JPWO2017170333A1 - Battery packaging laminate - Google Patents

Abstract

To provide a laminated body for battery packaging that not only can suppress the generation of pinholes during drawing, but also has little deterioration in appearance and strength even when exposed to an electrolyte.
At least a base material layer, an aluminum foil, and a sealant layer are laminated in this order, the base material layer has the following characteristics (a) to (d), and a biaxially stretched polybutylene terephthalate film having a thickness of 10 to 30 μm. The laminated body for battery packaging characterized by being.
(A) 60 to 90% by weight of polybutylene terephthalate resin (A), 10 to 40% by weight of polyester resin (B) other than polybutylene terephthalate resin (A),
(B) The intrinsic viscosity of the film is 0.81 dl / g or more.
(C) The puncture strength is 0.5 N / μm or more.
(D) The haze of the film is 10% or less, and the dynamic friction coefficient of at least one side is 0.4 or less.

Description

In recent years, lithium batteries have been used for various purposes and are used as small and large-capacity power sources for personal computers, mobile terminal devices (cell phones, PDAs, etc.), video cameras, electric vehicles, energy storage batteries, robots, satellites, etc. Yes.
As the exterior body of a lithium battery, a metal can obtained by pressing a metal into a cylindrical or rectangular parallelepiped container or a multilayer film composed of an outermost layer / aluminum / sealant layer in a bag shape is used. ing. In particular, from the viewpoint of the degree of freedom of shape and size reduction, and the heat dissipation performance with respect to the heat generation of the battery, in recent years, a bag-like exterior body made of a multilayer film has come to be preferred.

  The characteristics and functions required for battery exterior materials include high moisture resistance, acid resistance (resistance to hydrofluoric acid generated by electrolyte degradation and hydrolysis), cold formability, sealing performance, puncture resistance, Pinhole resistance, insulation, heat resistance, cold resistance and the like are indispensable, and in particular, moisture resistance, acid resistance, and cold formability are important factors.

  Conventionally used as the above-described battery exterior is, for example, as in Patent Document 1, a polyamide film / polyester film bonding or the like is used. However, in the case of such a configuration, since the process includes a lamination process of a polyamide film and a polyester film, the process becomes complicated, and there is a limit in terms of reducing the weight of the film.

  Patent Document 2 proposes a film excellent in moldability even when a polyester film made of polyethylene terephthalate (PET) or PET and isophthalic acid copolymerized PET resin is used alone. However, while further deep drawability is required for battery exterior use, further improvements in aluminum followability and moldability have been desired.

  As a means for achieving both puncture resistance and chemical resistance of the film, it is conceivable to use a polybutylene terephthalate (PBT) resin having a molecular skeleton that is more flexible than PET resin. For example, in Patent Document 3, a technique has been known that has an excellent processability for an application in which drawing is performed by using an unstretched PBT film having a specific range of stab displacement for exterior use of a lithium ion battery. . However, since this conventional technique is not stretched, the orientation of the PBT is weak, and from the viewpoint of mechanical characteristics and piercing strength, the characteristics of the original PBT cannot be sufficiently extracted, and the piercing strength is insufficient. It was insufficient for improving moldability as an outer packaging material of an ion battery.

As a means for obtaining a polybutylene terephthalate (PBT) film having excellent puncture resistance, a means for stretching the PBT and increasing the degree of plane orientation can be mentioned.
For example, in Patent Document 4, after stretching in the transverse direction (TD) at a stretching ratio of 3.5 times or less, the film is stretched in the MD direction at a deformation rate of 100000% / min or more, and biaxially stretched polybutylene terephthalate (PBT) film. A technique for producing a uniformly stretched film without unevenness in thickness has been known. However, as can be seen from the results of the examples, this conventional technique increases only the deformation speed in the machine direction (MD), so that the elongation is low and the film cannot be balanced in the MD and TD directions. There was a point.

  Patent Document 5 discloses a polybutylene terephthalate (PBT) film formed by using a tubular simultaneous biaxial stretching method so that the breaking strength in four directions is not less than a specific value. In addition, a technique of excellent mechanical properties and dimensional stability has been known. However, this conventional technique has a problem that the thickness accuracy is poor due to the manufacturing method and the puncture strength is low because the plane orientation coefficient does not increase.

