JP4861672B2 - Straight-cut polyamide laminated film and method for producing the same - Google Patents

Description

  The present invention has excellent straight-cut properties, low hot water shrinkage, good thickness accuracy, and excellent gas barrier properties, and is suitable as a base film for packaging bags such as foods, chemicals, and industrial products. The present invention relates to a linear-cutting polyamide-based laminated film and a method for producing the same.

  Films mainly composed of polyamide polymers such as nylon 6 and laminated films composed of polyamide polymers as layers are excellent in tensile strength and impact strength. It is manufactured and sold in various forms by secondary processing into packaging bags.

  2. Description of the Related Art In recent years, easy-open packaging that can be easily opened as a packaging form has attracted attention from the viewpoint of consumer convenience, barrier-free and universal design. Examples of the means for improving the openability include a method of notching the heat seal portion, a method called magic cut (registered trademark), and a method of finely scratching the heat seal portion. However, these methods are only a trigger for tearing, and when tearing from this notch, they may not tear straight, or a large force may be required for tearing.

Therefore, a packaging material that is a bag made of a composite film composed of a functional resin film such as nylon and a sealant, etc., that tears straight when the film is torn and does not require a large force to tear. It has been demanded. In addition to basic properties such as strength and gas barrier properties, the properties required for the functional resin film used in such packaging materials include straight cuts that can be cut straight, easy opening that can be easily opened even with a small force, etc. Is mentioned.
When opening a packaging bag using a film that is inferior in the above-mentioned linear cutability and easy-openability, a trouble that a large force is required for tearing or tearing linearly often occurs. In such a case, the contents cannot be taken out, or the contents are scattered and wasted at the same time as opening, and especially when the contents are liquid, semi-fluid or powdery, Accidents that contaminate and the like are likely to occur.

Here, as a means for imparting unsealing property to a functional resin film itself such as nylon, there is a method in which a plurality of polyamide resins are mixed and linear cut property is imparted by these phase separation structures. For example, Patent Document 1 is a film having a three-layer structure including nylon 6 and polymetaxylylene adipamide (hereinafter referred to as “MXD6”), and the mass ratio of the front and back layers is nylon 6 / MXD6 = 60 to 95/40. To 5 and a mass ratio of the inner layer of nylon 6 / MXD6 = 40 to 85/60 to 15 is melted and extruded, and both MD and TD are 2. using the tubular simultaneous biaxial stretching method. An easy tear film stretched 8 times or more has been proposed.
However, the film formed by the tubular simultaneous biaxial stretching method has a large thickness fluctuation rate in the width direction, and due to this thickness fluctuation, wrinkles occur, tarmi occurs, printing registration shifts, and the film path is changed. This causes problems such as meandering and shifting of the printing pitch, and troubles during printing and lamination are likely to occur.
A sequential biaxial stretching method is known as one of the methods for forming a film with good thickness accuracy, but the above-mentioned polyamide-based film is subjected to a sequential biaxial stretching method and a stretching ratio of 2.8 times or more for both MD and TD. When the film was stretched, there was a problem that the linear cutability at the end of the obtained film was lowered mainly due to the bowing phenomenon.
Furthermore, in patent document 1, since there is little content of MXD6 of each layer, sufficient gas barrier property is not obtained, but it uses for the use which requires high gas barrier property from a viewpoint of the preservation | save of the contents and the improvement of a shell life. It becomes impossible film.

  Moreover, in patent document 2, it consists of a mixture of nylon 6 / MXD6 = 80-95 / 20-5 (mass ratio), and the biaxial orientation which has the linear cut property which disperse | distributed the shape of the dispersion particle of MXD6 to the specific shape. Polyamide films have been proposed. However, when the mixing ratio of MXD6 is 20% by mass or less, the linear cut property may be insufficient and the gas barrier property is also insufficient.

Japanese Patent No. 2661843 Japanese Patent No. 2971306

  Therefore, the present invention provides a linear-cutting polyamide-based laminated film having excellent linear cut property, low hot water shrinkage, good thickness accuracy, and excellent gas barrier property, and a method for producing the same. Objective.

