Polypropylene sealant film and exterior material for power storage devices

Abstract

To provide a polypropylene-based sealant film and an exterior material for power storage device provided with performances of good balance excellent in all of heat seal strength, whitening resistance, heat resistance, laminate strength, and blocking resistance and capable of cohesive failure of a proper heat seal peeling interface.SOLUTION: A laminate layer 20 and a heat seal layer 40 are mainly composed of a propylene-ethylene block copolymer or a propylene homopolymer, and a base material layer 30 is mainly composed of a propylene-ethylene block copolymer and the propylene-ethylene block copolymer has a weight average molecular weight of 100,000 to 600,000 as determined by gel permeation chromatography for xylene solubles, a melt flow rate of 1 to 10 g / 10 min, and an ethylene content of 10 to 70 wt.% for xylene solubles. and the substrate layer contains 5 to 30 wt.% of an ethylene / α-olefin random copolymer elastomer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polypropylene sealant film and an exterior material for a power storage device that uses the sealant film. [Background technology]

[0002] For example, retort sealant films are suitable for use as packaging materials for foods, miscellaneous goods, etc., as well as for industrial applications such as soft packs for lithium-ion batteries, etc. Soft-pack type lithium-ion batteries are obtained by filling contents such as electrolyte into a sealant film that has been molded (drawn) into a desired shape and size, and then processing it into a pouch.

[0003] Sealant films for power storage devices such as lithium-ion batteries are required to have properties such as heat seal strength, whitening resistance, heat resistance, lamination strength, and blocking resistance. They are also required to be able to vent gases to prevent sudden rupture when the internal pressure of the soft pack increases. This venting occurs through cohesive failure at the heat seal peel interface of the sealant film.

[0004] A known sealant film for use in electricity storage devices is, for example, a polypropylene-based sealant film for extrusion molding, which has a base layer mainly made of a propylene-ethylene block copolymer and a heat-seal layer mainly made of a propylene-ethylene random copolymer (see Patent Document 1). This sealant film is a film that is imparted with heat resistance and whitening resistance, and high heat-seal strength can be obtained, for example, by constructing the base layer solely from a propylene-ethylene block copolymer. However, simply increasing the heat-seal strength makes it difficult to cause peeling at the heat-sealed portion when the internal pressure increases, resulting in irregular film damage and making it difficult to properly cause cohesive failure at the heat-sealed peel interface.

[0005] Therefore, a sealant film for an electricity storage device has been proposed that is configured so that cohesive failure occurs inside the sealant film (sealant layer) (see Patent Document 2). This sealant film consists of at least two layers: a first resin layer mainly made of a propylene-random copolymer, and a second resin layer mainly made of a first elastomer-modified olefin-based resin and comprising at least one polymer component selected from random polypropylene, homopolypropylene, olefin-based elastomer, and styrene-based elastomer.

[0006] In Patent Document 2, first resin layers are disposed on both sides of a second resin layer, one of the first resin layers of a sealant film is used as a laminate layer, and a metal foil layer laminated on a surface outer layer film is laminated to the laminate layer via an adhesive to form an exterior packaging material for an electricity storage device, and the other first resin layer of the sealant film is used as the innermost heat seal layer to process the electricity storage device into a pouch. When the internal pressure of the soft pack for the electricity storage device increases, cohesive failure occurs in the second resin layer inside the sealant film.

[0007] In the above-mentioned packaging materials for power storage devices, if the heat seal strength or lamination strength of the sealant film is too high, it is difficult to stably cause cohesive failure inside the sealant film, and if it is too low, the seal may be broken in situations other than when the internal pressure increases. Therefore, it is necessary to adjust the seal strength within a predetermined range. However, with conventional sealant films, it has been difficult to appropriately adjust the lamination strength between the laminate layer and the metal foil layer such as aluminum foil. Furthermore, other properties such as blocking resistance are not necessarily sufficient, making it difficult to obtain a high-quality sealant film in all required performance aspects. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-176690 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-76510 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been proposed in light of the above circumstances, and provides a polypropylene-based sealant film and an exterior material for a storage battery device that have excellent and well-balanced performance in all aspects of heat seal strength, whitening resistance, heat resistance, lamination strength, and blocking resistance, and that are capable of appropriate cohesive failure at the heat seal peel interface. [Means for solving the problem]

[0010] That is, the invention of claim 1 is a polypropylene-based sealant film having a laminate layer, a base layer, and a heat-seal layer, wherein the laminate layer and the heat-seal layer are mainly made of a propylene-ethylene block copolymer or a propylene homopolymer, the base layer is mainly made of a propylene-ethylene block copolymer, and satisfies the following a1, a2, and a3: (a1): the weight-average molecular weight of the xylene-soluble portion of the propylene-ethylene block copolymer is 100,000 to 600,000 as measured by gel permeation chromatography (GPC), and (a2): the propylene-ethylene block copolymer satisfies JIS K (a2): the melt flow rate (MFR) (230°C, 2.16 kg load) measured in accordance with JIS No. 7210-1(2014) is 1 to 10 g / 10 min, and (a3): the ethylene content of the xylene soluble matter of the propylene-ethylene block copolymer is 10 to 70 wt %, and the base layer contains 5 to 30 wt % of an ethylene-α-olefin random copolymer elastomer. the laminate layer contains at least 30% by weight of a propylene-α-olefin random copolymer, the base layer contains at least 10% by weight of a propylene-α-olefin random copolymer, and the heat seal layer contains at least 15% by weight of a propylene-α-olefin random copolymer. The present invention relates to a polypropylene sealant film characterized by the above-mentioned.

[0011] The invention of claim 2 relates to the polypropylene-based sealant film according to claim 1, wherein the laminate layer is mainly made of a propylene-ethylene block copolymer.

[0012] The invention of claim 3 relates to the polypropylene-based sealant film according to claim 1 or 2, wherein the heat seal layer is mainly composed of a propylene-ethylene block copolymer.

[0013] The invention of claim 4 relates to the polypropylene-based sealant film according to claim 2 or 3, wherein the propylene-ethylene block copolymer is produced using one of the following catalysts: a magnesium-supported catalyst containing magnesium, a halogen, titanium, and an electron donor as catalytic components; a catalyst consisting of a solid catalyst component containing titanium trichloride as a catalyst and an organoaluminum; and a metallocene catalyst; and the melt flow rate (MFR) measured in accordance with JIS K 7210-1 (2014) (230°C, 2.16 kg load) is 1 to 10 g / 10 min.

[0014] Claim 5 The invention of claim 1, wherein the laminate layer and the heat seal layer are mainly made of propylene homopolymer. 1 The present invention relates to the polypropylene sealant film described in 1.

[0015] Claim 6 The invention is as set forth in claims 1 to 5 The present invention relates to an exterior packaging material for a power storage device, which is a laminate comprising the polypropylene sealant film according to any one of the above items 1 to 4, a metal foil layer, and an outer layer film, wherein the heat seal layer of the polypropylene sealant film is arranged on the innermost layer side, and the outer layer film is arranged on the outermost layer side.

[0016] Claim 7 The invention of claim 1 is characterized in that the base layer of the polypropylene sealant film is broken when the heat seal is peeled off. 6 The present invention relates to the packaging material for a power storage device described in 1. [Effects of the Invention]

[0017] According to the invention of claim 1, the polypropylene sealant film has a laminate layer, a base layer, and a heat seal layer, wherein the laminate layer and the heat seal layer are mainly made of a propylene-ethylene block copolymer or a propylene homopolymer, the base layer is mainly made of a propylene-ethylene block copolymer, and satisfies the following a1, a2, and a3: (a1): the weight average molecular weight of the xylene soluble matter of the propylene-ethylene block copolymer is 100,000 to 600,000 as measured by gel permeation chromatography (GPC), and (a2): the propylene-ethylene block copolymer satisfies JIS K (a2): the melt flow rate (MFR) (230°C, 2.16 kg load) measured in accordance with JIS No. 7210-1(2014) is 1 to 10 g / 10 min, and (a3): the ethylene content of the xylene soluble matter of the propylene-ethylene block copolymer is 10 to 70 wt %, and the base layer contains 5 to 30 wt % of an ethylene-α-olefin random copolymer elastomer. the laminate layer contains at least 30% by weight of a propylene-α-olefin random copolymer, the base layer contains at least 10% by weight of a propylene-α-olefin random copolymer, and the heat seal layer contains at least 15% by weight of a propylene-α-olefin random copolymer. Therefore, it has a well-balanced performance in all areas: heat seal strength, whitening resistance, heat resistance, lamination strength, and blocking resistance, and it can also properly cause cohesive failure at the heat seal peeling interface. Furthermore, the interlaminar strength of each layer is improved.