  In Patent Document 6, in addition to polybutylene terephthalate (PBT), two types of resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are alternately laminated, thereby providing high rigidity and high temperature dimensions. A technique that is excellent in stability and moldability has been known. However, since this conventional technique has laminated a layer made of a resin of polyethylene naphthalate (PET) or polyethylene naphthalate (PEN) in addition to polybutylene terephthalate (PBT), the stretching temperature is higher than that of polybutylene terephthalate (PBT). Polybutylene terephthalate (PBT) is stretched at a high temperature because it is stretched at a stretching temperature of PET or PEN having a high glass transition temperature (Tg), and does not bring out the characteristics of the original PBT film. In addition, since there are two types of resin compositions in the film, there is a problem in that it is difficult to add trimming scraps and the like at the time of film formation to the raw material and reuse them, which is disadvantageous in terms of economy.

Japanese Patent Laid-Open No. 9-115428 Japanese Patent Laid-Open No. 2004-362953 JP 2012-77292 A JP 51-146572 A JP 2012-146636 A WO2004 / 108408 publication

  The present invention has been made against the background of such prior art problems. That is, an object of the present invention is to provide a battery packaging laminate that not only can suppress the occurrence of pinholes during drawing, but also has a small decrease in appearance and strength even when exposed to an electrolytic solution.

As a result of intensive studies to achieve the above object, the present inventors have completed the present invention. That is, in the present invention, at least a base material layer, an aluminum foil, and a sealant layer are laminated in this order, the base material layer has the following characteristics (a) to (d), and is biaxial with a thickness of 10 to 30 μm. A battery packaging outer body characterized by being a stretched polybutylene terephthalate film (a) 60 to 90% by weight of a polybutylene terephthalate resin (A) and 10% of a polyester resin (B) other than the polybutylene terephthalate resin (A) Contains ~ 40 wt%,
(B) The intrinsic viscosity of the film is 0.81 dl / g or more.
(C) The puncture strength is 0.5 N / μm or more.
(D) The haze of the film is 10% or less, and the dynamic friction coefficient of at least one side is 0.4 or less.

  In this case, the polyester resin (B) other than the polybutylene terephthalate resin (A) is a polyester such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), or polypropylene terephthalate (PPT). In addition to resin, polybutylene obtained by copolymerization of at least one dicarboxylic acid selected from the group consisting of isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid Naphthalate (PBT) resin, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanedi Polybutylene naphthalate (PBT) resin in which at least one diol component selected from the group consisting of alcohol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate is copolymerized, or isophthalic acid, orthophthalic acid A polybutylene naphthalate (PBT) resin copolymerized with at least one dicarboxylic acid selected from the group consisting of naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid, 3-butanediol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethyleneglycol Selected from at least one resin selected from polyethylene naphthalate (PET) resin copolymerized with at least one diol component selected from the group consisting of polyethylene, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate It is preferred that it is at least one resin.

  According to the present invention, a biaxially stretched polybutylene terephthalate film excellent in piercing strength, electrolytic solution resistance, and thickness accuracy can be obtained in a biaxially stretched polybutylene terephthalate film and an outer casing for drawing and packaging using the same. Therefore, it is possible not only to suppress the generation of pinholes during drawing, but also to obtain an outer packaging material for battery packaging that has little deterioration in appearance and strength even when exposed to an electrolytic solution.

Hereinafter, the present invention will be described in detail.
The polyester thermoplastic resin composition used for the base material layer of the present invention mainly comprises a polybutylene terephthalate (PBT) resin (A), and the content of the polybutylene terephthalate (PBT) resin (A). Is preferably 60% by mass or more, preferably 75% by mass or more, and more preferably 85% by mass or more. If it is less than 60% by mass, impact strength and puncture resistance are lowered, and the film properties are not sufficient.
The polybutylene terephthalate (PBT) resin used as the main constituent component is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 98 mol% or more as the dicarboxylic acid component. Yes, and most preferably 100 mol%. As the glycol component, 1,4-butanediol is preferably 90 mol% or more, more preferably 95 mol% or more, further preferably 97 mol% or more, and most preferably 1,4-butane during polymerization. Except for the by-product produced by the ether bond of the diol, it is not included.

The polyester thermoplastic resin composition used for the base material layer of the present invention may contain a polyester resin other than the PBT resin for the purpose of adjusting the film forming property when biaxial stretching and the mechanical properties of the obtained film. it can.
Examples of polyester resins (B) other than polybutylene terephthalate (PBT) resin (A) include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polypropylene terephthalate (PPT). In addition, polybutylene obtained by copolymerizing at least one dicarboxylic acid selected from the group consisting of isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid Phthalate (PBT) resin, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol Polybutylene naphthalate (PBT) resin copolymerized with at least one diol component selected from the group consisting of diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate, or isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid 1,3-butane, a polybutylene naphthalate (PBT) resin copolymerized with at least one dicarboxylic acid selected from the group consisting of acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid Diol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, Cyclohexane diol, polyethylene glycol, at least one resin at least one diol component selected from the county consisting of polytetramethylene glycol and polycarbonate is selected from the copolymerization polyethylene naphthalate (PET) resins.

