) Then, the sample film was immersed in hot water of 95 ° C. for 5 minutes, and then the adhering water was completely wiped off, and the temperature was 23 ° C. and the relative humidity was 50.
After controlling the humidity for 24 hours in an atmosphere of%, the vertical and horizontal lengths were accurately measured. (The average value is Ls.) The hot water shrinkage ratio was calculated by the following formula. Hot water shrinkage (%) = ((Lo-Ls) / Lo) x 100

<Boiler bag breakage test of package> A heat-shrinkable laminated film which is heat-sealable is slit into a width of 160 mm to prepare a roll film, and a vertical pillow type automatic packaging (bag making / filling) machine is formed by using this film. 200g of water as the object to be packaged while creating the package by the palm-stick method
After filling, a package having a peripheral length of 135 mm and a length of 180 mm was prepared. Ten of these packages were immersed in hot water at 90 ° C. for 30 minutes, and visually evaluated for the presence or absence of delamination, destruction of the heat-sealed portion, and the like.

<Decomposition Test of Contents> The packaging prepared in each Example or Comparative Example was filled with raw oysters, and the presence or absence of decay was observed and evaluated.

Example 1 100 parts by weight of an ethylene-propylene copolymer having an ethylene content of 83 mol% and a melt flow index of 1.0 g / 10 minutes, and α dissolved in a small amount of acetone,
0.025 parts by weight of α'-bis-t-butylperoxy-p-diisopropylbenzene and 0.8 parts by weight of maleic anhydride were mixed in a Henschel mixer. This mixed granular material is extruded at 230 ° C. into a pellet by using an extruder having an inner diameter of 40 mmφ and L / D = 28 to form a modified ethylene-propylene copolymer (modified polyolefin (P1)).
Got 20% by weight of these pellets and 80% by weight of an ethylene-vinyl acetate copolymer (polyolefins (P2)) having a vinyl acetate content of 8% by weight and a melt flow index of 1.5 g / 10 minutes are mixed, and an inner diameter of 40 mmφ, L /
A polymer (P) was prepared by extruding at 200 ° C. using an extruder with D = 28 and pelletizing. Next, polymeta-xylylene adipamide (manufactured by Mitsubishi Gas Chemical Co., Inc., MXD-nylon 6007) (polymer (A)) and the above polymer (P) were mixed at a ratio of 97: 3, poly, ε-caproamide (Novamid 102, manufactured by Mitsubishi Kasei Co., Ltd.)
2) (Polymer (B)), and crushed material of the edge trim film of the film (the mixing ratio of the polymer (A) and the polymer (B) is 4).
0:60, the mixing ratio of the polymer (P) in the total polymer is 1.2% by weight) is separately melted using three 65 mmφ extruders, and laminated in a co-extrusion T-die. Let me 3
Extruded as a laminated film having a layer structure, adhered to a cast roll at 30 ° C. and rapidly cooled, and the polymer (B) having an outer layer of about 54 μm,
The intermediate layer is a mixture of the polymer (A) and the polymer (P) of about 36 μ, the inner layer is a polymer (A) of about 45 μ, and the mixture of the polymer (B) and the polymer (P) is not laminated. A stretched film was obtained. The laminated unstretched film obtained was stretched 3 times in the longitudinal direction by a roll-type stretching machine under the condition of 60 ° C., and then the end portion of this film was held by a tenter clip, and the condition was maintained at 90 ° C. in a tenter oven. Then, the film was stretched in the transverse direction three times and then heat-treated at 160 ° C. for 6 seconds. The hot water shrinkage ratio at 95 ° C. for 5 minutes was 20%.

After the heat treatment, the film gripped with clips is cut off from both ears of the film to make scrap, and the product film is wound on a winder to obtain about 6 μm.
Of the polymer (B) (layer (b)), about 4 μ of the mixture of the polymer (A) and the polymer (P) (layer (a)), about 5 μ of the polymer (B), The heat-shrinkable polyamide-based laminated biaxially stretched film (base film) having a total thickness of about 15 μm, in which the layers ((c) layers) of the mixture of the polymer (A) and the polymer (P) are laminated in this order. ) Was manufactured. A 15 μm-thick low-density polyethylene polymer layer (d) layer and a 30 μm-thick linear low-density polyethylene polymer layer (e layer) can be laminated on the obtained base film and heat-sealed. A heat shrinkable laminated film was obtained. Table 1 shows the results of observation, evaluation, and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the hot water shrinkage ratio, and the boil bag breaking property by the method described above.

Examples 2 to 9 In the examples described in Example 1, the layer constitution, film thickness, raw material composition ratio, and polymer (P) mixing ratio were changed as shown in Table 1, respectively. Otherwise, a heat-shrinkable laminated film capable of heat sealing was obtained by the same method as described in the same example. The composition of the film obtained,
By the method described above, oxygen permeability, flex pinhole resistance,
Table 1 shows the results of measuring, observing and evaluating the hot water shrinkage ratio and the boil bag breaking property.

Example 10 In the same manner as in the example described in Example 1, except that the polymer (P2) of the polymer (P) was replaced with low density polyethylene having a melt flow index of 1.5 g / 10 min. A heat-shrinkable laminated film capable of being heat-sealed was obtained by the same method as described above. Table 1 shows the results of observation, evaluation, and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the hot water shrinkage ratio, and the boil bag breaking property by the method described above.

Example 11 Similar to the example described in Example 1 except that the polymer (P) was replaced with an ionomer resin (HIMIRAN H-1652 manufactured by Mitsui DuPont Polychemical Co., Ltd.). A heat-shrinkable laminated film which can be heat-sealed by the method was obtained. Table 1 shows the results of observation, evaluation, and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the hot water shrinkage ratio, and the boil bag breaking property by the method described above.

