JPH06255054A - Polyamide laminated biaxially oriented film - Google Patents

Abstract

PURPOSE:To obtain an excellent oxygen gas barrier, flexing resistance, toughness as a structure having a plurality of types of layers of a mixture of specific polymer B, specific polymers A, B and mixture of polymer having excellent flexing resistance of a mixture having the polymers A and B. CONSTITUTION:The polyamide laminated biaxially oriented film comprises two or more types of layers of a mixture of aromatic polyamide polymer A containing 70mol% or more of polyamide constituent unit of m and/or p-xylene diamine and 6-12C alpha-, omega-aliphatic dicarboxylic acid in a molecular chain and polymer P having more excellent flexing resistance than that of the polymer A of 1-10vol.%, a mixture of the polymer B, and the polymers A, B, and a mixture of the polymer P of 10vol.% or less. The polymer P dispersed in a flat plate state in the layer (a) of the polymer A has two or more of mean value of ten of dispersion index Z to be defined by Z=Y/X...(1), where X is a width of the film observed by an electron microscope by cutting a surface of the film in a vertical direction, and Y is total sum of measured values of length of the polymer P dispersed in the film width X.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyamide system which is excellent in oxygen gas barrier property, flex resistance, toughness, etc. and is suitable for a film for packaging foods, medical products, chemicals and the like which do not want to deteriorate the contents due to oxygen. The present invention relates to a laminated biaxially stretched film.

[0002]

2. Description of the Related Art Heretofore, unstretched films or stretched films of polyamide polymers have been used as various packaging materials, either alone or laminated with other films. However, the commonly used film made of an aliphatic polyamide polymer alone is excellent in mechanical properties such as tensile strength and flex pinhole resistance, but has a drawback that it is not sufficient in oxygen gas barrier property. . Therefore, in order to impart an oxygen gas barrier property to this film, a method of coating a vinylidene chloride polymer latex on the surface of the film to form 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 polymer latex has a drawback that it becomes cloudy when treated with hot water, and further, when it is incinerated, a compound containing chlorine is generated, which causes environmental pollution. It was also the cause. On the other hand, as a film having a good oxygen gas barrier property, an aromatic polyamide polymer containing a polyamide constitutional unit composed of m- and / or p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms as a main component is used. A raw material made from coalescence has been proposed. This film is
Although it is excellent in transparency and oil resistance, its use is limited because it is inferior in bending resistance.

In order to obtain a film having the advantages of both of the above polyamide-based polymers, that is, the tensile strength, flex resistance, and oxygen gas barrier property, two polyamide-based polymers are used. A method for producing a laminated biaxially stretched film by an inflation method, which is separately melt-extruded, has been proposed (JP-A-57-5).
1427). Further, a laminated film having a structure in which a layer containing an aromatic polyamide polymer as a main component is sandwiched between layers containing an aliphatic polyamide polymer as a main component has also been proposed (see JP-A-56-155762). ).

However, in the laminated biaxially stretched film proposed in the above publication, for example, if the proportion of the aromatic polyamide polymer is increased to improve the oxygen gas barrier property, the bending resistance of the laminated film is lowered. . Further, in order to improve the bending resistance and toughness, if the proportion of the aliphatic polyamide polymer is increased, the laminated film as a whole becomes thick and cannot be used for soft packaging, and has an oxygen gas barrier property,
Neither flex resistance is satisfactory.

[0006]

SUMMARY OF THE INVENTION In view of the above situation, the present invention provides a polyamide-based laminated biaxially stretched film having excellent oxygen gas barrier properties, excellent flex resistance, and toughness. To aim.

[0007]

Means for Solving the Problems The inventors of the present invention have completed the present invention as a result of extensive studies to solve the above problems. Therefore, the gist of the present invention is that the following polymer (A), polymer (B), mixture (C), and polymer (P) are used as raw materials, and they are composed of polymer (A) (a) Layer, composed of polymer (B) (b)
Of the layer and the layer (c) composed of the mixture (C), the polymer (P) is contained in the layer (a) in an amount of 1 to 10 vol% and in the layer (c) in an amount of 10 vol% or less. It is a structure including two or more types of layers including at least one (a) layer among the layers, and the polymer (P) in the (a) layer or the (a) layer and the (c) layer with respect to the surface of the film. When observed using an electron micrograph of a cross section cut in the vertical direction, it has a microstructure dispersed in a flat plate shape substantially parallel to the surface of the film, and has a flat plate shape in the (a) layer. Regarding the dispersed polymer (P) (hereinafter referred to as "flat plate"), the average value at any 10 points of the film having the dispersion index Z defined by the following formula (1) is 2 or more. Polyamide-based laminated biaxially stretched film.

