Stretched films, multilayer films, and packaging materials

Abstract

Provided are a stretched film including polyamide resins and having excellent transparency, a multilayered film, and a packaging material. The stretched film comprises a polyamide resin (a1) and a polyamide resin (a2), wherein the polyamide resin (a1) comprises diamine-derived constituent units and dicarboxylic-acid-derived constituent units, 70 mol% or more of the diamine-derived constituent units being derived from xylylene diamine and 70 mol% or more of the dicarboxylic-acid-derived constituent units being derived from sebacic acid, the polyamide resin (a2) is one in which 35 mol% or more of all the constituent units are constituent units including a linear alkylene group and derived from a monomer having 5-7 carbon atoms, and the mass ratio between the polyamide resin (a1) and the polyamide resin (a2) is 5 / 95 to 30 / 70.

Description

[Technical Field]

[0001] This invention relates to stretched films, multilayer films, and packaging materials. [Background technology]

[0002] Traditionally, films made from polyamide resins containing xylylenediamine-derived structural units have been known for their excellent oxygen gas barrier properties, heat resistance, and high film strength. Furthermore, unstretched and stretched films made from aliphatic polyamides, such as polyamide 6 and polyamide 66, exhibit excellent impact resistance and flexural fatigue resistance, and are widely used as various packaging materials. On the other hand, Patent Document 1 states that films made of polyamide resin containing xylylenediamine-derived structural units have a problem in that they are prone to pinhole formation. It also states that when pinholes occur in product packaging materials, it can lead to contamination due to leakage of contents, spoilage of contents, and mold growth, resulting in a decrease in product value.

[0003] Furthermore, Patent Document 1 discloses a biaxially oriented polyamide film characterized by having a resin layer (layer B) mainly composed of an aliphatic polyamide resin, laminated on at least one side of a resin layer (layer A) mainly composed of a metaxylylene group-containing polyamide polymer, in which metaxylylenediamine or a mixed xylylenediamine consisting of metaxylylenediamine and paraxylylenediamine is the main diamine component and an α,ω-aliphatic dicarboxylic acid component having 6 to 12 carbon atoms is the main dicarboxylic acid component, and satisfying the following requirements (1) to (3). (1) The resin layer (Layer A) mainly composed of the metaxylylene group-containing polyamide polymer contains 70% by mass or more of the metaxylylene group-containing polyamide polymer. (2) The resin layer (layer B) mainly composed of the aliphatic polyamide resin contains at least 99 to 60% by mass of polyamide 6 and 1 to 34% by mass of polyamide polymerized from biomass-derived raw materials. (3) The thickness of layer A is 10% or more and 30% or less of the combined thickness of layers A and B.

[0004] Furthermore, Patent Document 2 describes a polyamide resin composition obtained by blending a specific amount of modified polyolefins relative to the aromatic polyamide in a mixture of a specific aromatic polyamide and an aliphatic polyamide, and a polyamide resin stretched film obtained by melt extrusion of this polyamide resin composition to make a substantially unoriented unstretched sheet, then stretching it at least uniaxially and heat-setting it. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021 / 070500 [Patent Document 2] Japanese Patent Application Publication No. 5-051525 [Overview of the project] [Problems that the invention aims to solve]

[0006] As mentioned above, stretched films composed of polyamide 6 have excellent impact resistance and flexural fatigue resistance, but they have problems such as high shrinkage rate and high water absorption rate. Therefore, in order to improve various properties, it is conceivable to improve the performance of stretched films by blending other polyamide resins with polyamide 6, etc. However, it has been found that when a resin layer mainly composed of aliphatic polyamide resin, such as the one described in Patent Document 1 above, i.e., a resin layer in which polyamide 6 is blended with polyamide 11 or polyamide 1010, etc., is used, the transparency of the resulting stretched film is inferior. The present invention aims to solve the aforementioned problems and to provide stretched films containing polyamide resin, stretched films, multilayer films, and packaging materials that exhibit excellent transparency. [Means for solving the problem]

[0007] Under the above challenges, the inventors investigated the possibility of blending a polyamide resin containing xylylenediamine-derived components with a highly flexible polyamide resin, specifically a polyamide resin in which 35 mol% or more of the total constituent units have linear alkylene groups. Blending a polyamide resin containing xylylenediamine-derived components with a polyamide resin in which 35 mol% or more of the total constituent units have linear alkylene groups is expected to impart properties such as reduced water absorption and reduced shrinkage of stretched films. However, it was found that blending polyamide 6 with metaxylyleneadipamide (MXD6), a representative example of a polyamide resin containing xylylenediamine-derived components, resulted in reduced transparency. Under these circumstances, the inventors discovered that a stretched film with excellent transparency can be obtained by using a polyamide resin containing xylylenediamine-derived structural units with relatively long aliphatic chains of the dicarboxylic acid component, and by using a highly flexible polyamide resin with relatively short aliphatic chains, thus completing the present invention. Specifically, the above problem was solved by the following means. <1> A stretched film comprising a polyamide resin (a1) and a polyamide resin (a2), wherein the polyamide resin (a1) comprises diamine-derived structural units and dicarboxylic acid-derived structural units, with 70 mol% or more of the diamine-derived structural units being derived from xylylenediamine and 70 mol% or more of the dicarboxylic acid-derived structural units being derived from sebacic acid; the polyamide resin (a2) comprises 35 mol% or more of the total structural units being monomers having linear alkylene groups and having 5 to 7 carbon atoms, and the mass ratio of the polyamide resin (a1) to the polyamide resin (a2) is 5 / 95 to 30 / 70. <2> The constituent unit having the linear alkylene group in the polyamide resin (a2) is -[NH(CH2) n1 CO]-,-[NH(CH2)] n2 NH]- and -[CO(CH2) n3At least one of the following is selected from CO: n1 is an integer between 4 and 6, n2 is an integer between 5 and 7, and n3 is an integer between 3 and 5. <1> The stretched film described above. <3> The polyamide resin (a1) contains a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, wherein 70 mol% or more of the diamine-derived structural unit is derived from metaxylylenediamine. <1> or <2> The stretched film described above. <4> The polyamide resin (a2) contains polyamide 6. <1> ~ <3> A stretched film as described in any one of the following. <5> The polyamide resin (a2) contains polyamide 6 / 66. <1> ~ <4> A stretched film as described in any one of the following. <6> The mass ratio of the polyamide resin (a1) to the polyamide resin (a2) is 5 / 95 to 19 / 81. <1> ~ <5> A stretched film as described in any one of the following. <7> It is a uniaxially oriented film. <1> ~ <6> A stretched film as described in any one of the following. <8> It is a biaxially oriented film. <1> ~ <6> A stretched film as described in any one of the following. <9> It is a tear-resistant film. <7> or <8> The stretched film described above. <10> <7> ~ <9> A multilayer film having a stretched film described in any one of the above and other layers. <11> The other layer includes a sealant layer. <10> The multilayer film described above. <12> The other layer includes a barrier layer, and the sealant layer, the stretched film, and the barrier layer are laminated in that order, and the stretched film is a biaxially oriented film. <11> The multilayer film described above. <13>The other layer includes a barrier layer, the barrier layer includes a structural unit derived from diamine and a structural unit derived from dicarboxylic acid, at least 70 mol% of the structural unit derived from diamine is derived from xylylenediamine, and at least 70 mol% of the structural unit derived from the dicarboxylic acid is derived from adipic acid, and the oxygen barrier resin is included, and the stretched film includes polyamide 6 and a structural unit derived from diamine and a structural unit derived from dicarboxylic acid, and at least 70 mol% of the structural unit derived from diamine is derived from metaxylylenediamine, and the multilayer film according to <10>, wherein the barrier layer and the stretched film are in contact with each other. <14>The multilayer film according to <13>, wherein the barrier layer and the stretched film are stretched at the same stretching ratio. <15>A packaging material including the stretched film according to any one of <1> to <9> or the multilayer film according to any one of <10> to <14>.

