JP7046346B2 - Laminates and their use - Google Patents

Description

The present invention relates to a laminate preferably used for an exterior member or the like of a lithium ion secondary battery (LiB).

LiB is widely used in the fields of mobile phones, notebook computers, video cameras, satellites, electric vehicles and the like, for example. The LiB is composed of a LiB cell main body composed of an electrode (positive electrode and a negative electrode), an electrolytic solution, and a separator, and an exterior member such as a tab terminal for packaging the electrode and a cell storage member.

Aluminum (Al) foil is often used for these LiB exterior parts. This Al foil is required to have strict reliability such as electrolytic solution resistance and HF resistance. Here, HF is generated by hydrolyzing an electrolyte such as LiPF ₆ with water remaining in a trace amount in the electrolytic solution due to moisture absorption or the like. Therefore, a method of providing a resin film on the surface of the Al foil to protect it from corrosion and the like has been proposed. For example, Patent Document 1 proposes a laminate in which a film made of chitosan is provided on the surface of an Al foil. Further, Patent Document 2 proposes an Al laminate in which a film made of modified PVA is provided on the surface of an Al foil.

The film made of chitosan or modified PVA has a problem of poor heat resistance. Therefore, Patent Documents 3 and 4 propose a PAl laminate in which a film made of polyamide-imide (PAI) having excellent heat resistance is provided on the surface of an Al foil.

Japanese Unexamined Patent Publication No. 2006-20257 International Publication 2012/128026 Japanese Unexamined Patent Publication No. 2005-297448 Japanese Unexamined Patent Publication No. 2016-126942

However, the Al laminate on which the PAI film is formed disclosed in the above document has a problem of poor adhesiveness to the Al foil, and lacks adhesive reliability when used as, for example, an exterior member of LiB. rice field.

Therefore, the present invention solves the above-mentioned problems, and an object of the present invention is to provide a laminate having high adhesive strength to Al foil and excellent adhesive reliability.

The present inventors have found that the above-mentioned problems can be solved by specifying the chemical structure of PAI, and have completed the present invention.

The present invention has the following object.
(1) A laminate in which a PAI film is formed on the surface of an Al foil, wherein the PAI is a copolymerized PAI using dimer acid as a carboxylic acid component.
(2) Use of the laminated body as a LiB exterior member.

The laminate of the present invention in which the PAI film is laminated on the Al foil of the present invention has excellent adhesive reliability and good electrolytic solution resistance, and therefore can be suitably used as a LiB exterior member or the like.

Hereinafter, the present invention will be described in detail.

PAI is a polymer having both an imide bond and an amide bond in the main chain, and a polymer having an intrinsic viscosity of 0.5 dl / g or more and a glass transition temperature (Tg) of 150 ° C. or more is heat resistant. And strength are preferable.

The PAI used in the PAI coating of the present invention is a copolymerized PAI using dimer acid as a carboxylic acid component. Such a PAI is a known PAI and can be obtained, for example, by the method described in JP-A-11-21454. That is, it can be obtained by dissolving trimellitic acid anhydride (TMA), which is a carboxylic acid component, dimer acid, and diisocyanate in a polymerization solvent and heating and stirring to proceed with the polymerization reaction. The carboxylic acid component and the diisocyanate are usually polymerized by using equimolar, but one component may be slightly increased or decreased as necessary. The polymerization temperature is usually 50 ° C. to 220 ° C., preferably 80 ° C. to 200 ° C.

In the polymerization of PAI, for example, amines such as triethylamine, lutidine, picolin and triethylenediamine, alkali metals such as lithium methoxide, sodium methoxide, potassium butoxide, potassium fluoride and sodium fluoride, and alkaline earth metals. It may be carried out in the presence of a catalyst such as a compound.

As the carboxylic acid component used for the polymerization of PAI, TMA and dimer acid are used, and TMA can partially replace a part thereof with another polyvalent carboxylic acid anhydride. Specific examples of the polyvalent carboxylic acid anhydride include pyromellitic acid anhydride, benzophenone tetracarboxylic acid anhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic acid anhydride, 3,3', 4, Examples thereof include 4'-diphenyltetracarboxylic acid anhydride and 4,4'-oxydiphthalic acid anhydride. These may be used alone or in combination of two or more.

Dimeric acid is a mixture of dicarboxylic acids mainly containing saturated or unsaturated dicarboxylic acids having 36 carbon atoms, and commercially available products can be used. Specific examples of commercially available products include "PRIPOL" manufactured by Croda Japan, "Haridimer" manufactured by Harima Chemicals, "EMPOL" manufactured by BASF Japan, and "Tsunodaime" manufactured by Tsukino Food Chemicals Co., Ltd. be able to. These may be used alone or in combination of two or more.

