Coating components

Abstract

The present invention provides a water-repellent coating composition that allows easy removal of stains and has a good appearance because the water-repellent component has good compatibility with other materials. [Solution] The present invention provides a coating composition comprising a siloxane group-containing polymer (A) and a crosslinking agent (B), the siloxane group-containing polymer (A) is a block copolymer comprising an A block and a B block, the A block comprising at least a structural unit derived from a siloxane group-containing vinyl monomer (a), and the B block comprising a structural unit derived from a hydroxyl group-containing vinyl monomer (b) and, if necessary, a structural unit derived from another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b); The coating composition is a copolymer polymerized by living radical polymerization and has a molecular weight distribution (Mw / Mn) of 2.0 or less.

Description

[Technical Field]

[0001] The present invention relates to a coating composition, and more particularly to a coating composition that provides a coating film having water repellency. [Background technology]

[0002] There is a demand for car surfaces that are wash-free, meaning that dirt can be washed away with rainwater without the need for a car wash. There are two types of car wash-free technology: one is to make the surface hydrophilic so that dirt can be washed away with rainwater, and the other is to make the surface water-repellent so that water droplets are blown away along with the dirt while driving. However, people tend to prefer water-repellent exteriors that repel water when it comes to the exteriors of luxury cars.

[0003] To make a coating surface water-repellent, fluorine-based or silicone-based materials are often used as water-repellent materials. While fluorine-based materials are highly water-repellent and effective, they are currently expensive, making them difficult to use in general-purpose coatings, and present problems such as environmental pollution, making them difficult to use. Silicone-based materials have the advantage of being easy to use for general purposes, and are therefore being developed at the forefront. For example, Japanese Patent Laid-Open Publication No. 11-293184 (Patent Document 1) proposes a polymer composition using a siloxane macromonomer with unsaturated bonds at both ends. However, silicone-based materials have lower water-repellent properties than fluorine-based materials, which inevitably increases the amount of material used, leading to problems with compatibility with other materials and adhesion to the base coating. Silicone-based materials also have problems with tensile strength and tear strength, and it is said that their abrasion resistance also needs improvement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-293184 Summary of the Invention [Problem to be solved by the invention]

[0005] To provide a water-repellent coating composition that allows easy removal of stains and has a good appearance because the water-repellent component has high compatibility with other materials. [Means for solving the problem]

[0006] That is, the present invention provides: [1] A coating composition comprising a siloxane group-containing polymer (A) and a crosslinking agent (B), the siloxane group-containing polymer (A) is a block copolymer comprising an A block and a B block, the A block comprising at least a structural unit derived from a siloxane group-containing vinyl monomer (a), and the B block comprising a structural unit derived from a hydroxyl group-containing vinyl monomer (b) and, if necessary, a structural unit derived from another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b); and the molecular weight distribution (Mw / Mn) is 2.0 or less, and the copolymer is polymerized by living radical polymerization. The present invention also provides the following aspects:

[0007] [2] The coating composition according to [1], wherein the siloxane group-containing polymer (A) is an AB diblock copolymer or an ABA triblock copolymer. [3] The coating composition according to [1] or [2], wherein the weight average molecular weight (Mw) of the siloxane group-containing polymer (A) is 5,000 to 100,000. [4] The living radical polymerization is carried out by the following formula (1): [ka] [In the formula, R 1 represents a C1 to C8 alkyl group, an aryl group, a substituted aryl group, or an aromatic heterocyclic group. 2 and R 3 represents a hydrogen atom or a C1 to C8 alkyl group. 4represents an aryl group, a substituted aryl group, an aromatic heterocyclic group, an acyl group, an oxycarbonyl group, or a cyano group. The coating composition according to any one of [1] to [3], wherein the polymerization is carried out using an organotellurium compound represented by the following formula: [5] The coating composition according to any one of [1] to [4], further comprising a hydroxyl group-containing polymer (C). [6] The coating composition according to any one of [1] to [5], wherein the blending ratio of the siloxane group-containing polymer (A) to the hydroxyl group-containing polymer (C) is 15:85 to 80:20 by weight ratio of the siloxane group-containing polymer (A):hydroxyl group-containing polymer (C). [7] The coating composition according to any one of [1] to [6], wherein the siloxane group-containing vinyl monomer (a) has a number average molecular weight (Mn) of 500 to 50,000. [8] The coating composition according to any one of [1] to [7], wherein the crosslinking agent (B) is an isocyanate-based crosslinking agent. [Effects of the Invention]

[0008] In the present invention, the incorporation of a siloxane group-containing polymer can impart water repellency to a coating film. The siloxane group-containing polymer is firmly incorporated into the coating film through the crosslinking reaction of the coating film, preventing separation or bleeding and allowing water repellency to be maintained stably and for a long period of time. Furthermore, when the siloxane group-containing polymer is a block copolymer, the portion that contributes to the crosslinking reaction of the coating film and the siloxane portion that imparts water repellency are separated within the polymer molecule, allowing each portion to function without interference from the other portions, allowing the fixing function of the crosslinked portion and the function of the polysiloxane portion in providing water repellency to be clearly exerted over a long period of time. As a result, water repellency can be achieved even with a small amount of siloxane group-containing polymer incorporated.

[0009] When a coating film formed from the coating composition of the present invention is present on the surface of an automobile or the like, the water repellency is maintained stably for a long period of time, so that rainwater and the like turns into droplets (bead-shaped droplets) and splashes off while the vehicle is traveling. Therefore, when it rains, dirt such as dust present on the coating film is absorbed by the rainwater and splashed off while the vehicle is traveling, removing it from the coating film. The siloxane moiety also has oil repellency, so adhesion of oily substances is reduced, and oily dirt is also reduced.

[0010] Furthermore, when the siloxane group-containing polymer (A) of the present invention is used, the siloxane group moieties remain firmly present in the coating film without separating and bleeding, allowing the polymer to not only exhibit its performance stably for a long period of time, but also maintain other properties of the coating film, such as tensile strength, tear strength, and abrasion resistance, without adversely affecting them, and therefore these properties are also maintained at a high level. [Brief explanation of the drawings]

[0011] [Figure 1] Photographs of the coating films formed in Examples 1, 3, 4, 5 and 9 observed with a transmission electron microscope (TEM) are shown. DETAILED DESCRIPTION OF THE INVENTION

[0012] The coating composition of the present invention contains a siloxane group-containing polymer (A) and a crosslinking agent (B), and may optionally contain a separate hydroxyl group-containing polymer (C). Each of these components will now be described.