Effects of the Invention

[0008] According to the present invention, it has become possible to provide a stretched film containing a polyamide resin, which has excellent transparency, a multilayer film, and a packaging material.

Brief Description of the Drawings

[0009] [Figure 1] It is a cross-sectional view showing an example of an embodiment of the multilayer film of the present invention.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an exemplification for explaining the present invention, and the present invention is not limited to only the present embodiment. In the present specification, "~" is used in the meaning of including the numerical values described before and after it as lower limit values and upper limit values. In the present specification, various physical property values and characteristic values are those at 23 °C unless otherwise specified. In this specification, "film" refers to a molded body that is thin in thickness relative to its length and width, and is generally flat, and includes "sheets." Furthermore, "film" in this specification may be single-layer or multi-layer. If the standards or measurement methods described herein differ from year to year, unless otherwise specified, the standards as of January 1, 2021 shall apply.

[0011] The stretched film of this embodiment is a stretched film comprising a polyamide resin (a1) and a polyamide resin (a2), wherein the polyamide resin (a1) comprises diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol% or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural units are derived from sebacic acid; the polyamide resin (a2) comprises 35 mol% or more of the total structural units derived from monomers having linear alkylene groups and having 5 to 7 carbon atoms, and the mass ratio of the polyamide resin (a1) to the polyamide resin (a2) is 5 / 95 to 30 / 70. By using this configuration, a stretched film with excellent transparency can be obtained. Polyamide resin (a2) is a polyamide resin in which 35 mol% or more of the total constituent units have linear alkylene groups, and is relatively flexible. For example, polyamide 6 is a typical example. However, as described in Patent Document 2, when MXD6, a typical example of a polyamide resin containing constituent units derived from xylylenediamine, was blended with polyamide 6, the transparency was reduced. It was speculated that this was because the difference in refractive index between the two was large, causing diffuse reflection of light. Furthermore, when polyamide 6 was blended with polyamide 11 or polyamide 1010, as described in Patent Document 1, the transparency was also reduced. It was speculated that this was because the difference in SP values ​​between polyamide 6 and polyamide 11 or polyamide 1010 was large, making it difficult for polyamide 11 or polyamide 1010 to disperse in polyamide 6. In this embodiment, a polyamide resin (a2) in which 35 mol% or more of the total constituent units have linear alkylene groups is blended with a polyamide resin (a1) in a predetermined ratio, in which 70 mol% or more of the diamine-derived constituent units are derived from xylylenediamine and 70 mol% or more of the dicarboxylic acid-derived constituent units are derived from sebacic acid. Furthermore, the constituent units having linear alkylene groups in the polyamide resin (a2) are derived from monomers with 5 to 7 carbon atoms. By creating a configuration in which there is a difference in the length of the aliphatic chains contained in the polyamide resin (a1) and the fatty chains contained in the polyamide resin (a2), it is possible to finely disperse the polyamide resin (a1) in the polyamide resin (a2), and it is presumed that a stretched film with excellent transparency and reduced diffuse reflection of light is obtained.

[0012] <Polyamide resin (a1)> The stretched film of this embodiment contains a polyamide resin (a1). By including the polyamide resin (a1), various functions can be imparted to the stretched film, such as low water absorption, easy tearing, and reduced shrinkage rate. The polyamide resin (a1) contains diamine-derived structural units and dicarboxylic acid-derived structural units, with 70 mol% or more of the diamine-derived structural units being derived from xylylenediamine and 70 mol% or more of the dicarboxylic acid-derived structural units being derived from sebacic acid.

[0013] The polyamide resin (a1) contains 70 mol% or more of diamine-derived structural units, preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, of which 70 mol% or more, of diamine-derived structural units are derived from xylylenediamine. The upper limit is 100 mol%. Preferably, of the above xylylenediamine, 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, are meta-xylylenediamine and / or para-xylylenediamine. The metaxylylenediamine and / or paraxylylenediamine are preferably mixed in a molar ratio of 50-100:50-0, more preferably 60-100:40-0, even more preferably 65-100:35-0, even more preferably 70-100:30-0, and may also be 80-100:20-0, 90-100:10-0, or 95-100:5-0. Increasing the proportion of para-xylylenediamine increases the amidation reaction rate of polyamide resin (a1), which has advantages in resin manufacturing, such as shortening the time to reach the desired relative viscosity. However, beyond the above ratio, the melting point rises, and the difference in melting points with polyamide resin (a2) becomes large, which tends to worsen moldability. Keeping the mixing ratio of meta-xylylenediamine and para-xylylenediamine within the above range results in good manufacturing conditions for polyamide resin (a1) itself and for stretched films containing polyamide resin (a1) and polyamide resin (a2).

[0014] Examples of diamines other than xylylenediamine include aromatic diamines such as paraphenylenediamine, and aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, and nonamethylenediamine. These other diamines may be present individually or in combination of two or more.

[0015] In the polyamide resin (a1), 70 mol% or more of the constituent units derived from dicarboxylic acid, preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, are derived from sebacic acid. The upper limit is 100 mol%. Using sebacic acid offers the advantage of creating a bio-based resin derived from castor oil, making it a carbon-neutral material that contributes to a sustainable society.

[0016] The dicarboxylic acid-derived constituent units may include other dicarboxylic acids besides sebacic acid. Examples of other dicarboxylic acids include α,ω-linear aliphatic dicarboxylic acids other than sebacic acid, such as malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, and dodecanedioic acid; phthalic acid compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid; and naphthalenedicarboxylic acid compounds such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. One or more of these can be used in combination.

