Coating composition

Abstract

To provide a coating composition having excellent dispersibility in alcohol and excellent stability under standing conditions.SOLUTION: A coating composition comprises a polymer, an alcohol, and an inorganic filler. The polymer comprises structural units derived from isopropenyltoluene and structural units derived from isopropenylphenol.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coating composition. [Background technology]

[0002] Conventionally, inorganic fillers are blended into coating compositions from the viewpoint of imparting various physical properties (for example, heat resistance, adhesion) to a coating layer formed from the coating composition.

[0003] On the other hand, if the inorganic filler aggregates in the coating composition, various physical properties may not be sufficiently imparted to the coating layer, and therefore, the inorganic filler is required to have good dispersibility in the coating composition.

[0004] Specifically, an aqueous coating composition containing particles and a film-forming polymer composition containing a polymer and water has been proposed (see, for example, Patent Document 1). In such an aqueous coating composition, the surface of the particles is modified in advance with a chemical agent, thereby improving the dispersibility of the particles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2017-511395 Summary of the Invention [Problem to be solved by the invention]

[0006] On the other hand, in Patent Document 1, the surface of the particles is modified in advance with a chemical, which makes the process complicated.

[0007] In addition, alcohol is selected as the dispersion medium of the coating composition from the viewpoint of volatility, that is, when the coating composition contains alcohol, dispersibility of the inorganic filler is required.

[0008] From the viewpoint of storage stability, it is also required that aggregation of the inorganic filler be suppressed even when the inorganic filler is allowed to stand for a certain period of time after being dispersed (i.e., static stability is required).

[0009] The present invention provides a coating composition having excellent dispersibility in alcohol and static stability. [Means for solving the problem]

[0010] The present invention [1] is a coating composition comprising a polymer, an alcohol, and an inorganic filler, the polymer comprising a structural unit derived from isopropenyl toluene and a structural unit derived from isopropenyl phenol.

[0011] The present invention [2] includes the coating composition according to the above [1], in which the content of the polymer is 80 parts by mass to 200 parts by mass relative to 100 parts by mass of the inorganic filler, and the content of the alcohol is 300 parts by mass to 400 parts by mass relative to 100 parts by mass of the inorganic filler.

[0012] The present invention [3] includes the coating composition according to the above [1], in which the content of the polymer is 120 parts by mass to 180 parts by mass relative to 100 parts by mass of the inorganic filler, and the content of the alcohol is 300 parts by mass to 350 parts by mass relative to 100 parts by mass of the inorganic filler.

[0013] The present invention [4] includes the coating composition according to any one of the above [1] to [3], wherein the polymer has a weight average molecular weight of 400 to 1,000.

[0014] The present invention [5] includes the coating composition according to any one of the above [1] to [4], in which the structural unit derived from isopropenylphenol is 2 mol % to 30 mol % relative to the polymer.

[0015] The present invention [6] includes the coating composition according to any one of the above [1] to [5], wherein the alcohol is isopropyl alcohol or methanol.

[0016] The present invention [7] includes the coating composition according to any one of the above [1] to [6], wherein the inorganic filler is inorganic particles, and the average primary particle diameter of the inorganic particles is 0.1 μm to 100 μm.

[0017] The present invention [8] includes the coating composition according to any one of the above [1] to [7], wherein the inorganic filler is silica or talc. Effect of the Invention

[0018] The coating composition of the present invention contains a polymer including a structural unit derived from isopropenyl toluene and a structural unit derived from isopropenyl phenol, and therefore has excellent dispersibility in alcohol and static stability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The coating composition includes a polymer, an alcohol, and an inorganic filler.

[0020] <Polymer> The polymer is a dispersing agent for dispersing the inorganic filler in the coating composition.

[0021] The polymer contains structural units derived from isopropenyl toluene and structural units derived from isopropenyl phenol.

[0022] Such a polymer is a polymer of the polymerization components and is produced by polymerizing the polymerization components.

[0023] The polymerization components essentially comprise isopropenyl toluene and isopropenyl phenol.

[0024] The polymerization components may also contain other components (components other than isopropenyl toluene and isopropenyl phenol) as optional components, that is, the polymer may also contain structural units derived from other components.

