Coating composition and substrate equipped with a coating film

Abstract

[Problem] To provide a composition capable of forming a dry coating on a surface, in the case of coating solutions such as paints, inks, adhesives, and positive and negative electrodes and separators of lithium-ion batteries, which mainly contain polymers. [Solution] A coating composition comprising a filler, a binder, a thickener, and a solvent, wherein the binder is at least one selected from diene rubber and (meth)acrylate polymer, and the viscosity of the coating composition measured at a shear rate of 0.01 / s is 1.0×106 Pa·s or less, and the following thixotropy index (TI) is 1.1×106 or more; [thixotropy index (TI)] = [viscosity of the coating composition measured at a shear rate of 0.01 / s] / [viscosity of the coating composition measured at a shear rate of 10,000 / s].

Description

Technology Field

[0001] The present invention relates to a composition comprising a filler, a binder, and a thickener, and to a composition capable of forming an easy-drying coating on a surface, in the case of paints, inks, adhesives, positive and negative electrodes, separators, etc., of lithium-ion batteries, mainly comprising polymers. Background Technology

[0002] In industrial fields, coating and printing technologies using compositions are widely used from the perspectives of environmental and safety aspects as well as efficiency. In these printing technologies, it is desired to have high coating properties, such as the ability to discharge and apply the minimum necessary amount of composition at high speed and high precision, and furthermore, to have a smooth coated surface.

[0003] However, the physical properties of a composition with excellent coating properties were not identified.

[0004] For example, Patent Document 1 discloses that a battery separator coating solution with excellent dispersibility and ease of coating is obtained by diluting fibrous cellulose with ion-exchanged water to a specific thixotropy index (TI).

[0005] Patent Document 2 discloses a coating solution for a metal ion secondary battery separator that can form a uniform coating film with excellent coating properties by making the viscosity ratio at a predetermined shear rate higher than a certain level. Prior art literature

[0006] International Publication No. 2018 / 070473 Japanese Patent No. 5829557 The problem to be solved

[0007] However, Patent Document 1 does not disclose TI in a state containing a composition other than fibrous cellulose and ion-exchanged water. Furthermore, there is no description or indication regarding high-speed coating properties.

[0008] In Patent Document 2, the coating solution has a very high solid content with a water-soluble component content of 5 mass% or less, and does not suggest anything at all in terms of high-speed coating performance or surface smoothness.

[0009] While many compositions possess good coating properties, the characteristics contributing to coating properties at high speeds or surface smoothness were not clearly identified. means of solving the problem

[0010] Under these circumstances, the inventors, after careful examination, discovered that by using a composition in which the viscosity ratio at high and low shear rates is within a specific range, it is possible to form a coating film with excellent coating properties and excellent surface smoothness, and thus sufficiently use it for the above-mentioned applications, and thus completed the present invention.

[0011] That is, the composition of the present invention is as follows.

[0012] [1] A coating composition comprising a filler, a binder, a thickener, and a solvent,

[0013] The above binder comprises at least one selected from diene rubber and (meth)acrylate polymer, and

[0014] The viscosity of the coating composition measured at a shear rate of 0.01 / s is 1.0×10 6 Pa·s or less,

[0015] The following thixotropy index (TI) is 1.1×10 6 A coating composition characterized by the above;

[0016] [Thixotropy Index (TI)] = [Viscosity of coating composition measured at a shear rate of 0.01 / s] / [Viscosity of coating composition measured at a shear rate of 10,000 / s]

[0017] [2] A coating composition of [1] in which the ratio of the filler to the thickener is 10 to 100 in mass ratio (filler / thickener).

[0018] [3] A coating composition of [1] or [2] in which the above-mentioned thickener is polyN-vinylcarboxylic acid amide.

[0019] [4] The above-mentioned thickener is polyN-vinylacetamide, [1] to [3] coating compositions.

[0020] [5] A coating composition of [1] or [2] in which the above-mentioned thickener is polyvinylpyrrolidone.

[0021] [6] A coating composition of [1] to [5] containing water as a solvent.

[0022] [7] The value of the above thixotropy index (TI) is 1.1×10 8 The coating composition of [1] to [6] below.

