Coating components

Abstract

To provide a coating composition capable of providing a coating film having water repellency and to which water stains are hardly adhered.SOLUTION: There is provided a composition for a coating material which comprises a siloxane group-containing polymer (A) and a crosslinking agent (B), wherein the siloxane group-containing polymer (A) is a block copolymer containing a block A and a block B and is a copolymer polymerized by living radical polymerization which contains at least a structural unit derived from a siloxane group-containing vinyl monomer (a) in the block A and contains a structural unit derived from a hydroxyl group-containing vinyl monomer (b) in the block B and a structural unit derived from another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b) as needed and has a molecular weight distribution (Mw / Mn) of 2.0 or less and the dynamic glass transition temperature under the conditions of a temperature increase rate of 2°C / min and a frequency of 8 Hz during curing is 100 to 300°C.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] There is a growing desire for car surfaces to be "wash-free," meaning they can be kept clean by rainwater without the need for washing. Two technologies exist to achieve this: one makes the surface hydrophilic so that rainwater washes away dirt, and the other makes it hydrophobic so that water droplets are blown off along with the dirt while driving. However, for luxury cars and other vehicles, a hydrophobic appearance that repels water well tends to be preferred by people.

[0003] To make a paint film surface water-repellent, fluorine-based or silicone-based materials are often used as water-repellent materials. Fluorine-based materials have high water repellency and are effective, but at present they are expensive and difficult to use in general-purpose paints, and there are also problems such as environmental pollution, so their use is not easy. Silicone-based materials have the advantage of being easy to use in general applications, so their development is ahead. For example, Japanese Patent Publication No. 11-293184 (Patent Document 1) proposes a polymer composition using a siloxane macromonomer having unsaturated bonds at both ends. However, while the polymer composition in Patent Document 1 has sufficient antifouling function against general mud and carbon stains such as soot, water stains from tap water used during car washing, or water stains from muddy water containing many minerals, adhere to the paint film by penetrating it, and once they adhere, they cannot be easily removed. It has been found that mud and carbon stains get caught on paint films to which such water stains have adhered, making them difficult to remove. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-293184 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present inventors aim to provide a coating composition that is water-repellent, allows for easy removal of dirt, and provides a coating film that is resistant to limescale, which is caused by solidified mineral components in water that, once fixed, are difficult to remove. [Means for solving the problem]

[0006] In other words, the present invention is [1] A paint 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, 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, optionally, structural units derived from other vinyl monomers (c) copolymerizable with the vinyl monomers (a) and (b). The molecular weight distribution (Mw / Mn) is 2.0 or less, and the copolymer is polymerized by living radical polymerization, and During curing, under conditions of a heating rate of 2°C / min and a frequency of 8Hz, the dynamic glass transition temperature is 100-300°C. The present invention provides a paint composition. Furthermore, the present invention provides the following embodiments:

[0007] [2] The paint composition according to [1], wherein the siloxane group-containing polymer (A) is an AB-type diblock copolymer or an ABA-type triblock copolymer. [3] The paint 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 described above is performed by the following formula (1): [ka] [In the formula, R 1R represents a C1-C8 alkyl group, aryl group, substituted aryl group, or aromatic heterocyclic group. 2 and R 3 R represents a hydrogen atom or a C1-C8 alkyl group. 4 This represents an aryl group, a substituted aryl group, an aromatic heterocyclic group, an acyl group, an oxycarbonyl group, or a cyano group. A paint composition according to any one of [1] to [3], wherein polymerization is carried out using an organic tellurium compound represented by [1]. [5] The paint composition according to any one of [1] to [4], wherein the siloxane group-containing polymer (A) is a (meth)acrylic copolymer. [6] The paint composition according to any one of [1] to [5], wherein the copolymerizable other vinyl monomer (c) is an alicyclic hydrocarbon group-containing (meth)acrylate. [7] A paint composition according to any one of [1] to [6], further comprising a hydroxyl group-containing polymer (C). [8] A paint composition according to any one of [1] to [7], wherein the blending ratio of the siloxane group-containing polymer (A) and the hydroxyl group-containing polymer (C) is 15:85 to 80:20 by weight ratio of siloxane group-containing polymer (A) to hydroxyl group-containing polymer (C). [9] The paint composition according to any one of [1] to [8], wherein the number average molecular weight (Mn) of the siloxane group-containing vinyl monomer (a) is 500 to 50,000.

[10] The paint composition according to any one of [1] to [9], wherein the crosslinking agent (B) is a combination of an alicyclic polyisocyanate (B-1) and an aliphatic polyisocyanate (B-2). [Effects of the Invention]

[0008] In this invention, water repellency can be imparted to a coating film by incorporating a siloxane group-containing polymer. Since the siloxane group-containing polymer is firmly incorporated into the coating film through a crosslinking reaction, it does not separate or bleed, and the water-repellent performance can be maintained stably 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. As a result, the functions of each portion are exerted without interference from other portions, and the fixation function of the crosslinking portion and the function of the polysiloxane portion for water repellency can be clearly and for a long period of time. Consequently, water repellency can be achieved even with a small amount of siloxane group-containing polymer incorporated.

[0009] When a coating film formed from the paint composition of the present invention is present on a surface such as an automobile, its water repellency can be maintained stably and for a long period of time, so rainwater and other liquids turn into droplets (bead-shaped droplets) and are scattered when the vehicle is driven. Therefore, dirt such as dust present on the coating film is removed from the coating film when it rains, as rainwater picks up the dirt and scatters it when the vehicle is driven. The siloxane portion also has oil-repellent properties, so the adhesion of oily substances is reduced, and oily stains are also reduced. Furthermore, by controlling the dynamic glass transition temperature (Tg) of the coating film formed from the paint composition of the present invention, the adhesion of water stains was greatly improved. Even if water droplets remain on the coating film and dry to form water stains, the coating film does not harden and physically adhere, so it is thought that dirt does not accumulate as a result of water stains.

