CN112703111B

CN112703111B - Polyamide laminated film and method for producing same

Info

Publication number: CN112703111B
Application number: CN201980050200.9A
Authority: CN
Inventors: 松本真实
Original assignee: Unitika Ltd
Current assignee: Unitika Ltd
Priority date: 2018-07-31
Filing date: 2019-07-30
Publication date: 2023-11-03
Anticipated expiration: 2039-07-30
Also published as: WO2020027089A1; JPWO2020027089A1; TW202015916A; TWI842725B; CN112703111A; JP7336142B2

Abstract

The present invention aims to provide a polyamide-based laminated film which can exhibit excellent electrolyte resistance even when the protective layer is thin. The polyamide-based laminated film of the present invention is characterized by comprising a polyamide-based film base material (11) and a protective layer (12) formed on at least one surface of the base material, wherein (1) the protective layer (12) is formed so as to directly contact the surface of the polyamide-based film base material (11); (2) At least 1 protective layer (12) is arranged as the outermost surface layer of the polyamide-based laminated film; (3) The protective layer (12) contains a copolymerized polyester resin which contains a dicarboxylic acid component and a diol component as constituent components, and has 50 mol% or more of a dicarboxylic acid component having a naphthalene skeleton in 100 mol% of a constituent unit derived from a dicarboxylic acid; the thickness of the protective layer (4) is 1.5 μm or less.

Description

Polyamide laminated film and method for producing same

Technical Field

The present invention relates to a polyamide-based laminated film used for packaging or coating various products, particularly electronic components, electronic devices, and the like.

Background

Conventionally, a laminate film including a polyamide film has been used as a material for exterior packaging of a battery (lithium ion secondary battery or the like). As a typical example, a laminate in which polyamide films/aluminum foils/sealing layers are laminated in this order is known. In a lithium ion secondary battery using this laminate as an exterior material, the laminate is processed into a container shape such that the polyamide film is disposed outside the battery and the sealing layer is disposed inside (inside the battery). Then, after the electrodes and the like are packaged in the container, an electrolyte is injected.

In manufacturing such a lithium ion secondary battery, a step of injecting an electrolyte into the battery, a step of heat-sealing an exterior material after the injection, and the like are performed. In these steps, the electrolyte may be sprayed out and attached to the polyamide film on the outer side of the exterior material. Since the polyamide film has low resistance to the electrolyte (electrolyte resistance), when the polyamide film is disposed outside as in the laminate, the electrolyte adheres to the polyamide film, causing whitening of the film surface, decomposition reaction, and the like. As a result, defects in the appearance of the product, a decrease in the strength of the film, and the like may be caused. Further, when the electrolyte solution intrudes from the deteriorated portion of the polyamide film and contacts the aluminum foil, there is a concern that the aluminum foil is corroded. In this case, there is caused a problem that the exterior material loses the required strength.

In order to solve the above-mentioned problems, a method of providing a protective layer on the surface of the outer side of the polyamide film has been proposed. For example, patent document 1 discloses an exterior material using a polyethylene terephthalate film as a protective layer. Patent document 2 discloses a coating material using a film obtained by stretching a laminate of a polyester film and a polyamide film. Patent documents 3 to 5 disclose exterior materials in which a coating layer containing a specific resin is laminated as a protective layer on the outermost layer.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2002-56824

Patent document 2: japanese patent laid-open publication No. 2013-240938

Patent document 3: japanese patent laid-open No. 2000-123799

Patent document 4: japanese patent application laid-open No. 2014-176999

Patent document 5: japanese patent application laid-open No. 2014-176998

Disclosure of Invention

Problems to be solved by the invention

The exterior materials of patent documents 1 and 2 use a polyester film as a protective layer for a polyamide film. However, since a step of laminating the polyester film is required in addition to a step of providing an adhesive layer between the polyamide film and the polyester film, the manufacturing process becomes complicated and cost reduction is hindered. In addition, since the total weight increases the weight of the adhesive, it is disadvantageous in terms of weight reduction of the battery.

The coatings disclosed in patent documents 3 to 5 contain a resin component such as polyvinylidene chloride or polyurethane. However, in order to impart a sufficient protective function to the electrolyte, it is necessary to secure a thickness of at least 1 μm or more as the protective layer. Therefore, in addition to the material cost of the protective layer itself, the energy cost required for the drying process is also high, which is economically disadvantageous. Further, since the protective layer is formed by the post-coating method, there is a concern that the heat of the drying step may adversely affect the physical properties of the base film, in addition to the increase in the number of steps and the cost.

Accordingly, a primary object of the present invention is to provide a polyamide-based laminated film which exhibits excellent electrolyte resistance even when the protective layer is thin.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by providing a protective layer comprising a specific copolyester resin on the surface of a polyamide film, and have further completed the present invention.

That is, the present invention relates to the following polyamide-based laminated film and a method for producing the same.

1. A polyamide-based laminated film comprising a polyamide-based film base material and a protective layer formed on at least one surface of the base material,

(1) The protective layer is formed so as to directly contact the surface of the polyamide-based film base material;

(2) At least 1 protective layer is arranged as the outermost surface layer of the polyamide-based laminated film;

(3) The protective layer contains a copolymerized polyester resin which contains a dicarboxylic acid component and a diol component as constituent components, and the dicarboxylic acid component having a naphthalene skeleton is contained in an amount of 50 mol% or more in 100 mol% of the constituent units derived from the dicarboxylic acid; and

(4) The thickness of the protective layer is 1.5 μm or less.

2. The polyamide-based laminated film according to the above item 1, which satisfies the following formula (1):

(HzX) - (Hz 0) < 3.0 … (1)

(wherein the above Hz0 is a haze value measured in accordance with Japanese Industrial Standard "JIS K7136", the above HzX is a haze value measured in the same manner as Hz0 after holding at a temperature of 23℃and a humidity of 50% RH for 12 hours in a state where an electrolyte is attached to a protective layer after measuring the above Hz0, the above electrolyte is a mixture comprising ethylene carbonate/diethyl carbonate/methylethyl carbonate=1:1:1 (volume ratio) ₆ Diluted to a concentration of 1 mole/L. )

And Hz0 is in the range of 10 or less.

3. The polyamide-based laminated film according to the above 1, wherein the surface roughness (Ra) of the protective layer is 45nm or less.

4. The polyamide-based laminate film according to the item 1, wherein the glass transition temperature of the copolyester resin is 60 to 145 ℃.

5. The polyamide-based laminated film according to the above 1, wherein the protective layer further comprises at least 1 of a melamine resin, an isocyanate compound, a carbodiimide compound and an oxazoline compound.

6. The polyamide-based laminated film according to any one of the preceding claims 1 to 5, wherein the protective layer is laminated so as to be in direct contact with at least one surface of the polyamide-based film base material, and the polyamide-based laminated film is a laminate of:

(a) A laminate comprising a protective layer, a polyamide-based film substrate, a barrier layer, and a heat-sealing layer in this order; or (b) a laminate comprising, in order, a protective layer, a polyamide-based film substrate, a protective layer, a barrier layer, and a heat-sealing layer.

7. The polyamide based laminate film according to any one of the preceding claims 1 to 6, which is used for packaging an article.

8. A battery, comprising:

a power generation element including a negative electrode, a positive electrode, a separator, and an electrolyte; and

An exterior material for packaging the power generation element,

the exterior material is the polyamide-based laminated film according to any one of the above items 1 to 5, and the protective layer is disposed as the outermost layer of the battery.

9. A method for producing a polyamide-based laminated film according to any one of claims 1 to 5, comprising:

(1) A step of applying a coating liquid for forming a protective layer, which contains a copolymerized polyester resin containing a dicarboxylic acid component and a diol component as constituent components, to an unstretched polyamide-based film or a uniaxially stretched polyamide-based film, wherein the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of the dicarboxylic acid component; and

(2) And stretching the polyamide film having the coating film obtained by the coating, thereby obtaining a polyamide laminated film having a protective layer formed on one or both sides of the biaxially stretched film stretched in the MD and TD directions.

Effects of the invention

According to the present invention, a polyamide-based laminated film can be provided which exhibits excellent electrolyte resistance even when the protective layer is thin.

In particular, since the protective layer of the polyamide-based laminated film of the present invention contains a copolymerized polyester resin having 50 mol% or more of a dicarboxylic acid component having a naphthalene skeleton among the acid components, excellent electrolyte resistance can be exhibited even if the thickness of the protective layer is 1.5 μm or less, which is a thin thickness. Therefore, even when the electrolyte adheres, whitening, decomposition reaction, and the like of the polyamide film can be effectively suppressed. As a result, the strength of the polyamide-based laminated film can be maintained continuously.

In addition, since the surface roughness of the protective layer is small (less irregularities), droplets are less likely to remain even when the electrolyte adheres. Therefore, deterioration of the protective layer due to adhesion of the electrolyte for a long period of time can be prevented.

Further, since the thickness of the protective layer is small, the polyamide-based laminated film can be made thin, and therefore even when the film is coated in a state of being adhered to a packaged body, excellent molding follow-up property can be obtained. Therefore, the resin composition is suitably used as a lithium ion secondary battery exterior material requiring adhesion and the like.

Since the thickness of the protective layer is as thin as 1.5 μm or less, it can be easily formed under a relatively mild heat treatment condition, and therefore, the influence on the physical properties of the polyamide-based film substrate can be suppressed to a minimum. This can contribute to the realization of a polyamide-based laminated film which is excellent in both electrolyte resistance, mechanical properties, blocking resistance, and the like.

In particular, an electrolyte used for a lithium ion secondary battery is a liquid having conductivity prepared by dissolving an ionic substance in a polar solvent. The ionic substance is usually lithium hexafluorophosphate (LiPF) ₆ )。LiPF ₆ When reacted with water, hydrofluoric acid (hydrogen fluoride) is produced as a strongly acidic medium. Thus, in the case of the electrolyte adhering to the air, the moisture in the air will be compatible with the LiPF in the electrolyte ₆ Reacts to produce hydrofluoric acid. The polyamide film used for the lithium ion secondary battery exterior material is dissolved by the hydrofluoric acid. In contrast, the polyamide-based laminated film of the present invention has the specific protective layer as described above, and therefore even if it contains LiPF ₆ And the like, the polyamide film can maintain the strength without deterioration.