[0018] According to the polypropylene sealant film of the invention of claim 2, in the invention of claim 1, the laminate layer is mainly composed of a propylene-ethylene block copolymer, so sufficient adhesive strength can be obtained between the base material layers, and excellent laminate strength can be obtained with respect to metal foil layers, etc.

[0019] According to the polypropylene sealant film of the invention of claim 3, in the invention of claim 1 or 2, the heat seal layer is mainly composed of a propylene-ethylene block copolymer, thereby achieving better blocking resistance.

[0020] According to the polypropylene sealant film of the invention of claim 4, in the invention of claim 2 or 3, the propylene-ethylene block copolymer is produced using any one of a magnesium-supported catalyst containing magnesium, a halogen, titanium, and an electron donor as catalytic components, a catalyst consisting of a solid catalyst component catalyzed by titanium trichloride and an organoaluminum, and a metallocene catalyst, and has a melt flow rate (MFR) measured in accordance with JIS K 7210-1 (2014) (230°C, 2.16 kg load) of 1 to 10 g / 10 min, thereby achieving more suitable film performance.

[0021] Claim 5 According to the polypropylene sealant film of the invention, 1 In the invention, since the laminate layer and the heat seal layer are mainly made of propylene homopolymer, it is possible to improve heat resistance.

[0022] Claim 6 According to the packaging material for an electricity storage device according to the present invention, claims 1 to 5 1. A laminate comprising the polypropylene sealant film according to any one of claims 1 to 9, a metal foil layer, and an outer layer film, wherein the heat seal layer of the polypropylene sealant film is arranged on the innermost layer side and the outer layer film is arranged on the outermost layer side, thereby achieving appropriate sealing strength and protective performance.

[0023] Claim 7 According to the invention of the packaging material for a power storage device, 6 In the invention, the base layer of the polypropylene sealant film is broken when the heat seal is peeled off, so that cohesive failure can be appropriately caused when the internal pressure of the electricity storage device increases. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view of a polypropylene sealant film according to one embodiment of the present invention. [Figure 2]FIG. 2 is a schematic cross-sectional view of an exterior packaging material for a power storage device using the sealant film of FIG. [Figure 3] FIG. 2 is a schematic cross-sectional view of the electricity storage device. DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1 shows a polypropylene sealant film 10 according to one embodiment of the present invention, which comprises a laminate layer 20, a base layer 30, and a heat-seal layer 40. This sealant film 10 is produced by a known production method such as the T-die method. The sealant film 10 of the present invention is produced without stretching. Unstretched films are preferred because they are less susceptible to whitening and have high heat-seal strength due to the suppression of stretching, which reduces the film's orientation. This unstretched film also includes films that have been stretched unavoidably during production.

[0026] This sealant film 10 is suitable for use as a material for the exterior packaging of an electricity storage device such as a soft-pack type lithium-ion battery. For example, the exterior packaging material 50 for an electricity storage device shown in Fig. 2 is composed of a laminate including the sealant film 10, a metal foil layer 60, and an outer layer film 70, and is used by being molded into a predetermined shape by known drawing or the like as an exterior packaging material for an electricity storage device such as a lithium-ion battery. The resin composition of the sealant film 10 and the exterior packaging material 50 for an electricity storage device will be described below.

[0027] The laminate layer 20 corresponds to one surface layer of the sealant film 10, and is the surface onto which a laminate such as a metal foil or another resin film is laminated during use. The laminate layer 20 is mainly composed of a propylene-ethylene block copolymer or a propylene homopolymer. The laminate layer 20 is preferably subjected to a surface treatment such as a corona treatment, a flame treatment, or a plasma treatment to improve adhesion to other films.

[0028] The propylene-ethylene block copolymer is a composition comprising a propylene-based polymer component and a propylene-ethylene random copolymer component. The melt flow rate (MFR) of the propylene-ethylene block copolymer is not particularly limited, but for example, the MFR (230°C, 2.16 kg load) measured in accordance with Method A of JIS K 7210-1 (2014) is 0.1 to 20 g / 10 min, more preferably 1 to 10 g / 10 min. Furthermore, preferred catalysts used in the production of this propylene-ethylene block copolymer include magnesium-supported catalysts containing magnesium, halogen, titanium, and an electron donor as catalytic components; catalysts containing a titanium trichloride-catalyzed solid catalyst component and organoaluminum; and metallocene catalysts.

[0029] Propylene homopolymers can be obtained using a highly stereoregular polymerization catalyst. Examples of highly stereoregular polymerization catalysts include Ziegler-Natta catalysts using titanium compounds prepared from starting materials such as titanium chloride or alkoxytitanium, and Kaminsky catalysts using metallocene compounds. The melt flow rate (MFR) of this propylene homopolymer is not particularly limited, but should preferably be 0.1 to 20 g / 10 min, more preferably 1 to 10 g / 10 min, measured at 230°C under a 2.16 kg load according to Method A of JIS K 7210-1 (2014).

[0030] Conventional laminate layers are composed of resins primarily composed of propylene-random copolymers, such as propylene-ethylene random copolymers. Slip agents and low-molecular-weight components typically bleed out into the laminate layer, impairing adhesion between the laminate layer and the adhesive and potentially reducing laminate strength. By using a propylene homopolymer with higher crystallinity than conventional propylene-random copolymers, the bleed-out of slip agents and low-molecular-weight components can be suppressed, resulting in superior laminate strength. Furthermore, the copolymer components contained in propylene-ethylene block copolymers and propylene-random copolymers have the property of enhancing compatibility with adhesives. In particular, propylene-ethylene block copolymers, due to their high copolymer component content, can achieve superior laminate strength.

[0031] The base layer 30 is a layer mainly made of a propylene-ethylene block copolymer, satisfies the following (a1), (a2), and (a3), and contains 5 to 30% by weight of an ethylene-α-olefin random copolymer elastomer.

[0032] As (a1), the xylene-soluble portion of the propylene-ethylene block copolymer of the base layer 30 is separated. The weight-average molecular weight of the resin component in the xylene-soluble portion is determined by measuring the xylene-soluble portion using gel permeation chromatography (GPC). This weight-average molecular weight is in the range of 100,000 to 600,000. The xylene-soluble portion is considered to be an elastomer component contained in the propylene-ethylene block copolymer that dissolves in xylene. Therefore, the content of the elastomer component can be estimated from the weight-average molecular weight of the xylene-soluble portion.

[0033] Due to the properties of the propylene-ethylene block copolymer, if the weight-average molecular weight of the xylene-soluble portion is below 100,000, good heat-sealing performance is difficult to achieve, and cohesive failure at the heat-seal peel interface is likely to decrease. If the weight-average molecular weight exceeds 600,000, the haze value of the resulting polypropylene sealant film before and after stretching deteriorates. In other words, whitening occurs during extrusion molding, which is undesirable. Therefore, a weight-average molecular weight of 600,000 is the upper limit. Therefore, the above weight-average molecular weight range is determined from the viewpoint of defining the properties of the propylene-ethylene block copolymer.

[0034] As for (a2), the MFR (230°C, 2.16 kg load) of the propylene-ethylene block copolymer measured in accordance with Method A of JIS K 7210-1 (2014) is 1 to 10 g / 10 min. If the melt flow rate value is less than 1 g / 10 min, the resin has poor fluidity. This results in reduced film formability. If the melt flow rate value exceeds 10 g / 10 min, the resin has excessive fluidity. Furthermore, the impact resistance of the resulting film is likely to decrease due to softening. Therefore, based on the trends in the examples described below, the melt flow rate under the above conditions is in the range of 1 to 10 g / 10 min.