[0017] In this embodiment, the polyamide resin (a1) is particularly preferably composed of diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol% or more of the diamine-derived structural units are derived from metaxylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural units are derived from sebacic acid. In this embodiment, the polyamide resin (a1) may be partially or entirely synthesized from biomass. For example, sebacic acid, a biomass monomer derived from castor oil, can be used.

[0018] Here, the constituent units of the polyamide resin include not only diamine-derived constituent units and dicarboxylic acid-derived constituent units, but also terminal groups and other constituent units without departing from the spirit of the present invention. Examples of other constituent units include lactams such as ε-caprolactam, valerolactam, laurolactam, and undecalactam, and aminocarboxylic acids such as 11-aminoundecanoic acid and 12-aminododecanoic acid. Furthermore, in the polyamide resin used in this embodiment, typically 95% or more by mass, preferably 98% or more by mass, and more preferably 99% or more by mass of the constituent units excluding terminal groups are composed of dicarboxylic acid-derived constituent units and diamine-derived constituent units.

[0019] The relative viscosity of the polyamide resin (a1) preferably has a lower limit of 2.1 or higher, more preferably 2.3 or higher, and even more preferably 2.5 or higher. On the other hand, the upper limit of the relative viscosity of the polyamide resin (a1) preferably has a lower limit of 4.0 or lower, more preferably 3.9 or lower, and even more preferably 3.8 or lower. The relative viscosity of polyamide resin (a1) is measured under the conditions of JIS K 69020-2.

[0020] <Polyamide resin (a2)> The stretched film of this embodiment contains a polyamide resin (a2). Polyamide resin (a2) is typically the main component of stretched films. By using such a polyamide resin, stretched films with excellent flexibility tend to be obtained. Furthermore, stretched films with excellent impact resistance and pinhole resistance tend to be obtained. Polyamide resin (a2) is a material in which at least 35 mol% of all constituent units are constituent units having a linear alkylene group and are derived from monomers having 5 to 7 carbon atoms. Examples of the monomers include diamines, dicarboxylic acids, lactams, and aminocarboxylic acids.

[0021] In the polyamide resin (a2), 35 mol% or more, preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, and especially most preferably 95 mol% or more of the total constituent units are derived from constituent units having the predetermined linear alkylene group. The upper limit is when all constituent units, excluding terminal groups, are the predetermined linear alkylene group. By having such a high proportion of linear alkylene groups, a stretched film with excellent flexibility can be obtained.

[0022] The linear alkylene group constituent units of the polyamide resin (a2) are derived from monomers having 5 to 7 carbon atoms, and preferably from monomers having 6 carbon atoms. This configuration prevents polyamide resin (a1) from becoming miscible within polyamide resin (a2) and facilitates dispersion. As a result, it is presumed that the stretched film can maintain high transparency. Furthermore, since polyamide resin (a2) and polyamide resin (a1) do not become miscible and are phase-separated as matrix and domains, a stretched film with excellent tear resistance can be obtained.

[0023] More specifically, the constituent unit having a linear alkylene group in this embodiment is -[NH(CH2) n1 CO]-,-[NH(CH2)] n2 NH]- and -[CO(CH2) n3 It is preferable that it be at least one selected from CO]-, where n1 is an integer between 4 and 6, preferably 5; n2 is an integer between 5 and 7, preferably 6; and n3 is an integer between 3 and 5, preferably 4.

[0024] The polyamide resin (a2) is preferably an aliphatic polyamide resin. An aliphatic polyamide resin is defined as a resin in which 50 mol% or more of the total constituent units, excluding the end groups, are derived from aliphatic monomers. In this embodiment, of the total constituent units of the polyamide resin (a2), excluding the end groups, it is preferable that 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more are derived from aliphatic monomers.

[0025] Examples of polyamide resin (a2) include polyamide 6, polyamide 66, polyamide 46, polyamide 6 / 66 (a copolymer consisting of polyamide 6 and polyamide 66 components), polyamide 610, polyamide 612, polyamide 6I, polyamide 6T, polyamide 6I / 6T, etc. Polyamide 6, polyamide 66, polyamide 46, and polyamide 6 / 66 are preferred, polyamide 6, polyamide 66, and polyamide 6 / 66 are more preferred, polyamide 6 and polyamide 6 / 66 are even more preferred, and polyamide 6 is even more preferred. Furthermore, although polyamide 6 is a ring-opening polymer of caprolactam, it may also contain constituent units derived from other monomers within a range that does not depart from the spirit of the present invention (for example, 5% by mass or less of the total, more specifically 3% by mass or less, and especially 1% by mass or less). The same applies to other polyamide resins such as polyamide 66.

[0026] <Relationship between polyamide resin (a1) and polyamide resin (a2)> In this embodiment, the stretched film has a mass ratio of polyamide resin (a1) to polyamide resin (a2) of 5 / 95 to 30 / 70, preferably 5 / 95 to 19 / 81. By setting the polyamide resin (a1) to the lower limit of 5 or higher, the shrinkage rate of the stretched film tends to be further reduced. Furthermore, by setting the polyamide resin (a1) to the upper limit of 30 or lower, it tends to be possible to effectively suppress the decrease in oxygen barrier properties while maintaining a certain degree of flexibility of the polyamide resin (a2). The mass ratio of the polyamide resin (a1) is preferably 6 or more, more preferably 8 or more, and even more preferably 10 or more, when the total of polyamide resin (a1) and polyamide resin (a2) is set to 100. Furthermore, the mass ratio of the polyamide resin (a1) is preferably 29 or less, more preferably 27 or less, even more preferably 25 or less, even more preferably 23 or less, even more preferably 20 or less, even more preferably 19 or less, and especially even more preferably 18 or less, when the total of polyamide resin (a1) and polyamide resin (a2) is set to 100.

