JP6159516B2 - Terminal adhesive tape and method of manufacturing the tape - Google Patents

Description

  The present invention relates to a terminal bonding tape interposed between a laminated film and a terminal in a battery (including a capacitor) encased by the laminated film, and a method for manufacturing the same.

  As electronic devices become smaller and lighter in demand, batteries used as power sources are also required to be smaller and lighter. At the same time, the battery is required to have a high energy density and a large energy capacity. In order to satisfy these requirements, in recent years, development of a nonaqueous electrolyte battery (for example, a thin lithium ion battery) in which a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte are enclosed in a laminate film is remarkable.

  FIG. 2 is a schematic longitudinal sectional view (A) showing an example of the nonaqueous electrolyte battery and an enlarged view (B) of the a-a ′ section. The nonaqueous electrolyte battery 20 is manufactured by storing power generation elements such as a positive electrode 25, a negative electrode 26, a separator 27, and a nonaqueous electrolyte (not shown) in a laminate film 22 and heat-sealing the peripheral portion of the laminate film 22. The At this time, a positive electrode terminal 23 connected to the positive electrode 25 and a negative electrode terminal (hereinafter abbreviated as a terminal) 24 connected to the negative electrode 26 are respectively connected to a terminal adhesive tape (hereinafter referred to as a “terminal adhesive tape”) at the heat seal portion at the periphery of the laminate film. It is bonded to the laminate film 22 via the adhesive tape 21 and is led out from the inside of the battery in a sealed state.

The main purpose of using the adhesive tape 21 between the laminate film 22 and the terminals 23 and 24 is to adhere the laminate film 22 and the terminals 23 and 24, but it also has the purpose of preventing a short circuit.
The general laminate film 22 has a layer structure of surface layer / barrier layer / heat seal layer. Since the barrier layer is made of a metal foil such as an aluminum foil, when the peripheral portion of the laminate film 22 is heat sealed, The seal layer may melt and the barrier layer and the terminals 23 and 24 may be close to each other, causing a short circuit. Therefore, the adhesive tape 21 is interposed between the laminate film 22 and the terminals 23 and 24 to maintain the distance between the barrier layer of the laminate film 22 and the terminals 23 and 24, thereby preventing a short circuit due to proximity.

Patent Document 1 proposes an adhesive tape including a crosslinked layer made of a crosslinked polyolefin resin. Since the crosslinked layer is hardly melted by heat at the time of heat sealing, if a crosslinked layer is provided on the adhesive tape, a short circuit due to the proximity of the barrier layer and the terminal can be prevented more reliably.
Moreover, in patent document 1, as resin which forms this bridge | crosslinking layer, what added the crosslinking adjuvant (trimethylol propane trimethacrylate) to low density polyethylene (Example 1 thru | or 5) and random type polypropylene (Example 6), An example is shown in which maleic anhydride-modified polypropylene is added with a crosslinking aid (trimethylolpropane trimethacrylate) (Example 7). The terminal bonding tapes using low density polyethylene (Examples 1 to 5) are suitable for bonding a laminate film (hereinafter abbreviated as PE-based outer packaging material) whose heat seal layer is made of an ethylene resin and terminals. The terminal bonding tape using propylene resin (Examples 6 and 7) is used to bond a laminate film (hereinafter abbreviated as PP-based outer packaging material) whose heat seal layer is made of propylene resin and a terminal. It is preferably used for this.

  By the way, it is known that ethylene-based resins are easily cross-linked by electron beam irradiation, but propylene-based resins are difficult to cross-link by electron beam irradiation. When a propylene-based resin is irradiated with an electron beam, a decomposition reaction in which molecular chains are broken is more likely to occur than a crosslinking reaction in which molecules are bonded to each other. Therefore, in Example 6 and Example 7 described above, a crosslinking assistant is used in combination to promote the crosslinking reaction. However, a resin composition containing a crosslinking aid may be crosslinked by heat during film formation. When crosslinking proceeds during film formation, gelled materials are mixed in the molten resin, making it difficult to stably form a film.

