Coating composition and coated article

Abstract

Provided is a coating composition including (i) an organopolysiloxane composed of the ratio of units represented in formula (1): (R1 3SiO1 / 2)a(R2 2SiO)b(R3 1SiO3 / 2)c(SiO2)d(OR4)e (where R1-R3 represent alkyl groups or the like that may be substituted with a hydrogen atom, one or more hydroxy groups, or the like, and that may have an ether bond, with at least a portion of the same being an alkyl group or the like that is substituted with a hydroxy group and that may have an ether bond, R4 represents a hydrogen atom or an alkyl group, and a is 0-0.5, b is 0-0.5, c is 0.2-1.0, d is 0-0.5, e is 0-3.0, and a+b+c+d=1 is satisfied), and (ii) an inorganic filler.

Description

Coating compositions and coated articles

[0001] The present invention relates to coating compositions and coated articles, and more particularly to flame-retardant coating compositions and coated articles for use on wood substrates.

[0002] In recent years, the use of wood in buildings has been promoted from the perspectives of carbon fixation and the effective use of domestic resources. However, wood is a flammable base material, and its use in applications requiring flame retardancy is severely limited. In this context, various technologies for imparting flame retardancy to wood have been investigated.

[0003] For example, Patent Document 1 successfully imparts flame retardancy by impregnating wood with a high concentration of a flame retardant such as boric acid. However, this system has the problem that the flame retardant adsorbed on the wood elutes or deliquesces due to moisture in the air, significantly impairing the aesthetic appearance.

[0004] Patent Document 2 reports that leaching of the chemicals can be suppressed by impregnating wood with a boron compound and then coating the wood surface with a siloxane compound. However, when using this method, it has been reported that the boron compound dissolves in the moisture contained in the wood itself, causing efflorescence at the interface between the coating film and the wood. In addition, this method requires many steps, such as impregnation with a flame retardant, drying, and surface coating, which inevitably increases manufacturing costs.

[0005] Patent Document 3 reports a technology for imparting flame retardancy to wood without impregnating the wood with a flame retardant by coating the wood surface with a primer component mainly composed of silica and then coating water glass on top of that. However, water glass has known problems such as low hardening and water resistance, and reacts with wood to cause discoloration, and there are many challenges to overcome before it can be put into practical use.

[0006] Furthermore, when coating wood surfaces, some of the coating liquid may be absorbed into the wood, causing powder additives such as pigments and fillers to segregate on the surface, resulting in poor appearance such as efflorescence and discoloration. This type of poor appearance is particularly likely to occur around knots where the fibers are sparse. Typically, an intermediate coating called a sealer is applied to prevent the paint from being absorbed into the wood. However, sealer coatings generally contain organic polymers to improve film-forming properties, which can worsen the wood's flame retardancy.

[0007] Japanese Patent No. 3538194 Japanese Patent No. 4367640 Japanese Patent Laid-Open No. 2018-115294

[0008] The present invention has been made in view of the above circumstances, and aims to provide a coating composition that can maintain the appearance of wood, such as wood grain, and can impart excellent flame retardancy and moisture resistance, and a coated article using the same.

[0009] As a result of extensive research into achieving the above-mentioned object, the present inventors discovered that the above-mentioned object can be achieved by using a coating composition containing a specific hydroxy group-modified organopolysiloxane and an inorganic filler, and thus completed the present invention.

[0010] That is, the present invention provides a composition comprising: 1. (i) 100 parts by mass of an organopolysiloxane having a unit ratio represented by the following formula (1), and (R 1 3SiO 1 / 2 ) a (R 2 2SiO) b (R 3 1SiO 3 / 2 ) c (SiO2) d (OR 4 ) e (1) (wherein, R 1 , R 2 and R 3each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with one or more amino groups, hydroxy groups, epoxy groups, acid anhydride groups, maleimide groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, or heterocyclic groups, and which may have an ether bond; 1 , R 2 and R 3 at least a part of which is an alkyl group having 1 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, an aryl group having 6 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, or an aralkyl group having 7 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, 4 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, a is 0 to 0.5, b is 0 to 0.5, c is 0.2 to 1.0, d is 0 to 0.5, and e is a number that satisfies the relationship a+b+c+d=1.) (ii) an inorganic filler: 100 to 900 parts by mass, 2. A coating composition comprising the R 1 , R 2 and R 3wherein the total number of hydroxy groups contained in (ii) is 50 mol % or more relative to the total number of silicon atoms in formula (1), 3. The coating composition according to 1 or 2, wherein the (ii) inorganic filler comprises one or more selected from silica, alumina, and phyllosilicate, 4. The coating composition according to any of 1 to 3, further comprising (iii) 10 to 300 parts by mass of one or more flame retardants selected from phosphorus-based, boron-based, magnesium-based, aluminum-based, nitrogen-based, antimony-based, and halogen-based compounds per 100 parts by mass of component (i), 5. The coating composition according to 4, wherein the ratio of the total mass of component (ii) and component (iii) to the mass of component (i), [(ii) + (iii)] / (i), is 2.0 to 9.0, 6. A cured product of the coating composition according to any of 1 to 5, 7. 7. A coated article having a coating layer formed on at least a portion of the surface of a wooden substrate, directly or via one or more other layers, comprising a coating film of the coating composition described in any one of 1 to 5; 8. A coated article having a topcoat layer formed on at least a portion of the surface of a wooden substrate, via an undercoat layer formed on at least a portion of the surface of the wooden substrate, comprising a coating film of a topcoat coating composition containing the following components (A), (B), and (C): (A) 100 parts by mass of an organopolysiloxane having a unit ratio represented by the following formula (2): (R 5 3SiO 1 / 2 ) f (R 6 2SiO) g (R 7 1SiO 3 / 2 ) h (SiO2) i (OR 8 ) j (2) (wherein, R 5 , R 6 and R 7 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with one or more amino groups, hydroxy groups, epoxy groups, acid anhydride groups, maleimide groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, or heterocyclic groups, and 5 , R 6 and R7 at least a part of which is an alkyl group having 1 to 20 carbon atoms substituted with an amino group, an aryl group having 6 to 20 carbon atoms substituted with an amino group, or an aralkyl group having 7 to 20 carbon atoms substituted with an amino group, 8 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, f is 0 to 0.5, g is 0 to 0.5, h is 0.2 to 1.0, i is 0 to 0.5, and j is a number that satisfies f+g+h+i=1.) (B) One or more flame retardants selected from phosphorus-based, boron-based, magnesium-based, aluminum-based, nitrogen-based, antimony-based, and halogen-based compounds: 50 to 300 parts by mass (C) Inorganic filler: 25 to 150 parts by mass 9. The coating amount of the primer layer is 0.01 to 0.50 kg / m2 of the wood substrate. 2 and the coating amount of the top coat layer is 0.1 to 2.0 kg / m2 relative to the wood substrate. 2 9. The coated article according to claim 8, wherein

[0011] When used as an undercoat for wood substrates, the coating composition of the present invention effectively coats the gaps between wood fibers with the organopolysiloxane and inorganic filler, thereby improving moisture resistance. Furthermore, by suppressing absorption of the topcoat into the surface of the wood substrate, it is possible to prevent deterioration of appearance, such as whitening around knots. Furthermore, by combining the composition with a topcoat containing an organopolysiloxane, a flame retardant, and an inorganic filler, the coating film ceramicizes during combustion, forming a fire-resistant and / or heat-insulating layer, thereby preventing combustion of the wood substrate. These effects enable the present invention to provide coated articles that maintain the appearance of wood substrates, such as wood grain, while also exhibiting excellent flame retardancy and moisture resistance, something that has previously been difficult to achieve. The coating composition of the present invention can impart flame retardancy to wood substrates by applying it to the surface of the wood substrate, making it easier to impart flame retardancy to wood substrates than conventional flame retardant impregnation methods. In addition, on-site application of the flame retardant is possible, which is expected to greatly expand the flexibility in the design and / or construction of wooden buildings.