In the production method of the present invention, a specific coating liquid for forming a protective layer can be coated in-line to form a protective layer, and therefore, a polyamide-based laminated film excellent in electrolyte resistance and the like as described above can be produced at low cost on an industrial scale. In particular, since the thickness of the protective layer can be as thin as 1.5 μm or less, it can be easily formed by in-line coating under relatively mild conditions, and as a result, the influence on the physical properties of the polyamide-based film substrate or the like can be suppressed to a minimum. In this respect, it is also advantageous to realize a polyamide-based laminated film which is excellent in both electrolyte resistance, mechanical properties, blocking resistance, and the like.

In the production method of the present invention, since the protective layer is formed by in-line coating with the specific protective layer forming coating liquid, the surface of the protective layer can be further flattened. This also contributes to improvement of electrolyte resistance. Although the reason for this is not clear, it is presumed that the mechanism of action is as follows. In the in-line coating method, a coating film obtained by using a coating liquid for forming a protective layer is subjected to stretching and heat treatment together with a polyamide film, and a high-density coating film containing a copolyester resin as a main component is formed by heat treatment while stretching, whereby the surface of the protective layer is smoothed and a surface having less surface irregularities can be formed. As a result, it is presumed that the surface of the protective layer has less irregularities, and therefore, the electrolyte is less likely to remain, even if the electrolyte adheres to the surface, and thus, a protective layer having high protective performance against the electrolyte can be obtained.

The polyamide-based laminated film of the present invention having such characteristics is suitable for use in applications where adhesion of an electrolyte (or an acidic liquid) is a concern. In particular, the polymer electrolyte is suitable for use as an exterior material for various batteries (in particular, laminate batteries) typified by lithium ion secondary batteries.

Drawings

Fig. 1 is a view showing an embodiment of a polyamide-based laminated film of the present invention.

Fig. 2 is a view showing an embodiment of the polyamide-based laminated film of the present invention.

Fig. 3 is a conceptual diagram showing a method for measuring thickness accuracy of the polyamide-based laminated film of the present invention.

Fig. 4 is an external view showing a battery using the polyamide-based laminate film of the present invention as an exterior material.

Fig. 5 is a schematic view showing the structure of a battery using the polyamide-based laminate film of the present invention as an exterior material.

Fig. 6 is a schematic view showing the structure of a battery using the polyamide-based laminate film of the present invention as an exterior material.

Detailed Description

1. Polyamide laminated film

The polyamide-based laminated film (film of the present invention) of the present invention comprises a polyamide-based film base material and a protective layer formed on at least one surface of the base material,

(3) The protective layer contains a copolymerized polyester resin which contains a dicarboxylic acid component and a diol component as constituent components, and has 50 mol% or more of a dicarboxylic acid component having a naphthalene skeleton in 100 mol% of a constituent unit derived from a dicarboxylic acid; and

(4) The thickness of the protective layer is 1.5 μm or less.

A. Layer structure of the inventive film

As described above, the film of the present invention is basically composed of a polyamide-based film base material and a protective layer formed on at least one side of the base material. That is, the laminate is basically constituted by a laminate in which a protective layer is formed adjacent to one or both surfaces of a polyamide film base material without an adhesive layer interposed therebetween.

Fig. 1 shows an example of a layer structure of the film of the present invention. Fig. 1A shows a laminate (film of the present invention) 10 in which a protective layer 12 is laminated on one side of a polyamide-based film base material 11. Fig. 1B shows a laminate (film of the present invention) 10' in which protective layers 12, 12 are laminated on both sides of a polyamide-based film base material 11. In any of these cases, the protective layer is configured as an outermost surface layer (outermost layer). When a package (bag or the like) using the film of the present invention is produced with the protective layer exposed as the outermost surface layer in this manner, for example, the contents of the package can be protected from the outside.

In the film of the present invention, as long as the protective layer is directly formed on the polyamide-based film base material as described above and at least 1 protective layer is arranged as the outermost surface layer, other layers may be further laminated. Examples thereof include barrier layers (gas barrier layers, vapor barrier layers, etc.), print layers, heat-seal layers (adhesive layers, sealant layers, heat-seal layers), primer layers (anchor coat layers), antistatic layers, vapor deposition layers, ultraviolet absorbing layers, ultraviolet blocking layers, and the like.

Fig. 2 shows an example of a layer structure of a polyamide-based laminated film in which an arbitrary layer is laminated in addition to a polyamide-based film base material and a protective layer. Fig. 2A shows a laminate 20 in which a barrier layer 13 and a heat fusion layer 14 are further laminated in this order on the laminate 10 of fig. 1A. In the laminate 20, the barrier layer 13 and the heat fusion layer 14 are laminated on the surface of the polyamide film base material 11 on which the protective layer 12 is not formed, and thus the protective layer 12 is maintained in an exposed state as the outermost surface layer. Fig. 2B shows a laminate 20 'obtained by further laminating a barrier layer 13 and a heat fusion layer 14 in this order on the laminate 10' of fig. 1B. In the laminate 20', the barrier layer 13 and the heat fusion layer 14 are laminated on the protective layer 12 on either side of the polyamide-based film base material 11, but the other protective layer 12 is maintained in a state of being exposed as the outermost surface layer. In addition, as shown in fig. 2, in the case where the film of the present invention has a heat fusion layer, the heat fusion layer is arranged as the outermost surface layer.

Hereinafter, the polyamide-based film base material and the protective layer constituting the film of the present invention will be described separately from any layer.

A-1 Polyamide film substrate

The polyamide-based film base material is a base material (core material) of the film of the present invention, and is usually provided in a form of a film formed in advance. The polyamide film base material may have a single-layer structure or a multilayer structure in which 2 or more polyamide films are laminated. In addition, in the case of a multilayer structure, the layers may have the same composition as each other or may have different compositions.

The polyamide film base material contains polyamide resin as a main component, and may contain other components. In this case, the content ratio of the polyamide resin in the polyamide film base material is not limited, but is preferably 70 to 100% by mass, particularly 90 to 99.5% by mass.

The polyamide resin may be a thermoplastic resin capable of being melt-molded and having an amide bond (-CONH-) in its molecule, and known or commercially available resins may be used. Thus, for example, polyamides obtained by polycondensation of lactams, omega-amino acids or dibasic acids with diamines are mentioned.

Examples of the lactams include epsilon-caprolactam, enantholactam, caprylolactam and laurolactam.

Examples of the ω -amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, and 11-aminoundecanoic acid.

Examples of dibasic acids include: adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, hexadecanedioic acid, eicosanedioic acid, eicosadienoic acid, 2, 4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, xylylene dicarboxylic acid, and the like.

Examples of diamines include: ethylenediamine, trimethylene diamine, tetramethylenediamine, pentamethylene diamine, hexamethylenediamine, nonamethylene diamine, decamethylene diamine, undecamethylenediamine, 2,4 (or 2, 4) -trimethylhexamethylene diamine, cyclohexane diamine, bis- (4, 4' -aminocyclohexyl) methane, m-xylylenediamine, and the like.

As the polymer obtained by polycondensing them or their copolymers, for example, can be used: nylon 6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 9T, 10T, 6I, MXD6 (poly (m-xylylenediamine adipamide)), 6/6.6, 6/12, 6/6T, 6/6I, 6/MXD6, and the like. These may be used in an amount of 1 or 2 or more. Among these, the polyamide resin preferably contains nylon 6, from the viewpoint of excellent balance between heat resistance and mechanical properties.

The relative viscosity of the polyamide resin used for the polyamide film base material is not particularly limited, but is usually about 1.5 to 5.0, and particularly preferably 2.0 to 4.0. If the relative viscosity of the polyamide is less than 1.5, the mechanical properties of the resulting film may be easily significantly lowered. On the other hand, if the relative viscosity exceeds 5.0, the film formability of the film tends to be impaired. The relative viscosity was measured using an Ubbelohde viscometer, and a sample solution (liquid temperature: 25 ℃) in which polyamide was dissolved in 96% sulfuric acid to a concentration of 1.0g/dl was obtained.

As described above, the polyamide-based film base material may contain other components in addition to the polyamide-based resin within a range that does not hinder the effects of the present invention. The other components may be known or commercially available additives. More specifically, metals (metal ions), pigments, heat stabilizers, antioxidants, weather-proofing agents, flame retardants, plasticizers, mold release agents, reinforcing agents (fillers), and the like can be exemplified. In particular, hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and the like are suitably used as heat stabilizers or antioxidants.

In order to improve the slipperiness of the film, it is preferable that at least one of at least 1 inorganic lubricant and organic lubricant be contained in a range where the surface roughness (Ra) is 45nm or less. Specific examples of the lubricant include inorganic lubricants such as clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass hollow spheres, carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, and layered silicate; organic lubricants such as erucamide, oleamide, stearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisoleic acid amide and methylene bisstearic acid amide.

The thickness of the polyamide-based film substrate is not particularly limited, but is usually preferably 4 to 30. Mu.m, particularly preferably 5 to 25. Mu.m. If the thickness is less than 4. Mu.m, the mechanical strength tends to be insufficient, and the formability tends to be lowered. On the other hand, if the thickness exceeds 30 μm, the weight increases, and it becomes difficult to use the film for the purpose of weight reduction. If the mechanical strength is sufficient, a thinner one can enclose more electrolyte, and therefore is preferable in terms of securing the content amount or the capacitance.

In addition, from the viewpoint of mechanical strength, the polyamide-based film base material is preferably a stretched base material. That is, a structure having orientation is preferable. In this case, the stretching may be either uniaxial stretching or biaxial stretching, but it is particularly preferable to have an orientation by biaxial stretching. The stretching ratio can be appropriately set in a range shown below.

The polyamide-based film base material preferably has a surface on which at least one surface is subjected to a known surface treatment such as corona treatment, plasma treatment, or ozone treatment in order to improve adhesion between layers constituting the laminate when the laminate is produced. Particularly preferably, the surface roughness is 10nm or more. In addition, from the viewpoints of electrolyte resistance and improvement of blocking resistance, it is preferable that the surface roughness of the protective layer is the same as or above that of the protective layer. That is, in the present invention, "the surface roughness of the protective layer is not more than the surface roughness of the polyamide-based substrate film" is preferable.