The lower limit of the intrinsic viscosity of the polybutylene terephthalate (PBT) resin (A) used for the base material layer of the present invention is preferably 0.8 dl / g, more preferably 0.95 dl / g, still more preferably 1. 0 dl / g.
When the intrinsic viscosity of the polybutylene terephthalate (PBT) resin (A) is less than 0.9 dl / g, the intrinsic viscosity of the film obtained by film formation may be reduced, and impact strength and puncture resistance may be reduced. .
The upper limit of the intrinsic viscosity of the polybutylene terephthalate (PBT) resin (A) is preferably 1.3 dl / g. When the above is exceeded, the stress at the time of extending | stretching will become high too much, and film forming property may worsen.

  The upper limit of the amount of the polyester resin (B) other than the polybutylene terephthalate (PBT) resin (A) is preferably 40% by mass or less, more preferably 35% by mass or less, and particularly preferably 15% by mass or less. . If the addition amount of the polyester resin (B) other than the polybutylene terephthalate (PBT) resin (A) exceeds 40% by mass, the mechanical properties of the biaxially stretched polybutylene terephthalate film are impaired, and the impact strength and puncture resistance are not good. In addition to being sufficient, transparency and barrier properties may decrease.

  The lower limit of the melting temperature of the polyester-based thermoplastic resin composition is preferably 200 ° C., and if it is lower than 200 ° C., ejection may become unstable. The upper limit of the resin melting temperature is preferably 300 ° C., and if it exceeds 300 ° C., the PBT resin may be deteriorated.

  The polyester-based thermoplastic resin composition may contain conventionally known additives such as a lubricant, a stabilizer, a colorant, an antioxidant, an antistatic agent, and an ultraviolet absorber as necessary.

In the present invention, in addition to using polybutylene terephthalate as a means for improving the formability at the time of drawing, it is effective to adjust the slipperiness of at least one surface of the film.
The upper limit of the dynamic friction coefficient of at least one surface of the biaxially stretched polybutylene terephthalate film is preferably 0.4 or less, preferably 0.39 or less, and most preferably 0.38 or less.

  As the lubricant type for adjusting the dynamic friction coefficient of the biaxially stretched polybutylene terephthalate film, in addition to inorganic lubricants such as silica, calcium carbonate, and alumina, organic lubricants are preferable, silica and calcium carbonate are more preferable. Is particularly preferable in terms of reducing haze. By these, transparency and slipperiness can be expressed.

  The lower limit of the lubricant concentration in the polyester-based thermoplastic resin composition is preferably 100 ppm, and if it is less than 100 ppm, the slipping property may be lowered. The upper limit of the lubricant concentration is preferably 20000 ppm, and if it exceeds 20000 ppm, the transparency may be lowered.

The lower limit of the intrinsic viscosity of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 0.80 dl / g, more preferably 0.85 dl / g, and even more preferably 0.90 dl. / G, particularly preferably 0.95 dl / g. If it exceeds the above, impact strength, puncture resistance and the like are improved. Moreover, the barrier property after bending is also good.
The upper limit of the intrinsic viscosity of the biaxially stretched polybutylene terephthalate film is preferably 1.2 dl / g, more preferably 1.1 dl / g. When the above is exceeded, the stress at the time of extending | stretching does not become high too much, and film forming property becomes favorable.

  The lower limit of the intrinsic viscosity of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 0.8, more preferably 0.85, even more preferably 0.9, especially Preferably, and most preferably. If it is less than the above, impact strength, puncture resistance and the like may decrease. The upper limit of the intrinsic viscosity of the film is preferably 1.2. When the above is exceeded, the stress at the time of extending | stretching will become high too much, and film forming property may worsen.

The biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention preferably has a resin having the same composition throughout the film.
In addition, a biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention may be laminated with a layer of another material on the biaxially stretched polybutylene terephthalate film used as the base material layer of the present invention. The film can be bonded after creation, or can be bonded during film formation.

  The lower limit of the piercing strength (N / μm) of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 0.5, more preferably 0.7, and further preferably 0. .8. When it is less than the above, the strength may be insufficient when used as an outer packaging bag for a lithium ion battery.