[0013] <Siloxane Group-Containing Polymer (A)> The siloxane group-containing polymer (A) is a block copolymer comprising an A block and a B block, wherein the A block contains structural units derived from at least a siloxane group-containing vinyl monomer (a), and the B block contains structural units derived from a hydroxyl group-containing vinyl monomer (b) and, if necessary, another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b); The copolymer has a molecular weight distribution (Mw / Mn) of 2.0 or less and is polymerized by living radical polymerization. In this specification, the term "vinyl monomer" refers to a monomer having a radically polymerizable carbon-carbon double bond in the molecule. The term "structural unit derived from a vinyl monomer" refers to a structural unit in which the radically polymerizable carbon-carbon double bond of a vinyl monomer is polymerized to form a carbon-carbon single bond.

[0014] The siloxane group-containing vinyl monomer (a) is not particularly limited as long as it is a vinyl monomer having a siloxane group (more specifically, a polysiloxane group). More specifically, the siloxane group-containing vinyl monomer is represented by the following formula I: [ka] [In the formula, Me represents a methyl group, and R 11 represents a hydrogen atom or a methyl group, and R 12 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 13 represents an alkyl group having 1 to 6 carbon atoms which may contain an oxygen atom, and n represents 0 or an integer of 1 or more.] The siloxane group-containing vinyl monomer (a) of the above formula (I) is represented by the following formula II: [ka] In the above formula I, a reaction product of an alcohol group at the terminal of a polysiloxane represented by the formula (I) with (meth)acrylic acid is preferred. 11 is a group derived from (meth)acrylic acid and represents a hydrogen atom or a methyl group. 12 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Me is a methyl group. 13 is an alkyl group having 1 to 6 carbon atoms. n is an integer of 0 or 1 or more, and n is preferably 6 to 300. In this specification, "(meth)acrylic" or "(meth)acrylate" means either or both of acrylic and methacrylic, and either or both of acrylate and methacrylate.

[0015] More specifically, the siloxane group-containing vinyl monomer (a) having the above formula (I) is commercially available from Shin-Etsu Chemical Co., Ltd. (modified silicone oil series) and JNC Corporation (Silaplane (registered trademark)), and examples thereof include X-22-2404 [functional group equivalent (g / mol): 420] [number average molecular weight: 420], X-22-174ASX [functional group equivalent (g / mol): 900] [number average molecular weight: 900], and X-22-174BX, all manufactured by Shin-Etsu Chemical Co., Ltd. Examples include KF-2012 [functional group equivalent (g / mol): 2,300] [number average molecular weight: 2,300], KF-2012 [functional group equivalent (g / mol): 4,600], X-22-2426 [functional group equivalent (g / mol): 12,000] [number average molecular weight: 12,000], and FM-0711 [number average molecular weight: 1,000], FM-0721 [number average molecular weight: 5,000], and FM-0725 [number average molecular weight: 10,000] (all trade names) manufactured by JNC Corporation. Note that when the siloxane group-containing vinyl monomer is monofunctional, the functional group equivalent [g / mol] can be regarded as the number average molecular weight of the siloxane group-containing vinyl monomer (a) per mole of siloxane.

[0016] From the viewpoint of polymerizability, the functional group equivalent weight of the siloxane group-containing vinyl monomer (a) is preferably 500 to 50,000, more preferably 600 to 3,000, and particularly preferably 700 to 1,200. In particular, excellent compatibility is exhibited when the functional group is 700 to 1,200. It is preferable that the functional group is a vinyl group, and that the siloxane group-containing vinyl monomer (a) is monofunctional from the viewpoint of polymerizability.

[0017] The number average molecular weight (Mn) of the siloxane group-containing vinyl monomer (a) is preferably 500 to 50,000 in terms of releasability, more preferably 600 to 3,000, and particularly preferably 700 to 1,200. In particular, a number of 700 to 1,200 shows excellent compatibility.

[0018] The hydroxyl group-containing vinyl monomer (b) is a vinyl monomer having a hydroxyl group in the molecule, and more specifically, a reaction product of alkyl polyol and (meth)acrylic acid is suitable. Examples of the hydroxyl group-containing vinyl monomer (b) include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, glycerin monoacrylate, glycerin monomethacrylate, glycerin diacrylate, and glycerin dimethacrylate. polyethylene glycol mono(meth)acrylates such as diethylene glycol monoacrylate, triethylene glycol monoacrylate, triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, hexaethylene glycol monoacrylate, octaethylene glycol monoacrylate, diethylene glycol monomethacrylate, triethylene glycol monomethacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, hexaethylene glycol monomethacrylate, and octaethylene glycol monomethacrylate.

[0019] The other copolymerizable vinyl monomer (c) may be any vinyl monomer copolymerizable with the vinyl monomers (a) and (b), and examples thereof include linear or branched alkyl (meth)acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, and octyl methacrylate; Carboxyl group-containing monomers such as (meth)acrylic acid, dimer acids of acrylic acid such as β-carboxyethyl acrylate; alicyclic ring-containing monomers such as cyclohexyl (meth)acrylate, cyclohexyloxyalkyl (meth)acrylate, t-butylcyclohexyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; phosphate group-containing (meth)acrylates such as phosphate esters of polyethylene glycol mono(meth)acrylate, phosphate esters of polypropylene glycol mono(meth)acrylate such as mono(propylene glycol monomethacrylate) phosphate, alkylene (meth)acrylate phosphates such as methylene (meth)acrylate phosphate, trimethylene (meth)acrylate phosphate, propylene (meth)acrylate phosphate, and tetramethylene (meth)acrylate phosphate; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, sulfonic acid group-containing monomers, or salts thereof; Alkoxyalkyl (meth)acrylamide monomers such as methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, isopropoxymethyl (meth)acrylamide, n-butoxymethyl (meth)acrylamide, and isobutoxymethyl (meth)acrylamide, (meth)acryloyl (meth)acrylamide-based monomers such as morpholine, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, (meth)acrylamide N-methylol(meth)acrylamide, etc.; Glycidyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, glycidyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, methyl vinyl ketone, styrene, α-methylstyrene, N-vinyl caprolactam, vinyl acetate, etc.; In particular, isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate are preferred from the viewpoint of the balance of the physical properties of the coating film.