Z = Y / X (1) where X is an electron micrograph of a cross section cut perpendicular to the surface of the film at an arbitrary observation location, and the width of the film in this observation area And Y means the sum of the measured values of the lengths of all the flat plates present in the layer (a) observed in the region of the width X of the film, which was observed using an electron micrograph. Polymer (A): Aromatic polyamide containing a polyamide constituent unit consisting of m- and / or 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. Polymer (B): Aliphatic polyamide Mixture (C): Mixture of polymer (A) and polymer (B) Polymer (P): A polymer having more excellent flex resistance than the polymer (A) Exist.

The present invention will be described in detail below. The main raw materials for the 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 polymer (A. The polymer (hereinafter, referred to as "polymer (P)") is more excellent in flex resistance than

The polymer (A), which is one type of polyamide polymer, comprises a polyamide constitutional unit composed of m- and / or p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms. It is a polymer containing 70 mol% or more 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 azeramide copolymer, metaxylylene / paraxylylene sepacamide copolymer And other copolymers.

In addition, 70 mol% or more of a polyamide structural unit containing m- or / and p-xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms is contained in the molecular chain. And a copolymer composed of other polyamide constituent components. Other polyamide constituent components include diamine components, dicarboxylic acid components and other components. Specific examples of the diamine component include
There are diamines such as aliphatic diamines such as hexamethylenediamine and 2,2,4-trimethylhexamethylenediamine, diamines containing heterocyclic rings or heteroatoms such as piperazine bispropylamine and neopentyl glycol bispropylamine, and dicarboxylic acids. Specific examples of the 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, and cyclic fatty acids such as 1,4-cyclohexanedigalbonic acid. Other components include lactams such as ε-caprolactam and ω-aminocarboxylic acids such as ε-aminocarboxylic acid.

Further, the polymer (A) may contain a polymer (D) compatible with the polymer (A) up to a range of 20% by weight. Examples of the polymer (D) that is compatible with the polymer (A) include polyamide polymers and other thermoplastic resins not exemplified above. The polymer (A) must have a polyamide constituent unit consisting of 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. . If it is out of this range, reach the target value of oxygen permeability (15 cc / m ² · 24H · atm or less under conditions of temperature 25 ° C and relative humidity 65%) to be applied to the finally obtained laminated film. No, it is not preferable. When the polymer (A) contains the polymer (D), the amount of the polymer (D) is 20.
When the content exceeds the weight%, it is not preferable for the same reason.

The 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 a homopolymer of ε-caprolactam, polyhexamethylene adipamide, and
Compound containing ε-caprolactam or hexamethylene adipamide as a main component and copolymerizable therewith 2 to 10 mol%
And the like.

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
It is preferable because it can be obtained at low cost and the biaxial stretching operation can be smoothly performed. The mixture (C) is a mixture of the polymer (A) and the polymer (B), but may be a mixture of virgin ones, or may have a nonstandard specification produced when a laminated film is produced. It may be a scrap mixture such as a film or a cut end material (edge trim) of the film side end, or may be a scrap mixture to which virgin is added. The mixing ratio of these two kinds 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 to have a water content of 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) is a polymer having more excellent flex resistance than the polymer (A), and functions as a flex resistance improver for the film. When an unstretched film made of itself was cut to a specific size, the number of pinholes was measured after repeated bending test with the next Gelbo Flex Tester, and the weight of 3/77 inch ² or less was measured. Refers to coalescence.

Here, the test by the Gerbo flex tester is performed as follows. An unstretched film having a thickness of 15 μ is cut into a size of 8 inches × 11 inches, and the cut film is left to condition for 24 hours or more under the condition of a temperature of 23 ° C. and a relative humidity of 50%. Tester (MIL-B-131
(According to the standard of C), the test film is wound into a cylindrical shape having a length of 8 inches, and one end of the wound cylindrical film is attached to the outer circumference of the disc-shaped fixed head of the tester, and the other end. Are fixed to the outer circumference of the disk-shaped movable head of the tester, and the movable head is opposed in parallel to the fixed head direction (the fixed head and the movable head are opposed by a distance of 7 inches). Along the axis 3.
Rotate 440 ° while approaching for 5 inches, then straighten for 2.5 inches without rotating, and then reverse these operations to return the movable head to the initial position for 1 stroke. A bending test as a cycle was performed at a speed of 40 cycles per minute for 3000 consecutive cycles, and then the fixed head of the tested film and 7 inch × 11 excluding the fixed part on the outer periphery of the movable head were tested.
Count the number of pinholes in the film within an inch. The polymer that can effectively achieve the object of the present invention,
The film must have physical properties such that the number of pinholes in the film after repeated bending test by this method is 3/77 inch ² or less.

Specific examples of the polymer (P) include, but are not limited to, modified polyolefins, a mixture of modified polyolefins and polyolefins, an ionomer polymer, an elastomer, or a mixture thereof. Not a thing. Specific examples of the polyolefins are homopolymers of olefins such as ethylene and propylene, and a mixture thereof, or a copolymer and a mixture thereof, for example, high density polyethylene,
Low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, etc. Can be mentioned.