[0010] Furthermore, when using the siloxane group-containing polymer (A) of the present invention, the siloxane group portion remains firmly in the coating film without separating or bleeding, so that its performance can be stably maintained for a long period of time. In addition, other properties of the coating film, such as tensile strength, tear strength, or abrasion resistance, are maintained without adverse effects, and these properties are also preserved at a high level. [Modes for carrying out the invention]

[0011] The composition for paint of the present invention contains a siloxane group-containing polymer (A) and a crosslinking agent (B), and may contain another hydroxyl group-containing polymer (C) as required. Each component will be described.

[0012] <Siloxane group-containing polymer (A)> The above siloxane group-containing polymer (A) is a block copolymer containing an A block and a B block. The A block contains at least a structural unit derived from a siloxane group-containing vinyl monomer (a), and the B block contains a hydroxyl group-containing vinyl monomer (b) and, if necessary, a structural unit derived from another vinyl monomer (c) copolymerizable with the above vinyl monomers (a) and (b). Moreover, the molecular weight distribution (Mw / Mn) is 2.0 or less, and it is a copolymer polymerized by living radical polymerization. The above siloxane group-containing polymer (A) preferably does not contain a fluorine group-containing group in the siloxane group-containing polymer (A). The above siloxane group-containing polymer (A) is preferably a (meth)acrylate copolymer. A (meth)acrylate copolymer is a copolymer having a structural unit derived from (meth)acrylate as a main component (50% by weight or more). The content of the structural unit derived from (meth)acrylate in the above siloxane group-containing polymer (A) is preferably 80% by weight or more, more preferably 90% by weight or more, based on 100% by weight of the siloxane group-containing polymer (A). Incidentally, the above siloxane group-containing polymer (A) may be composed only of a structural unit derived from a (meth)acrylic monomer. As used herein, the term "vinyl monomer" refers to a monomer having a carbon-carbon double bond capable of radical polymerization in the molecule. The term "structural unit derived from a vinyl monomer" refers to a structural unit in which the carbon-carbon double bond capable of radical polymerization of the vinyl monomer has polymerized to form a carbon-carbon single bond. "(Meth)acrylate" refers to "at least one of acrylate and methacrylate". The term "structural unit derived from (meth)acrylate" refers to a structural unit in which the carbon-carbon double bond capable of radical polymerization of (meth)acrylate has polymerized to form a carbon-carbon single bond. "(Meth)acrylic" refers to "at least one of acrylic and methacrylic".

[0013] The above 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 [Chemical formula] [In the formula, Me represents a methyl group, R 11 represents a hydrogen atom or a methyl group, R 12 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R 13 represents an alkyl group having 1 to 6 carbon atoms which may have an oxygen atom intervening, and n represents 0 or an integer of 1 or more.] is represented by. The siloxane group-containing vinyl monomer (a) of the above formula (I) is preferably a siloxane group (more specifically, a polysiloxane group)-containing (meth)acrylate which is a reaction product of an alcohol group at the terminal of a polysiloxane represented by the following formula II: [Chemical formula] In the above formula I, R 11 represents a hydrogen atom or a methyl group. In the above formulas I and II, R 12 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Me is a methyl group. R 13n is an alkyl group having 1 to 6 carbon atoms. n is 0 or an integer of 1 or more, and n is preferably 6 to 300.

[0014] The siloxane group-containing vinyl monomer (a) having the above formula (I) is more specifically available from Shin-Etsu Chemical Co., Ltd. (Modified Silicone Oil Series) and JNC Corporation (Sylaplane®), including Shin-Etsu Chemical's 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. Examples include [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 are trade names) manufactured by JNC Corporation. Furthermore, if the siloxane group-containing vinyl monomer is monofunctional, the functional group equivalent [g / mol] can be considered as the number average molecular weight (Mn) of the siloxane group-containing vinyl monomer (a) per mole of siloxane.

[0015] The functional group equivalent (g / mol) of the siloxane group-containing vinyl monomer (a) is preferably 500 to 50,000 g / mol, more preferably 600 to 3,000 g / mol, and particularly preferably 700 to 1,200 g / mol, from the viewpoint of polymerizability. In particular, it shows excellent compatibility at 700 to 1,200 g / mol. The above functional group is a vinyl group, and the siloxane group-containing vinyl monomer (a) is preferably monofunctional from the viewpoint of polymerizability.

[0016] The number-average molecular weight (Mn) 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, due to its release properties. In particular, it shows excellent compatibility at 700 to 1,200.

[0017] The hydroxyl group-containing vinyl monomer (b) described above is a vinyl monomer having a hydroxyl group in its molecule, and more specifically, a hydroxyl group-containing (meth)acrylate, which is a reaction product of an alkyl polyol and (meth)acrylic acid, is preferred. Examples of hydroxyl group-containing vinyl monomers (b) include, for example, hydroxyalkyl(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, and glycerin mono(meth)acrylate; and polyethylene glycol mono(meth)acrylates such as diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, tetraethylene glycol mono(meth)acrylate, hexaethylene glycol mono(meth)acrylate, and octaethylene glycol mono(meth)acrylate.