In Patent Document 2, as a resin composition for forming a cross-linked layer of an adhesive tape, polypropylene, an ethylene polymer, a butene polymer, a three-component copolymer of ethylene, butene, and propylene, and a density of 900 kg / m. No. ³ low crystalline ethylene / butene copolymer, amorphous ethylene / propylene copolymer, propylene α / olefin copolymer, etc. ing. By blending the above-mentioned subcomponents in place of the crosslinking aid, crosslinking by electron beam irradiation of polypropylene is possible, and thermal crosslinking during film formation is suppressed.

JP2001-102016 JP 2002-289157 A

Prior to the present invention, a film was formed from a resin composition in which polyethylene was added as an accessory component to polypropylene, and an adhesive tape was produced by irradiating the film with an electron beam, and the short-circuit prevention performance of the tape was examined. Specifically, the probe was pressed against the adhesive tape, the surface temperature of the adhesive tape was raised to 250 ° C., and how much the adhesive tape was deformed was measured. If the amount of deformation is large, the effect of suppressing the proximity between the barrier layer and the terminal is poor, and a short-circuit prevention effect cannot be expected. On the other hand, when the deformation amount is small, the effect of suppressing the proximity between the barrier layer and the terminal is rich, and an effect of preventing a short circuit can be expected.
As a result of the measurement, the amount of deformation of the adhesive tape made of a composition in which polyethylene was blended with polypropylene was relatively large. This seems to be because the compatibility between the polypropylene and the ethylene component is not good. Since the ethylene component is not uniformly dispersed in polypropylene, it is presumed that there was a portion where a crosslinked structure was not built in the adhesive tape.

  The present invention aims to build a cross-linking structure that exhibits a short-circuit prevention effect on an adhesive tape containing a propylene-based resin as a main component using an active energy ray, and has good adhesion to a PP-based outer packaging material, It is another object of the present invention to provide an adhesive tape that can reliably prevent a short circuit caused by the proximity of the barrier layer of the outer packaging material and the terminal.

According to the present invention, as means for solving the above problems,
(1) A terminal-adhesive tape for adhering the laminate film and terminals in a battery encased by a laminate film, comprising a resin composition in which a propylene-based thermoplastic elastomer is blended with a propylene-based resin, and a crosslinked structure and have a, the propylene-based thermoplastic elastomer, a hard segment of polypropylene, consists of a soft segment, it said soft segment to said hard segment is characterized by a nano-dispersed elastomer dispersed in nano order Terminal adhesive tape is provided,
(2) After the propylene-based thermoplastic elastomer to the propylene resin is by molding a resin composition formulated into a film, the production method of the adhesive tape is provided, which comprises an active energy ray The

  In the present invention, the auxiliary component added to the propylene-based resin for the purpose of promoting cross-linking is a polypropylene-based thermoplastic elastomer (hereinafter abbreviated as PP-based TPO). PP-based TPO has a good compatibility with a propylene-based resin because the hard segment is made of polypropylene, and is uniformly finely dispersed when blended with the propylene-based resin. When an active energy ray is irradiated to a composition in which PP-based TPO is blended with the propylene-based resin, the finely dispersed PP-based TPO soft segments are preferentially crosslinked, so that a dense and uniform crosslinked structure is contained in the composition. Is built.

  Since the adhesive tape of the present invention has a dense and uniform cross-linking structure, it does not melt completely and keeps a certain thickness when heat-sealed to bond the outer packaging material and the terminal. it can. Therefore, a short circuit due to the proximity of the barrier layer of the outer packaging material and the terminal can be prevented. Moreover, since the ratio of the propylene origin component in a resin composition is high, the adhesiveness with respect to PP type | system | group outer packaging material is also ensured.

It is typical sectional drawing which shows an example of the adhesive tape of this invention. It is typical sectional drawing (A) of an example of a nonaqueous electrolyte battery, and the elements on larger scale of the a-a 'cross section (B).