The modified polyolefins refer to those obtained by graft-polymerizing unsaturated carboxylic acids with polyolefins as the main skeleton. Specific examples of the polyolefin as the main skeleton, ethylene, homopolymers of olefins such as propylene, and mixtures thereof, or copolymers and mixtures thereof, for example, high-density polyethylene, low-density polyethylene, Linear low density polyethylene,
Examples thereof include ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene and the like. Specific examples of unsaturated carboxylic acids, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, carboxylic acids such as citraconic acid, maleic anhydride, citraconic acid anhydride, acid anhydrides such as itaconic acid, Alternatively, a metal salt of an acid such as potassium acrylate or potassium methacrylate can be used. These unsaturated carboxylic acids are not limited to one kind, and two or more kinds may be mixed and used.

The content of unsaturated carboxylic acids in the modified polyolefin is preferably 0.02 to 4% by weight, more preferably 0.1 to 2% by weight. When the content of unsaturated carboxylic acids is less than 0.02% by weight, it cannot be uniformly mixed with the polyamide-based mixed polymer, and the obtained film becomes hazy, while 4% by weight on the other hand.
If the amount exceeds the above range, not only the production cost becomes high, but also the effect of improving the flex resistance of the obtained film is saturated. Therefore, the content of unsaturated carboxylic acids in the modified polyolefin exceeds 4% by weight. You don't have to.

An ionomer polymer is made of an olefin and an α, β-ethylenically unsaturated monomer having a carboxyl moiety, and the carboxyl moiety is considered to be an acid equivalent, and the carboxylic acid has a valence of 1 to 3. It is one that has been neutralized with metal ions. Specific examples of the olefin are polyethylene or a copolymer of ethylene and at least one α-olefin having 3 to 8 carbon atoms and a diolefin, for example, 1,4-hexadiene. Specific examples of the α, β-ethylenically unsaturated monomer having a carboxyl moiety include methacrylic acid, acrylic acid, maleic acid, maleic anhydride, fumaric acid and the like. The metal ions include zinc ions, sodium ions, lithium ions, potassium ions, magnesium ions and the like. The ionomer polymer is produced by a direct synthesis method of polymerizing an α-olefin and an olefin monomer having a carboxyl moiety, a grafting method of adding a monomer having a carboxyl moiety to an olefin skeleton, or the like.

As the elastomer, a polyamide-based elastomer such as polyether amide, polyether ester amide or polyester amide, an acrylic-based elastomer such as methyl acrylate, ethyl acrylate, methyl methacrylate or a copolymer of ethylene and ethylene. Or methacrylic elastomer, polystyrene phase at both ends,
Examples of the rubber intermediate phase include a styrene elastomer which is a block copolymer having a hydrogenated polyolefin and a polystyrene phase serving as a crosslinking point.

The polyamide-based laminated biaxially stretched film according to the present invention contains the polymer (P) in the layers (a) and (c). The content ratio of the polymer (P) contained in the layer (a) or the layer (c) is in the range of 1 to 10 vol% with respect to the total amount of all the polymers contained in the layer (a), (c).
1 for the total amount of all polymers contained in the layer
If it is less than 0% by volume and less than 1% by volume, the effect of improving the bending resistance is not obtained, and if it exceeds 10% by volume, the film becomes hazy, which is not preferable. A particularly preferred range is (a)
2 to 8 vol% in layer, 6 vol in layer (c)
% Or less.

The polymer (P) in the layers (a) and (c) of the polyamide-based laminated biaxially stretched film according to the present invention is an electron micrograph showing a cross section of the polymer (P) cut in a direction perpendicular to the surface of the film. It is necessary for the film to have a microstructure in which it is dispersed in a flat plate shape substantially in parallel with the surface of the film when observed by using. The flat plate may be the polymer (P) alone, or may be a flat plate in which the polyamide component is incorporated in an island shape.

The shape of the polymer (P) dispersed in the film is presumed to have a disk-like or elliptical disk-like microstructure when the film is observed from the surface. When a cross section cut in a direction perpendicular to the surface of the film is observed by using an electron micrograph, the polymer having a microstructure dispersed in a flat plate shape substantially in parallel with the surface of the film (P The microstructure in the (a) layer or the (a) layer and the (c) layer of (1) makes an ultrathin section of a cross section cut in a direction perpendicular to the surface of the film, and the surface of this ultrathin section is phosphotungsten. Transmission electron micrograph (magnification: 10,000) stained with acid and ruthenium oxide
It is possible to observe.

