KR101494811B1 - Process for producing sealing film, and sealing film - Google Patents

Abstract

A method for producing a sealing film (1) sandwiched between an electrode (11) as a power generation element housed in a bag (20) and a marginal edge of a bag (20) is characterized in that an acid - modified polyolefin resin (A) Melting and kneading both the resin B having a functional group capable of reacting with the carboxyl group of A and the resin B to knead the resin B with the resin C to chemically bond the functional group of the resin B to the carboxyl group of the resin A, A heat resistant layer forming step of forming the heat resistant layer 3, an adhesive layer forming step of forming an electrode adhesive layer 2 to be formed on the electrode by molding the carboxylic acid modified polyolefin resin D into a layer, And a lamination step of directly laminating the heat-resistant layer (3) and the electrode bonding layer (2) when either or both of them are in a molten state.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a process for producing a sealing film,

The present invention relates to a method for manufacturing a sealing film for sealing an electrode, which is a power generating element such as a secondary battery or a capacitor, housed in a bag, and a sealing film.

The present application claims priority based on Japanese Patent Application No. 2010-252940 filed on November 11, 2010, the contents of which are incorporated herein by reference.

2. Description of the Related Art In recent years, secondary batteries, capacitors, and the like, housed in a bag made of a film, have been employed as power sources for electronic devices such as notebook computers and cellular phones, hybrid cars, fuel cell vehicles and batteries for battery vehicles.

Conventionally, these secondary batteries and capacitors are constructed by sealing a flat power generating element in a flat bag or a drawn body formed of a laminated film in which a polyolefin sealant is laminated on a metal foil such as an aluminum foil. An electrode for charging and discharging is sealed by protruding one end to the outside on the bag film base. At the time of sealing, an electrode (electrode tab) on a tape is sandwiched by the film base material of the bag body and heat sealed.

Since the electrodes of these secondary batteries and the like (hereinafter sometimes referred to as " pack batteries ") are thicker than sealants of bag bodies, it is difficult to encapsulate the resin around the thickness direction of the electrodes during sealing, There may be a gap around the direction. If a gap is formed around the electrode, the sealing portion may deteriorate under long-term use, harsh environments such as high temperature or high humidity, or the bonding strength between the bag and the electrode in the sealing portion may be reduced, and the electrolyte may leak from the sealing portion.

To solve these problems, a method has been used in recent years in which a sealing film is sandwiched between the front and back surfaces of the electrode and the heat sealing is performed with the film substrate of the bag body. However, in order to improve the adhesiveness between the bag and the electrode, if the heating or pressurizing conditions during sealing are made strict, the resin between the metal foil and the electrode of the bag may become thin or the sealing film may be deformed and short-circuiting may occur.

When the sealing film is sandwiched between the film base material of the bag and the electrode and is heat sealed, for example, as disclosed in Patent Document 2, the sealing material is heat-sealed by exposing the water sealing film at the opening end of the bag. By such exposure, a short circuit can surely be prevented. However, since the seal bar is brought into contact with or approaching the exposed portion at the time of heat sealing, the seal film may melt or deform due to the contact of the high temperature seal bar or radiant heat. This makes it easier for the electrode to contact the metal foil of the film base of the bag.

In order to solve these problems, for example, Patent Document 1 discloses a method in which a heat-sealable portion of a terminal material is coated with a coating material having a laminated structure in which a heat-resistant layer made of a woven fabric, a nonwoven fabric, or an ultrahigh molecular weight polyethylene is sandwiched by a heat- , A configuration for preventing a short circuit is described.

Patent Document 2 discloses an adhesive film in which an electron beam crosslinked polyolefin layer and an acid denatured polyolefin layer are laminated.

Japanese Patent Application Laid-Open No. 62-61268 Japanese Patent Application Laid-Open No. 2001-297748

Since the coating material described in Patent Document 1 secures heat resistance by a woven fabric or a nonwoven fabric, it is necessary to select a woven fabric or a nonwoven fabric which is hardly melted. However, since woven fabrics and nonwoven fabrics are not melted, it is difficult to laminate them and the heat-sealable film with high adhesiveness. Therefore, there is a possibility that pinholes are likely to occur, and the sealing property may not be improved. In some cases, the sealing property is lowered. In addition, ultrahigh molecular weight polyethylene is difficult to obtain and is costly disadvantageous. Further, the ultrahigh molecular weight polyethylene can not be laminated with a thermally adhesive film made of a polypropylene type resin. Therefore, a polypropylene-based resin can not be employed for the sealant of the bag, and it is difficult to improve the heat resistance of the bag.

The adhesive film described in Patent Document 2 is excellent in heat resistance. However, this film is manufactured by extrusion laminating an acid-modified polyolefin layer by electron beam cross-linking the polyolefin film in advance, or by layering the polyolefin layer and the acid-modified polyolefin layer by coextrusion, followed by electron beam cross-linking. Therefore, an electron beam cross-linking step is required by any method. In paragraph [0013] of Patent Document 2, it is described that since a usual polypropylene is decomposed by irradiation with an electron beam, it is necessary to use a specific resin. In addition, when the polyolefin layer and the acid-modified polyolefin layer are laminated by co-extrusion and then crosslinked by electron beams, the acid-modified polyolefin is also crosslinked and the flexibility is lowered, so that it becomes difficult to cover the resin with no gap around the thickness direction of the electrode.

In view of the above background, it is an object of the present invention to provide a heat-resistant layer and an electrode adhesive layer which can be easily obtained by using a readily available material, A process for producing a sealing film excellent in heat resistance and sealing property capable of being laminated, and a sealing film produced by the manufacturing method are provided.