The upper limit of the piercing strength (J / μm) of the biaxially stretched polybutylene terephthalate film used for the base material layer is preferably 1.5. If the above is exceeded, the improvement effect may become saturated.
The biaxially stretched polybutylene terephthalate film piercing strength used for the base material layer can be controlled by MD magnification, heat setting temperature, and multilayering.

  The lower limit of the impact strength, J / μm, of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 0.055, more preferably 0.060, and even more preferably 0.065. It is. If it is less than the above, the strength may be insufficient when used as a bag.

  The upper limit of the impact strength, J / μm, of the biaxially stretched polybutylene terephthalate film used for the base material layer is preferably 0.2. If the above is exceeded, the improvement effect may become saturated.

The upper limit of the haze (% / μm) per thickness of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 0.35%, more preferably 0.33%, Preferably it is 0.31%.
When the above is exceeded, there is a possibility that the quality of printed characters and images is impaired when printing is performed on a biaxially stretched polybutylene terephthalate film.

  The lower limit of the thermal shrinkage (%) in the longitudinal direction and the width direction of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 0. If it is less than the above, the improvement effect is saturated, and it may become mechanically brittle.

  The upper limit of the heat shrinkage rate (%) in the longitudinal direction and the width direction of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 4.0, more preferably 3.5. Yes, more preferably 3.0. If the above is exceeded, pitch deviation may occur due to dimensional changes during processing such as printing.

The lower limit of the thickness of the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is preferably 3 μm, more preferably 5 μm, and even more preferably 8 μm. If it is less than 3 μm, the strength as a film may be insufficient.
Preferably the upper limit of the thickness of the film used for a base material layer is 100 micrometers, More preferably, it is 75 micrometers, More preferably, it is 50 micrometers. If it exceeds 100 μm, it may become too thick and processing for the purpose of the present invention may be difficult.

(Method for producing biaxially stretched polybutylene terephthalate film used for the base material layer)
As a suitable method for obtaining the biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention, it is possible to cast multiple raw materials having the same composition during casting.
Since the PBT resin has a high crystallization speed, crystallization proceeds during casting. At this time, when cast as a single layer without forming multiple layers, there is no barrier that can suppress the growth of crystals, so these crystals grow into large spherulites. As a result, the yield stress of the obtained unstretched sheet becomes high, and not only is it easy to break during biaxial stretching, but the flexibility of the obtained biaxially stretched polybutylene terephthalate film is impaired, and impact strength and puncture resistance are reduced. It becomes a film with insufficient properties.
On the other hand, the present inventors have found that by stretching the same resin in multiple layers, the stretching stress of the unstretched sheet can be reduced and stable biaxial stretching is possible.

The method for producing a biaxially stretched polybutylene terephthalate film used for the base material layer of the present invention is specifically a step of melting a thermoplastic resin composition containing 60% by weight or more of a polybutylene terephthalate resin to form a molten fluid. The laminated fluid formed in (1) is formed from the molten fluid formed in step (2), and the laminated fluid formed in (2) is discharged from a die and brought into contact with a cooling roll to solidify to form a laminated body. Step (3), and biaxially stretching the laminate (4).
Another step may be inserted between step (1) and step (2), step (2) and step (3). For example, a filtration process, a temperature change process, etc. may be inserted between the process (1) and the process (2). Further, a temperature changing process, a charge adding process, and the like may be inserted between the process (2) and the process (3). However, there should be no step of destroying the laminated structure formed in step (2) between step (2) and step (3).

  In the step (1), the method of melting the thermoplastic resin to form a molten fluid is not particularly limited, but a preferable method is a method of heating and melting using a single screw extruder or a twin screw extruder. it can.

  The method of forming the laminated fluid in the step (2) is not particularly limited, but a static mixer and / or a multilayer feed block is more preferable from the viewpoints of facility simplicity and maintainability. Further, in view of uniformity in the sheet width direction, those having a rectangular melt line are more preferable. It is further preferred to use a static mixer or multilayer feed block with a rectangular melt line. In addition, you may let the resin composition which consists of several layers formed by making a several resin composition merge pass in any 1 type, or 2 or more types of a static mixer, a multilayer feed block, and a multilayer manifold.

  The theoretical number of layers in step (2) needs to be 60 or more. The lower limit of the theoretical number of layers is preferably 200, more preferably 500. If the number of theoretical layers is too small, or the distance between layer interfaces becomes long and the crystal size becomes too large, the effects of the present invention tend not to be obtained. In addition, the degree of crystallinity in the vicinity of both ends of the sheet increases, the film formation becomes unstable, and transparency after molding may decrease. The upper limit of the theoretical number of layers in step (2) is not particularly limited, but is preferably 100,000, more preferably 10,000, and still more preferably 7,000. Even if the theoretical number of layers is extremely increased, the effect may be saturated.