The cross section of the flat polymer (flat plate) shown in the electron micrograph is not limited to the maximum diameter of the disk, and is presumed to be the cut surface of various portions of the disk or elliptical disk.
There are various sizes. The attached FIG. 1 shows a model of an electron micrograph. In FIG.
1 is the (a) layer, 2 is the (b) layer, 3 is the (c) layer, and 4 to 10.
Is a flat plate dispersed in the (a) layer, 11 to 15 are (c)
Flat plate dispersed in the layer, X is the width of the film observed in the electron micrograph, y is the length of the flat plate 4, and t is the flat plate 4.
The thickness of each is shown.

According to the experiments conducted by the present inventors, it was found that the flat plate present in the layer (a) should satisfy certain conditions in order to effectively achieve the object of the present invention. The specific condition is that the flat plate in the (a) layer has an average value of 2 at any 10 points of the dispersion index Z defined by the following formula (1).
That is all. The dispersion index Z is, for example, in FIG. 1, the length of the flat plate 4 dispersed in the layer (a) is y, the length of the flat plate 5 is y5, and the length of the flat plate 6 is y.
6, the length of the flat plate 7 is y7, ... The length of the flat plate 10 is y1
When set to 0, the sum of the measured values of the lengths of all the flat plates observed in the (a) layer is Y (mm) (Y = y + y5 + y6 + y7
+ Y8 + y9 + y10), and the relationship between this and X (mm) is a numerical value that satisfies the following expression (1).

Z = Y / X (1) According to the experiments by the inventors, ultra-thin sections were prepared from the dispersion index Z at arbitrary 10 points on the film, and their microstructures were obtained by transmission electron micrographs. It is necessary that the dispersion index Z is calculated from the above formula (1) and the average value of the dispersion index Z at these 10 points is 2 or more.
If it is less than 2, the laminated biaxially stretched film of the product is inferior in bending resistance and is not preferable. The dispersion index Z does not have to exceed 25, and if it exceeds 25, the film becomes hazy, which is not preferable.

Further, according to the experiments by the present inventors, in order to effectively achieve the object of the present invention, its microstructure is observed by an electron micrograph of a cross section taken in a direction perpendicular to the surface of the film. At this time, the flat plate index ratio of the flat plate in the (a) layer must be 50% or more. Here, the flat plate index ratio refers to the film width X region observed by using an electron micrograph of an ultrathin section prepared by cutting in a direction perpendicular to the film surface at an arbitrary observation position. The relatively large flat plate, that is, the thickness of one flat plate is 5 to 200 nm, and the ratio of the length to the thickness of the flat plate is calculated based on the sum of the sectional areas of all the flat plates present in the layer (a). It means the ratio occupied by the sum of the cross-sectional areas of a plurality of flat plates having a length / thickness of 30 or more.

The plate index ratio is, for example, as shown in FIG.
(A) In the flat plates 4 to 10 dispersed in the layer 1, the thickness of the flat plate 4 is t, the thickness of the flat plate 5 is t5, the thickness of the flat plate 6 is t6, ... When the length is t10, the sum of the cross-sectional areas of all the flat plates present in the layer (a) (this is W) is W = (y × t + y5 × t5 +
y6 × t6 + ... + y10 × t10). Also,
A flat plate having a thickness of 5 to 200 nm and a ratio of length to thickness of the flat plate (length / thickness) of 30 or more is
Since these are 4, 6, 7, 9, and 10, the sum of the cross-sectional areas of these flat plates (which is N) is N = (y × t + y6 × t).
6 + y7 × t7 + y9 × t9 + y10 × t10). That is, the ratio of the length to the thickness of the flat plate (length / thickness) is 5 to 200 nm for one flat plate with respect to the total cross-sectional area of all the flat plates present in the layer (a). 50% of which is the sum of the cross-sectional areas of flat plates (plurality) whose number is 30 or more
The above is that N / W ≧ 50,
This means that a large proportion of the polymer (P) having a long and thin cross section is present in the layer (a) in the form of a flat plate. If the flatness index ratio is 50% or less, even if the polymer (P) is dispersed in a flat plate shape, the effect of improving the bending resistance of the laminated biaxially stretched film is small, which is not preferable. Plate index ratio is
It is particularly preferably 60% or more, and more preferably 70% or more, because the effect of improving the bending resistance of the biaxially stretched film is remarkable.

The dispersion state of the polymer (P) in the (a) layer and the (c) layer may be uniformly dispersed throughout the (a) layer and the (c) layer, or near the interface of each layer. Alternatively, it may be concentrated and dispersed in the central portion, and if the values of the dispersion index and the flat plate index ratio are satisfied in any state, the laminated biaxially stretched film of the product is resistant to oxygen gas while maintaining its resistance. Flexibility can be improved.

The three types of layers constituting the laminated biaxially stretched polyamide film according to the present invention include a layer (a) in which the polymer (P) is mixed with the polymer (A) and a polymer (B). (B) layer, and (c) layer obtained by mixing the polymer (P) with the mixture (C). The layered structure of the polyamide-based laminated film of the product is composed of two or more layers including at least one (a) layer of (a) layer, (b) layer, and (c) layer, and has 2 to 5 layers. It is better to select by range. Specific examples of the combination of layers and the number of layers in this case include (a) /
(B), (a) / (c), (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) / (b), (c) /
Examples thereof include (b) / (a) / (b) / (c), but are not limited thereto.