In view of the current situation, the present inventors have made extensive studies and have found a polyamide-based film that can solve the conventional problems.
That is, the present invention provides the following linear-cutting polyamide-based laminated film and a method for producing the same.
1. The layer (a) containing 55 to 79% by mass of the aliphatic polyamide polymer (A) and 21 to 45% by mass of the aromatic polyamide polymer (B), and 90 to 90% of the aromatic polyamide polymer (B). (B) layer containing 100% by mass, each of which is a laminated film having a linear cut property (absolute value of deviation from a straight line when a straight line is drawn on MD and 200 mm is split), and is 95 mm or less, 95 The hot water shrinkage in the film flow direction (MD) at 3.0 ° C. for 5 minutes is 3.0% or less, the thickness fluctuation rate in the film width direction (TD) is 10% or less of the average thickness, and further 25 ° C. × 50 A straight-cut polyamide-based laminated film having an oxygen permeability of 80 fmol / (m ² · sec · Pa) or less under the condition of% RH.
2. 2. The linear-cutting polyamide-based laminated film according to 1 above, wherein the aliphatic polyamide polymer (A) is nylon 6 and the aromatic polyamide polymer (B) is polymetaxylylene adipamide.
3. (B) The linear-cutting polyamide-based laminated film according to any one of 1 or 2 above, wherein the layer has a thickness of 2 to 7 μm.
4). An unstretched film extruded from a flat die is stretched by a tenter-type sequential biaxial stretching method at a stretching ratio of less than 2.8 times in MD and 2.8 times in TD, and then at least 200 ° C. and the above aliphatic polyamide 4. The linear cut property according to any one of 1 to 3 above, wherein heat setting is performed at a temperature not higher than 10 ° C. from an extrapolated melting start temperature (measured according to JIS K 7121) of the polymer (A). A method for producing a polyamide-based laminated film.
5. 5. A method for producing a linearly cutable polyamide-based laminated film, wherein the MD described in 4 above has a draw ratio of 2.4 times or more.
6). 4. A laminate film, wherein the straight-cut polyamide-based laminate film according to any one of 1 to 3 is a constituent of a laminate.
7). A bag comprising the laminate film as described in 6 above.

  ADVANTAGE OF THE INVENTION According to this invention, while having the outstanding linear cut property, the low hot-water shrinkage property, favorable thickness precision, and also the linear cut property polyamide-type laminated film provided with the outstanding gas barrier property, and its manufacturing method can be provided.

Hereinafter, the present invention will be described in detail, but the scope of the present invention is not limited to the embodiments described below.
First, the linear-cutting polyamide-based laminated film of the present invention is a laminated film having at least one (a) layer and (b) layer, and (a) the layer is an aliphatic polyamide polymer (A), The aromatic polyamide polymer (B) is included at a specific ratio, and the layer (b) includes the aromatic polyamide polymer (B) at a specific ratio.
Here, as the layer structure, a two-layer structure (a) / (b), a three-layer structure (a) / (b) / (a), (b) / (a) / (b), (A) / (c) / (b) / (c) / (a), (b) / (c) / (a) / (c) / (b ) And the like, but the three-layer configuration of (a) / (b) / (a) is preferable from the viewpoint of the productivity of the laminated film and the secondary processability such as laminating to the bag. Used for.

  The aliphatic polyamide polymer (A) used for the linear-cutting polyamide-based laminated film of the present invention is not particularly limited, but is a ring-opening polymer of a cyclic lactam, a polycondensate of an aminocarboxylic acid, a dicarboxylic acid and a diamine. And polycondensates thereof. Specifically, a homopolymer of ε-caprolactam called nylon 6 or polyhexamethylene adipamide called nylon 66 can be obtained at low cost, and the stretching operation can be performed smoothly. To preferred.

Further, the aromatic polyamide polymer (B) is not particularly limited, but 70 mol of a polyamide constituent unit composed of xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain. % Or more can be used.
Specifically, homopolymers such as polymetaxylylene adipamide, polymetaxylylene pimeramide, polymetaxylylene azeramide, polyparaxylylene azeramide, polyparaxylylene decanamide, metaxylylene / paraxylylene azamide Examples of the copolymer include a pamide copolymer, a metaxylylene / paraxylylene pimeramide copolymer, a metaxylylene / paraxylylene azelamide copolymer, and a metaxylylene / paraxylylene sepacamide copolymer. Polymetaxylylene adipamide (hereinafter referred to as “MXD6”) is preferable because it has excellent basic properties such as strength and gas barrier properties, and is relatively easy to obtain industrially.