[0012] The present invention will be described in detail below. [1] Coating composition The coating composition of the present invention contains the following components (i) and (ii): (i) an organopolysiloxane having a unit ratio represented by the following formula (1), and (ii) an inorganic filler.

[0013] (i) Organopolysiloxane Component (i) is an organopolysiloxane composed of units represented by the following formula (1): (R 1 3SiO 1 / 2 ) is the M unit, (R 2 2SiO) is a D unit, and (R 3 SiO 3 / 2 A unit represented by (SiO2) is called a T unit, and a unit represented by (SiO2) is called a Q unit.

[0014] (R 1 3SiO 1 / 2 ) a (R 2 2SiO) b (R 3 1SiO 3 / 2 ) c (SiO2) d (OR 4 ) e (1)

[0015] In formula (1), R 1 , R 2 and R 3 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with one or more amino groups, hydroxy groups, epoxy groups, acid anhydride groups, maleimide groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, or heterocyclic groups, and which may have an ether bond; 1 , R 2 and R 3At least a part of the above is an alkyl group having 1 to 20 carbon atoms and substituted with a hydroxy group and optionally having an ether bond, an aryl group having 6 to 20 carbon atoms and substituted with a hydroxy group and optionally having an ether bond, or an aralkyl group having 7 to 20 carbon atoms and substituted with a hydroxy group and optionally having an ether bond.

[0016] The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-decyl, cyclopentyl, and cyclohexyl groups. Methyl and ethyl groups are preferred in terms of enhancing the flame retardancy of the coating composition. Examples of aryl groups having 6 to 20 carbon atoms include phenyl and naphthyl groups. Examples of aralkyl groups having 7 to 20 carbon atoms include benzyl and phenethyl groups. Examples of heterocyclic groups include piperidinyl, pyridinyl, pyrrolyl, and thienyl groups.

[0017] As described above, in formula (1), R 1 , R 2 and R 3 at least a part of which is an alkyl group having 1 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, an aryl group having 6 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, or an aralkyl group having 7 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, and preferred examples of such a group substituted with a hydroxy group include a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 2,3-dihydroxypropyl group, a 3,4-dihydroxybutyl group, a β-(3,4-dihydroxycyclohexyl)ethyl group, and a group represented by the following formula (3):

[0018] (In the formula, the wavy line represents a bond.)

[0019] Considering the solubility of the component (i) in water, the affinity with the inorganic filler component and the substrate, etc., R1 , R 2 and R 3 The total number of hydroxy groups contained in the formula (1) is preferably 50 mol % or more, more preferably 80 mol % or more, and even more preferably 100 mol % or more, based on the total number of silicon atoms in the formula (1).

[0020] In addition, R 1 , R 2 and R 3 Among these, as the substituents other than the group substituted with a hydroxy group, a methyl group or an ethyl group, which has a small number of carbon atoms in the combustible alkyl chain, is preferred, and a methyl group is more preferred.

[0021] In formula (1), R 4 Each of R independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Specific examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, and n-octyl groups. Among these, from the viewpoint of flame retardancy of the coating composition, R 4 is preferably a hydrogen atom.

[0022] a is a number between 0 and 0.5, b is a number between 0 and 0.5, c is a number between 0.2 and 1.0, and d is a number between 0 and 0.5, and a + b + c + d = 1 is satisfied. e is a number between 0 and 3.0, and is preferably a number between 0.1 and 2.0 from the viewpoint of the water solubility of the organopolysiloxane. If e exceeds 3.0, the film-forming properties of the coating composition and the moisture resistance of the coating film may deteriorate.

[0023] The organopolysiloxane of component (i) has undergone a certain degree of condensation, which facilitates network formation and facilitates immobilization to the substrate. In addition, the organopolysiloxane contains fewer alkoxy groups, which are sources of flammable gas, than monomer components (such as silane coupling agents) that do not contain siloxane bonds (Si—O—Si bonds), which provides the advantage of less degradation in flame retardancy.

[0024] The amount of the monomer component not containing a siloxane bond is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and even more preferably 1% by mass or less, relative to the organopolysiloxane of component (i). The ratio of the monomer component not containing a siloxane bond to the organopolysiloxane component is as follows: 29 It can be determined from the signal and integral ratio in the Si-NMR (nuclear magnetic resonance) spectrum. 29 In Si-NMR, for example, in the case of a trifunctional siloxane (T unit), the number of silicon atoms forming the siloxane bond can be determined by examining the ratio of (T0) to (T3) shown below. The detected magnetic field generally increases in the order of T3 > T2 > T1 > T0, so the T0 component is a silicon atom derived from the silane coupling agent and the others are silicon atoms derived from the siloxane. Therefore, the ratio of the integral values ​​of each peak can be used to determine the ratio of the monomer (silane coupling agent) component to the organopolysiloxane component.

[0025] (In the formula, R represents an organic group, and X represents a hydrogen atom or an organic group.)

[0026] The organopolysiloxane of component (i) can be produced by hydrolysis and condensation of the monomer components of the respective structural units in the presence of an acid or base catalyst. Furthermore, by carrying out a deprotection reaction of the protected hydroxy groups as necessary, it is possible to produce an organopolysiloxane having alkyl groups, aryl groups, aralkyl groups, etc. substituted with hydroxy groups.

[0027] Examples of the monomer of the Q unit include tetramethoxysilane, tetraethoxysilane, tetra(n-propoxy)silane, tetra(i-propoxy)silane, tetra(n-butoxy)silane, alkali silicate, and activated silicic acid obtained by cation exchange of alkali silicate.

[0028] Examples of monomers for the T unit include methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3 ,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, perfluorooctylethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, γ-isocyanatepropyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane, and the like. Among these, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, etc. can be converted into hydroxy group-substituted products by transesterification with water, and γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc. can be converted into diol products by reacting the epoxy ring with water, which are preferred because they improve the solubility of the siloxane in water and the affinity with wood and inorganic filler components.

[0029] Examples of the monomer for the D unit include dimethyldimethoxysilane, dimethyldiethoxysilane, methylethyldimethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, diisopropyldimethoxysilane, phenylmethyldimethoxysilane, vinylmethyldimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. Among these, taking into consideration the solubility of the resulting siloxane in water and the affinity with wood and flame retardant components, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, and the like can be converted into hydroxy group-substituted products by transesterification with water, and γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, and the like can be converted into diol products by reacting the epoxy ring with water, which are preferred because they improve the solubility of the siloxane in water and the affinity with wood and inorganic filler components.

[0030] Examples of monomers for M units include trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, n-propyldimethylmethoxysilane, n-propyldiethylmethoxysilane, isopropyldimethylmethoxysilane, isopropyldiethylmethoxysilane, propyldimethylethoxysilane, n-butyldimethylmethoxysilane, n-butyldimethylethoxysilane, n-hexyldimethylmethoxysilane, n-hexyldimethylethoxysilane, n-pentyldimethylmethoxysilane, n-pentyldimethylethoxysilane, n-hexyldimethylmethoxysilane, and n-hexyldimethylethoxysilane. Examples thereof include dimethylethoxysilane, n-decyldimethylmethoxysilane, n-decyldimethylethoxysilane, trimethylsilanol, triethylsilanol, n-propyldimethylsilanol, n-propyldiethylsilanol, isopropyldimethylsilanol, isopropyldiethylsilanol, propyldimethylsilanol, n-butyldimethylsilanol, n-hexyldimethylsilanol, n-pentyldimethylsilanol, n-decyldimethylsilanol, γ-aminopropyldimethylmethoxysilane, and N-(2-aminoethyl)-3-aminopropyldimethylmethoxysilane. Among these, taking into consideration the solubility of the resulting organopolysiloxane in water and the affinity with the substrate and flame retardant components, γ-methacryloxypropyldimethylmethoxysilane, γ-methacryloxypropyldimethylethoxysilane, etc. can be converted into hydroxy group-substituted products by a transesterification reaction with water, and γ-glycidoxypropyldimethylmethoxysilane, γ-glycidoxypropyldimethylethoxysilane, β-(3,4-epoxycyclohexyl)ethyldimethylmethoxysilane, etc. can be converted into diol products by reacting the epoxy ring with water, and these are preferred because they improve the solubility of the siloxane in water and the affinity with wood and inorganic filler components.

