JP2015107585A - Multilayer film, multilayer film package material, draw molded article, and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film that can sufficiently suppress spring back in cold molding and has excellent deep drawing moldability at the time of cold molding.SOLUTION: The multilayer film includes a nylon layer (ONy) comprising an oriented nylon film, an aluminum layer (Al), a polyolefin layer (PO), and a polyethylene terephthalate layer (PET), in an order of PET/ONy/Al/PO. In stress-strain curves in predetermined four directions of the multilayer film obtained by tension tests on the multilayer film, an elastic modulus is 1000 MPa or more and 2000 MPa or less in all of the four directions; a tensile stress σat a proportional limit is 20 MPa or more and 40 MPa or less in all of the four directions; and a stress ratio A (σ/σ), which is a ratio of a tensile stress σwhen a strain εis 0.5 to the tensile stress σat the proportional limit, is 2.5 or less in all of the four directions.

Description

  The present invention particularly relates to a multilayer film, a multilayer film packaging material, a draw-molded article, and a battery that can be suitably used as a packaging material for cold molding.

  In recent years, electronic devices have been reduced in size and thickness, and batteries used in these devices are similarly required to be reduced in size and thickness. Then, instead of the battery of the type sealed in the metal sealing cans so far, a multilayer film packaging material laminated in a layer configuration of biaxially stretched nylon film / adhesive layer / aluminum foil / adhesive layer / sealant layer There has been proposed a battery of a type that is cold-molded by using (for example, Patent Document 1).

JP 2002-216715 A

However, in cold forming, a phenomenon (spring back) that a part of a molded product returns from a shape after molding to a shape before molding after drawing is likely to be a problem. Such a springback may cause a problem that the dimensional accuracy of the shape after drawing is insufficient. And, in the multilayer film packaging material as described in Patent Document 1, although it is not a problem in normal cold forming, when the dimensional accuracy of the shape after cold forming is required at a very high level, There was a case that it could not cope with it.
Further, the packaging material for cold forming is required to further improve drawability (deep drawability) as the capacity of batteries and the like increases. However, in the multilayer film packaging material as described in Patent Document 1, there is no problem in ordinary drawing, but if deep drawing is performed, pinholes may be generated.

  Accordingly, the present invention provides a multilayer film, a multilayer film packaging material, a draw-molded product, and a battery that can sufficiently suppress spring back during cold forming and have excellent deep drawability during cold forming. The purpose is to do.

  In the present invention, cold molding refers to molding performed in a temperature atmosphere below the glass transition point (Tg) of the nylon layer constituting the multilayer film. One means of such cold forming is to use a cold forming machine used for forming aluminum foil or the like to push the sheet material into the female mold with a male mold and press it at high speed. According to such cold forming, plastic deformation such as molding, bending, shearing and drawing can be generated without heating.

The multilayer film of the present invention includes a nylon layer (hereinafter referred to as ONy), an aluminum layer (hereinafter referred to as Al), a polyolefin layer (hereinafter referred to as PO), and a polyethylene terephthalate layer (hereinafter referred to as “nylon 6”). , PET) in the order of PET / ONy / Al / PO, and the four directions in the tensile test (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) of the multilayer film In the stress-strain curve in the MD direction, TD direction, 45 ° direction and 135 ° direction of the stretched nylon film, the elastic modulus is 1000 MPa to 2000 MPa in all of the 4 directions, and the tensile stress σ at the proportional limit ₂ is 20 MPa or more and 40 MPa or less in all of the four directions, Stress ratio A (σ), which is the ratio of the tensile stress σ ₁ when the strain ε ₂ at break in the four directions is 0.5 (the elongation rate until break is 50%) and the tensile stress σ _{2 1} / σ ₂ ) is 2.5 or less in each of the four directions.

In the present invention, tensile in a tensile test stress - in strain curve, four directions of the elastic modulus 1000MPa or more 2000MPa or less, four directions of 40MPa tensile stress sigma ₂ to 20MPa or more at proportional limit or less, the strain at the time of the four directions at break epsilon ₂ 2.5 There 0.5 tensile stress sigma ₁ when (elongation to break of 50%) becomes, both the stress ratio a (σ ₁ / σ ₂₎ of the tensile stress sigma ₂ in proportional limit It is as follows.
For this reason, the spring back at the time of cold forming can be sufficiently suppressed, and a multi-layer film having excellent deep drawing formability without producing a pinhole at the time of cold forming can be obtained.

In the present invention, it is preferable that the stress ratio A (σ ₁ / σ ₂ ) is 1.5 or more in each of the four directions.
In the present invention, by setting the stress ratio A (σ ₁ / σ ₂ ) to 1.5 or more in four directions, spring back can be sufficiently suppressed, and excellent deep drawing without causing pinholes during cold forming Formability can be provided.

In the present invention, the ratio (A _max / A _min ) between the maximum stress ratio A _max and the minimum stress ratio A _min among the stress ratios A in the four directions is 1.2 or less. It is preferable that the configuration be
In this invention, when the ratio (A _max / A _min ) between the stress ratio A _max and the stress ratio A _min is 1.2 or less, the multilayer film stretches in a well-balanced manner during cold molding, and molding with a uniform thickness is achieved. Product can be manufactured.
Here, if the ratio (A _max / A _min ) exceeds 1.2, the uneven thickness is poor and the thickness is locally thinned, and the multilayer film may be broken.