[0018] The other vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b) above may be any vinyl monomer copolymerizable with the vinyl monomers (a) and (b), specifically: Linear alkyl-containing (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, and n-octyl (meth)acrylate; Branched alkyl group-containing (meth)acrylates such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, and isooctyl (meth)acrylate; (Meth)acrylates containing monocyclic cyclic alkyl groups such as cyclohexyl (meth)acrylate, cyclohexyloxyalkyl (meth)acrylate, and t-butylcyclohexyloxyethyl (meth)acrylate; (meth)acrylates containing alicyclic hydrocarbon groups such as isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate; (Meth)acrylic acid, carboxyl group-containing monomers such as β-carboxyethyl acrylate and other acrylic acid dimer acids; Phosphate-containing (meth)acrylates such as polyethylene glycol mono(meth)acrylate phosphate esters, polypropylene glycol mono(meth)acrylate phosphates such as (propylene glycol monomethacrylate) phosphate, methylene(meth)acrylate phosphate, trimethylene(meth)acrylate phosphate, propylene(meth)acrylate phosphate, tetramethylene(meth)acrylate phosphate, and alkylene(meth)acrylate phosphates such as tetramethylene(meth)acrylate phosphate; Olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid, sulfonic acid group-containing monomers or their salts; Alkoxyalkyl(meth)acrylamide monomers such as methoxymethyl(meth)acrylamide, ethoxymethyl(meth)acrylamide, propoxymethyl(meth)acrylamide, isopropoxymethyl(meth)acrylamide, n-butoxymethyl(meth)acrylamide, isobutoxymethyl(meth)acrylamide, (meth)acrylamide monomers such as (meth)acryloylmorpholine, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, and (meth)acrylamide N-methylol(meth)acrylamide; Glycidyl (meth)acrylate, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, methyl vinyl ketone, styrene, α-methylstyrene, N-vinylcaprolactam, vinyl acetate, etc. These include (meth)acrylates containing alicyclic hydrocarbon groups, and (meth)acrylates containing cyclic alkyl groups having a polycyclic structure are particularly preferred from the viewpoint of balancing the physical properties of the coating film.

[0019] The above-mentioned 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 other vinyl monomers (c) copolymerizable with vinyl monomers (a) and (b). A certain amount of siloxane group-containing vinyl monomer (a) imparts water repellency to the coating film, but too much structural units derived from siloxane group-containing vinyl monomer (a) is undesirable as it adversely affects the coating film. A larger amount of structural units derived from hydroxyl group-containing vinyl monomer (b) is preferable because it can copolymerize at a greater number of 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), with a hydroxyl value of 30 to 250 mgKOH / g being preferred, and 70 to 170 mgKOH / g being particularly preferred. If the hydroxyl value is less than 30 mgKOH / g, the isocyanate groups may not react sufficiently, potentially resulting in a coating with low crosslinking density, and if the hydroxyl value is greater than 250 mgKOH / g, the water resistance of the coating may deteriorate.

[0020] The siloxane group-containing polymer (A) described above is a block copolymer comprising an A block and a B block, wherein 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). Preferably, the B block further contains structural units derived from another vinyl monomer (c) copolymerizable with vinyl monomers (a) and (b). Furthermore, the block copolymer is preferably an AB-type diblock copolymer or an ABA-type triblock copolymer. More specifically, the A block in the block copolymer contains structural units derived from a polysiloxane group-containing vinyl monomer (a), making it possible to impart water-repellent and oil-repellent properties to the coating film. The B block in the block copolymer contains structural units derived from a hydroxyl group-containing vinyl monomer (b), which can crosslink with a crosslinking agent (B) to form a three-dimensional network structure, thereby improving durability. In other words, because the hydroxyl group-containing vinyl monomer (b), which is reactive with the crosslinking agent, is not introduced into block A but concentrated in block B, it becomes possible to clearly distinguish the functions that each polymer block, A and B, performs.

[0021] Furthermore, if blocks A and B have different polarities or are incompatible with each other, or if a polymer compatible with either block A or block B is present, a microphase separation structure may be formed in the coating film. In particular, when a microphase separation structure is present in the coating film, the functions performed by each polymer block of blocks A and B are most clearly separated, resulting in superior functionality. The microphase separation structure can take the form of a sea-island (spherical) structure, a columnar (linear) structure, a lamellar structure, or a worm-like structure at a microscopic level, which can be confirmed by thin slicing of the coating film and taking transmission microscope images (TEM images).

[0022] Polymers in which the above copolymer is randomly copolymerized rather than a block polymer may have difficulty exhibiting their functionality or, depending on the composition, may have poor compatibility due to the presence of structural units derived from polysiloxane group-containing vinyl monomer (a) and structural units derived from hydroxyl group-containing vinyl monomer (b) that are reactive with the crosslinking agent.

[0023] As a method for producing the AB-type diblock copolymer of the siloxane group-containing polymer (A) of the present invention, the A block may be produced first and the monomer of the B block may be polymerized onto the A block; the B block may be produced first and the monomer of the A block may be polymerized onto the B block; or the A block and the B block may be produced separately and then coupled together.

[0024] For example, it can be obtained by sequentially polymerizing the vinyl monomers that make up the block using a radical polymerization method. Specifically, a manufacturing method can be described as comprising the steps of polymerizing the vinyl monomers that make up one of the blocks A and B to polymerize one block, and after polymerizing one block, polymerizing the vinyl monomers that make up the other block A and B to polymerize the other block.

[0025] The effects of the present invention are difficult to obtain when using (meth)acrylic polymers obtained by conventional radical polymerization (free radical polymerization: FRP). In free radical polymerization, radical species are continuously generated during the reaction and added to the vinyl monomer, and polymerization proceeds. Therefore, in free radical polymerization, polymers are produced in which terminal radicals are deactivated during the reaction, or polymers are produced in which new radical species are generated during the reaction. Consequently, when a (meth)acrylic polymer containing a crosslinkable functional group is produced by free radical polymerization, a polymer is produced that does not contain structural units derived from a relatively low molecular weight vinyl monomer containing a crosslinkable functional group.

[0026] In crosslinkable (meth)acrylic polymers polymerized by free radical polymerization, the polymer composition is heterogeneous, and because it includes 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 heterogeneous composition can lead to the formation of homopolymers, for example, in which only siloxane-containing vinyl monomers are polymerized. This can worsen the compatibility of the resin and result in coating defects such as clouding and paint repellency.