[0031] Since the M units and D units have two or more Si-C bonds and are easily combustible, the content of M units and D units among all structural units in the organopolysiloxane of component (i) is each 50 mol % or less. That is, in the above formula (1), a is a number from 0 to 0.5, preferably a number from 0 to 0.2, and more preferably a number from 0 to 0.1. Furthermore, b is a number from 0 to 0.5, preferably a number from 0 to 0.2, and more preferably a number from 0 to 0.1.

[0032] Since T units have one Si-C bond and are less flammable than D and M units, the inclusion of 20 mol % or more of T units among all the structural units in the organopolysiloxane of component (i) results in good flame retardancy. That is, in the above formula (1), c is a number from 0.2 to 1.0, preferably a number from 0.5 to 1.0, and more preferably a number from 0.6 to 1.0.

[0033] The Q units do not contain Si-C bonds and have low flammability, and are effective in suppressing a decrease in flame retardancy due to combustion resulting from the Si-C bonds. On the other hand, because the Q units have many crosslinking points and are highly reactive, from the viewpoints of compatibility with the flame retardant component and film-forming properties, the Q units are in the range of 0 to 50 mol % of all constitutional units in the organopolysiloxane of component (i), i.e., d is a number from 0 to 0.5, and preferably a number from 0 to 0.4.

[0034] The ratio of each structural unit in component (i) is, for example, 29 This can be confirmed by a known method using the ratio of the chemical shift and integral value of the Si-NMR signal.

[0035] The content of component (i) is preferably 5 to 50 mass% and more preferably 10 to 30 mass% based on the total solid content of the coating composition. When it is 5 mass% or more, the film-forming properties and transparency of the coating film are good. When it is 50 mass% or less, the flame retardancy of the coating film and the effect of suppressing poor appearance around knots in the wood substrate are good. Component (i) may be used alone or in combination of two or more types.

[0036] (ii) Inorganic Filler: The inorganic filler of component (ii) can be a known, general inorganic filler, such as inorganic fillers containing Group 13 elements, Group 14 elements (excluding carbon), first-series transition elements, second-series transition elements, third-series transition elements, lanthanides, etc. Inorganic fillers containing Group 13 elements include oxides derived from aluminum, boron, indium, etc., with alumina being preferred. Inorganic fillers containing Group 14 elements (excluding carbon) include oxides and salts thereof derived from silicon, tin, etc., with silica being preferred. Inorganic fillers containing first-series transition elements include oxides derived from titanium, manganese, zinc, etc., and these oxides can also be used as light-absorbing materials at specific wavelengths. Inorganic fillers containing second-series transition elements include oxides derived from yttrium, zirconium, etc., and these oxides can also be used as light-absorbing and fluorescent materials at specific wavelengths. Inorganic fillers containing third-series transition elements include oxides derived from hafnium, tantalum, etc. Examples of inorganic fillers containing lanthanoids include oxides derived from lanthanum, cerium, praseodymium, neodymium, terbium, dysprosium, ytterbium, etc. These oxides can also be used as light absorbing and fluorescent materials with specific wavelengths. In addition, compounds of two or more of these oxides formed via chemical bonds can also be used.

[0037] The shape of the inorganic filler is not particularly limited, and inorganic fillers of various shapes such as spherical, hollow spherical, porous, plate-like, needle-like, and fibrous shapes can be used.

[0038] In particular, the inorganic filler used in the present invention is preferably an inorganic oxide or silicate containing elements such as silicon, boron, or aluminum, which becomes ceramic upon combustion and forms a fire-resistant or heat-insulating layer. Examples include silica, alumina, and phyllosilicates. In particular, it is preferable to use a silicon oxide-containing filler such as silica in combination with a phyllosilicate such as clay, as this improves flame retardancy and the effect of suppressing poor appearance around knots.

[0039] In particular, as the inorganic filler used in the present invention, silica particles having an average particle size calculated based on the BET specific surface area of ​​15 to 100 nm are preferably used, and silica particles having an average particle size of 20 to 80 nm are more preferably used. An average particle size of 15 nm or more results in excellent film-forming properties of the coating film, and an average particle size of 100 nm or less results in excellent transparency of the coating film.

[0040] The blending amount of component (ii) is 100 to 900 parts by mass, more preferably 200 to 800 parts by mass, per 100 parts by mass of the organopolysiloxane of component (i). At 100 parts by mass or more, the flame retardancy of the coating film is improved. For example, when the coating composition of the present invention is used as a primer layer on a wooden substrate and then a topcoat layer is formed on top of that, the inorganic filler fills the grain of the wood substrate surface, forming the primer layer, thereby suppressing absorption of the topcoat paint and preventing poor appearance around knots. At 900 parts by mass or less, the coating film formation is improved, resulting in good transparency of the coated article and improved suppression of poor appearance around knots. Component (ii) may be used alone or in combination of two or more types.

[0041] (iii) Flame Retardant The coating composition of the present invention may contain, as component (iii), one or more flame retardants selected from phosphorus-, boron-, magnesium-, aluminum-, nitrogen-, antimony-, and halogen-based compounds. Phosphorus-based compounds include, for example, organic phosphorus compounds, phosphoric acid, phosphate esters, and phosphate salts. Specific examples include diammonium hydrogen phosphate, ammonium dihydrogen phosphate, diguanidine phosphate, ammonium polyphosphate, hydrophobized ammonium polyphosphate, guanylurea phosphate, carbamate polyphosphate, and melamine phosphate. Boron-based compounds include, for example, organic boron compounds, boric acid, borax, boron oxide, borate esters, and borates. Magnesium-based compounds include, for example, magnesium hydroxide and magnesium oxide. Aluminum-based compounds include, for example, aluminum hydroxide. Nitrogen-based compounds include, for example, ammonium sulfate, ammonium carbonate, ammonium bicarbonate, and melamine cyanurate. Antimony-based compounds include, for example, antimony trioxide. Examples of halogen compounds include zinc chloride.

[0042] Among these, phosphorus-based compounds and boron-based compounds are preferred as flame retardants for use in the coating composition of the present invention, as they provide good transparency and flame retardancy of the coated article and good effects in suppressing poor appearance around knots in wood.Specific examples that can be suitably used include diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium polyphosphate, boric acid, borax, boron oxide, etc.

[0043] When component (iii) is used, the blending amount is preferably 10 to 300 parts by mass, and more preferably 50 to 200 parts by mass, per 100 parts by mass of the organopolysiloxane of component (i) above, from the viewpoint of the flame retardancy, film-forming ability, transparency, and moisture resistance of the coating film. Component (iii) may be used alone, or two or more types may be used in combination.

[0044] In the coating composition of the present invention, the ratio of the total mass of component (ii) and component (iii) to the mass of component (i), [(ii) + (iii)] / (i), is preferably 1.0 to 10.0, more preferably 2.0 to 9.0, and even more preferably 3.0 to 8.0. When this ratio is 1.0 or more, the flame retardancy is good, and when it is 10.0 or less, the moisture resistance, film-forming ability, and transparency of the coating film are good.