[0035] As for (a3), the ethylene content of the xylene-soluble portion of the propylene-ethylene block copolymer is in the range of 10 to 70% by weight. The ethylene content is an index that relativizes the proportion of ethylene skeletons in the resin component of the xylene-soluble portion. For example, it can be calculated based on the absorbance attributable to ethylene units and the absorbance attributable to propylene units in an infrared (IR) spectrum. Considering the ethylene content of the resin component contained in the xylene-soluble portion is useful for understanding heat resistance, etc. If the ethylene content in the xylene-soluble portion is less than 10% by weight, good heat-sealing performance is difficult to achieve. If the ethylene content in the xylene-soluble portion is more than 70% by weight, the heat resistance of the film is reduced. Therefore, the ethylene content of the xylene-soluble portion is in the above-mentioned range.

[0036] The ethylene-α-olefin random copolymer elastomer is a low-crystalline or amorphous copolymer elastomer, a copolymer of ethylene and an α-olefin copolymerizing monomer. The ethylene-α-olefin random copolymer elastomer is the component that primarily causes cohesive failure at the heat seal peel interface of the sealant film 10. This is because the ethylene-α-olefin random copolymer elastomer is contained in a resin layer primarily composed of a propylene-ethylene block copolymer, forming a sea-island structure. This sea-island structure makes it possible to cause cohesive failure at the heat seal peel interface in the base layer 30. Therefore, the ethylene-α-olefin random copolymer elastomer satisfies the following (b1), (b2), and (b3):

[0037] As for (b1), the density of the ethylene-α-olefin random copolymer elastomer is 0.860 to 0.895 g / cm 3 The density is 0.860 g / cm 3 If the density is less than 0.895g / cm, the melting point of the resin tends to decrease, increasing heat resistance. 3 If the density exceeds this range, the cohesive failure property of the heat seal peel interface may decrease. Therefore, it is important to strike a balance between these two, and the density of the ethylene-α-olefin random copolymer elastomer is specified within the above range.

[0038] As for (b2), the MFR (190°C, 2.16 kg load) of the ethylene-α-olefin random copolymer elastomer measured in accordance with JIS K 7210-1 (2014) is 0.5 to 10.0 g / 10 min. If the MFR of the resin is less than 0.5 g / 10 min, the content of high molecular weight components will be high. If the MFR exceeds 10.0 g / 10 min, the content of high molecular weight components will be low. Therefore, taking into account the formability of the film and the heat resistance of the sealant film 10, the preferred MFR of the ethylene-α-olefin random copolymer elastomer is in the above range.

[0039] As for (b3), the ethylene-α-olefin random copolymer elastomer is a random copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms. Specific examples of α-olefins include propylene, 1-butene, 1-pentene, 1-heptene, and 1-octene. If the α-olefin has fewer than 3 carbon atoms, it does not exist as a comonomer, and the resin is not viable. If the carbon number exceeds 8, the compatibility with other propylene-ethylene copolymers decreases due to the influence of the comonomer portion. Therefore, the ethylene-α-olefin random copolymer elastomer satisfies the above conditions. From the viewpoints of heat seal strength and cohesive failure at the heat seal peel interface, 1-butene is particularly preferred as the α-olefin.

[0040] The blending ratio of the ethylene-α-olefin random copolymer elastomer in the base layer 30 is 5 to 30% by weight. If the blending ratio is less than 5% by weight, there is a risk that cohesive failure at the heat seal peel interface will not occur. If it exceeds 30% by weight, there is a risk that heat resistance will decrease. Therefore, the blending ratio of the ethylene-α-olefin random copolymer elastomer is set to the above range in order to strike a balance between cohesive failure at the heat seal peel interface and heat resistance.

[0041] The heat seal layer 40 corresponds to the surface layer on the other side of the sealant film 10, and is the surface that is bonded to the electrode members of the electricity storage device, other films, etc., during use. The heat seal layer 40 is mainly composed of a propylene-ethylene block copolymer or a propylene homopolymer, similar to the laminate layer 20. The heat seal layer 40 can also have a lower heat seal temperature by adding an ethylene-α-olefin random copolymer elastomer.

[0042] In the sealant film 10, the main components constituting the laminate layer 20 and the heat seal layer 40 are appropriately selected depending on the required film performance. For example, to increase the adhesive strength between the laminate layer 20 and the base layer 30, the laminate layer 20 is preferably made of a propylene-ethylene block copolymer. To increase the blocking resistance of the sealant film 10, the heat seal layer 40 is preferably made of a propylene-ethylene block copolymer. Furthermore, when both the laminate layer 20 and the heat seal layer 40 are made primarily of a propylene homopolymer, improved heat resistance can be achieved.

[0043] Furthermore, in the sealant film 10, the laminate layer 20, the base layer 30, and the heat-seal layer 40 each preferably contain a propylene-α-olefin random copolymer. The blending ratio of the propylene-α-olefin random copolymer is set appropriately for each of the layers 20, 30, and 40. That is, it is preferred that the laminate layer 20 contains at least 30% by weight of the propylene-α-olefin random copolymer, the base layer 30 contains at least 10% by weight of the propylene-α-olefin random copolymer, and the heat-seal layer 40 contains at least 15% by weight of the propylene-α-olefin random copolymer.

[0044] As described above, the interlaminar strength of each layer 20, 30, 40 is improved by including a predetermined proportion of propylene-α-olefin random copolymer in each layer 20, 30, 40. If the proportion of propylene-α-olefin random copolymer in each layer 20, 30, 40 is too low, the heat seal strength may be reduced. On the other hand, if the proportion of propylene-α-olefin random copolymer in each layer 20, 30, 40 is too high, the cohesive failure may not occur properly. The upper limit of the proportion of propylene-α-olefin random copolymer is not particularly limited, as long as it is less than the proportion of the main component of each layer 20, 30, 40.

[0045] The thickness of the sealant film 10 is not particularly limited, but is preferably about 20 to 150 μm, more preferably 20 to 100 μm. The thickness ratio of each layer of the sealant film 10 is, for example, 10 to 33.3% for the laminate layer, 33.4 to 80% for the base layer 30, and 10 to 33.3% for the heat seal layer.

[0046] Additives such as antiblocking agents, slip agents, antistatic agents, antioxidants, neutralizing agents, and colorants may be added to each layer constituting the sealant film 10 as needed, as long as they do not impair properties such as laminate strength.

[0047] In conventional sealant films, heat resistance and whitening resistance are imparted by constructing the laminate layer and heat seal layer mainly from a propylene-random copolymer and the base layer mainly from a propylene-ethylene block copolymer, or by constructing the base layer mainly from an elastomer-modified olefin resin and also containing random polypropylene, homopolypropylene, etc., cohesive failure can occur within the sealant film. However, in the case of the former sealant film, the adhesive strength of each layer is poor, making it difficult to adjust the laminate strength, and in the case of the latter sealant film, other properties such as blocking resistance are insufficient, resulting in a film lacking in some film properties.

[0048] In contrast, as described above, the polypropylene sealant film 10 of the present invention has resins constituting each layer, with the laminate layer 20 and heat seal layer 40 primarily composed of a propylene-ethylene block copolymer or a propylene homopolymer, and the base layer 30 primarily composed of a propylene-ethylene block copolymer. This ensures sufficient adhesive strength between the laminate layer 20 and the base layer 30, providing excellent lamination strength to the metal foil layer 60 and the like, while also imparting excellent blocking resistance to the heat seal layer 40. Furthermore, other film properties are not impaired. Therefore, a well-balanced sealant film with excellent overall performance is obtained.