A-2 protective layer

The protective layer contains a copolyester resin containing a dicarboxylic acid component and a glycol component (glycol component) as constituent components, and the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of the constituent units derived from the dicarboxylic acid (hereinafter, this specific copolyester resin is referred to as "copolyester resin a"). As such a copolyester resin a, for example, it is possible to suitably use: and a copolymer obtained by polycondensation of the dicarboxylic acid component and the diol component.

(a) Copolyester resin A

Dicarboxylic acid component

The dicarboxylic acid component is not particularly limited, and examples thereof include: aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 2, 3-naphthalenedicarboxylic acid, 4-dicarboxybiphenyl, phenyl dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, and sodium 5-sulfone dicarboxylate (Japanese 5-naphazel acid); aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, dimer acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid; alicyclic dicarboxylic acids such as 1, 4-cyclohexanedicarboxylic acid; hydroxycarboxylic acids such as parahydroxybenzoic acid, and the like. These may be used in an amount of 1 or 2 or more.

Among these, examples of the dicarboxylic acid component having a naphthalene skeleton (hereinafter also referred to as "dicarboxylic acid component A") include 2, 6-naphthalene dicarboxylic acid, 1, 4-naphthalene dicarboxylic acid, 2, 3-naphthalene dicarboxylic acid, and the like. Among them, 2, 6-naphthalene dicarboxylic acid is particularly preferred in the present invention from the viewpoints of small steric hindrance and high crystallinity.

In the present invention, the dicarboxylic acid component a is contained in the dicarboxylic acid-derived structural unit (100 mol%) usually at 50 mol% or more, particularly preferably at 60 mol% or more, further more preferably at 70 mol% or more, and most preferably at 80 mol% or more. This ensures higher electrolyte resistance. The upper limit of the content of the dicarboxylic acid component is not particularly limited, and may be generally about 95 mol%.

In this case, the content of the dicarboxylic acid component other than the dicarboxylic acid component a (hereinafter referred to as "dicarboxylic acid component B") is not particularly limited, and is usually about 1 to 50 mol%, and particularly preferably 5 to 45 mol% in the constituent unit (100 mol%) derived from the dicarboxylic acid.

In the present invention, terephthalic acid is particularly preferably used as the dicarboxylic acid component B from the viewpoints of small steric hindrance and high crystallinity. When terephthalic acid is contained, the content of terephthalic acid in the dicarboxylic acid-derived structural unit (100 mol%) is not particularly limited, and is usually about 3 to 50 mol%, particularly preferably about 5 to 45 mol%, and most preferably about 10 to 40 mol%. Therefore, in the present invention, the dicarboxylic acid component may suitably be a composition containing 2, 6-naphthalene dicarboxylic acid and terephthalic acid. More specifically, there may be mentioned: the dicarboxylic acid-derived structural unit (100 mol%) has a composition comprising 50 mol% or more of 2, 6-naphthalene dicarboxylic acid and 5 mol% or more of terephthalic acid. Thus, for example, it is also possible to use: the dicarboxylic acid-derived structural unit (100 mol%) has a composition comprising 55 to 90 mol% of 2, 6-naphthalene dicarboxylic acid and 5 to 45 mol% of terephthalic acid.

In the present invention, the dicarboxylic acid component B may contain aliphatic dicarboxylic acids such as adipic acid and sebacic acid, but if the content of these acids is increased, the electrolyte resistance of the protective layer may be lowered, and therefore the content of aliphatic dicarboxylic acids in the constituent units (100 mol%) derived from dicarboxylic acids is preferably 20 mol% or less, particularly preferably 15 mol% or less, and particularly preferably 5 mol% or less.

In the case of using the dicarboxylic acid component B, the mixing ratio (molar ratio) of the dicarboxylic acid component A to the dicarboxylic acid component B is usually about 50:50 to 98:2, and particularly preferably about 80:20 to 95:5.

Glycol component

The diol component is not particularly limited, and examples thereof include: aliphatic dihydroxy compounds such as ethylene glycol, diethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, and neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; alicyclic dihydroxy compounds such as 1, 4-cyclohexanedimethanol and spiroglycol; aromatic dihydroxy compounds such as bisphenol A. These may be used in an amount of 1 or 2 or more.

Among these, aliphatic dihydroxy compounds are preferable from the viewpoint of enhancing electrolyte resistance, and aliphatic dihydroxy compounds having 4 or less carbon atoms are more preferable. More specifically, at least 1 of ethylene glycol, diethylene glycol, 1, 2-propanediol, and 1, 3-propanediol can be mentioned.

The aliphatic dihydroxy compound is preferably contained in the structural unit (100 mol%) derived from the diol component in an amount of usually 50 mol% or more, particularly preferably 60 mol% or more, further preferably 70 mol% or more, and particularly preferably 80 mol% or more. The upper limit of the content is set to, for example, 100 mol%, but is not limited thereto.

In the present invention, for example, an aliphatic diol having 5 or more carbon atoms such as 1, 4-butanediol, 1, 5-pentanediol, and 1, 6-hexanediol may be contained, but if the content is too high, the electrolyte resistance tends to be low, and therefore the content of the aliphatic diol having 5 or more carbon atoms is preferably about 0 to 25 mol% based on 100 mol% of the constituent unit derived from the diol component.

Other copolymerization Components

In the case where the copolyester resin A is prepared as an aqueous coating liquid for forming a protective layer, the dicarboxylic acid component B preferably contains a solvent having a sulfo group (-SO) ₃ H) Particularly preferred is an aromatic dicarboxylic acid having a sulfo group. For example, at least 1 of isophthalic acid 5-sulfonic acid, isophthalic acid 2-sulfonic acid, isophthalic acid 4-sulfonic acid, terephthalic acid sulfonic acid and 4-sulfonaphthalene-2, 6-dicarboxylic acid is preferable, and isophthalic acid 5-sulfonic acid is particularly preferable from the viewpoint of cost. That is, a dicarboxylic acid component having no naphthalene skeleton and having a sulfo group is suitably used as the dicarboxylic acid component B. In the case of a compound belonging to dicarboxylic acid A, B, the content of the compound may be calculated as dicarboxylic acid B.

The content of the dicarboxylic acid component having a sulfo group is preferably 3.5 to 30 mol%, more preferably 4 to 20 mol%, and even more preferably 4 to 10 mol%, based on 100 mol% of the constituent unit derived from the dicarboxylic acid.

Physical Properties of the copolyester resin A

The glass transition temperature of the copolyester resin A is preferably 60℃or higher, particularly preferably 80℃or higher, and most preferably 100℃or higher. When the glass transition temperature is less than 60 ℃, the restraint force between the molecular chains constituting the copolyester resin becomes weak, and thus the electrolyte resistance may be poor.

On the other hand, as described later, the film of the present invention is preferably produced by applying a coating liquid for forming a protective layer to an unstretched or uniaxially stretched polyamide film and then stretching the film, but if the glass transition temperature of the copolyester resin a is high, the stretch following property with the polyamide film is lowered, and the film is easily cut, so that the glass transition temperature is preferably 145 ℃ or less, more preferably 140 ℃ or less.

In addition, the copolyester resin a may have a crosslinked structure. For example, the crosslinked structure may be formed by using a crosslinking agent that reacts with a carboxyl group or a hydroxyl group as a terminal group of the copolyester resin a. As a result, it is possible to exhibit more excellent electrolytic solution resistance, physical properties, and the like. The crosslinking agent is not particularly limited as long as the above reaction can be performed, but preferably contains at least 1 of melamine resin, isocyanate compound, carbodiimide compound, and oxazoline compound. These may be used as known or commercially available ones.

The crosslinking agent is contained in the protective layer preferably in an amount of 0.1 to 15% by mass, particularly preferably in an amount of 0.1 to 10% by mass, and most preferably in an amount of 2.5 to 7.5% by mass. When the content is within such a range, more excellent electrolytic solution resistance and the like can be obtained.

Synthesis of copolyester resin A

The copolyester resin A can be basically synthesized according to a known method for producing a copolyester resin, except that the specific dicarboxylic acid component and the diol component are used as described above. That is, the copolyester resin a is preferably produced by a production method comprising a step of polycondensing a dicarboxylic acid component containing 50 mol% or more of a dicarboxylic acid component having a naphthalene skeleton with a diol component in 100 mol% of the dicarboxylic acid component.

As the dicarboxylic acid component (dicarboxylic acid compound), at least 1 of derivatives such as a metal salt thereof, an acid anhydride thereof, and an ester compound thereof may be used in addition to the dicarboxylic acids exemplified above. These compounds may be the same as those used in the synthesis of the known copolyester resin.

As the diol component (diol compound), at least 1 of derivatives such as a metal salt thereof, an acid anhydride thereof, and an ester compound thereof can be used in addition to the diols exemplified above. These compounds may be the same as those used in the synthesis of a known copolyester resin.

The mixing ratio of the carboxylic acid component and the diol component can be appropriately set within a range where a predetermined polycondensation reaction can be sufficiently performed, and is usually set within a range where the molar ratio of the carboxylic acid component to the diol component=1:0.5 to 1:1.5, but the present invention is not limited thereto.

In addition, a polymerization catalyst may be added to the raw material as needed. The polymerization catalyst is not limited, and a known catalyst can be used, and for example, a titanium catalyst such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate can be suitably used. The amount of the polymerization catalyst to be added is not particularly limited, and may be usually 5X 10 based on 1 mol of the carboxylic acid component ^-5 ～5×10 ^-4 The molar range is appropriately adjusted.

The reaction system may be a liquid phase reaction, and the diol component is usually liquid, so that the reaction can be carried out particularly in the absence of a solvent. An organic solvent can be used as needed. In addition, as for the reaction atmosphere, the pressure may be any of normal pressure, reduced pressure (including vacuum), or pressurized. The atmosphere gas is usually an inert gas atmosphere such as nitrogen or argon.

The reaction is preferably carried out in 2 stages, the 2 stages comprising: a transesterification reaction step as stage 1 and a polymerization step as stage 2.

The reaction temperature in the transesterification reaction step is not particularly limited as long as all the components can be melted, and may be set to about 200 to 260 ℃. The reaction time depends on the reaction temperature and the like, and is usually in the range of about 1 to 5 hours.

The reaction temperature in the polymerization step is not particularly limited as long as the polymerization of the initial condensate (ester compound) can be carried out, and may be set to about 200 to 260 ℃. The reaction time depends on the reaction temperature and the like, and is usually in the range of about 1 to 5 hours. In particular, in the polymerization step, the polymerization is preferably carried out under reduced pressure or under vacuum, more specifically, 1X 10 is preferably set ^-5 About 1X 10 Pa. Therefore, it can be set to, for example, 1×10 ^-4 About 1X 5Pa, or 1X 10Pa ^-5 ～1×10 ^-1 About Pa.