[0023] [8] Coating compositions of [1] to [7], wherein the aspect ratio of the above filler is 1 or more and less than 2.

[0024] [9] A substrate having a coating film, comprising a coating film formed from the coating composition of [1] to [8].

[0025]

[10] Separator formed from a coating membrane substrate of [9].

[0026]

[11] A secondary battery using the separator of

[10] .

[0027]

[12] A lithium-ion secondary battery using the separator of

[10] .

[0028]

[13] An electrode material formed by providing a coating film formed from the coating compositions of [1] to [8] on the surface of a substrate. Effects of the invention

[0029] The coating composition of the present invention can obtain a coating film with a smooth surface when the composition is coated at high speed and high precision. If this technology is employed for forming electrodes or separators, such as those in secondary batteries, particularly lithium-ion secondary batteries, the production efficiency of the secondary battery can be improved. Specific details for implementing the invention

[0030] The following describes a mode of implementing the present invention.

[0031] [Coating Composition]

[0032] The coating composition of the present embodiment comprises a filler, a thickener, a binder, and a solvent.

[0033] For this coating composition, the viscosity of the coating composition measured at a shear rate of 0.01 / s is 1.0 × 10⁻⁶ 6 It is less than Pa·s.

[0034] The following thixotropy index (TI) is 1.1×10 6 Ideally, 3.0×10 6 The above is the case, and more preferably 1.0×10 7 That is all. In addition, the thixotropy index (TI) is preferably 1.1 × 10⁻⁶ 8 Below, preferably 5.0×10 7 The following applies. Such a predetermined thixotropy index (TI) can be adjusted by the above composition.

[0035] [Thixotropy Index (TI)]=[Viscosity of coating composition measured at a shear rate of 0.01 / s] / [Viscosity of coating composition measured at a shear rate of 10,000 / s].

[0036] The thixotropy index (TI) of the present invention is the ratio of viscosity at a high shear rate to viscosity at a low shear rate, and by having this ratio within a predetermined range, an extremely smooth coating film can be obtained without streaks or flow marks appearing on the surface even when high-speed and high-precision coating is performed.

[0037] [Filler]

[0038] As a filler, materials containing inorganic substances are used. Specifically, alumina, boehmite, talc, kaolin, calcium carbonate, calcium phosphate, amorphous silica, crystalline glass filler, titanium dioxide, silica-alumina composite oxide particles, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, etc. are preferred as fillers. Among these, alumina and boehmite are more preferred.

[0039] The shape of the filler is not particularly limited and may be spherical, polyhedral, plate-like, flaky, columnar, tubular, or fibrous.

[0040] The aspect ratio of the filler is preferably 1 or more and 15 or less, and more preferably in the range of 1 or more and less than 2. If the aspect ratio of the filler is 1 or more and 15 or less, it is easy to mix with other components in the coating composition, which is desirable.

[0041] 50% particle size D in the cumulative particle size distribution based on the volume of the filler 50 It is preferably in the range of 0.1 to 50 μm, more preferably 0.5 to 10 μm.

[0042] [Thickening agent]

[0043] The thickener includes an organic polymer. The binder described below is not included in the thickener. Preferred thickeners include poly-N-vinylcarboxylic acid amide, poly-N-vinylpyrrolidone, sodium salt of carboxymethylcellulose, polyacrylamide, polyvinyl alcohol, carrageenan, xanthan gum, guar gum, pectin, polysaccharides, cellulose-based polymers such as carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, methylethylhydroxycellulose, methylcellulose, and hydroxypropylcellulose, and ammonium salts and alkali metal salts of these cellulose-based polymers.

[0044] Among these, polyN-vinylcarboxylic acid amide or polyN-vinylpyrrolidone is preferred, more preferably polyN-vinylcarboxylic acid amide, and even more preferably polyN-vinylacetamide. Specific examples of monomers constituting polyN-vinylcarboxylic acid amide include N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, N-vinylbenzamide, N-vinyl-N-methylformamide, N-vinyl-N-ethylformamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, etc. Among these, N-vinylacetamide is particularly preferred.

[0045] These may be homopolymers or copolymers. When copolymerizing, it is possible to copolymerize salts such as itaconic acid, maleic acid, crotonic acid, and (meth)acrylate acid, but is not particularly limited.