  When the lamination in the step (2) is performed with a static mixer, the number of theoretical laminations can be adjusted by selecting the number of elements of the static mixer. The static mixer is generally known as a static mixer (line mixer) having no drive unit, and the fluid entering the mixer is sequentially stirred and mixed by the elements. However, when the high-viscosity fluid is passed through the static mixer, the high-viscosity fluid is divided and laminated, and a laminated fluid is formed. Each time it passes through one element of the static mixer, the high-viscosity fluid is divided into two and then merged and laminated. For this reason, when a high-viscosity fluid is passed through a static mixer having n elements, a laminated fluid having a theoretical number N = 2n is formed.

  A typical static mixer element has a structure in which a rectangular plate is twisted 180 degrees, and depending on the direction of twisting, there are a right element and a left element, and the dimensions of each element are 1.5 times the diameter. Based on. The static mixer that can be used in the present invention is not limited to this.

  When the lamination in the step (2) is performed with a multilayer feed block, the theoretical number of laminations can be adjusted by selecting the number of divisions / stacking of the multilayer feed block. Multiple multilayer feed blocks can be installed in series. Moreover, it is also possible to use the highly viscous fluid itself supplied to the multilayer feed block as a laminated fluid. For example, when the number of layers of the high-viscosity fluid supplied to the multilayer feed block is p, the number of divisions / layers of the multilayer feed block is q, and the number of multilayer feed blocks is r, the number of layers N of the multilayer fluid is Xqr.

  In step (3), the laminated fluid is discharged from a die and brought into contact with a cooling roll to be solidified.

  The lower limit of the die temperature is preferably 200 ° C., and if it is less than the above, the discharge may not be stable and the thickness may be uneven. The upper limit of the die temperature is preferably 320 ° C., more preferably 300 ° C. or less, and further preferably 280 ° C. or less. When the above is exceeded, the thickness becomes non-uniform and the resin deteriorates, and the appearance may be deteriorated due to die lip contamination.

  The lower limit of the cooling roll temperature is preferably 0 ° C., and if it is less than the above, the effect of suppressing crystallization may be saturated. The upper limit of the cooling roll temperature is preferably 25 ° C, more preferably 20 ° C or less. If the above is exceeded, the crystallinity becomes too high and stretching may be difficult. Further, when the temperature of the cooling roll is in the above range, it is preferable to reduce the humidity of the environment near the cooling roll in order to prevent condensation.

In casting, since the high temperature resin contacts the surface, the temperature of the surface of the cooling roll rises. Normally, the chill roll is cooled by flowing cooling water through the pipe inside, but securing a sufficient amount of cooling water, devising the arrangement of the pipe, performing maintenance so that sludge does not adhere to the pipe, etc. It is necessary to reduce the temperature difference in the width direction. In particular, care should be taken when cooling at low temperatures without using a method such as multilayering.
At this time, the thickness of the unstretched sheet is preferably in the range of 15 to 2500 μm. More preferably, it is 500 micrometers or less, More preferably, it is 300 micrometers or less.

  Casting in the multilayer structure described above is performed with at least 60 layers, preferably 250 layers or more, more preferably 1000 layers or more. When the number of layers is small, the spherulite size of the unstretched sheet is increased, and the effect of reducing the yield stress of the obtained biaxially stretched film is lost as well as the effect of improving the stretchability is small.

  Next, the stretching method will be described. The stretching method can be simultaneous biaxial stretching or sequential biaxial stretching, but in order to increase the piercing strength, it is necessary to increase the plane orientation coefficient, and in that respect, sequential biaxial stretching is preferable.

  The lower limit of the machine direction (hereinafter referred to as MD) stretching temperature is preferably 55 ° C, more preferably 60 ° C. When the temperature is lower than 55 ° C., not only breakage is likely to occur, but also the orientation in the machine direction is strengthened by stretching at a low temperature. As a result, the mechanical strength may become uneven in the width direction. The upper limit of the MD stretching temperature is preferably 100 ° C, more preferably 95 ° C. If the temperature exceeds 100 ° C., the orientation is not applied and the mechanical properties may be deteriorated. When using a PET resin as a resin other than the PBT resin, it is preferable to raise the temperature as compared with the case of using a polybutylene terephthalate (PBT) resin alone.