The obtained reaction product is usually liquid at normal temperature and pressure, and thus can be used as a raw material of a coating agent for forming a protective layer. If necessary, the liquid reaction product may be subjected to solid-liquid separation, purification, and other treatments, and then separated. Thus, a copolyester resin A was obtained.

In the present invention, the copolyester resin a may be further reacted with a crosslinking agent in order to have a crosslinked structure as needed. When the crosslinking agent is contained, the crosslinking density of the protective layer is increased by reacting with one or both of the carboxyl group and the hydroxyl group as the terminal group of the copolyester resin, and thus the electrolyte resistance of the protective layer can be further improved. In the case of using the in-line coating method, the compound having a relatively remarkable effect of improving the electrolyte resistance of the protective layer by the crosslinking agent is at least 1 kind of blocked isocyanate or oxazoline, and particularly preferably, oxazoline.

The amount of the crosslinking agent to be added may be adjusted as appropriate, as long as the protective layer contains a specific proportion as described above, for example, in the range of about 1 to 15 parts by mass relative to 100 parts by mass of the copolyester resin a. When the crosslinking agent is added, the crosslinking agent may be added to the copolyester resin A, mixed, and held for a certain period of time. The holding temperature in this case is not particularly limited, and is usually about 5 to 30 ℃. The holding time is usually about 0 to 120 hours.

(b) Composition and physical properties of protective layer

As described above, the protective layer contains the copolyester resin a, and the content of the copolyester resin a in the protective layer is preferably 70 to 100% by mass, and particularly preferably 80 to 95% by mass.

Therefore, the protective layer may contain components other than the copolyester resin A within a range that does not inhibit the effect of the present invention. Examples thereof include: various additives such as lubricants, heat stabilizers, antioxidants, reinforcing materials (fillers), pigments, deterioration inhibitors, weather-proofing agents, flame retardants, plasticizers, mold release agents, and crosslinking agents. These may be used as the same additives as those used for the polyamide-based film base material described above.

In particular, examples of the lubricant include: organic lubricants such as ethylene bisstearamide, organic particles such as acrylic particles, and inorganic particles such as silica. Since these can also function as an anti-blocking agent, it is preferable to add 1 or 2 or more of the above lubricants.

Examples of the heat stabilizer, antioxidant and anti-deterioration agent include: hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, or mixtures of these.

Examples of the reinforcing material include: clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminum silicate, magnesium silicate, glass hollow spheres, carbon black, zinc oxide, zeolite, hydrotalcite, metal fibers, metal whiskers, ceramic whiskers, potassium titanate whiskers, boron nitride, graphite, glass fibers, carbon fibers, and the like. These may be added in 1 or 2 or more.

From the viewpoint of further improving the electrolyte resistance, an inorganic layered compound may be contained. The inorganic layered compound is an inorganic compound in which single crystal layers (Japanese: unit crystalline run) are stacked to form a layered structure, and specifically includes zirconium phosphate (phosphate derivative type compound), chalcogenides, lithium aluminum composite hydroxide, graphite, clay minerals, and the like, and particularly preferably one that swells or cracks in a solvent (Japanese: split).

The thickness of the protective layer is required to be 1.5 μm or less, and particularly preferably 1 μm or less from the viewpoints of improvement in productivity, blocking resistance, and the like due to shortening of the drying time. The protective layer having a thickness exceeding 1.5 μm may be uneven in the protective layer forming step or the drying step, may be reduced in productivity due to a longer heat treatment time, or may be disadvantageous in economical terms due to an increased cost of the coating liquid, and may be poor in blocking resistance.

On the other hand, the lower limit of the protective layer thickness is preferably 0.05 μm or more, particularly preferably 0.1 μm or more, further preferably 0.2 μm or more, and particularly preferably 0.4 μm or more, in order to sufficiently improve the resistance to an acidic liquid such as an electrolyte.

The surface roughness Ra of the protective layer (exposed surface) is not particularly limited, but is preferably 45nm or less, particularly preferably 40nm or less, and particularly preferably 35nm or less, from the viewpoint of improving electrolyte resistance. If the surface roughness of the protective layer exceeds 45nm, the electrolyte may be easily retained in the protective layer, and the electrolyte resistance may be impaired. The lower limit value of the surface roughness Ra may be, for example, 20nm or 15nm, but is not limited thereto. The surface roughness can be controlled to 45nm or less by forming a protective layer by an in-line coating method using a predetermined coating liquid for forming a protective layer, for example, as will be described later.

A-3 other layers

As described above, the film of the present invention may be laminated with various layers as required, in addition to the polyamide-based film base material and the protective layer. The layers themselves may be the same layers as those used for known packaging materials and the like. As shown in fig. 2, the film of the present invention is useful as a battery exterior material, for example, a laminate including a protective layer/polyamide film base material/barrier layer/heat-seal layer, or a laminate including a protective layer/polyamide film base material/protective layer/barrier layer/heat-seal layer. Preferred embodiments of the barrier layer and the heat-seal layer will be described herein.

Barrier layer

The barrier layer may be a barrier layer which exhibits gas barrier properties (oxygen barrier properties) and water vapor barrier properties, and for example, a known or commercially available barrier layer or film such as a metal foil or a vapor deposited film may be used. Among them, a metal foil having a wide range of applications is preferable. The metal foil is preferably aluminum foil, but is not limited thereto. For example, various barrier layers used for the exterior material of the lithium ion secondary battery may be used.

The thickness of the barrier layer is not particularly limited, but is usually about 20 to 200. Mu.m, and particularly preferably 30 to 150. Mu.m.

In addition, it is preferable to perform surface treatment suitable for a lithium ion secondary battery exterior material on the surface of one side or both sides of the barrier layer. Examples of the surface treatment include chemical conversion treatment and chromate treatment. In particular, these surface treatments are preferably performed on the side of the barrier layer that is in contact with the heat fusion layer.

Thermal fusion layer

The heat-seal layer is not particularly limited as long as it can be heat-sealed, and for example, a known layer suitable for use as an exterior material of a lithium ion secondary battery or the like can be used. Specifically, polyvinyl chloride films, polyolefin films, and the like can be suitably used. Examples of the polyolefin include polyethylene, polypropylene, a copolymer containing polypropylene as a main component, and an acid-modified product thereof. The heat-seal layer may use either a stretched film or an unstretched film.

The method for forming the heat-seal layer is not particularly limited, and any of, for example, a method of applying a coating liquid containing a heat-seal component, a method of laminating films obtained by forming a resin composition containing a heat-seal component into a film in advance, and the like can be used.

The thickness of the heat-seal layer is not particularly limited as long as the desired heat-seal property can be obtained, and is generally about 20 to 200 μm, and more preferably 30 to 100 μm.

B. Characteristics of the inventive film

The thickness (total thickness) of the film of the present invention can be appropriately set according to the application, the method of use, etc. For example, when the film of the present invention is used as a battery exterior material, it is preferably about 10 to 25 μm, and particularly preferably 15 to 25 μm.

In addition, it is desirable that the film of the present invention have high thickness accuracy (thickness uniformity). That is, the standard deviation value with respect to the average thickness is generally preferably 0.200 or less, particularly preferably 0.180 or less, and most preferably 0.160 or less.

The above-described thickness accuracy evaluation method is performed as follows. After the film of the present invention was subjected to humidity control at 23 ℃ x 50% rh for 2 hours, 8 lines L1 to L8 of total 8 100mm were drawn from the center point a toward the reference direction (a), 45-degree direction (b), 90-degree direction (c), 135-degree direction (d), 180-degree direction (e), 225-degree direction (f), 270-degree direction (g), and 315-degree direction (h) after the reference direction (0-degree direction) was designated with respect to the arbitrary point a on the film as shown in fig. 3. On each straight line, the thickness was measured at 10mm intervals from the center point A (10 points were measured) using a length meter "HEIDENHAIN-METRO MT1287" (manufactured by Heidenhain Co.). Fig. 3 shows a state in which a measurement point (10 points) is determined when L2 in the 45-degree direction is measured, as an example. Then, the average value of the measured values of 80 points in total of the data obtained by measuring all the straight lines was calculated, and the average thickness was used as the average thickness, and the standard deviation value with respect to the average thickness was calculated. The reference direction is not particularly limited, and MD in the stretching step at the time of film production may be used as the reference direction, for example.

In the present invention, the average thickness and standard deviation may be determined based on any point (point a) of the polyamide-based film, and in particular, in the obtained polyamide-based film wound around the film roll, the average thickness and standard deviation in the above-described range are more preferably determined at any of the following 3 points. The 3 point is located at the following position: a) A position near the center of the roll width and corresponding to half the roll amount; b) A position near the right end of the roll width and corresponding to half the roll amount; and c) a position near the left end of the roll width and near the roll end.

The film of the present invention has excellent electrolyte resistance, and preferably has a value satisfying the following formula (1) as an index thereof.

(HzX) - (Hz 0) < 3.0 … (1)

Hz0: haze value measured according to Japanese Industrial Standard "JIS K7136". The haze value may be measured using a commercially available measuring device (for example, a haze meter "NDH 4000" manufactured by japan electric color corporation).

HzX: after Hz0 was measured, the haze value measured in the same manner as Hz0 was used after 12 hours at a temperature of 23 ℃ and a humidity of 50% rh in a state where an electrolyte solution shown below was attached to the protective layer.

The electrolyte is used: liPF is blended in a mixed solution containing ethylene carbonate/diethyl carbonate/methylethyl carbonate=1:1:1 (volume ratio) ₆ And diluting the obtained liquid to a concentration of 1 mol/L. This is then applied10ml of the electrolyte was dropped onto the protective layer side, and the solution was left to stand at a temperature of 23℃and a humidity of 50% RH for 12 hours in a state where the electrolyte was adhered. Thereafter, the electrolyte on the protective layer was wiped off with gauze and Hz0 was measured.

In this way, the haze value before the electrolyte was dropped was set to Hz0, and the haze value measured after the electrolyte was dropped for 12 hours was set to HzX.