[0027] The total content of polyamide resin (a1) and polyamide resin (a2) in the stretched film of this embodiment is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 93% by mass or more, even more preferably 95% by mass or more, even more preferably 97% by mass or more, even more preferably 99% by mass or more, even more preferably 99.9% by mass or more, and even more preferably more than 99.9% by mass. The upper limit is 100% by mass. The stretched film of this embodiment may contain only one type of polyamide resin (a1) and one type of polyamide resin (a2), or two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0028] <Other ingredients> The stretched film of this embodiment may contain, in addition to polyamide resin (a1) and polyamide resin (a2), another polyamide resin (a3). Examples of the other polyamide resin include semi-aromatic polyamide resins (excluding those corresponding to polyamide resin (a1) or polyamide resin (a2)), and xylylenediamine-based polyamide resins other than polyamide resin (a1) are preferred. Examples of xylylenediamine-based polyamide resins other than polyamide resin (a1) include polyamide resins containing diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol% or more of the diamine-derived structural units are derived from xylylenediamine (preferably meta-xylylenediamine), and 70 mol% or more of the dicarboxylic acid-derived structural units are derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms (preferably 6 carbon atoms). Furthermore, xylylenediamine-based polyamide resins in which a portion of the dicarboxylic acid component of the polyamide resin (for example, 1 to 10 mol% of the dicarboxylic acid component) is isophthalic acid are also preferred. Other examples of polyamide resins (a3) ​​include polyamide 11, polyamide 12, polyamide 9T, and polyamide 10T. If the stretched film of this embodiment contains another polyamide resin (a3), its content is preferably 10% by mass or less of the stretched film, more preferably 5% by mass or less, and may be 1% by mass or less. The stretched film of this embodiment may contain only one type of polyamide resin (a3), or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0029] Furthermore, the stretched film of this embodiment may contain plasticizers, elastomers, polyolefins, antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, inorganic fillers, antistatic agents, antiblocking agents, flame retardants, and the like. The content of these components is preferably 10% by mass or less of the stretched film. One embodiment of this model is a stretched film that is substantially free of elastomers. "Substantially free of elastomers" means that the elastomer content in the stretched film is, for example, less than 1% by mass, preferably less than 0.5% by mass. By substantially free of elastomers, the effect of transparency is more effectively achieved. One embodiment of this model is a stretched film that is substantially free of polyolefins. "Substantially free of polyolefins" means that the polyolefin content in the stretched film is, for example, less than 1% by mass, preferably less than 0.5% by mass, and more preferably less than 0.3% by mass. By substantially free of polyolefins, the effect of transparency is more effectively achieved.

[0030] <Stretching> The stretched film of this embodiment is obtained by stretching an unstretched polyamide resin film. The stretched film of this embodiment may be a uniaxially stretched film or a biaxially stretched film. Furthermore, when uniaxial stretching is performed, the stretch ratio is preferably 1.1 times or more, more preferably 2.0 times or more, and even more preferably 3.0 times or more. There is no upper limit, but it is preferably 20.0 times or less. Furthermore, when biaxial stretching is performed, the stretch ratio in each direction (TD, MD) is preferably 1.1 times or more, more preferably 2.0 times or more, and may be 3.0 times or more. There is no particular upper limit, but it is preferably 20.0 times or less. The overall stretch ratio is preferably 1.5 times or more, and preferably 30.0 times or less.

[0031] The stretched film of this embodiment is preferably a tearable film. If it is a tearable film, it may be either a biaxially oriented or uniaxially oriented film. However, uniaxial stretching results in the polyamide resin (a1) existing in elongated forms within the film, making it possible to obtain a film with superior tearability. It can also be used as a constituent layer in a multilayer film. Furthermore, in this embodiment, the polyamide resin (a1) can be sufficiently dispersed in the polyamide resin (a2) without complete miscibility, making it a suitable choice for use as an easily tearable film.

[0032] Furthermore, if the stretched film of this embodiment is a biaxially oriented film, it may be used as a single-layer film, but it is preferable to use it as a constituent layer of a multilayer film. It is presumed that a good sea-island structure is formed by biaxial stretching of polyamide resin (a1) and polyamide resin (a2). That is, islands of polyamide resin (a1) are formed in a sea of ​​polyamide resin (a2). As a result, a stretched film with low water absorption, low shrinkage, and excellent properties, as well as a multilayer film, can be obtained, which are the characteristics of polyamide resin (a1).

[0033] The unstretched polyamide film may be stretched after forming a multilayer film with other layers, or the unstretched polyamide film may be stretched and then laminated with other layers. When stretching an unstretched polyamide film, the stretching method can be described in paragraphs 0049-0053 of International Publication No. 2017 / 010390, which is incorporated herein by reference.

[0034] The thickness of the stretched film (single-layer film) in this embodiment is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and preferably 200 μm or less, and even more preferably 100 μm or less.

[0035] The stretched film of this embodiment preferably has a haze of less than 2.0%, more preferably less than 1.3%, and even more preferably less than 1.0%. Ideally, the lower limit would be 0%, but 0.01% or more is practical.

[0036] The stretched film of this embodiment preferably has a shrinkage rate of less than 10.0%. Ideally, the lower limit should be 0%, but 0.01% or more is practical.

[0037] The stretched film of this embodiment preferably has a water absorption rate of less than 2.5%, and more preferably less than 1.8%. Ideally, the lower limit would be 0%, but 0.01% or more is practical.

[0038] The stretched film of this embodiment preferably has an oxygen transmission coefficient of less than 1.0 cc·mm / m 2 ·atm·day, and more preferably less than 0.52 cc·mm / m 2 ·atm·day. As the lower limit, 0 cc·mm / m 2 ·atm·day is ideal, but 0.01 cc·mm / m 2 ·atm·day or more is practical.

[0039] The stretched film (preferably a uniaxially stretched film) of this embodiment preferably has 10 or fewer pinholes per 100 cm of the film after 3000 foldings, more preferably 5 or fewer, and even more preferably 1 or fewer. The lower limit of the number of the pinholes is preferably 0. 2 The haze, shrinkage rate, water absorption rate, oxygen transmission coefficient, and number of pinholes are measured according to the description of the examples described later.

[0040] <Multilayer film> The multilayer film of this embodiment will be described. The multilayer film of this embodiment has a uniaxially stretched film or a biaxially stretched film and other layers. Examples of the other layers include a polyolefin layer, an adhesive layer, a sealant layer, an oxygen barrier layer (barrier layer), an oxygen absorption layer, an oxygen permeation layer, a metal vapor deposition layer, a design layer, and the like. In this embodiment, it is preferable that the other layer includes a sealant layer. Also, in this embodiment, it is preferable that the other layer includes a barrier layer. ​In this embodiment, the other layers include a sealant layer and a barrier layer, and the layers are laminated in the order of sealant layer, stretched film of this embodiment, and barrier layer, with the stretched film preferably being a biaxially oriented film. The sealant layer and the stretched film, and the stretched film and the barrier layer, may be in contact with each other or separated by other layers. If separated by other layers, an adhesive layer is preferred. Figure 1 shows an example of a cross-sectional view of the multilayer film of this embodiment, where 1 is the sealant layer, 2 is the stretched film of this embodiment, and 3 is the barrier layer. In one example of this embodiment, the sealant layer and the stretched film, and the stretched film and the barrier layer, are in contact with each other. Another example of this embodiment is that the sealant layer and the stretched film are in contact via an adhesive layer, and the stretched film and the barrier layer are in contact with each other.