In order to mix the polymer (A) and the polymer (P) constituting the layer (a), a dry blending method, a method of melting the dry blended product with an extruder and pelletizing it, or the like is carried out. . Further, it is desirable to consider the extruder, melt line and the like as necessary so that the dispersion index and the flat plate index ratio match the numerical values defined by the present invention. For example, increase the compression ratio of the extruder, increase L / D, attach a mixing zone to the screw, use a twin-screw extruder, attach a cavity transfer mixer, make the screw shape a damflight type, static on the melt line It is desirable to consider how to attach a mixer or devise the extrusion temperature.

The polyamide-based laminated biaxially stretched film according to the present invention can be manufactured by a known method. First, a raw material comprising a polymer (B), a polymer (A) containing the polymer (P), and a mixture (C) containing the polymer (P) is substantially amorphous and not oriented. An unstretched laminated film is produced by the coextrusion method. Next, the unstretched laminated film is stretched by a tenter type sequential biaxial stretching, a tenter type simultaneous biaxial stretching, a tubular type simultaneous biaxial stretching, etc. so that the dispersion index and the flat plate index ratio satisfy the numerical values defined by the present invention. Depending on the method, it is stretched 2.5 to 5 times in both longitudinal and transverse directions.

Considering the object of the present invention, the polyamide-based laminated film according to the present invention has the following physical properties, that is, when the film thickness is about 15 μ, the oxygen permeability is 25 ° C. and the relative humidity is 65%. 15cc / m ² · 24H under conditions
-3000 atm by Gelvo Flex Tester for a test film that is less than atm and has a flex resistance of 23 ° C and a relative humidity of 50%.
Having the physical properties that the number of pinholes measured on the film after carrying out the cycle bending test (the details of the bending test are described above) is 15 pieces / 77 inch ² or less,
It is excellent in both oxygen gas barrier property and bending resistance, and it can be said that the purpose is achieved.

The total thickness of the laminated biaxially stretched polyamide film according to the present invention is preferably 10 μm or more and 40 μm or less. When the total thickness is less than 10 μ, the oxygen gas barrier property and the flex resistance are poorly balanced, and the abrasion resistance is also poor, so that a satisfactory film for packaging cannot be obtained. Also, 4
When it exceeds 0 μ, the film becomes hard, and when the sealant layer is further laminated, the entire film becomes very thick, which is not suitable for soft packaging. The polyamide-based laminated biaxially stretched film of the present invention can be used for bag-like products by laminating a sealant layer.

[0038]

EXAMPLES The contents and effects of the present invention will be described below in more detail with reference to 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 each of the following methods. Table 1 shows the layer structure of the film and the evaluation results.

<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 resistance (number of pinholes / 77 inch)
² )> A film cut into a size of 8 inches x 11 inches is left standing for 24 hours or more under the condition of a temperature of 23 ° C and a relative humidity of 50% to be conditioned, and a Gelbo flex tester (manufactured by Rigaku Kogyo, No. .901 type) (MIL
(B-131C standard) was used to repeat the bending test as follows, and the number of pinholes was measured.

The rectangular test film is wound into a cylindrical shape having a length of 8 inches, one end of the wound cylindrical film is on the outer circumference of the disk-shaped fixed head of the tester, and the other end is the disk-shaped of the tester. The movable head is fixed to the outer periphery of the movable head, and the movable head is parallel to the direction of the fixed head along the axis of both heads (the fixed head and the movable head face each other at a distance of 7 inches). Rotate 440 ° while approaching for 0.5 inch, then go straight for 2.5 inches without rotating, and then reverse these operations to return the movable head to the initial position. A bending test of one cycle was continuously performed at a speed of 40 cycles per minute for 3000 cycles, and then fixed to the outer periphery of the fixed head and the movable head of the tested film. The pin number of holes generated in a portion of the 7 inches × 11 inches excluding the amount was measured.

<Dispersion index> An ultrathin section was prepared by cutting in the direction perpendicular to the surface of the film, and a sample was prepared by the ultrathin method dyed with phosphotungstic acid and ruthenium oxide.
Approximately 160m when observed with a transmission electron microscope at a magnification of 10,000 times
An electron micrograph of m, about 220 mm was taken, and the width of the film of the cut ultrathin section, that is, the lateral width of the area photographed was X (mm), and the (a) layer observed in the electron micrograph. When the sum of the measured values of the lengths of all the flat plates present therein was Y (mm), Z represented by Z = Y / X was calculated.

Then, such Z was calculated at 10 arbitrary observation points on the film, and the average of these values was used as the dispersion index.