As described above, the value of the above formula (1) is usually less than 3, particularly preferably 2 or less, further more preferably 1.8 or less, and most preferably 1 or less. If the value of the above formula (1) is large, corrosion by the electrolytic solution occurs, and the result means that whitening occurs, indicating poor electrolytic solution resistance. The lower limit of the value is not particularly limited, and may be, for example, 0.1.

The haze value (Hz 0) of the film of the present invention before the electrolyte is dropped is not particularly limited, but is usually preferably 10 or less, and more preferably 5 or less, when the film is used in applications requiring transparency in particular. The lower limit of the haze value (Hz 0) is not particularly limited, and may be, for example, about 0.1.

The film of the present invention preferably satisfies the following formula (2) as an index of excellent electrolyte resistance.

(HzY) - (Hz 0) < 3.0 … (2)

HzY: after Hz0 was measured, the haze value measured in the same manner as Hz0 was used after 24 hours at a temperature of 23 ℃ and a humidity of 50% rh in a state where an electrolyte solution shown below was attached to the protective layer.

The electrolyte is used: liPF is blended in a mixed solution containing ethylene carbonate/diethyl carbonate/methylethyl carbonate=1:1:1 (volume ratio) ₆ And diluting the obtained liquid to a concentration of 1 mol/L. 10ml of the electrolyte was dropped onto the protective layer side to attach the electrolyte thereto, and the solution was left to stand at a temperature of 23℃and a humidity of 50% RH for 24 hours. Then, the electricity on the protective layer is wiped off by gauzeSolution was removed and Hz0 was measured.

In this way, the haze value before the electrolyte was dropped was set to Hz0, and the haze value measured after the electrolyte was left for 24 hours after the electrolyte was dropped was set to HzY.

The value of the above formula (2) is usually less than 3, particularly preferably 2.6 or less, further more preferably 2 or less, still more preferably 1.8 or less, and most preferably 1 or less. The lower limit of the value is not particularly limited, and may be, for example, about 0.1.

In this way, the film of the present invention satisfying the above formula (1) or the above formulae (1) to (2) can more reliably exhibit excellent electrolyte resistance. That is, there was little change in haze after 12 hours of standing after the electrolyte was attached, and there was little change in haze after 24 hours of standing. This may be expected to be: even if left for a long time in a state where the electrolyte is adhered, the change in haze before and after the adhesion is effectively suppressed, and the change in appearance or the decrease in the degree of elongation is also effectively suppressed.

2. Production of polyamide-based laminated film

The film of the present invention can be suitably produced by a method for producing a polyamide-based laminated film comprising the steps of:

(1) A step of applying a coating liquid for forming a protective layer, which contains a copolymerized polyester resin containing a dicarboxylic acid component and a diol component as constituent components, to an unstretched polyamide-based film or a uniaxially stretched polyamide-based film, wherein the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of the constituent units derived from the dicarboxylic acid (application step); and

(2) And a step (stretching step) of stretching the polyamide-based film having the coating film obtained by the coating to obtain a polyamide-based laminated film having a protective layer formed on one or both sides of the biaxially stretched film stretched in the MD and TD directions.

In the production of the film of the present invention, the method for forming the protective layer is not limited, and any method such as an in-line coating method, a post-coating method, or the like may be employed.

In particular, in the present invention, an inline coating method is preferably employed. Namely, the following method is preferably employed: an unstretched film or a uniaxially stretched film on which a coating film based on a coating liquid for forming a protective layer has been formed is stretched together with the aforementioned coating film. Accordingly, a production method including the above-described coating method and stretching method can be suitably employed. In the present invention, by employing the in-line coating method, the protective layer can be smoothed as compared with the post-coating method, and as a result, the protective layer can be formed thinly and uniformly. In addition, as described above, the electrolyte resistance of the protective layer containing the copolyester resin is also improved.

In the production method of the present invention, the order of the coating step and the stretching step is not particularly limited as long as the steps are provided. For example, 1) a method of applying a coating liquid for forming a protective layer to an unstretched polyamide film and then simultaneously or successively biaxially stretching the film can be used; 2) In the sequential biaxial stretching method, a coating liquid for forming a protective layer is applied to a uniaxially stretched polyamide-based film, and then the film is stretched in a direction (MD direction or TD direction) orthogonal to the uniaxial direction. The respective steps are specifically described below.

Coating process

In the coating step, a coating liquid for forming a protective layer (the coating liquid of the present invention) containing a copolyester resin (a copolyester resin a) containing a dicarboxylic acid component and a diol component as constituent components and having 50 mol% or more of a dicarboxylic acid component having a naphthalene skeleton in 100 mol% of a constituent unit derived from a dicarboxylic acid is coated on one side or both sides of an unstretched polyamide-based film or a uniaxially stretched polyamide-based film.

In this case, the unstretched polyamide-based film or the uniaxially stretched polyamide-based film may be the polyamide-based film base material of the film of the present invention, and a film produced by a known method may be used in addition to the known film itself.

For example, an unstretched polyamide-based film can be obtained by molding a melt-kneaded product containing a polyamide-based resin into a film shape. The melt-kneaded product may be prepared by a known method. For example, the resin composition may be produced by molding a melt-kneaded product obtained by melting a resin composition containing a polyamide resin into a film shape. This can be done by using known or commercially available devices. For example, a melt extruder with a T-die may be used. That is, a starting material (for example, a granular raw material) is first fed into a hopper, plasticized and melted in a melt extruder, and the melt-kneaded product is extruded into a sheet form from a T die attached to the front end of the extruder, and cooled and solidified by a casting roll. In this case, the melt-kneaded product may be pressed against a casting roll by air to obtain an unstretched film.

The resin composition may contain various additives, as required, in addition to the polyamide resin. Examples of the additive include additives added to a polyamide-based film substrate.

As the uniaxially stretched polyamide-based film, for example, a film obtained by uniaxially stretching the above-mentioned unstretched polyamide-based film can be used.

The coating liquid of the present invention contains a copolymerized polyester resin containing a dicarboxylic acid component and a diol component as constituent components, and the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more in 100 mol% of the dicarboxylic acid component. Such a copolymerized polyester resin may use the resins mentioned in the foregoing.

The method for producing the coating liquid of the present invention can be carried out by dissolving or dispersing the copolyester resin A in a solvent. That is, the coating liquid of the present invention can be prepared in the form of a solution or a dispersion.

The solvent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, and isopropanol, in addition to water; cellosolve such as butyl cellosolve; organic solvents such as toluene, methyl Ethyl Ketone (MEK), cyclohexanone, solvosiso, isophorone, xylene, methyl isobutyl ketone (MIBK), ethyl acetate, propyl acetate, butyl acetate, and isobutyl acetate. These may be used in an amount of 1 or 2 or more. In the present invention, it is preferable to use a) water or b) a mixed solvent of water and a water-soluble organic solvent. That is, from the viewpoint of workability, environment, and the like, it is preferable that the coating liquid for forming a protective layer is an aqueous coating agent containing water as a main component and is water-soluble or an aqueous dispersion, and from the viewpoint of coatability, it is more preferable that it is an aqueous dispersion. In this case, the crosslinking agent is also preferably an aqueous crosslinking agent. For the purpose of shortening the drying step and improving the stability of the coating liquid, an organic solvent such as alcohol may be contained in a small amount.

The concentration of the copolyester resin A in the coating liquid of the present invention may be appropriately set depending on the type of the copolyester resin used, and is usually about 3 to 40% by mass, and particularly preferably 5 to 20% by mass.

The coating liquid of the present invention may contain other components in addition to the copolyester resin A within a range that does not impair the effects of the present invention. For example, various additives as exemplified above may be blended.

The solid content concentration of the coating liquid for forming a protective layer containing a copolyester resin used in the present invention is preferably appropriately adjusted according to the standards of a coating apparatus and a drying/heat treatment apparatus. However, too thin a coating liquid is difficult to form a protective layer having a thickness sufficient to exhibit resistance to an acidic liquid such as an electrolyte, and in addition, a problem of requiring a long time is likely to occur in a subsequent drying process. On the other hand, a coating liquid having an excessively high concentration is less likely to be uniform, and problems in coating properties are likely to occur. From such a viewpoint, the solid content concentration of the coating liquid for forming the protective layer is preferably about 5 to 70% by mass, but is not limited thereto.

The coating liquid for forming a protective layer containing a copolyester resin used in the present invention may be prepared by a known method using a melting furnace (Japanese: dissolution vessel) equipped with a stirrer or the like.

The method of coating using the coating liquid of the present invention is not particularly limited, and a known method can be suitably used. For example, a gravure roll coating method, a reverse roll coating method, a wire bar coating method, an air knife coating method, a curtain coating method, a doctor blade coating method, a die coating method, a dip coating method, a bar coating method, or the like may be used, and a method in which these methods are combined may also be used.

After the application of the coating liquid of the present invention, the solvent may be removed by drying as needed, but may be supplied to the stretching step in the state of a liquid film or a semi-dried film before drying.

The drying step after the coating is not particularly limited, and may be performed by a known method such as a drying treatment in a drying atmosphere such as an oven, a drying treatment performed in contact with a hot roll, a drying treatment in a stretching machine, or the like. The drying temperature is not particularly limited, and may be set in a range of about 30 to 160 ℃. The drying time may be appropriately set according to the drying temperature, and is generally set in the range of 0.5 to 10 minutes.

Stretching step

After the coating step, the polyamide-based film having the coating film obtained by the coating is stretched to obtain a polyamide-based laminated film having a protective layer formed on one or both sides of the biaxially stretched film stretched in the MD direction and the TD direction.

Before the stretching step, the unstretched film or the uniaxially stretched film is preferably preheated. The preheating temperature is not limited, and is usually 180 to 250 ℃, particularly preferably 200 to 245 ℃, and particularly preferably 210 to 240 ℃. By preheating, a biaxially stretched film having good physical properties can be obtained more reliably. The preheating time depends on the preheating temperature and the like, but is preferably about 0.5 to 5 seconds.

The method for performing the preheating is not particularly limited. For example, it may be appropriate to employ: the method is carried out by setting the temperature of hot air blown to the film passing through the preheating zone of the stretching machine to the above-mentioned temperature range.

The stretching temperature is not limited to the above temperature, and is preferably set in the above temperature range by the temperature of hot air blown to the film passing through the stretching zone of the stretching machine. In this case, the time for the polyamide-based film to pass through the stretching zone is usually preferably about 0.5 to 5 seconds.