[0049] As shown in Fig. 2, the packaging material 50 for a power storage device is a laminate including a polypropylene sealant film 10, a metal foil layer 60, and an outer layer film 70, with the respective layers laminated via adhesive layers 80, 85. As shown in Fig. 3, this packaging material 50 for a power storage device is used as a packaging material for a power storage device 100, and is configured to be molded (draw-molded) into a desired shape and size and to cover an electrode member 110 by pouch processing or the like. In this case, the heat seal layer 40 of the polypropylene sealant film 10 is arranged on the innermost layer side, and the outer layer film 70 is arranged on the outermost layer side.

[0050] The metal foil layer 60 is a layer having water vapor barrier properties that prevent moisture from penetrating into the electricity storage device 100. The metal foil layer 60 also has extensibility for deep drawing. This metal foil layer 60 is made of an appropriate metal foil such as aluminum or stainless steel. From the viewpoints of mass (specific gravity), moisture resistance, processability, cost, etc., aluminum foil is preferred. The thickness of the metal foil layer 60 is not particularly limited, but from the viewpoints of barrier properties, pinhole resistance, processability, etc., it is preferably about 9 to 200 μm, and more preferably 15 to 100 μm.

[0051] The metal foil layer 60 is preferably subjected to a corrosion prevention treatment to form a corrosion prevention treatment layer 90 as needed. The corrosion prevention treatment layer 90 is a layer that prevents corrosion of the metal foil layer 60 due to the electrolytic solution or hydrofluoric acid generated by the reaction of the electrolytic solution with water, and is formed on the inner layer side of the metal foil layer 60 (the sealant film 10 side).

[0052] Methods for forming the corrosion-resistant treatment layer 90 include, for example, a combination of degreasing, hydrothermal conversion treatment, anodizing, and chemical conversion treatment. Alternatively, the corrosion-resistant treatment layer 90 can be formed solely by a coating process. Examples of coating processes include using a sol of a rare earth oxide, such as cerium oxide, with an average particle size of 100 nm or less, which has an aluminum corrosion inhibitor effect and is environmentally friendly. This allows for the provision of corrosion protection to metal foils, such as aluminum foil, using a standard coating process. Furthermore, various polymer-based coating agents may be applied to improve adhesion between the corrosion-resistant treatment layer 90 and adjacent layers, or to provide various functionalities. The corrosion-resistant treatment layer 90 may have either a single-layer structure or a multi-layer structure.

[0053] The corrosion prevention treatment layer 90, whether it is a single-layer structure or a multi-layer structure, has a mass per unit area of ​​0.005 to 0.200 g / m 2 is preferable, and 0.010 to 0.100 m 2 is more preferable. If the mass per unit area is too small, the corrosion prevention function may not be sufficiently imparted. Also, if the mass per unit area is too large, the improvement in the corrosion prevention function will not be observed, which is not preferable. The thickness of the corrosion prevention treatment layer 90 can be calculated from its specific gravity.

[0054] The outer layer film 70 is a layer that provides protective properties such as heat resistance in the sealing process during the production of the energy storage device 100 and measures against pinholes during processing and distribution. The outer layer film 70 is preferably an insulating resin film, such as a stretched or unstretched polyester film, polyamide film, or polypropylene film. These films may be used as a single layer or as a multilayer film having two or more layers laminated together. The thickness of the outer layer film 70 is preferably about 2 to 50 μm from the viewpoints of pinhole resistance, insulation, deep-draw formability, and the like. If the outer layer film 70 is too thin, sufficient protective properties such as pinhole resistance and insulation may not be obtained. If the outer layer film 70 is too thick, deep-draw formability may be reduced.

[0055] The adhesive layers 80 and 85 are layers that improve the adhesiveness of each layer. The adhesive layers 80 and 85 are not particularly limited, but examples include polyurethane adhesives, polyester polyurethane adhesives, and polyether polyurethane adhesives. Furthermore, for the adhesive layer 85 interposed on the inner layer side (sealant film 10 side) of the metal foil layer 60, a polyolefin-based adhesive that swells little with the electrolyte is preferably used. The thicknesses of the adhesive layers 80 and 85 are not particularly limited, but it is preferable that the adhesive layer 80 on the outer layer side (outer layer film 70 side) of the metal foil layer 60 be approximately 1 to 10 μm thick, and the adhesive layer 85 on the inner layer side (sealant film 10 side) be approximately 1 to 6 μm thick.

[0056] Next, an example of a method for manufacturing an exterior material for a power storage device will be described. The method for manufacturing an exterior material for a power storage device includes a corrosion prevention treatment step, a first lamination step, and a second lamination step, and optionally a heat treatment step.

[0057] The corrosion prevention treatment step is a step of forming a corrosion prevention treatment layer 90 by subjecting the metal foil layer 60 to a corrosion prevention treatment. In this example, the corrosion prevention treatment layer 90 is formed on one side of the metal foil layer 60. Corrosion prevention treatment methods include degreasing, hydrothermal denaturation treatment, anodizing treatment, chemical conversion treatment, and application of a coating agent with corrosion prevention properties. The degreasing treatment is performed by a spray method or immersion method, the hydrothermal denaturation treatment and anodizing treatment are performed by an immersion method, and the chemical conversion treatment is performed by an immersion method, spray method, coating method, etc., depending on the type of chemical conversion treatment. Furthermore, various coating methods such as gravure coating, reverse coating, roll coating, and bar coating can be used for coating the coating agent. Regardless of the method, the coating amount of the coating agent is 0.005 to 0.200 g / m. 2 is preferable, and 0.010 to 0.100 g / m 2 Furthermore, if dry curing is required, it is performed at a metal foil layer (base material) temperature of 60 to 300°C depending on the drying conditions of the corrosion prevention treatment layer 90 used.

[0058] The first lamination step is a step of bonding (laminating) the metal foil layer 60 and the outer layer film 70 via the outer layer side adhesive layer 80. In this example, the outer layer film 70 is laminated to the metal foil layer 60 on the side where the corrosion prevention treatment layer 90 is not provided. Techniques such as dry lamination, non-solvent lamination, and wet lamination are used as the bonding method. The thickness of the outer layer side adhesive layer 80 is set to 1 to 10 μm.

[0059] The second lamination step is a step of bonding (laminating) the metal foil layer 60 and the sealant film 10 via the inner layer side adhesive layer 85. In this example, the sealant film 10 is laminated onto the corrosion prevention treatment layer 90 provided on the metal foil layer 60. The bonding method may be dry lamination, non-solvent lamination, wet lamination, or the like. The thickness of the inner layer side adhesive layer 85 is set to 1 to 6 μm.

[0060] The heat treatment step is a step of aging (curing) the laminate (50) obtained through the above steps. By aging the laminate, it is possible to promote adhesion between the outer film 70, adhesive layer 80, metal foil layer 60, corrosion prevention treatment layer 90, adhesive layer 85, and sealant film 10. The aging treatment is carried out at a temperature ranging from room temperature to 100°C, and the aging time is, for example, about 1 to 10 days.

[0061] The laminate thus formed is provided as an electrical storage device packaging material 50. For example, it can be suitably used in electrical storage devices such as secondary batteries, such as lithium ion batteries, nickel-metal hydride batteries, and lead-acid batteries, and electrochemical capacitors, such as electric double layer capacitors. In particular, the electrical storage device packaging material 50 is suitable as a packaging material for lithium ion batteries. [Example]

[0062] [Production of exterior materials for energy storage devices] In producing the electrical storage device packaging materials of Prototype Examples 1 to 52, first, the materials described below were melted and kneaded, extruded by a T-die method, and cooled with a cooling roll to produce a 40 μm-thick (5 μm-thick laminate layer, 30 μm-thick base layer, 5 μm-thick heat-seal layer) unstretched polypropylene sealant film corresponding to the electrical storage device packaging materials of Prototype Examples 1 to 52. Next, each produced sealant film was combined with a 15 μm-thick nylon film as the outer layer film, a 9 μm-thick aluminum foil as the metal foil layer, and a two-component curing polyurethane adhesive as each adhesive layer. The outer layer film was dry-laminated to one side of the metal foil layer via the adhesive layer, and then the sealant film was dry-laminated to the other side of the metal foil layer via the adhesive layer. The resulting mixture was aged at 40° C. for 2 days to obtain electrical storage device packaging materials of Prototype Examples 1 to 52.