[0027] Therefore, it is a copolymer polymerized by living radical polymerization. Living radical polymerization yields polymers with more uniform molecular weight and composition compared to free radical polymerization and the like, and suppresses the generation of low molecular weight components, making it less prone to bleed-out over time. Living radical polymerization methods include methods using transition metal catalysts (ATRP method), methods using sulfur-based reversible chain transfer agents (RAFT method), and methods using organotellurium compounds (TERP method), depending on the method used to stabilize the polymerization growth ends. The ATRP method uses amine-based complexes, so it may not be usable unless the acidic groups of vinyl monomers with acidic groups are protected. The RAFT method, when using various monomers, does not easily produce a low molecular weight distribution, and may have problems such as sulfurous odor and discoloration. Among these methods, the TERP method is preferred from the viewpoint of the diversity of monomers that can be used, molecular weight control in the high molecular weight range, uniform composition, and discoloration. The TERP method is a method for polymerizing radical polymerizable compounds (vinyl monomers) using an organotellurium compound as a chain transfer agent, and is described, for example, in International Publication Nos. 2004 / 14848, 2004 / 14962, 2004 / 072126, and 2004 / 096870.

[0028] As for the TERP method, a polymerization method using an organic tellurium compound represented by the following formula (1) is preferred, and a polymerization method using a mixture of the organic tellurium compound represented by the following formula (1) and an organic diterlide compound represented by the following formula (2) is more preferred. The following equation (1): [ka] [In the formula, R 1 R represents a C1-C8 alkyl group, aryl group, substituted aryl group, or aromatic heterocyclic group. 2 and R 3 R represents a hydrogen atom or a C1-C8 alkyl group. 4 This 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 This is the same as above.

[0029] Specific examples of organotellurium compounds represented by formula (1) include ethyl-2-methyl-2-n-butylteranyl-propionate, ethyl-2-n-butylteranyl-propionate, (2-hydroxyethyl)-2-methyl-methylteranyl-propionate, and other organotellurium compounds described in International Publication Nos. 2004 / 14848, 2004 / 14962, 2004 / 072126, and 2004 / 096870. Specific examples of organoditerlide compounds represented by formula (2) include dimethylditerlide and dibutylditerlide.

[0030] The polymerization step involves mixing a vinyl monomer, an organic tellurium compound of general formula (1), and an organic diterlide compound of formula (2) in a container purged with an inert gas, for purposes such as promoting the reaction, controlling the molecular weight and molecular weight distribution, depending on the type of vinyl monomer. Examples of inert gases include nitrogen, argon, and helium. Argon and nitrogen are preferred. The amount of vinyl monomer used can be adjusted as appropriate depending on the desired properties of the copolymer.

[0031] Polymerization is usually carried out without a solvent, but organic solvents commonly used in radical polymerization may also be used. Examples of usable solvents 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 as appropriate, but 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 as appropriate depending on the molecular weight or molecular weight distribution of the resulting copolymer, but typically, stirring is performed at 0°C to 150°C for 1 minute to 100 hours. After the polymerization reaction is complete, the target copolymer can be separated from the reaction mixture by conventional separation and purification methods to remove the solvent used and any remaining vinyl monomer.

[0032] 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, and the composition of all polymers approaches uniformity. When such a crosslinkable (meth)acrylic polymer is crosslinked using a crosslinking agent, almost all polymers can participate in crosslinking between polymer chains.

[0033] The siloxane group-containing polymer (A) described above is obtained by copolymerizing a polysiloxane group-containing vinyl monomer (a), a hydroxyl group-containing vinyl monomer (b), and another unsaturated monomer (c) copolymerizable with these, as described above, and preferably has a number-average molecular weight (Mn) of 3,000 to 100,000, and more preferably has a molecular weight distribution (Mw / Mn) of 2.0 or less.

[0034] 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 prone to bleed-out and allowing the initial surface properties to be maintained over a long period. The weight-average molecular weight (Mw) of the siloxane group-containing polymer (A) is preferably 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 limit, bleeding is more likely to occur, while if they are higher than the upper limit, handling becomes difficult due to increased viscosity, and turbidity may occur.

[0035] When the molecular weight distribution (Mw / Mn) of the siloxane group-containing polymer (A) is 2.0 or less, the molecular weight distribution is sharp, resulting in good compatibility with the coating film and obtaining 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 this invention, the molecular weight distribution is determined by (weight-average molecular weight of the block copolymer (Mw)) / (number-average molecular weight of the block copolymer (Mn)). The smaller the Mw / Mn, the narrower the molecular weight distribution, resulting in a copolymer with uniform molecular weights, and the narrowest molecular weight distribution is achieved when the value is 1.0. Conversely, the larger the Mw / Mn, the more molecules with smaller or larger molecular weights are included compared to the molecular weight of the designed polymer, which can worsen compatibility. Molecules with too small a molecular weight may dissolve but cause coating film problems such as bleed-out, while molecules with too large a molecular weight may have poor solubility in other polymer resins, causing problems such as cloudy coating films.

[0036] <Crosslinking agent (B)> The crosslinking agent incorporated into the paint composition of the present invention is not particularly limited, but it is one that crosslinks with the hydroxyl groups present in the siloxane group-containing polymer (A), and polyisocyanate-based crosslinking agents are an example.

[0037] A polyisocyanate crosslinking agent is a compound having two or more isocyanate groups in one molecule. Examples of polyisocyanate crosslinking agents include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates. Polyisocyanate crosslinking agents may be used alone or in combination of two or more types.

[0038] Examples of aliphatic polyisocyanates used as crosslinking agents (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, and 2,6- Aliphatic diisocyanates such as diisocyanatomethylcaproate; for example, 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.

[0039] 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, methyl- Alicyclic diisocyanates such as 2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, 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.