Moreover, in this invention, it is preferable to set it as the structure whose tensile strength (sigma) ₃ at the time of the fracture | rupture about the said 4 directions in the said tensile test of the said multilayer film is all 55 MPa or more.
In this invention, sufficient tensile strength can be obtained by setting the tensile breaking strength σ ₃ in the four directions to 55 MPa or more, and the multilayer film is more difficult to break during cold forming.
Here, if any of the four-direction tensile breaking strengths σ ₃ is less than 55 MPa, the multilayer film tends to break during cold deep drawing, and good cold formability may not be obtained. There is.

Furthermore, in the present invention, it is preferable that the strain ε ₂ at the time of fracture is 0.7 or more in all the four directions.
In this invention, when the strain ε ₂ is 0.7 or more in four directions (the elongation rate until breaking in the four directions is 70% or more), the multilayer film stretches in a well-balanced and uniform thickness during cold forming. Can be manufactured.
Here, the strain epsilon ₂ is smaller than 0.7, the multilayer film when such deep drawing molding in cold tends to break, there is a possibility that good cold formability can not be obtained.

In the present invention, in the tensile stress-strain curve of the multilayer film in the tensile test, the tensile stress σ ₁ when the strain ε ₂ at break is 0.5 (elongation is 50%) is 4 It is preferable that the direction is 45 MPa or more.
In this invention, since the four directions of the tensile stress σ ₁ are all set to 45 MPa or more, the multilayer film can be stretched in a balanced manner during cold forming, and a molded product having a uniform thickness can be manufactured.

Furthermore, in the present invention, the PO is preferably a crystalline polypropylene layer.
In the present invention, by making PO a crystalline polypropylene layer, it is possible to provide a multilayer film that can be heat-sealed well and has heat resistance.

And in this invention, it is preferable to set it as the structure for cold forming.
In the present invention, even when applied to cold forming, spring back can be sufficiently suppressed, and excellent deep drawing can be performed without generating pinholes.

The multilayer film packaging material of the present invention is characterized by using the multilayer film of the present invention.
In the present invention, the spring back can be sufficiently suppressed during cold forming, and the multilayer film of the present invention having excellent deep drawability without causing pinholes is used, so that the dimensional accuracy is high and the shielding property is excellent. Can be provided as a packaging material.

The drawn article of the present invention is characterized in that the multilayer film of the present invention is drawn.
In the present invention, the spring back can be sufficiently suppressed during cold forming, and the multilayer film of the present invention having excellent deep drawability without causing pinholes is used, so that the dimensional accuracy is high and the shielding property is excellent. We can provide a drawn product.

The battery of the present invention includes the multilayer film of the present invention and a battery main body, wherein the multilayer film covers the battery main body and is used as an exterior material with the PET side as an outer surface side.
In the present invention, the spring back can be sufficiently suppressed during cold forming, and the multilayer film of the present invention having excellent deep drawability without causing pinholes is used, so that the dimensional accuracy is high and the shielding property is excellent. Battery can be provided.

It is a graph which shows an example of the stress-strain curve obtained when performing a tensile test with respect to the multilayer film of embodiment which concerns on this invention. It is a schematic block diagram which shows an example of the apparatus which manufactures the biaxially stretched nylon film which concerns on this invention. It is a graph which shows the stress-strain curve obtained when the tensile test was done with respect to the multilayer film obtained in Example 1. FIG. It is a graph which shows the stress-strain curve obtained when the tensile test was done with respect to the polyethylene terephthalate film. It is a graph which shows the stress-strain curve obtained when the tensile test was done with respect to aluminum foil.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
[Configuration of multilayer film]
The multilayer film according to the present embodiment includes a nylon layer (hereinafter referred to as ONy), an aluminum layer (hereinafter referred to as Al), a polyolefin layer (hereinafter referred to as PO), and a polyethylene terephthalate layer made of a stretched nylon film made of nylon 6. (Hereinafter referred to as “PET”) in the order of PET / ONy / Al / PO. In addition, as a multilayer film, it is good also as a multilayer structure by which the other film was laminated | stacked.

(Nylon layer)
The nylon layer in the present embodiment is a layer made of a stretched nylon film (ONy film).
The ONy film is formed by, for example, biaxially stretching a raw film made of nylon resin as a raw material and heat-fixing it at a predetermined temperature.
Nylon 6, nylon 8, nylon 11, nylon 12, nylon 6,6, nylon 6,10, nylon 6,12, etc. can be used as the nylon resin as the raw material. Nylon 6 (hereinafter also referred to as Ny6) is preferably used from the viewpoint of physical properties, melting characteristics, and ease of handling.
Here, the chemical formula of Ny6 is shown in the following formula (1).

  The number average molecular weight of the raw material nylon resin is preferably 15000 or more and 30000 or less, and more preferably 22000 or more and 24000 or less.

  The thickness of the ONy film is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 30 μm or less. When the thickness of the ONy film is less than the lower limit, the impact resistance of the multilayer film packaging material is lowered, and the cold formability tends to be insufficient. On the other hand, if the thickness of the ONy film exceeds the upper limit, the total thickness of the multilayer film packaging material increases, which is not preferable from the viewpoint of downsizing of the battery or the like.

(Aluminum layer)
The aluminum layer in the present embodiment is a layer made of aluminum (Al). This aluminum layer can be appropriately formed by a known method. For example, a method of laminating an aluminum foil on an ONy film can be adopted. In forming the aluminum layer, a known adhesive can be used as appropriate.