Other polyamide constituents include nylon salts of diamines and dicarboxylic acids, lactams such as ε-caprolactam, ω-aminocarboxylic acids such as ε-aminocarboxylic acid, and the like.
The diamines that are the components of the nylon salt include aliphatic diamines such as hexamethylene diamine and 2,2,4-trimethylhexamethylene diamine, heterocycles or heteroatoms such as piperazine bispropylamine and neopentylglycol bispropylamine. Dicarboxylic acids include aliphatic dicarboxylic acids such as adipic acid, azelaic acid and sebacic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and 1,4-cyclohexanedigalbonic acid. And cycloaliphatic dicarboxylic acids.

The content ratio of the aliphatic polyamide polymer (A) and the aromatic polyamide polymer (B) in the layer (a) is 55 to 79% by mass of the aliphatic polyamide polymer (A), and the aromatic polyamide polymer. It is important that (B) is 21 to 45% by mass. When the aromatic polyamide polymer (B) is within this range, the resulting film has good linear cut properties, and a significant reduction in impact strength can be suppressed. When the content ratio of the aromatic polyamide polymer (B) exceeds 45% by mass, there is a problem that not only the linear cutting property is deteriorated but also the impact strength is greatly reduced.
Here, the mixture of the aliphatic polyamide polymer (A) and the aromatic polyamide polymer (B) is a mixture of raw material polymers (pellets and the like), and when producing the polyamide-based film of the present invention on these. It may be a mixture of non-standard film or cut end material (ear trim) that is generated on the surface.

  Moreover, it is important that the content rate of the aromatic polyamide polymer (B) of the said (b) layer is 90-100 mass%. If the aromatic polyamide polymer (B) is 90% by mass or more, sufficient gas barrier properties can be imparted to the film. Here, the (b) layer may contain a small amount (about 10% by mass or less) of the aliphatic polyamide polymer (A).

  In the present invention, the adhesive layer (c) layer may be provided between the (a) layer and the (b) layer from the viewpoint of interlayer adhesion and the like. Although there is no restriction | limiting in particular as a component which comprises an adhesive layer, The mixture of the said aliphatic polyamide polymer (A) and the said aromatic polyamide polymer (B), polyolefin-type, polyester-type adhesive resins, etc. are used. be able to.

A bending-resistant pinhole property improving material can be added to the linear-cutting polyamide-based laminated film of the present invention, whereby the bending-resistant pinhole property can be improved. Examples of the bending-resistant pinhole improving material include polyolefins, polyamide elastomers, and polyester elastomers.
Examples of polyolefins include those containing 50 mass% or more of polyethylene units and / or polypropylene units in the main chain, and may be graft-modified with maleic anhydride or the like. As structural units other than the polyethylene unit and the polypropylene unit, vinyl acetate or a partially saponified product thereof, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, or a partial metal neutralized product thereof (ionomers), butene 1-alkenes such as alkadienes, styrene and the like. Polyolefins may contain a plurality of these structural units.

Examples of polyamide elastomers include polyamide block copolymers such as polyether amide and polyether ester amide. Examples of the amide component include nylon 6, nylon 66, nylon 12, and the like. Examples thereof include oxytetramethylene glycol, polyoxyethylene glycol, polyoxy-1,2-propylene glycol and the like, and a copolymer having polytetramethylene glycol and polylauryl lactam (nylon 12) as main components is preferable. Further, a combination of a small amount of dicarboxylic acids such as dodecanedicarboxylic acid, adipic acid and terephthalic acid as an optional component may be used.
Examples of polyester elastomers include polyether ester elastomers combining polybutylene terephthalate and polytetramethylene glycol, and polyester ester elastomers combining polybutylene terephthalate and polycaprolactone.
These bending-resistant pinhole improving materials may be used alone or in combination of two or more.

