JP7168323B2 - Heat-expandable fire-resistant sheet and use of the heat-expandable fire-resistant sheet in battery - Google Patents

Description

The present invention relates to a thermally expandable refractory sheet and the use of the thermally expandable refractory sheet in a battery.

Various types of batteries represented by lithium-ion batteries may cause disasters such as fire and smoke when they reach high temperatures. In order to minimize such disasters, it is important to take measures to make it difficult for the heat of the battery, which has reached an abnormally high temperature, to be transmitted to the surrounding batteries and the housing containing the batteries.

In some cases, a heat-expandable fire-resistant material is used around the battery in order to reduce damage in the event of a fire breaking out from the battery. For example, Patent Literature 1 discloses a battery cell in which a portion of the outside of the battery cell is covered with a fire resistant coating. Fire resistant coatings may be ablative, intumescent or endothermic coatings, commercially available polyurethane-based coatings being exemplified.

Special table 2013-528911

On the other hand, in small electronic devices such as mobile terminals, the space for the battery is very limited, so there is a demand for thinner heat-expandable fireproof materials. However, thinning the heat-expandable refractory material causes a problem of strength, and it has been difficult to thin the heat-expandable refractory material while maintaining its strength. In order to maintain the strength, it is conceivable to relatively increase the content of the matrix resin that constitutes the thermally expandable refractory material. However, if the matrix resin content is relatively increased, sufficient fire resistance cannot be obtained.

An object of the present invention is to provide a thermally expandable fire-resistant sheet that has excellent fire resistance and is thin but has excellent strength.

In order to solve the above problems, the following aspects of the present invention are provided.
[1] A thermally expandable fireproof sheet containing a matrix resin and thermally expandable graphite, containing 5% by mass or more of the thermally expandable graphite, and having a thickness of 1200 μm or less, A thermally expandable fireproof sheet, wherein a thickness T (μm) of the thermally expandable fireproof sheet and an average aspect ratio R of the thermally expandable graphite satisfy a relationship of T×R≧800.
[2] The thermally expandable fireproof sheet according to Item 1, further containing an inorganic filler.
[3] The thermally expandable fireproof sheet according to Item 1 or 2, wherein the matrix resin is one or more selected from the group consisting of thermoplastic resins, thermoplastic elastomers and rubbers.
[4] The thermally expandable fireproof sheet according to any one of Items 1 to 3, wherein the matrix resin contains an ethylene-vinyl acetate copolymer (EVA).
[5] A fireproof material for batteries comprising the heat-expandable fireproof sheet according to any one of [1] to [4].
[6] Use of the heat-expandable fireproof sheet according to any one of items 1 to 4 in a battery.
[7] Use according to item 6, wherein the battery is a battery for electronic equipment.
[8] A battery comprising a battery cell and the heat-expandable fireproof sheet according to any one of Items 1 to 4 provided on the surface of the battery cell.

ADVANTAGE OF THE INVENTION According to this invention, while having the outstanding fire resistance, the thermal expansion fire-resistant sheet|seat excellent in intensity|strength although thin can be provided. Since this thermally expandable fireproof sheet has sufficient strength and sufficient fire resistance even though it is thin, it can impart excellent fire resistance to batteries in small electronic devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a fire-resistant multilayer sheet in which a substrate is laminated on the thermally expandable fire-resistant sheet of the present invention; 1 is a schematic vertical cross-sectional view of an example of a battery module to which the thermally expandable fireproof sheet of the present invention is applied; FIG. FIG. 3 is a schematic longitudinal sectional view of a battery pack including the battery module of FIG. 2; FIG. 2 is a schematic plan view of an example in which the thermally expandable fireproof sheet of the present invention is applied to a smartphone battery. FIG. 4 is a schematic plan view of another example in which the thermally expandable fireproof sheet of the present invention is applied to the battery of a smartphone. FIG. 4 is a schematic plan view of another example in which the thermally expandable fireproof sheet of the present invention is applied to the battery of a smartphone.

An embodiment in which the present invention is embodied in a thermally expandable fireproof sheet will be described below.

The resin composition constituting the thermally expandable fireproof sheet of the present invention contains a matrix resin and thermally expandable graphite.

[Matrix resin]
Matrix resins include, for example, thermoplastics, thermosets, elastomers, rubber materials, and combinations thereof.