  The thickness of the aluminum layer is preferably 20 μm or more and 100 μm or less, and more preferably 30 μm or more and 50 μm or less. If the thickness of the aluminum layer is less than the lower limit, the gas barrier property of the multilayer film packaging material tends to be low. It is not preferable.

(Polyolefin layer)
The polyolefin layer in the present embodiment is a layer made of a polyolefin resin (PO). This polyolefin layer can be appropriately formed by a known method. For example, a method of laminating a polyolefin film on the aluminum layer or a method of extruding a polyolefin resin on the aluminum layer can be employed. In addition, when forming this polyolefin layer, a well-known adhesive agent can be used suitably.

  Examples of the polyolefin resin include polypropylene resins such as homopolypropylene (HPP), random polypropylene (RPP), and block polypropylene, polyethylene resins such as high density polyethylene (HDPE) and low density polyethylene (LDPE), and linear ethylene- An α-olefin copolymer or the like is used. Among these, a polypropylene resin is preferable from the viewpoint of being suitable for a battery exterior material. In particular, crystalline polypropylene (CPP) resin is preferable in terms of heat resistance and heat sealability.

  The polyolefin layer preferably has a thickness of 30 μm or more and 80 μm or less, and more preferably 35 μm or more and 50 μm or less. If the thickness of the polyolefin layer is less than the above lower limit, the sealing property of the multilayer film packaging material tends to be low. It is not preferable.

(Polyethylene terephthalate layer)
The polyethylene terephthalate layer in the present embodiment is a layer made of polyethylene terephthalate resin (PET). This polyethylene terephthalate layer can be appropriately formed by a known method. For example, a method of laminating a polyethylene terephthalate film on the nylon layer or a method of extruding a polyethylene terephthalate resin on the nylon layer can be employed. In addition, when forming this polyethylene terephthalate layer, a well-known adhesive agent can be used suitably.

The thickness of the polyethylene terephthalate layer is preferably 1 μm or more and 40 μm or less, and more preferably 2 μm or more and 30 μm or less.
When the thickness of the polyethylene terephthalate layer is less than the lower limit, the sealing property of the multilayer film packaging material tends to be low. On the other hand, when the thickness exceeds the upper limit, the total thickness of the multilayer film packaging material increases, and the size of the battery or the like is reduced. It is not preferable from the viewpoint.

In this embodiment, the elastic modulus in four directions of the multilayer film (MD direction of ONy film (moving direction of film), TD direction (direction orthogonal to moving direction of film), 45 ° direction and 135 ° direction), For the tensile stress σ _{2 at} the proportional limit and the stress ratio A (σ ₁ / σ ₂ ), etc., a tensile test (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) was performed on the multilayer film. It calculates | requires based on the stress-strain curve obtained by these.
Here, examples of the stress-strain curve obtained by the tensile test include those shown in FIG.
In FIG. 1, the vertical axis represents the tensile stress σ (MPa) of the ONy film, and the horizontal axis represents the strain ε (ε = Δl / l, l: initial length of the film, Δl: increased length of the film) of the ONy film. Show. When the tensile test of the ONy film is performed, the tensile stress σ increases in a substantially linear function as the strain ε increases, and there is a region where the tensile stress σ and the strain ε are in a proportional relationship. In the present invention, the maximum stress (σ ₂ ) in this region is defined as the tensile stress σ ₂ at the proportional limit, and the strain at this time is defined as the strain ε ₁ at the proportional limit. Further, the proportionality constant (σ / ε) between the tensile stress σ and the strain ε up to this proportional limit is defined as the elastic modulus (the proportionality constant is obtained from the slope of the stress-strain curve). When the strain ε further increases, the tensile stress σ also increases with this, and when the strain ε ₂ is reached, the film breaks. Such stress-strain curves are acquired in four directions (MD direction, TD direction, 45 ° direction and 135 ° direction of the ONy film) for one multilayer film.

  In the multilayer film of this embodiment, the elastic modulus is required to be 1000 MPa or more and 2000 MPa or less in all of the four directions. When the elastic modulus in any one of the four directions exceeds the upper limit, the moldability of the film becomes insufficient, and thickness unevenness easily occurs in the molded product. Further, from the viewpoint of the balance between the strength of the film and the moldability, the elastic modulus is preferably 1100 MPa or more and 1900 MPa or less, more preferably 1200 MPa or more and 1800 MPa or less, and particularly preferably 1300 MPa or more and 1800 MPa or less.

In the multilayer film of this embodiment, it is necessary that the tensile stress σ _{2 at} the proportional limit is 20 MPa or more and 40 MPa or less in all of the four directions. If the proportional limit of any one of the four directions exceeds the upper limit, spring back cannot be sufficiently suppressed.
From the viewpoint of the balance between the handleability of the film and the spring back, the tensile stress σ ₂ is preferably 22 MPa or more and 40 MPa or less, more preferably 25 MPa or more and 38 MPa or less, and particularly preferably 27 MPa or more and 38 MPa or less.

In the multilayer film of the present embodiment, the strain tensile stress sigma ₁ at the time of a 0.5, the ratio of the tensile stress sigma ₂ in proportional limit stress ratio A is (σ _{1 /} σ _2), wherein All of the four directions need to be 2.5 or less.
The spring ratio can be sufficiently suppressed, and pinholes can be reliably prevented from occurring during cold forming, and from the viewpoint of producing a molded product having a deep drawability and a sharp shape, the stress ratio A (σ ₁ / σ ₂ ) is preferably 1.5 or more and 2.5 or less, more preferably 1.6 or more and 2.4 or less, and particularly preferably 1.7 or more and 2.3 or less.