[0025] Other components include, for example, alpha-methylstyrene, indene, vinyl toluene, and unsaturated aliphatic hydrocarbons.

[0026] The unsaturated aliphatic hydrocarbons are components copolymerizable with isopropenyl toluene, isopropenyl phenol, α-methyl styrene, indene, and vinyl toluene, and examples thereof include C4 fractions and C5 fractions.

[0027] The C4 fraction is obtained by refining and / or cracking petroleum. The C4 fraction is a fraction having a boiling point range of −15° C. or more and 45° C. or less under normal pressure, and includes, for example, unsaturated aliphatic hydrocarbons having 4 carbon atoms and no conjugated double bonds, and unsaturated aliphatic hydrocarbons having 4 carbon atoms and containing conjugated double bonds.

[0028] Examples of unsaturated aliphatic hydrocarbons having 4 carbon atoms and containing no conjugated double bonds include 1-butene, isobutene, and 2-butene.

[0029] An example of an unsaturated aliphatic hydrocarbon having 4 carbon atoms and containing a conjugated double bond is 1,3-butadiene.

[0030] The C5 fraction is obtained by refining and / or cracking petroleum, and generally has a boiling point range of -15°C to 45°C under normal pressure, and includes, for example, unsaturated aliphatic hydrocarbons having 5 carbon atoms and no conjugated double bonds, and unsaturated aliphatic hydrocarbons having 5 carbon atoms and containing conjugated double bonds.

[0031] Examples of unsaturated aliphatic hydrocarbons having 5 carbon atoms and containing no conjugated double bonds include 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, and 2-pentene.

[0032] Examples of unsaturated aliphatic hydrocarbons having 5 carbon atoms and containing a conjugated double bond include isoprene, 1,3-pentadiene, and cyclopentadiene.

[0033] The other components may be used alone or in combination of two or more kinds.

[0034] The polymerization components preferably do not contain other components and include isopropenyl toluene and isopropenyl phenol. That is, the polymerization components preferably consist of isopropenyl toluene and isopropenyl phenol. In other words, the polymer is preferably a copolymer of isopropenyl toluene and isopropenyl phenol consisting of structural units derived from isopropenyl toluene and structural units derived from isopropenyl phenol.

[0035] In addition, all or a part of the monomers constituting the polymerization components may be derived from fossil fuels or biomass.

[0036] Fossil fuels include petroleum, coal, natural gas, shale gas, or combinations thereof.Biomass is any renewable natural raw material and its residue, such as plant- or animal-derived, including fungi, yeast, algae, and bacteria.Preferably, isopropenyl toluene and isopropenyl phenol are derived from biomass.

[0037] The polymer is obtained by polymerizing the polymerization components in the presence of a Friedel-Crafts catalyst.

[0038] Friedel-Crafts catalysts include, for example, phenol complexes (eg, boron trifluoride phenolate complexes).

[0039] The mixing ratio of the Friedel-Crafts catalyst is, for example, 0.01 part by mass to 1 part by mass with respect to 100 parts by mass of the polymerization components.

[0040] As for the polymerization conditions, the polymerization temperature is, for example, −50° C. to 50° C. The polymerization time is, for example, 10 minutes to 10 hours.

[0041] The reaction is carried out in the presence of a solvent or without a solvent, and is preferably carried out in the presence of a solvent.

[0042] Examples of the solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, and alkyl esters. Examples of the solvent include aromatic hydrocarbons. Examples of the aromatic hydrocarbons include toluene and xylene. Examples of the aromatic hydrocarbons include toluene.

[0043] The solvents can be used alone or in combination of two or more kinds.

[0044] This gives a polymer (polymer solution).

[0045] The solids concentration of the polymer solution is, for example, 5% by mass to 70% by mass, or preferably 10% by mass to 60% by mass.

[0046] In such a polymer, from the viewpoint of coatability onto a substrate (e.g., a polyethylene terephthalate (PET) film), the content of the constitutional units derived from isopropenyl toluene is, for example, 70 mol % to 98 mol %, preferably 75 mol % to 95 mol %, more preferably 78 mol % to 92 mol %, even more preferably 80 mol % to 90 mol %, and particularly preferably 82 mol % to 88 mol %.