[0040] Examples of aromatic aliphatic polyisocyanates include aromatic aliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0041] Examples of aromatic polyisocyanates include aromatic diisocyanates such as m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate, 2,4'- or 4,4'-diphenylmethanediisocyanate or mixtures thereof, 2,4- or 2,6-tolylenediisocyanate or mixtures thereof, 4,4'-toluidinediisocyanate, and 4,4'-diphenyletherdiisocyanate; 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.

[0042] The above-mentioned aromatic polyisocyanates may yellow due to ultraviolet light, which is undesirable from the viewpoint of weather resistance. Aliphatic polyisocyanates are preferred from the viewpoint of weather resistance, and alicyclic polyisocyanates may be used in combination as needed.

[0043] In the present invention, the crosslinking agent (B) is preferably a combination of an alicyclic polyisocyanate (B-1) and an aliphatic polyisocyanate (B-2) among the polyisocyanate crosslinking agents listed above. A specific example of the alicyclic polyisocyanate (B-1) is isophorone diisocyanate, and a specific example of the aliphatic polyisocyanate (B-2) is hexamethylene diisocyanate or pentamethylene diisocyanate. A combination of these is more preferable. With this combination, it becomes easier to control the range of the dynamic glass transition temperature. These polyisocyanate crosslinking agents may also be in the form of derivatives described below.

[0044] Furthermore, examples of derivatives of polyisocyanate crosslinking agents include dimers, trimers, biuret, allophanate, carbodiimide, uretodione, uretoimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), and crude TDI. In particular, biuret, allophanate, and isocyanurate are preferred, with isocyanurate being the most preferred from the viewpoint of balancing the physical properties of the coating film.

[0045] The above-mentioned polyisocyanate crosslinking agents are typically used after blocking the isocyanate groups 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 blocking agents include compounds having active hydrogen groups (e.g., alcohols, oximes, etc.). Examples of blocking agents that are preferably used include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenolcarbinol, and methylphenylcarbinol; cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono-2-ethylhexyl ether; polyether-type terminal diols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycolphenol; polyester-type terminal polyols 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 mixing ratio of the siloxane group-containing polymer (A) and the polyisocyanate-based crosslinking agent is preferably such that the ratio of isocyanate group equivalents of the polyisocyanate-based crosslinking agent to the hydroxyl group equivalents of the siloxane group-containing polymer (A) is 0.5 to 2.5, more preferably 0.9 to 1.5, from the viewpoint of curability of the coating film and stability of the composition. If the ratio of isocyanate group equivalents of the polyisocyanate-based crosslinking agent to the hydroxyl group equivalents of the siloxane group-containing polymer (A) is less than 0.5, the crosslinking ability will be insufficient, and if it is greater than 2.5, yellowing due to heat is likely to occur.

[0047] <Hydroxygroup-containing polymer (C)> The coating composition of the present invention may optionally contain a hydroxyl group-containing polymer (C). Examples of hydroxyl group-containing polymers (C) include acrylic resins, silicone acrylic resins, polyester resins, alkyd resins, silicone polyester resins, epoxy resins, epoxy ester resins, and fluororesins, but among these, acrylic resins, polyester resins, alkyd resins, epoxy resins, and epoxy ester resins can be suitably used. Due to the ease of controlling functional groups and manufacturing, acrylic resins containing hydroxyl groups (hereinafter sometimes referred to as "acrylic polyol resins") are preferred as the hydroxyl group-containing polymer (C).

[0048] Acrylic polyol resins can be prepared using one or more unsaturated monomers commonly used in the preparation of acrylic resins, such as (meth)acrylic monomers, hydroxyl group-containing acrylic monomers, and other copolymerizable monomers.

[0049] The above (meth)acrylic monomers are not particularly limited and include, for example, 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.

[0050] As the hydroxyl group-containing acrylic monomer, the same one used in the hydroxyl group-containing vinyl monomer (b) used in the synthesis of the siloxane group-containing polymer (A) described above is preferably used. Furthermore, other copolymerizable monomers include monomers that copolymerize with acrylic monomers, such as styrenes like styrene and α-methylstyrene; and vinyl compounds such as vinyl acetate.

[0051] The method for producing the above-mentioned acrylic polyol resin is not particularly limited and can be carried out by, for example, solution polymerization such as conventional radical polymerization.

[0052] The acrylic polyol resin described above 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 paint composition and the properties of the resulting coating film, such as weather resistance.

[0053] The quantitative ratio of siloxane group-containing polymer (A) to hydroxyl group-containing polymer (C) is preferably 15:85 to 80:20 by weight ratio of siloxane group-containing polymer (A) to hydroxyl group-containing polymer (C). When the ratio is within this range, microphase separation can be controlled by the compatibility of the hydroxyl group-containing polymer (C) with the siloxane group-containing polymer (A) that forms a microphase separation structure. This allows for efficient imparting of antifouling functions such as water and oil repellency to the coating film by structural units derived from the polysiloxane group-containing vinyl monomer (a) of the polymer block of chain A. The weight ratio of siloxane group-containing polymer (A) to hydroxyl group-containing polymer (C) is preferably 20:80 to 75:25, more preferably 30:70 to 60:40.

[0054] <Paint composition> The coating composition of the present invention can be prepared by mixing the components constituting the above coating composition by commonly used means. The above coating composition may optionally contain pigments, surface modifiers (such as defoamers and leveling agents), 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.

[0055] The coating composition of the present invention is cured after being applied to a substrate, preferably at 70 to 170°C, more preferably at 70 to 160°C, and even more preferably at 70 to 150°C.

[0056] The coating composition of the present invention requires that the dynamic glass transition temperature during curing, under conditions of a heating rate of 2°C / min and a frequency of 8Hz, be 100°C to 300°C, preferably 110°C to 250°C, and more preferably 120°C to 150°C. When the dynamic glass transition temperature (dynamic Tg) is within this temperature range, it is possible to suppress the penetration and adhesion of water stains to the coating film when water stains form. Therefore, even in situations where dirt accumulates further, it is possible to suppress the accumulation of dirt triggered by water stains.