[0045] (iv) Solvent The coating composition of the present invention may contain a solvent in addition to the above components (i) to (iii). The solvent is not particularly limited, but alcohol or water is preferred, and water is more preferred from the viewpoints of environmental conservation and easy availability.

[0046] When water is used as the solvent, specific examples of fresh water that can be used include tap water, industrial water, well water, natural water, rainwater, distilled water, and ion-exchanged water, with ion-exchanged water being particularly preferred. Ion-exchanged water can be produced using a pure water maker (e.g., FW-10, manufactured by Organo Corporation, Direct-QUV3, manufactured by Merck Millipore, etc.).

[0047] When a solvent is used, the blending amount is preferably 20 to 98% by mass, more preferably 70 to 95% by mass, based on the total composition. When the solvent is contained in an amount of 20% by mass or more based on the total composition, the fluidity and workability of the paint are improved, and when the solvent is contained in an amount of 98% by mass or less based on the total composition, the concentration of the active ingredient in the paint is high, making it easier to thicken the paint film.

[0048] (v) Curing catalyst The coating composition of the present invention may contain a curing catalyst for the purpose of accelerating the curing reaction. The type, amount, and addition method of the curing catalyst can be determined by known methods and conditions depending on the type of composition. In particular, when the coating composition contains a component that cures by a chemical reaction in the presence of a catalyst, it is preferable that the coating composition contains a curing catalyst. Examples of the curing catalyst include basic compounds such as lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium methylate, sodium propionate, potassium propionate, sodium acetate, potassium acetate, sodium formate, potassium formate, trimethylbenzylammonium hydroxide, tetramethylammonium hydroxide, tetramethylammonium acetate, n-hexylamine, tributylamine, diazabicycloundecene (DBU), and dicyandiamide; metal-containing compounds such as tetraisopropyl titanate, tetrabutyl titanate, titanium acetylacetonate, aluminum triisobutoxide, aluminum triisopropoxide, tris(acetylacetonate)aluminum, diisopropoxy(ethylacetoacetate)aluminum, aluminum perchlorate, aluminum chloride, cobalt octylate, cobalt acetylacetonate, iron acetylacetonate, tin acetylacetonate, dibutyltin octylate, and dibutyltin laurate; and acidic compounds such as p-toluenesulfonic acid and trichloroacetic acid. Among these, sodium propionate, sodium acetate, sodium formate, trimethylbenzylammonium hydroxide, tetramethylammonium hydroxide, tris(acetylacetonato)aluminum, diisopropoxy(ethylacetoacetate)aluminum, etc. are particularly preferred, and metal-containing compounds such as aluminum-based catalysts, titanium-based catalysts, and tin-based catalysts containing organic ligands are particularly preferred.

[0049] The coating composition of the present invention may contain additives that exert additional effects, provided that the effects of the present invention are not impaired. Examples of additives include leveling agents. Examples of leveling agents that can be used include well-known, commonly used leveling agents, such as acrylic, vinyl, silicone, and fluorine-based leveling agents. Among these, silicone leveling agents having a siloxane structure in the main chain are preferred in terms of enhancing the flame retardancy of the coated article.

[0050] In addition, examples of additives other than the leveling agent include ultraviolet absorbers, anti-termite agents, antioxidants, dyes, pigments, etc., and these additives may be used alone or in combination of two or more types.

[0051] In the coating composition of the present invention, the total content of the above components (i) to (iii) relative to the total solid content is preferably 70 mass % or more, more preferably 80 mass % or more, and most preferably 90 mass % or more.

[0052] The coating composition of the present invention can be produced by mixing the above-mentioned components (i) and (ii), and, if necessary, components (iii), (iv), (v), and other components. The method for mixing the components may be appropriately selected from known methods and is not particularly limited. Examples of devices that can be used for mixing include mixers, shakers, ultrasonic homogenizers, high-pressure homogenizers, bead mills, and ball mills. For the purpose of promoting dissolution and dispersion of the components, the mixing operation may be performed under heating within a range that does not impair the effects of the present invention.

[0053] [2] Cured product and coated article A cured product (cured film) can be obtained by curing the coating composition of the present invention. For example, a flame-retardant coated article can be obtained by applying the coating composition of the present invention directly or via one or more other layers to at least a portion of the surface of a wood substrate to be flame-retarded, and then curing to form a coating film (coating layer). After applying the coating composition of the present invention to the surface of a wood substrate, a coating film can be formed by drying alone, without curing by crosslinking the organopolysiloxane of component (i) above.

[0054] The coating composition of the present invention can also be suitably used as a coating composition for an undercoat layer on a wooden substrate. A flame-retardant coated article can be obtained by forming a topcoat layer on the surface of the wooden substrate, the topcoat layer being a coating film obtained by applying, drying, and, if necessary, curing a coating composition for a topcoat layer containing a flame retardant, via an undercoat layer consisting of a coating film obtained by applying, drying, and, if necessary, curing the coating composition of the present invention.

[0055] In this case, the coating layer having the above-mentioned undercoat layer and topcoat layer may be formed on a part of the surface of the substrate or on the entire surface. For example, in the case of a plate-shaped substrate, the coating layer may be formed on at least one surface thereof.

[0056] (1) Wood-based substrate Examples of wood-based substrates include sawn wood products, logs, plywood, laminated veneer lumber (LVL), laminated timber, cross-laminated timber (CLT), high-strength engineered wood lumber (LSL), laminated veneer board (LVB), laminated veneer sandwich (LVS), parallel strand lumber (PSL), medium-density fiberboard (MDF), structural panels (oriented strand board (OSB)), particle board, fiberboard, and other wood materials. In particular, building materials such as sawn lumber, laminated lumber, and CLT-type substrates are suitable.

[0057] Furthermore, these wood substrates and wood substrates whose surfaces have been treated, specifically wood substrates that have been treated with chemical conversion coating, corona discharge treatment, plasma treatment, or acid or alkaline solution, can also be used.

[0058] Alternatively, the coating composition of the present invention may be applied to the surface of a wood substrate on which other functional layers have already been formed. Examples of such functional layers include an anti-corrosion layer, a gas barrier layer, a waterproof layer, and a heat-shielding layer, and one or more of these layers may be formed in advance on the wood substrate.

[0059] (2) Primer Layer The primer layer can be formed by applying the coating composition of the present invention described above to at least a portion of the surface of the wood substrate, followed by drying and, if necessary, curing.

[0060] The conditions for applying and drying the coating composition of the present invention to a wood substrate may be appropriately determined depending on the type and shape of the wood substrate, etc. Specific conditions can be appropriately selected from known conditions.

[0061] The coating method for the coating composition may be appropriately selected from known techniques, and various coating methods such as brush coating, spraying, dipping, flow coating, roll coating, curtain coating, spin coating, and knife coating can be used. The coating composition of the present invention is a composition that can form a film at, for example, about 0 to 40°C, preferably about 5 to 35°C, but is more preferably one that can form a film after 24 hours at 25°C. Note that, in order to shorten the curing time, the composition may be heated within a temperature range that does not adversely affect the substrate, etc.

[0062] (3) Topcoat Layer The topcoat layer can be formed by applying a coating composition for topcoat layer onto the above-mentioned primer layer, drying and, if necessary, curing. From the viewpoints of moisture resistance, flame retardancy, and coating film transparency, the topcoat layer is preferably formed from a coating composition for topcoat layer containing the following components (A) to (C): (A) an organopolysiloxane composed of units represented by the following formula (2) in a unit ratio: (B) a flame retardant; and (C) an inorganic filler.