<Plate index ratio> The thickness and length of each plate in the layer (a) observed in the region of the film width X of the ultrathin section in the electron micrograph taken when calculating the dispersion index. Was measured. The thickness of one flat plate is 5 with respect to the sum of the cross-sectional areas of all the flat plates present in the layer (a) (cross-sectional area of each flat plate = thickness of each flat plate x length of each flat plate). It is defined as the ratio of the sum of the cross-sectional areas of the flat plates even though the ratio of the length to the thickness of the flat plate (length / thickness) is 30 or more in the range of up to 200 nm.

Example 1 A laminated biaxially stretched film having the following constitution was obtained. Film layer structure: (b) layer about 6 μ / (a) layer about 4 μ /
(C) Layer About 5 μm Resin constituting layer (a): content ratio of polymer (P) to polymer (A) 3.2 VOL% (b) Resin constituting layer: polymer (B) (c) ) Resin constituting layer: polymer (A) and polymer (B)
And the mixing ratio of the polymer (P) with respect to the total polymer is 1.3 vol%.

Polymer (A): polymeta-xylylene adipamide (manufactured by Mitsubishi Gas Chemical Co., Inc., MXD-nylon 60)
07) Polymer (B): Poly-ε-caproamide (Novamid 1022, manufactured by Mitsubishi Kasei Co., Ltd.) Mixture (C): Film trimmed at the ear trim end of the polymer Polymer (P): 83 mol% ethylene content, 20% by weight of a modified ethylene-propylene copolymer obtained by modifying an ethylene-propylene copolymer having a melt flow index of 1.0 g / 10 minutes with maleic anhydride, a vinyl acetate content of 8% by weight, a melt flow index of 1. 5 g /
80% by weight of ethylene-vinyl acetate copolymer which is 10 minutes
The above-mentioned laminated biaxially stretched film is obtained by stretching a previously prepared unstretched laminated film 3 times in the machine direction and 3 times in the transverse direction.

The composition of the obtained film, the oxygen permeability measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and the plate index ratio from the electron micrograph observation of the ultrathin section are shown in the table. Shown in 1. Further, FIG. 2 shows an electron micrograph (magnification: 10,000 times) of an ultrathin section cut from the film obtained in this example.

Example 2 The same laminated biaxially stretched film as in Example 1 was obtained except that the description in Example 1 was changed as follows. Layer structure of film: (b) layer about 10 μ / (a) layer about 4 μ Film structure of the obtained film, oxygen permeability measured by the above-mentioned method, pinhole number, and electron micrograph observation of ultrathin section The results of calculating the dispersion index and the flat plate index ratio from Table 1 are shown in Table 1, respectively.

Example 3 The same laminated biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Layer structure of film: (c) layer about 10 μ / (a) layer about 4 μ Film structure of the obtained film, oxygen permeability measured by the above-mentioned method, pinhole number, electron micrograph observation of ultrathin section The results of calculating the dispersion index and the flat plate index ratio from Table 1 are shown in Table 1, respectively.

Example 4 The same laminated biaxially stretched film as in Example 1 was obtained except that the following description was made in Example 1. Layer structure of film: (b) layer about 5.5 μ / (a) layer about 4
μ / (b) layer about 5.5μ Polymer (P): A mixture of 20% by weight of a modified ethylene-butene copolymer obtained by modifying an ethylene-butene copolymer with maleic anhydride and 80% by weight of an ethylene-vinyl acetate copolymer. Table 1 shows the composition of the obtained film, the oxygen permeability measured by the above-described method, the number of pinholes, the dispersion index and the plate index ratio calculated from the electron micrograph observation of the ultrathin section. .

Example 5 The same laminated biaxially stretched film as in Example 1 was obtained except that the following description was made in Example 1. Layer structure of film: (c) layer about 5.5 μ / (a) layer about 4
μ / (c) Layer About 5.5 μ (a) Resin constituting layer: Content of polymer (P) in polymer (A) 6.4 VOL% Film composition of the obtained film, as described above Table 1 shows the results of calculating the dispersion index and the flat plate index ratio from the oxygen transmission rate measured by the method, the number of pinholes, and the electron micrograph observation of ultrathin sections.

Example 6 The same laminated biaxially stretched film as in Example 1 was obtained except that the following description was made in Example 1. Resin constituting the layer (a): content ratio of the polymer (P) to the polymer (A) 1.6 VOL% Polymer (P): modified ethylene obtained by modifying an ethylene-propylene copolymer with maleic anhydride A mixture of 20% by weight of propylene copolymer and 80% by weight of low-density polyethylene. Composition of the obtained film, oxygen permeability measured by the above-mentioned method, pinhole number, electron micrograph of ultrathin section. Table 1 shows the results of calculating the dispersion index and plate index ratio from the observation.