[0046] The component derived from N-vinylacetamide in polyN-vinylcarboxylic acid amide is preferably 60 mol% or more.

[0047] The viscosity of the thickener is preferably 30 mPa·s or more and 30,000 mPa·s or less in terms of its viscosity as is (without adjusting the solution concentration). It is desirable that the viscosity be within this range so that the coating process is easy to perform.

[0048] [bookbinder]

[0049] The binder comprises at least one selected from diene rubber and (meth)acrylate polymer, and it is more preferable to comprise only at least one selected from diene rubber and (meth)acrylate polymer. Examples of diene rubber include styrene-butadiene rubber, butyl rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, ethylene-propylene-diene rubber, or modified products thereof. The (meth)acrylate polymer refers to a polymer comprising at least one of acrylate and methacrylate. The (meth)acrylate polymer may be copolymerized and comprises 50 mol% or more of acrylate and methacrylate.

[0050] Other monomers included in the (meth)acrylate polymer are not particularly limited as long as they can copolymerize with (meth)acrylate.

[0051] These may also be added to the coating material in the form of an emulsion latex dispersed in water.

[0052] In addition, polyvinyl alcohol, poly(meth)acrylic acid, higher alcohol ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, etc., can also be used as binders, and in the case of poly(meth)acrylic acid, the salt is not particularly limited, but an ammonium salt that does not contain metal is preferred as the salt, and for example, ammonium polyacrylate can be used.

[0053] Among these, a cross-linked type acrylate emulsion is preferred. The acrylate emulsion may be either a homopolymer or a copolymer. In addition, it may be used as an emulsion or after solidification.

[0054] [menstruum]

[0055] The solvent is not particularly limited as long as it disperses or dissolves each of the above components and does not react, but a volatile solvent is used in consideration of drying properties. Specifically, water or a polar solvent compatible with water is used, and it is preferable that water is included in an amount of 50 mass% or more, and it is more preferable that water alone is used. Ion-exchanged water is particularly preferred. Examples of solvents other than water include alcohols such as methanol, ethanol, and isopropanol.

[0056] [Dispersant]

[0057] The coating composition of the present invention may include a dispersant as needed. The dispersant is not particularly limited as long as it can disperse the filler, but fatty acid esters of dodecylbenzenesulfonic acid, sorbitol, and sorbitan are preferred. The salt is not particularly limited, but an ammonium salt that does not contain metal is preferred.

[0058] [Composition and Preparation Method of Coating Composition]

[0059] The ratio of filler to thickener in the coating composition is preferably 10 to 100, more preferably 20 to 80, and even more preferably 30 to 60 in mass ratio (filler / thickener). With this ratio, coating is easy, drying properties are good, and sufficient strength is obtained in the coating layer, which is desirable.

[0060] The mass of the filler in the coating composition is preferably in the range of 10 to 80 mass%, more preferably 20 to 50 mass%. Based on the solid content in the coating composition, the mass of the filler is preferably in the range of 50 to 99 mass%, more preferably 70 to 98 mass%.

[0061] It is preferable that the solid content of the binder be included in a range of preferably 0.1 to 20 mass%, more preferably 1 to 5 mass%, with respect to the mass of the filler.

[0062] The mass of the binder (solid content) in the coating composition is preferably in the range of 0.1 to 20 mass%, more preferably 1.0 to 5.0 mass%. Based on the solid content in the coating composition, the mass of the binder (solid content) is preferably in the range of 0.2 to 10 mass%, more preferably 0.5 to 5.0 mass%.

[0063] The mass of the thickener in the coating composition is preferably in the range of 0.01 to 20 mass%, more preferably 1.0 to 5.0 mass%. Based on the solid content in the coating composition, the mass of the thickener is preferably in the range of 0.2 to 10 mass%, more preferably 0.5 to 5 mass%.

[0064] Typically, regarding the solvent such as water, the filler is preferably 0.1 to 1000 parts by mass, more preferably 1 to 200 parts by mass, per 100 parts by mass of the solvent. Within this range, good fluidity is obtained for the coating composition, and the viscosity measured at a shear rate of 0.01 / s is 1.0 × 10⁻⁶ 6 A coating composition with a Pa·s or less can be obtained.