The inventors of the present invention have found that during the research of a sealing film excellent in heat resistance and sealing property, the carboxyl group of the acid-modified polyolefin resin in which the carboxylic acid is graft polymerized is easily reacted with the hydroxyl group, the amino group and the epoxy group and can be easily modified. The present invention is based on this finding.

That is, according to the first aspect of the present invention, there is provided a method for producing the following encapsulating film.

(1) A method for producing a sealing film sandwiched between an electrode serving as a power generation element housed in a bag and an end edge of the bag, comprising the steps of: (a) mixing an acid-modified polyolefin resin A obtained by graft-polymerizing a carboxylic acid with a functional group capable of reacting with a carboxyl group Melting and kneading both the resin B having the carboxyl group of the resin A and the functional group of the resin B to chemically bond the carboxyl group of the resin A and the functional group of the resin B to the resin C to form a heat resistant layer An adhesive layer forming step of forming an electrode bonding layer for forming a carboxylic acid-modified polyolefin resin D into a layer and bonding it to an electrode; and a step of forming an electrode bonding layer for bonding the resin heat- And a laminating step of directly laminating the electrode adhesive layer.

(2) The process for producing an encapsulating film according to (1), wherein the melt-kneading step is carried out in an extruder.

(3) The process for producing a sealing film according to (1) or (2), wherein the melt-kneading step and the heat-resistant layer film-forming step are carried out continuously.

(4) The process for producing a sealing film according to any one of (1) to (3), wherein the lamination step is carried out successively or successively to either or both of the heat resistant layer forming step and the adhesive layer forming step.

(5) The method for producing a sealing film according to any one of (1) to (4), wherein the lamination step is performed in a co-extrusion die.

(6) The process for producing a sealing film according to any one of (1) to (5), wherein the melt-kneading step is carried out in combination with a weight percentage of resin B of from 1 to 10 with respect to resin B of from 99 to 90 .

(7) The method for producing a sealing film according to any one of (1) to (6), wherein a resin having a melting point equal to or lower than the melting point of the resin A is used as the resin D.

Further, according to the second aspect of the present invention, the following encapsulating film is provided.

(8) An encapsulating film sandwiched between an electrode, which is a power generation element housed in a bag, and the end edge of the bag, comprising an acid-modified polyolefin resin A in which carboxylic acid is graft polymerized and a resin having a functional group capable of reacting with a carboxyl group of the resin A B were melted and kneaded to obtain a laminated structure in which the heat resistant layer made of the resin C modified by chemically bonding the carboxyl group of the resin A with the functional group of the resin B was directly laminated on the electrode bonding layer made of the carboxylic acid modified polyolefin resin D Encapsulating film.

(9) The encapsulating film according to (8), wherein the resin B is at least one selected from a resin having a hydroxyl group, an amino group or an epoxy group.

(10) The encapsulating film according to (8) or (9), wherein the resin A is an acid-modified polyolefin resin in which maleic anhydride is graft polymerized in polypropylene.

(11) The encapsulating film according to any one of (8) to (10), wherein the laminated structure is formed by co-extrusion of the resin C and the resin D.

(12) The encapsulating film according to any one of (8) to (11), wherein the heat-resistant layer is laminated with the innermost layer of the bag and a sealant to be thermally fused.

In the method for producing a sealing film of the present invention, since the carboxyl group of the resin A and the functional group of the resin B are chemically bonded to each other by resin C, a crosslinking step such as electron beam crosslinking becomes unnecessary. Therefore, heat resistance can be imparted to the heat resistant layer by a simple process.

Since both the resin A and the resin B are melted and kneaded, they can be modified with the resin C in a conventional extruder used in the film-forming step.

In the present invention, when either or both of the resin C and the resin D are in a molten state, the heat-resistant layer and the electrode adhesive layer are directly laminated. In the lamination method, one of the layers is formed by combining an extruder and a film-forming die, and then the other layer is extrusion-laminated. In another lamination method, the heat resistant layer and the electrode adhesive layer are co-extruded. According to these methods, in the present invention, the heat resistant layer and the electrode adhesive layer can be directly laminated with a high adhesive strength by a simple process. In the sealing film by these methods, the sealing film is hardly melted or deformed by the contact of the high-temperature seal bar or the radiant heat during the heat sealing. As a result, short-circuiting between the electrode and the metal foil of the bag is difficult to occur.

In particular, by co-extruding the heat resistant layer and the electrode adhesive layer, the heat resistant layer and the electrode adhesive layer can be directly laminated with a higher adhesive strength by a simpler process.

The sealing film of the present invention has the resin C in which the heat resistant layer is modified by chemically bonding the carboxyl group of the resin A and the functional group of the resin B and has a low melt fluidity. This makes it difficult for the heat-resistant layer to become thin at the time of heat sealing or to thermally deform the sealing film. Therefore, shorting of the metal foil of the electrode and the bag is difficult to occur.

When the resin B is at least one kind selected from resins having a hydroxyl group, an amino group or an epoxy group, the carboxyl group of the resin A and the functional group of the resin B are likely to be chemically bonded and the modification to the resin C is smooth. Since the resin A and the resin B are melted and kneaded, the carboxyl group of the resin A and the functional group of the resin B are easily chemically bonded uniformly.

If the resin A is an acid-modified polyolefin resin in which maleic anhydride is graft-polymerized to polypropylene, the functional groups of the resin B and the carboxyl group of the resin A are easily chemically bonded, and the modification to the resin C becomes more smooth.

When the laminated structure of the sealing film is formed by co-extrusion of the resin C and the resin D, the bonding strength of the laminated structure is high, the sealing film is not thermally deformed at the time of heat sealing, it's difficult.