[0063] [Materials used] The following resins were used as the resin compositions for the laminate layer, base layer, and heat seal layer. The melt flow rate (MFR) was measured in accordance with JIS K 7210 (2014) at 230°C and 2.16 kg or 190°C and 2.16 kg.

[0064] Resin A1: Propylene homopolymer, density 0.9g / cm 3 , Melting point 166℃, MFR (230℃): 7.5g / 10min

[0065] Resin B1: Propylene-ethylene block copolymer, density 0.9 g / cm 3 , Melting point 165℃, MFR (230℃): 3.5g / 10min Resin B2: Propylene-ethylene block copolymer, density 0.9 g / cm 3 , Melting point 160℃, MFR (230℃): 8.5g / 10min Resin B3: Propylene-ethylene block copolymer, density 0.9 g / cm 3 , Melting point 161℃, MFR (230℃): 2.5g / 10min Resin B4: Propylene-ethylene block copolymer, density 0.9 g / cm 3 , Melting point 163℃, MFR (230℃): 8g / 10min

[0066] Resin C1: Propylene-ethylene random copolymer, density 0.9 g / cm 3 , Melting point 130℃, MFR (230℃): 7g / 10min Resin C2: Propylene-ethylene-butene random copolymer, density 0.9 g / cm 3 , Melting point 140℃, MFR (230℃): 8g / 10min Resin C3: Propylene-ethylene-random copolymer, density 0.9 g / cm 3 , Melting point 134℃, MFR (230℃): 7g / 10min

[0067] Resin D1: Linear low-density polyethylene, density 0.919 g / cm 3 , Melting point 118℃, MFR (190℃): 5g / 10min

[0068] Resin E1: Ethylene-α-olefin random copolymer elastomer, density 0.89 g / cm 3 , Melting point 66℃, MFR (190℃): 4g / 10min, Comonomer carbon number 4 Resin E2: Ethylene-α-olefin random copolymer elastomer, density 0.89 g / cm 3 Melting point 66℃, MFR (190℃): 1g / 10min, Comonomer carbon number 4 Resin E3: Ethylene-α-olefin random copolymer elastomer, density 0.86 g / cm 3 , Melting point 38℃, MFR (190℃): 3g / 10min, Comonomer carbon number 3

[0069] Resin F1: Propylene-α-olefin random copolymer elastomer, density 0.90 g / cm 3 Melting point: 83°C, MFR (190°C): 3g / 10min, Comonomer carbon number: 4

[0070] Resin G1: Butene-α-olefin random copolymer elastomer, density 0.89 g / cm 3 , Melting point 58℃, MFR(190℃):4g / 10min, Comonomer carbon number 3

[0071] [Prototype 1] Prototype example 1 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 45% by weight of resin A1 and 55% by weight of resin B1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin A1 and 55% by weight of resin B1.

[0072] [Prototype 2] Prototype example 2 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0073] [Prototype 3] Prototype example 3 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B2 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B2 and 45% by weight of resin C1.

[0074] [Prototype 4] Prototype example 4 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B3 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B3 and 45% by weight of resin C1.

[0075] [Prototype 5] Prototype example 5 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is 100% by weight of resin B1, the base material layer is 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is 100% by weight of resin B1.

[0076] [Prototype 6] Prototype example 6 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 80% by weight of resin B1 and 20% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 80% by weight of resin B1 and 20% by weight of resin C1.

[0077] [Prototype 7] Prototype example 7 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 70% by weight of resin B1 and 30% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 70% by weight of resin B1 and 30% by weight of resin C1.

[0078] [Prototype 8] Prototype example 8 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin D1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0079] [Prototype 9] Prototype example 9 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1, 35% by weight of resin C1, and 10% by weight of resin D1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0080] [Prototype 10] Prototype example 10 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1, 35% by weight of resin C1, and 10% by weight of resin E1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0081] [Prototype 11] Prototype example 11 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 65% by weight of resin B1, 30% by weight of resin C1, and 5% by weight of resin E1.

[0082] [Prototype 12] Prototype example 12 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 65% by weight of resin B1, 30% by weight of resin C1, and 5% by weight of resin D1.

[0083] [Prototype 13] Prototype example 13 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55 wt% resin B1, 35 wt% resin C1, and 10 wt% resin C2, the base material layer is made of 75 wt% resin B1, 5 wt% resin D1, and 20 wt% resin E1, and the heat seal layer is made of 65 wt% resin B1, 25 wt% resin C1, 5 wt% resin C2, and 5 wt% resin D1.

[0084] [Prototype 14] Prototype example 14 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 25% by weight of resin A1, 55% by weight of resin B1, and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0085] [Prototype 15] Prototype example 15 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin A1 and 45% by weight of resin B1.

[0086] [Prototype 16] Prototype example 16 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin B1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0087] [Prototype 17] Prototype example 17 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin B1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin A1 and 45% by weight of resin B1.

[0088] [Prototype 18] Prototype example 18 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin A1 and 45% by weight of resin C1.

[0089] [Prototype 19] Prototype example 19 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 70% by weight of resin A1 and 30% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin A1 and 45% by weight of resin C1.

[0090] [Prototype 20] Prototype example 20 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E3, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0091] [Prototype 21] Prototype example 21 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 95% by weight of resin B1 and 5% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0092] [Prototype 22] Prototype example 22 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 90% by weight of resin B1 and 10% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0093] [Prototype 23] Prototype example 23 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 85% by weight of resin B1 and 15% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0094] [Prototype 24] Prototype example 24 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 75% by weight of resin B1 and 25% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0095] [Prototype 25] Prototype example 25 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 70% by weight of resin B1 and 30% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0096] [Prototype 26] Prototype example 26 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1, 5% by weight of resin D1, and 15% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0097] [Prototype 27] Prototype example 27 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 75% by weight of resin B1, 5% by weight of resin D1, and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0098] [Prototype 28] Prototype example 28 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 75% by weight of resin B1, 5% by weight of resin C1, and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0099] [Prototype 29] Prototype example 29 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55 wt% resin B1 and 45 wt% resin C1, the base material layer is made of 5 wt% resin A1, 75 wt% resin B1, and 20 wt% resin E1, and the heat seal layer is made of 55 wt% resin B1 and 45 wt% resin C1.

[0100] [Prototype 30] Prototype example 30 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 90% by weight of resin B1 and 10% by weight of resin E2, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0101] [Prototype 31] Prototype example 31 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E2, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0102] [Prototype 32] Prototype example 32 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 100% resin C2 by weight, the base material layer is made of 80% resin B1 and 20% resin E1 by weight, and the heat seal layer is made of 100% resin C1 by weight.

[0103] [Prototype 33] Prototype example 33 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 45% by weight of resin B1 and 55% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0104] [Prototype 34] Prototype example 34 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin E1, and the heat seal layer is made of 100% by weight of resin C1.

[0105] [Prototype 35] Prototype example 35 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 97% by weight of resin B1 and 3% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0106] [Prototype 36] Prototype example 36 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 60% by weight of resin B1 and 40% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0107] [Prototype 37] Prototype example 37 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin F1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0108] [Prototype 38] Prototype example 38 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 80% by weight of resin B1 and 20% by weight of resin G1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0109] [Prototype 39] Prototype example 39 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 45% by weight of resin A1, 45% by weight of resin B1, and 10% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0110] [Prototype 40] Prototype example 40 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 45% by weight of resin B1, 45% by weight of resin C1, and 10% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0111] [Prototype 41] Prototype example 41 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 95% by weight of resin B2 and 5% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0112] [Prototype 42] Prototype example 42 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 95% by weight of resin B4 and 5% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0113] [Prototype 43] Prototype example 43 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 95% by weight of resin B3 and 5% by weight of resin E1, and the heat seal layer is made of 55% by weight of resin B1 and 45% by weight of resin C1.