[0020] The siloxane group-containing polymer (A) preferably contains 5 to 35% by weight of structural units derived from polysiloxane group-containing vinyl monomer (a), 5 to 35% by weight of structural units derived from hydroxyl group-containing vinyl monomer (b), and 30 to 90% by weight of structural units derived from another vinyl monomer (c) copolymerizable with vinyl monomers (a) and (b). A relatively high content of siloxane group-containing vinyl monomer (a) will impart water repellency to the coating film, but too much structural unit derived from siloxane group-containing vinyl monomer (a) is undesirable because it adversely affects the coating film. A high content of structural units derived from hydroxyl group-containing vinyl monomer (b) is preferred because it allows copolymerization at multiple reaction sites. The amount of structural units derived from the hydroxyl group-containing vinyl monomer (b) can be controlled by the hydroxyl value of the siloxane group-containing polymer (A), which preferably has a hydroxyl value of 30 to 250 mgKOH / g, particularly preferably 70 to 170 mgKOH / g. If the hydroxyl value is less than 30 mgKOH / g, the polymer may not react sufficiently with isocyanate, resulting in a coating film with low crosslink density, while if the hydroxyl value is more than 250 mgKOH / g, the coating film may have poor water resistance.

[0021] The siloxane group-containing polymer (A) is a block copolymer comprising an A block and a B block, where the A block contains structural units derived from a polysiloxane group-containing vinyl monomer (a), and the B block contains structural units derived from a hydroxyl group-containing vinyl monomer (b). The B block preferably further contains structural units derived from another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b). The block copolymer is preferably an AB diblock copolymer or an ABA triblock copolymer. More specifically, the A block of the block copolymer contains structural units derived from the polysiloxane group-containing vinyl monomer (a), which can impart water and oil repellency to the coating film. The B block of the block copolymer contains structural units derived from the hydroxyl group-containing vinyl monomer (b), which can crosslink with the crosslinking agent (B) to form a three-dimensional network structure, improving durability. In other words, the hydroxyl group-containing vinyl monomer (b), which is reactive with a crosslinking agent, is not introduced into the A block but is concentrated in the B block, making it possible to clearly distinguish the functions played by each polymer block, the A block and the B block.

[0022] Furthermore, when the A and B blocks have different polarities or are incompatible with each other, or when a polymer compatible with the A or B blocks is present, a microphase-separated structure may form in the coating film. In particular, when a microphase-separated structure is present in the coating film, the functions of each polymer block, the A and B, are most clearly separated, resulting in excellent functionality. Microphase-separated structures can be microscopically confirmed to have an island-in-the-sea (spherical) structure, a columnar (linear) structure, or a lamellar structure by thinly slicing the coating film and taking a transmission electron microscope (TEM) photograph.

[0023] When the copolymer is not a block polymer but a randomly copolymerized polymer, the structural units derived from the polysiloxane group-containing vinyl monomer (a) and the structural units derived from the hydroxyl group-containing vinyl monomer (b) that are reactive with the crosslinking agent are mixed, and therefore the polymer may not be able to exhibit its function well or may have poor compatibility depending on the composition.

[0024] As a method for producing an AB type diblock copolymer of the siloxane group-containing polymer (A) of the present invention, the A block may be produced first and then a monomer for the B block may be polymerized onto the A block; the B block may be produced first and then a monomer for the A block may be polymerized onto the B block; or the A block and the B block may be produced separately and then the A block and the B block may be coupled together.

[0025] For example, it can be obtained by sequentially polymerizing vinyl monomers constituting the blocks by radical polymerization. Specifically, it can be produced by a production method including a step of polymerizing a vinyl monomer constituting one of the A block and the B block to polymerize the one block, and a step of polymerizing the one block, and then polymerizing a vinyl monomer constituting the other of the A block and the B block to polymerize the other block.

[0026] The effects of the present invention are difficult to achieve when using acrylic polymers obtained by conventional radical polymerization (free radical polymerization: FRP). In free radical polymerization, radical species are continuously generated during the reaction and add to the vinyl monomer, causing the polymerization to proceed. Therefore, free radical polymerization produces polymers in which the propagating terminal radicals are deactivated during the reaction, and polymers propagated by newly generated radical species during the reaction. Therefore, when an acrylic polymer containing crosslinkable functional groups is produced by free radical polymerization, a polymer is produced that does not contain structural units derived from the relatively low molecular weight vinyl monomer containing the crosslinkable functional group.

[0027] In crosslinkable acrylic polymers polymerized by free radical polymerization, the polymer composition is heterogeneous, and since the polymer contains polymers that do not contain relatively low molecular weight crosslinkable functional group-containing vinyl monomers, there are polymer chains that cannot participate in crosslinking.Furthermore, the composition is heterogeneous, and for example, homopolymers in which only siloxane-containing vinyl monomers are polymerized are produced, which can cause deterioration of resin compatibility and can lead to coating defects such as cloudiness and even cissing.

[0028] Therefore, it is a copolymer polymerized by living radical polymerization. Living radical polymerization, compared to the above-mentioned free radical polymerization, yields polymers with more uniform molecular weight and composition, and can suppress the generation of low-molecular-weight components, making bleed-out over time less likely. Living radical polymerization methods include those using transition metal catalysts (ATRP), those using sulfur-based reversible chain transfer agents (RAFT), and those using organotellurium compounds (TERP), depending on the method used to stabilize the polymer growth terminal. Because the ATRP method uses amine complexes, it may not be possible to use it unless the acidic groups of vinyl monomers containing acidic groups are protected. When using a variety of monomers, the RAFT method is difficult to achieve a low molecular weight distribution and may have problems such as a sulfur odor and coloration. Among these methods, the TERP method is preferred from the perspectives of the variety of monomers that can be used, molecular weight control in the polymer region, uniform composition, and coloration. The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, and is a method described, for example, in WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, and WO 2004 / 096870.

[0029] As the TERP method, a method of polymerization using an organotellurium compound represented by the following formula (1) is preferred, and a method of polymerization using a mixture of an organotellurium compound represented by the following formula (1) and an organic ditelluride compound represented by the following formula (2) is more preferred. The following formula (1): [ka] [In the formula, R 1 represents a C1 to C8 alkyl group, an aryl group, a substituted aryl group, or an aromatic heterocyclic group. 2 and R 3 represents a hydrogen atom or a C1 to C8 alkyl group. 4 represents an aryl group, a substituted aryl group, an aromatic heterocyclic group, an acyl group, an oxycarbonyl group, or a cyano group. Formula (2): (R 1 Te)2(2) [In the formula, R 1 is the same as above.