  The lower limit of the MD draw ratio is preferably 2.6 times, particularly preferably 2.8 times, and further preferably 3.0 times. If it is less than the above, the orientation is not applied, so the mechanical properties and thickness unevenness may be deteriorated. The upper limit of the MD draw ratio is preferably 4.3 times, more preferably 4.0 times, and particularly preferably 3.8 times. If the above is exceeded, the effect of improving the mechanical strength and thickness unevenness may be saturated, and the vertical orientation becomes stronger. In some cases, the strain becomes large, and as a result, the mechanical strength becomes non-uniform in the width direction.

  The lower limit of the transverse direction (hereinafter referred to as TD) stretching temperature is preferably 60 ° C, more preferably 70 ° C, and further preferably 80 ° C. If it is less than the above, breakage may easily occur. The upper limit of the TD stretching temperature is preferably 100 ° C., and if it exceeds the above, since the orientation is not applied, the mechanical properties may be deteriorated. When a PET resin is used as a resin other than the PBT resin, it is preferably higher than that of the PBT resin alone.

  The lower limit of the TD stretch ratio is preferably 3.5 times, more preferably 3.6 times, still more preferably 3.7 times, and particularly preferably 4.0 times. If it is less than the above, the orientation is not applied, so the mechanical properties and thickness unevenness may be deteriorated. The upper limit of the TD stretch ratio is preferably 5 times, more preferably 4.5 times, and particularly preferably 4.0 times. If the above is exceeded, the effect of improving the mechanical strength and thickness unevenness may be saturated.

  The lower limit of the heat setting temperature is preferably 200 ° C, more preferably 205 ° C. If it is less than the above, the thermal shrinkage rate increases, and displacement or shrinkage during processing may occur. The upper limit of the heat setting temperature is preferably 250 ° C, more preferably 230 ° C. If the above is exceeded, the film will melt, and even if it does not melt, it may become brittle.

  The lower limit of the TD relaxation rate is preferably 0.5%, more preferably 2%, and even more preferably 3%. If it is less than the above, breakage may easily occur during heat setting. The upper limit of the TD relaxation rate is preferably 6%, more preferably 5%. If it exceeds the above, sagging may occur and thickness unevenness may occur, and as a result of increased shrinkage in the longitudinal direction during heat setting, the distortion of molecular orientation at the end increases, and the mechanical strength increases in the width direction. May be non-uniform.

(Laminate for battery packaging)
Hereinafter, the laminated body for battery packaging of this invention is demonstrated.
The laminated body for battery packaging according to a preferred embodiment is a laminated body in which a metal foil layer and a sealant layer are sequentially laminated on one surface side of a base material layer. The laminate is used with the base material layer on the outer side of the battery and the sealant layer on the inner side of the battery.

[Metal foil layer]
As the metal foil layer, various metal foils such as aluminum and stainless steel can be used, and aluminum foil is preferable from the viewpoint of workability such as moisture resistance and spreadability and cost. A general soft aluminum foil can be used as the aluminum foil. Among these, an aluminum foil containing iron is preferable from the viewpoint of excellent pinhole resistance and extensibility during molding.
0.1-9.0 mass% is preferable and, as for content of iron in the aluminum foil (100 mass%) containing iron, 0.5-2.0 mass% is more preferable. When the iron content is at least the lower limit value, the laminate is excellent in pinhole resistance and spreadability. If the iron content is 9.0% by mass or less, the laminate is excellent in flexibility.
The thickness of the metal foil layer is preferably 9 to 200 μm and more preferably 15 to 100 μm from the viewpoint of barrier properties, pinhole resistance, and workability.

[Sealant layer]
A sealant layer is a layer which provides the sealing performance by heat sealing in an exterior material. Examples of the sealant layer include a polyolefin resin or a resin film made of an acid-modified polyolefin resin obtained by graft-modifying an acid such as maleic anhydride to a polyolefin resin.
Examples of the polyolefin resin include low density, medium density, and high density polyethylene; ethylene-α olefin copolymer; homo, block, or random polypropylene; propylene-α olefin copolymer. These polyolefin resin may be used individually by 1 type, and may use 2 or more types together.

The sealant layer may be a single layer film or a multilayer film, and may be selected according to a required function. For example, in terms of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene is interposed can be used.
The sealant layer 16 may be blended with various additives such as a flame retardant, slip agent, anti-blocking agent, antioxidant, light stabilizer, and tackifier.
10-100 micrometers is preferable and, as for the thickness of the sealant layer 16, 20-60 micrometers is more preferable.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to the following examples. The film was evaluated by the following measurement method.