[0047] In such a polymer, the constituent units derived from isopropenylphenol are, from the viewpoint of coatability onto a substrate (e.g., a PET film), for example, 2 mol% to 30 mol%, preferably 5 mol% to 25 mol%, more preferably 8 mol% to 22 mol%, even more preferably 10 mol% to 20 mol%, and particularly preferably 12 mol% to 18 mol%.

[0048] In such a polymer, the content of structural units derived from other components is 10 mol % or less, preferably 5 mol % or less, more preferably 1 mol % or less, and even more preferably 0 mol %.

[0049] The ratio of the above structural units can be determined by IR spectrum, 13 It can be measured by C-NMR spectroscopy.

[0050] The softening point of the polymer is, from the viewpoint of improving the solubility of the polymer in alcohol and the adhesion to a substrate (e.g., a PET film), for example, 65°C to 110°C, preferably 70°C to 105°C, more preferably 75°C to 100°C, even more preferably 80°C to 95°C, and particularly preferably 85°C to 95°C.

[0051] The softening point can be measured by the ring and ball method (in accordance with JIS K2207).

[0052] The number average molecular weight (Mn) of the polymer is, for example, 200 to 2000, preferably 400 to 1000, more preferably 500 to 700, and still more preferably 520 to 550, in terms of standard polystyrene measured by gel permeation chromatography (GPC).

[0053] When the number average molecular weight (Mn) is within the above range, it is possible to improve dispersibility in alcohol, solubility in alcohol, and static stability.

[0054] The weight average molecular weight (Mw) of the polymer is, in terms of standard polystyrene measured by gel permeation chromatography (GPC), for example, 350 to 1000, preferably 400 to 1000, more preferably 400 to 900, even more preferably 450 to 800, particularly preferably 500 to 700, and most preferably 550 to 650.

[0055] When the weight average molecular weight (Mw) is within the above range, the dispersibility in alcohol, the solubility in alcohol, and the static stability can be improved.

[0056] In the polymer, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is, for example, 1.05 to 1.50, preferably 1.10 to 1.30, more preferably 1.10 to 1.20, still more preferably 1.10 to 1.18, and particularly preferably 1.10 to 1.17.

[0057] When the ratio is within the above range, the dispersibility in alcohol, the solubility in alcohol, and the static stability can be improved.

[0058] The polymers can be used alone or in combination of two or more kinds.

[0059] The content of the polymer is, for example, 10 parts by mass to 40 parts by mass, preferably 15 parts by mass to 35 parts by mass, more preferably 20 parts by mass to 33 parts by mass, and even more preferably 25 parts by mass to 30 parts by mass, relative to 100 parts by mass of the total amount of the polymer, the alcohol, and the inorganic filler.

[0060] The content of the polymer is, for example, 80 parts by mass to 200 parts by mass, preferably 100 parts by mass to 190 parts by mass, more preferably 120 parts by mass to 180 parts by mass, and even more preferably 140 parts by mass to 170 parts by mass, relative to 100 parts by mass of the inorganic filler.

[0061] In detail, the content ratio of the polymer is, relative to 100 parts by mass of the inorganic filler, for example, 80 parts by mass or more, preferably 100 parts by mass or more, from the viewpoint of improving the static stability and adhesion to the substrate (e.g., a PET film); from the viewpoint of further improving the static stability and adhesion to the substrate (e.g., a PET film), more preferably 120 parts by mass or more, even more preferably 140 parts by mass or more; and from the viewpoint of the handleability and uniformity of the coating film obtained using the coating composition, for example, 200 parts by mass or less, preferably 190 parts by mass or less; and from the viewpoint of the handleability and uniformity of the coating film, more preferably 180 parts by mass or less, even more preferably 170 parts by mass or less.

[0062] <Alcohol> The alcohol is a dispersion medium for the inorganic filler in the coating composition. In addition, the alcohol is excellent in safety and volatility, and therefore, when the coating composition is applied to a coating target, it has excellent drying properties. Therefore, the coating composition has excellent workability.

[0063] Alcohols include, for example, monohydric alcohols and dihydric alcohols.

[0064] Preferred examples of the monohydric alcohol include methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutanol, s-butanol, t-butanol, pentanol, hexanol, heptanol, octanol, and phenol.