[0063] (A) Organopolysiloxane Component (A) is an organopolysiloxane composed of units represented by the following formula (2): (R 5 3SiO 1 / 2 ) is the M unit, (R 6 2SiO) is a D unit, and (R 7 SiO 3 / 2 A unit represented by (SiO2) is called a T unit, and a unit represented by (SiO2) is called a Q unit.

[0064] (R 5 3SiO 1 / 2 ) f (R 6 2SiO) g (R 7 1SiO 3 / 2 ) h (SiO2)i (OR 8 ) j (2)

[0065] In formula (2), R 5 , R 6 and R 7 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with one or more amino groups, hydroxy groups, epoxy groups, acid anhydride groups, maleimide groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, or heterocyclic groups, and these R 5 , R 6 and R 7 At least a part of the above is an alkyl group having 1 to 20 carbon atoms substituted with an amino group, an aryl group having 6 to 20 carbon atoms substituted with an amino group, or an aralkyl group having 7 to 20 carbon atoms substituted with an amino group.

[0066] The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-decyl, cyclopentyl, and cyclohexyl groups. Methyl and ethyl groups are preferred in terms of enhancing the flame retardancy of the coating composition. Examples of aryl groups having 6 to 20 carbon atoms include phenyl and naphthyl. Examples of aralkyl groups having 7 to 20 carbon atoms include benzyl and phenethyl. Examples of heterocyclic groups include piperidinyl, pyridinyl, pyrrolyl, and thienyl.

[0067] As described above, in formula (2), R 5 , R 6 and R 7At least a part of the groups is an alkyl group having 1 to 20 carbon atoms substituted with an amino group, an aryl group having 6 to 20 carbon atoms substituted with an amino group, or an aralkyl group having 7 to 20 carbon atoms substituted with an amino group, and as such a group substituted with an amino group, a γ-aminopropyl group or an N-(2-aminoethyl)-3-aminopropyl group is preferred. Considering the solubility of component (A) in water, the affinity with the flame retardant component and the substrate, etc., R 5 , R 6 and R 7 Among these, the total number of alkyl groups having 1 to 20 carbon atoms and substituted with amino groups, aryl groups having 6 to 20 carbon atoms and substituted with amino groups, or aralkyl groups having 7 to 20 carbon atoms and substituted with amino groups is preferably 50 mol % or more, more preferably 55 mol % or more, and even more preferably 60 mol % or more, based on the total number of silicon atoms in formula (2).

[0068] In addition, R 5 , R 6 and R 7 Among these, the substituents other than the group substituted with an amino group are preferably methyl or ethyl groups, which have a small number of carbon atoms in the combustible alkyl chain, and more preferably methyl groups.

[0069] In formula (2), R 8 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Specific examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, and n-octyl groups. Among these, R 8 is preferably a hydrogen atom.

[0070] f is a number between 0 and 0.5, g is a number between 0 and 0.5, h is a number between 0.2 and 1.0, and i is a number between 0 and 0.5, and is a number that satisfies f+g+h+i=1. j is a number between 0 and 3.0, and is preferably a number between 0.1 and 2.0 from the viewpoint of the water solubility of the organopolysiloxane. If j exceeds 3.0, the film-forming properties of the coating composition and the moisture resistance of the coating film may deteriorate.

[0071] The organopolysiloxane of component (A) has undergone condensation to a certain extent, which facilitates network formation and facilitates fixation to the substrate. In addition, the organopolysiloxane contains fewer alkoxy groups, which are sources of combustible gas, than monomer components (such as silane coupling agents) that do not contain siloxane bonds (Si—O—Si bonds), which provides the advantage of less reduction in flame retardancy.

[0072] The amount of the monomer component not containing a siloxane bond is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and even more preferably 1% by mass or less, relative to the organopolysiloxane of component (A). The ratio of the monomer component not containing a siloxane bond to the organopolysiloxane component is as follows: 29 It can be determined from the signal and integral ratio in the Si-NMR (nuclear magnetic resonance) spectrum.

[0073] The organopolysiloxane of component (A) can be produced by hydrolytic condensation of the monomer components of the respective structural units in the presence of an acid or base catalyst.

[0074] Examples of the monomer of the Q unit include tetramethoxysilane, tetraethoxysilane, tetra(n-propoxy)silane, tetra(i-propoxy)silane, tetra(n-butoxy)silane, alkali silicate, and activated silicic acid obtained by cation exchange of alkali silicate.

[0075] Examples of monomers for the T unit include methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3 ,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, perfluorooctylethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, γ-isocyanatepropyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane, and the like.Among these, taking into consideration the solubility of the resulting siloxane in water, the affinity with wood and flame retardant components, and the like, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, γ-isocyanatepropyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane are preferred, and γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltriethoxysilane are more preferred.

[0076] Examples of the monomer for the D unit include dimethyldimethoxysilane, dimethyldiethoxysilane, methylethyldimethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, diisopropyldimethoxysilane, phenylmethyldimethoxysilane, vinylmethyldimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. Among these, γ-aminopropylmethyldiethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane are preferred, taking into consideration the solubility of the resulting siloxane in water and the affinity with wood and flame retardant components.

[0077] Examples of monomers for M units include trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, n-propyldimethylmethoxysilane, n-propyldiethylmethoxysilane, isopropyldimethylmethoxysilane, isopropyldiethylmethoxysilane, isopropyldimethylethoxysilane, n-butyldimethylmethoxysilane, n-butyldimethylethoxysilane, n-hexyldimethylmethoxysilane, n-hexyldimethylethoxysilane, n-pentyldimethylmethoxysilane, n-pentyldimethylethoxysilane, and n-hexyldimethylmethoxysilane. Examples of suitable organosiloxanes include silane, n-hexyldimethylethoxysilane, n-decyldimethylmethoxysilane, n-decyldimethylethoxysilane, trimethylsilanol, triethylsilanol, n-propyldimethylsilanol, n-propyldiethylsilanol, isopropyldimethylsilanol, isopropyldiethylsilanol, n-butyldimethylsilanol, n-hexyldimethylsilanol, n-pentyldimethylsilanol, n-decyldimethylsilanol, γ-aminopropyldimethylmethoxysilane, and N-(2-aminoethyl)-3-aminopropyldimethylmethoxysilane. Among these, γ-aminopropyldimethylmethoxysilane and N-(2-aminoethyl)-3-aminopropyldimethylmethoxysilane are preferred, taking into consideration the solubility of the resulting organopolysiloxane in water and the affinity with the substrate and flame retardant components.

[0078] Because the M units and D units have two or more Si-C bonds and are easily combustible, the content of M units and D units of all structural units in the organopolysiloxane of component (A) is preferably 50 mol% or less. That is, in the above formula (2), f is preferably a number from 0 to 0.5, more preferably a number from 0 to 0.2, and even more preferably a number from 0 to 0.1. Furthermore, g is preferably a number from 0 to 0.5, more preferably a number from 0 to 0.2, and even more preferably a number from 0 to 0.1.

[0079] Since T units have one Si-C bond and are less flammable than D units and M units, the inclusion of 20 mol % or more of T units among all the structural units in the organopolysiloxane of component (A) results in good flame retardancy. That is, in the above formula (2), h is preferably a number from 0.2 to 1.0, more preferably a number from 0.5 to 1.0, and even more preferably a number from 0.6 to 1.0.

[0080] The Q units contain no Si-C bonds and have low flammability, and are effective in preventing a decrease in flame retardancy due to combustion resulting from the Si-C bonds. On the other hand, because the Q units have many crosslinking points and are highly reactive, from the viewpoints of compatibility with the flame retardant component and film-forming ability, the Q units preferably account for 0 to 50 mol % of all structural units in the organopolysiloxane of component (A). That is, i is preferably a number from 0 to 0.5, more preferably a number from 0.1 to 0.4, and even more preferably a number from 0.3 to 0.4.