That is, in draw forming such as cold forming, the degree of bending, shearing, drawing, etc. differs depending on the film portion. Therefore, even after drawing, depending on the part of the film, the proportional limit is not exceeded, and it is assumed that there is a part that is elastically deformed without causing plastic deformation. The reason why there is a correlation between the springback during cold forming and the elastic modulus and the tensile stress σ ₂ at the proportional limit is that there is an elastically deformed portion of the molded product after cold forming It is assumed that springback is generated by the elastically deformed portion. On the other hand, even when the deformation exceeds the proportional limit, it is surmised that, when the load is removed, a slight springback occurs. And, as the value of the stress ratio A (σ ₁ / σ ₂ ), which is the ratio between the tensile stress σ ₁ when the strain becomes 0.5 and the tensile stress σ ₂ at the proportional limit, increases, the proportional limit is exceeded. It is presumed that springback is likely to occur at the part where deformation occurs.
As described above, when the elastic modulus, the tensile stress σ _{2 at} the proportional limit, and the stress ratio A (σ ₁ / σ ₂ ) satisfy the above conditions, the elastically deformed portion in the molded product during cold forming Can be sufficiently reduced, and the spring back at the portion where the deformation exceeds the proportional limit in the molded product can be sufficiently suppressed. As a result, the inventor presumes that a multilayer film capable of sufficiently suppressing spring back during cold forming is obtained.

Further, among the stress ratios A in these four directions, the ratio (A _max / A _min ) between the maximum stress ratio A _max and the minimum stress ratio A _min is preferably 1.2 or less. . When the ratio (A _max / A _min ) exceeds 1.2, the uneven thickness is poor and locally thins, and the multilayer film may be broken.
The ratio (A _max / A _min ) is preferably 1.19 or less, more preferably 1.18 or less, from the viewpoint of producing a multi-layer film with a good balance during cold molding and producing a molded product having a uniform thickness. Particularly preferably, it is 1.17 or less.

In the multilayer film of the present embodiment, it is preferable that the tensile rupture strength σ ₃ , which is the tensile strength at break in the four directions in the multilayer film tensile test, is 55 MPa or more. When the tensile rupture strength σ _{3 in the} four directions is less than 55 MPa, the multilayer film tends to break during cold deep drawing, and good cold formability may not be obtained.
From the viewpoint of obtaining sufficient processing strength and making the multilayer film more difficult to break during cold forming, it is preferable that the tensile breaking strength σ ₃ in all four directions is 60 MPa or more, more preferably 65 MPa. As described above, it is particularly preferably 70 MPa or more.

In the multilayer film of the present embodiment, the strain ε ₂ at break is 0.7 or more in all the four directions (the elongation to break in the four directions is 70% or more in all). Preferably, it is 0.72 or more, more preferably 0.75 or more.
Thereby, a multilayer film comes to extend with sufficient balance at the time of cold molding, and there exists a tendency for the draw-molding property when it is used as a multilayer film packaging material, and a molded product of uniform thickness can be manufactured.

And in the multilayer film of this embodiment, it is preferable that tensile stress (sigma) ₁ when elongation rate becomes 50% is 45 Mpa or more about all four directions. If the tensile stress σ _{1 in} four directions is less than 45 MPa, the thickness of the molded product may be nonuniform during cold forming.
From the viewpoint of the uniformity of the thickness of the molded article, the tensile stress σ _{1 in} the four directions is preferably 45 MPa or more and 100 MPa or less, more preferably 50 MPa or more and 95 MPa or less, and particularly preferably 55 MPa or more and 90 MPa or less.

Note that the thickness of the ONy film, the aluminum layer, and the polyolefin layer is adjusted as means for bringing the elastic modulus of the multilayer film, the tensile stress σ _{2 at} the proportional limit, and the stress ratio A (σ ₁ / σ ₂ ) into the above-described ranges. And adjusting the stretching ratio and stretching temperature during production of the ONy film, the heat setting temperature after stretching, and adjusting the raw material of the ONy film.
As a draw ratio at the time of manufacture, it is 2.8 times or more in each of MD direction and TD direction, More preferably, it is 3.0 times or more. In addition, the said draw ratio is 4.5 times or less from a viewpoint of the practicality of an ONy film, for example, More preferably, 4.0 times or less is suitable.
Moreover, you may provide the difference of the draw ratio in MD direction at the time of manufacture, and TD direction. As a difference of the draw ratio in MD direction and TD direction at the time of manufacture, the difference (TD-MD) which subtracted the draw ratio of MD direction from the draw ratio of TD direction is 0.1 times or more, for example, More preferably Is 0.1 times or more and 0.8 times or less, and particularly preferably 0.2 to 0.8 times.
The heat setting temperature after stretching is, for example, 150 ° C. or higher and 218 ° C. or lower, more preferably 160 ° C. or higher and 215 ° C. or lower, and particularly preferably 190 ° C. or higher and 215 ° C. or lower.

[Configuration of multilayer film packaging]
The multilayer film packaging material of this embodiment is composed of the multilayer film and is formed by molding the multilayer film. In general, a multilayer film wrapping material including an aluminum layer is not suitable for cold forming because the aluminum layer is easily broken by necking during cold forming. In this regard, according to the multilayer film packaging material of the present embodiment, the multilayer film has excellent deep-drawing moldability, so that it is possible to suppress breakage of the aluminum layer during cold deep-drawing molding, etc. Generation of pinholes in the material can be suppressed. Further, the multilayer film can sufficiently suppress spring back during cold forming. Therefore, even when the total packaging material thickness is thin, a molded product having a sharp shape, high strength and high dimensional accuracy can be obtained.