[0030] Specific examples of the organic tellurium compound represented by formula (1) include ethyl-2-methyl-2-n-butyltellanyl-propionate, ethyl-2-n-butyltellanyl-propionate, (2-hydroxyethyl)-2-methyl-methyltellanyl-propionate, and the organic tellurium compounds described in WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, and WO 2004 / 096870. Specific examples of the organic ditelluride compound represented by formula (2) include dimethyl ditelluride and dibutyl ditelluride.

[0031] In the polymerization process, a vinyl monomer, an organotellurium compound of general formula (1), and an organic ditelluride compound of formula (2) are mixed in a vessel purged with an inert gas for the purpose of promoting the reaction and controlling the molecular weight and molecular weight distribution depending on the type of vinyl monomer. Examples of inert gases used in this process include nitrogen, argon, and helium. Argon and nitrogen are preferred. The amount of vinyl monomer used can be adjusted appropriately depending on the physical properties of the desired copolymer.

[0032] Polymerization is typically carried out without a solvent, but organic solvents commonly used in radical polymerization may also be used. Examples of solvents that can be used include benzene, toluene, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, and trifluoromethylbenzene. Aqueous solvents can also be used, such as water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, and 1-methoxy-2-propanol. The amount of solvent used can be adjusted appropriately; for example, 0.01 to 100 ml of solvent per 1 g of vinyl monomer is preferred. The reaction temperature and reaction time can be adjusted appropriately depending on the molecular weight or molecular weight distribution of the resulting copolymer; however, the reaction is typically carried out at 0°C to 150°C and stirred for 1 minute to 100 hours. After completion of the polymerization reaction, the solvent and residual vinyl monomer can be removed from the resulting reaction mixture by conventional separation and purification techniques, and the target copolymer can be isolated.

[0033] Living radical polymerization is a type of polymerization in which molecular chains grow without being hindered by side reactions such as termination reactions or chain transfer reactions. In living radical polymerization, all polymer chains react uniformly with monomers during the reaction, resulting in a uniform composition of the entire polymer. When such crosslinkable acrylic polymers are crosslinked using a crosslinking agent, almost all of the polymer can participate in crosslinking between polymer chains.

[0034] The siloxane group-containing polymer (A) is obtained by copolymerizing a polysiloxane group-containing vinyl monomer (a), a hydroxyl group-containing vinyl monomer (b), and another unsaturated monomer (c) copolymerizable therewith, as described above, and preferably has a number average molecular weight (Mn) of 3,000 to 100,000. Furthermore, the molecular weight distribution (Mw / Mn) of the siloxane group-containing polymer (A) is preferably 2.0 or less.

[0035] The number-average molecular weight (Mn) of the siloxane group-containing polymer (A) is relatively high, ranging from 3,000 to 100,000, making it less susceptible to bleeding and allowing the initial surface properties to be maintained for a long period of time. The weight-average molecular weight (Mw) of the siloxane group-containing polymer (A) is preferably from 5,000 to 100,000. The lower limit of Mw is more preferably 8,000. The upper limit of Mw is more preferably 80,000, even more preferably 30,000, and most preferably 20,000. If the number-average molecular weight and weight-average molecular weight are lower than the lower limits, bleeding is likely to occur. Conversely, if they are higher than the upper limits, the viscosity may increase, making handling difficult and causing cloudiness.

[0036] When the molecular weight distribution (Mw / Mn) of the siloxane group-containing polymer is 2.0 or less, the molecular weight distribution is sharp, and compatibility with the coating film is good, resulting in a uniform and transparent coating film. The Mw / Mn of the block copolymer is preferably 1.8 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. In the present invention, the molecular weight distribution is calculated by (weight average molecular weight (Mw) of the block copolymer) / (number average molecular weight (Mn) of the block copolymer). The smaller the Mw / Mn, the narrower the molecular weight distribution and the more uniform the copolymer, and when this value is 1.0, the molecular weight distribution is narrowest. Conversely, the larger the Mw / Mn, the more likely the polymer contains molecules with molecular weights smaller or larger than the molecular weight of the designed polymer, which can result in poor compatibility. While a polymer with a molecular weight that is too small will dissolve, it can cause coating problems such as bleed-out. However, a polymer with a molecular weight that is too large will have poor solubility in other polymer resins, resulting in problems such as cloudy coating films.

[0037] <Crosslinking agent (B)> The crosslinking agent to be blended in the coating composition of the present invention is not particularly limited, but may be one that undergoes a crosslinking reaction with the hydroxyl groups present in the siloxane group-containing polymer (A), and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aminoplast resins, glyoxal, etc. These crosslinking agents may be used alone or in combination of two or more.

[0038] An isocyanate crosslinking agent refers to a compound having two or more isocyanate groups in one molecule. Examples of the isocyanate crosslinking agent include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates. The isocyanate crosslinking agents may be used alone or in combination of two or more.

[0039] Examples of the aliphatic polyisocyanate used in the crosslinking agent (B) include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6- aliphatic diisocyanates such as diisocyanatomethyl caproate; and aliphatic triisocyanates such as lysine ester triisocyanate, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0040] Examples of alicyclic polyisocyanates include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), 4,4'-methylenebis(cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, and methyl- Alicyclic diisocyanates such as 2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, and norbornane diisocyanate; for example, 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl) -bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-isocyanatoethyl)- Examples include alicyclic triisocyanates such as 2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane.

[0041] Examples of the araliphatic polyisocyanate include araliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; and araliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0042] Examples of aromatic polyisocyanates include aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4'- or 4,4'-diphenylmethane diisocyanate or a mixture thereof, 2,4- or 2,6-tolylene diisocyanate or a mixture thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenylether diisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4'''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0043] The aromatic polyisocyanates are undesirable from the viewpoint of weather resistance because they tend to yellow when exposed to ultraviolet light, whereas aliphatic polyisocyanates are preferred from the viewpoint of weather resistance and the like, and may be used in combination with alicyclic polyisocyanates as needed.

[0044] Furthermore, examples of polyisocyanate derivatives include dimers, trimers, biurets, allophanates, carbodiimides, uretdione, uretoimine, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), and crude TDI of the above-mentioned polyisocyanate curing agents. In particular, biurets, allophanates, and isocyanurates are preferred, with isocyanurates being most preferred from the viewpoint of the balance of physical properties of the coating film.