As the stretching method, since the biaxially stretched film of the present invention is finally obtained, a simultaneous biaxial stretching method or a sequential biaxial stretching method may be employed. Further, as the classification by the stretching apparatus, for example, a tube method, a tenter method, or the like can be used. In the present invention, the stretching method by the tenter method is preferable in particular in terms of quality stability and dimensional stability. Therefore, a tenter simultaneous biaxial stretching method or a tenter sequential biaxial stretching method can be suitably employed.

In the case of using the sequential biaxial stretching method as the stretching method, the film of the present invention in which the protective layer is formed on a predetermined biaxially stretched film can be obtained by applying the coating liquid for forming the protective layer to the film uniaxially stretched in the MD direction or the TD direction in advance and then stretching the film in the direction (TD direction or MD direction) orthogonal to the uniaxial direction.

The stretching ratio is not particularly limited, and it is usually about 2.0 to 4.5 times stretching in the MD direction and the TD direction. In this case, the stretch ratios in the MD direction and the TD direction may be the same or different from each other. In this way, a stretched film having excellent physical properties such as tensile strength and tensile elongation can be obtained.

The stretching temperature is not limited, and may be appropriately set in a range of 220℃or lower depending on the stretching method, the use of the film of the present invention, the use form, and the like.

For example, in the sequential biaxial stretching method, an unstretched film is first stretched in a uniaxial direction at a stretching temperature of 40 to 80 ℃ (preferably 50 to 65 ℃), and then a coating liquid for forming a protective layer is applied. The uniaxially stretched film coated with the coating liquid for forming a protective layer may be dried at 50 to 220 ℃ in the same manner as the simultaneous biaxial stretching method described above. Thereafter, the uniaxially stretched film coated with the coating liquid for forming a protective layer is stretched in the orthogonal direction at a stretching temperature of 200 ℃ or less (preferably 90 to 190 ℃) to obtain a biaxially stretched film. In the case of performing the sequential biaxial stretching, it is preferable to perform the stretching by a combination of a roll stretching method and a tenter stretching method. That is, after stretching in a uniaxial direction (TD direction or MD direction) by a roll (usually, a device that stretches while passing through 2 or more rolls), biaxial stretching may be performed by stretching in a direction (TD direction or MD direction) substantially perpendicular to the uniaxial direction by tentering.

In the simultaneous biaxial stretching method, for example, it is preferable that the unstretched film coated with the coating liquid for forming a protective layer is simultaneously biaxially stretched at a stretching temperature of 215 ℃ or less (preferably 190 to 210 ℃) after being dried at 50 to 220 ℃ in the drying step. When the unstretched film is biaxially stretched simultaneously, it is preferably stretched by a tenter method, a LISIM biaxial stretching method or the like.

The stretched film in the stretching process is preferably further subjected to a heat treatment. The heat treatment temperature is not particularly limited, but is usually preferably about 190 to 220 ℃, and more preferably 195 to 215 ℃. If the heat treatment temperature is less than 190 ℃, the formation of the coating film of the copolyester resin may be insufficient, and a protective layer having insufficient resistance to the electrolyte may be formed. In addition, when a curing agent is added, the crosslinking reaction may not proceed sufficiently, and the effect of adding the crosslinking agent may not be obtained. On the other hand, if the heat treatment temperature exceeds 220 ℃, the strength of the polyamide film may be lowered. In the case where the crosslinking reaction is not sufficiently performed in the heat treatment, the aging treatment may be performed after the completion of the stretching. The time of the heat treatment may be appropriately set depending on the heat treatment temperature and the like, and is preferably about 1 to 15 seconds in general.

The heat treatment method is not particularly limited, and for example, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, and the like can be employed. Among them, a method of blowing hot air is preferable from the viewpoint of being heated uniformly and with good precision. For example, the heat setting treatment may be performed by blowing hot air, which has been set in the above temperature range, to the film passing through the heat setting zone of the stretching machine.

Other procedures

The method of stacking the layers is not particularly limited, and for example, any of the following methods may be employed: the method comprises the following steps: a) a method of forming a coating film obtained by using a coating liquid, b) a method of laminating a preformed film, c) a method of forming a vapor deposition film by PVD method, CVD method, or the like. In the case of b), any of a method of laminating via an adhesive, a method of laminating by simultaneous extrusion molding, and the like may be employed. In particular, when the film of the present invention is used for a battery exterior material such as a lithium ion secondary battery, a known method for producing the exterior material may be used. In this case, the lamination may be performed using a known adhesive.

For example, in the case of lamination with a barrier layer, the following method can be adopted: and a method of dry lamination, thermal lamination, or the like of a laminate comprising a protective layer/polyamide film substrate, a laminate comprising a protective layer/polyamide film substrate/protective layer, a metal foil for forming a barrier layer, or the like via a two-component urethane adhesive or the like.

In addition, as a method of joining the barrier layer and the heat fusion layer, a known method (dry lamination, heat lamination, extrusion lamination, sandwich lamination, or the like) can be used.

On the surfaces of the polyamide film, the barrier layer, and the heat fusion layer on which the adhesive layer is to be formed, other layers such as an anchor coat layer and a primer layer may be provided as needed as long as the effect of the present invention is not impaired.

3. Use of polyamide-based laminated film

The films of the present invention are useful in a variety of applications, and are particularly useful as packaging materials. That is, it is available as a packaging material for packaging the contents. The content is not limited, and may be packaged, for example, in electronic parts, chemical products, cosmetics, medical supplies (medical devices), drinks and foods, and the like.

In particular, the film of the present invention can be suitably used as an exterior material for lithium ion batteries, and in the case of using the film of the present invention as an exterior material, the film of the present invention (particularly, a polyamide-based base material layer) can be protected from the electrolytic solution by the protective layer. As a result, problems due to corrosion of the exterior material or the like can be effectively suppressed or prevented.

In general, an electrolyte used for a lithium ion secondary battery is a conductive liquid prepared by dissolving an ionic substance (particularly, a lithium salt) in a polar solvent such as carbonate. The lithium salt may be a lithium salt that generates hydrofluoric acid (hydrogen fluoride) by reaction with water. More specifically, there can be exemplified: lithium hexafluorophosphate (LiPF) ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) And fluorine-containing lithium salts. Therefore, when the electrolyte adheres to the air, the moisture in the air and the fluorine contained in the electrolyteThe lithium salt reacts to produce hydrofluoric acid. The hydrofluoric acid may dissolve a polyamide film used for a lithium ion secondary battery exterior material. In contrast, in the film of the present invention, since the polyamide-based base material layer is covered with the specific protective layer, even if the electrolyte contacts the exterior material (particularly, the protective layer), the exterior material can be effectively protected with high electrolyte resistance, and as a result, a highly reliable lithium ion secondary battery can be provided. Therefore, the film of the present invention can be suitably used as, for example, a lithium ion secondary battery exterior material, and can also be applied to an embossed or deep-drawn lithium ion secondary battery. In addition, in the case of manufacturing a lithium ion secondary battery, even if an electrolyte adheres to the exterior material, the performance as the exterior material of the lithium ion secondary battery can be well maintained.

In the case of using as a packaging material, the form thereof is not particularly limited, and for example, it can be used as a packaging bag or a packaging container. The packaging bag can be used as various bag bodies such as a pillow bag, an accessory bag, and a stand bag. The method of forming the bag body may be carried out according to a known method.

The present invention also includes a product (packaged product) in which the content is packaged by the above-described packaging material or packaging bag. The packaging state in this case includes, for example: a state in which the content is sealed from the outside by a packaging material or a packaging bag, and the like.

4. Battery cell

The present invention includes a battery, characterized by comprising: a power generation element including a negative electrode, a positive electrode, a separator, and an electrolyte; and an exterior material for packaging the power generation element; the exterior material is the film of the present invention, and the protective layer is disposed as the outermost layer of the battery.

The film of the present invention may be suitably used for a laminate type (pouch type) battery, depending on the packaging form of the battery, which may be classified into a can type and a laminate type (pouch type). For this reason, in addition to a method of filling and sealing the power generating element after the film of the present invention is formed into a concave shape (container shape), a method of sealing the power generating element by placing the power generating element on the film of the present invention and then forming the film of the present invention so as to wrap the film of the present invention in the film may be employed.

The power generation element is not particularly limited, and a known or commercially available power generation element may be used. The battery may be a primary battery or a secondary battery. Examples thereof include lithium ion batteries, nickel hydrogen batteries, nickel cadmium batteries, and the like.

A schematic of the battery is shown in fig. 4. The battery 40 has a structure in which the power generating element 41 is covered with an exterior material including the film 10 of the present invention. More specifically, the power generating element 41 is covered with the film 10 of the present invention so that the protective layer 10a surface of the film 10 of the present invention is outside.

The power generation element 41 in fig. 4 includes: a positive electrode including a positive electrode active material and a current collector, a separator, a negative electrode including a negative electrode active material and a current collector, an electrolyte, and the like (none of which are shown). The positive electrode and the negative electrode each have a lead (tab) 43 extending from an end.

As an example of the lithium ion battery, the following configuration can be adopted. Examples of the positive electrode active material include lithium salts such as lithium manganate, metallic lithium, and aluminum foil as examples of the positive electrode current collector. Examples of the separator include microporous films such as polyethylene and polypropylene. Examples of the negative electrode active material include graphite, lithium salts such as lithium manganate, metallic lithium, and aluminum foil. Examples of the electrolyte include lithium tetrafluoroborate (LiBF ₄ ) Lithium hexafluorophosphate (LiPF) ₆ ) And lithium salts are dissolved in Ethyl Carbonate (EC), ethyl Methyl Carbonate (EMC), propylene carbonate, and the like.

Fig. 5 is a cross-sectional view showing an example of an embodiment of a battery using the film body of the present invention as an exterior material. In the battery 50, the film 10 of the present invention as an exterior material is folded in half so that the protective layer 10a is positioned outside, and the power generation element 41 is mounted therein. The surface of the film 10 of the present invention on the opposite side of the protective layer is a heat-sealed layer surface 10b, and the adhesive portion S1 is formed by heat sealing in a state where the end portions thereof are opposed to each other. In the bonding portion S1, the lead 43 is sandwiched between the heat fusion layers. In fig. 4, only 1 lead 43 is shown for simplicity, but a positive electrode lead and a negative electrode lead are actually provided.