The thickness of the multilayer film packaging material of this embodiment is preferably 200 μm or less. If the thickness of the multilayer film packaging material exceeds 200 μm, it becomes difficult to form the corner part by cold molding, and it tends to be difficult to obtain a molded product with a sharp shape. From the viewpoint of, it is not preferable.
Moreover, in the multilayer film packaging material of this embodiment, it is preferable that the thickness ratio of PET / ONy / Al / PO is 1-40 μm / 9-40 μm / 30-100 μm / 20-150 μm. If the thickness ratio deviates from this, the cost may increase or the deep drawability during cold forming may be deteriorated.

[Method for producing stretched nylon film]
Next, a method for producing an ONy film used in the present embodiment will be described with reference to the drawings.
First, an apparatus for producing an ONy film used in this embodiment will be described with an example.
As shown in FIG. 2, the film manufacturing apparatus 100 includes an original fabric manufacturing apparatus 90 for manufacturing the original fabric film 1, a biaxial stretching apparatus (tubular stretching apparatus) 10 that stretches the original fabric film 1, and stretching. A first heat treatment device 20 (preheating furnace) that preheats a base film 2 that is folded later (hereinafter also simply referred to as “film 2”), a separation device 30 that separates the preheated film 2 into two upper and lower sheets, A second heat treatment device 40 that heat-treats (heat-set) the separated film 2, a tension control device 50 that applies tension to the film 2 from the downstream side when the film 2 is heat-set, and the film 2 is heat-set. And a winding device 60 for winding the biaxially stretched nylon film 3 (hereinafter also simply referred to as “film 3”).

As shown in FIG. 2, the raw fabric manufacturing apparatus 90 includes an extruder 91, a circular die 92, a water cooling ring 93, a stabilizer plate 94, and a pinch roll 95.
The tubular stretching device 10 is a device for producing a film 2 by biaxially stretching (bubble stretching) a tubular raw film 1 with the pressure of internal air. As shown in FIG. 2, the tubular stretching device 10 includes a pinch roll 11, a heating unit 12, a guide plate 13, and a pinch roll 14.
The first heat treatment apparatus 20 is an apparatus for preliminarily heat-treating the flat film 2. As shown in FIG. 2, the first heat treatment apparatus 20 includes a tenter 21 and a heating furnace 22.
As shown in FIG. 2, the separating device 30 includes a guide roll 31, a trimming device 32, separating rolls 33A and 33B, and grooved rolls 34A to 34C. Further, the trimming device 32 has a blade 321.

The 2nd heat processing apparatus 40 is provided with the tenter 41 and the heating furnace 42, as shown in FIG.
As shown in FIG. 2, the tension control device 50 includes guide rolls 51 </ b> A and 51 </ b> B and a tension roll 52.
As shown in FIG. 2, the winding device 60 includes a guide roll 61 and a winding roll 62.

  Next, each process which manufactures an ONy film using this film manufacturing apparatus 100 is demonstrated in detail.

(Raw film production process)
As shown in FIG. 2, the raw material nylon resin is melt-kneaded by an extruder 91 and extruded into a tube shape by a circular die 92. The tubular molten resin is cooled by a water cooling ring 93. The raw film 1 is molded by rapidly cooling a molten nylon resin as a raw material by a water cooling ring 93. The cooled original film 1 is folded by the stabilizer 94. The folded raw film 1 is sent to the next stretching step as a flat film by the pinch roll 95.

(Stretching process)
As shown in FIG. 2, the raw film 1 manufactured by the raw film manufacturing process is introduced into the apparatus as a flat film by a pinch roll 11. The introduced raw film 1 is bubble-stretched by being heated with infrared rays at the heating unit 12. Thereafter, the film 2 after being bubble-stretched is folded by the guide plate 13. The folded film 2 is pinched by the pinch roll 14 and sent to the next first heat treatment step as a flat film 2.

At this time, it can be expected that the impact strength is improved by setting the draw ratio in the MD direction and the TD direction to 2.8 times or more, respectively.
Further, the difference (TD-MD) obtained by subtracting the draw ratio in the MD direction from the draw ratio in the TD direction is preferably 0.1 or more, more preferably 0.2 or more and 0.8 or less. More preferably, it is 3 or more and 0.8 or less. If the value of TD-MD is less than the above lower limit, the deep drawability of the resulting film tends to be insufficient, and the thickness accuracy of the film tends to be lowered. In particular, when the value of TD-MD is 0.1 or less, the stretching stability is inferior and the thickness accuracy of the film tends to decrease. On the other hand, when the value of TD-MD exceeds the above upper limit, the deep drawability of the resulting film tends to be insufficient, and the stretching stability tends to decrease.

(First heat treatment process)
The film 2 sent from the stretching process is at a temperature that is equal to or higher than the shrinkage start temperature of the film 2 and about 30 ° C. lower than the melting point of the film 2 while being gripped at both ends by clips (not shown) of the tenter 21. It is heat-treated in advance at a temperature lower than that and sent to the next separation step.
The heat treatment temperature in the first heat treatment is preferably 120 ° C. or higher and 190 ° C. or lower, and the relaxation rate is preferably 15% or lower.
By this first heat treatment step, the crystallinity of the film 2 is increased, and the slipping property between the overlapping films is improved.