Examples of thermoplastic resins include polyolefin resins such as polypropylene resins, polyethylene resins, poly(1-)butene resins and polypentene resins, polyester resins such as polyethylene terephthalate, polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, and ethylene. Synthetic resins such as vinyl acetate copolymer (EVA), polycarbonate resin, polyphenylene ether resin, (meth)acrylic resin, polyamide resin, polyvinyl chloride resin (PVC), novolak resin, polyurethane resin, and polyisobutylene can be used.

Examples of thermosetting resins include synthetic resins such as polyurethane resins, phenol resins, epoxy resins, urea resins, melamine resins, unsaturated polyester resins, and polyimides.

Examples of elastomers include olefin-based elastomers, styrene-based elastomers, ester-based elastomers, amide-based elastomers, vinyl chloride-based elastomers, and combinations thereof.

Rubber substances include natural rubber, isoprene rubber, butadiene rubber, 1,2-polybutadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM ), chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, polyvulcanized rubber, non-vulcanized rubber, silicone rubber, fluororubber, urethane rubber, and the like.

One or more of these synthetic resins and/or rubber substances can be used.

Among these synthetic resins and/or rubber substances, PVC and EVA are preferable in terms of moldability. Unvulcanized rubbers such as butyl rubber and polyolefin resins are preferred in order to obtain soft and rubbery properties. PVC is preferred in terms of fire resistance. Epoxy resins are preferable from the viewpoint of improving the flame retardancy of the resin itself and improving the fireproof performance.

[Thermal expandable graphite]
Thermally expandable graphite is a conventionally known substance that expands when heated, and is produced by treating powders of natural flake graphite, pyrolytic graphite, Kish graphite, etc. with an inorganic acid and a strong oxidizing agent to form a graphite intercalation compound. is. Inorganic acids include concentrated sulfuric acid, nitric acid, selenic acid and the like. Strong oxidizing agents include concentrated nitric acid, perchloric acid, perchlorate, permanganate, bichromate, hydrogen peroxide and the like. Thermally expandable graphite is a crystalline compound that retains the layered structure of carbon.

The thermally expandable graphite may optionally be neutralized. That is, the thermally expandable graphite obtained by acid treatment as described above is further neutralized with ammonia, lower aliphatic amines, alkali metal compounds, alkaline earth metal compounds, or the like.

The thermally expandable graphite obtained by acid treatment as described above may be further neutralized with ammonia, lower aliphatic amines, alkali metal compounds, alkaline earth metal compounds and the like.

The content of the thermally expandable graphite in the thermally expandable fireproof sheet of the present invention is not particularly limited, but is 5% by mass or more, more preferably 15% by mass or more. When the content of thermally expandable graphite is 5% by mass or more, expansion suitable for preventing the passage of fire is obtained. Although the upper limit of the content of thermally expandable graphite is not particularly limited, it is preferably 50% by mass or less from the viewpoint of mechanical strength.

The particle size of the thermally expandable graphite is preferably 20-200 mesh. When the particle size is 200 mesh or smaller, the degree of expansion of the graphite is sufficient to obtain an expanded heat insulating layer. Good physical properties.

The average aspect ratio of the thermally expandable graphite is not particularly limited, but is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. Although the upper limit of the average aspect ratio of the thermally expandable graphite is not particularly limited, it is preferably 1000 or less from the viewpoint of preventing cracking of the thermally expandable graphite. The thermally expandable graphite having an average aspect ratio of 2 or more contributes to high expandability of the resin composition and high residue hardness after combustion.

The aspect ratio is defined as the maximum dimension (major axis) of the thermally expandable graphite piece divided by the minimum dimension (minor axis). Then, the aspect ratio is measured for 10 or more expanded graphite flakes, and the average value is defined as the average aspect ratio. The major axis and minor axis of thermally expandable graphite can be measured using, for example, a field emission scanning electron microscope (FE-SEM).