[0045] The isocyanate crosslinking agent is usually used after blocking the isocyanate group with a blocking agent. The blocking agent is stable at room temperature, but can regenerate free isocyanate groups when heated above its dissociation temperature. Examples of the blocking agent include compounds having active hydrogen groups (e.g., alcohols, oximes, etc.). Preferred examples of blocking agents include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenol carbinol, and methylphenyl carbinol; cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono 2-ethylhexyl ether; polyether-type diols terminated at both ends such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol phenol; polyester-type polyols terminated at both ends obtained from diols such as ethylene glycol, propylene glycol, and 1,4-butanediol and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, and sebacic acid; phenols such as para-t-butylphenol and cresol; oximes such as dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, methyl amyl ketoxime, and cyclohexanone oxime; and lactams represented by ε-caprolactam and γ-butyrolactam. Among these, blocked isocyanate compounds obtained by blocking hexamethylene diisocyanate or its nurate with a blocking agent are more preferably used.

[0046] In the coating composition of the present invention, the siloxane group-containing polymer (A) and polyisocyanate curing agent are mixed at a ratio of the isocyanate group equivalent of the isocyanate crosslinking agent to the hydroxyl group equivalent of the siloxane group-containing polymer (A) of preferably 0.5 to 2.5, more preferably 0.9 to 1.5, from the viewpoints of the curability of the coating film and the stability of the composition. If the ratio of the isocyanate group equivalent of the polyisocyanate curing agent to the hydroxyl group equivalent of the siloxane group-containing polymer (A) is less than 0.5, crosslinking will be insufficient, and if it is more than 2.5, yellowing due to heat will occur easily.

[0047] The epoxy crosslinking agent used as the crosslinking agent (B) is a compound having two or more epoxy groups as reactive groups in one molecule. The epoxy crosslinking agents may be used alone or in combination of two or more.

[0048] Examples of epoxy crosslinking agents include epoxy resins made from bisphenol A and epichlorohydrin, ethylene glycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, diamine glycidylamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0049] In the coating composition of the present invention, the siloxane group-containing polymer (A) and the epoxy crosslinking agent are mixed in such a ratio that the ratio of the epoxy equivalent of the epoxy crosslinking agent to the hydroxyl equivalent of the siloxane group-containing polymer (A) is preferably 0.5 to 2.5, more preferably 0.9 to 1.5, from the viewpoints of the curability of the coating film and the stability of the composition. If the ratio of the epoxy equivalent of the epoxy crosslinking agent to the hydroxyl equivalent of the siloxane group-containing polymer (A) is less than 0.5, the crosslinking performance will be insufficient, and if it is more than 2.5, yellowing due to heat will easily occur.

[0050] Aminoplast resins are condensation products of aldehydes such as formaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with amino- or amide-group-containing substances such as urea, melamine, and benzoguanamine, and include benzoguanamine-formaldehyde resins, melamine-formaldehyde resins, esterified melamine-formaldehyde resins, and urea-formaldehyde resins.

[0051] <Hydroxyl Group-Containing Polymer (C)> The coating composition of the present invention can contain a hydroxyl group-containing polymer (C) as needed. Examples of the hydroxyl group-containing polymer (C) include acrylic resins, silicone acrylic resins, polyester resins, alkyd resins, silicone polyester resins, epoxy resins, epoxy ester resins, and fluororesins. Of these, acrylic resins, polyester resins, alkyd resins, epoxy resins, and epoxy ester resins are preferred. The hydroxyl group-containing polymer (C) is preferably an acrylic resin containing hydroxyl groups (hereinafter sometimes referred to as "acrylic polyol resin"), due to ease of control of functional groups and ease of production.

[0052] The acrylic polyol resin can be prepared using one or more unsaturated monomers that are commonly used in the preparation of acrylic resins, such as (meth)acrylic monomers, hydroxyl group-containing acrylic monomers, and other copolymerizable monomers.

[0053] The (meth)acrylic monomer is not particularly limited, and examples thereof include alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-, i-, or t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; amides such as (meth)acrylamide; and nitriles such as (meth)acrylonitrile.

[0054] The hydroxyl group-containing acrylic monomer is preferably the same as the hydroxyl group-containing vinyl monomer (b) used in the synthesis of the siloxane group-containing polymer (A). Further, other copolymerizable monomers include monomers that copolymerize with the acrylic monomer, such as styrenes, α-methylstyrene, and vinyl compounds, such as vinyl acetate.

[0055] The method for producing the acrylic polyol resin is not particularly limited, and can be carried out by, for example, solution polymerization such as ordinary radical polymerization.

[0056] The acrylic polyol resin preferably has a weight-average molecular weight (Mw) of 1,000 to 20,000. By having the weight-average molecular weight within this range, it is possible to maintain a good balance between the viscosity of the coating composition and the physical properties of the resulting coating film, such as the weather resistance of the coating film.

[0057] The quantitative ratio of the siloxane group-containing polymer (A) to the hydroxyl group-containing polymer (C) is preferably 15:85 to 80:20 by weight (siloxane group-containing polymer (A):hydroxyl group-containing polymer (C)). When the weight ratio is within this range, the hydroxyl group-containing polymer (C) is compatible with the siloxane group-containing polymer (A) that forms a microphase-separated structure, thereby controlling microphase separation. Furthermore, the structural units derived from the polysiloxane group-containing vinyl monomer (a) in the A-chain polymer block efficiently impart antifouling properties, such as water and oil repellency, to the coating film. The weight ratio of the siloxane group-containing polymer (A):hydroxyl group-containing polymer (C) is preferably 20:80 to 75:25, more preferably 30:70 to 60:40.

[0058] <Paint composition> The coating composition of the present invention can be prepared by mixing the components constituting the coating composition by any commonly used means. The coating composition may contain, as necessary, pigments, surface conditioners (antifoaming agents, leveling agents, etc.), pigment dispersants, plasticizers, film-forming aids, ultraviolet absorbers, antioxidants, flame retardants, antistatic agents, electrostatic aids, heat stabilizers, light stabilizers, solvents (water, organic solvents), and other additives.

[0059] The coating composition of the present invention is cured preferably at 70 to 170°C, more preferably 70 to 160°C, and even more preferably 70 to 150°C after being applied to an object to be coated.