The copolymerization ratio of dimer acid is preferably 0.1 mol% or more and 30 mol% or less, and more preferably 0.5 mol% or more and 20 mol% or less with respect to the total carboxylic acid component. By copolymerizing the dimer acid in this way, strong adhesiveness to the Al foil can be ensured.

Specific examples of the diisocyanate include 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diaminodicyclohexylmethane diisocyanate, isophorone diisocyanate and the like, and MDI is preferable. These may be used alone or in combination of two or more.

The polymerization of PAI is preferably carried out in an amide-based solvent or a urea-based solvent. Specific examples of the amide-based solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, N, N-dimethylacetamide (DMAc) and the like. Specific examples of the urea-based solvent include tetramethylurea, tetraethylurea, dimethylethyleneurea, and dimethylpropyleneurea. Of these, NMP and DMAc are preferred. These may be used alone or in combination of two or more.

Fila can be added to the PAI solution obtained as described above. The type of filler is not limited, and organic fillers, inorganic fillers and mixtures thereof can be used. Specific examples of the organic filler include homopolymers such as styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or two or more copolymers, polytetrafluoroethylene, and the like. Examples thereof include particles made of a polymer such as tetrafluoroethylene-6 fluoride propylene copolymer, tetrafluoride ethylene-ethylene copolymer, and polyvinylidene fluoride. The organic filler can be used alone or in combination of two or more. Specific examples of the inorganic filler include particles made of an inorganic substance such as a metal oxide, a metal nitride, a metal carbide, a metal hydroxide, a carbonate, and a sulfate. Specific examples include powders made of alumina, silica, titanium dioxide, barium sulfate, calcium carbonate and the like. The inorganic filler can be used alone or in combination of two or more. The average particle size of the filler is not limited, but is preferably 0.01 μm or more and 2 μm or less. The average particle size can be measured by a measuring device based on the laser diffraction / scattering method.

Various coupling agents (silane type, aluminum type, titanate type, zirconate type, etc.) can be blended in the PAI solution to improve the adhesiveness.

Specific examples of the silane coupling agent include vinyl trichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-. Methacryloxypropylmethyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldi Ethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, n-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltri Methoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, 3-aminopropyl-methyl-diethoxysilane, 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-aminopropyl Trimethoxysilane, 3-aminopropyl-tris (2-methoxy-ethoxy-ethoxy) silane, N-methyl-3-aminopropyltrimethoxysilane, triaminopropyl-trimethoxysilane, 3-4,5-dihydroimidazolepropyl Trimethoxysilane, 3-methacryloxypropyl-trimethoxysilane, 3-mercaptopropyl-methyldimethoxysilane, 3-chloropropyl-methyl-dimethoxysilane, 3-cyanopropyl-triethoxysilane, hexamethyldisilazane, N, O -Bis (trimethylsilyl) acetamide, methyltrimethoxysilane, methyltriethoxysilane, ethyltrichlorosilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, amyltrichlorosilane, octyltriethoxysilane, phenyltrimethoxysilane, phenylotriethoxy Silane, Methyltri (methacryloyloxyethoxy) silane, Methyltri (glycidyloxy) silane, N-β (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, Octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium Chloride, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane, γ- Examples thereof include chloropropylmethyldiethoxysilane, trimethylsilylisocyanate, dimethylsilylisocyanate, methylsilyltriisocyanate, vinylsilyltriisocyanate, phenylsilyltriisocyanate, tetraisocyanatesilane, and ethoxysilaneisocyanate. It can be used alone or in combination of two or more.

Specific examples of the aluminate-based coupling agent include, for example, aluminum chelate compounds (aluminum ethylacetate acetate-alkylacetoacetate aluminum-diisopropyrate such as ethylacetoacetate aluminum-diisopropyrate, aluminum-tris (ethylacetate acetate), aluminum-monoacetyl. Acetate-bis (ethylacetacetate), aluminum-tris (acetylacetonate), aluminum-monoisopropoxy-monooleoxyethylacetate, aluminum-di-n-butoxide-monoethylacetoacetate, aluminum-di-iso (Propoxide-monoethylacetacetate, etc.), aluminum alcoholate (aluminum isopropylate, mono-sec-butoxyaluminum diisopropyrate, aluminum-sec-butyrate, aluminum ethylate, etc.) and the like can be mentioned. These can be used alone or in admixture of two or more.