[0065] Examples of dihydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and dipropylene glycol.

[0066] As the alcohol, preferably, a monohydric alcohol is used. From the viewpoint of dispersibility of the inorganic filler, more preferably, methanol and isopropyl alcohol are used. That is, the alcohol is more preferably methanol or isopropyl alcohol.

[0067] The alcohols can be used alone or in combination of two or more kinds.

[0068] The content of the alcohol is, for example, 30 to 80 parts by mass, preferably 40 to 70 parts by mass, and more preferably 50 to 60 parts by mass, relative to 100 parts by mass of the total amount of the polymer, the alcohol, and the inorganic filler.

[0069] The content of the alcohol relative to 100 parts by mass of the inorganic filler is, for example, 200 parts by mass to 700 parts by mass, preferably 250 parts by mass to 500 parts by mass, more preferably 300 parts by mass to 400 parts by mass, and even more preferably 300 parts by mass to 350 parts by mass.

[0070] In detail, the content of alcohol is, relative to 100 parts by mass of the inorganic filler, 200 parts by mass or more, preferably 250 parts by mass or more, from the viewpoint of improving dispersibility in alcohol; more preferably 300 parts by mass or more, from the viewpoint of further improving dispersibility in alcohol; and, for example, 700 parts by mass or less, preferably 500 parts by mass or less, from the viewpoint of improving coatability and adhesion to a substrate (e.g., a PET film), more preferably 400 parts by mass or less, and even more preferably 350 parts by mass or less, from the viewpoint of further improving coatability and adhesion to a substrate (e.g., a PET film).

[0071] <Inorganic filler> The inorganic filler preferably includes inorganic particles. Examples of the inorganic particles include oxides, nitrides, carbides, sulfates, hydroxides, and potassium titanate. Examples of the oxides include alumina, silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide. Examples of the nitrides include silicon nitride, titanium nitride, and boron nitride. Examples of the carbides include silicon carbide and calcium carbonate. Examples of the sulfates include magnesium sulfate and aluminum sulfate. Examples of the hydroxides include aluminum hydroxide and aluminum oxide hydroxide. Examples of the silicates include talc, kaolinite, dickite, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, silica sand, and glass.

[0072] As the inorganic filler, preferably, oxides and silicates are used. As the inorganic filler, more preferably, silica and talc are used from the viewpoint of dispersibility. That is, the inorganic filler is more preferably silica or talc.

[0073] When the inorganic filler is inorganic particles, the average primary particle diameter of the inorganic filler (inorganic particles) is, from the viewpoints of static stability and handleability, for example, 0.1 μm to 100 μm, preferably 0.5 μm to 80 μm, more preferably 1.0 μm to 60 μm, even more preferably 3.0 μm to 40 μm, and particularly preferably 5.0 μm to 30 μm.

[0074] The average primary particle size of the inorganic filler (inorganic particles) can be determined by creating a particle size distribution curve using a laser diffraction / scattering type particle size distribution measurement device and calculating the 50% by mass equivalent particle size.

[0075] The inorganic fillers can be used alone or in combination of two or more kinds.

[0076] The content of the inorganic filler is, for example, 5 to 30 parts by mass, preferably 10 to 20 parts by mass, and more preferably 12 to 17 parts by mass, relative to 100 parts by mass of the total amount of the polymer, alcohol, and inorganic filler.

[0077] <Additives> The coating composition may contain additives in an appropriate ratio as necessary, such as antioxidants, ultraviolet absorbers, antistatic agents, silane coupling agents, coatability improvers, leveling agents, defoamers, plasticizers, surfactants, pigments, antifungals, processing aids, and antiaging agents.

[0078] The additives can be used alone or in combination of two or more kinds.

[0079] <Preparation of Coating Composition> The coating composition can be obtained by blending a polymer (a solution of the polymer), an alcohol, an inorganic filler, and additives that are blended as required.

[0080] When the coating composition is diluted, the solid content concentration is, for example, 5% by mass to 70% by mass, or preferably 10% by mass to 60% by mass.

[0081] In the coating composition, the inorganic filler is dispersed in the alcohol, which provides excellent adhesion to the substrate (e.g., PET film).