[Inorganic filler]
The resin composition constituting the thermally expandable fireproof sheet of the present invention may further contain an inorganic filler. When the expansion heat insulating layer is formed, the inorganic filler increases the heat capacity and suppresses heat transfer, and acts like an aggregate to improve the strength of the expansion heat insulating layer. The inorganic filler is not particularly limited, and examples thereof include metal oxides such as alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, and ferrite; calcium hydroxide, magnesium hydroxide, Metal hydroxides such as aluminum hydroxide and hydrotalcite; Metal carbonates such as basic magnesium carbonate, calcium carbonate, magnesium carbonate, zinc carbonate, strontium carbonate and barium carbonate; Inorganic phosphates as flame retardants; Calcium sulfate , gypsum fiber, calcium salts such as calcium silicate; silica, diatomaceous earth, dawsonite, barium sulfate, talc, clay, mica, montmorillonite, bentonite, activated clay, sepiolite, imogolite, sericite, glass fiber, glass beads, silica balloon , aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fiber, carbon balloon, charcoal powder, various metal powders, potassium titanate, magnesium sulfate, lead zirconate titanate, zinc stearate, calcium stearate, aluminum borate , molybdenum sulfide, silicon carbide, stainless steel fibers, zinc borate, various magnetic powders, slag fibers, fly ash, dewatered sludge, and the like. One or more of these inorganic fillers can be used.

The particle size of the inorganic filler is preferably 0.5-100 μm, more preferably 1-50 μm. When the content of the inorganic filler is small, the dispersibility greatly affects the performance, so it is preferable to use a small particle size. , is preferably 0.5 μm or more. When the content is large, the viscosity of the resin composition increases and the moldability decreases as the filling progresses, but the viscosity of the resin composition can be reduced by increasing the particle size. A large diameter is preferable, but if the particle diameter exceeds 100 μm, the surface properties of the molded article and the mechanical performance of the resin composition may be deteriorated.

Commercially available inorganic fillers include, for example, aluminum hydroxide with a particle size of 1 μm “H-42M” (manufactured by Showa Denko KK), particle size of 18 μm “H-31” (manufactured by Showa Denko KK); calcium carbonate; Examples thereof include "Whiten SB Red" (manufactured by Shiraishi Calcium Co., Ltd.) having a particle size of 1.8 µm, and "BF300" (manufactured by Shiraishi Calcium Co., Ltd.) having a particle size of 8 µm. In addition, it is more preferable to use a combination of an inorganic filler having a large particle size and a filler having a small particle size.

Although the content of the inorganic filler in the heat-expandable fireproof sheet is not particularly limited, it is preferably 1 to 50% by weight.

Moreover, the total content of the thermally expandable graphite and the inorganic filler in the thermally expandable fireproof sheet is preferably 5 to 80% by weight. It is preferably 5% by weight or more in terms of satisfying the amount of residue after combustion and obtaining sufficient fire resistance performance, and preferably 80% by weight or less in terms of maintaining mechanical properties.

[Phosphorus compound]
Furthermore, the resin composition that constitutes the thermally expandable fireproof sheet of the present invention can further contain a phosphorus compound in addition to each of the above components in order to increase the strength of the expansion heat insulating layer and improve the fireproof performance. . Phosphorus compounds act as flame retardants. The phosphorus compound is not particularly limited. Phosphate metal salts such as potassium phosphate and magnesium phosphate; ammonium polyphosphate; and compounds represented by the following chemical formula (1). Among these, red phosphorus, ammonium polyphosphate, and compounds represented by the following chemical formula (1) are preferable from the viewpoint of fire resistance, and ammonium polyphosphate is more preferable from the viewpoints of performance, safety, cost, and the like.

In chemical formula (1), R ¹ and R ³ are the same or different and represent hydrogen, a linear or branched alkyl group having 1 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms. R ² is a hydroxyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, a linear or branched alkoxyl group having 1 to 16 carbon atoms, an aryl group having 6 to 16 carbon atoms, or carbon It represents an aryloxy group of numbers 6-16.

Commercially available red phosphorus can be used as the red phosphorus, but from the viewpoint of safety such as moisture resistance and no spontaneous ignition during kneading, red phosphorus particles whose surfaces are coated with a resin are preferably used.
The ammonium polyphosphate is not particularly limited, and examples thereof include ammonium polyphosphate, melamine-modified ammonium polyphosphate and the like, but ammonium polyphosphate is preferably used from the viewpoint of handleability and the like. Examples of commercially available products include "AP422" and "AP462" manufactured by Clariant, "FR CROS 484" and "FR CROS 487" manufactured by Budenheim Iberica.