Specific examples of the titanate-based coupling agent include isopropyltrioctanoyl titanate, isopropyldimethacrylisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropylisostearoyl dialicyl titanate, isopropyltri (dioctyl phosphate) titanate, and isopropyltricylphenyl. Titanium, Isopropyltris (Dioctylpyrophosphate) Titanium, Isopropyltri (n-aminoethyl-Aminoethyl) Titanium, Tetraisopropylbis (Dioctylphosphite) Titanium, Tetraoctylbis (Ditridecylphosphite) Titanium, Tetra (2,2) -Diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, dicumylphenyloxyacetate titanate, bis (dioctylpyrophosphate) oxyacetate titanate, tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2) -Ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium chili ethanolaminate, polyhydroxytitanium stearate, tetramethyl ortho Titanium, Tetraethyl Orthotitanate, Tetrapropyl Orthotitanate, Tetraisobutyl Orthotitanate, Stearyl Titanate, Cresyl Titanate Monomer, Cresyl Titanate Polymer, Di-Isopropoxy-bis- (2,4-Pentadionate) -Titanium (IV) , Di-isopropyl-bis-triethanolamino-titanate, octylene glycol titanate HV, tetra-n-butoxytitanium polymer, tri-n-butoxytitanium monostearate polymer, tri-n-butoxytitanium monostearate, etc. be able to. It can be used alone or in combination of two or more.

Specific examples of the zirconate-based coupling agent include tetrapropylzircoaluminate, tetrabutylzirconate, tetra (triethanolamine) zirconate, tetaraisopropylzirconate, zirconiumacetylacetonate, acetylacetonezirconium butyrate, zirconium lactate, and stearic acid. Zirconium butyrate and the like can be mentioned. These can be used alone or in admixture of two or more.

The blending amount of the coupling agent is preferably 0.01 to 5% by weight with respect to the mass of PAI.

If necessary, a surfactant, a leveling agent, or the like may be added to the PAI solution as long as the effects of the present invention are not impaired.

If necessary, a polymer other than PAI may be added to the PAI solution as long as the effects of the present invention are not impaired.

The PAI solution is applied to the surface of the Al foil and then dried to form a PAI film, whereby the laminate of the present invention can be obtained. As a method of applying the PAI solution to the Al foil, a dip coater, a bar coater, a spin coater, a die coater, a spray coater or the like can be used, and the PAI solution can be applied continuously or in a batch manner. The upper limit of the drying temperature in the drying step is not limited, but is preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. Further, since the PAI film has excellent heat resistance, heat treatment may be performed at a temperature of 200 ° C. or higher, for example, about 250 ° C. after drying.

As the Al foil, a general soft Al foil can be used. The thickness of the Al foil is not limited, but is usually about 9 to 200 μm, preferably 15 to 50 μm.

As the Al foil, a known chemical conversion treatment and degreasing treatment can also be used. Examples of the chemical conversion treatment include chromic acid chromate treatment, phosphoric acid chromate treatment, chromium-based chemical conversion treatment such as coating type chromate treatment, and non-chromic acid-based (coating type) chemical conversion treatment such as zirconium, titanium, and zinc phosphate. Can be done. Examples of the degreasing treatment include an alkaline dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, and an acid activation method.

The thickness of the PAI coating is not limited, but is usually about 0.5 to 50 μm, preferably 1 to 20 μm.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples.

<Example 1>
A copolymerized PAI solution containing dimer acid was prepared in accordance with JP-A-11-21454 and the description of Examples. That is, TMA: 0.97 mol, dimer acid (manufactured by Croda Japan, trade name: PRIPOL1009): 0.03 mol, MDI: 1.0 mol, and NMP were put into a glass reaction vessel under a nitrogen atmosphere. Stirred. The obtained solution was reacted at 120 ° C. for 2 hours, then heated to 180 ° C. and reacted for 6 hours to obtain a PAI solution (A-1) having a solid content concentration of 15% by mass. L-1 was applied on a degreased soft Al foil (manufactured by Toyo Aluminum Co., Ltd., thickness 30 μm) using a doctor blade and dried at 150 ° C. for 30 minutes to have a thickness of 5 μm laminated on the Al foil. A laminated body (L-1) on which the PAI film of No. 1 was formed was obtained. The adhesiveness of L-1 was measured according to JIS K5600-5-6 (Part 5, Section 6, Crosscut Method). That is, six cuts were made in the coating surface at intervals of 1 mm in the vertical and horizontal directions with a cutter knife, and 10 grid patterns with 25 grids were created (the total number of grids was 250). Next, for each of these lattice patterns, a peeling test was performed using cellophane tape (registered trademark), and the peeling points of the grid and the peeling points of the coating film were visually inspected, and the number of peeling points (n points) / It was evaluated by the ratio of the total number of grid stitches (250). The peeling point of L-1 was 0/250, and good adhesiveness was confirmed. Further, no cracks or the like occurred when L-1 was bent. Next, the electrolytic solution resistance of the PAI coating was evaluated. That is, an electrolytic solution (solvent: ethylene carbonate / dimethyl carbonate / diethyl carbonate = 1: 1: 1 (mass ratio), electrolyte: 1 M LiPF ₆ ) to which a small amount of water (100 ppm) was added was dropped onto the surface of the PAI film. After leaving for 24 hours, it was wiped off with isopropyl alcohol. After that, as a result of observing the appearance of the dropped portion, the portion where the electrolytic solution was dropped could not be recognized, and it was found that L-1 had good electrolytic solution resistance.