If the innermost layer of the bag and the sealant to be thermally welded are laminated on the heat resistant layer, the heat welding strength of the innermost layer of the bag and the sealing film can be increased. Further, if the sealant is directly laminated on the heat resistant layer, peeling of the adhesive interface by the electrolytic solution can be prevented.

1 is a cross-sectional view showing an example of a sealing film of the present invention.
Fig. 2 is a cross-sectional view showing a state in which a laminate film of a bag is bonded to an electrode using the sealing film shown in Fig. 1;
3A is a perspective view showing an electrode in which a sealing film having the sealing film shown in Fig. 1 bonded to an electrode is formed.
FIG. 3B is a cross-sectional view showing an electrode in which a sealing film having the sealing film shown in FIG. 1 bonded to an electrode is formed.

Hereinafter, the present invention will be described in detail based on embodiments.

1 is a cross-sectional view showing a schematic structure of a sealing film 1 of the present invention.

2 is a sectional view along the longitudinal direction of the electrode 11 showing a state in which the sealing film 1 shown in Fig. 1 is sandwiched between the laminate film 20 of the bag and the electrode 11. Fig.

3A is a perspective view showing an electrode 10 having a sealing film formed by bonding the sealing film 1 shown in Fig. 1 to the electrode 11. Fig. Fig. 3B is a cross-sectional view showing the electrode 10 in which the sealing film is formed, in a direction perpendicular to the longitudinal direction of the electrode 11. Fig.

The encapsulating film (1) of the present invention is sandwiched between the electrode, which is a power generating element housed in the bag, and the end edge of the bag. As shown in Figs. 1 and 2, the basic layer structure of this film has a laminated structure composed of at least two layers in which the electrode adhesive layer 2 and the heat resistant layer 3 are laminated. In the sealing film 1 of this embodiment, the sealant 22, which is the innermost layer of the bag body, and the sealant 4 which is thermally welded are further directly laminated on the heat resistant layer 3 as a basic layer constitution.

The thickness of the sealing film (1) of the present invention is preferably 50 mu m to 300 mu m. If the thickness of the sealing film 1 is smaller than this range, the insulating property may be lowered. Further, the thickness of the sealing film 1 may be larger than this range. However, further improvement of the insulating property can not be expected, and it is rather difficult to seal the heat.

The heat resistant layer 3 is obtained by melting and kneading both the acid-modified polyolefin resin A in which the carboxylic acid is graft polymerized and the resin B having a functional group capable of reacting with the carboxyl group of the resin A, And a resin C modified by chemical bonding.

The resin blend ratio at this time is preferably 1 to 10% by weight of resin B with respect to 99 to 90% by weight of resin A. When the blend ratio of the resin B is lower than this range, the modifying effect of the resin C is small and the heat resistance of the sealing film 1 may become insufficient. If the blend ratio of the resin B is higher than this range, the heat resistant layer 3 tends to become fragile. For this reason, cracks may occur in the heat-resistant layer 3 due to the bending of the electrode 11 when the packed battery is mounted.

The heat-resistant layer 3 secures insulation between the metal foil 21 of the laminate film 20 of the bag and the electrode 11. The heat-resistant layer 3 is preferably thin as long as it can prevent thermal deformation of the sealing film 1 at the time of thermal application of heat and ensure insulation. The thickness of the heat-resistant layer 3 is preferably 30 m to 150 m. If the thickness of the heat resistant layer 3 is less than 30 占 퐉, the sealing film 1 may be thermally deformed or thinned at the time of heat application, resulting in insufficient insulation. The thickness of the heat resistant layer 3 may exceed 150 mu m. However, further improvements in insulation can not be expected. The resin constituting the heat resistant layer (3) is made more polymerized than the resin (A) because the resin (B) is chemically bonded to the resin (A), and is relatively hard and has low melt fluidity. Therefore, when the heat resistant layer 3 is thicker than necessary, the gap formed by the step due to the thickness of the electrode 11 when the electrode 11 is sandwiched between the two sealing films 1, It is difficult to fill. As a result, pinholes may be generated between the sealing films 1 and 1.

The acid-modified polyolefin resin A is obtained by graft polymerization of an unsaturated carboxylic acid or a derivative thereof with a polyolefin obtained by polymerizing one or more alkylene monomers such as ethylene and propylene as a base resin.

As the polyolefin, for example, homopolymers and copolymers of polypropylene and polyethylene are used. Examples of the copolymer include a random copolymer (random PP) or a block copolymer (block PP) of propylene and 1 to 5 wt% of ethylene, a random or block copolymer of ethylene and 1 to 10 wt% of propylene, And 1 to 10% by weight of an? -Olefin having 4 or more carbon atoms, and mixtures thereof.

When the polyethylene resin is used as the base resin of the resin A in the heat resistant layer 3 of the sealing film 1 in order to make the sealant 22 of the bag laminate film 20 a polyethylene resin, It is preferable to use linear low-density polyethylene or high-density polyethylene having a temperature of about 140 占 폚.

The base resin of the acid-modified polyolefin resin A is preferably a homopolypropylene and a propylene-ethylene random copolymer having a melt flow rate (MFR) of 0.5 to 30 g / 10 min, particularly 5 to 15 g / 10 min, Lt; RTI ID = 0.0 > olefin < / RTI > copolymer are preferably used.

The MFR of the resin C forming the heat resistant layer 3 is preferably in the range of 0.5 g / 10 min to 3 g / 10 min. When the MFR is smaller than this range, molding may be difficult. If the MFR is larger than this range, the heat-resistant layer 3 may be deformed or thinned at the time of heat application, resulting in deterioration of the insulating property.