[0065] When a dispersant is included, the amount is preferably in the range of 0.01 to 10 mass%, more preferably 0.1 to 5 mass%, in the coating composition. If included in this range, the dispersibility of the filler can be increased.

[0066] Although the method of mixing each component of the coating composition is not particularly limited, in order to achieve a more uniform mixture, it is preferable to dissolve or disperse the binder, thickener, etc., in a solvent and then add and mix the filler. Furthermore, it is more preferable to sequentially add the filler while continuously stirring the solution in which the binder, thickener, etc. are dissolved or dispersed, and then mix and homogenize the mixture. By doing so, it becomes possible to achieve an ideal mixture form.

[0067] [use]

[0068] The coating composition of the present embodiment can be used in various coating liquids such as paints, inks, adhesives, positive and negative electrodes, and separators of lithium-ion batteries, depending on the type of filler incorporated.

[0069] The coating composition can be used as a coating solution as is, but if necessary, the concentration or viscosity can be adjusted appropriately with a solvent or the like to be used as a coating solution.

[0070] For example, a coating film is manufactured by applying the above coating composition to a substrate surface and drying it. Additionally, a coating film containing the coating composition may be provided on a substrate surface (referred to as a substrate provided with a coating film) and used as an electrode material.

[0071] The coating composition of the present invention comprises a filler, a binder, a thickener, and a solvent, and the viscosity of the coating composition measured at a shear rate of 0.01 / s is 1.0 × 10⁻⁶ 6 Pa·s or less,

[0072] The following thixotropy index (TI) is 1.1×10 6 From the above, even if the coating composition is coated at high speed and high precision, a coating film with a smooth surface on the coated surface can be obtained.

[0073] The method of coating the substrate of the coating composition is not particularly limited, but in addition to spray coating, roll coating, bar coating, gravure coating, die coating, knife coating, inkjet coating, brush coating, dipping coating, etc., it is also possible to coat continuously using a roll-to-roll pattern coating device.

[0074] In addition, the coating composition may include known materials added to paint in addition to the above, and may include, for example, surface modifiers, defoaming agents, leveling agents, pigments, dyes, etc.

[0075] As for the substrate, films, nonwoven fabrics, porous bodies, plate-like bodies, etc., can be used without particular restriction.

[0076] Materials constituting the substrate may include ethylene alone or copolymers with other α-olefins, homopolypropylene, copolymers of propylene and other olefins, organic resin materials such as polyethylene terephthalate, polyethylene naphthalate, polyamide ether ketone, polyimide, polyamide, polyphenylene sulfone, polyphenylene ether, polyethylene, polyether sulfone, polyether ether ketone, polybenzimidazole, polyetherimide, polyamideimide, poly(p-phenylene-2,6-benzobisoxazole), fluoropolymer, and epoxy resin, metal materials such as aluminum, copper, silver, and iron, and inorganic materials such as glass (silicon oxide), alumina, magnesia, aluminum nitride, aluminum carbide, silicon nitride, and barium titanate. The substrate may be used as a single type or in combination of two or more types. Among these, polyolefin is preferred as the substrate, more preferably at least one selected from polyethylene and polypropylene, and most preferably a three-layer laminate laminated in the order of polypropylene / polyethylene / polypropylene. If a porous substrate containing such a material is used, it can be used as a separator for a secondary battery, etc.

[0077] In the case of a polyolefin film, the porous substrate is not particularly limited to being manufactured by a wet method or a dry method. Furthermore, in the case of a porous substrate comprising a three-layer laminate, it is preferable that all three layers be manufactured by a dry method. A structure having such a composition is free from curling and has good heat resistance, mechanical strength, etc.

[0078] In addition, the dry method is a dry process that does not use a solvent when manufacturing a film, and examples include melt molding or injection molding of molten resin using a T-die. In addition, the outer layer and inner layer may be made using either the dry method or the wet method, and the wet method is a method of forming pores by forming a film using a resin to which additives have been added and mixed, and then extracting the additives with a solvent.

[0079] The total thickness of the substrate is appropriately selected in terms of mechanical strength, performance, and miniaturization according to the purpose, and it is preferable that it be 7.0 μm or more, and the upper limit is preferably 50 μm or less. With a thickness within this range, the strength can be increased.