Example 12 In the example described in Example 1, heat-shrinkable heat-shrinkable by the same method as described in the example except that the polymer (P) was replaced with the modified ethylene-propylene copolymer. A transparent laminated film was obtained. Table 1 shows the results of observation, evaluation, and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the hot water shrinkage ratio, and the boil bag breaking property by the method described above.

Comparative Example 1 A heat-shrinkable laminated film capable of heat sealing was obtained by the same method as described in Example 1 except that the polymer (P) was not used. Table 1 shows the results of observation, evaluation, and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the hot water shrinkage ratio, and the boil bag breaking property by the method described above.

Comparative Example 2 In the example described in Example 1, 11 times the stretched film was used.
A heat-shrinkable laminated film capable of heat-sealing by the same method as described in the same example except that heat treatment was performed at 5 ° C. for 6 seconds (the hot water shrinkage rate at 95 ° C., 5 minutes was 37%). Got Table 1 shows the results of observation, evaluation, and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the hot water shrinkage ratio, and the boil bag breaking property by the method described above.

Comparative Example 3 Using a commercially available vinylidene chloride-coated biaxially stretched nylon film (thickness: 17 μ), oxygen permeability, bending pinhole resistance, hot water shrinkage ratio, boil bag breaking property were measured by the methods described above. Table 1 shows the results of measurement and observation evaluation.

Examples 13 to 18 and Comparative Examples 4 and 5 The base film described in Example 1 was used to obtain a heat-shrinkable laminated film which was heat-sealable by the lamination layer constitution and the laminating method shown in Table 2, and then the films. A vertical pillow automatic filling machine was used to prepare a package. Table 2 shows the results of the observation and evaluation of the composition of the obtained film, the oxygen permeability, the bending pinhole resistance, the boil bag breaking property, and the rot test with raw oysters, which were measured by the above-mentioned method.
Shown in.

Comparative Example 6 Commercially available heat-shrinkable polyvinylidene chloride film having a thickness of 40 μm (Saran film manufactured by Asahi Kasei Kogyo Co., Ltd.)
Was sack-shaped by high-frequency sealing, raw oysters were put therein, both ends thereof were tied with aluminum metal fittings, and then boiled at 90 ° C. for 20 seconds to shrink the bag. Table 2 shows the results obtained by measuring and observing oxygen permeation rate, bending pinhole resistance, boil bag breaking property, and rotting test with raw oysters by the above-mentioned method.
Shown in.

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[Table 1]

[0053]

[Table 2]

In Tables 1 and 2, each abbreviation has the following meaning. A: Polymer (A) B: Polymer (B) P: Polymer (P) P1: Modified polyolefin P2: Polyolefin EVA: Ethylene-vinyl acetate copolymer LD: Low density polyethylene Et-Pr: Maleic anhydride -Modified ethylene-propylene copolymer HIMILAN: ionomer polymer HIMIRAN H-1652 manufactured by Mitsui DuPont Polychemical Co., Ltd. X: heat-shrinkable polyamide laminated biaxially stretched film LDPE: layer of low density polyethylene polymer LLDPE: straight chain Low density polyethylene polymer layer Ionomer: Ionomer polymer layer

The following can be seen from Tables 1 and 2. 1. In the heat-shrinkable laminated film capable of being heat-sealed according to the present invention, the oxygen gas barrier property and the bending pinhole resistance are within the intended numerical ranges. (See Table 1 and Table 2) 2. A bag body made from the heat-sealable heat-shrinkable laminated film according to the present invention, which has a sealant layer composed of two layers (d) and (e), does not break even in the boil bag breaking test of the package. No pouching and no delamination.
On the other hand, the bag made from the film of Comparative Example having only one sealant layer had a defective phenomenon such as delamination. (See Table 1 and Table 2)

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INDUSTRIAL APPLICABILITY The present invention has particularly remarkable effects as follows, and its industrial utility value is extremely large. 1. The heat-shrinkable laminated film capable of being heat-sealed according to the present invention has excellent oxygen gas barrier property and excellent bending pinhole resistance, and by heat-water shrinkage, the heat-shrinkable polyamide-based laminated biaxially stretched film and sealant. There is no delamination between layers and it can be used for all shrink wrapping. 2. The heat-shrinkable laminated film capable of being heat-sealed according to the present invention is easy to be processed into a bag by a method such as affixing palms, and is suitable for use in packaging foods and the like.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B65D 65/40 C 9028-3E // B29K 23:00 77:00 B29L 7:00 4F 9:00 4F

Claims (1)

[Claims] 1. A polymer (A) and a polymer (B) having the following composition:
And (a) obtained by using the polymer (P) as a raw material and mixing the polymer (A) with the polymer (P) in an amount of 0.3 to 5% by weight.
Layer, a layer comprising the polymer (B) (b) a layer, a layer comprising the mixture (C) of the polymer (A) and the polymer (B) and 5% by weight or less of the polymer (P) ( c) a heat-shrinkable polyamide laminated biaxially stretched film having a structure including at least two of these three layers and having a hot water shrinkage ratio at 95 ° C. of 15 to 35%. , A layer (d) made of a low-density polyethylene polymer, a linear low-density polyethylene polymer, an ethylene-vinyl acetate copolymer, or an (e) layer made of a polymer selected from an ionomer polymer is sequentially laminated. A heat-shrinkable laminated film capable of being heat-sealed. Polymer (A): Aromatic compound containing 70 mol% or more of polyamide constituent units consisting of m- and / or p-xylylenediamine and α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain. Polyamide polymer (B): Aliphatic polyamide polymer (P): Ionomer polymer or polyolefins grafted with unsaturated carboxylic acids, and polyolefins of the former 100 to 5% by weight and the latter 0 to 95% by weight. Mixed in range