[0060] <Object to be coated> Substrates to which the coating composition of the present invention can be applied include steel plates made of metals such as iron, steel, stainless steel, aluminum, copper, zinc, and tin, as well as alloys thereof; polyethylene resin, EVA resin, polyolefin resin (e.g., polyethylene resin, polypropylene resin), vinyl chloride resin, styrene resin, polyester resin (including PET resin, PBT resin, etc.), unsaturated polyester resin, polycarbonate resin, acrylic resin, acrylonitrile butadiene styrene (ABS) resin, acrylonitrile styrene (AS) resin, polyamide resin, acetal resin, phenolic resin, fluororesin, melamine resin, urethane resin, epoxy resin, and polyphenylene oxide (PPO); and organic-inorganic hybrid materials, which may be in a molded state. The coating composition of the present invention is particularly effective when applied to easily electrostatically charged materials such as polyethylene resin, polyolefin resin (e.g., polyethylene resin, polypropylene resin), styrene resin, polyester resin (including PET resin, PBT resin, etc.), and polycarbonate resin, as well as unsaturated polyester resins used in FRP and CFRP.

[0061] The coating or application of the coating composition of the present invention is not particularly limited and can be carried out by any commonly used coating or application method. For example, when applying the coating composition of the present invention to an automobile body, in order to enhance the appearance of the resulting coating film, multi-stage coating by air electrostatic spray coating, preferably two-stage coating, or a coating method combining air electrostatic spray coating with a rotary atomizing electrostatic coater commonly known as a "μμ (micro) bell," "μ (micro) bell," or "metabell," can be used. When applying to a film or the like, methods such as roll coating, kiss roll coating, gravure coating, bar coating, knife coating, curtain coating, lip coating, and extrusion coating using a die coater can be used. Furthermore, hand coating or brush coating using fibers impregnated with the coating composition of the present invention is also possible. For example, a suitable amount of the composition can be impregnated into a dry fiber such as a sponge or rag, and then thinly spread by hand on the surface of the substrate, followed by natural drying or forced drying using a dryer or the like to form a coating film.

[0062] The thickness of the coating film formed from the coating composition of the present invention is preferably, for example, 0.5 μm to 50 μm, more preferably 1 μm to 30 μm, as a dry film thickness. [Example]

[0063] The present invention will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0064] [Production of Copolymer] Production Example 1 Production of Siloxane Group-Containing Polymer (A-1) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 1.49 g of ethyl 2-methyl-2-n-butyltellanyl propionate (BTEE), 0.92 g of dibutyl ditelluride (DBDT), 42 g of 2-hydroxyethyl methacrylate (HEMA), 98 g of isobutyl methacrylate (iBMA), 0.33 g of 2,2'-azobis(isobutyronitrile) (AIBN), and 140 g of butyl acetate (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize the B block.

[0065] A mixed solution (second monomer composition) of 60.0 g of a siloxane group-containing acrylic monomer (X-22-174ASX manufactured by Shin-Etsu Chemical Co., Ltd. [functional group equivalent (g / mol)]: 900 [number average molecular weight: 900]; abbreviated as "PDMSA" in Table 1) previously purged with argon, 0.33 g of AIBN, and 60 g of butyl acetate was added to the reaction solution, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block. The physical properties of the resulting AB block siloxane group-containing polymer (A-1) are shown in Table 1. Table 1 also lists the monomer blend amount, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (organotellurium compound-based polymerization (TERP) / free radical polymerization (FRP)), polymer morphology (block polymer / random polymer), and block morphology (AB / ABA).

[0066] Production Example 2: Production of siloxane group-containing polymer (A-2) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 78 g of iBMA, 0.33 g of AIBN, and 120 g of butyl acetate (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize the B block.

[0067] To the reaction mixture was added a mixture (second monomer composition) of 60.0 g of X-22-174ASX, which had been previously purged with argon, 20 g of a phosphate-containing monomer (mono(propylene glycol monomethacrylate) phosphate, manufactured by Johoku Chemical Industry Co., Ltd., product name: JAMP-100N; abbreviated as "PO4(JAMP)" in Table 1), 0.33 g of AIBN, and 60 g of butyl acetate, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block. The physical properties of the resulting AB-block siloxane-containing polymer (A-2), including its weight-average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer morphology (block polymer / random polymer), block morphology (AB / ABA), and monomer composition, are shown in Table 1.

[0068] Production Example 3: Production of siloxane group-containing polymer (A-3) A siloxane group-containing polymer (A-3) was obtained in the same manner as in Production Example 1, except that 140 g of iBMA was used instead of 42 g of HEMA and 98 g of iBMA. The physical properties of the obtained siloxane group-containing polymer (A-3), including its weight-average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer form (block polymer / random polymer), block form (AB / ABA), and monomer composition, are shown in Table 1.

[0069] Production Example 4 Production of Siloxane Group-Containing Polymer (A-4) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 98 g of iBMA, 60 g of X-22-174ASX, 0.33 g of AIBN, and 400 g of butyl acetate (first monomer composition), and the mixture was reacted at 60°C for 36 hours to produce a random-structure siloxane group-containing polymer (A-4). The physical properties of the resulting random-structure siloxane group-containing polymer (A-4), including its weight-average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer morphology (block polymer / random polymer), block morphology (AB / ABA), and monomer composition, are shown in Table 1.

[0070] Production Example 5 Production of Siloxane Group-Containing Polymer (A-5) A 0.2 L separable flask equipped with a temperature controller, stirring blade, reflux condenser, and nitrogen inlet was charged with 30 g of butyl acetate, and the flask was purged with nitrogen. The inside of the flask was then heated to 120°C and maintained at a constant temperature. Meanwhile, a mixture of 20.88 g of HEMA, 49.12 g of iBMA, 30 g of X-22-174ASX, and 0.88 g of Kayaester O was placed in a dropping funnel and added dropwise over 3 hours.

[0071] After the reaction was continued for 1 hour, a mixture of 2 g of butyl acetate and 0.5 g of Kayaester O was added dropwise over 30 minutes as a post-initiator, and the reaction was continued for another hour to obtain a random structure siloxane group-containing polymer (A-5). The physical properties of the obtained random structure siloxane group-containing polymer (A-5), including its weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer morphology (block polymer / random polymer), block morphology (AB / ABA), and monomer composition, are shown in Table 1.

[0072] Production Example 6 Production of Siloxane Group-Containing Polymer (A-6) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 98 g of iBMA, 0.33 g of AIBN, and 140 g of butyl acetate (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize the B block.