Example 7 The same laminated biaxially stretched film as in Example 1 was obtained except that the following description was made in Example 1. Polymer (P): a mixture of 20% by weight of a modified ethylene-propylene copolymer obtained by modifying an ethylene-propylene copolymer with maleic anhydride and 80% by weight of a linear low-density polyethylene. Table 1 shows the composition of the film, the oxygen transmission rate measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and the flat plate index ratio from the observation of an electron micrograph of an ultrathin section.

Example 8 The same laminated biaxially stretched film as that of the same example was obtained except that the following description was made in the description of Example 1. Polymer (P): a mixture of 20% by weight of a modified ethylene-propylene copolymer obtained by modifying an ethylene-propylene copolymer with maleic anhydride and 80% by weight of polypropylene, the film composition of the obtained film, Table 1 shows the results of calculating the oxygen transmission rate, the number of pinholes, the dispersion index and the flat plate index ratio from the electron micrograph observation of the ultrathin section, which were measured by the above method.

Example 9 The same laminated biaxially stretched film as in Example 1 was obtained except that the description in Example 1 was changed as follows. Polymer (P): 100% by weight of a modified ethylene-propylene copolymer obtained by modifying an ethylene-propylene copolymer with maleic anhydride, the film composition of the obtained film, the oxygen permeability measured by the method described above, and the pin Table 1 shows the results of calculating the dispersion index and plate index ratio from the number of holes and electron micrograph observation of ultrathin sections.

Example 10 The same laminated biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Polymer (P): Daiamide (manufactured by Daicel Hüls)
100% by weight, diamide is a block copolymer of polylaurinlactam and polyether.

The composition of the obtained film, the oxygen transmission rate measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and plate index ratio from the electron micrograph observation of the ultrathin section are shown in the table. Shown in 1.

Example 11 The same laminated biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Polymer (P): 100% by weight of Baymac (manufactured by DuPont), Baymac is a copolymer of methyl acrylate and ethylene, and is a polymer forming a cross-linking point by a copolymer of monomers having a carboxyl group.

The composition of the obtained film, the oxygen transmission rate measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and the plate index ratio from the observation of an electron micrograph of an ultrathin section are shown in the table. Shown in 1.

Example 12 The same laminated biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Polymer (P): Kraton G (manufactured by Shell Chemical Co.) 100
% By weight, Kraton G is a block copolymer having a polystyrene phase at both ends and a hydrogenated polyolefin as a rubber intermediate phase, and the polystyrene phase serving as a crosslinking point.

The composition of the obtained film, the oxygen transmission rate measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and plate index ratio from the electron micrograph observation of the ultrathin section are shown in the table below. Shown in 1.

Example 13 The same laminated biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Polymer (P): Ionomer polymer (Mitsui DuPont
Polychemical Co., Ltd., Himilan AM7315) 100% by weight Film composition of the obtained film, oxygen transmission rate measured by the above-mentioned method, pinhole number, dispersion index, tabular index ratio from electron micrograph observation of ultrathin section Table 1 shows the results of the calculation.

Example 14 The same laminated biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Polymer (P): ethylene vinyl alcohol (Kuraray Co., EP-E105, ethylene fraction 44 mol%) 100
The composition of the obtained film, the oxygen transmission rate measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and the plate index ratio from the electron micrograph observation of the ultrathin section are shown in Table 1, respectively. Shown in.

Comparative Example 1 The same biaxially stretched film as in the same example was obtained except that the following description was made in the description of Example 1. Layer composition of film: (a) Layer about 15μ Film composition of the obtained film, oxygen transmission rate measured by the above-mentioned method, pinhole number, dispersion index, plate index ratio from electron micrograph observation of ultrathin section Table 1 shows the results of the calculation.

Comparative Example 2 The same laminated biaxially stretched film as in the same example was obtained except that the following was changed in the description of Example 1. Resin constituting the layer (a): content ratio of the polymer (P) in the polymer (A) 0.54 VOL% Film constitution of the obtained film, oxygen permeability measured by the above-mentioned method, pinhole Table 1 shows the results of calculating the dispersion index and the plate index ratio from the observation of the number and the electron micrograph of the ultrathin section.

Comparative Example 3 The same laminated biaxially stretched film as in the same example was obtained except that the following was changed in the description of Example 1. Polymer (P): 100% by weight of Septon (manufactured by Kuraray Co., Ltd.),
Septon is a block copolymer having a polystyrene phase at both ends and polyisoprene as a rubber intermediate phase, and the polystyrene phase serves as a crosslinking point.

The composition of the obtained film, the oxygen transmission rate measured by the above-mentioned method, the number of pinholes, and the results of calculating the dispersion index and plate index ratio from the electron micrograph observation of the ultrathin section are shown in the table below. Shown in 1.