[0081] The ratio of the structural units in component (A) is, for example, 29 This can be confirmed by a known method using the ratio of the chemical shift and integral value of the Si-NMR signal.

[0082] The content of component (A) is preferably 5 to 60% by mass, more preferably 10 to 40% by mass, based on the total coating composition for the top coat layer. When the content is 5% by mass or more, the film-forming properties, transparency, and moisture resistance of the coating film are improved. When the content is 60% by mass or less, the flame retardancy of the coating film is improved. Component (A) may be used alone or in combination of two or more types.

[0083] (B) Flame Retardant Component (B) is one or more flame retardants selected from phosphorus-based, boron-based, magnesium-based, aluminum-based, nitrogen-based, antimony-based, and halogen-based compounds. Phosphorus-based compounds include, for example, organic phosphorus compounds, phosphoric acid, phosphate esters, and phosphate salts. Specific examples include diammonium hydrogen phosphate, ammonium dihydrogen phosphate, diguanidine phosphate, ammonium polyphosphate, hydrophobized ammonium polyphosphate, guanylurea phosphate, carbamate polyphosphate, and melamine phosphate. Boron-based compounds include, for example, organic boron compounds, boric acid, borax, boron oxide, borate esters, and borates. Magnesium-based compounds include, for example, magnesium hydroxide and magnesium oxide. Aluminum-based compounds include, for example, aluminum hydroxide. Nitrogen-based compounds include, for example, ammonium sulfate, ammonium carbonate, ammonium bicarbonate, and melamine cyanurate. Antimony-based compounds include, for example, antimony trioxide. Examples of halogen compounds include zinc chloride.

[0084] Among these, phosphorus-based compounds and boron-based compounds are preferred as flame retardants for use in the coating composition for the top coat layer, and it is particularly preferred to use phosphates and polyphosphates, which form a carbonized layer in a short time and are easy to ensure flame retardancy. In particular, it is preferred to use a water-soluble phosphate and / or polyphosphate in combination with a water-insoluble phosphate and / or polyphosphate, as this further improves the flame retardancy and moisture resistance of the coating film without impairing the transparency of the coating film.

[0085] The blending amount of component (B) is preferably 50 to 300 parts by mass, and particularly preferably 75 to 250 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). If the blending amount is less than 50 parts by mass, the flame retardancy of the coating film may be insufficient, and if the blending amount exceeds 300 parts by mass, the coating film may be inferior in film-forming ability, transparency, and moisture resistance. Component (B) may be used alone, or two or more types may be used in combination.

[0086] (C) Inorganic Filler As the inorganic filler of component (C), known general inorganic fillers can be used, such as inorganic fillers containing Group 13 elements, Group 14 elements (excluding carbon), first-series transition elements, second-series transition elements, third-series transition elements, lanthanides, etc. Inorganic fillers containing Group 13 elements include oxides derived from aluminum, boron, indium, etc., with alumina being preferred. Inorganic fillers containing Group 14 elements (excluding carbon) include oxides and salts thereof derived from silicon, tin, etc., with silica being preferred. Inorganic fillers containing first-series transition elements include oxides derived from titanium, manganese, zinc, etc., and these oxides can also be used as light-absorbing materials with specific wavelengths. Inorganic fillers containing second-series transition elements include oxides derived from yttrium, zirconium, etc., and these oxides can also be used as light-absorbing and fluorescent materials with specific wavelengths. Inorganic fillers containing third-series transition elements include oxides derived from hafnium, tantalum, etc. Examples of inorganic fillers containing lanthanoids include oxides derived from lanthanum, cerium, praseodymium, neodymium, terbium, dysprosium, ytterbium, etc. These oxides can also be used as light absorbing and fluorescent materials with specific wavelengths. In addition, compounds of two or more of these oxides formed via chemical bonds can also be used.

[0087] The shape of the inorganic filler is not particularly limited, and inorganic fillers of various shapes such as spherical, hollow spherical, porous, plate-like, needle-like, fibrous, etc. Among these, fibrous inorganic fillers are preferred because they are highly effective in suppressing cracks in the ceramic layer formed after combustion and provide particularly good flame retardancy.

[0088] In particular, as the inorganic filler used in the coating composition for the top coat layer, it is preferable to use inorganic oxides or silicates containing elements such as silicon, boron, and aluminum, which become ceramic upon combustion and form a fire-resistant layer or a heat-insulating layer. In particular, it is preferable to use a silicon oxide-containing filler such as silica or glass fiber in combination with a phyllosilicate such as clay, as this improves flame retardancy.

[0089] The blending amount of component (C) is preferably 25 to 150 parts by mass, and particularly preferably 50 to 150 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). If it is less than 25 parts by mass, the flame retardancy of the coating film may be insufficient, and if it exceeds 150 parts by mass, the film-forming properties and transparency of the coating film may be poor. Component (C) may be used alone, or two or more types may be used in combination.

[0090] In the coating composition for the top coat layer, the ratio of the total mass of the components (B) and (C) to the mass of the component (A), [(B) + (C)] / (A), is preferably 1.0 to 4.5, more preferably 1.2 to 4.0, and even more preferably 1.5 to 2.5. When this ratio is 1.0 or more, the flame retardancy is good, and when it is 4.5 or less, the moisture resistance, film-forming ability, and transparency of the coating film are good.

[0091] (D) Leveling Agent The coating composition for the top coat layer may contain a component derived from a leveling agent (D). As the leveling agent, for example, a known common leveling agent such as an acrylic, vinyl, silicone, or fluorine-based leveling agent can be used. Among these, a silicone-based leveling agent having a siloxane structure in the main chain is preferred from the viewpoint of enhancing the flame retardancy of the coating composition.

[0092] When component (D) is used, its amount is preferably 1 to 10 parts by mass, more preferably 3 to 6 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). Within this range, a topcoat layer with excellent film-forming properties can be obtained while maintaining flame retardancy and transparency. Component (D) may be used alone, or two or more types may be used in combination.

[0093] (E) Solvent The coating composition for the top coat layer may contain a solvent in addition to the above components. The solvent is not particularly limited, but alcohol or water is preferred, and water is more preferred from the viewpoints of environmental conservation and easy availability.

[0094] When water is used as the solvent, specific examples of fresh water that can be used include tap water, industrial water, well water, natural water, rainwater, distilled water, and ion-exchanged water, with ion-exchanged water being particularly preferred. Ion-exchanged water can be produced using a pure water maker (e.g., FW-10, manufactured by Organo Corporation, Direct-QUV3, manufactured by Merck Millipore, etc.).

[0095] When a solvent is used, the amount blended is preferably 20 to 80% by mass, more preferably 30 to 60% by mass, of the total topcoat layer coating composition. When the solvent is contained in an amount of 20% by mass or more of the total composition, the fluidity and workability of the coating are improved, and when the solvent is contained in an amount of 80% by mass or less of the total composition, the concentration of the active ingredient in the coating is high, making it easier to thicken the coating film.

[0096] The coating composition for the topcoat layer may contain a curing catalyst for the purpose of accelerating the curing reaction. The type, amount, and addition method of the curing catalyst can be determined by known methods and conditions depending on the type of composition. Specifically, the above-mentioned examples of component (v) can be used.

[0097] The coating composition for the top coat layer may contain additives that exert additional effects, provided that the effects of the present invention are not impaired. Examples of additives include ultraviolet absorbers, anti-termite agents, antioxidants, dyes, pigments, etc. These additives may be used alone or in combination of two or more types.

[0098] The total content of the components (A) to (C) relative to the total solid content of the coating composition for the topcoat layer is preferably 70% by mass or more, more preferably 80% by mass or more, and most preferably 90% by mass or more.