[Film thickness]
It measured by the method based on JIS-Z-1702.

[Intrinsic viscosity of film]
Based on JIS K7367-5, it measured at 30 degreeC, using the mixed solvent of a phenol (60 mass%) and 1,1,2,2-tetrachloroethane (40 mass%) as a solvent.

[Puncture strength]
It was measured in accordance with “2. Test methods for strength, etc.” in “Standards for Foods, Additives, etc. 3: Equipment and Containers and Packaging” in the Food Sanitation Law (Ministry of Health and Welfare Notification No. 20 of 1982)
A needle having a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm / min, and the strength when the needle penetrated the film was measured to obtain the piercing strength. The measurement is performed at room temperature (23 ° C.), and the unit is [N / μm].

[Dynamic friction coefficient]
Based on JIS K-7125, the dynamic friction coefficient (micro | micron | mu) d at the time of joining the surface of a film and a back surface was calculated | required in 23 degreeC and 65% RH environment using the tensile tester (ORIENTEC company make Tensilon). The weight of the thread (weight) wound with the upper film was 1.5 kg, and the size of the bottom area of the thread was 63 mm long × 63 mm wide. In addition, the tensile speed at the time of friction measurement is 200 mm / min. Met.

[Haze]
The sample was measured at three different places using a haze meter (Nippon Denshoku, NDH2000) by a method according to JIS-K-7105, and the average value was defined as haze.
The unit is [%].

[Drawing formability]
The obtained film roll and aluminum foil (8079 material, thickness 40 μm) were urethane adhesives (TM-509 manufactured by Toyo Morton Co., Ltd., CAT10L manufactured by Toyo Morton Co., Ltd., and ethyl acetate 33.6: 4.0: 62, respectively. 4 (mass ratio) was dry laminated to produce a film / aluminum foil laminate. The obtained laminate was placed in a die set mold (convex shape 90 mm × 50 mm), and was pressed at 23 ° C. by a press to perform drawing. The drawing depth at the time of molding was increased by 0.2 mm, and the maximum depth at which the laminate was not damaged was taken as the drawing depth.
Judgment ○: Molding depth 8 mm or more Δ: 4 mm to less than 8 mm ×: Less than 4 mm

[Electrolytic solution resistance]
The obtained film was cut into a size of 100 mm × 100 mm and immersed in a solution of 1 mol / L of LiPF6 in a solvent of propylene carbonate / dimethyl carbonate = 1/1 (vl%) for 24 hours. The appearance of the film after immersion for 24 hours was visually observed and judged according to the following criteria.
Judgment ○: No discoloration △: Some discoloration ×: Discoloration or dissolved

[Raw resin]
Polyethylene terephthalate (PBT); Examples 1 to 6, Comparative Examples 1 to 4
In the film production of Examples 1 to 6 and Comparative Examples 1 to 3 which will be described later, 1100-211XG (CHANGE CHUN PLASTICS CO., LTD., Intrinsic viscosity 1.28 dl / g) was used as the main raw material PBT resin.

PET-1: Examples 1 and 2 and Comparative Examples 1 and 2
In the film production of Examples 1 and 2 and Comparative Examples 1 and 2 described later, an average particle diameter of polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g composed of terephthalic acid // ethylene glycol = 100 // 100 (mol%). A resin containing 0.3% of amorphous silica of 1.5 μm was used.

PET-2; Example 3
In the film production of Example 3 described later, an isophthalic acid copolymer polyethylene terephthalate resin having an intrinsic viscosity of 0.72 dl / g composed of terephthalic acid / isophthalic acid // ethylene glycol = 80/20 // 100 (mol%) was used. .

PET-3; Example 4
In the film production of Example 4 described later, a neopentyl glycol copolymer polyethylene terephthalate resin having an intrinsic viscosity of 0.75 dl / g composed of terephthalic acid / ethylene glycol / neopentyl glycol = 100 // 70/30 (mol%) is used. It was.

PET-4; Example 5, Comparative Example 3
In the film production of Example 5 and Comparative Example 2 described later, a CHDM copolymer having an intrinsic viscosity of 0.75 dl / g composed of terephthalic acid / ethylene glycol / cyclohexanedimethanol (CHDM) = 100 // 70/30 (mol%). Polyethylene terephthalate resin was used.

TPE-2; Example 6
In the film production of Example 6 described later, the polytetramethylene glycol copolymerized PET resin as the main raw material is PTMG made of terephthalic acid / butanediol / polytetramethylene glycol (PTMG) = 100 // 85/15 (mol%). A copolymerized polyethylene terephthalate resin was used.