The heat resistant layer 3 is required to be hard to be melted or softened when the sealing film 1 of the present invention is thermally fused to the electrode 11. Therefore, the higher the melting point of the resin C forming this, the better. Concretely, in the case of a sealing film made of a polypropylene type resin, a resin having a melting point of 130 to 170 캜 as measured by the JIS K6921-2 DSC method is preferable.

In order to obtain such a resin C, it is preferable to use a homopolymer of polypropylene (PP) as a resin A, a random copolymer or block copolymer of ethylene and propylene, or an acid-modified polyolefin resin which is a base resin thereof . The PP-based resin generally tends to become vulnerable under a low-temperature environment. A block copolymer of ethylene and propylene is preferable because it is excellent in flexibility even when the melting point is high and is not weakened even in a low temperature environment (cold resistance).

Examples of the unsaturated carboxylic acid graft-polymerized to the base resin of the acid-modified polyolefin resin A include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, their acid anhydrides, , Amides, imides, and metal salts. Among these unsaturated carboxylic acids, maleic acid is preferable, and maleic anhydride is most preferable. In order to accelerate the reaction between the polyolefin and the unsaturated carboxylic acid, it is preferable to use a radical polymerization initiator such as an organic peroxide such as benzoyl peroxide or lauroyl peroxide or azobisisobutyronitrile.

The amount of the unsaturated carboxylic acid to be graft-polymerized is usually 0.5 to 5% by weight based on the total weight of the monomers.

The graft polymerization of an unsaturated carboxylic acid to a polyolefin includes, for example, a method of reacting a polyolefin and an unsaturated carboxylic acid in a molten state, a method of reacting in a solution state, a method of reacting in a slurry state, Method. Among these methods, a method of reacting in a molten state is preferable in terms of easiness of operation. Specifically, a polymerization initiator such as the above-mentioned polyolefin, unsaturated carboxylic acid, or organic peroxide is sufficiently mixed with a tumbler, a Henschel mixer or the like. Thereafter, the mixture is melted and kneaded to carry out the grafting reaction.

The melt-kneading method is not particularly limited and can be carried out using, for example, a screw extruder, Banbury mixer, or a mixing roll. Among these methods, a screw extruder is preferably used because it is easy to operate. The screw extruder may be a single shaft, a biaxial screw, or a multi-screw screw. The temperature of the melt kneading is preferably not lower than the melting point of the polyolefin used and not higher than the decomposition temperature of the organic peroxide to be used. The specific temperature and time are usually from 160 to 280 DEG C for 0.3 to 30 minutes, preferably from 170 to 250 DEG C for from 1 to 10 minutes.

A heat-resistant layer 3 is formed by molding a resin C modified by melt-kneading a resin B in an acid-denatured polyolefin resin A into a layer to give heat resistance to the sealing film. The heat resistant layer 3 may be formed by a calendering method in which the resin C is rolled between a plurality of rolls and an extrusion method in which the melted resin C is extruded by a T-die ring die. Among these methods, the extrusion method is preferable because the resin C melt-kneaded by the extruder used in the denaturation step can be extruded as it is.

It is preferable to add a step of introducing a polyolefin and an unsaturated carboxylic acid into an extruder, melting and kneading the same, and modifying the polyolefin and the unsaturated carboxylic acid with an acid-denatured polyolefin resin A, before the step of denaturation into the resin C. Thereafter, it is preferable to further add the resin B to the extruder to denature the resin A with the resin C.

Further, an acid-modified polyolefin resin graft-polymerized with an unsaturated carboxylic acid is commercially available, and a commercially available product can also be used.

The PP-based polymer graft-polymerized with an unsaturated carboxylic acid includes an ionomer in which a carboxyl group is neutralized with a metal hydroxide, an alkoxide, a lower fatty acid salt or the like.

Examples of the functional group capable of reacting with the carboxyl group of the resin A of the resin B include a hydroxyl group, an amino group, a carboxyl group, a formyl group and an epoxy group. The resin B having these functional groups is not particularly limited, but a general-purpose resin which is easily available is preferable. Examples of such a general purpose resin include ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVA), polyamide (PA) such as nylon 6 or nylon 6,6, ethylene-glycidyl methacrylate copolymer ) And epoxy group-containing resins. Therefore, preferred functional groups capable of reacting with the carboxyl group of the resin A include a hydroxyl group, an amino group and an epoxy group.

When EVOH is used as the resin B, it is preferable that the MFR is 1 to 30 g / 10 min (230 DEG C) from the viewpoint of compatibility with the resin A and processability. More preferably 1 to 20 g / 10 min, and particularly preferably 3 to 16 g / 10 min. The ethylene content in the EVOH is preferably 20 to 60 mol%, more preferably 25 to 50 mol%, of ethylene.

When a polyamide is used as the resin B, a polyamide having a terminal amino group amount and a terminal carboxyl group content equal to that of a polyamide having a terminal amino group blocked and a terminal carboxyl group relative to the terminal amino group is 2 and not more than the amount of terminal amino group 8.0 × 10 ^- it is preferred to use a ⁵ mol / g or more polyamides. Such a polyamide can increase the shear rate dependency of the melt viscosity of the resin C. Since the polyamide has a relatively high melting point in the general-purpose resin, resistance to thermal deformation of the resulting resin C is improved.