The adhesive tape of the present invention is formed from a resin composition in which a PP-based TPO is blended with a propylene-based resin.
<Propylene resin>
The propylene-based resin used in the present invention is a polymer having a propylene-derived component of 50 mol% or more, and produced by a metallocene catalyst, a Ziegler-Natta catalyst, or the like, a propylene homopolymer, a copolymer of propylene and an α-olefin. A coalescence etc. can be illustrated. Examples of the copolymer of propylene and α-olefin include propylene-ethylene, propylene-butene copolymer, propylene-ethylene-butene terpolymer.

<Propylene-based thermoplastic elastomer (PP-based TPO)>
The propylene-based thermoplastic elastomer used in the present invention is an elastomer having polypropylene as a hard segment and ethylene-propylene-diene rubber, ethylene-propylene rubber, butyl rubber or the like as a soft segment, and the end of the soft segment is bound by the hard segment. Has a structured. Since the hard segment acts as a physical cross-linking point at room temperature, it has the same properties as rubber. However, when the temperature is raised, the hard segment melts and loses its function as a cross-linking point, and thus exhibits thermoplasticity.
PP-based TPO has (1) a conventional elastomer that disperses in an island structure of 1 μm or more with respect to the propylene component when blended with the propylene-based resin, and (2) is dispersed in nano-order with respect to the propylene component. Although there are nano-dispersed elastomers, the PP-based TPO used in the present invention is particularly preferably a nano-dispersed elastomer. By using the nano-dispersed elastomer, the cross-linked structure in the adhesive tape can be made denser. Nano-dispersed elastomers include Tough Selenium (trademark) manufactured by Sumitomo Chemical Co., Ltd., Toughmer (trademark) (PN series) manufactured by Mitsui Chemicals, Inc., and Versify (trademark) manufactured by The Dow Chemical Company. An example is Vistamax (trademark) manufactured by ExxonMobil Chemical Company.

  The blending ratio of the propylene-based resin and PP-based TPO is not particularly limited, but propylene-based resin: PP-based TPO = 90 to 50:10 to 50 (weight ratio) is preferable. If the blending ratio of PP-based TPO is smaller than the above range, there is a possibility that sufficient short-circuit prevention effect may not be obtained even if it is cross-linked, and conversely if larger than the above range, adhesion to PP-based outer packaging material may be reduced. is there.

<Manufacturing method>
The tape for terminal bonding of the present invention is obtained by forming the above-mentioned (1) resin composition comprising a propylene-based resin and PP-based TPO into a film shape, then (2) irradiating with active energy rays, and (3) slit processing. Can be manufactured.
(1) As a specific method for forming a resin composition comprising a propylene-based resin and PP-based TPO into a film, the propylene-based resin and PP-based TPO are supplied to an extruder and melt-kneaded by the extruder. Thereafter, a T-die (or inflation) extrusion method for forming a film from a flat (or annular) die will be exemplified. If this method is used, it can be performed consistently from kneading of propylene-based resin and PP-based TPO to film formation.
Next, (2) active energy rays are irradiated to the obtained film-like molded product. The active energy ray can be used without particular limitation as long as it is an energy ray that affects the electron trajectory of the irradiated object. For example, an electron beam, γ-ray, ultraviolet ray, infrared ray, or the like can be used. However, in view of the efficiency of crosslinking, it is most preferable to irradiate an electron beam among the above-described active energy rays. By irradiating the electron beam at 50 to 100 kV and 50 to 300 kGy, a uniform and dense cross-linked structure can be imparted to the film-like molded product.
Finally, (3) slitting is performed. The width of the adhesive tape may be appropriately determined according to the shape of the terminal or battery, but is generally 5 to 50 mm.
In addition, the manufacturing method of the adhesive tape of this invention is not limited to the method mentioned above.