[0073] A mixed solution (second monomer composition) of 60.0 g of siloxane group-containing acrylic monomer (X-22-174ASX manufactured by Shin-Etsu Chemical Co., Ltd.), 0.33 g of AIBN, and 60 g of butyl acetate, which had been previously purged with argon, was added to the reaction solution, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block. The physical properties of the resulting AB block siloxane group-containing polymer (A-6) are shown in Table 1. Table 1 also lists the monomer blend amount, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer form (block polymer / random polymer), and block form (AB / ABA) of the siloxane group-containing polymer (A-1).

[0074] Production Example 7 Production of Siloxane Group-Containing Polymer (A-7) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 98 g of iBMA, 0.33 g of AIBN, and 140 g of butyl acetate (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize the B block.

[0075] A mixed solution (second monomer composition) of 60.0 g of a siloxane group-containing acrylic monomer (X-22-174BX manufactured by Shin-Etsu Chemical Co., Ltd. [functional group equivalent (g / mol)]: 2300 [number average molecular weight: 2300]; abbreviated as "PDMSA" in Table 1) previously purged with argon, 0.33 g of AIBN, and 60 g of butyl acetate was added to the reaction solution, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block. The physical properties of the resulting AB block siloxane group-containing polymer (A-1) are shown in Table 1. Table 1 also lists the monomer blend amount, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer form (block polymer / random polymer), and block form (AB / ABA) of the siloxane group-containing polymer (A-7).

[0076] Production Example 8 Production of siloxane group-containing polymer (A-8) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 98 g of isobornyl methacrylate (IBXMA), 0.33 g of AIBN, and 140 g of butyl acetate (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize the B block.

[0077] A mixed solution (second monomer composition) of 60.0 g of siloxane group-containing acrylic monomer (X-22-174ASX manufactured by Shin-Etsu Chemical Co., Ltd.), 0.33 g of AIBN, and 60 g of butyl acetate, which had been previously purged with argon, was added to the reaction solution, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block. The physical properties of the resulting AB block siloxane group-containing polymer (A-8) are shown in Table 1. Table 1 also lists the monomer blend amount, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer form (block polymer / random polymer), and block form (AB / ABA) of the siloxane group-containing polymer (A-8).

[0078] Production Example 9 Production of Siloxane Group-Containing Polymer (A-9) A mixed solution (first monomer composition) of 60.0 g of a siloxane group-containing acrylic monomer (X-22-174ASX manufactured by Shin-Etsu Chemical Co., Ltd.), 0.33 g of AIBN, and 60 g of butyl acetate, which had been previously argon-substituted, was placed in a flask equipped with an argon gas inlet tube and a stirring blade, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block.

[0079] To the reaction solution, 42 g of HEMA, 98 g of iBMA, 0.33 g of AIBN, and 140 g of butyl acetate, which had been previously purged with argon, were added (second monomer composition), and the mixture was reacted at 60° C. for 36 hours to polymerize the B block.

[0080] A mixed solution (first monomer composition) of 60.0 g of siloxane group-containing acrylic monomer (X-22-174ASX manufactured by Shin-Etsu Chemical Co., Ltd.), 0.33 g of AIBN, and 60 g of butyl acetate, which had been previously purged with argon, was added to the reaction solution, and the mixture was allowed to react at 60°C for 36 hours to polymerize the A block. The physical properties of the resulting ABA triblock siloxane group-containing polymer (A-9) are shown in Table 1. Table 1 also lists the monomer blend amount, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, production method (TERP / FRP), polymer form (block polymer / random polymer), and block form (AB / ABA) of the siloxane group-containing polymer (A-9).

[0081] The number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were measured by the following methods. [Measurement of number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)] A calibration curve was prepared by gel permeation chromatography (GPC) using a TSKgel SuperMultipore HZ-H (Φ4.6 × 150) × 2 (Tosoh Corporation) column, tetrahydrofuran as the mobile phase, and polystyrene (TSK Standard, Tosoh Corporation) as the standard substance, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured. The molecular weight distribution (Mw / Mn) was calculated from these measurements.

[0082] Preparation of Hydroxyl-Containing Polymer (C) A 2-L separable flask equipped with a temperature controller, stirring blade, reflux condenser, and nitrogen inlet was charged with 444.27 g of butyl acetate, and the flask was purged with nitrogen and then heated to 130°C and maintained at that temperature. Meanwhile, a mixture of 255 g of styrene (ST), 8.5 g of methacrylic acid (MAA), 394.4 g of HEMA, 117.47 g of 2-ethylhexyl acrylate (EHA), 74.72 g of iBMA, and 102 g of Kayaester O was placed in a dropping funnel and added dropwise over 3 hours.

[0083] The reaction was continued for 1 hour, and then a mixture of 204 g of butyl acetate and 20.4 g of Kayaester O was added dropwise over 30 minutes as a post-initiator. The reaction was continued for another hour, and the mixture was diluted with butyl acetate to a solids content of 60%, yielding a hydroxyl-containing polymer (C). Table 1 shows the weight-average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, and production method (TERP / FRP) of the hydroxyl-containing polymer (C).

[0084] Table 1 also shows N3600 (low viscosity hexamethylene diisocyanate trimer: NCO%=23) manufactured by Covestro as the crosslinking agent (B), and the NCO / OH ratio thereof.

[0085] (Examples 1 to 12 and Comparative Examples 1 to 4) Paint composition and coating film preparation Siloxane group-containing polymers (A) (A-1 to A-9), N3600 (manufactured by Covestro, NCO%=23) as the crosslinker (B), and hydroxyl group-containing polymer (C) were blended in the amounts shown in Table 1, and the resin content was diluted to 50% by weight with butyl acetate to form a coating composition. The coating was applied to a tin plate using an applicator to a dry film thickness of 30 μm, and the test piece was left for 7 minutes in a coating environment of 20±5°C and a relative humidity of 78% or less. Comparative Example 4 is an example in which no siloxane group-containing polymer was blended. Table 1 also lists the weight ratio of the siloxane group-containing polymer (A) to the hydroxyl group-containing polymer (C) (siloxane group-containing polymer (A):hydroxyl group-containing polymer (C)).

[0086] The coating was then dried and heat-cured for 30 minutes at 140°C using a hot air dryer to obtain a test piece having a substrate and a coating film. The composition, various physical properties, and evaluation results of the obtained coating film are shown in Table 1.