[0082] <Action and effect> The coating composition contains a polymer including a structural unit derived from isopropenyl toluene and a structural unit derived from isopropenyl phenol, and therefore has excellent dispersibility in alcohol and static stability.

[0083] In particular, alcohol is safe and highly volatile, and therefore has excellent drying properties when the coating composition is applied to an object to be coated, thereby improving workability.

[0084] On the other hand, when the coating composition contains alcohol, the dispersibility of the inorganic filler in the alcohol may decrease.

[0085] This coating composition contains a polymer containing a structural unit derived from isopropenyl toluene and a structural unit derived from isopropenyl phenol. By containing a structural unit derived from isopropenyl toluene, aggregation between inorganic fillers can be suppressed. In addition, by containing a structural unit derived from isopropenyl phenol, affinity with alcohol can be improved. As a result, such a polymer has excellent solubility in alcohol and can improve the dispersibility of inorganic fillers in alcohol. EXAMPLES

[0086] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are based on mass unless otherwise specified. In addition, the specific numerical values ​​of the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit value (numerical value defined as "less than or equal to" or "less than") or lower limit value (numerical value defined as "more than or equal to" or "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above "Form for carrying out the invention".

[0087] <Ingredient details> Details of the abbreviations used in each Example and Comparative Example are given below. IPT: Isopropenyl toluene IPP: Isopropenyl phenol Silica: Product name "Nipsil VN3", average primary particle size 18 μm, manufactured by Tosoh Silica Corporation Talc: Product name "JM-209", average primary particle size 3.9 μm, manufactured by Asada Flour Milling Co., Ltd.

[0088] <Production of Polymer> Production Example 1 (Copolymer of IPT and IPP) A mixture of isopropenyltoluene, isopropenylphenol, and dehydrated and purified toluene (polymerization components / toluene = 1 / 1 (volume ratio)) and boron trifluoride phenolate complex (1.7 times phenol equivalent) diluted 10 times with dehydrated and purified toluene were continuously fed to the first stage of an autoclave with a working volume of 1270 ml and equipped with a stirring blade, and a polymerization reaction was carried out at 20°C to obtain a reaction mixture. The mass ratio of isopropenyltoluene to isopropenylphenol was 80 / 20. The amount of diluted catalyst fed was 60 milliliters / hour.

[0089] The reaction mixture was then transferred to the second autoclave, and the polymerization reaction was continued at 20°C. When the total residence time in the first and second autoclaves reached 2 hours, the reaction mixture was continuously discharged from the autoclave, and when the residence time reached three times, 1 liter of the reaction mixture was collected to terminate the polymerization reaction. After the polymerization was completed, a 1N NaOH aqueous solution was added to the collected reaction mixture to deash the catalyst residue. Furthermore, the reaction mixture was washed five times with a large amount of water, and the solvent and unreacted polymerization components were distilled off under reduced pressure using an evaporator. This produced a polymer.

[0090] Production Example 2 (IPT and IPP copolymer) A polymer was produced based on the same procedure as in Production Example 1, except that the mass ratio of isopropenyl toluene to isopropenyl phenol was 90 / 10.

[0091] Production Example 3 (IPT homopolymer) A polymer was produced according to the same procedure as in Production Example 1. However, the polymerization component was isopropenyl toluene alone. The polymerization temperature was 25° C., and the amount of the diluted catalyst fed was 30 mL / hour.

[0092] Production Example 4 (IPT homopolymer) A polymer was produced according to the same procedure as in Production Example 3, except that the amount of the diluted catalyst fed was 90 mL / hour.

[0093] <Preparation of Coating Composition> Examples 1 to 7 and Comparative Examples 1 to 12 The polymer, the alcohol, and the inorganic filler were mixed according to the description in Table 2. Then, the mixture was stirred for 10 minutes using a stirrer. Thus, a coating composition was prepared.

[0094] <Evaluation> [Constituent units of each component] The structural units of each component in the polymer of each production example were analyzed using a Fourier transform infrared spectrophotometer (FT-IR) manufactured by JASCO Corporation, with the aromatic C=C stretching vibration of about 1500 cm originating from isopropenyltoluene. -1 (R1) and the OH stretching vibration of about 3200 cm originating from isopropenylphenol -1 The absorbance ratio (R2 / R1) was calculated. The results are shown in Table 1.