<Multilayer adhesive tape>
Although the case where the adhesive tape of the present invention is a single layer has been described above, the present invention is not limited to this. As shown in FIG. 1, the adhesive tape of the present invention has two layers having an adhesive tape 101 composed only of the above-described active energy ray-crosslinked layer (hereinafter, crosslinked layer) 11 and a heat seal layer 12 on one side of the crosslinked layer 11. The adhesive tape 102 may be a three-layer tape 103 having heat seal layers 12 and 13 on both sides of the cross-linked layer 11. The resin forming the heat seal layers 12 and 13 is not particularly limited, but it is desirable that the same propylene-based resin as that of the crosslinked layer 11 is a main component in consideration of adhesiveness with the crosslinked layer 11.
The two-layer tab tape 102 composed of the heat seal layer 12 / cross-linked layer 11 is formed by using a coextrusion method or the like, after forming a two-layer film of the heat seal layer / cross-link layer composed of propylene-based resin and PP-based TPO, It can be manufactured by irradiating an active energy ray from the cross-linking layer side to give a cross-linking structure only to the cross-linking layer and then performing slit processing.

In addition, the adhesive tape 103 having a three-layer structure of heat seal layer 12 / cross-linked layer 11 / heat seal layer 13 is formed by separately forming a cross-linking film made of propylene-based resin and PP-based TPO and a heat-sealing film. Then, only the film for crosslinking is irradiated with active energy rays, and these are then bonded and slit processed.
Moreover, after forming a three-layer film of a cross-linking layer / heat-sealing layer composed of a heat-sealing layer / propylene resin and PP-based TPO using a co-extrusion method, the active energy ray is irradiated and slit processing is performed. Can be manufactured. However, in this case, it is desirable to keep the irradiation amount of active energy rays low to such an extent that the heat seal layer 12 and the heat seal layer 13 do not deteriorate (crosslink or decompose). It is desirable to use a nano-dispersed elastomer as the PP-based TPO in order to prevent the cross-linked layer 11 from approaching the barrier layer and the terminal of the laminate film while keeping the irradiation amount of the active energy ray low. When a nano-dispersed elastomer is used as the PP-based TPO, since the resulting crosslinked structure is dense, the proximity between the barrier layer and the terminal can be suppressed even if the degree of crosslinking is low.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. The performance of the examples and comparative examples was evaluated by the following methods.
<Short-circuit prevention performance>
Each adhesive tape was pressurized with a probe, and the shape retention of the adhesive tape was measured. A pressure of 0.5 MPa was applied to the probe, and the surface temperature of the adhesive tape was raised from 25 ° C. to 250 ° C. at 10 ° C./min. The shape retention rate is evaluated as (b / a) × 100 when the thickness of the adhesive tape before pressing with the probe is a, and the thickness after pressurizing by heating up to 250 ° C. is (b / a) × 100. did. The larger the shape retention rate, the smaller the thermal deformation at the time of heat sealing, so that the proximity between the barrier layer of the laminate film and the terminal can be prevented, and the short circuit prevention performance is excellent.
<Peel strength>
As a laminate film, prepare a 5-layer PP-based outer packaging material consisting of a polyethylene terephthalate / nylon laminate, a barrier layer made of aluminum, and a heat seal layer made of acid-modified polypropylene / polypropylene. prepare. Next, the terminals are sandwiched from above and below with an adhesive tape, and a laminate film is further applied from above and below, a seal bar heated to 190 ° C. from above and below is filled, and heat sealing is performed at a sealing pressure of 1.0 MPa for 3 seconds. Thereafter, the obtained sample was cut to a width of 15 mm (cut in a direction perpendicular to the heat seal direction), and the upper and lower laminated films were pulled in the 180 ° direction, and the tensile tester (manufactured by Shimadzu Corp., Autograph) was used. The peel strength was measured. The greater the peel strength, the better the adhesion to the PP-based outer packaging material.