In assembling the battery shown in fig. 5, the power generation element 41 including the lead 43 is covered with the film 10 of the present invention so that the lead is exposed to the outside. In the coating, the power generating element 41 is coated by bonding the heat fusion bonding layers 10b of the film 10 of the present invention to each other. In this case, a part is not joined to ensure the injection port of the electrolyte. Next, after the electrolyte is filled from the inlet, the inlet is sealed by heat sealing. In this way, the power generating element 41 is sealed by the film 10 of the present invention as the exterior material.

Fig. 6 is a schematic view showing a cross section of a battery according to another embodiment. The battery 60 has a power generating element (power generating element) 41 for connecting to an external lead 43, and the periphery thereof is covered with 2 sheets of the films 10, 10 of the present invention. Both ends of the films 10, 10 of the present invention are sealed with adhesive portions S1, S2 obtained by heat sealing or the like. The lead wire 43 extends so as to be exposed to the outside from the electrode in the battery 60, and can draw out the current from the power generation element 41 to the outside. In fig. 6, only 1 lead 43 is shown for simplicity, but a positive electrode lead and a negative electrode lead are actually provided.

When the battery 60 shown in fig. 6 is assembled, the power generating element 41 is covered with the films 10 and 10 of the present invention so that the lead 43 is exposed to the outside with respect to the power generating element 41 provided with the lead 43. In the coating, the power generating element 41 is coated by bonding the heat-seal layers 10b, 10b of the 2 sheets of the films 10, 10 of the present invention to each other by heat sealing. In this case, a part is not joined to ensure the injection port of the electrolyte. Next, after the electrolyte is filled from the inlet, the inlet is sealed by heat sealing. In this way, the sealing of the power generating element 41 was performed by using 2 sheets of the films 10 and 10 of the present invention.

Examples

The following examples and comparative examples illustrate the features of the present invention in more detail. However, the scope of the present invention is not limited by the examples. The term "parts" as used hereinafter means "parts by mass".

Example 1

(1) Synthesis of copolyester resin A

The dicarboxylic acid component (709.4 parts of 2, 6-naphthalene dicarboxylic acid, 26.6 parts of terephthalic acid, 56.2 parts of isophthalic acid-5-sodium sulfonate), the diol component (176.7 parts of ethylene glycol, 126.2 parts of diethylene glycol, 336.8 parts of 1, 6-hexanediol), and 0.26 part of tetrabutyl titanate as a polymerization catalyst were charged into a reactor, and the inside of the system was replaced with nitrogen gas. Then, the reactor was warmed to 200℃while stirring the raw materials at 1000 rpm.

Then, the temperature was gradually raised to 260℃over 4 hours and subjected to transesterification. Thereafter, the pressure was gradually reduced at 250℃and the polycondensation reaction was carried out at 0.35mmHg for 1.5 hours. In this way, a prescribed copolyester resin was prepared.

(2) Preparation of coating liquid for Forming protective layer

The obtained copolyester resin was finely pulverized, 30 parts of the copolyester resin and 70 parts of water were added to a dissolution tank, and stirred at 80 to 95 ℃ while taking 2 hours to dissolve, thereby obtaining an aqueous solution having a concentration of 30 mass% as a coating liquid for forming a protective layer.

(3) Production of stretched film (Simultaneous biaxial stretching)

A polyamide resin (nylon 6, unitika corporation "A1030BRF", relative viscosity 3.1) was extruded into a sheet form through a T die using an extruder equipped with a T die at 260 ℃. Then, the resultant film was brought into close contact with a casting roll whose surface temperature was adjusted to 18℃to rapidly cool the film, and the supply amount of the polyamide resin was adjusted so that the thickness of the stretched polyamide film became 15. Mu.m.

Subsequently, the unstretched film was passed through a water absorption treatment apparatus at a water temperature of 50℃to apply the coating liquid for forming a protective layer to one side of the unstretched film by a spray method so that the thickness after drying became 0.70. Mu.m, and the film was dried at 150℃and then introduced into a simultaneous biaxial stretching machine. The coated, unstretched film was simultaneously biaxially stretched 3.0 times in the MD and 3.3 times in the TD in a simultaneous biaxial stretching machine at a preheating temperature of 200℃and a stretching temperature of 190 ℃. Then, a heat treatment was performed at a heat treatment temperature of 210℃for 3 seconds to form a protective layer on one surface of the polyamide film. Further, the other surface having no protective layer was subjected to corona treatment, and thus a stretched film having a film thickness of 15 μm and a protective layer thickness of 0.70 μm was obtained.

(4) Production of polyamide-based laminated film

The coating amount of the resultant stretched film was 5g/m on the surface where no protective layer was laminated ² A two-component polyurethane adhesive (TM-K55/CAT-10L, manufactured by Toyo Morton Co., ltd.) was applied and dried at 80℃for 10 seconds. An aluminum foil (thickness: 50 μm) was bonded to the adhesive-coated surface. Then, the adhesive was applied to the aluminum foil surface under the same conditions, dried, and an unstretched polypropylene film (GHC, manufactured by Mitsui Chemicals Tohcello Co., ltd., thickness: 50 μm) was bonded as a heat-seal layer, followed by aging treatment at 40℃for 72 hours. Thus, a polyamide-based laminated film was obtained in which the layers were laminated in the order of "protective layer/polyamide film/aluminum foil/heat-seal layer".

Examples 2 to 19 and comparative examples 1 to 6

A polyamide-based laminated film was produced in the same manner as in example 1, except for the conditions shown in table 1 and below. Table 1 shows an example using the post-coating method.

TABLE 1

< example 2>

(2) Preparation of coating liquid for Forming protective layer

Using the copolyester resin described in example 1 and the oxazoline-based crosslinking agent (WS 300 manufactured by japan catalyst corporation) described in table 1, the coating liquid for forming a protective layer was obtained by adding the mixture of the copolyester resin and the crosslinking agent so that the crosslinking agent content was 5 mass% relative to the solid content of the copolyester resin, and further mixing the mixture with pure water so that the solid content of the mixture of the copolyester resin and the crosslinking agent became 9 mass%.

(3) Production of stretched film (Simultaneous biaxial stretching)

A stretched film was obtained in the same manner as in example 1, except that the heat treatment temperature at the time of forming the protective layer on one side of the polyamide film was changed to the values shown in table 1.

< example 5>

(1) Synthesis of copolyester resin A

A copolyester resin was obtained by polymerization in the same manner as in example 1, except that the blending ratio of the dicarboxylic acid component to the diol component was changed to the composition shown in table 1.

(2) Preparation of coating liquid for Forming protective layer

Under the conditions shown in table 1, a crosslinking agent was added to the above-mentioned copolyester resin, and 9 mass% of a coating liquid for forming a protective layer was obtained using pure water.

(3) Production of stretched film (successive biaxial stretching)

Polyamide resin (nylon 6, manufactured by unitka corporation, a1030BRF, relative viscosity 2.7) was extruded into a sheet form at 260 ℃ through a T-die using an extruder equipped with a T-die. Then, the resultant was brought into close contact with a casting roll whose surface temperature was adjusted to 18℃to rapidly cool the film, and the supply amount of the polyamide resin was adjusted so that the thickness of the polyamide film obtained after stretching became 15. Mu.m.

Then, the unstretched film is stretched in the MD direction by passing it through a stretching roller heated to 54 to 62℃to a stretch ratio of 2.80. Next, the protective layer forming coating liquid was applied to one side of the stretched film by using a gravure coater so that the thickness after drying became 0.70 μm, and stretched in the TD direction to a stretching ratio of 3.2 times at a preheating temperature of 60 ℃ and a stretching temperature of 90 ℃. Further, the heat treatment was performed at a heat treatment temperature of 215℃for 3 seconds. The surface of the polyamide film without the protective layer is further subjected to corona treatment. Thus, a stretched film having a film thickness of 15 μm and a protective layer thickness of 0.70 μm was obtained.

< example 6>

A polyamide-based laminated film was produced in the same manner as in example 5, except that the heat treatment temperature was changed as shown in table 1.

< examples 3 to 4, 9, 16 to 18, comparative example 2>

A polyamide-based laminated film was obtained in the same manner as in example 2, except that the composition of the coating liquid for forming a protective layer and the heat treatment temperature at the time of forming a protective layer were set to the conditions shown in table 1.

< examples 6 to 8 and 10 to 15>

A polyamide-based laminated film was obtained in the same manner as in example 5, except that the composition of the coating liquid for forming a protective layer and the heat treatment temperature at the time of forming a protective layer were set to the conditions shown in table 1.

< example 19>

(3) Production of stretched film (Simultaneous biaxial stretching)

Then, the unstretched film was passed through a water absorption treatment apparatus having a water temperature of 50℃and then introduced into a simultaneous biaxial stretching machine, and simultaneously biaxially stretched at a preheating temperature of 200℃and a stretching temperature of 190℃in the MD direction of 3.0 times and in the TD direction of 3.3 times. Next, the heat treatment was performed at a heat treatment temperature of 210℃for 3 seconds. Then, corona treatment is performed on one surface. Thus, a stretched film having a film thickness of 15 μm was obtained.

Further, the obtained stretched film was introduced into a gravure coater, and the coating liquid for forming a protective layer obtained in example 2 was applied so that the final coating thickness became 0.7 μm, and passed through a 5-zone drying oven [ zone 1 (80 ℃ C.) →zone 2 (100 ℃ C.) →zone 3 (120 ℃ C.) →zone 4 (110 ℃ C.) →zone 5 (80 ℃ C.) ] for 3 seconds to dry, thereby obtaining a stretched film having a film thickness of 15 μm and a protective layer thickness of 0.70 μm.

< comparative example 1>

A polyamide-based laminated film was obtained in the same manner as in example 19, except that the composition of the coating liquid for forming a protective layer was set as shown in table 1 and the thickness of the protective layer was set to 2.00 μm.

< comparative example 3>

A polyamide-based laminated film was obtained in the same manner as in comparative example 1, except that the coating liquid for forming a protective layer was changed to a commercially available PVDC coating liquid (Saran Latex L549, asahi chemical Co., ltd.).

< comparative example 4>

A polyamide-based laminated film was obtained in the same manner as in example 1, except that the coating liquid for forming a protective layer was changed to the same PVDC coating liquid as in comparative example 3, and the heat treatment temperature at the time of forming a protective layer was changed.