  In the present invention, the addition amount of the bending-resistant pinhole property improving material is about 0.1 to 10% by mass from the viewpoint of the balance between the effect of improving the bending-resistant pinhole property and the decrease in transparency when formed into a film. It is. Here, as the aliphatic polyamide polymer (A) and the aromatic polyamide polymer (B) containing the bending pinhole resistance improving material, those obtained by dry blending these at a predetermined ratio, or the dry blend product is extruded in advance. It may be any of those pelletized after being melt-mixed by a machine.

  In addition, the raw material polyamide polymer and the polyamide mixed composition described above may be appropriately added with a lubricant, an antistatic agent, an antioxidant, an antiblocking agent, a stabilizer, and a dye within a range not exceeding the gist of the present invention. Various additives such as pigments and inorganic fine particles can be added. Specific examples include impact modifiers (such as elastomers), anti-blocking agents (such as inorganic fillers), water repellents (such as ethylene bisstearic acid esters), and lubricants (such as ethylene bisstearic acid amides).

  When using the linear-cutting polyamide-based film of the present invention as a packaging bag, from the viewpoint of maintaining the quality of the contents and preventing spoilage, further laminating a gas barrier resin layer, metals such as aluminum, silicon dioxide, The gas barrier property and moisture proof property can be further improved by vapor-depositing a metal oxide such as alumina and applying a gas barrier coating agent.

  The linear-cutting polyamide-based laminated film of the present invention includes a non-standard film generated when the linear-cutting polyamide-based laminated film of the present invention is produced, as necessary, within the range not exceeding the gist of the present invention. A cut end material (ear trim) can be added to each of the layers (a), (b), and (c), or a plurality of layers.

In the layer structure of the linear-cutting polyamide-based laminated film of the present invention, the thickness of the (b) layer is preferably 2 to 7 μm, more preferably 3 to 6 μm. Here, when 2 or more layers are comprised in a laminated | multilayer film, it is preferable that the total thickness exists in the said range.
Here, when the thickness of the layer (b) is 2 μm or more, the oxygen permeability under the condition of 25 ° C. × 50% RH is easily achieved at 80 fmol / (m ² · sec · Pa) or less, and at 7 μm or less. If it exists, there is little fall of a linear cut property, and since mechanical strength is also favorable, it is preferable.

Next, it is important that the linear-cutting polyamide-based film of the present invention has the following characteristics (1) to (4), which are mainly composed of the above-described aliphatic polyamide polymer (A) in each layer. It can be controlled by the content ratio with the aromatic polyamide polymer (B) and the film production conditions (drawing ratio, heat setting temperature, etc.) described later.
(1) It is necessary that the linear cut property (absolute value of the deviation from the straight line when a straight line is drawn on the MD and split by 200 mm) is 5.0 mm or less. Here, if the straight-cut property is 5.0 mm or less, it can be torn linearly when opening a packaging bag or the like, and the contents cannot be taken out, or the contents can be prevented from scattering simultaneously with opening. .
(2) It is necessary that the hot water shrinkage in the flow direction (MD) of the film at 95 ° C. × 5 minutes is 3.0% or less. Here, if the hot water shrinkage rate of MD is 3.0% or less, it is possible to suppress the occurrence of troubles such as pitch deviation due to heat shrinkage in processes such as printing and laminating.
(3) The thickness variation rate in the width direction (TD) of the film needs to be 10% or less of the average thickness. Here, if the thickness variation rate is 10% or less of the average thickness, the occurrence of wrinkles due to thickness unevenness, the occurrence of tarmi, the misregistration of printing, the meandering of the film path and the deviation of the printing pitch, etc. The occurrence of trouble can be suppressed.
(4) The oxygen permeability under the condition of 25 ° C. × 50% RH needs to be 80 fmol / (m ² · sec · Pa) or less. Here, if the oxygen permeability is 80 fmol / (m ² · sec · Pa) or less, a sufficient gas barrier property can be obtained, and a high gas barrier property is required from the viewpoints of preservation of contents and improvement of shell life. Can be used for applications.