[Example 1]
70% by weight of a propylene resin (hereinafter referred to as b-PP) obtained by block copolymerization of an ethylene component with a propylene component and 30% by weight of PP-based TPO which is a nano-dispersed elastomer are supplied to a single screw extruder, A film was formed by a T-die extrusion method, and electron beam irradiation was performed at 70 kV and 100 kGy). The obtained film-like molded product was slit to a width of 15 mm to obtain the adhesive tape of the present invention. The results of the short-circuit prevention performance and peel strength of the adhesive tape are shown in Table 1.

[Comparative Example 1]
An adhesive tape was obtained in the same manner as in Example 1 using only b-PP. Table 1 shows the results of evaluating the shape retention and adhesion of the adhesive tape.

[Comparative Example 2]
Instead of PP-based TPO that is a nano-dispersed elastomer, the same procedure as in Example 1 was performed except that 30 wt% of an ethylene-based thermoplastic elastomer having polyethylene as a hard segment (hereinafter referred to as PE-based TPO) was added. An adhesive tape was obtained. Table 1 shows the evaluation results of the shape retention performance and peel strength of the adhesive tape.

[Comparative Example 3]
An adhesive tape was obtained in the same manner as in Example 1 except that 30% by weight of linear ultra-low density polyethylene (hereinafter referred to as V-LDPE) was added instead of PP-based TPO which is a nano-dispersed elastomer. . Table 1 shows the evaluation results of the shape retention performance and peel strength of the adhesive tape.

It can be seen that the adhesive tape obtained by forming a film from a resin composition in which PP-based TPO is blended with b-PP and irradiating it with an electron beam has a high thickness residual ratio and is excellent in short-circuit prevention performance. Also, the peel strength is high and the first purpose of the adhesive tape (adhesiveness between the terminal and the laminate film) is also achieved.
The adhesive tape (Comparative Example 1) made only of b-PP had extremely poor short-circuit prevention performance. This seems to be because a crosslinked structure was hardly constructed in the propylene-based resin layer.
The adhesive tape (Comparative Example 2) made of a resin composition in which PE-based TPO was blended with b-PP also had extremely poor short-circuit prevention performance. This is probably because the ethylene component of PE-based TPO was attracted to the ethylene component of b-PP, and PE-based TPO was not uniformly dispersed. As a result of preferentially cross-linking PE-based TPO present locally, it is presumed that only a local cross-linked structure was constructed in the PP resin, and the short-circuit preventing performance was not exhibited. Moreover, since the ratio of the ethylene-derived component was high, the composition had low peel strength.
The adhesive tape (Comparative Example 3) made of a resin composition in which V-LDPE is blended with b-PP is superior to Comparative Examples 1 and 2, but is not as effective as Example 1. This seems to be because the dispersibility of V-LDPE with respect to b-PP was superior to that of Comparative Examples 1 and 2, but was not as high as that of Example 1. Moreover, since the ratio of the ethylene-derived component was high, the composition had low peel strength.

  The adhesive tape of the present invention is used for the purpose of bonding a laminate film, which is an outer packaging material, and a terminal in various batteries such as a lithium ion battery, a lithium ion capacitor, an all-solid battery, and a sodium battery that are enclosed by a laminate film. be able to.

101, 102, 103 Terminal adhesive tape 11 Cross-linked layer 12, 13 Heat seal layer 20 Nonaqueous electrolyte battery 21 Terminal adhesive tape 22 Laminate film 23 Positive electrode terminal 24 Negative electrode terminal 25 Positive electrode 26 Negative electrode 27 Separator

Claims (2)

In a battery encased by a laminate film, a terminal bonding tape for bonding the laminate film and a terminal,
Propylene resin consists of propylene-based thermoplastic elastomer resin composition formulated, and have a crosslinked structure, wherein the propylene-based thermoplastic elastomer, a hard segment of polypropylene, consists of a soft segment, the hard segment On the other hand, a tape for terminal bonding, wherein the soft segment is a nano-dispersed elastomer in which the soft segment is dispersed in nano-order . After molding the resin composition of the propylene-based thermoplastic elastomer to the propylene resin is blended into a film, the manufacturing method of the terminal adhesive tape according to claim 1, characterized in that an active energy ray is applied .