[0114] [Prototype 44] Prototype example 44 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 55% by weight of resin B1, 25% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin A1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0115] [Prototype 45] Prototype example 45 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 70% by weight of resin B1, 10% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin A1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0116] [Prototype 46] Prototype example 46 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 60% by weight of resin B1, 20% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin A1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0117] [Prototype 47] Prototype example 47 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 50% by weight of resin B1, 30% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin A1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0118] [Prototype 48] Prototype example 48 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 70% by weight of resin A1 and 30% by weight of resin C1, the base material layer is made of 55% by weight of resin B1, 25% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 50% by weight of resin A1, 40% by weight of resin C1, and 10% by weight of resin E1.

[0119] [Prototype 49] Prototype example 49 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 55% by weight of resin B1, 25% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 70% by weight of resin A1, 15% by weight of resin C1, and 15% by weight of resin E1.

[0120] [Prototype Example 50] Prototype example 50 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 55% by weight of resin B1, 25% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin A1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0121] [Prototype 51] Prototype example 51 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin A1 and 45% by weight of resin C1, the base material layer is made of 55% by weight of resin B1, 25% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin B1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0122] [Prototype 52] Prototype example 52 is an exterior material for a storage battery device that uses a sealant film in which the laminate layer is made of 55% by weight of resin B1 and 45% by weight of resin C1, the base material layer is made of 55% by weight of resin B1, 25% by weight of resin C3, and 20% by weight of resin E1, and the heat seal layer is made of 45% by weight of resin B1, 40% by weight of resin C1, and 15% by weight of resin E1.

[0123] Tables 1 to 8 show the resin compositions of the layers of the films constituting the packaging materials for electricity storage devices of Prototype Examples 1 to 52.

[0124] [Table 1]

[0125] [Table 2]

[0126] [Table 3]

[0127] [Table 4]

[0128] [Table 5]

[0129] [Table 6]

[0130] [Table 7]

[0131] [Table 8]

[0132] To evaluate the performance of each sealant film used in the packaging materials for electricity storage devices of Prototype Examples 1 to 52, the coefficient of thermal expansion, the difference in haze value before and after tension, and the blocking strength were measured.

[0133] [Thermal expansion coefficient] A thermal expansion test was conducted on each sealant film corresponding to prototypes 1 to 52, using the resistance to thermal deformation as an indicator of thermal stability (heat resistance). In the thermal expansion test, the deformation (tensile strength) of the film under heat is measured using a thermomechanical analyzer (TMA) in accordance with standards such as JIS K 0129 (2005) and JIS K 7197 (1991, 2012). Therefore, we decided to measure the deformation (tensile strength) of the film under heat using a thermomechanical analyzer (TMA). A thermomechanical analyzer (model number: Q400) manufactured by TA Instruments Japan, Inc. was used for the TMA measurement.

[0134] Each sealant film corresponding to Prototype Examples 1 to 52 was cut into a rectangular test piece (for measuring the coefficient of thermal expansion) measuring 4 mm x 8 mm (width direction x length direction of the film), and the test piece was fixed to the probe of the TMA device with the length direction as the tensile direction. A load of 0.0322 N (tensile direction side) was applied to the test piece, and the length of the test piece (L0) was first read at this point. The test piece was heated from room temperature to 140°C at a temperature rise rate of 5°C / min with the same device, and after reaching 140°C, the temperature was maintained for 2 minutes. After 2 minutes had passed, the length of the test piece after heating to 140°C (L1) was read. During the heating process, a load of 0.0322 N was continuously applied to the test piece in the tensile direction. The lengths of the test piece before and after heating (L0) and (L1) were then substituted into the following equation (i) to calculate the coefficient of thermal expansion (T) from the relationship between the initial length of the test piece and the change in length. E ) (%) was calculated. E The lower the value, the less likely the material is to be thermally deformed (the better the heat resistance), so a measurement result of 13% or less was rated as "excellent (◎)", and a result of more than 13% was rated as "poor (×)".

[0135]

number

[0136] [Difference in haze value before and after tension] When judging the appearance of each sealant film corresponding to prototypes 1 to 52, an optical indicator of whitening is used. In particular, when performing extrusion molding, it is important to understand the changes due to elongation at the bending point. Generally, when a film is subjected to deformation pressure such as elongation, whitening progresses at that point, which tends to deteriorate the appearance. Therefore, the haze value (unit: %) is measured using a haze meter (NDH-4000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136 (2000).

[0137] Each sealant film corresponding to prototype examples 1 to 52 was cut into a rectangular test piece (for haze measurement) measuring 50 mm x 100 mm (width direction x length direction of the film). First, the haze value of this test piece was measured in accordance with the above-mentioned standard. This is the haze value (H0) before stretching. Next, the longitudinal direction of the test piece was fixed to the chuck of a tensile tester. The test piece was stretched at a tensile speed of 200 mm / min until it reached 500% of its length (five times its original length). After this stretching, the haze value of the test piece that had finished stretching was also measured in accordance with the above-mentioned standard. This is the haze value (H1) after stretching. Therefore, the difference in haze value before and after stretching (D H ) in the following formula (ii) "D H = |H1 - H0|". The absolute value was used to take into account the influence of the state of the film before and after stretching. The difference in haze value (D H ) the smaller the value, the less whitening (better whitening resistance), so a measurement result of 10 or less was rated as "excellent (◎)", 30 or less was rated as "good (〇)", and anything greater than 30 was rated as "unacceptable (×)".

[0138]

number

[0139] [Blocking Strength] A blocking strength measurement test was carried out as an index of the ease of peeling when overlapping each sealant film corresponding to prototypes 1 to 52 (blocking resistance). In the blocking strength measurement test, the heat seal layers of each sealant film corresponding to prototypes 1 to 52 were overlapped, and a 4 cm2 After applying a load of 10 N to the sample and leaving it at 40°C for 24 hours, the shear peel strength (blocking strength) was measured using a tensile tester (Shimadzu Corporation, Autograph AGS-X 50N) (N / 4cm 2 ) This shear peel strength represents the shear force that the film exerts when a load is applied to it at a tension tester speed of 200 mm / min. The lower the blocking strength, the easier it is to peel when overlapping, so a measurement result of 5 N / 4 cm 2 Less than 5N / 4cm is "Excellent (◎)" 2 If it was greater than this, it was marked as "Not acceptable (×)".

[0140] Furthermore, to evaluate the performance of the packaging materials for electricity storage devices of Prototype Examples 1 to 52, the lamination strength and heat seal strength were measured, and the appearance of the heat seal peeling interface was also evaluated.

[0141] [Laminate strength] A laminate strength measurement test was conducted to assess the adhesiveness of each layer of the packaging materials for power storage devices in Prototype Examples 1 to 52. In the laminate strength measurement test, a tensile tester (Shimadzu Corporation, EZ-SX) was used in accordance with JIS K 6854-3 (1999) to measure the load at the time of peeling the laminate (packaging material). Test pieces were cut into 15 mm x 200 mm strips from the packaging materials of Prototype Examples 1 to 52. A 50 mm section of the laminate in the longitudinal direction was peeled off from each test piece, opening it into a T-shape in side view. The partially peeled test piece was opened so that the non-laminated portion (the sealant film side) and the laminated film (the outer film, metal foil layer) side were positioned 180° apart, and each was secured to the chuck of the tensile tester. The remaining laminated portion (the laminated adhesive portion) was peeled off by pulling it vertically at a test speed of 200 mm / min. The specimen was peeled off for 100 mm, and the maximum peel load during this period was recorded as the laminate strength (N / 15 mm) of the specimen. Measurement results of 7 N / 15 mm or more were rated as "excellent (◎)", and results of less than 7 N / 15 mm were rated as "unacceptable (×)".