(Separation process)
As shown in FIG. 2, the flat film 2 sent through the guide roll 31 is cut into both ends by a blade 321 of a trimming device 32 and separated into two films 2A and 2B. And film 2A, 2B is isolate | separated, interposing air between film 2A, 2B by a pair of separation roll 33A, 33B located up and down apart. The incision of the flat film 2 may be performed so that a part of the ear is generated by positioning the blade 321 slightly inward from both ends, or by positioning the blade 321 in the fold portion of the film 2. , It may be performed so that the ear does not occur.
These films 2A and 2B are overlapped again by three grooved rolls 34A to 34C positioned in order in the film flow direction, and sent to the next second heat treatment step. In addition, these grooved rolls 34A to 34C are obtained by plating the surface after the grooved processing. A good contact state between the films 2A and 2B and the air can be obtained through the grooves.

(Second heat treatment process (heat setting process))
The overlapped films 2A and 2B are heat-treated at a temperature equal to or lower than the melting point of the resin constituting the film 2 and about 30 ° C. lower than the melting point while being gripped at both ends by clips (not shown) of the tenter 41. It is (heat-set) and becomes a biaxially stretched nylon film 3 (hereinafter also referred to as film 3) having stable physical properties, and is sent to the next winding step.
The heat treatment temperature in the second heat treatment (heat setting) is preferably 150 ° C. or higher and 218 ° C. or lower. If the heat treatment temperature is less than the lower limit, the film shrinkage rate tends to increase and the risk of delamination tends to increase.On the other hand, if the upper limit is exceeded, the bowing phenomenon at the time of heat setting increases and the distortion of the film increases. Also, the density tends to be too high, and the degree of crystallinity tends to be too high, making the film difficult to deform.
In addition, the relaxation rate at this time is preferably 15% or less.
A strong tension is applied to the films 2A and 2B in the heating furnace 42 by the tension control device 50 located on the downstream side.

(Winding process)
The film 3 heat-set in the second heat treatment step is wound as films 3A and 3B on the two winding rolls 62 via the guide roll 61 via the tension control device 50.

[Modification of Embodiment]
The aspect described above shows one aspect of the present invention, and the present invention is not limited to the above-described embodiment, and has the configuration of the present invention and can achieve the object and effect. It goes without saying that modifications and improvements within the scope are included in the content of the present invention. In addition, the specific structure and shape in carrying out the present invention may be used as other structures and shapes within the scope of achieving the object and effect of the present invention.

For example, in the present embodiment, a multilayer film of a PET / ONy / Al / PO laminate mode is used, but the present invention is not limited to this. For example, on at least one surface of the above-mentioned ONy film, an aluminum layer, a polyester resin, polyvinyl chloride (PVC), a polyvinylidene chloride resin (PVDC), a polyvinylidene chloride copolymer resin, a lubricant, A layer in which an antistatic agent or a layer of nitrified cotton amide resin (which may be a coating layer) is further laminated may be used. Further, on at least one surface of the aluminum layer, polyethylene terephthalate (PET), polyester resin, polyvinyl chloride (PVC), polyvinylidene chloride resin (PVDC), polyvinylidene chloride copolymer resin, lubricant, Further, a layer in which an antistatic agent or a layer of nitrified cotton amide resin (which may be a coating layer) is further laminated may be used. Similarly, an aluminum layer, polyethylene terephthalate (PET), polyester resin, polyvinyl chloride (PVC), polyvinylidene chloride resin (PVDC), or polyvinylidene chloride copolymer is formed on at least one surface of the polyolefin layer. A layer obtained by further laminating a layer of resin, lubricant, antistatic agent, nitrified cotton amide resin or the like (may be a coating layer) may also be used. Also, an aluminum layer, polyethylene terephthalate (PET), polyester resin, polyvinyl chloride (PVC), polyvinylidene chloride resin (PVDC), or polyvinylidene chloride copolymer is provided on at least one surface of the polyethylene terephthalate layer. A layer obtained by further laminating a layer of resin, lubricant, antistatic agent, nitrified cotton amide resin or the like (may be a coating layer) may also be used.
By laminating such a laminate substrate and coating layer, it is possible to improve production efficiency and transport efficiency, and to improve functionality (chemical resistance, electrical insulation, moisture resistance, cold resistance, A multilayer film to which processability and the like are added can be obtained.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. Incidentally, characteristics in each example (elastic modulus of the multilayer film, the stress sigma ₁ Tensile at strain 0.5, the tensile stress sigma ₂ in proportional limit, stress ratio _{A (σ 1 / σ 2)} , stress ratio _{A max} and the stress ratio A The ratio to _min (A _max / A _min ), the strain ε ₂ at break, the tensile strength σ ₃ at break, and the springback and deep drawability were evaluated by the following methods.

(I) Tensile test A multi-layer film was subjected to a tensile test using an Instron 5564 model at a sample width of 15 mm, a chuck interval of 50 mm, and a tensile speed of 100 mm / min. Measurement was carried out for each of the MD direction, TD direction, 45 ° direction and 135 ° direction of the stretched film constituting the multilayer film. Based on the stress-strain curve obtained for each direction, the elastic modulus (MPa) in each direction, the tensile stress σ ₂ (MPa) at the proportional limit in each direction, and the strain in each direction at 0.5 Tensile stress σ ₁ (MPa), stress ratio A in each direction (A = σ ₁ / σ ₂ , σ ₁ : tensile stress at strain 0.5, σ ₂ : tensile stress at proportional limit), and these stress ratios The ratio (A _max / A _min ) between the maximum value A _max and the minimum value A _min of A, the strain ε ₂ at break in each direction, and the tensile strength σ ₃ (MPa) at break in each direction And asked.