[0080] In addition, for porous substrates, it is preferable that the air permeability measured in accordance with JIS P 8117:2009 be 80 seconds / 100ml or higher, and the upper limit be 700 seconds / 100ml or lower. If the air permeability is within this range, short circuits are difficult to occur, and the ion mobility is also high.

[0081] It is preferable that the porosity of the porous substrate be 30% or more, and the upper limit be 70% or less. With a porosity within this range, the mechanical strength is high, there is no short circuit, and the ion mobility can be high.

[0082] The maximum pore diameter of the porous substrate is preferably 0.05 μm or more, and the upper limit is preferably 2 μm or less. If it is within this range, when used as a separator, the ion mobility is high and the resistance is low.

[0083] The thickness of the coating film is not particularly limited and can be a coating film with a thickness of 0.5 to 20 μm, but is not particularly limited.

[0084] Drying methods for the coating film are not particularly limited and include spin drying, vacuum drying, hot air drying, and infrared drying. The drying time is also not particularly limited.

[0085] When configuring a separator, it can be configured by a method such as applying the above coating composition to the surface of the substrate.

[0086] When forming an electrode, the battery electrode can be formed by mixing the coating composition with a positive electrode active material or a negative electrode active material and applying it to the surface of the substrate or the current collector, or by coating a mixture of the positive electrode active material or the negative electrode active material or both thereof onto an electrode foil, or by forming the coating composition into a thin film and inserting it into the surface of the positive electrode or the negative electrode or both current collectors.

[0087] The components constituting a lithium-ion secondary battery can be broadly divided into a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode and the negative electrode each contain an active material that performs an oxidation / reduction reaction to transmit and receive electrons. The positive electrode and the negative electrode can be used in the form of an electrode group with a stacked structure formed by interposing a battery separator, or further in the form of an electrode group with a wound structure formed by winding these electrodes.

[0088] As for the positive electrode, there are no particular restrictions as long as it is a positive electrode conventionally known to be used in lithium-ion secondary batteries. The positive electrode is Li + It contains an active material capable of absorbing and releasing ions.

[0089] As for the negative electrode, there are no particular restrictions as long as it is a negative electrode conventionally known to be used in lithium-ion secondary batteries. The negative electrode is Li + It contains an active material capable of absorbing and releasing ions.

[0090] The positive and negative electrodes can be used in the form of an electrode group with a stacked structure formed by stacking with a separator interposed, or further in the form of an electrode group with a wound structure formed by winding this. As the electrolyte, a solution in which a lithium salt is dissolved in an organic solvent is used. As the lithium salt, Li dissociates in the solvent. + There are no particular restrictions as long as it forms ions and does not cause side reactions such as decomposition within the voltage range used as a battery. As for the organic solvent, there are no particular restrictions as long as it dissolves the lithium salt and does not cause side reactions such as decomposition within the voltage range used as a battery.

[0091] Each component produced using the coating composition of the present embodiment is appropriately used in each component of the battery.

[0092] Lithium-ion batteries are used for various conventional applications in addition to powering various devices such as mobile phones, laptop personal computers, electric vehicles, hybrid vehicles, electric bikes, electric bicycles, power tools, and electric shavers.

[0093] Examples

[0094] The present invention will be explained below by way of examples, but the present invention is not limited to these examples at all.

[0095] [Examples 1 to 12, Comparative Examples 1 to 3]

[0096] The specified amounts listed in Table 1 were weighed in the order of ion-exchanged water, surfactant, dispersant, binder, thickener, and inorganic filler into a 200ml resin container and fed into a rotating type kneader (Sinky ARE-250). The mixture was sealed with a stopper and mixed under conditions of 60 seconds of mixing and 60 seconds of degassing to obtain a uniform coating composition.

[0097] A polypropylene sheet (thickness 1 mm) was fixed on the coating plate of a coating machine, and 3.5 g of the obtained coating composition was coated over a width of 15 cm and a length of 30 cm using an automatic coating machine (Tester Sangyo Co., Ltd. Pi-1210) at a speed of 200 mm / second with a bar coater (Yoshimitsu Seki Co., Ltd., width: 50 mm × thickness: 5 μm).