The compound represented by the chemical formula (1) is not particularly limited, and examples thereof include methylphosphonic acid, dimethyl methylphosphonate, diethyl methylphosphonate, ethylphosphonic acid, n-propylphosphonic acid, n-butylphosphonic acid, and 2-methylpropylphosphonic acid. acid, t-butylphosphonic acid, 2,3-dimethyl-butylphosphonic acid, octylphosphonic acid, phenylphosphonic acid, dioctylphenylphosphonate, dimethylphosphinic acid, methylethylphosphinic acid, methylpropylphosphinic acid, diethylphosphinic acid, dioctylphosphine acid, phenylphosphinic acid, diethylphenylphosphinic acid, diphenylphosphinic acid, bis(4-methoxyphenyl)phosphinic acid and the like. Among them, t-butylphosphonic acid is expensive, but is preferred in terms of high flame retardancy. One or more of the phosphorus compounds can be used.

If the amount of the phosphorus compound added is small, the flame retardance tends to decrease, and if it is large, the moldability tends to decrease. is preferably

[Plasticizer]
The resin composition constituting the thermally expandable fireproof sheet of the present invention can further contain a plasticizer.

The plasticizer is not particularly limited as long as it is a plasticizer that is generally used when producing polyvinyl chloride resin moldings. Specifically, for example, phthalate plasticizers such as di-2-ethylhexyl phthalate (DOP), dibutyl phthalate (DBP), diheptyl phthalate (DHP), diisodecyl phthalate (DIDP),
Fatty acid ester plasticizers such as di-2-ethylhexyl adipate (DOA), diisobutyl adipate (DIBA), dibutyl adipate (DBA); epoxidized ester plasticizers such as epoxidized soybean oil; polyesters such as adipate and adipate polyester plasticizers; trimellitate ester plasticizers such as tri-2-ethylhexyl trimellitate (TOTM) and triisononyl trimellitate (TINTM); and process oils such as mineral oil. One or more plasticizers can be used.

When the content of the plasticizer is too small, the extrusion moldability tends to be lowered, and when the content is too high, the molded article obtained tends to be too soft. Therefore, although the content of the plasticizer is not limited, it is preferably 0 to 40% by mass, more preferably 5 to 35% by mass in the thermally expandable fireproof sheet. In one embodiment, the content of the plasticizer in the thermally expandable fireproof sheet is 0 to 20% by mass. In a further embodiment, the plasticizer content in the thermally expandable refractory sheet is 5-20% by weight.

[Other ingredients]
Examples of the above-mentioned other components that can be contained in the thermally expandable fireproof sheet of the present invention include antioxidants such as phenolic, amine, and sulfur antioxidants, and metal damage prevention agents, as long as they do not impair the physical properties of the sheet. agents, antistatic agents, stabilizers, cross-linking agents, lubricants, softeners, pigments and the like.

Although the thickness of the thermally expandable fireproof sheet of the present invention is not particularly limited, it is preferably 1200 μm or less, more preferably 60 to 1000 μm. The "thickness" of the thermally expandable fireproof sheet referred to in this specification refers to the average thickness of three points in the width direction of the thermally expandable fireproof sheet.

The present inventors have found that the thickness of the thermally expandable refractory sheet is T (μm), the average aspect ratio of the thermally expandable graphite is R, and the relationship T×R≧800 is satisfied. It was found that the sheet has sufficient strength even if it is thin. More preferably, T×R≧1000.

Although the elongation at break of the thermally expandable fireproof sheet is not particularly limited, it is preferably 70% or more in terms of the strength of the thermally expandable fireproof sheet.

Also, the thermally expandable fireproof sheet is not particularly limited as long as it is thermally insulated by the expansion layer when exposed to high temperatures such as in the event of a fire, and the expansion layer has strength. The expansion ratio after heating at 600° C. for 30 minutes is preferably 3 to 50 times, more preferably 15 to 40 times, and even more preferably 20 to 35 times. When the expansion ratio is 3 times or more, the burnt-out portion of the matrix component can be sufficiently buried, and when the expansion ratio is 50 times or less, the strength of the expansion layer is maintained and the effect of preventing flame penetration is obtained. be kept. The expansion ratio is calculated as (thickness of test piece after heating)/(thickness of test piece before heating) of the test piece of the thermally expandable fireproof sheet.

The heat-expandable refractory sheet is prepared by mixing the above matrix component, heat-expandable graphite, and other optional components with a single-screw extruder, twin-screw extruder, injection molding machine, Banbury mixer, kneader mixer, kneading roll, and lykai machine. , a planetary stirrer, or the like, and coating or molding the refractory resin composition. Molding includes press molding, extrusion molding and injection molding. Coating or molding is well known in the art.