(Ii) Springback property The multilayer film was cut to produce a strip of 120 x 80 mm, which was used as a sample. Using a 33 × 55 mm rectangular mold, the molding depth is 5 mm, cold molding is performed, the mold is removed, and the container is allowed to stand for 1 hour. The container depth after 1 hour is measured, and the retention rate (ratio of container depth and molding depth) is calculated.
A: Retention rate is 90% or more.
○: Retention rate is 70% or more and less than 90%.
X: Retention rate is less than 70%.

(Iii) Deep-drawing moldability The multilayer film was cut to produce a 120 × 80 mm strip piece as a sample. Using a 33 x 55 mm rectangular mold, press it with a surface pressure of 0.1 MPa, change the molding depth from 0.5 mm to 0.5 mm, and cold mold each 10 samples. (One-stage pull-in molding). The molding depth at which no pinhole was generated in any of the 10 samples in the aluminum foil was taken as the limit molding depth, and the molding depth was shown as an evaluation value. In addition, confirmation of the pinhole confirmed the transmitted light visually.
A: The limit molding depth is 7 mm or more.
○: The limit molding depth is 6 mm or more and less than 7 mm.
(Triangle | delta): The limit shaping | molding depth is 5 mm or more and less than 6 mm.
X: The limit molding depth is less than 5 mm.

[Example 1]
(Raw film production process)
As shown in FIG. 2, after using nylon resin as a raw material and melt-kneading with an extruder 91 at 270 ° C., the melt is extruded from a circular die 92 as a tube-like film, and subsequently the tube-like melt is removed by a water-cooled ring 93. The raw film 1 was prepared by quenching with water (15 ° C.). Here, the nylon resin used is nylon 6 [UBE nylon 1022FD (trade name), relative viscosity ηr = 3.5] manufactured by Ube Industries, Ltd.
(Stretching process)
Next, as shown in FIG. 2, the raw film 1 is inserted between a pair of pinch rolls 11, and then heated by the heating unit 12 while gas is being injected therein, and is blown to the stretching start point to form bubbles. The biaxial stretching in the MD direction and the TD direction was performed by the tubular method by expanding and taking up with a pair of downstream pinch rolls 14. The magnification during this stretching was 3.0 times in the MD direction and 3.3 times in the TD direction.
(First heat treatment step and second heat treatment step)
Next, as shown in FIG. 2, the film 2 is heat-treated at a temperature of 170 ° C. by the first heat treatment apparatus 20, and after that, after passing through the separation apparatus 30, the film 2 is heat-treated at a temperature of 210 ° C. And heat fixed.
(Winding process)
Next, as shown in FIG. 2, the film 3 heat-set by the second heat treatment step is wound as two films 3 </ b> A and 3 </ b> B on two winding rolls 62 via a guide roll 61 via a tension control device 50. A biaxially stretched nylon film was produced. The thickness of the obtained biaxially stretched nylon film was 25 μm.
(Production of multilayer film)
The obtained biaxially stretched nylon film was used as a base film, a polyethylene terephthalate film having a thickness of 12 μm on one side of the base film, an aluminum foil having a thickness of 40 μm on the other side of the base film, and a thickness of 40 μm on the surface of the aluminum foil. A multilayer film was obtained by dry laminating the crystalline polyolefin film as a sealant film. The multilayer film after dry lamination was aged at 40 ° C. for 3 days. The production conditions of the obtained multilayer film are shown in Table 1.
And the elastic modulus of the obtained multilayer film, tensile stress σ _{2 at} proportional limit, stress ratio A (σ ₁ / σ ₂ ), ratio of stress ratio A _max to stress ratio A _min (A _max / A _min ), Strain ε ₂ at break, tensile rupture strength σ _{3 at} break, tensile stress σ ₁ when strain ε ₂ is 0.5 (when the elongation becomes 50%), ratio B ((σ ₃ − σ ₂ ) / (ε ₂ −ε ₁ )). The obtained results are shown in Table 2.
The resulting multilayer film was evaluated for spring back and deep drawability. The obtained results are shown in Table 3.

[Examples 2 and 3]
As Examples 2 and 3, production conditions (stretch ratio, heat setting temperature) were appropriately adjusted by the production method shown in Example 1 to produce a multilayer film.
Elastic modulus of the obtained multilayer film, tensile stress σ _{2 at} proportional limit, stress ratio A (σ ₁ / σ ₂ ), ratio of stress ratio A _max to stress ratio A _min (A _max / A _min ), at break The strain ε ₂ and the tensile strength σ ₃ at break were measured. The obtained results are shown in Table 2. Moreover, the spring back property and deep drawing moldability of the obtained multilayer film were evaluated. The obtained results are shown in Table 3. And the stress-strain curve in the multilayer film obtained in Example 2 is shown in FIG.