[0098] After that, the polypropylene sheet with the formed coating was dried in a hot air dryer at a temperature of 40°C for 1 hour to obtain a coated sheet.

[0099] Each component used in the composition is as follows.

[0100] · Filler

[0101] Alumina: AL160-SG-3 (Manufactured by Showa Denko Co., Ltd.) D 50 : 0.52㎛, aspect ratio 1.4

[0102] Individual Bemite: Serashur (Made by Kawai Sekkai High School Co., Ltd.) Aspect B: 20 ​​to 40

[0103] Flake alumina: Cerashur α (manufactured by Kawai Sekkai High School Co., Ltd.) Aspect B: 20 ​​to 40

[0104] ·bookbinder

[0105] Acrylate Emulsion: Polysol (Registered Trademark) LB-350 (Manufactured by Showa Denko Co., Ltd.)

[0106] SBR (Styrene Butadiene Rubber Aqueous Dispersion): BM400B (Manufactured by Nippon Zeon Co., Ltd.)

[0107] Ammonium polyacrylate: Aaron (registered trademark) A-30SL (manufactured by Doa Gose Co., Ltd.)

[0108] · Thickener

[0109] Poly-N-vinylacetamide PNVA (registered trademark)-1: GE191-043 (manufactured by Showa Denko Co., Ltd.), unadjusted viscosity 5000 mPa·s, solids content 4 mass%

[0110] Poly-N-vinylacetamide PNVA (registered trademark)-2: GE191-104 (manufactured by Showa Denko Co., Ltd.), unadjusted viscosity 18,000 mPa·s, solids content 10 mass%

[0111] Poly-N-vinylacetamide PNVA (registered trademark)-3: GE191-107 (manufactured by Showa Denko Co., Ltd.), unadjusted viscosity 50 mPa·s, solids content 10 mass%

[0112] Carboxymethylcellulose CMC-Na: MAC350HC (manufactured by Nippon Seishi Co., Ltd., 2 mass% viscosity 7800 mPa·s)

[0113] Polyvinylpyrrolidone: PVP K-90 (Manufactured by Tokyo Kasei High School Co., Ltd.)

[0114] · Dispersant

[0115] Sodium dodecylbenzenesulfonate aqueous dispersion: Neopelex G-65 (manufactured by Gao Co., Ltd.)

[0116]

[0117] The obtained composition and coated sheet were evaluated as follows.

[0118] <Rotation Viscosity>

[0119] Using a Brookfield DV2T type viscometer spindle SC4-28 water jacket small sample adapter, 20g of the coating composition was placed in the sample holder, and the rotational viscosity was measured at rotational speeds of 0.3rpm and 100rpm.

[0120] Solution Viscosity

[0121] The coating composition was evaluated at 23°C and 50 rpm using a Type B viscometer (Brookfield DV2T type viscometer spindle SC4-28 water jacket small sample adapter).

[0122] In addition, the blank locations in Examples 8 to 12 are not subject to data measurement.

[0123] <Shear Viscosity, TI>

[0124] TI (Thixotropy Index) is calculated using the following formula.

[0125] TI = Viscosity of coating composition at a shear rate of 0.01 / s (Pa·s) ÷ Viscosity of coating composition at a shear rate of 10,000 / s (Pa·s)

[0126] Shear viscosity was measured using an AntonParr rotational viscometer. Specifically, the viscosity of the coating composition at 23°C was measured at a shear rate of 0.1 sec -1 from 10000sec -1 Up to, measuring while increasing speed over 400 seconds, and continuously for 10,000 seconds -1 from 0.1sec -1Measurements were taken while decreasing the speed over a period of 400 seconds. The measured values ​​obtained while decreasing the shear rate were defined as the viscosity at each shear rate.

[0127] Viscosity of Carboxymethylcellulose

[0128] Carboxymethylcellulose was adjusted with water to a solid content of 2 mass% and evaluated at 23°C and 50 rpm using a Brookfield DVE type viscometer spindle H04.

[0129] Coating thickness

[0130] Using a Techlock PF-11J static pressure thickness gauge, three points were measured and averaged: the center of the coated and dried film and two points located 10 cm above and below the center.