Hereinafter, a production method suitable for obtaining the linearly cutable polyamide-based laminated film of the present invention will be described.
That is, using a polyamide-based polymer as a raw material, a film that is substantially amorphous and not oriented (hereinafter referred to as “unstretched film”) is usually produced by a coextrusion method. The unstretched film is produced, for example, by melting the above raw material with 1 to 7 extruders (preferably a single-screw extruder from the viewpoint of controlling the phase separation structure), extruding from a flat die, and then rapidly cooling. Thus, a coextrusion method for forming a flat unstretched film can be employed. The raw material to be supplied to the extruder may be pellets prepared by previously melting and kneading pellets of both the aliphatic polyamide polymer (A) and the aromatic polyamide polymer (B) in a biaxial kneader, A mixed pellet obtained by dry blending the pellets of both resins with a blender may be used.

Next, the unstretched film is stretched in the biaxial direction in terms of stretching effect, film strength, and the like in the film flow direction (MD) and the width direction (TD) which is the orthogonal direction.
As a biaxial stretching method, it is important in the present invention to stretch by a tenter type sequential biaxial stretching method. In the case of the tenter type sequential biaxial stretching method, the unstretched film is heated to a temperature range of 50 to 110 ° C. and is less than 2.8 times in the longitudinal direction by a roll type longitudinal stretching machine, preferably 2.4 times or more, It is important to stretch to less than 2.8 times, more preferably from 2.60 times to 2.74 times.
Here, when the longitudinal stretching ratio is less than 2.4 times, uneven stretching occurs and the thickness becomes non-uniform, the strength of the film decreases due to insufficient orientation, and the linear cut property also decreases. Furthermore, if the stretching unevenness is significant, film formation may not be possible. On the other hand, when the longitudinal stretch ratio is 2.8 times or more, the problem of a decrease in linear cutability at the end of the obtained biaxially stretched film is likely to occur due mainly to the bowing phenomenon.

The longitudinally stretched film stretched by the above method is then held at its end by a tenter clip, and is 2.8 times or more in TD within a temperature range of 60 to 140 ° C., preferably 2. It is important to stretch at 8 times or more and 5.0 times or less, more preferably 3.0 times or more and 4.0 times or less.
Here, when the transverse draw ratio is less than 2.8, the transverse draw ratio is too low, and uneven portions such as unstretched portions are generated, resulting in uneven thickness and insufficient film orientation. There is a problem of lowering.

The biaxially stretched film stretched by the above method continues to hold the end with a tenter clip, is 200 ° C. or higher in a tenter oven, and 10 ° C. from the extrapolated melting start temperature of the aliphatic polyamide polymer (A) described above. The heat setting is usually performed at a high temperature or lower for a period of several seconds to several tens of minutes, preferably 1 second to 2 minutes, more preferably 3 to 15 seconds.
Here, if the heat setting temperature is 200 ° C. or more and the processing time is 1 second or more, the hot water shrinkage rate of MD can be suppressed to 3.0% or less, and the shrinkage is caused by printing, laminating and the like. It is possible to suppress the occurrence of troubles such as shifting the pitch. On the other hand, if the heat setting temperature is 10 ° C. or less higher than the extrapolated melting start temperature of the aliphatic polyamide polymer (A) and the treatment time is 2 minutes or less, the film is melted or crystallized during heat setting. Therefore, a film having good mechanical properties can be obtained.
The extrapolated melting start temperature described above is a straight line obtained by extending the low-temperature base line of the melting peak in the differential scanning calorimetry (DSC) described in JIS K 7121: 1987 to the high-temperature side. This is the temperature obtained from the intersection of the tangent lines drawn at the point where the gradient is maximum on the low temperature side curve.

  As an embodiment of the present invention, there is a laminate film in which the linear-cutting polyamide-based laminate film is a constituent component of the laminate. Examples of the laminate film include those in which a sealant film (layer) is disposed on at least one side of the linear cut polyamide-based laminate film. The sealant film may be any resin that can be heat-sealed, and generally includes a polyolefin resin, a polyester resin, and the like. Specifically, polypropylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, ionomer Resins, ethylene / α-olefin copolymers, amorphous polyesters and the like may be mentioned, but are not limited thereto. The thickness of the sealant film is generally preferably about 15 to 80 μm. If the sealant film is thin, the adhesive strength tends to be inferior, whereas if it is too thick, it tends to be unsuitable for packaging applications.