When an epoxy group-containing resin is used as the resin B, it is preferable that the ethylene monomer is copolymerized from the viewpoint of compatibility with the resin A and processability. The carboxyl group of the resin A is converted into the epoxy group of the epoxy group-containing resin, and the hydroxyl group produced by ring opening is esterified. This esterification is carried out repeatedly. As a result, the molecular structure of the resin C becomes like a crosslinked structure, and resistance to thermal deformation is improved.

The electrode bonding layer 2 is a layer in which the sealing film 1 is heated and pressed onto the electrode 11 to be thermally fused. The electrode bonding layer 2 is made of a carboxylic acid-modified polyolefin resin D having excellent adhesion to a metal.

Resin D is a resin obtained by copolymerizing one or two or more kinds of alkylene monomers such as ethylene and propylene with one or more kinds of unsaturated carboxylic acid or its derivative. The copolymer may be a block copolymer, a graft copolymer or a random copolymer. When a graft copolymer is used, the same polyolefin as the resin A and the same unsaturated carboxylic acid as the resin A may be subjected to graft polymerization to give a carboxylic acid-modified polyolefin resin D.

It is preferable that the electrode bonding layer 2 is thin as long as the heat welding with the electrode 11 is ensured. Normally, the thickness of the electrode adhesive layer 2 is 20 탆 to 60 탆. If the thickness of the electrode bonding layer 2 is smaller than this range, the bonding strength between the electrode bonding layer 2 and the electrode 11 may be lowered. If the thickness of the electrode adhesive layer 2 is larger than this range, the heat resistance of the sealing film 1 may be insufficient.

The melting point of the resin D forming the electrode bonding layer 2 is preferably lower than the melting point of the resin C forming the heat resistant layer 3. [ In the case of the sealing film 1 made of a polypropylene-based resin, the melting point of the resin D is preferably 130 ° C to 150 ° C. If the melting point of the resin D is lower than this range, the heat resistance of the sealing film 1 may be insufficient. If the melting point of the resin D is higher than this range, it is difficult to increase the melting point of the resin D with the resin C forming the heat resistant layer 3. If the melting point difference between the resin D and the resin C is 10 占 폚 or more, it is preferable to control the temperature at the time of heat application by heat.

The melting point of the resin D is preferably equal to or lower than the melting point of the resin A. When the resin A is modified with the resin C, the molecules of the resin B are bonded to the molecules of the resin A to increase the molecular weight of the resin C, and the melting point of the resin C becomes higher than that of the resin A. As a result, it becomes easy to set the melting point of the resin D and the resin C to 10 ° C or higher. When resin D and resin A are made of the same resin, the resin can be easily managed.

As a method of forming the electrode adhesive layer 2, there can be mentioned an extrusion method in which a resin D melted by using an extruder is extruded from a T-die ring die. When a graft copolymer is used as the resin D, the polyolefin and the unsaturated carboxylic acid can be graft polymerized when extruded by an extruder in the same manner as the resin A.

When acid-modified polyethylene is used as the electrode bonding layer 2 in order to obtain a sealing film made of a polyethylene-based resin, maleic anhydride-graft copolymerized polyethylene having a melting point of about 90 to 120 캜 is preferable. The acid-modified polyethylene includes an ionomer in which a carboxyl group is neutralized.

The MFR of the acid-modified polyolefin resin D forming the electrode bonding layer 2 is preferably in the range of 3 g / 10 min to 30 g / 10 min. It is more preferable that the MFR is in the range of 5 g / 10 min to 10 g / 10 min. If the MFR is smaller than these ranges, the acid-modified polyolefin may not be sufficiently surrounded around the electrode 11 at the time of heat application. If the MFR is larger than these ranges, the electrode bonding layer 2 becomes thinner and the bonding strength may be insufficient.

In the present invention, the MFR is measured at 230 占 폚 in the case of a polypropylene-based resin and 190 占 폚 in the case of a polyethylene-based resin in JIS K7210.

Since the carboxylic acid-modified polyolefin resin is commercially available, it is also possible to use a commercially available product.

The electrode adhesive layer 2 and the heat resistant layer 3 are directly laminated without interposing an adhesive layer or an anchoring layer between the layers. As a result, it is possible to prevent peeling due to the penetration of the electrolytic solution into the laminated interface and deterioration of the flexibility of the sealing film 1. In the sealing film 1, it is also important that the heat-resistant layer 3 as well as the electrode adhesive layer 2 is surrounded by the electrode 11. If there is no effect of flexibility or interaction with the electrolyte, dry lamination may be performed using an adhesive. In the case of extrusion laminating, an anchor agent may be used.

As a method for directly laminating, a heat laminate in which a molded electrode bonding layer 2 and a heat resistant layer 3 are overlaid and heat-welded, one of an electrode adhesive layer 2 and a heat resistant layer 3 is molded in advance, And a co-extrusion laminate method in which both the electrode adhesive layer 2 and the heat-resistant layer 3 are laminated while being extruded from a co-extrusion die when they are both in a molten state. Of these methods, the co-extrusion lamination method can be directly laminated in a co-extrusion die by connecting an extruder for extruding the resin C while melt-kneading the resin C and a different extruder for extruding the resin D to the co-extrusion die . This makes it possible to modify the resin C, to form the heat resistant layer 3, to form the electrode bonding layer 2, and to laminate the electrode bonding layer 2 and the heat resistant layer 3 in one step.

In the present embodiment, the sealant 4 is laminated on the surface of the heat resistant layer 3 opposite to the electrode adhesive layer 2. The sealant 4 is a layer which is heat-pressed and welded to the sealant 22 of the laminate film 20 of the bag body.

The same method as that of the lamination of the electrode adhesive layer 2 and the heat resistant layer 3 is adopted for the same reason as the lamination method. Among these methods, since the electrode adhesive layer 2, the heat resistant layer 3 and the sealant 4 can be laminated at one time, it is preferable to laminate them by a coextrusion laminate method.