<Example 2>
A PAI solution (A-2) was obtained in the same manner as in Example 1 except that TMA: 0.95 mol and dimer acid: 0.05 mol were used. Using A-2, a laminated body (L-2) having a PAI film having a thickness of 5 μm laminated on the Al foil was obtained in the same manner as in Example 1. When the adhesiveness of L-2 was evaluated in the same manner as in Example 1, the peeled portion of L-2 was 0/250, and good adhesiveness was confirmed. In addition, no cracks or the like occurred when L-2 was bent.
Further, when the electrolytic solution resistance was evaluated in the same manner as in Example 1, it was found that the portion where the electrolytic solution was dropped could not be recognized, and that L-2 had good electrolytic solution resistance.

<Example 3>
A PAI solution (A-3) was obtained in the same manner as in Example 1 except that TMA: 0.93 mol and dimer acid: 0.07 mol were used. Using A-3, a laminated body (L-3) having a PAI film having a thickness of 5 μm laminated on the Al foil was obtained in the same manner as in Example 1. When the adhesiveness of L-3 was evaluated in the same manner as in Example 1, the peeled portion of L-3 was 0/250, and good adhesiveness was confirmed. In addition, no cracks or the like occurred when L-3 was bent.
Further, when the electrolytic solution resistance was evaluated in the same manner as in Example 1, it was found that the portion where the electrolytic solution was dropped could not be recognized, and that L-3 had good electrolytic solution resistance.

<Example 4>
A laminated body (L-4) having a PAI film formed on the Al foil was obtained in the same manner as in Example 1 except that the thickness of the PAI film laminated on the Al foil was 3 μm. When the adhesiveness of L-4 was evaluated in the same manner as in Example 1, the peeled portion of L-4 was 0/250, and good adhesiveness was confirmed. In addition, no cracks or the like occurred when L-4 was bent. Further, when the electrolytic solution resistance was evaluated in the same manner as in Example 1, it was found that the portion where the electrolytic solution was dropped could not be recognized, and that L-4 had good electrolytic solution resistance.

<Comparative Example 1>
A PAI solution (B-1) was obtained in the same manner as in Example 1 except that 1.0 mol of TMA was used as the carboxylic acid component. Using B-1, a laminated body (R-1) having a 5 μm-thick PAI film laminated on the Al foil was obtained in the same manner as in Example 1. When the adhesiveness of R-1 was evaluated in the same manner as in Example 1, the peeled portion of R-1 was 16/250, which was insufficient in terms of adhesiveness. In addition, cracks occurred when R-1 was bent. Further, when the electrolytic solution resistance was evaluated in the same manner as in Example 1, contours were generated at the points where the electrolytic solution was dropped, and the electrolytic solution resistance of R-1 was insufficient.

<Comparative Example 2>
A laminate (R) in which the PAI film was formed on the Al foil in the same manner as in Example 1 except that B-1 was used as the PAI solution and the thickness of the PAI film laminated on the Al foil was 3 μm. -2) was obtained. When the adhesiveness of R-2 was evaluated in the same manner as in Example 1, the peeled portion of R-2 was 7/250, which was insufficient in terms of adhesiveness. In addition, cracks occurred when R-2 was bent. Further, in the same manner as in Example 1, when the electrolytic solution resistance was evaluated, the place where the electrolytic solution was dropped could not be recognized, and a contour was generated at the place where the electrolytic solution was dropped, and the electrolytic solution resistance of R-2 was generated. Was inadequate.

As shown in Examples and Comparative Examples, the laminate of the present invention is excellent in adhesive reliability, and thus it can be seen that it has good electrolytic solution resistance.

The laminate of the present invention in which the PAI film is laminated on the Al foil has excellent adhesive reliability and good electrolytic solution resistance, and therefore can be suitably used as a LiB exterior member or the like.

Claims (2)

A laminate in which a polyamide-imide (PAI) film is formed on the surface of an aluminum foil, PAI is a copolymerized PAI using dimer acid as a carboxylic acid component, and the copolymerization ratio of dimer acid is total carboxylic acid. A laminate characterized by being 0.5 mol% or more and 7 mol% or less with respect to the components. Use of the laminate according to claim 1 for an exterior member of a lithium ion secondary battery (LiB).