Residual hardness can be measured by supplying the thermally expandable fireproof sheet after heating to a compression tester (manufactured by Kato Tech Co., Ltd., "Finger Filling Tester") and compressing it with an indenter. Although the hardness of the residue is not particularly limited, it is preferably 0.2 kgf/cm ² or more from the viewpoint of fire resistance.

As shown in FIG. 1, the thermally expandable fireproof sheet of the present invention may be further laminated or layered with a substrate. The substrate is laminated on one side or both sides of the thermally expandable fireproof sheet. FIG. 1 is a schematic cross-sectional view of a fire-resistant multilayer sheet 1 in which a heat-expandable fire-resistant sheet 4 and a base material 8 of the present invention are laminated.

The substrate may be a combustible layer, a quasi-noncombustible layer, or a noncombustible layer. Although the thickness of the base material is not particularly limited, it is, for example, 5 μm to 1 mm.

Materials used for the combustible layer include, for example, one or more of cloth materials, paper materials, wood materials, natural resins, synthetic resins, and the like.

Materials used for the quasi-noncombustible layer or the noncombustible layer include, for example, one or more of metals, inorganic materials, and the like.

Examples of cloth materials include woven fabrics such as cotton, silk, nylon, polyester and polypropylene, and non-woven fabrics.

Examples of the paper material include fibrous substances extracted from plants such as wood, and paper obtained by dispersing chemical fibers in a dispersion medium such as water, filtering the dispersion to form a uniform layer, and then drying. be done.

Examples include processed paper obtained by coating paper with a paint, a water-repellent agent, etc., and corrugated cardboard in which corrugated paper is sandwiched between flat papers called liner and adhered.

Examples of lumber include not only wood materials obtained from natural wood, but also laminated lumber containing wood materials, laminated lumber, laminated wood boards, and the like.

Natural resins include, for example, cellulose derivatives, gelatin, alginates, chitosan, pullulan, pectin, carrageenan, proteins, tannins, lignin, polymers containing rosin acid as main components, and natural rubbers.

Examples of synthetic resins include isoprene rubber, butadiene rubber, 1,2-polybutadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene-propylene rubber, chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, and silicone. Synthetic rubber such as rubber, fluorine rubber, urethane rubber, polyisobutylene rubber, butyl chloride rubber, etc.
Polyolefin resins such as polypropylene resin, polyethylene resin, poly(1-)butene resin, polypentene resin,
Polystyrene resin, acrylonitrile-butadiene-styrene resin, polycarbonate resin, acrylic resin, polyamide resin, polyvinyl chloride resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene ether resin, wholly aromatic polyester resin, polyethersulfone resin, phenolic resin , polyurethane resins, epoxy resins, and the like.

Examples of metals include aluminum, iron, stainless steel, tin, lead, tin-lead alloys, and copper.

Moreover, it is preferable to use a metal foil as the metal, and examples of the metal foil include aluminum foil, iron foil, stainless steel foil, tin foil, lead foil, tin-lead alloy foil, and copper foil.

Examples of inorganic materials include glass wool, rock wool, ceramic wool, gypsum fiber, carbon fiber, stainless steel fiber, slag fiber, silica-alumina fiber, alumina fiber, silica fiber, and zirconia fiber. The inorganic fiber layer preferably uses an inorganic fiber cloth using the inorganic fibers. Moreover, it is preferable to use the inorganic fiber laminated with the metal foil for the inorganic fiber layer.

As specific examples of metal foil-laminated inorganic fibers, for example, aluminum foil-laminated glass cloth, copper foil-laminated glass cloth, and the like are more preferable.

In one embodiment, the substrate is a nonwoven. In this case, it is excellent in terms of protection of the expansive material such as prevention of breakage.

As used herein, the term "battery" refers to a lithium ion battery, a lithium ion polymer battery, a nickel-hydrogen battery, a lithium-sulfur battery, a nickel-cadmium battery, a nickel-iron battery, a nickel-zinc battery, a sodium-sulfur battery, It means a secondary battery such as a lead-acid battery or an air battery. "Battery" is used interchangeably with "battery" herein.

The above lithium ion batteries are classified into cylindrical type, rectangular type, and laminated type depending on the shape of the cell.

As used herein, the term “battery cell” refers to a structural unit of a battery in which a positive electrode material, a negative electrode material, a separator, a positive electrode tab or a positive electrode terminal, a negative electrode tab or a negative electrode terminal, and the like are accommodated in an exterior member.