[Example 1]
Using a single screw extruder, melt PBT as polybutylene terephthalate resin, PET-1 as polyester resin resin, and inert particles such that silica particles with an average particle size of 2.4 μm are 1500 ppm at 295 ° C. After that, the melt line was introduced into a 12-element static mixer. Thereby, the PBT melt was divided and laminated to obtain a multilayer melt made of the same raw material. An unstretched sheet was obtained by casting from a T-die at 270 ° C., and adhering it to a cooling roll at 25 ° C. by an electrostatic adhesion method. Next, the film was stretched 3.3 times in the machine direction at 70 ° C., then passed through a tenter and stretched 4.2 times in the transverse direction at 90 ° C., and subjected to tension heat fixation treatment at 210 ° C. for 3 seconds and 5% for 1 second. After carrying out the relaxation treatment, the gripping portions at both ends were cut and removed 10% at a time to obtain a mill roll of a biaxially stretched polybutylene terephthalate film having a thickness of 12 μm. Table 1 shows the film forming conditions, physical properties, and evaluation results of the obtained film.

[Examples 2 to 6]
In Example 1, it carried out like Example 1 except having changed the raw material composition and the film forming conditions into the biaxially stretched film described in Table 1. Table 1 shows the film forming conditions, physical properties, and evaluation results of the obtained film.

[Comparative Examples 1-4]
In Example 1, it carried out like Example 1 except having changed the raw material composition and the film forming conditions into the biaxially stretched film described in Table 2. Table 2 shows the film forming conditions, physical properties, and evaluation results of the obtained film.

  As shown in Table 1, the biaxially stretched polybutylene terephthalate film and laminate (Examples 1 to 6) obtained by the present invention have excellent piercing strength, and excellent moldability and electrolytic solution resistance. Had.

On the other hand, as shown in Table 2, in Comparative Example 1, since the lubricant ratio was small, the dynamic friction coefficient was large, and the moldability was insufficient.
In Comparative Example 2, the content of polybutylene terephthalate (PET) resin was large, so that the electrolyte solution resistance was excellent, but the puncture strength and moldability were low.
Furthermore, in Comparative Example 3, since the content of the copolymerized polyethylene terephthalate resin added as a polyester resin other than polybutylene terephthalate (PBT) is large, the initial puncture strength was low and the electrolytic solution resistance was also lowered. . Furthermore, in Comparative Example 4, since the draw ratio at the time of film stretching was low, the piercing strength and moldability were insufficient.

[Reference Examples 1 and 2]
Table 1 shows the physical properties and evaluation results of commercially available polyethylene terephthalate film (Toyobo Co., Ltd., E5100) and polyamide film (Toyobo Co., Ltd., N1100).

  According to the present invention, the battery has excellent piercing strength, electrolytic solution resistance and thickness accuracy, and not only can suppress the generation of pinholes during drawing molding, but also has little deterioration in appearance and strength even when exposed to an electrolytic solution. A laminate for packaging can be obtained, and is expected to greatly contribute to the industry.

Claims (2)

For battery packaging, comprising at least a base material layer and a sealant layer, wherein the base material layer is a biaxially stretched polybutylene terephthalate film having the following characteristics (a) to (d) and a thickness of 10 to 30 μm: Laminated body.
(A) 60 to 90% by weight of polybutylene terephthalate resin (A) and 10 to 40% by weight of polyester resin (B) other than polybutylene terephthalate resin (A) are contained.
(B) The intrinsic viscosity of the film is 0.81 or more.
(C) The puncture strength is 0.5 N / μm or more.
(D) The haze of the film is 10% or less, and the dynamic friction coefficient of at least one side is 0.4 or less.   Polyester resins (B) other than polybutylene terephthalate resin (A) include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polypropylene terephthalate (PPT), and isophthalate. Polybutylene naphthalate (PBT) copolymerized with at least one dicarboxylic acid selected from the group consisting of acids, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid Resin, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol Polybutylene naphthalate (PBT) resin, or isophthalic acid, orthophthalic acid, naphthalene copolymerized with at least one diol component selected from the group consisting of polyol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate Polybutylene naphthalate (PBT) resin copolymerized with at least one dicarboxylic acid selected from the group consisting of dicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid, 1,3- Butanediol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanedi 2. At least one resin selected from polyethylene naphthalate (PET) resin copolymerized with at least one diol component selected from the group consisting of polyol, polyethylene glycol, polytetramethylene glycol and polycarbonate. The laminated body for battery packaging described in 1.