[0095] [Softening point] The polymers of each production example and KE100 were measured by the ring and ball method in accordance with JIS K2207. The results are shown in Table 1.

[0096] [Number average molecular weight (Mn), weight average molecular weight (Mw) and Mw / Mn] For the polymers of each production example, the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of standard polystyrene were measured by gel permeation chromatography (GPC) under the following measurement conditions, and Mw / Mn was calculated. The results are shown in Table 1. {Measurement conditions} Equipment: GPC HLC-8320 (Tosoh Corporation) Solvent: Tetrahydrofuran Columns: TSKgel G7000 x 1, TSKgel G4000 x 2, TSKgel G2000 x 1 (all manufactured by Tosoh Corporation) Flow rate: 1.0ml / min Sample: 20mg / mL tetrahydrofuran solution Column temperature: 40℃ Detector: Differential refractive index detector Injection volume: 50μl

[0097] [Dispersibility] The coating compositions of each Example and Comparative Example were transferred to a test tube, and the solubility of the polymer and the dispersibility of the inorganic filler were observed. The dispersibility was evaluated based on the following criteria. The results are shown in Tables 2 and 3. {standard} A: The inorganic filler was uniformly dispersed in the alcohol. Δ: Polymer-derived aggregates were found in part of the alcohol, and part of the inorganic filler was aggregated. ×: A large amount of polymer-derived aggregates were found in the alcohol, and most of the inorganic filler was aggregated.

[0098] [Standing stability] The coating compositions of each Example and Comparative Example were transferred to a test tube and left to stand for 1 hour. After that, the dispersibility of the inorganic filler was observed. The static stability was evaluated based on the following criteria. The results are shown in Tables 2 and 3. {standard} A: The inorganic filler was uniformly dispersed in the alcohol. △: A part of the inorganic filler was precipitated. ×: Most of the inorganic filler was precipitated.

[0099] [Coating ability on PET film] The coating composition of each Example and Comparative Example was applied to a PET film using a bar coater, and then dried at 40°C to obtain a coating film. The appearance of the coating film was then observed. The coatability to the PET film was evaluated based on the following criteria. The results are shown in Tables 2 and 3. {standard} A: The coating was uniform. △: Unevenness was observed in some areas of the coating. ×: Unevenness was observed in most of the application.

[0100] [Adhesion to PET film] The surface of the coating film prepared in the above coating property evaluation was rubbed five times with a stainless steel spoon. The adhesion to the PET film was evaluated based on the following criteria. The results are shown in Tables 2 and 3. {standard} A: The coating film did not peel off. △: Part of the coating peeled off. ×: Most of the coating film peeled off.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3]

Claims

1. The composition includes a polymer, an alcohol, and an inorganic filler, The coating composition, wherein the polymer comprises structural units derived from isopropenyl toluene and structural units derived from isopropenyl phenol.

2. The content ratio of the polymer is 80 parts by mass to 200 parts by mass relative to 100 parts by mass of the inorganic filler, 2. The coating composition according to claim 1, wherein the content of the alcohol is 300 parts by mass to 400 parts by mass with respect to 100 parts by mass of the inorganic filler.

3. The content ratio of the polymer is 120 parts by mass to 180 parts by mass relative to 100 parts by mass of the inorganic filler, 2. The coating composition according to claim 1, wherein the content of the alcohol is 300 parts by mass to 350 parts by mass with respect to 100 parts by mass of the inorganic filler.

4. 2. The coating composition according to claim 1, wherein the polymer has a weight average molecular weight of 400 to 1,000.

5. 2. The coating composition according to claim 1, wherein the polymer contains structural units derived from isopropenylphenol in an amount of 2 mol % to 30 mol %.

6. 10. The coating composition of claim 1, wherein the alcohol is isopropyl alcohol or methanol.

7. The inorganic filler is an inorganic particle, 2. The coating composition according to claim 1, wherein the inorganic particles have an average primary particle size of 0.1 μm to 100 μm.

8. The coating composition according to any one of claims 1 to 7, wherein the inorganic filler is silica or talc.

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