When the battery cell is cylindrical, it refers to the structural unit of the battery in which the positive electrode material, negative electrode material, separator, positive electrode tab, negative electrode tab, insulating material, gas discharge valve, gasket, positive electrode cap, etc. are housed in the outer can.

When the battery cell is prismatic, it refers to a structural unit of a battery in which a positive electrode material, a negative electrode material, a separator, a positive electrode terminal, a negative electrode terminal, an insulating material, a gas discharge valve, and the like are housed in an outer can.

When the battery cell is of a laminate type, it refers to a structural unit of a battery in which a positive electrode material, a negative electrode material, a separator, a positive electrode tab, a negative electrode tab, etc. are housed in an exterior film. Examples of the exterior film include an aluminum film laminated with a polyethylene terephthalate film.

As used herein, the term "battery module" refers to a unit of battery housing a plurality of battery cells in a housing, and the term "battery pack" refers to a housing housing a plurality of battery modules. In addition to the battery cells, necessary members such as electrical connection cables electrically connected to the battery cells are used inside the battery pack and the battery as needed.

FIG. 2 is a schematic longitudinal sectional view of an example of the battery module 1 to which the thermally expandable fireproof sheet 4 of FIG. 1 is applied.

A plurality of battery cells 3 (three cells are shown in the drawing) are housed in a housing 2 of the battery module 1 so as to be spaced apart from each other and extend in the vertical direction. , the thermally expandable fireproof sheet 4 of the present invention is arranged. Each thermally expandable fireproof sheet 4 is attached to one surface of the battery cell 3 .

The surface of one battery cell 3 is usually formed of an aluminum sheet laminated with a PET film, or a cylindrical metal or the like. As a method of installing the thermally expandable fireproof sheet 4 on at least one side (for example, one side or a pair of both sides) of the battery cell 3 partially or entirely, A method of sticking and fixing the surface of one battery cell 3 by self-adhesiveness of the expansive fireproof sheet 4, a method of laminating the battery cell 3 and the thermally expandable fireproof sheet 4 and then fixing them using a frame, etc. is mentioned.

Therefore, the heat-expandable fireproof sheet 4 has excellent heat dissipation during normal use of the battery, and can effectively dissipate the heat generated by the operation of the battery cells 3 . In addition, when the thermally expandable fireproof sheet 4 is heated due to abnormal heat generation or fire, the thermally expandable fireproof sheet 4 starts expanding even at a relatively low temperature, closing the space that serves as a flow path for fire or heat. , forming a heat insulating layer between adjacent battery cells 3 . Therefore, heat transfer or ignition from one battery cell 3 to an adjacent battery cell 3 can be prevented, suppressed, or delayed, and the safety of the battery is ensured.

The dimensions of the thermally expandable fireproof sheet 4 are not particularly limited, and can be changed according to the size of the battery cells 3 and the size of the space inside the battery module 1 .

The housing 2 is, for example, a housing made of metal or resin molding, but is not limited to this. In FIG. 2, the battery cells 3 and the thermally expandable fireproof sheet 4 are substantially flat rectangular parallelepipeds, and are arranged substantially parallel to each other. A space 5 is provided around the battery cell 3 and the heat-expandable fireproof sheet 4 in the housing 2, and a space is also provided between the battery cell 3 and the heat-expandable fireproof sheet 4 adjacent to the battery cell 3. 6 is provided. These spaces 5 and 6 act as air passages for the heat dissipation of the battery cells 3 . For example, the battery cell 3 may be heated during operation, but by securing such spaces 5 and 6, the battery cell 3 can be dissipated more quickly.

The thermally expandable fireproof sheet 4 functions as a heat insulating layer, and can prevent or delay heat transfer or ignition from one battery cell 3 to an adjacent battery cell 3, thereby improving the ignition retardancy of the battery module 1. safety is ensured.

FIG. 3 is a schematic longitudinal sectional view of a battery pack 10 having the battery module 1 of FIG. A housing 11 of the battery pack 10 accommodates a plurality of battery modules 1 (two modules are shown in the drawing). The housing 11 is, for example, a housing made of metal or resin molding, but is not limited to this. A thermally expandable fireproof sheet 4 is arranged between adjacent battery modules 1 . A plurality of battery modules 1 are arranged in series or in parallel to form a cylindrical battery.

When the heat-expandable fireproof sheet 4 is heated due to abnormal heat generation, fire, or the like, the heat-expandable fireproof sheet 4 expands. This closes off the space that serves as a flow path for fire and heat.