Comparative Example 4 The same laminated biaxially stretched film as in Example 1 was obtained except that the following was changed in the description of Example 1. Polymer (P): 100% by weight of polystyrene The composition of the obtained film, the oxygen permeability measured by the above-mentioned method, the number of pinholes, the dispersion index and the tabular index ratio from the electron micrograph observation of the ultrathin section are shown. The calculated results are shown in Table 1.

Comparative Example 5 Film Layer Structure: Vinylidene chloride-coated biaxially stretched nylon film About 17 μm (Mitsubishi Kasei Polytech Co., Ltd.)
Santonil SG, manufactured by Co., Ltd.) Table 1 shows the results of measuring oxygen permeability and flex resistance by the methods described above.

[0070]

[Table 1]

In Table 1, each abbreviation has the following meaning. EVA: ethylene-vinyl acetate copolymer LDPE: low-density polyethylene LLDPE: linear low-density polyethylene Modified Et-Pr: ethylene-propylene copolymer modified with maleic anhydride Modified Et-Bt: ethylene-butene modified with maleic anhydride Copolymer Diamide: Trade name of polyamide elastomer from Daicel Hüls Baymac: Trade name of acrylic elastomer from DuPont Clayton G: Trade name of hydrogenated styrene block copolymer from Shell Chemical Co., Ltd. Ionomer polymer: Mitsui DuPont・ Himilan AM7315 Septon manufactured by Polychemical Co., Ltd .: trade name of a styrene block copolymer composed of a polystyrene phase of Kuraray Co., Ltd. and a polyisoprene phase as a rubber intermediate phase.

From Table 1, the polyamide-based laminated biaxially stretched film according to the present invention has oxygen gas barrier properties and flex resistance within the intended numerical ranges, and in particular has excellent flex resistance, It can be seen that the film has the oxygen gas barrier property within the target numerical value, but the flex resistance is outside the target numerical value range.

[0073]

INDUSTRIAL APPLICABILITY The present invention has particularly remarkable effects as follows, and its industrial utility value is extremely large. 1. The polyamide-based laminated biaxially stretched film according to the present invention has excellent oxygen gas barrier properties, excellent flex resistance, and toughness. Therefore, it is suitable for a film for packaging foods, medical products, medicines, etc., which do not like the deterioration of the contents due to oxygen.

[Brief description of drawings]

FIG. 1 is a model view of an electron micrograph of an ultrathin section.

FIG. 2 is a 10,000 × electron micrograph of the ultrathin section of Example 1.

[Explanation of symbols]

1 (a) layer 2 (b) layer 3 (c) layer 4-10 Flat plate of polymer (P) dispersed in (a) layer 11-15 Flat plate in (c) layer Plate of dispersed polymer (P) X Width of film observed by electron micrograph y Length of plate 4 t Thickness of plate 4

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[Procedure amendment]

[Submission date] March 25, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (2)

[Claims] 1. A polymer (A), a polymer (B), a mixture (B), a mixture (C), and a polymer (P), which are used as raw materials, as a raw material. ) Consists of (b)
Of the layer and the layer (c) composed of the mixture (C), the polymer (P) is contained in the layer (a) in an amount of 1 to 10 vol% and in the layer (c) in an amount of 10 vol% or less. It is a structure including two or more types of layers including at least one (a) layer among the layers, and the polymer (P) in the (a) layer or the (a) layer and the (c) layer with respect to the surface of the film. When observed using an electron micrograph of a cross section cut in the vertical direction, it has a microstructure in which it is dispersed in a flat plate shape substantially parallel to the surface of the film, and is dispersed in a flat plate shape in the (a) layer. Of the polymer (P) (hereinafter, referred to as a “flat plate”) having a dispersion index Z defined by the following formula (1), the average value at any 10 positions is 2 or more. Characteristic polyamide-based laminated biaxially stretched film. Z = Y / X (1) Here, X is an electron micrograph of a cross section taken in a direction perpendicular to the surface of the film at an arbitrary observation location, and the width of the film in this observation area is defined as Y Means the sum of the measured values of the lengths of all the flat plates present in the layer (a) observed in the region of the width X of the film, which were observed using an electron micrograph. Polymer (A): Aromatic polyamide containing a polyamide constituent unit consisting of m- and / or 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. Polymer (B): Aliphatic polyamide Mixture (C): Mixture of polymer (A) and polymer (B) Polymer (P): Polymer having better flex resistance than the polymer (A) 2. The polyamide-based biaxially stretched film according to claim 1, wherein the flat index of the polymer (P) dispersed in the layer (a) is 50% or more. Here, the flat plate index ratio is observed in a region of width X of the film, which is observed by using an electron micrograph of a cross section cut in a direction perpendicular to the surface of the film at an arbitrary observation location (a).
1 for the sum of the cross-sectional areas of all the flat plates present in the layer
This means the ratio of the sum of the cross-sectional areas of a plurality of flat plates in which the thickness of each flat plate is 5 to 200 nm and the ratio of the length to the thickness of the flat plate (length / thickness) is 30 or more.