[0099] The coating composition for the topcoat layer can be produced by mixing the above components (A) to (C), and, if necessary, component (D), component (E), and other components. The method for mixing the components may be appropriately selected from known methods and is not particularly limited. Examples of devices that can be used for mixing include mixers, shakers, ultrasonic homogenizers, high-pressure homogenizers, bead mills, and ball mills. For the purpose of promoting dissolution and dispersion of the components, the mixing operation may be performed under heating within a range that does not impair the effects of the present invention.

[0100] The conditions for applying and drying the coating composition for the topcoat layer onto the undercoat layer to form the topcoat layer can be set appropriately depending on the type and shape of the wood substrate, and the specific conditions can be selected appropriately from known conditions.

[0101] The coating method may be appropriately selected from known techniques, and various coating methods such as brush coating, spraying, dipping, flow coating, roll coating, curtain coating, spin coating, and knife coating can be used. The coating composition for the top coat layer is a composition that can form a film at about 0 to 40°C, preferably about 5 to 35°C, and more preferably one that can form a film after 24 hours at 25°C. Note that, in order to shorten the curing time, it may be heated within a temperature range that does not adversely affect the substrate, etc.

[0102] The coating weight of the undercoat layer and the topcoat layer is not particularly limited, but the undercoat layer is preferably 0.01 to 0.50 kg / m of the substrate. ２ It is preferable to coat the material so that the coating weight is 0.01 to 0.10 kg / m ２ Within this range, the flame retardancy is improved and the effect of suppressing poor appearance around the knots is improved. The top coat layer is applied to the substrate at a pressure of 0.1 to 2.0 kg / m ２ It is preferable to coat the coating so that the coating weight is 0.2 to 1.0 kg / m ２ It is more preferable to coat the substrate so that the coating amount falls within this range. If the coating amount falls within this range, the flame retardancy and the appearance of the coating film will be good. In order to achieve a coating amount within the above range, the coating composition may be applied so that the coating amount of the solid content of the coating composition falls within the above range relative to the substrate.

[0103] The coated article of the present invention may be coated on the surface on which the topcoat layer is formed or on the surface opposite thereto with one or more layers such as a hard coat layer, an anticorrosive layer, a gas barrier layer, a waterproof layer, a heat-shielding layer, an antifouling layer, a photocatalytic layer, or an antistatic layer. Materials constituting these layers include alkyd resins, acrylic resins, urethane resins, acrylic silicone resins, fluororesins, silicone resins, epoxy resins, vinylidene chloride copolymer resins, vinyl chloride resins, and the like (whether water-based or solvent-based). The above layers can be applied as a coating liquid or laminated as pre-formed films by bonding them together via an adhesive or the like.

[0104] The present invention will be explained in more detail below with reference to Synthesis Examples, Comparative Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0105] [1] Preparation of Coating Compositions for Primer Layer [Examples 1 to 8, Comparative Examples 1 to 6] Coating compositions for primer layer were prepared by mixing the following components in the amounts shown in Tables 1 and 2. Note that the active ingredient concentration in Tables 1 and 2 refers to the total of the solid content of the blended amounts of component (i), comparative component, component (ii-1), component (ii-2), component (ii-3), and component (iii-1), the blended amount of component (ii-4), and the blended amount of component (iii-2) per 100 parts by mass of the coating composition; and the active ingredient mass ratio in Tables 1 and 2 is the value calculated by converting the mass ratio of each component based on the solid content, with component (i) being 100.

[0106] (i) Component (i-1): A 30% by mass aqueous solution of a hydroxyl group-containing organopolysiloxane (a = 0, b = 0, c = 1.0, d = 0, e = 0.7, R 3 = methyl group, a group represented by the following formula (3), R 4 = hydrogen atoms, hydroxy group substitution amount (relative to total silicon atoms) = 200 mol%) (In the formula, the wavy line represents a bond.)

[0107] [Comparative component] (i'-2): Aqueous dispersion of acrylic resin produced in Comparative Synthesis Example 1 below

[0108] Comparative Synthesis Example 1 200 parts by mass of ion-exchanged water and 6.0 parts by mass of a non-reactive emulsifier (Hitenol NF0825: anionic, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) were placed in a five-neck flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping device, and a nitrogen inlet tube. The flask was heated to 80°C while the atmosphere inside was purged with nitrogen, and then 1.0 part by mass of potassium persulfate was added. Subsequently, a mixture of 190 parts by mass of methyl methacrylate, 250 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 220 parts by mass of ion-exchanged water, and 30.0 parts by mass of the non-reactive emulsifier, which had been mixed and stirred in a separate container, was continuously added dropwise over 3.5 hours. After that, the mixture was aged for 2 hours at 80°C while continuing to stir, and then a mixture of 2.7 parts by mass of ion-exchanged water and 0.3 parts by mass of a 70% by mass aqueous solution of tert-butyl hydroperoxide was added to the reactor, followed by continuous dropwise addition of a mixture of 9.7 parts by mass of ion-exchanged water and 0.3 parts by mass of sodium erythorbate over 5 minutes. The mixture was then aged for 2 hours at 80°C while continuing to stir, and after cooling to room temperature, 4.0 parts by mass of a 25% by mass aqueous ammonia solution was added to adjust the pH to 9.0, yielding an aqueous acrylic resin dispersion i'-2. The acrylic resin content in the dispersion was 49.8% by mass, and the volume average particle size of the emulsion was 144 nm.

[0109] (ii) Component ii-1: Snowtex OL (20 mass% silica aqueous dispersion, particle size 45 nm, manufactured by Nissan Chemical Industries, Ltd.) ii-2: Snowtex O40 (40 mass% silica aqueous dispersion, particle size 22 nm, manufactured by Nissan Chemical Industries, Ltd.) ii-3: Aluminasol 520-A (20 mass% alumina aqueous dispersion, manufactured by Nissan Chemical Industries, Ltd.) ii-4: BENTONE-EW NA (hectorite clay, manufactured by Elementis Specialties, Inc.)

[0110] (iii) Component iii-1: Nonnen W2-50 (a 50% by mass aqueous solution of phosphorus-nitrogen flame retardant, manufactured by Maruzen Chemical Industries Co., Ltd.) iii-2: Boric acid (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.)

[0111] [Evaluation of Paint Stability] The stability of the primer paint composition was evaluated visually according to the following criteria. In this evaluation, the settling over time of the water-insoluble flame retardant component or filler component, which is originally a solid, was not judged to be a deterioration in paint stability, so long as the composition could be used without problems if shaken. The results are also shown in Tables 1 and 2. ◯: When gelation or solid precipitation did not occur when the components were blended, and the composition remained liquid. ×: When gelation or solid precipitation occurred when the components were blended.

[0112] [2] Preparation of Coating Composition for Top Coat Layer [Synthesis Example 1] A 30% by mass aqueous solution of amino group-containing organopolysiloxane (A-1, where f = 0, g = 0, h = 0.7, i = 0.3, j = 0.7 in the above formula (2), R 7 = methyl group, N-(2-aminoethyl)-3-aminopropyl group, R 8 = hydrogen atoms, amine substitution amount (relative to total silicon atoms) = 61 mol%) 56.0 g, Nonnene W2-50 (B-1, a 50% by weight aqueous solution of phosphorus-nitrogen flame retardant, manufactured by Maruzen Yuka Kogyo Co., Ltd.) 16.7 g, Taien K (B-2, a water-insoluble ammonium polyphosphate powder, manufactured by Pacific Industrial Co., Ltd.) 13.6 g, EPH80M-01N (C-1, glass fiber, manufactured by Nippon Electric Glass Co., Ltd.) 12.7 g), BYK3450 (leveling agent, polyether-modified polydimethylsiloxane, manufactured by BYK Japan Co., Ltd.) 0.9 g were mixed to prepare an aqueous coating composition. The solids ratio of each component in the solution was 100 parts by weight of component (A), 131 parts by weight of component (B), and 76 parts by weight of component (C).