With such a configuration, even in the battery pack 10 of FIG. 2, the heat-expandable fireproof sheet 4 acts as a heat insulating material at high temperatures such as abnormal heat generation or fire, while ensuring air passages for heat dissipation of the battery cells 3. As a result, the battery module 1 and the battery pack 10 can demonstrate ignition retardancy, and the heat dissipation of the battery pack during normal times and safety at high temperatures can be combined. In addition, in FIGS. 2 and 3, the battery cell 3 and the thermally expandable fireproof sheet 4 may be in contact with each other, or may be separated by a space. Moreover, the spaces 5 and 6 may not exist.

Since the thermally expandable fireproof sheet of the present invention is thin but excellent in strength and has sufficient fire resistance, it is suitably used as a fireproof material for batteries housed in electronic devices such as mobile phones, smartphones, and tablet devices. be able to.

4 to 6 are plan views of examples in which the thermally expandable fireproof sheet of the present invention is applied to a smartphone battery.
FIG. 4 shows a state in which the lid 22 is removed from the main body 21 of the smart phone 20 . A main body 21 of the smartphone 20 has a substantially rectangular recess 22 , and a plurality of holes 23 (one at the top and bottom and two at the left and right in the drawing) are provided at the edges of the recess 22 . On the back side of the lid 22, the same number of protrusions (not shown) as the holes 23 are provided at positions corresponding to the holes 23. When the lid 22 is attached to the main body 21, the holes 23 and the protrusions are aligned. By fitting, the lid 22 is more firmly attached to the main body 21 . A substantially rectangular recess 24 is provided below the center of the recess 22 in the drawing, and a battery cell 25 is accommodated in the recess 24 . In addition, a thermally expandable fireproof sheet 4 is provided around the four sides of the battery cell 25 in the recess 24 . In FIG. 4, one thermally expandable fireproof sheet 4 is wrapped around four sides of the battery cell 25, but one thermally expandable fireproof sheet 4 may be attached to one side of the battery 25. good. In this example, since the thermally expandable fireproof sheet 4 is provided around the four sides of the battery cell 25, the thermally expandable fireproof sheet 4 prevents or suppresses heat transfer to the periphery of the battery cell 25 or ignition. , or can be delayed.
A camera 26 is built into the main body 21 of the smartphone 20, and an opening 27 through which the camera 26 is inserted is provided in a portion of the lid 22 corresponding to the camera 26 so that a photograph can be taken with the lid 22 attached to the main body 21. is provided.
FIG. 5 shows another arrangement of the thermally expandable fireproof sheet 4. FIG. In this example, the thermally expandable fireproof sheet 4 is provided on the upper surface of the battery cell 25 (the upper surface when the smartphone 20 is placed still) and the lower surface. Even in this case, the thermally expandable fireproof sheet 4 can prevent, suppress, or delay heat transfer to the surroundings of the battery cell 25 or ignition.
FIG. 6 shows another arrangement of the thermally expandable fireproof sheet 4. FIG. In this example, the thermally expandable fireproof sheet 4 is provided only on one side of the battery 25 . Even in this case, the thermally expandable fireproof sheet 4 forms a barrier between the battery cells 25 and the camera 26 and other electronic components inside the body 21, preventing heat transfer to the surroundings of the battery cells 25 or ignition. can be prevented, suppressed or delayed.
4 to 6, the thermally expandable fireproof sheet 4 may cover the entire surface of the battery cell 25 excluding the connection terminal portion, or may be arranged in another arrangement.
In addition to fireproof materials for batteries housed in electronic equipment, the thermally expandable fireproof sheet of the present invention can be used as fireproof materials for various batteries.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these.

(Examples 1 to 6, Comparative Examples 1 to 3)
A resin composition containing the matrix resin, thermally expandable graphite, flame retardant and plasticizer shown in Table 1 was supplied to a single screw extruder and extruded at 150° C., Examples 1 to 6 and Comparative Examples 1 to 1. A heat-expandable fireproof sheet No. 3 was obtained. The following components were used for each component.