It is preferable that the sealant 4 is thin as long as the sealant 22 is secured to the bag body. Normally, the thickness of the sealant 4 is 20 to 40 占 퐉. If the thickness of the sealant 4 is smaller than these ranges, the weld strength between the sealant 4 and the sealant 22 of the bag may be lowered. If the thickness of the sealant 4 is larger than these ranges, the heat resistance of the sealing film 1 may be insufficient.

The resin forming the sealant 4 (hereinafter referred to as " resin E ") is easily welded to the sealant 22 of the laminate film 20 of the bag body, Resins are preferred. Normally, the sealing film 1 is made of a PP-based resin in that it is excellent in heat resistance.

When the sealing film (1) is composed of a PP-based resin, the resin E may be a homopolymer of PP, a random copolymer or block copolymer of ethylene and propylene, or a mixture thereof, or a polymer alloy thereof. Of these, random copolymers of ethylene and propylene are preferable in that they are excellent in flexibility.

In the case of the sealing film made of the PP-based resin, the melting point of the resin E forming the sealant 4 is preferably 130 ° C to 170 ° C. If the melting point of the resin E is lower than this range, the heat resistance of the sealing film 1 may be insufficient. If the melting point of the resin E forming the sealant 4 is higher than this range, it is difficult to increase the melting point of the resin E forming the heat resistant layer 3 with the resin C. When the difference between the melting point of the resin E and the melting point of the resin C is 10 占 폚 or more, it is preferable to control the temperature at the time of melt-bonding to the laminate film 20 of the bag.

When the sealant (4) is made of a polyethylene-based resin in order to make the sealing film (1) to be a polyethylene-based resin, it is preferable to use a low-density polyethylene or a linear low-density polyethylene having a melting point of about 100 to 120 deg.

In the case of a sealing film made of a PP-based resin, the resin E forming the sealant 4 preferably has an MFR of 3 g / 10 min to 30 g / 10 min, more preferably 5 g / 10 min to 10 g / 10 min More preferable. If the MFR of the resin E is smaller than these ranges, it may be difficult to laminate the laminate with an extruded laminate or a coextruded laminate. If the MFR of the resin E is larger than these ranges, it may be difficult to form the resin into a co-extrusion ring die.

The sealant 4 is an optional layer and may not be formed when the heat-resistant layer 3 and the sealant 22 of the bag are secured.

The sealing film (1) of the present invention is fused between the sealant (22) of the bag and the electrode (11). When the sealing film 1 is welded, the sealing film 1 is welded to a predetermined width from the end of the laminated film 20 as shown in Fig. At this time, in order to facilitate positioning of the sealing film 1, it is preferable to color at least one of the two sealing films 1. As a coloring method, a method such as printing, dyeing, incorporation of a coloring agent such as a dye or pigment into at least one layer of the layer constituting the sealing film 1 can be used. Among these methods, incorporation of a coloring agent is preferable because it is simple. The layer to be colored can also be used to confirm the adhesion of the bag to the sealant 22. Therefore, it is preferable that the coloring layer is a heat-resistant layer 3 which is not deformed or melted when melted.

The encapsulation film 1 of the present embodiment is characterized in that in order to position the encapsulation film 1 at the time of melting and to place the resin around the thickness direction of the electrode without gap, Is preferably thermally fused to at least one surface, preferably both surfaces, of the electrode 11 by using the electrode adhesive layer 2 of the sealing film 1. This makes it possible to easily and reliably deposit the sealant (22) of the bag using the sealant (4) or the heat resistant layer (3) of the sealant film (1). At this time, when the sealing film 1 is colored, the electrode tab and the sealing film 1 are bonded to each other using an optical sensor in an automated welding assembly line at the time of heat application of the innermost layer of the bag body and the electrode tab to which the sealing film is deposited Can be accurately positioned.

The heat sealing of the sealing film 1 and the electrode 11 can be performed by directly heating the sealant using a heat sealer, an impulse sealer, or the like. When the sealing film 1 is heated, direct heating of the electrode 11 by using electromagnetic induction heating or energizing heating suppresses the flow caused by melting of the outer portion of the sealant 4 or the heat resistant layer 3 , So that softening and melting of the inner portion of the heat resistant layer 3 and the electrode bonding layer 2 are promoted.

Examples of the shape of the electrode 11 include a tape and a round rod. Although the size of the electrode 11 is not particularly limited, for example, the thickness of the back side of the tape is about 50 to 500 mu m, the width is about 5 to 100 mm, and the length is about 40 to 100 mm. The ridgeline (edge portion) of the tape electrode 11 may be rounded. The surface may be the same as the rolled surface, but is preferably roughened by surface treatment such as sandblasting or etching. By roughening, the bonding strength of the sealing film 1 is improved. In addition, an undercoating treatment such as chemical conversion treatment may be performed.

As the material of the electrode 11, for example, metals such as aluminum, copper, nickel, iron, gold, platinum and various alloys can be used. Of these, aluminum or copper is preferably used because it is excellent in conductivity and advantageous in terms of cost. However, aluminum or copper may not be sufficient in resistance to hydrogen fluoride (hydrofluoric acid), which is liable to occur in an electrolytic solution in a packed battery. Further, when the PP-based resin is in contact with copper, the degradation of the resin may be promoted. Therefore, it is preferable to apply nickel, which is highly conductive and excellent in resistance to hydrofluoric acid, to the base metal of aluminum or copper.