  Furthermore, there exists a bag body which consists of the said laminate film as other embodiment of this invention. This is a secondary processing of the above laminate film, and the bag is made by heat welding with the sealant layers inside. It is preferable to make a notch in the cut part of the seal part of the bag so that it can be easily torn. The form of the notch is not particularly limited as long as it is a generally adopted form. Examples of the contents of the bag include foods, pharmaceuticals, chemicals, and fragrances that do not want to be altered by oxygen.

  Hereinafter, the contents and effects of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. The evaluation and measurement methods for the film were performed by the following methods. Here, the flow direction from the extruder of the film is MD, and the width direction of the film, which is the orthogonal direction, is TD.

(1) Straight cut property From the both ends of the obtained film and the three points at the center, cut out two pieces each at 300 mm × TD into 180 mm into MD, and draw lines exactly parallel to MD at intervals of 30 mm. Next, a cut is made on this line using a feather blade to a point of 50 mm from the end, and a strip is formed to produce a test piece. Next, the test piece is placed on the flat frosted glass in such a way that the MD faces straight forward in front of the measurer. Here, in the case of right-handed pulling, the right hand holds the strip at the right end of the test piece, and the left hand holds the strip that is next to it. Pull the right hand with the strip part slowly and straightly toward you. This operation is performed five times in order from the right end. In the case of left pulling, the reverse operation is performed.
The width that is shifted from the line drawn on MD in advance from the beginning of tearing, that is, the absolute value of the amount of deviation from the straight line when drawing a straight line on MD and tearing 200 mm is L (mm). It was used as an index.
The above tests are conducted for each of the right hand pull and left hand pull, and the average value (rounded off to the first decimal place) is taken, and the following evaluation is performed for the largest of the six points at both ends and the center. Went.
L (mm) is 5.0 mm or less (○), and L (mm) is more than 5.0 mm (×)

(2) Hot water shrinkage rate From the both ends of the obtained film and the central three points, cut into 120 mm × TD at 120 mm in MD, and draw three reference lines of about 100 mm on MD of this sample. This sample is left in an atmosphere of 23 ° C. and 50% RH for 24 hours, and the reference line is measured. The measured length before heat treatment is F. This sample is immersed in hot water maintained at 95 ° C., heated for 5 minutes, and then taken out. Further, after being left in an atmosphere of 23 ° C. and 50% RH for 30 minutes, the reference line is measured, and the length after the heat treatment is defined as G.
The hot water shrinkage rate is calculated by the following formula, and the average value of the three (rounded off the second decimal place of the average value) is the hot water shrinkage rate of MD, and the maximum of the three points at both ends and the center. The following evaluation was performed on the product.
Hot water shrinkage = [(F−G) / F] × 100 (%)
MDs with hot water shrinkage of 3.0% or less (○), those with more than 3.0% (×)

(3) Thickness fluctuation rate (%)
Using a striking-point thickness meter, the thickness is measured at intervals of 20 mm in the width direction of the obtained film, the maximum value at that time is Tmax, the minimum value is Tmin, the average value obtained by summing all the measurement points and dividing by the number of measurement points Tave.
The thickness fluctuation rate was calculated by the following formula (rounded to the first decimal place), and the following evaluation was performed.
Thickness variation rate = [(Tmax−Tmin) / Tave] × 100 (%)
Thickness fluctuation rate of 10% or less (○), 10% or more (×)

(4) Oxygen permeability (fmol / (m ² · sec · Pa))
Using an “OXY-TRAN100 type oxygen permeability measuring device” manufactured by Modern Control Co., Ltd., measured at a temperature of 25 ° C. and 50% RH (relative humidity 50%) (n = 3), and the average value obtained The following evaluation was performed by rounding off the first decimal place.
Those with an oxygen permeability of 80 fmol / (m ² · sec · Pa) or less (○)
Those with oxygen permeability exceeding 80 fmol / (m ² · sec · Pa) (×)