[Comparative Examples 1 and 2]
As Comparative Example 1, a polyethylene terephthalate film (stretching method: tenter method (sequential biaxial), thickness: 25 μm, manufactured by Toray Industries, Inc.) was obtained, and as Comparative Example 2, a polyethylene terephthalate film (stretching method: tenter method (sequential biaxial) ), thickness: 25 [mu] m, to obtain the Teijin Ltd.), in the same manner as in example 1, the elastic modulus, the stress sigma ₂ tensile in proportional limit stress sigma ₁ tensile at strain 0.5, stress ratio a (σ ₁ / σ ₂ ), the ratio (A _max / A _min ) between the stress ratio A _max and the stress ratio A _min , the strain ε ₂ at break, and the tensile strength σ ₃ at break. In addition, the stress-strain curve in the polyethylene terephthalate film of Comparative Example 1 is shown in FIG.
And the multilayer film was produced similarly to Example 1 using the polyethylene terephthalate film of Comparative Examples 1 and 2, and the elastic modulus, tensile stress σ _{2 at} the proportional limit, strain 0.5 as in Example 1. Tensile stress σ ₁ , stress ratio A (σ ₁ / σ ₂ ), ratio of stress ratio A _max to stress ratio A _min (A _max / A _min ), strain ε ₂ at break, and tensile strength at break σ ₃ was measured. The obtained results are shown in Table 2. Further, the obtained multilayer film was evaluated for spring back property and deep drawability in the same manner as in Example 1. The obtained results are shown in Table 3.

[Reference test]
For reference, an aluminum foil (thickness: 40 μm) was obtained and these tensile tests were performed. A stress-strain curve in the aluminum foil is shown in FIG.

As is clear from the results shown in Table 1, the elastic modulus of the multilayer film, the tensile stress σ _{2 at} the proportional limit, and the stress ratio A (σ ₁ / σ ₂ ) satisfy the above conditions (Examples 1 to 4). Thus, it was confirmed that the spring back at the time of cold forming can be sufficiently suppressed, and that it has excellent deep drawability at the time of cold forming.
On the other hand, when the stress ratio A (σ ₁ / σ ₂ ) of the multilayer film does not satisfy the above conditions (Comparative Examples 1 and 2), the deep drawability is insufficient and the spring back cannot be sufficiently suppressed. I understood that.
Further, from the result of the reference test shown in FIG. 5, it was found that the aluminum foil had a small strain ε ₂ at the time of fracture and was difficult to extend in terms of physical properties. On the other hand, as shown in FIG. 3, it turned out that it is hard to fracture | rupture and elongation is obtained by setting it as a multilayer film with a nylon film.

  The multilayer film of the present invention can be used in, for example, industrial fields (such as lithium battery packaging materials mounted on electric vehicles, tablet-type terminal devices, smartphones, etc.), household goods fields (such as refill packaging materials for liquid detergents), pharmaceuticals, It can be suitably used as a packaging material that particularly requires pinhole resistance, such as a packaging material in the medical device field and a packaging material in the food field. The multilayer film packaging material of the present invention can be suitably used as a packaging material for cold molding that requires particularly excellent deep drawability.

      3, 3A, 3B ... Biaxially stretched nylon film

Claims (11)

A nylon layer (hereinafter referred to as ONy) made of a stretched nylon film using nylon 6 as a raw material, an aluminum layer (hereinafter referred to as Al), a polyolefin layer (hereinafter referred to as PO), and a polyethylene terephthalate layer (hereinafter referred to as PET) are PET. / ONy / Al / PO in the order of multilayer film,
Stress-strain in four directions (MD direction, TD direction, 45 ° direction and 135 ° direction of the stretched nylon film) in the tensile test (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) of the multilayer film In the curve,
The elastic modulus is 1000 MPa or more and 2000 MPa or less in all of the four directions,
The tensile stress σ _{2 at the} proportional limit is 20 MPa or more and 40 MPa or less in each of the four directions.
Stress ratio A (σ), which is the ratio of the tensile stress σ ₁ when the strain ε ₂ at the time of breaking in the four directions is 0.5 (the elongation to break is 50%) and the tensile stress σ _{2 1} / σ ₂ ) is 2.5 or less in all of the four directions. The multilayer film according to claim 1,
The stress ratio A (σ ₁ / σ ₂ ) is 1.5 or more in all of the four directions. The multilayer film according to claim 1 or 2,
Of the stress ratios A in the four directions, a ratio (A _max / A _min ) between the maximum stress ratio A _max and the minimum stress ratio A _min is 1.2 or less. Multi-layer film. A multilayer film according to any one of claims 1 to 3,
The multilayer film, wherein the tensile strength σ ₃ at the time of breaking in the four directions in the tensile test of the multilayer film is 55 MPa or more. A multilayer film according to any one of claims 1 to 4,
The multilayer film characterized by having a strain ε ₂ at break of 0.7 or more in each of the four directions. A multilayer film according to any one of claims 1 to 5,
In the tensile stress-strain curve in the tensile test of the multilayer film, the tensile stress σ ₁ when the strain ε ₂ at break was 0.5 (elongation rate was 50%) was 45 MPa or more in all four directions. A multilayer film characterized by A multilayer film according to any one of claims 1 to 6,
The multi-layer film, wherein the PO is a crystalline polypropylene layer. A multilayer film according to any one of claims 1 to 7,
A multilayer film characterized by being for cold forming. A multilayer film packaging material using the multilayer film according to any one of claims 1 to 8. A draw-molded product, wherein the multilayer film according to any one of claims 1 to 8 is draw-molded. A multilayer film according to any one of claims 1 to 8, and a battery body,
The battery is characterized in that the multilayer film covers the battery body and is used as an exterior material with the PET side as an outer surface side.