[0113] [3] Preparation of coated wood and its evaluation. Cedar wood containing knots (air-dry specific gravity: 0.27-0.49) was dried at 115°C for 24 hours and cut into 300mm x 300mm x 20mm pieces. Each primer coating of Examples 1-8 and Comparative Examples 2-6 was applied to the wood in a coating amount of solids of approximately 0.01-0.02 kg / m. ２ The top coat paint obtained in Synthesis Example 1 was then applied to the substrate in a solids amount of about 0.38 kg / m ２The coating was then left to cure at a temperature of 21 to 25°C and a relative humidity of 45 to 55% RH until a constant mass was reached. For Comparative Example 1, no primer coating was applied, and the top coating obtained in Synthesis Example 1 was applied at a coating weight of solids of approximately 0.38 kg / m ２ The coated cedar wood was then cured at a temperature of 21 to 25°C and a relative humidity of 45 to 55% RH until a constant mass was achieved. The following tests were carried out on the coated cedar wood.

[0114] (1) Paint Film Appearance The appearance of the paint film around the knots of cedar wood was visually evaluated according to the following criteria. The results are also shown in Table 1. ◯: The paint film around the knots was transparent and the wood grain could be seen. ×: The paint film around the knots was cloudy white. (2) Moisture Resistance Each piece of wood was subjected to five cycles of wet-dry repetition, with one cycle consisting of 40°C, 90% RH (24 hours) followed by 60°C air drying (24 hours). After that, the wood was allowed to cool at 20°C, 60% RH for 24 hours, after which the condition of the paint film surface was observed and visually evaluated according to the following criteria. The results are also shown in Table 1. ◯: No whitening, deliquescence, discoloration, etc. was observed ×: Whitening, deliquescence, discoloration, etc. was observed (3) Flame Retardancy Each piece of wood was subjected to a radiant heat intensity of 50 kW / m 2 A cone calorimeter test (ISO-5660-1) was conducted, and the flame retardancy was evaluated according to the following criteria: ⊚: The calorific value after 10 minutes of heating was 6 (MJ / m 2 ) or less. 〇: The calorific value after 10 minutes of heating is 8 (MJ / m 2 ) or less ×: The calorific value after 10 minutes of heating is 8 (MJ / m 2 ) and / or the coating expands and comes into contact with the device (igniter)

[0115]

[0116] *: Expanded coating film comes into contact with the device

[0117] As shown in Table 1, the coated articles of Examples 1 to 8, which had a primer layer made of a coating composition satisfying the requirements of the present invention and a topcoat layer containing a siloxane compound, a flame retardant, and an inorganic filler, exhibited good coating appearance and moisture resistance, suppressed whitening around knots, and exhibited low heat release during combustion, thereby meeting the flame retardancy standards for quasi-noncombustible wood. From the above, it can be seen that the application of a primer layer made of a coating composition satisfying the requirements of the present invention fills the gaps between the wood fibers, inhibits the penetration of the topcoat into the wood, and enables the formation of a uniform topcoat layer, thereby suppressing whitening. Furthermore, it is possible to form a sturdy ceramic layer during combustion, and the resulting fire resistance and insulating effects are thought to significantly improve the flame retardancy of the wood. On the other hand, as shown in Table 2, whitening occurred around knots in Comparative Example 1, which did not have a primer layer. Comparative Examples 2 and 3, which contained insufficient amounts of inorganic filler, resulted in poor flame retardancy. In Comparative Example 4, in which an excessive amount of inorganic filler was added, the primer layer was not sufficiently formed, resulting in poor flame retardancy and whitening around the knots. In addition, in Comparative Examples 5 and 6, in which a primer layer not containing a siloxane structure was provided, the increased amount of flammable organic components caused intense combustion, resulting in poor flame retardancy and swelling of the coating film.

Claims

1. (i) 100 parts by mass of an organopolysiloxane having a unit ratio represented by the following formula (1), and (R 1 3SiO 1 / 2 ) a (R 2 2SiO) b (R 3 1SiO 3 / 2 ) c (SiO2) d (OR 4 ) e (1) (wherein, R 1 , R 2 and R 3 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with one or more amino groups, hydroxyl groups, epoxy groups, acid anhydride groups, maleimide groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, or heterocyclic groups, and which may have an ether bond, 1 , R 2 and R 3 at least a part of which is an alkyl group having 1 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, an aryl group having 6 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond, or an aralkyl group having 7 to 20 carbon atoms and which is substituted with a hydroxy group and which may have an ether bond; 4 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, a is 0 to 0.5, b is 0 to 0.5, c is 0.2 to 1.0, d is 0 to 0.5, and e is a number that satisfies 0 to 3.0, and a+b+c+d=1.) (ii) an inorganic filler: 100 to 900 parts by mass.

2. The above R 1 , R 2 and R 3 2. The coating composition according to claim 1, wherein the total number of hydroxy groups contained in the formula (1) is 50 mol % or more based on the total number of silicon atoms in the formula (1).

3. The coating composition according to claim 1 or 2, wherein the inorganic filler (ii) comprises one or more selected from the group consisting of silica, alumina, and phyllosilicate.

4. A coating composition according to any one of claims 1 to 3, further comprising (iii) 10 to 300 parts by mass of one or more flame retardants selected from phosphorus-, boron-, magnesium-, aluminum-, nitrogen-, antimony- and halogen-based compounds per 100 parts by mass of component (i).

5. The coating composition according to claim 4, wherein the ratio of the total mass of said components (ii) and (iii) to the mass of said component (i), [(ii)+(iii)] / (i), is 2.0 to 9.

0.

6. A cured product of the coating composition according to any one of claims 1 to 5.

7. A coated article having a coating layer comprising a coating of the coating composition according to any one of claims 1 to 5, directly or via one or more other layers, on at least a portion of the surface of a wood substrate.

8. A coated article having, on at least a portion of the surface of a wood substrate, an undercoat layer formed of a coating of the coating composition according to any one of claims 1 to 5, and a topcoat layer formed of a coating of a topcoat coating composition containing the following components (A), (B) and (C): (A) an organopolysiloxane having a unit ratio represented by the following formula (2): 100 parts by mass (R 5 3SiO 1 / 2 ) f (R 6 2SiO) g (R 7 1SiO 3 / 2 ) h (SiO2) i (OR 8 ) j (2) (wherein, R 5 , R 6 and R 7 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with one or more amino groups, hydroxyl groups, epoxy groups, acid anhydride groups, maleimide groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, or heterocyclic groups, and 5 , R 6 and R 7 at least a part of R is an alkyl group having 1 to 20 carbon atoms substituted with an amino group, an aryl group having 6 to 20 carbon atoms substituted with an amino group, or an aralkyl group having 7 to 20 carbon atoms substituted with an amino group; 8 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, f is 0 to 0.5, g is 0 to 0.5, h is 0.2 to 1.0, i is 0 to 0.5, j is 0 to 3.0, and is a number that satisfies f+g+h+i=1.) (B) one or more flame retardants selected from phosphorus-based, boron-based, magnesium-based, aluminum-based, nitrogen-based, antimony-based, and halogen-based compounds: 50 to 300 parts by mass (C) inorganic filler: 25 to 150 parts by mass 9. The coating amount of the undercoat layer is 0.01 to 0.50 kg / m2 of the wood substrate. ２ and the coating amount of the topcoat layer is 0.1 to 2.0 kg / m2 relative to the wood substrate. ２ 9. The coated article of claim 8,

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