[0142] [Heat seal strength] A heat-seal strength measurement test was conducted to assess the adhesiveness of the heat-sealed surfaces of the exterior packaging materials for power storage devices in Prototype Examples 1 to 52. In the heat-seal strength measurement test, the sealant films (innermost layers) of the exterior packaging materials were first overlapped and heat-sealed using a heat-seal tester (TP-701-B, manufactured by Tester Sangyo Co., Ltd.) at a sealing pressure of 0.3 MPa, a sealing time of 2 seconds, and a sealing temperature of 180°C. The heat-sealed exterior packaging materials were cut into 15 mm widths and peeled using a tensile tester (EZ-SX, manufactured by Shimadzu Corporation) at a peel rate of 200 mm / min. The maximum peel load during this process was recorded as the heat-seal strength (N / 15 mm) of the exterior packaging material. Measurement results of 40 N / 15 mm or greater were rated as "excellent (◎)," 30 N / 15 mm or greater were rated as "good (◯)," and less than 30 N / 15 mm were rated as "unacceptable (×)." If the exterior material was torn during peeling, the measured value at that point was written in parentheses.

[0143] [Appearance of heat seal peeling interface] As an indicator of the cohesive failure of the heat-seal peel interface of the packaging materials for energy storage devices of Prototype Examples 1 to 52, the peel surface of the sealant film of the packaging material (heat-seal peel interface) after the heat-seal strength measurement test was visually observed, and the degree of whitening of the peel surface was judged. If cohesive failure occurred appropriately in the base layer of the sealant film, both sides of the heat-seal peel interface would whiten uniformly. Therefore, the evaluation criteria were as follows: uniform whitening on both sides of the peel surface was rated as "excellent (◎)," no whitening observed on any part of the peel surface was rated as "good (◯)," and almost no whitening observed on the peel surface was rated as "poor (×)." If the packaging material was torn during peeling, it was rated as "not observed (-)."

[0144] Tables 9 to 16 show the test results and evaluations of each sealant film corresponding to the packaging materials for power storage devices of Prototype Examples 1 to 52 and the packaging materials for power storage devices of Prototype Examples 1 to 52. In Tables 9 to 16, the overall evaluation was evaluated as "excellent (◎)" when all the evaluations for each test were "excellent (◎)," "good (◯)" when all were "good (◯)" or above, and "poor (×)" when there was even one "poor (×)" or "not observed (-)."

[0145] [Table 9]

[0146] [Table 10]

[0147] [Table 11]

[0148] [Table 12]

[0149] [Table 13]

[0150] [Table 14]

[0151] [Table 15]

[0152] [Table 16]

[0153] [Results and Discussion] As shown in Tables 1 to 8 and Tables 9 to 16, prototypes 1 to 31 and 44 to 52 received an overall rating of "good (◯)" or better, while prototypes 32 to 43 received an overall rating of "poor (×)." Therefore, we will first consider the differences in performance between the good prototypes 1 to 31 and the bad prototypes 32 to 43 by comparing the configuration of the sealant film for each prototype.

[0154] The defective prototype 32 is compared with the non-defective prototypes 1 to 12 and 15 to 19. The laminate and heat seal layers of prototypes 1 to 12 and 15 to 19 contain 50% by weight or more of either a propylene-ethylene block copolymer or a propylene homopolymer, whereas the laminate and heat seal layers of prototype 32 are composed solely of a propylene-α-olefin copolymer. As a result, prototype 32 lacked lamination strength and blocking strength.

[0155] Furthermore, defective Sample 33 differed from Samples 2, 8 to 10, and 16 in that the propylene-ethylene block copolymer in the laminate layer was less than 50% by weight, and thus the laminate strength performance was insufficient. Defective Sample 34 differed from Samples 2, 11, 12, and 15 in that the heat seal layer was composed only of a propylene-α-olefin copolymer, and thus the blocking strength performance was insufficient.

[0156] As can be seen from a comparison of Prototype Examples 1 to 12, 15 to 19 and Prototype Examples 32 to 34, it is believed that appropriate lamination strength can be obtained by forming the laminate layer of the sealant film primarily from a propylene-ethylene block copolymer or a propylene homopolymer, and that appropriate blocking strength can be obtained by forming the heat seal layer of the sealant film primarily from a propylene-ethylene block copolymer or a propylene homopolymer.

[0157] The proportion of resin E1 (ethylene-α-olefin random copolymer elastomer) in the base layer differs between the good prototypes 2, 21-25 and the bad prototypes 35 and 36. The bad prototype 35 had the minimum proportion of resin E1 in the base layer of 3% by weight, and in the heat seal strength measurement test, the packaging material tore apart during peeling, preventing proper cohesive failure at the heat seal peel interface. The bad prototype 36 had the maximum proportion of resin E1 in the base layer of 40% by weight, resulting in a high thermal expansion coefficient and insufficient heat resistance.

[0158] On the other hand, in the good prototypes 2, 21 to 25, the blending ratio of resin E1 in the base layer was a minimum of 5 wt% in prototype 21 and a maximum of 30 wt% in prototype 25. It was also observed that the lower the blending ratio of resin E1 in the base layer, the higher the heat seal strength, and the higher the blending ratio, the higher the thermal expansion coefficient. Based on good prototypes 2, 21 to 25 and defective prototypes 35 and 36, it appears that the preferred blending ratio of ethylene-α-olefin random copolymer elastomer in the base layer of a sealant film is 5 to 30 wt%.

[0159] Defective Sample 37 differs from non-defective Sample 2 in that it uses resin F1 (propylene-α-olefin random copolymer elastomer) instead of resin E1 (ethylene-α-olefin random copolymer elastomer) in the base layer. Defective Sample 38 also differs from non-defective Sample 2 in that it uses resin G1 (butene-α-olefin random copolymer elastomer) instead of resin E1 (ethylene-α-olefin random copolymer elastomer) in the base layer. In both Samples 37 and 38, the outer packaging material tore during peeling during the heat seal strength measurement test, preventing proper cohesive failure at the heat seal peel interface. Therefore, it is believed that using an ethylene-α-olefin random copolymer elastomer is preferable for properly generating cohesive failure at the heat seal peel interface in the base layer.

[0160] Here, we consider the preferred conditions for the ethylene-α-olefin random copolymer elastomer used in the base layer. Comparing the good-quality samples 2, 20, and 31, sample 2, which used resin E1, and sample 20, which used resin E3, showed uniform whitening on both sides of the heat-sealed peel interface, indicating proper cohesive failure. Sample 31, which used resin E2, showed no whitening in parts of the heat-sealed peel interface, but was generally good. Incidentally, sample 30, which used 10% by weight of resin E2, also showed no whitening in parts of the heat-sealed peel interface, similar to sample 31, but was generally good. Therefore, resins E1, E2, and E3 can all be used effectively.

[0161] The defective prototypes 39 and 40 differ from the non-defective prototypes 14, 26 to 29 in that the resin B1 (propylene-ethylene block copolymer) used in the base layer is not the main component (its blending ratio is higher than that of other resin materials). In both prototypes 39 and 40, the packaging material tore during peeling in the heat seal strength measurement test, and proper cohesive failure at the heat seal peel interface did not occur. Therefore, it is considered preferable for the base layer to be primarily composed of a propylene-ethylene block copolymer.

[0162] The defective prototypes 41 to 43 differ from the non-defective prototype 21 in the type of propylene-ethylene block copolymer that is the main component of the base layer. All of prototypes 41 to 43 had a large difference in haze value before and after tension, and exhibited insufficient whitening resistance. Furthermore, in prototypes 41 and 42, the packaging material tore during peeling in the heat seal strength measurement test, preventing proper cohesive failure at the heat seal peel interface.

[0163] In prototype 13, the laminate layer and heat seal are primarily made of resin B1 (propylene-ethylene block copolymer), and the base layer is primarily made of resin B1 (propylene-ethylene block copolymer) with an appropriate amount of resin E1 (ethylene-α-olefin random copolymer elastomer). In particular, the laminate layer, base layer, and heat seal layer are each composed of three or more types of resin, and good results were obtained in all tests. Therefore, it is believed that well-balanced film performance can be achieved even if multiple types of resins are blended in addition to the main resin in each layer.