[0041] The thickness of the multilayer film is, for example, 50 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less.

[0042] The multilayer film of this embodiment may have only one other layer, or it may have two or more other layers. The number of other layers is preferably one or more, more preferably two or more, may be three or more, and also preferably 10 or fewer, more preferably 8 or fewer, and may be 5 or fewer.

[0043] The sealant layer preferably contains a polyolefin. The polyolefin may be either a homopolymer or copolymer of α-olefins. Specifically, examples of the polyolefin include polyethylene, homopolypropylene, propylene-ethylene random copolymer, and propylene-ethylene block copolymer. Furthermore, a portion of the polyolefin may be an acid-modified polyolefin. By using an acid-modified polyolefin, adhesion to stretched films and the like can be further improved. The polyolefin may also be a low-density polyolefin. Moreover, the polyolefin may be a biopolyolefin. Examples of biopolyolefins include bio-low-density polyethylene and bio-linear low-density polyethylene.

[0044] The sealant layer preferably contains 80% by mass or more of polyolefin, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The sealant layer may contain one or more types of polyolefins, and if there are two or more types, it is preferable that the total amount is within the above range. Furthermore, the sealant layer may contain other components besides polyolefin, as long as it does not depart from the spirit of the present invention. Furthermore, as a sealant layer, reference can be made to paragraph 0045 of International Publication No. 2015 / 083558, which is incorporated herein by reference.

[0045] If the multilayer film of this embodiment has a sealant layer, its thickness is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and preferably 200 μm or less, and even more preferably 100 μm or less.

[0046] The barrier layer may be a layer mainly composed of a barrier resin or a metal foil such as aluminum foil, and it is preferable that the barrier layer mainly composed of a barrier resin. Specifically, the barrier layer is a layer in which, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more is a barrier resin. The upper limit may be 100% by mass. As a barrier resin, it has an oxygen permeability of 100 cc / m³. 2 This refers to resins with an oxygen barrier capacity of less than or equal to 10m·day. Examples of oxygen barrier resins include polyamides (such as MXD6), ethylene-vinyl alcohol copolymers, and vinylidene chloride.

[0047] The polyamide resin used as an oxygen barrier resin preferably contains diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol% or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural units are derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms, making the oxygen barrier resin X.

[0048] The oxygen barrier resin X contains diamine-derived constituent units, preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, of which 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, of which meta-xylylenediamine and / or para-xylylenediamine is preferred, and more preferably meta-xylylenediamine.

[0049] Examples of diamines other than xylylenediamine include aromatic diamines such as paraphenylenediamine, and aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, and nonamethylenediamine. These other diamines may be present individually or in combination of two or more.

[0050] The oxygen barrier resin X contains dicarboxylic acid-derived constituent units, preferably 75 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, all of which are derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms. The upper limit is 100 mol%.

[0051] Examples of α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms include succinic acid, glutaric acid, adipic acid, and suberic acid, with adipic acid being preferred. There may be one or more α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms.

[0052] The dicarboxylic acid-derived constituent units may include other dicarboxylic acids other than α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms. Examples of other dicarboxylic acids include α,ω-linear aliphatic dicarboxylic acids having 9 to 12 carbon atoms such as sebacic acid, phthalate compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and naphthalenedicarboxylic acid compounds such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, and one or more of these can be used in combination. In this embodiment, when the oxygen barrier resin X contains dicarboxylic acids other than α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms, sebacic acid is preferred. The proportion of sebacic acid is preferably 1 to 30 mol%, and more preferably 5 to 25 mol%, of the total dicarboxylic acid units constituting the oxygen barrier resin X.

[0053] In this embodiment, the oxygen barrier resin X particularly contains diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol% or more of the diamine-derived structural units are derived from metaxylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural units are derived from adipic acid. Furthermore, preferably 1 to 30 mol%, more preferably 5 to 25 mol%, of the dicarboxylic acid component may be sebacic acid. In addition to the oxygen barrier resin X, the above-mentioned polyamide resin (a1) may also be incorporated. In this case, the proportion of polyamide resin (a1) in the barrier layer is preferably 1 to 30% by mass, and more preferably 5 to 25% by mass.

[0054] Furthermore, the barrier layer may contain plasticizers, elastomers, antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, antistatic agents, flame retardants, etc. The content of these components is preferably 10% by mass or less of the barrier layer. If the multilayer film of this embodiment has a barrier layer, its thickness is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and preferably 200 μm or less, and even more preferably 100 μm or less.

[0055] Details of the adhesive layer can be found in paragraph 0015 of Japanese Patent Publication No. 2012-035504 and paragraph 0043 of International Publication No. 2015 / 083558, which are incorporated herein by reference. For the oxygen permeable layer, reference can be made to paragraphs 0011-0014 of International Publication No. 2015 / 083558, which are incorporated herein by reference. An example of a metal vapor-deposited layer is an aluminum vapor-deposited layer. Details of the metal vapor-deposited layer can be found in International Publication No. 2018 / 083962, which is incorporated herein by reference.

[0056] As an example of the multilayer film of this embodiment, a multilayer film is exemplified in which the other layers include a barrier layer, the barrier layer includes diamine-derived structural units and dicarboxylic acid-derived structural units, 70 mol% or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural units are derived from adipic acid-derived oxygen barrier resin, the stretched film of this embodiment includes polyamide 6, diamine-derived structural units and dicarboxylic acid-derived structural units, and 70 mol% or more of the diamine-derived structural units are derived from meta-xylylenediamine-derived polyamide resin, and the barrier layer and the stretched film are in contact. Such a multilayer film is preferable because of the high adhesion between the barrier layer and the stretched film. Furthermore, it is preferable that the barrier layer and the stretched film are stretched at the same stretching ratio. The same stretching ratio can be achieved, for example, by stretching the barrier layer and the stretched film of this embodiment simultaneously.

[0057] Multilayer films can be manufactured according to known methods. For example, methods such as melting the polymers constituting each layer using separate extruders and manufacturing them by co-extrusion from a single die, melt-extruding the polymers constituting each layer separately into films and then laminating them by a lamination method, and methods combining these can be employed. Furthermore, in this embodiment, the film may be stretched after being made into a multilayer film. In this case, the stretching method can be a flat sequential biaxial stretching method, a flat simultaneous biaxial stretching method, a tubular method, etc., and the flat sequential biaxial stretching method is preferred. More specifically, raw resin is melt-extruded from two extruders using a co-extrusion method, merged in a feed block, extruded in a film-like manner from a die, and supplied to a cooling roll for cooling to obtain a multilayer unstretched film. At this time, the resin melting temperature in each extruder can be arbitrarily selected within the range of the melting point of the resin constituting each layer + 10°C to 50°C. The obtained unstretched multilayer film is guided to a roll-type longitudinal stretcher and stretched longitudinally using the speed difference between the rolls, then introduced to a tenter-type transverse stretcher for transverse stretching, followed by heat setting and relaxation treatment to obtain a multilayer stretched film. In this embodiment, an example is provided in which an unstretched film containing polyamide resin (a1) and polyamide resin (a2) and a barrier layer are co-extruded, stretched, and then a sealant layer is provided. The stretching ratio is preferably within the same range as the value described above for the stretched film.