[0087] The performance of the resulting coating films was evaluated by the method described below, and the results are shown in Table 2. In addition, transmission electron microscope (TEM) photographs were taken of some of the resulting coating films (Examples 1, 3, 4, 5, and 9), and are shown in Figure 1. TEM photographs were also taken for Example 10 and Comparative Examples 1 to 3, but no microseparated structure was confirmed, so the photographs are not shown. In addition, the coating films of Comparative Examples 1 to 3 became cloudy.

[0088] [Paint film transparency] The surface of the coating was visually observed and evaluated according to the following criteria. ○: The coating is transparent and no abnormalities are observed. △: The coating film is slightly milky white. ×: Cloudiness is observed in the coating film

[0089] [Removal of oil-based organic contaminants] Pine resin, terpineol, and limonene were added to carbon black (furnace black (KREMER pigments)) and stirred in a disperser to obtain a black, tar-like liquid. This was used as the oil-based organic contaminant. Using an applicator, this was applied onto the coating film obtained in the example so that the dry film thickness would be approximately 20 μm, and the film was dried in a hot air dryer at 80°C for 30 minutes, and evaluated under the following conditions. High-pressure water spray conditions: spray nozzle (1 / 4 PMEG-2506), water flow (11 L / min), water temperature (50°C), cleaning time (1 minute), water spray distance (10 cm) ○...The dirt is blown away at the same time as the water is sprayed, and there is no black dirt on the paint film where it was blown away. ×...The dirt does not blow off completely. Black dirt remains on the painted surface.

[0090] This test is a method for evaluating the degree of adhesion and ease of removal of oily organic contaminants, and is a substitute test for the removability of oily contaminants from the perspective of how easily the contaminants can be removed.

[0091] [Water stain removal] Evian (trade name) was sprayed onto the coating film obtained in the examples using an atomizer, and water droplets were placed on the coating film. This was dried in a hot air dryer at 60°C for 10 minutes to allow the scale to adhere to the coating film. The coating film was washed 10 times with a sponge under running tap water, and the scale remaining on the coating film was then visually evaluated. ◎…No hardened limescale ○: Most of the limescale has been removed. Only small dots remain. ×...Scale is stuck in a ring shape like a coffee ring (poor appearance).

[0092] [Contact angle and water repellency evaluation] Using a Kyowa Interface Science Co., Ltd. DMo-701 contact angle meter, approximately 1 μL of distilled water was deposited on the coating surface in an atmosphere of 25°C and 55% RH, and the angle between the droplet and the coating surface after 10 seconds was calculated using the θ / 2 method. ◎...Contact angle is 95 degrees or more, ○...Contact angle is 85 degrees or more, ×...Contact angle is less than 85 degrees.

[0093] [Contact angle and water repellency evaluation after polishing] Assuming a car wash, the coating was polished with a compound (#7500) using an electric polisher for 10 seconds, then washed with ion-exchanged water using a neutral detergent, and then dried at room temperature to prepare the coating for measurement. Using a Kyowa Interface Science Co., Ltd. DMo-701 contact angle meter, approximately 1 μL of distilled water was deposited on the coating surface in an atmosphere of 25°C and 55% RH, and the angle between the droplet and the coating surface after 10 seconds was calculated using the θ / 2 method. ◎...Contact angle is 95 degrees or more, ○...Contact angle is 85 degrees or more, ×...Contact angle is less than 85 degrees.

[0094] [Solvent resistance test] 2 μl of toluene was dropped onto the resulting coating film and allowed to stand for 5 minutes. After 5 minutes, the film was wiped off with a dry cloth and the appearance was evaluated according to the following criteria. ◯: No abnormalities were observed in the appearance of the coating film. △...A faint trace of droplets remains.

[0095] [Table 1]

[0096] [Table 2]

[0097] As is clear from Table 2, the paints of the examples have high paint film transparency and excellent water repellency (water repellency and ability to remove oil-based organic pollutants). Comparative Example 1 is an example in which a hydroxyl group-containing vinyl monomer is not blended with a siloxane group-containing vinyl polymer, resulting in poor compatibility and poor paint film transparency. Comparative Example 2 is an example of random polymerization rather than block polymerization, and also results in poor paint film transparency. Comparative Example 3 is an example of random polymerization with a high molecular weight distribution (Mw / Mn), and also results in poor paint film transparency. Comparative Example 4, as mentioned above, is an example in which a siloxane group-containing polymer is not blended, and results in poor water repellency.

Claims

1. A coating composition comprising a siloxane group-containing polymer (A), a crosslinking agent (B), and a hydroxyl group-containing polymer (C), the siloxane group-containing polymer (A) is a block copolymer comprising an A block and a B block, the A block comprising at least a structural unit derived from a siloxane group-containing vinyl monomer (a), the B block comprising a structural unit derived from a hydroxyl group-containing vinyl monomer (b) and, if necessary, a structural unit derived from another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b); and the copolymer has a molecular weight distribution (Mw / Mn) of 2.0 or less and is polymerized by living radical polymerization. The living radical polymerization is carried out by the following formula (1): 【Chemistry 1】 (In the formula, R 1 represents a C 1 to C 8 alkyl group, an aryl group, a substituted aryl group, or an aromatic heterocyclic group. R 2 and R 3 represent a hydrogen atom or a C 1 to C 8 alkyl group. R 4 represents an aryl group, a substituted aryl group, an aromatic heterocyclic group, an acyl group, an oxycarbonyl group, or a cyano group.) This is a method for polymerizing an organotellurium compound represented by the formula: Paint composition.

2. 2. The coating composition according to claim 1, wherein the siloxane group-containing polymer (A) is an AB diblock copolymer or an ABA triblock copolymer.

3. 3. The coating composition according to claim 1, wherein the weight average molecular weight (Mw) of the siloxane group-containing polymer (A) is 5,000 to 100,000.

4. 4. The coating composition according to claim 1, wherein the siloxane group-containing polymer (A) and the hydroxyl group-containing polymer (C) are blended in a weight ratio of siloxane group-containing polymer (A):hydroxyl group-containing polymer (C) of 15:85 to 80:

20.

5. 5. The coating composition according to claim 1, wherein the siloxane group-containing vinyl monomer (a) has a number average molecular weight (Mn) of 500 to 50,000.

6. The coating composition according to any one of claims 1 to 5, wherein the crosslinking agent (B) is an isocyanate-based crosslinking agent.

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