EVA resin Product name EVAFLEX EV460, Mitsui DuPont Polychemicals Co., Ltd. Polyvinyl chloride resin Product name TK-1000, Shin-Etsu Chemical Co., Ltd. Butyl rubber Product name Butyl 065, JSR Corporation Thermally expandable graphite Product name EXP50T Nippon Graphite Industry Co., Ltd. Thermally expandable graphite Product name GREP-EG Tosoh Corporation Thermally expandable graphite GREP-EG (150 mesh) Tosoh Corporation Flame retardant AP422 (ammonium polyphosphate) Clariant Inorganic filler Calcium carbonate Whiten BF300 Bihoku Funka Co., Ltd. Plasticity Agent DIDP (diisodecyl phthalate) J-Plus

(Measurement of T and R)
Let T (μm) be the thickness of the thermally expandable fireproof sheet, and R be the average aspect ratio of the thermally expandable graphite. The thickness of the thermally expandable fireproof sheet was measured with a vernier caliper at three points each in the width direction and the machine direction of the sheet. Also, the average aspect ratio of the thermally expandable graphite was measured using a field emission scanning electron microscope (FE-SEM).

(Measurement of tensile strength)
It was measured according to the method of JIS K6767.

(elongation at break)
It was measured according to the method of JIS K6767.

(expansion ratio)
A test piece obtained by cutting the thermally expandable refractory sheet into a length of 100 mm and a width of 100 mm is supplied to an electric furnace, heated at 600 ° C. for 30 minutes, and then the thickness of the test piece is measured. thickness)/(thickness of test piece before heating) was calculated as the expansion ratio.

(residue hardness)
The heated test piece whose expansion ratio has been measured is supplied to a compression tester ("Finger Filling Tester" manufactured by Kato Tech Co., Ltd.), compressed at a rate of 0.1 cm/sec with an indenter of 0.25 cm ² , and fractured. Point stress was measured.

(Shape retention of residue hardness)
The residue hardness is an index of the hardness of the residue after expansion, but since the measurement is limited to the surface portion of the residue, it may not be an index of the hardness of the entire residue. Therefore, shape retention was measured as an index of the hardness of the entire residue. The shape retention of the residue was measured by holding both ends of the test piece whose expansion ratio was measured and lifting it by hand, and visually measuring the ease of collapse of the residue at that time. When the test piece was lifted without crumbling was evaluated as PASS, and when the test piece collapsed and could not be lifted, it was evaluated as FAIL.

Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications are possible based on the technical idea of the present invention.

For example, the configurations, methods, steps, shapes, materials, numerical values, etc., given in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, numerical values, etc., may be used if necessary. may be used.

Also, the configurations, methods, steps, shapes, materials, numerical values, etc. of the above-described embodiments can be combined with each other without departing from the gist of the present invention.

4 Thermally expandable fireproof sheet

Claims (9)

a thermally expandable fireproof sheet containing a matrix resin and thermally expandable graphite;
A fireproof multilayer sheet for batteries laminated with a base material (excluding those made of fluororesin or stretched polyester resin),
The heat-expandable refractory sheet contains 5% by mass or more of heat-expandable graphite, the thickness of the heat-expandable fire-resistant sheet is 1200 μm or less, and the average aspect ratio between the thickness T (μm) of the heat-expandable fire-resistant sheet and the heat-expandable graphite. A fire-resistant multilayer sheet for a battery, wherein R satisfies the relationship of T×R≧800. The fire-resistant multilayer sheet for batteries according to claim 1, wherein the thermally expandable fire-resistant sheet further contains an inorganic filler. The fireproof multilayer sheet for batteries according to claim 1 or 2, wherein the matrix resin is at least one selected from the group consisting of thermoplastic resins, thermoplastic elastomers and rubbers. The fireproof multilayer sheet for batteries according to any one of claims 1 to 3, wherein the matrix resin contains an ethylene-vinyl acetate copolymer (EVA). A fireproof material for batteries comprising the fireproof multilayer sheet for batteries according to any one of claims 1 to 4. Use of the fireproof multilayer sheet for batteries according to any one of claims 1 to 4 in a battery. Use according to claim 6, wherein the battery is a battery for electronic equipment. A battery comprising a housing, a plurality of battery cells housed in the housing, and a heat -expandable fire-resistant sheet provided on the surface of the battery cells, wherein the heat-expandable fire-resistant sheet is placed between adjacent battery modules. is placed and
A thermally expandable fireproof sheet containing a matrix resin and thermally expandable graphite,
The thermally expandable fireproof sheet contains 5% by mass or more of the thermally expandable graphite, has a thickness of 1200 μm or less, and has a thickness T (μm) of the thermally expandable fireproof sheet and the above A battery, wherein an average aspect ratio R of thermally expandable graphite satisfies a relationship of T×R≧800. The battery according to claim 8, which is a battery for electronic equipment.

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