[0058] Furthermore, the multilayer film of this embodiment may be subjected to heat treatment or humidity control treatment depending on the application. Details thereof can be found in paragraph 0049 of International Publication No. 2021 / 070500, which is incorporated herein by reference. Furthermore, when forming a multilayer film using an unstretched polyamide film as another layer, reference can be made to paragraphs 0080-0092 of International Publication No. 2017 / 073560, paragraph 0049 of International Publication No. 2021 / 070500, and paragraphs 0046-0050 of International Publication No. 2021 / 070500, which are incorporated herein by reference. Furthermore, with respect to the manufacture of stretched films and multilayer films, the descriptions in paragraphs 0025 to 0030 of Table 2019 / 208687 can be referenced without departing from the spirit of the present invention, and these contents are incorporated herein.

[0059] <Application> The stretched film or multilayer film of this embodiment is preferably used as a packaging material. Examples of packaging materials of this embodiment include those for food, medical, and cosmetic products. Packaging materials of this embodiment also include packaging containers. The contents that can be filled or packaged in the packaging material of this embodiment include confectionery such as rice crackers, bean snacks, nuts, biscuits, cookies, wafers, marshmallows, pies, semi-fresh cakes, candies, and snack foods; staples such as bread, instant noodles, dried noodles, pasta, aseptically packaged rice, rice porridge, packaged mochi, and cereal foods; processed agricultural products such as pickles, boiled beans, natto, miso, freeze-dried tofu, tofu, enoki mushrooms, konjac, processed wild vegetables, jams, peanut butter, salads, frozen vegetables, and processed potato products; processed livestock products such as ham, bacon, sausages, processed chicken products, and corned beef; and processed fish products such as fish ham, fish sausage, and processed seafood. Products include processed seafood such as kamaboko (fish cake), nori (seaweed), tsukudani (simmered seafood), katsuobushi (dried bonito flakes), shiokara (salted seafood), smoked salmon, and karashi mentaiko (spicy cod roe); fruits such as peaches, mandarins, pineapples, mangoes, apples, pears, and cherries; vegetables such as corn, asparagus, mushrooms, onions, carrots, radishes, and potatoes; frozen and chilled prepared foods such as hamburgers, meatballs, fried seafood, gyoza (dumplings), and croquettes; dairy products such as butter, margarine, cheese, cream, instant creamy powder, and infant formula; liquid seasonings, retort curry, and pet food; cigarettes, disposable hand warmers, pharmaceuticals, cosmetics, and batteries. [Examples]

[0060] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0061] 1.Raw materials <Sealant layer> Bio-based LLDPE: Biomass linear low-density polyethylene (bio-LLDPE), manufactured by Braskem.SA, SLL118 Petroleum-based PP: Petroleum-based polypropylene, manufactured by Japan Polypropylene Corporation, FY6 Petroleum-based LLDPE: Petroleum-based low-density polyethylene, manufactured by Japan Polyethylene Corporation, Novatec UF421

[0062] <Stretched film> MXD10: Synthesized according to the following synthesis example. <<Synthesis of MXD10>> Sebacic acid (manufactured by CASDA) was placed in a jacketed reactor equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping funnel, and a nitrogen gas inlet tube, and thoroughly purged with nitrogen. After heating and melting at 170 °C, while stirring the contents, metaxylylenediamine (manufactured by Mitsubishi Gas Chemical Company, MXDA) was gradually dropped in such that the molar ratio to sebacic acid was 1:1, while raising the temperature to 240 °C. After completion of the dropping, the temperature was raised to 260 °C and maintained for 20 minutes. Thereafter, the pressure inside the reaction system was continuously reduced to 0.08 MPa, and the reaction was continued. After completion of the reaction, the inside of the reactor was pressurized with nitrogen gas to 0.2 MPa, and the polymer was taken out as strands from the nozzle at the bottom of the polymerization tank, water-cooled, and pelletized with a pelletizer. The obtained pellets were dried in a vacuum dryer at 160 °C for 3 hours and then used. The relative viscosity was 2.6.

[0063] MP10(30): Synthesized according to the following synthesis example. <<Synthesis of MP10(P30)>> Sebacic acid (manufactured by CASDA) was placed in a jacketed reaction vessel equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping funnel, and a nitrogen gas inlet tube. After sufficient nitrogen replacement and heating to 170 °C to melt it, while stirring the contents, a mixed amine (70:30) of metaxylylenediamine and paraxylylenediamine (manufactured by Mitsubishi Gas Chemical Company, MPXDA) was gradually dropped in such that the molar ratio to sebacic acid became 1:1, and the temperature was raised to 240 °C. After completion of dropping, the temperature was raised to 260 °C and maintained for 20 minutes. Thereafter, the pressure inside the reaction system was continuously reduced to 0.08 MPa, and the reaction was continued. After completion of the reaction, the inside of the reaction vessel was pressurized with nitrogen gas to 0.2 MPa, and the polymer was taken out as a strand from the nozzle at the bottom of the polymerization tank, and after water cooling, it was pelletized with a pelletizer to obtain it. The obtained pellets were dried in a vacuum dryer at 180 °C for 2 hours and then used. The relative viscosity was 2.6.

[0064] PA6: Polyamide 6, manufactured by Ube Industries, Ltd., Ube Nylon 1022B PA666: Copolymer composed of polyamide 6 component and polyamide 66 component, polyamide 6 / 66, manufactured by Ube Industries, Ltd., Ube Nylon 5023B MXD6: Polyamide resin synthesized from metaxylylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, S6011 PA11 and PA1010 were synthesized according to the following synthesis examples.

[0065] <<Synthesis of PA11>> Aminoundecanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in a jacketed reaction vessel equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping funnel, and a nitrogen gas inlet tube. After sufficient nitrogen replacement and while stirring the contents, the temperature was raised to 220 °C and maintained for 20 minutes. Thereafter, the pressure inside the reaction system was continuously reduced to 0.08 MPa, and the reaction was continued. After completion of the reaction, the inside of the reaction vessel was pressurized with nitrogen gas to 0.2 MPa, and the polymer was taken out as a strand from the nozzle at the bottom of the polymerization tank, and after water cooling, it was pelletized with a pelletizer to obtain it. The obtained pellets were dried in a vacuum dryer at 90 °C for 6 hours and then used.