[0131] <Potted Surface Appearance>

[0132] The surface appearance of the coated sheet was evaluated according to the following criteria.

[0133] ○: No voids were found on the surface of the coating.

[0134] △: Fewer than 10 voids were identified on the surface of the coating.

[0135] ×: More than 10 voids were identified on the coating surface.

[0136] Surface roughness

[0137] Using a Surtronic Duo surface roughness meter (manufactured by TAYLOR HOBSON), the arithmetic mean roughness (Ra) of a coated sheet (15 cm × 30 cm) was measured at three points: the center and two points 10 cm above and below the center, and the average was calculated.

[0138] <Exfoliation Evaluation>

[0139] A cellophane tape peel test was performed on the coated surface of the coated sheet using a 15 mm wide cellophane tape manufactured by Nichiban, and the adhesion between the coated material and the polypropylene sheet was evaluated in the following three stages.

[0140] ○: The coated part did not peel off.

[0141] △: The coating has peeled off slightly, but it is usable.

[0142] ×: The coating has peeled off and is practically unacceptable.

[0143] Heat Resistance Evaluation

[0144] From the coating sheet, a portion of the coating with a constant thickness (6 to 7 μm) was peeled off, a rectangular sample (5 cm × 4 cm) was taken, and the lengths of the four sides were measured. Then, the test specimens were placed on metal bats at a distance from each other without interference.

[0145] The metal tray was placed in an air oven at an internal temperature of 150°C for 15 minutes, removed, and the dimensions of the four sides were measured. The test specimen, after measurement was completed, was placed in an air oven adjusted to 200°C, left for 15 minutes, removed, and the dimensions of the four sides were measured.

[0146] It was evaluated based on the following items.

[0147] ○: For all sides at 150℃ and 200℃, the shrinkage rate is 20% or less.

[0148] △: In the 150℃ and 200℃ tests, in any of the variables, the shrinkage rate is greater than 20% and less than or equal to 30%, and the shrinkage rate of all variables is less than or equal to 30%.

[0149] ×: In any of the variables tested at 150℃ and 200℃, there are cases where the shrinkage rate exceeds 30%.

[0150] Aspect B

[0151] In accordance with JIS R1670-2006, the long diameter and short side of 100 particles were each measured and averaged using microscopic images, and the result was calculated as average long diameter ÷ average short side.

[0152] <D 50 >

[0153] A laser diffraction / scattering particle diameter distribution measuring device (Horiba Seisakusho Inc., Partica mini LA-350), the median diameter based on volume distribution (hereinafter D) 50 There are also cases where it is said that), the volume average diameter based on the volume distribution standard was measured.

[0154]

[0155] From Table 2, in the examples where TI is within a specific range, it was possible to form a coating film that has no disturbance on the coating surface, high surface smoothness, and excellent peelability and heat resistance.

Claims

Claim 1 A coating composition comprising a filler, a binder, a thickener, and a solvent, wherein the binder comprises at least one selected from diene rubber and (meth)acrylate polymer and an ammonium poly(meth)acrylate salt, and the viscosity of the coating composition measured at a shear rate of 0.01 / s is 1.0 × 10⁻⁶ 6 Pa·s or less, and the following thixotropy index (TI) is 1.1×10 6 A coating composition characterized by the above: [Thixotropy Index (TI)] = [Viscosity of the coating composition measured at a shear rate of 0.01 / s] / [Viscosity of the coating composition measured at a shear rate of 10,000 / s]. Claim 2 A coating composition according to claim 1, wherein the ratio of the filler to the thickener is 10 to 100 in mass ratio (filler / thickener). Claim 3 A coating composition according to claim 1 or 2, wherein the thickener is polyN-vinylcarboxylic acid amide. Claim 4 A coating composition according to claim 1 or 2, wherein the thickener is polyN-vinylacetamide. Claim 5 A coating composition according to claim 1 or 2, wherein the thickener is polyvinylpyrrolidone. Claim 6 A coating composition comprising water as a solvent in claim 1 or 2. Claim 7 In claim 1 or 2, the value of the thixotropy index (TI) is 1.1 × 10 8 A coating composition of the following person. Claim 8 A coating composition according to claim 1 or 2, wherein the aspect ratio of the filler is 1 or more and less than 2. Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 delete

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