[0057] The dynamic glass transition temperature (dynamic Tg) is determined by first applying a paint composition to a polypropylene test plate using an air spray to achieve a single-layer dry film thickness of 30 μm, and then heating and curing it at 140°C for 30 minutes to form a coating film. Next, the coating film is peeled from the test plate and cut into 5 mm × 20 mm pieces to form test specimens. Dynamic viscoelasticity measurements are performed on these specimens using a forced-stretch vibration type viscoelasticity measuring device (Orientec's "Vibron"). Under conditions of a heating rate of 2°C / min and a measurement frequency of 8 Hz, the -20°C loss tangent tanδ is determined from the phase difference between the stress generated during heating and the vibration strain. The dynamic Tg of the coating film is defined as the temperature at which the loss tangent tanδ shows its maximum value. The "loss tangent tanδ" is a value measured in accordance with the tensile vibration-non-resonant method of JIS-K7244-4:1999.

[0058] <Object to be coated> Examples of materials to which the coating composition of the present invention is applied include steel plates made of metals such as iron, steel, stainless steel, aluminum, copper, zinc, and tin, and alloys thereof; resins such as ethylene vinyl acetate (EVA) resin, polyolefin resin (polyethylene resin, polypropylene resin, etc.), vinyl chloride resin, styrene resin, polyester resin (including polyethylene terephthalate (PET) resin, polybutylene terephthalate (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, polyphenylene oxide (PPO), etc.; and organic-inorganic hybrid materials. These may be in a molded state. The paint composition of the present invention is particularly effective with materials that are prone to static charge, such as polyolefin resins (polyethylene resin, polypropylene resin, etc.), styrene resins, polyester resins (including PET resin, PBT resin, etc.), and polycarbonate resins, as well as with unsaturated polyester resins used in fiber reinforced plastics (FRP) and carbon fiber reinforced plastics (CFRP).

[0059] The painting and / or coating of the paint composition of the present invention is not particularly limited and can be painted or coated by commonly used painting or coating methods. For example, when painting the paint composition of the present invention onto an automobile body, in order to improve the appearance of the resulting coating film, a multi-stage painting method using air electrostatic spray painting, preferably in two stages, or a painting method combining air electrostatic spray painting with a rotary atomizing electrostatic coating machine commonly known as "μμ (micro) bell," "μ (micro) bell," or "meta bell" can be used. When coating onto a film or the like, methods such as roll coating, kiss roll coating, gravure coating, bar coating, knife coating, curtain coating, lip coating, or extrusion coating using a die coater can be used. Furthermore, hand painting or brush painting using fibers impregnated with the paint composition of the present invention is also possible. For example, an appropriate amount can be impregnated into a dry sponge or cloth, and this can be spread thinly on the surface of the substrate by hand, forming a coating film by natural drying or forced drying using a dryer.

[0060] The film thickness of the coating film formed from the coating composition of the present invention is preferably 0.5 μm to 50 μm as a dry film thickness, and more preferably 1 μm to 30 μm. [Examples]

[0061] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[0062] [Manufacturing of copolymers] Manufacturing Example 1: Production of Siloxane Group-Containing Polymer (A-1) In a flask equipped with an argon gas inlet tube and a stirring blade, 1.49 g of ethyl-2-methyl-2-n-butylteranyl propionate (BTEE), 0.92 g of dibutyl diterlide (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 were charged (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize block B.

[0063] A mixed solution (second monomer composition) of 60.0 g of polysiloxane group-containing acrylic monomer (Shin-Etsu Chemical Co., Ltd.: X-22-174ASX [functional group equivalent (g / mol): 900] [number average molecular weight: 900]: abbreviated as "PDMSA" in Table 1), 0.33 g of 2,2'-azobis(isobutyronitrile), and 60 g of butyl acetate, which had been pre-substituted with argon, was added to the above reaction solution, and the mixture was polymerized by reacting at 60°C for 36 hours. The physical properties of the obtained siloxane group-containing polymer (A-1) from blocks AB are shown in Table 1. Table 1 lists the monomer content, molecular weight (weight average molecular weight), molecular weight distribution (Mn / Mw), hydroxyl value, and manufacturing method (TERP / FRP) of the siloxane group-containing polymer (A-1).

[0064] Manufacturing Example 2: Production of Siloxane Group-Containing Polymer (A-2) In a flask equipped with an argon gas inlet tube and a stirring blade, 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 78 g of dicyclopentanyl methacrylate (DCPMA), 0.33 g of AIBN, and 120 g of butyl acetate were charged (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize block B.

[0065] A mixed solution (second monomer composition) of 60.0 g of polysiloxane group-containing acrylic monomer (Shin-Etsu Chemical Co., Ltd.: X-22-174ASX [functional group equivalent (g / mol)]: 900 [number average molecular weight: 900]: abbreviated as "PDMSA" in Table 1), 0.33 g of 2,2'-azobis(isobutyronitrile), and 60 g of butyl acetate, which had been pre-substituted with argon, was added to the above reaction solution, and the mixture was polymerized by reacting at 60°C for 36 hours. The physical properties of the obtained siloxane group-containing polymer (A-1) of blocks AB are shown in Table 1. Table 1 lists the monomer content, molecular weight (weight average molecular weight), molecular weight distribution (Mn / Mw), hydroxyl value, and manufacturing method (TERP / FRP) of the siloxane group-containing polymer (A-1).

[0066] Manufacturing Example 3: Production of Siloxane Group-Containing Polymer (A-3) In a flask equipped with an argon gas inlet tube and a stirring blade, 1.49 g of BTEE, 0.92 g of DBDT, 42 g of HEMA, 78 g of isobornyl methacrylate (IBXMA), 0.33 g of AIBN, and 120 g of butyl acetate were charged (first monomer composition), and the mixture was reacted at 60°C for 36 hours to polymerize block B.