< comparative example 5>

A polyamide-based laminated film was obtained in the same manner as in comparative example 1, except that the coating liquid for forming a protective layer was changed to a saturated polyester resin emulsion (high rosin oil Co., ltd., A-110F).

< comparative example 6>

A polyamide-based laminated film was obtained in the same manner as in example 1, except that the coating liquid for forming a protective layer was changed to the same saturated polyester resin emulsion as in comparative example 5, and the heat treatment temperature at the time of forming a protective layer was changed.

Test example 1

The following characteristics were measured for the polyamide-based laminated films obtained in each of the examples and comparative examples. The results are shown in Table 2. The "no measurement" in table 2 indicates that wrinkles or the like occur after the electrolyte adheres, and the surface of the polyamide-based laminated film is deformed, and thus cannot be measured.

(1) Composition of the copolyester resin

Measurement Using "ECZ400R type NMR apparatus" manufactured by Japanese electronics Co., ltd ¹ H-NMR was obtained from the peak integrated intensity ratio of protons of each copolymer component of the obtained chart.

(2) Glass transition temperature of the copolyester resin

The measurement was performed at a temperature rise rate of 20℃per minute using a differential scanning calorimeter (Diamond DSC) manufactured by Perkin Elmer.

(3) Thickness of protective layer

The polyamide-based laminate film obtained was embedded with an epoxy resin, and then subjected to a planarization process (Japanese (face-out) and then to RuO ₄ Stained (1 day) and sections with a thickness of 90nm (set point) were collected using an microtome. The cutting temperature was set to 23℃and the humidity was 50% RH (sample circumference, knife, chamber) and the cutting speed was set to 0.6mm/min. The obtained sample was subjected to transmission measurement using a "JEM-1230" TEM, manufactured by Japanese electronic Co., ltd, and the thickness of the protective layer was measured at an acceleration voltage of 100 kV.

(4) Non-uniform thickness of laminated film (thickness accuracy)

As shown in fig. 3, the obtained polyamide-based laminated film was subjected to humidity control at a temperature of 23 ℃ and a humidity of 50% rh for 2 hours, and after a reference direction (0 degree direction) was designated with respect to an arbitrary point a on the film, 8 directions such as 45 degree direction, 90 degree direction, 135 degree direction, 180 degree direction, 225 degree direction, 270 degree direction, 315 degree direction, etc. rotated clockwise from the reference direction toward the reference direction from the center point a were drawn into a total of 8 straight lines of 100mm, respectively. The thickness was measured (10 points were measured) at 10mm intervals from the center point a on each straight line using a length meter "HEIDENHAIN-METRO MT1287" (manufactured by Heidenhain corporation), the average value of the measured values of the data measured in all straight lines was calculated for 80 points in total, and the standard deviation value with respect to the average thickness was calculated with this as the average thickness. The reference direction is not particularly limited, and may be, for example, MD in the stretching step at the time of film production.

(5) Surface roughness

The surface roughness of the protective layer and the base material surface of the polyamide-based laminated film obtained was measured at 10 points by using a contact surface roughness measuring device "suefcordier SE500A" manufactured by the institute of small ban, inc. According to japanese industrial standard "JIS B0601-2013", and the calculated average value was set as Ra.

(6) Electrolyte resistance

The resulting polyamide-based laminated film was used to evaluate electrolyte resistance for 3 sets of time periods of 6 hours, 12 hours and 24 hours as shown below.

First, the haze value of the obtained polyamide-based laminated film was measured according to japanese industrial standard "JIS K7136" using a haze meter (NDH 4000) manufactured by japan electric color corporation. This was set to the haze (Hz 0) before dropping of the electrolyte solution.

Next, 3 samples were prepared in which the opening of the glass shallow chassis (diameter: 200 mm) was covered with a polyamide-based laminated film so that the protective layer was the surface. In each sample, 10ml of an electrolytic solution was dropped onto the protective layer (LiPF was blended in a mixed solution containing ethylene carbonate/diethyl carbonate/methylethyl carbonate=1/1/1 (volume ratio) ₆ And diluted to a concentration of 1 mol/L), the electrolyte is attached to the protective layer.

Of the 3 samples, 3 samples were prepared in which the holding time at a temperature of 23℃and a humidity of 50% RH was set to 6 hours, 12 hours and 24 hours after the electrolyte was adhered. For the 3 samples, after leaving for each time, the electrolytic solution on the protective layer was wiped off with gauze, and measurement was performed in the same manner as described above using a haze meter (NDH 4000) manufactured by japan electric color company according to japanese industrial standard "JIS K7136".

The haze value measured after the electrolyte was attached and left at a temperature of 23℃and a humidity of 50% RH for 6 hours was HzW, the haze value measured after left for 12 hours was HzX, and the haze value measured after left for 24 hours was HzY.

Then, the difference between each of them and Hz0 before the electrolyte was dropped was calculated, (HzW) - (Hz 0), (HzX) - (Hz 0), (HzY) - (Hz 0).

In the above calculation results, the value according to the practicality is less than 3.0, particularly preferably less than 2.0, and even more preferably less than 1.0.

(7) Wetting

Wetting was measured according to Japanese Industrial Standard "JIS K6768". When the measured value was 42dyn or more, it was evaluated as good.

(8) Blocking resistance

The resulting polyamide-based laminate film was laminated (when the protective layer was one-sided, the protective layer was laminated with the base material layer, and when the protective layer was double-sided, the protective layer was laminated with the protective layer) and placed 300g/cm ² In the state of the weight, the mixture was left to stand in a constant temperature bath at a temperature of 40℃and a humidity of 50% RH for 24 hours. Thereafter, the sample was cut into strips 15mm wide by 100mm long, and peeled off at a speed of 200mm/min using a tensile tester Autograph AG-I (manufactured by Shimadzu corporation), and the highest value was defined as the peel strength value. Regarding the peel strength value, 50g/15mm or less was evaluated as blocking resistance ". O", more than 50g/15mm and less than 80g/15mm was evaluated as blocking resistance ". DELTA.", and 80g/15mm or more was evaluated as blocking resistance ". X". In terms of practicality, it is necessary to be blocking resistance ". DELTA.or more.

TABLE 2

The polyamide-based laminated films obtained in examples 1 to 19 were excellent in electrolyte resistance and blocking resistance, since the protective layer contained the copolyester resin having the composition defined in the present invention and had a thickness of 1.5 μm or less, even if the electrolyte was adhered to the protective layer, the appearance of the polyamide film was not changed for at least 12 hours. In particular, the protective layer containing a dicarboxylic acid component having a naphthalene skeleton in an amount of 80 mol% or more, a glass transition temperature of 80 ℃ or more, and a crosslinking agent is excellent in electrolyte resistance.

On the other hand, the polyamide-based laminated films obtained in comparative examples 1, 3 and 5 were poor in blocking resistance because they were not sufficiently dried in a drying step of 3 seconds or so, although they exhibited electrolyte resistance, due to the thick protective layer.

In comparative examples 2, 4 and 6, since the protective layer composition was not defined in the present invention, when the protective layer thickness was as small as 1.50 μm or less, sufficient electrolyte resistance could not be obtained, and when the electrolyte was adhered to the protective layer, the polyamide-based laminated film whitened, and the appearance was greatly impaired. In comparative example 5, even when the protective layer is thick, the polyamide-based laminated film is whitened, and the appearance is largely impaired.

Claims

(3) The protective layer contains a copolymerized polyester resin which contains a dicarboxylic acid component and a diol component as constituent components, and contains 50 mol% or more of (a) a dicarboxylic acid component having a naphthalene skeleton and 5 to 45 mol% of (b) terephthalic acid in 100 mol% of constituent units derived from a dicarboxylic acid; and

(4) The thickness of the protective layer is 1.5 μm or less, and the surface roughness Ra of the protective layer is 45nm or less.

2. The polyamide-based laminated film according to claim 1, which satisfies the following formula (1):

(HzX) - (Hz 0) < 3.0 … (1)

And Hz0 is in the range of 10 or less,

in the formula (1), hz0 is a haze value measured in accordance with JIS K7136, the HzX is a haze value measured in the same manner as Hz0 after being held at a temperature of 23 ℃ and a humidity of 50% rh for 12 hours in a state in which an electrolyte is attached to a protective layer after measuring Hz0, the electrolyte is a composition comprising a volume ratio of 1:1:1 in a mixture of ethylene carbonate/diethyl carbonate/ethylmethyl carbonate ₆ Diluted to a concentration of 1 mole/L.

3. The polyamide-based laminate film according to claim 1, wherein the glass transition temperature of the copolyester resin is 60 to 145 ℃.

4. The polyamide-based laminate film as claimed in claim 1, wherein the protective layer further comprises at least 1 of a melamine resin, an isocyanate compound, a carbodiimide compound, and an oxazoline compound.

5. The polyamide-based laminated film according to any one of claims 1 to 4, wherein the polyamide-based laminated film is laminated such that the protective layer directly contacts at least one surface of the polyamide-based film base material, and is a laminate of:

(a) A laminate comprising a protective layer, a polyamide-based film substrate, a barrier layer, and a heat-sealing layer in this order; or (b)

(b) A laminate comprising a protective layer, a polyamide film base material, a protective layer, a barrier layer, and a heat-sealing layer in this order.

6. The polyamide-based laminated film according to any one of claims 1 to 4, which is used for packaging an article.

7. The polyamide-based laminated film according to claim 5, which is used for packaging an article.

8. A battery, comprising:

An exterior material for packaging the power generation element,

the exterior material is the polyamide-based laminated film according to any one of claims 1 to 5, and the protective layer is disposed as the outermost layer of the battery.

9. A process for producing the polyamide-based laminated film according to any one of claims 1 to 5, comprising:

(1) A step of applying a coating liquid for forming a protective layer, which contains a copolymerized polyester resin containing a dicarboxylic acid component and a diol component as constituent components, and containing 50 mol% or more of (a) a dicarboxylic acid component having a naphthalene skeleton and 5 to 45 mol% of (b) terephthalic acid, to 100 mol% of the dicarboxylic acid component, to an unstretched polyamide film or a uniaxially stretched polyamide film; and

(2) And stretching the polyamide film having the coating film obtained by the coating to obtain a polyamide laminated film having a protective layer formed on one or both sides of the biaxially stretched film stretched in the MD and TD directions.