2, the laminate film 20 of the bag in which the encapsulating film 1 of the present invention is deposited is formed by laminating a sealant 22 on one surface of the metal foil 21 and a film substrate 22 on the other surface, (23) are stacked on one another. The laminate film 20 may be laminated with other layers.

The laminate film 20 of the bag is formed into a draw-formed bag, a flat bag or the like. Examples of the metal foil 21 include aluminum foil, stainless steel foil, copper foil and iron foil. The metal foil 21 may be subjected to an undercoating treatment such as chemical conversion treatment.

As the resin forming the sealant 22 of the laminate film 20 of the bag body, the sealant 4 of the sealing film 1 and the resin which can be fused are selected. As such a resin, for example, when the sealant (4) of the sealing film (1) is a PP-based resin, a homopolymer of PP or a copolymer of PP and ethylene can be used. In the case of a polyethylene-based resin, a low-density polyethylene or a linear low-density polyethylene can be used. The resin constituting the film base material 23 is not particularly limited, but polyamide, polyethylene terephthalate (PET), PP or the like having high strength is preferably used. These resins have high physical strength when stretched. A plurality of these films may be laminated.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications are possible.

For example, the sealing film 1 may include another layer such as an additional resin layer in order to improve adhesiveness between the resin layers, physical strength, and insulation. In this case, it is preferable that the other layer is a layer which is difficult to be melted at the time of heat application and has high flexibility. Further, the sealing film 1 may be provided with a safety valve function in a case where the laminate strength between the respective layers is controlled to an appropriate range and the temperature or pressure in the bag body abnormally rises.

Example

Examples and Comparative Examples of the encapsulating film (1) shown in Table 1 were prepared using the resins shown below.

Resin A: maleic anhydride-modified PP (MFR 2.4 g / 10 min (230 캜), melting point 143 캜) graft-polymerized with maleic anhydride to random PP

Resin B

Resin B-1: EVOH having an ethylene content of 48 mol% (MFR 15 g / 10 min (230 캜), melting point 160 캜)

Resin B-2: EVOH having an ethylene content of 32 mol% (MFR: 3.6 g / 10 min (230 DEG C), melting point: 183 DEG C)

Resin B-3: Nylon 6 (relative viscosity: 3.37, melting point: 220 占 폚)

Resin B-4: Nylon 6 (relative viscosity 4.08, melting point 220 캜)

Resin B-5: E-GMA copolymer (MFR 3 g / 10 min (190 캜), melting point 105 캜) having a glycidyl methacrylate content of 6 wt%

Resin D

Resin D-1: maleic anhydride-modified PP (MFR 7.5 g / 10 min (230 캜), melting point 135 캜) graft-polymerized with maleic anhydride to random PP

Resin D-2: maleic anhydride-modified PP (MFR 7.0 g / 10 min (230 캜), melting point 140 캜) graft-polymerized with maleic anhydride to random PP

Resin E: Block PP (MFR 2.3 g (230 캜) / 10 min, melting point 163 캜)

≪ Examples 1 to 15 &

The resin A and the resin B were extruded in a hopper of an extruder at a mixing ratio shown in Table 1 while being denatured with a resin C at the extrusion temperature shown in Table 1 and laminated in a coextrusion T die together with the resin D extruded by another extruder, Examples 1 to 15 of Example 1 were cast molded.

In the embodiment in which the layer of the layer construction shown in Table 1 has three layers, during the co-extrusion cast molding, the resin E is further extruded from another extruder and co-extruded and laminated. In the examples in which three columns of the coloring agent of Table 1 were used, 3 parts by weight of a pigment-based master batch of a PP base was added when the resin A and the resin B were blended.

The extrusion temperatures of the resin D and the resin E were all 240 캜.

Thus, a laminated film having a two-layer structure composed of the electrode adhesive layer 2 having a thickness of 40 μm and the heat-resistant layer 3 having a thickness of the heat-resistant layer shown in Table 1, and a laminated film having a thickness of 20 μm Thereby forming a laminated film having a layer structure. The laminated film was slit to a width of 25 mm to prepare Examples 1 to 15 of the sealing film (1).

≪ Comparative Example 1 &

The resin D-1 and the resin E were respectively extruded at 240 占 폚 and laminated in a co-extruded T-die to obtain a laminated film having a two-layer structure composed of the electrode adhesive layer 2 of 20 占 퐉 and the sealant 4 of 80 占 퐉, Respectively. This laminated film was slit with a width of 25 mm to produce the encapsulating film (1) of Comparative Example 1.

In Table 1, " part " means all parts by weight.

≪ Measurement of electrode bonding strength >

A square aluminum foil having a thickness of 50 mu m, a width of 50 mm, and a length of 50 mm was used as the electrode 11. Examples 1 to 15 and Comparative Example 1 of the sealing film 1 were each cut into a length of 60 mm. And the electrode adhesive layer 2 of the sealing film 1 was placed inside the electrode 11. Using a heat sealer, the aluminum foil was heated on the side of the aluminum foil under the conditions of 200 DEG C and 0.2 MPa for 3 seconds, leaving the untreated portion at one end and thermally welding the other end.

The peel strength between the electrode bonding layer 2 and the electrode 11 of each sealing film 1 was measured using an Instron type tensile tester. At the time of measuring the peel strength, the ends of the sealing film 1 not bonded to the electrodes 11 and the ends of the electrodes 11 were fixed to two chucks of a tensile tester, and were stretched at a speed of 300 mm / The 180 degree peel strength was measured. The electrode bonding layer 2 and the electrode 11 of each encapsulation film 1 were heat sealed at a sealing strength of 27.5 to 32.8 N / 25 mm.