[0067] A mixed solution (second monomer composition) of 60.0 g of polysiloxane group-containing acrylic monomer (Shin-Etsu Chemical Co., Ltd.: X-22-174ASX [functional group equivalent (g / mol)]: 900 [number average molecular weight: 900]: abbreviated as "PDMSA" in Table 1), 0.33 g of 2,2'-azobis(isobutyronitrile), and 60 g of butyl acetate, which had been pre-substituted with argon, was added to the above reaction solution, and the mixture was reacted at 60°C for 36 hours to polymerize block A. The physical properties of the siloxane group-containing polymer (A-3) obtained from blocks AB are shown in Table 1. Table 1 lists the monomer content, molecular weight (weight average molecular weight), molecular weight distribution (Mn / Mw), hydroxyl value, and manufacturing method (TERP / FRP) of the siloxane group-containing polymer (A-3).

[0068] Production of hydroxyl group-containing polymer (C-1) 444.27 g of butyl acetate was placed in a 2 L separable flask equipped with a temperature controller, stirring blade, reflux tubing, and nitrogen inlet. The flask was then subjected to a nitrogen atmosphere, and the temperature was raised to 130°C and maintained at a constant 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 kaya ester O was placed in a dropping funnel and added dropwise over 3 hours.

[0069] Next, after continuing the reaction for 1 hour, a mixture of 204 g of butyl acetate and 20.4 g of kaya ester O was added dropwise over 30 minutes as a post-initiator, and the reaction was continued for another hour. Dilution with butyl acetate was then performed to obtain hydroxyl group-containing polymer (C-1) with a solid content of 60%. Table 1 shows the weight-average molecular weight (Mw), molecular weight distribution (Mw / Mn), hydroxyl value, and manufacturing method (TERP / FRP) of hydroxyl group-containing polymer (C).

[0070] (Examples 1-9 and Comparative Examples 1-3) Preparation of coating compositions and coating films A coating composition was prepared by blending a siloxane group-containing polymer (A) (any of A-1 to A-3), either or both of Z4470 (manufactured by Covestro, NCO%=11.8) having an IPDI isocyanurate structure or N3600 (manufactured by Covestro, NCO%=23) having an HDI isocyanurate structure as a crosslinking agent (B), and a hydroxyl group-containing polymer (C-1) in the amounts listed in Table 1. The resin content was diluted to 50% by mass with butyl acetate, and the coating composition was applied to a tin plate using an applicator to achieve a dry film thickness of 30 μm. The test specimens were left for 7 minutes in a coating environment with a temperature of 20±5°C and a relative humidity of 78% or less. Comparative Examples 2 and 3 are examples that do not contain a siloxane group-containing polymer.

[0071] Next, the substrate and coating were dried and heat-cured for 30 minutes at 140°C using a hot air dryer to obtain test specimens. The formulation and dynamic glass transition temperature (dynamic Tg) of the obtained coating are shown in Table 1.

[0072] [Measurement of dynamic Tg] The obtained coating composition was applied to a polypropylene test plate using an air spray to achieve a single-film dry thickness of 30 μm, and then heated and cured at 140°C for 30 minutes to form a coating film. Next, the coating film was peeled off the test plate and cut into 5 mm × 20 mm pieces to form test specimens. Dynamic viscoelasticity measurements were performed on these specimens using a forced-stretch vibration viscoelasticity measuring device (Orientec's "Vibron"). Under conditions of a heating rate of 2°C / min and a measurement frequency of 8 Hz, the -20°C loss tangent tanδ was determined from the phase difference between the stress and vibration strain generated during heating. The dynamic Tg of the coating film was defined as the temperature at which the loss tangent tanδ showed its maximum value. "Loss tangent tanδ" is a value measured in accordance with the tensile vibration-non-resonant method of JIS-K7244-4:1999. The obtained values ​​are listed in Table 1.

[0073] [Table 1]

[0074] The performance of the obtained coating film was evaluated using the method described below, and the results are shown in Table 2.

[0075] [Scale Test (Scale removal performance after 60*20 mins)] Hard water (product name: Evian) was sprayed onto the coating obtained in the example or comparative example from a spray bottle at a distance of approximately 20 cm from the coated plate, ensuring that droplets were evenly distributed on the plate. This was then dried in a hot air dryer at 60°C for 10 minutes to allow the limescale to adhere to the coating. The coating was then washed 10 times back and forth with a sponge while rinsing it with tap water, and the remaining limescale on the coating was visually inspected. ◎...No limescale buildup ○...Most of the limescale has been removed. Only tiny dots remain. ×...The limescale has hardened into a ring-like structure, similar to a coffee ring. (Not suitable for viewing.)

[0076] [Scale Test (Scale removal performance after 80°C * 10 min)] 80°C is the temperature of the hood of a dark-colored car under the blazing summer sun, making this a test conducted in an extremely harsh environment. Hard water (product name: Evian) was sprayed onto the coating obtained in the example or comparative example from a spray bottle at a distance of approximately 20 cm from the coated plate, ensuring that droplets were evenly distributed on the plate. This was then dried in a hot air dryer at 60°C for 10 minutes to allow the limescale to adhere to the coating. The coating was then washed 10 times back and forth with a sponge while rinsing it with tap water, and the remaining limescale on the coating was visually inspected. ◎...No limescale buildup ○...Most of the limescale has been removed. Only tiny dots remain. ×...The limescale has hardened into a ring-like structure, similar to a coffee ring. (Not suitable for viewing.)