[0066] <<Synthesis of PA1010>> Sebacic acid (manufactured by CASDA) was placed in a jacketed reactor equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping tank, and a nitrogen gas inlet tube. After sufficient nitrogen replacement and heating to 100 °C to melt it, while stirring the contents, 1,10-diaminodecane was gradually dropped in such that the molar ratio to sebacic acid was 1:1, and the temperature was raised to 180 °C. After completion of dropping, the temperature was raised to 220 °C and maintained for 20 minutes. Thereafter, the pressure inside the reaction system was continuously reduced to 0.08 MPa, and the reaction was continued. After completion of the reaction, the inside of the reactor was pressurized with nitrogen gas to 0.2 MPa, and the polymer was taken out as a strand from the nozzle at the bottom of the polymerization tank, and pelletized with a pelletizer after water cooling. The obtained pellets were dried in a vacuum dryer at 90 °C for 6 hours and then used.

[0067] <Barrier layer> EVOH: Ethylene-vinyl alcohol copolymer, manufactured by Kuraray Co., Ltd., Eval F104B MXD6: Polyamide resin synthesized from metaxylylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, Inc., S6011 MXD610 was synthesized according to the following synthesis example.

[0068] MXD610 (20 mol% sebacic acid (SA)) was synthesized according to the following synthesis example. <<Synthesis example of MXD610 (SA 20 mol%)>> 10,000 g (68 mol) of adipic acid, 3,460 g (17.1 mol) of sebacic acid, 0.38 g of sodium hypophosphite monohydrate (NaH₂PO₂·H₂O) (5 ppm by mass in terms of the phosphorus atom concentration in the polyamide resin), and 0.15 g of sodium acetate were precisely weighed and charged into a reaction vessel equipped with a stirrer, a partial condenser, a total condenser, a thermometer, a dropping funnel, a nitrogen inlet tube, and a strand die. After sufficient nitrogen replacement, the system was filled with nitrogen to an internal pressure of 0.4 MPa, and then heated to 190 °C while stirring the inside of the system under a small amount of nitrogen gas flow. 11,813 g (87 mol) of metaxylylenediamine was added dropwise thereto with stirring, and the temperature inside the system was continuously raised while removing the generated condensed water out of the system. After completion of the dropwise addition of metaxylylenediamine, the internal temperature was raised, and when it reached 255 °C, the inside of the reaction vessel was depressurized, and the internal temperature was further raised to continue the melt polycondensation reaction at 260 °C for 10 minutes. Thereafter, the system was pressurized with nitrogen, and the obtained polymer was taken out from the strand die and pelletized to obtain polyamide MXD610 (SA 20 mol%).

[0069] MXD10: MXD10 obtained in the above <Synthesis of MXD10> was used.

[0070] 2. Measurement method <Transparency (stretched film, multilayer film)> For the multilayer film obtained above, haze (unit: %) was measured using a color and haze simultaneous measuring instrument. As the color and haze simultaneous measuring instrument, "COH400" manufactured by Nippon Denshoku Industries Co., Ltd. was used. Evaluation was carried out as follows. <<Stretched film>> A: Less than 1.0% B: 1.0% or more and less than 1.3% C: 1.3% or more and less than 2.0% D: 2.0% or more <<Multilayer film>> A: Less than 8.0% B: 8.0% or more

[0071] <Shrinkage rate (stretched film)> A square with a side of 100 mm and its diagonal were marked with an oil-based pen at the center of the stretched film, and the length of each side of the square was measured to one decimal place. The stretched film was immersed in an autoclave filled with water and heated at 100 °C for 30 minutes. The film after heating and cooling was taken out, the lengths of the previously marked square and diagonal were measured, and the shrinkage rate was calculated using the initial length and the length after heating. Shrinkage rate = (Initial length - Length after heating) / Initial length × 100) A: Less than 10.0% B: 10.0% or more

[0072] <Water absorption rate (stretched film)> The stretched film was left standing in an environment of 50°C and 90% relative humidity, and the moisture content after one month was measured using a moisture meter (Nitto Seiko Analytech Co., Ltd., autosampler type moisture meter CA-310) at an evaporation temperature of 185°C. A: Less than 1.8% B: 1.8% or more and less than 2.5% C: 2.5% or more

[0073] <Oxygen barrier properties (stretched film)> For stretched films, the oxygen permeability (OTR) was measured using the isobaric method under an atmosphere of 23°C and 60% relative humidity (RH), and the oxygen permeability coefficient (OTC) was calculated from the measurement results (unit: cc·mm / m). 2 The pressure under an oxygen atmosphere was set to 1 atm, and the measurement time was 24 hours. The oxygen permeability coefficient (OTC) was calculated as follows. OTC = OTR × Film thickness (μm) / 1000 Oxygen permeability (OTR) was measured using an oxygen permeability meter (MOCON Corporation, product name: "OX-TRAN(registered trademark) 2 / 21"). A: 0.52 cc·mm / m 2 Less than ATM day B: 0.52 cc·mm / m 2 • ATM • Day or more 1.0cc • mm / m 2 Less than ATM day C: 1.0 cc·mm / m 2 ·atm·day or more

[0074] <Pinhole resistance, 3000 times / number of holes (stretched film)> A stretched film was cut into 25cm squares and mounted on a pinhole resistance tester. The film was subjected to a continuous 440° torsional motion and a 65mm linear motion at a speed of 40 times / minute, causing it to be refracted 3000 times. The number of pinholes in the film after refraction was measured using a pinhole inspection machine, and the results were measured for 100cm of film. 2The number of pinholes per 100cm of film was calculated. 2 The number of pinholes per unit is calculated as follows: Number of pinholes (per 100cm) 2 ) = Total number of pinholes (pieces) / Effective test area (cm²) 2 ) × 100 In this embodiment, a Gelboflex tester manufactured by Rigaku Industries Co., Ltd. was used as the pinhole resistance tester, and a POROSCOPE DC manufactured by Fischer was used as the pinhole inspection machine. A: 5 or less B: 6 or more and 10 or less C: 11 or more

[0075] <Easily tearable (multilayer film)> A straight line was drawn in the MD (machine direction) and two straight lines were drawn in the TD (transverse direction) of the multilayer film obtained above. The distance between the two straight lines in the TD was set to 20 cm. The deviation width (in mm) of the TD when the film was torn 20 cm along the MD was defined as the straight-line cutability. It was evaluated as follows. A: Less than 3mm B: 3mm or more and 5mm or less C: More than 5mm