Example 1
In order to obtain a film having a three-layer structure (a) / (b) / (a), nylon 6 “Mitsubishi Engineering Plastics Co., Ltd.” was used as the aliphatic polyamide polymer (A) constituting the layer (a). , Trade name Novamid 1022, extrapolation start temperature: 215 ° C. ”, MXD6“ Mitsubishi Gas Chemical Co., Ltd., trade name MX Nylon S6007 ”is used as the aromatic polyamide polymer (B), 65 masses of nylon 6 % And 35% by mass of MXD6 are mixed by dry blending, and this is put into a 65 mmφ single screw extruder (L / D = 28), and (b) 100% of the MXD6 constituting the layer is mixed. % In a separate 65 mmφ single screw extruder (L / D = 28), melted and kneaded separately at a set temperature of 260 ° C., and each of the mixed polyamides was almost halved with a distribution block. Split, laminated in a coextrusion T-die, extruded as a laminated film with a three-layer structure, closely cooled to a 30 ° C. cast roll, (a) / (b) / (a) ≈51 μm / 38 μm / 51 μm A stretched laminated film was obtained.
The obtained unstretched laminated film was stretched 2.7 times in the longitudinal direction by a roll-type stretching machine under the condition of 60 ° C., and then the end of the longitudinally stretched film was held with a tenter clip. The film was stretched 3.4 times in the transverse direction under the condition of 100 ° C., and then heat-fixed at 215 ° C. for 6 seconds. The heat-fixed film is trimmed at both end portions corresponding to the gripping portion of the clip, and the trimmed film is wound into a roll shape, and (a) / (b) / (a) ≈5.5 μm / A laminated biaxially stretched film having a total thickness of about 15 μm was obtained with a three-layer structure of 4 μm / 5.5 μm. The results of evaluation using the obtained film are shown in Table 1.

(Example 2)
A film was obtained in the same manner as in Example 1 except that the ratio of MXD6 in the layer (a) was 21% by mass, and the same evaluation was performed. The results are shown in Table 1.

(Example 3)
A film was obtained in the same manner as in Example 1 except that the ratio of MXD6 in the layer (a) was 45% by mass, and the same evaluation was performed. The results are shown in Table 1.

Example 4
A film was obtained in the same manner as in Example 1 except that the stretching ratio in the longitudinal direction was 2.4 times, and the same evaluation was performed. The results are shown in Table 1.

(Example 5)
A film was obtained in the same manner as in Example 1 except that the heat setting temperature after stretching was 200 ° C., and the same evaluation was performed. The results are shown in Table 1.

(Example 6)
A film was obtained in the same manner as in Example 1 except that the heat setting temperature after stretching was 225 ° C., and the same evaluation was performed. The results are shown in Table 1.

(Example 7)
A film was obtained in the same manner as in Example 1 except that the extrusion amount was changed so that the thickness of the (b) layer, which is the inner layer after stretching, was 2 μm, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 1)
A film was obtained in the same manner as in Example 1 except that the ratio of MXD6 in the layer (a) was 15% by mass, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 2)
A film was obtained in the same manner as in Example 1 except that the ratio of MXD6 in the layer (a) was 50% by mass, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 3)
A film was obtained in the same manner as in Example 1 except that the stretching ratio in the longitudinal direction was 2.3 times, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 4)
A film was obtained in the same manner as in Example 1 except that the stretching ratio in the longitudinal direction was changed to 3.0, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 5)
A film was obtained in the same manner as Example 1 except that the heat setting temperature after stretching was 190 ° C., and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 6)
In Example 1, the same method was used except that the heat setting temperature after stretching was 230 ° C., but the film was frequently broken in the tenter and could not be continuously formed. The results are shown in Table 1.