<Measurement of Lamination Film Welding Strength>

A biaxially oriented PET film having a thickness of 12 占 퐉 as the film base material 23, an aluminum foil having a thickness of 40 占 퐉 as the metal foil 21 and a random copolymer film of ethylene and propylene having a thickness of 40 占 퐉 as the sealant 22 were laminated by dry lamination . The obtained laminated film was cut into a square having a side length of 100 mm to produce two laminate films 20 of a bag body.

Examples 1 to 15 and Comparative Example 1 of the sealing film 1 were each cut into a length of 60 mm. The sealant 22 of the two bag laminate films 20 was opposed to each other and the sealing film 1 was sandwiched therebetween. When the sealing film 1 was sandwiched, the sealing film 1 was exposed 5 mm from the end of the laminated film 20.

Both ends of the two laminate films 20 of the bag were heated under the same conditions as the measurement of the electrode bonding strength to weld one end of the side on which the sealing film 1 was exposed. The other end was left as a beauty attachment. At the time of melting the sealing film (1), the seal bar was brought into contact with about 2 mm of the base of the exposed portion of the sealing film (1).

The end portion of the non-cured portion of the sealing film 1 and the end portion of the laminated film 20 were fixed to two chucks of a tensile tester and the same conditions as those for measuring the electrode bonding strength were measured, The heat seal strength of the sealant 4 or the heat resistant layer 3 of the laminated film 1 and the laminate film 20 was measured. Each of the sealing film 1 and the laminated film 20 was heat-sealed at a sealing strength of 124.2 to 143.3 N / 25 mm.

In addition, no trace of thermal deformation or melting was found in the portions of the sealing film 1 exposed in the laminated film 20 in all the examples. On the other hand, in the comparative example, the base of the portion exposed in the laminate film 20 was somewhat contracted.

&Lt; MFR of kneaded product &

A melt-kneaded product (resin C-1) of 95 parts by weight of Resin A and 5 parts by weight of Resin B-1, 95 parts by weight of Resin A and 5 parts by weight of Resin B- Extruded alone, and the MFR at 230 占 폚 was measured. The original resin A had an MFR of 2.4. Resin C-1 had an MFR of 1.9, which was lower than that of Resin A. The MFR of Resin C-3 was 2.5, which was higher than that of Resin A. The reason why the heat resistance of the sealing film 1 is improved in the present invention is not only that the molecular weight is increased due to the chemical bonding between the carboxyl group of the resin A and the functional group of the resin B, .

INDUSTRIAL APPLICABILITY The present invention can be widely applied to an encapsulating film for encapsulating an electrode, which is a power generating element such as a secondary battery and a capacitor, housed in a bag, and a sealing film.

One… Encapsulation film
2… The electrode-
3 ... Heat resistant layer
4… Sealant
10 ... The electrode on which the sealing film is formed
11 ... electrode
20 ... The laminate film of the bag
21 ... Metal foil of laminate film
22 ... Sealant of laminate film
23 ... Film substrate of laminate film

Claims (12)

A manufacturing method of a sealing film sandwiched between an electrode, which is a power generating element housed in a bag, and an end edge of the bag,
The acid-modified polyolefin resin A in which the carboxylic acid is graft polymerized and the resin B having the functional group capable of reacting with the carboxyl group of the resin A are melted and kneaded to chemically bond the functional group of the resin B with the carboxyl group of the resin A, A melt-kneading step of modifying the melt-
A heat resistant layer forming step of forming a heat resistant layer by forming the resin C into a layer,
An adhesive layer-forming step of forming a carboxylic acid-modified polyolefin resin D into a layer to form an electrode bonding layer to be bonded to an electrode,
And a lamination step of directly laminating the heat resistant layer and the electrode adhesive layer when either or both of the resin C and the resin D are in a molten state. The method according to claim 1,
Wherein the melt-kneading step is carried out in an extruder. 3. The method according to claim 1 or 2,
Wherein the melt-kneading step and the heat-resistant layer film-forming step are performed continuously. 3. The method according to claim 1 or 2,
Wherein the laminating step is carried out successively or successively to either or both of the heat resistant layer forming step and the adhesive layer forming step. 3. The method according to claim 1 or 2,
Wherein the laminating step is performed in a co-extrusion die. 3. The method according to claim 1 or 2,
Wherein the melt-kneading step is carried out by mixing the resin A in a weight percentage of 1 to 10 with respect to the resin A in a ratio of 99 to 90. 3. The method according to claim 1 or 2,
A resin having a melting point equal to or lower than the melting point of the resin (A) is used as the resin (D). An encapsulating film sandwiched between an electrode of a power generating element housed in a bag and an end edge of the bag,
Modified polyolefin resin A in which a carboxylic acid is graft-polymerized and a resin B having a functional group capable of reacting with a carboxyl group are melted and kneaded to obtain a resin modified by chemically bonding a carboxyl group of the resin A and a functional group of the resin B C has a laminated structure in which an electrode bonding layer made of a carboxylic acid-modified polyolefin resin D is directly laminated when either or both of the resin C and the resin D are in a molten state. 9. The method of claim 8,
Wherein the resin B is at least one selected from a resin having a hydroxyl group, an amino group or an epoxy group. 10. The method according to claim 8 or 9,
Wherein the resin A is an acid-modified polyolefin resin obtained by graft polymerization of maleic anhydride onto polypropylene. 10. The method according to claim 8 or 9,
Wherein the laminated structure is formed by co-extrusion of the resin C and the resin D. 10. The method according to claim 8 or 9,
And a sealant to be thermally welded to the innermost layer of the bag is laminated on the heat resistant layer.

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