[0076] 3. Examples 1-11, Comparative Examples 1-6 <Manufacturing of stretched film> Two or three of the polyamide resins (a1), (a2), and (a3) ​​shown in Tables 1-3 were dry-blended and then supplied to a single-screw extruder with a T-die (PTM-30, manufactured by Plastics Engineering Laboratory Co., Ltd.) for mixing. The mixture was melt-extruded from the die at an extrusion temperature of 260°C. Specifically, the resin composition in which each component was melt-mixed was extruded to obtain a film with a width of 175 mm and a thickness of 140 μm. The obtained film was cut into 112 mm squares. Subsequently, using a batch-type biaxial stretching machine (Tenter method, EX105-S5, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the film was stretched in the MD and TD directions respectively under an atmospheric atmosphere of 100°C, with stretching ratios of 2.5 times in the MD direction, 2.5 times in the TD direction, and an overall stretching ratio of 6.25 times, to obtain a stretched film with a thickness of 20 μm. In this stretching process, a relaxation rate of 2.5% for both MD and TD directions was incorporated. After stretching, heat fixing was performed. The heat fixing temperature was 170°C and the heat fixing time was 45 seconds. The resulting stretched film was measured for transparency, shrinkage rate, water absorption, oxygen barrier properties, and pinhole resistance according to the method described above.

[0077] <Manufacturing of multilayer films> The obtained polyamide resins (a1), (a2), and (a3) ​​were dry-blended in the amounts shown in the table below. The barrier resins were then used to form multilayer structures (multilayer films) consisting of a polyamide resin layer and a barrier layer. These were done using two single-screw extruders (manufactured by Plastics Engineering Laboratory Co., Ltd., screw diameter 40 mm) and a multilayer film molding machine equipped with a channel for forming a multilayer structure with two types of T-dies and two layers. The extrusion temperature was 240°C and the post-lamination channel temperature was 240°C. The thickness of the polyamide resin layer was 130 μm, the thickness of the barrier layer was 70 μm, and the total thickness of the multilayer film was 200 μm. The obtained multilayer film was cut into 120 mm squares. Subsequently, using a batch-type biaxial stretching apparatus (Tenter method, EX10-S5, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the film was stretched in the MD and TD directions respectively under heating conditions of 100°C in an atmospheric environment, with stretching ratios of 2.5x for the MD and 2.5x for the TD, resulting in an overall stretching ratio of 6.25x. A stretched film with a thickness of approximately 30 μm was obtained. During this stretching process, relaxation operations were incorporated to achieve relaxation rates of 2.5% for both the MD and TD directions. After stretching, heat setting was performed. The heat setting temperature was 170°C and the heat setting time was 45 seconds to obtain a stretched multilayer film (polyamide resin layer / barrier layer). Separately, the resin used for the sealant layer was supplied to a single-screw extruder with a T-die (PTM-30, manufactured by Plastics Engineering Laboratory Co., Ltd.) and melt-extruded from the die at an extrusion temperature of 220°C. Specifically, a resin composition in which each component was melt-kneaded was extruded to obtain a sealant layer film with a width of 175 mm and a thickness of 70 μm. The obtained sealant layer film was coated with adhesive on its surface, and the sealant layer film and the stretched multilayer film (the polyamide resin layer side of the multilayer film with a polyamide resin layer / barrier layer) were dry-laminated using a laminator (MKS "Halder Laminator MRK") to obtain a multilayer film (approximately 100 μm thick) consisting of a sealant layer / adhesive layer / polyamide resin layer / barrier layer. The transparency and tearability of the obtained multilayer films were measured according to the method described above.

[0078] 3. Reference examples 1 and 2 <Manufacturing of stretched film> The procedure was the same as in Example 1, except that the type of polyamide resin was changed as shown in Table 3, and everything else was the same. The resulting stretched film was measured for transparency, shrinkage rate, water absorption, oxygen barrier properties, and pinhole resistance according to the method described above.

[0079] <Manufacturing of multilayer films> A sealant layer film was attached to the stretched film as described above, in the same manner as in Example 1, to form a multilayer film. The transparency and tearability of the obtained multilayer films were measured according to the method described above.

[0080] [Table 1]

[0081] [Table 2]

[0082] [Table 3]

[0083] As is clear from the results above, the stretched film of the present invention exhibited excellent transparency. Furthermore, it had a low shrinkage rate during stretching, low water absorption, excellent oxygen barrier properties, and excellent pinhole resistance. Furthermore, the multilayer film of the present invention exhibited excellent transparency and also excellent tear resistance. [Explanation of symbols]

[0084] 1. Sealant layer 2. Stretched film 3. Barrier layer

Claims

1. A stretched film comprising polyamide resin (a1) and polyamide resin (a2), The polyamide resin (a1) contains a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, wherein 70 mol% or more of the diamine-derived structural unit is derived from metaxylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural unit is derived from sebacic acid. The polyamide resin (a2) is such that 35 mol% or more of its total constituent units are derived from monomers having linear alkylene groups and having 5 to 7 carbon atoms. The constituent unit having a linear alkylene group in the polyamide resin (a2) is at least one selected from -[NH(CH2)n1CO]-, -[NH(CH2)n2NH]-, and -[CO(CH2)n3CO]-, where n1 is an integer from 4 to 6, n2 is an integer from 5 to 7, and n3 is an integer from 3 to 5. The polyamide resin (a2) comprises polyamide 6 and / or polyamide 6 / 66. A stretched film in which the mass ratio of the polyamide resin (a1) to the polyamide resin (a2) is 5 / 95 to 19 / 81.

2. The stretched film according to claim 1, which is a uniaxially stretched film.

3. The stretched film according to claim 1 or 2, which is a biaxially oriented film.

4. The stretched film according to claim 3, which is an easily tearable film.

5. A multilayer film comprising the stretched film described in claim 3 and other layers.

6. The multilayer film according to claim 5, wherein the other layer includes a sealant layer.

7. The multilayer film according to claim 6, wherein the other layer includes a barrier layer, and the sealant layer, the stretched film, and the barrier layer are laminated in that order, and the stretched film is a biaxially oriented film.

8. The aforementioned other layer includes a barrier layer, The barrier layer comprises a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, wherein 70 mol% or more of the diamine-derived structural unit is derived from metaxylylenediamine, and 70 mol% or more of the dicarboxylic acid-derived structural unit is derived from adipic acid, and the barrier layer comprises an oxygen barrier resin. The stretched film comprises polyamide 6, a polyamide resin comprising diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol% or more of the diamine-derived structural units are derived from metaxylylenediamine. The multilayer film according to claim 5, wherein the barrier layer and the stretched film are in contact.

9. The multilayer film according to claim 8, wherein the barrier layer and the stretched film are stretched at the same stretching ratio.

10. A packaging material comprising the stretched film described in claim 1.

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