[0077] [Carbon test after limescale buildup] On the coating obtained in the examples or comparative examples, hard water (product name: Evian) was sprayed onto the coating plate from a distance of approximately 20 cm using a spray bottle, ensuring that droplets were evenly distributed on the plate. This was then dried in a hot air dryer at 80°C for 10 minutes to allow the water stains to adhere to the coating. These coating plates were then immersed 10 times vertically up and down in a 1 wt% carbon dispersion aqueous solution (carbon pigment, Orion Engineering Carbons FW-100), and dried again in a hot air dryer at 80°C for 10 minutes. While spraying pure water onto the coating plates with carbon stains, a flannel cloth was moved back and forth 10 times, and the degree of remaining carbon staining was visually assessed. ○...No carbon stains △...Scattered carbon stains remain. ×...Carbon deposits have adhered to areas where water stains remain, leaving behind visible dirt (not aesthetically pleasing).

[0078] [Contact angle and water repellency evaluation] Using a DMo-701 contact angle meter manufactured by Kyowa Interface Science Co., Ltd., approximately 1 μL of distilled water was dropped onto the coating surface under conditions 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 of 85 degrees or more, ×... Contact angle less than 85 degrees

[0079] [Cleaning ability for mud and dirt stains] Eleven types of JIS test dust and hard water (product name: Evian) were mixed in a ratio of 5:95 wt% to create a 5 wt% suspension of JIS test dust, which was used as the contaminant dispersion. This dispersion was sprayed onto the coated plate from a distance of approximately 20 cm using a spray bottle, ensuring that droplets were evenly distributed across the plate. This was then dried in a hot air dryer at 60°C for 10 minutes. The resulting test pieces with the contaminant droplets were then rinsed evenly with tap water for 30 seconds, and after washing twice with a sponge, the remaining contaminants on the coating were visually inspected. ○...No traces of dried water droplets remain, and no dirt is left on the paint film. ×...There is a slight amount of dirt attached.

[0080] [Bending test] A coating film was applied to a polypropylene board, cured, and then the coating film was peeled off. A bending test was then performed. The flexibility was evaluated according to the following criteria. ◎...No abnormalities were observed in the coating even after repeated bending. ○...Cracks appear in the paint film.

[0081] [Solvent resistance] Two μl of toluene was dropped onto the coating film and left to stand for five minutes. After five minutes, the appearance was evaluated according to the following criteria after wiping with a dry cloth. ◎...No abnormalities are observed in the appearance of the coating. ○...A faint trace of the liquid droplet remains.

[0082] [Table 2]

[0083] As is clear from Table 2, the coatings in the examples exhibit excellent water stain removal and water repellency. Comparative Example 1 is an example where the dynamic Tg of the coating film is less than 100 degrees, resulting in poor water stain performance. Comparative Example 2 does not contain siloxane group-containing polymer (A), resulting in poor water repellency and dirt removal performance. As mentioned above, Comparative Example 3 is an example where the dynamic Tg of the coating film is less than 100 degrees and does not contain siloxane group-containing polymer, resulting in poor water stain removal, water repellency, and dirt resistance.

Claims

1. A method for producing a paint composition by mixing a siloxane group-containing polymer (A) and a crosslinking agent (B), The siloxane group-containing polymer (A) is a block copolymer comprising block A and block B, wherein block A contains at least structural units derived from a siloxane group-containing vinyl monomer (a), and block B contains structural units derived from a hydroxyl group-containing vinyl monomer (b). The siloxane group-containing polymer (A) has a molecular weight distribution (Mw / Mn) of 2.0 or less and is a copolymer polymerized by living radical polymerization. When the aforementioned coating composition hardens, the dynamic glass transition temperature under conditions of a heating rate of 2°C / min and a frequency of 8 Hz is 100 to 300°C. A method for producing a paint composition.

2. A method for producing a paint composition according to claim 1, wherein the siloxane group-containing polymer (A) is an AB-type diblock copolymer or an ABA-type triblock copolymer.

3. A method for producing a paint composition according to claim 1 or claim 2, wherein the weight-average molecular weight (Mw) of the siloxane group-containing polymer (A) is 5,000 to 100,000.

4. The aforementioned living radical polymerization is performed using the following formula (1): 【Chemistry 1】 [In the formula, R １ C １ ~C ８ R represents an alkyl group, aryl group, substituted aryl group, or aromatic heterocyclic group. ２ and R ３ is a hydrogen atom or C １ ~C ８ R indicates the alkyl group. ４ This represents an aryl group, a substituted aryl group, an aromatic heterocyclic group, an acyl group, an oxycarbonyl group, or a cyano group. A method for producing a paint composition according to any one of claims 1 to 3, wherein polymerization is performed using an organic tellurium compound represented by .

5. A method for producing a paint composition according to any one of claims 1 to 4, wherein the siloxane group-containing polymer (A) is a (meth)acrylic copolymer.

6. A method for producing a paint composition according to claim 1, wherein the siloxane group-containing polymer (A) is a block copolymer comprising an A block and a B block, the A block contains at least structural units derived from a siloxane group-containing vinyl monomer (a), the B block contains structural units derived from a hydroxyl group-containing vinyl monomer (b), and further contains structural units derived from another vinyl monomer (c) copolymerizable with the vinyl monomers (a) and (b).

7. A method for producing a paint composition according to claim 6, wherein the copolymerizable other vinyl monomer (c) is an alicyclic hydrocarbon group-containing (meth)acrylate.

8. Furthermore, a method for producing the paint composition according to any one of claims 1 to 6, comprising a hydroxyl group-containing polymer (C).

9. A method for producing a paint composition according to claim 8, wherein the blending ratio of the siloxane group-containing polymer (A) and the hydroxyl group-containing polymer (C) is 15:85 to 80:20 by weight ratio of siloxane group-containing polymer (A) to hydroxyl group-containing polymer (C).

10. A method for producing a paint composition according to claim 1 or 6, wherein the number average molecular weight (Mn) of the siloxane group-containing vinyl monomer (a) is 500 to 50,000.

11. A method for producing a paint composition according to any one of claims 1 to 10, wherein the crosslinking agent (B) is a combination of an alicyclic polyisocyanate (B-1) and an aliphatic polyisocyanate (B-2).

Images