(Comparative Example 7)
A film was obtained in the same manner as in Example 1 except that the extrusion amount was changed so that the thickness of the (b) layer, which is the inner layer after stretching, was 1 μm, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 8)
A film was obtained in the same manner as in Example 1 except that the amount of extrusion was changed so that the thickness of the (b) layer as the inner layer after stretching was 8 μm, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 9)
In order to obtain a film having a three-layer structure (a) / (b) / (a), nylon 6 “Mitsubishi Engineering Plastics Co., Ltd.” was used as the aliphatic polyamide polymer (A) constituting the layer (a). , Trade name Novamid 1022, extrapolation start temperature: 215 ° C. ”, MXD6“ Mitsubishi Gas Chemical Co., Ltd., trade name MX Nylon S6007 ”is used as the aromatic polyamide polymer (B), 65 masses of nylon 6 % And 35% by mass of MXD6 are mixed by dry blending, and this is put into a 65 mmφ single screw extruder (L / D = 28), and (b) 100% of the MXD6 constituting the layer is mixed. % In a separate 65 mmφ single screw extruder (L / D = 28), melted and kneaded separately at a set temperature of 260 ° C., and each of the mixed polyamides was almost halved with a distribution block. By splitting, laminating in a co-extrusion round die, extruding as a laminated film having a three-layer structure, and quenching with water, (a) / (b) / (a) ≈55 μm / 40 μm / 55 μm A stretched laminated film was obtained.
After the obtained unstretched laminated film is inserted between a pair of nip rolls, it is heated with a heater while air is pressed into it, and is blown into a bubble by blowing air from the air ring to the stretching start point. By pulling with a pair of nip rolls, simultaneous biaxial stretching in the MD direction and the TD direction was performed by the tubular method. The magnification at the time of stretching was 3.0 times in the MD direction and 3.3 times in the TD direction.
Next, the end of the stretched film was held with a tenter clip, and heat fixed at 215 ° C. for 6 seconds in a tenter oven. The heat-fixed film is trimmed at both end portions corresponding to the gripping portion of the clip, and the trimmed film is wound into a roll shape, and (a) / (b) / (a) ≈5.5 μm / A laminated biaxially stretched film with a total thickness of about 15 μm was obtained with a three-layer structure of 4 μm / 5.5 μm, and the same evaluation was performed. The results are shown in Table 1.

From Table 1, it can be seen that Examples 1 to 7 which are the films of the present invention show good results for all the evaluation items.
On the other hand, it can be seen that Comparative Example 1, Comparative Example 2, and Comparative Example 4 having a high longitudinal draw ratio are inferior in linear cut property, in which the content of MXD6 is outside the scope of the present invention. Comparative Example 3 having a low longitudinal stretching ratio was a film in which stretching unevenness occurred and the thickness variation rate was large. In Comparative Example 5 where the heat setting temperature is low, the hot water shrinkage rate of MD is large, so that there is a problem that troubles such as shrinkage due to shrinkage in printing, laminating, and the like are likely to occur. In Comparative Example 6 having a high heat setting temperature, breakage occurred frequently in the tenter, and the film could not be continuously formed. It can be seen that Comparative Example 7 in which the (b) layer, which is a gas barrier layer, is thin has poor oxygen permeability, while Comparative Example 8 in which the (b) layer is thick has poor linear cutting properties. Comparative Example 9 formed by the tubular simultaneous biaxial stretching method has a large rate of variation in thickness, causes wrinkles and tarmi, causes misregistration in printing, causes film paths to meander, and shifts in printing pitch. Therefore, there is a problem in that troubles easily occur during printing and laminating.

Claims (3)

(A) layer containing 55 to 79% by mass of nylon 6 (A) and 21 to 45% by mass of polymetaxylylene adipamide (B ), 0 to 10% by mass of nylon 6 (A) and polymetaxyl silylene adipamide (B) is seen from 90 to 100 wt% free, and a thickness of the laminated film having at least one layer respectively and a 2-7 [mu] m (b) layer, the unstretched film extruded from a flat die MD After stretching by a tenter-type sequential biaxial stretching method at a stretching ratio of 2.4 times or more and less than 2.8 times to TD and 2.8 times or more of TD, extrapolation melting of the nylon 6 (A) is performed at 200 ° C. or more. Straight cut property (absolute value of deviation from a straight line when a straight line is drawn on the MD and 200 mm is obtained by heat setting at a temperature not higher than 10 ° C higher than the starting temperature (measured in accordance with JIS K 7121) ) Is 5.0mm Below, the hot water shrinkage rate in the film flow direction (MD) at 95 ° C. × 5 minutes is 3.0% or less, the thickness variation rate in the width direction (TD) of the film is 10% or less of the average thickness, and 25 A linear-cutting polyamide-based laminated film having an oxygen permeability of 80 fmol / (m ² · sec · Pa) or less under the condition of ° C x 50% RH. The laminate film according to claim 1, wherein the linear-cutting polyamide-based film is a constituent of a laminate. A bag comprising the laminate film according to claim 2 .