[0164] As mentioned above, although Prototypes 35, 37-42 all have high heat seal strength (e.g., 70 N / 15 mm or more), the packaging material tears during peeling. On the other hand, Prototypes 5, 21, 22, 30, and 31, which are good products, have heat seal strength equivalent to that of Prototypes 35, 37-42 (70 N / 15 mm or more), but they also experience appropriate cohesive failure at the heat seal peel interface. This shows that simply having high heat seal strength for a sealant film is not enough; it is important to strike a balance between maintaining a certain seal strength and ensuring that cohesive failure at the heat seal peel interface occurs at the appropriate time. Therefore, the sealant films used in the packaging materials of Prototypes 1-31, which are good products, can be said to have an excellent balance of film performance.

[0165] Next, we will consider prototypes 44 to 52, which contain propylene-α-olefin random copolymer in the laminate layer, base layer, and heat seal layer. All of prototypes 44 to 52 were good products with an overall rating of "Good (〇)" or better, and the following discussion will focus on the tendency for these to exhibit better performance.

[0166] In Examples 44 to 47, the main component of the laminate layer and heat seal layer was propylene homopolymer, and the blending ratio of propylene-α-olefin random copolymer in the base layer was adjusted: 25% by weight for Example 44, 10% by weight for Example 45, 20% by weight for Example 46, and 30% by weight for Example 47. The test results for each example showed that the heat seal strength tended to improve depending on the blending ratio of propylene-α-olefin random copolymer in the base layer.

[0167] Furthermore, in Samples 44 to 46, the heat-sealed peel interface was uniformly whitened, indicating that cohesive failure occurred appropriately. On the other hand, in Sample 47, although whitening was not observed in some parts of the heat-sealed peel interface, cohesive failure generally occurred satisfactorily. Sample 47 has a higher proportion of propylene-α-olefin random copolymer in the base layer than Samples 44 to 46. Therefore, if the proportion of propylene-α-olefin random copolymer in the base layer becomes too high, it is thought that cohesive failure will not occur appropriately.

[0168] In prototype 48, the blending ratio of propylene-α-olefin random copolymer in the laminate layer was reduced compared to prototype 44. In prototype 49, the blending ratio of propylene-α-olefin random copolymer in the heat seal layer was reduced compared to prototype 44. As can be seen from the test results, prototype 44, which has a higher blending ratio of propylene-α-olefin random copolymer in the laminate layer and heat seal layer, exhibits higher laminate strength and heat seal strength than prototypes 48 and 49. Therefore, it is believed that the higher the blending ratio of propylene-α-olefin random copolymer in the laminate layer and heat seal layer, the better the laminate strength and heat seal strength will be.

[0169] In Prototype 50, the main component of the laminate layer was changed to a propylene-ethylene block copolymer compared to Prototype 44, in Prototype 51 the main component of the heat seal layer was changed to a propylene-ethylene block copolymer compared to Prototype 44, and in Prototype 52 the main components of the laminate layer and heat seal layer were changed to a propylene-ethylene block copolymer compared to Prototype 44. As can be seen from the test results, Prototypes 50 and 52, in which the main component of the laminate layer is a propylene-ethylene block copolymer, were found to have higher laminate strength than Prototype 44, in which the main component of the laminate layer is a propylene homopolymer. Therefore, it is believed that excellent laminate strength can be obtained by using a propylene-ethylene block copolymer as the main component of the laminate layer.

[0170] As shown and explained above, the polypropylene-based sealant film of the present invention has a laminate layer, a base layer, and a heat seal layer, and the base layer is mainly composed of a propylene-ethylene block copolymer and contains 5 to 30 wt % of an ethylene-α-olefin random copolymer elastomer, and when the heat seal is peeled off, the base layer is ruptured, causing cohesive failure at the heat seal peeling interface.

[0171] In particular, the sealant film of the present invention has a laminate layer or heat seal layer made mainly of a propylene-ethylene block copolymer or a propylene homopolymer, which is different from the propylene-random copolymer used in conventional sealant films. Therefore, the sealant film of the present invention improves the laminate strength, blocking resistance, and other properties that have been lacking in conventional sealant films without compromising other properties. Therefore, the sealant film of the present invention has a well-balanced performance that is excellent in all of heat seal strength, whitening resistance, heat resistance, laminate strength, and blocking resistance, and can also appropriately cause cohesive failure at the heat seal peel interface.

[0172] In an electrical storage device packaging material using this sealant film, the heat seal layer of the sealant film is positioned on the innermost layer side, and the outer layer film is positioned on the outermost layer side, so that appropriate sealing strength and protective performance can be obtained. In particular, in an electrical storage device packaging material using the sealant film of the present invention, the base layer of the sealant film is ruptured when the heat seal is peeled off, so that cohesive failure can be appropriately caused when the internal pressure of the electrical storage device increases. [Industrial Applicability]

[0173] As described above, the polypropylene-based sealant film of the present invention has well-balanced and excellent film properties and can appropriately cause cohesive failure at the heat-seal peel interface, making it suitable for use as a material for packaging materials for electricity storage devices. Furthermore, packaging materials for electricity storage devices using this sealant film are promising as alternatives to conventional packaging materials for electricity storage devices. [Explanation of symbols]

[0174] 10 Polypropylene sealant film 20 laminate layers 30 Base material layer 40 Heat seal layer 50. Exterior material for power storage device (laminate) 60 Metal foil layer 70 outer film 80,85 Adhesive layer 90 Corrosion prevention treatment layer 100 Electricity storage device 110 Electrode material

Claims

1. A polypropylene sealant film having a laminate layer, a base layer, and a heat seal layer, the laminate layer and the heat seal layer are mainly composed of a propylene-ethylene block copolymer or a propylene homopolymer; The base layer is mainly composed of a propylene-ethylene block copolymer and satisfies the following a1, a2, and a3: (a1): the weight average molecular weight of the xylene-soluble portion of the propylene-ethylene block copolymer is 100,000 to 600,000 as measured by gel permeation chromatography (GPC); (a2): The propylene-ethylene block copolymer has a melt flow rate (MFR) (230°C, 2.16 kg load) of 1 to 10 g / 10 min as measured in accordance with JIS K 7210-1 (2014), (a3): the ethylene content of the xylene-soluble matter of the propylene-ethylene block copolymer is 10 to 70% by weight; the substrate layer contains 5 to 30% by weight of an ethylene-α-olefin random copolymer elastomer; The laminate layer contains at least 30% by weight of a propylene-α-olefin random copolymer, the base layer contains at least 10% by weight of a propylene-α-olefin random copolymer, and the heat seal layer contains at least 15% by weight of a propylene-α-olefin random copolymer. A polypropylene sealant film characterized by:

2. 2. The polypropylene sealant film according to claim 1, wherein the laminate layer is mainly composed of a propylene-ethylene block copolymer.

3. 3. The polypropylene sealant film according to claim 1, wherein the heat seal layer is mainly composed of a propylene-ethylene block copolymer.

4. The polypropylene sealant film according to claim 2 or 3, wherein the propylene-ethylene block copolymer is produced using any one of a magnesium-supported catalyst containing magnesium, a halogen, titanium, and an electron donor as a catalyst component, a catalyst containing a solid catalyst component catalyzed by titanium trichloride and an organoaluminum, and a metallocene catalyst, and has a melt flow rate (MFR) (230°C, 2.16 kg load) of 1 to 10 g / 10 min as measured in accordance with JIS K 7210-1 (2014).

5. 2. The polypropylene sealant film according to claim 1, wherein the laminate layer and the heat seal layer are mainly composed of a propylene homopolymer.

6. 6. An exterior packaging material for a storage battery device, comprising: a laminate comprising the polypropylene-based sealant film according to claim 1, a metal foil layer, and an outer layer film, wherein the heat seal layer of the polypropylene-based sealant film is disposed on the innermost layer side, and the outer layer film is disposed on the outermost layer side.

7. The packaging material for a power storage device according to claim 6 , wherein the base layer of the polypropylene sealant film is ruptured when the heat seal is peeled off.

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