Wood coating composition, and kit thereof

Abstract

To provide a novel wood coating composition that can be cured at room temperature and reduce wood degradation due to ultraviolet rays.SOLUTION: The wood coating composition contains a resol-type phenol resin and an organic acid ester compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wood coating composition and a kit therefor. [Background technology]

[0002] Patent Document 1 describes a method for manufacturing outdoor wooden products, in which wood is impregnated with a resin liquid containing a photopolymerization initiator and a thermal polymerization initiator, the resin liquid is hardened and fixed within the wood using ultraviolet light and heat to form a wood-plastic composite layer, and then a urethane coating is applied to the surface of the wood.

[0003] Patent Document 2 describes a wood surface protective agent containing 1 to 30% by weight of an isocyanate compound and 70 to 99% by weight of an organic solvent, wherein the isocyanate compound is (A) a hydrophilic isocyanate compound, or (B) a hydrophobic isocyanate compound, or (C) a mixture of a hydrophilic isocyanate compound and a hydrophobic isocyanate compound.

[0004] Patent Document 3 describes a wood treatment agent that contains one or more methylolated phenol monomers and is used as a weakly acidic or neutral aqueous solution, and a wood treatment method in which the wood treatment agent is injected under pressure into wood to be treated, and then the wood is dried and heated to harden and resinify the methylolated phenol monomers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-103309 [Patent Document 2] Japanese Patent Application Publication No. 2018-53038 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-328104 Summary of the Invention [Problem to be solved by the invention]

[0006] Wood coating compositions are required to have weather resistance and to suppress deterioration of wood due to ultraviolet rays. For example, Patent Documents 1 and 2 do not disclose any findings regarding wood coating compositions containing resol-type phenolic resins.

[0007] The present inventors discovered that by using a resol-type phenolic resin (alkali phenolic resin) in a wood coating composition, it is possible to cure it at room temperature and to suppress deterioration of wood caused by ultraviolet rays, and thus completed the present invention.

[0008] That is, one aspect of the present invention aims to provide a novel wood coating composition that can be cured at room temperature and that can reduce deterioration of wood caused by ultraviolet rays, and related technologies. [Means for solving the problem]

[0009] In order to solve the above problems, a wood coating composition according to one aspect of the present invention contains a resol-type phenolic resin and an organic acid ester compound.

[0010] Furthermore, a wood paint kit according to one embodiment of the present invention includes a first agent containing a resol-type phenolic resin and a second agent containing an organic acid ester compound for mixing with the resol-type phenolic resin. [Effects of the Invention]

[0011] According to one aspect of the present invention, it is possible to provide a novel wood coating composition that can be cured at room temperature and can suppress deterioration of wood due to ultraviolet rays. [Brief explanation of the drawings]

[0012] [Figure 1]Figure 1 is a photograph showing the evaluation results of an outdoor exposure test after 13 months for the wood of Example 7, which was coated twice with Wood Coating Sample-2, and the wood of Comparative Example 2. The top of Figure 1 is a photograph juxtaposing the wood of Example 7, which was coated twice with Wood Coating Sample-2 (top right of Figure 1), with a comparison solid wood that was not exposed to the outdoors (top left of Figure 1), and the bottom of Figure 1 is a photograph juxtaposing the wood of Comparative Example 2 (bottom right of Figure 1) with a comparison solid wood that was not exposed to the outdoors (bottom left of Figure 1). DETAILED DESCRIPTION OF THE INVENTION

[0013] One embodiment of the present invention will be described below, but the present invention is not limited thereto. In this specification, unless otherwise specified, "A to B" representing a range of numerical values ​​means "A or more, B means "below."

[0014] <Wood coating composition> A wood coating composition according to one embodiment of the present invention contains a resol-type phenolic resin and an organic acid ester compound, and may contain other components.

[0015] By reacting a resol-type phenolic resin with an organic acid ester compound, the wood coating composition can be dried outdoors at room temperature, for example, 0 to 40°C, while suppressing deterioration of wood caused by ultraviolet rays.

[0016] [1] Resol-type phenolic resin A wood coating composition according to one embodiment of the present invention contains a resol-type phenolic resin.

[0017] The pH of the resol type phenolic resin at room temperature (25° C.) is preferably 10.0 to 14.0, more preferably 10.5 to 13.5, and even more preferably 11.0 to 13.0. The higher the pH of the resol type phenolic resin within the range of 10.0 to 14.0, the more soluble the resol type phenolic resin in water can be, and the lower the pH, the more rapid the curing rate of the resol type phenolic resin at room temperature can be.

[0018] The viscosity of the resol phenolic resin is preferably 1 to 3,000 mPa·s, more preferably 5 to 2,000 mPa·s, even more preferably 10 to 1,000 mPa·s, particularly preferably 10 to 800 mPa·s, and most preferably 10 to 500 mPa·s. If the viscosity of the resol phenolic resin is within the range of 1 to 3,000 mPa·s, the wood coating composition can be imparted with even better coating workability. The viscosity of the resol phenolic resin can be measured at room temperature (25°C) using an E-type viscometer.

[0019] The resol-type phenolic resin is contained in the wood coating composition as an aqueous solution. The solids concentration of the aqueous solution can be adjusted as desired with water and is not limited to, but is preferably 20.0 to 60.0 wt.%, more preferably 30.0 to 55.0 wt.%, and even more preferably 30.0 to 50.0 wt.%. The higher the solids concentration of the resol-type phenolic resin within the range of 20.0 to 60.0 wt.%, the thicker the film thickness of the wood coating composition that can be applied in a single coat can be. The lower the solids concentration within the range of 20.0 to 60.0 wt.%, the easier the coating workability of the wood coating composition can be. Furthermore, by increasing the solids concentration of the resol-type phenolic resin within the range of 20.0 to 60.0 wt.%, the effect of preventing wood deterioration due to ultraviolet rays can be further improved.

[0020] The solids concentration of the resol-type phenolic resin can be determined by weighing a predetermined amount of a sample of the resol-type phenolic resin before drying onto a weighing dish, placing it in an incubator maintained at 135±1°C, drying for 60±2 minutes, and then allowing it to cool in a desiccator. Based on the results, the weight of the dried sample, D (g), can be calculated using the following formula (1), and the solids concentration can be calculated using the following formula (2). D = C2 - C1 (1) Solid content concentration (wt%)=D / S×100...(2) Weight of weighing dish: C1 (g) Sample weight before drying: S (preferably about 1.5±0.1g) Sample weight after drying: C2 (g)

[0021] The weight-average molecular weight (Mw) of the resol-type phenolic resin is preferably in the range of 300 to 8,000, more preferably in the range of 400 to 5,000, even more preferably in the range of 600 to 3,000, particularly preferably in the range of 800 to 2,500, and most preferably in the range of 1,000 to 2,000. A higher weight-average molecular weight (Mw) of the resol-type phenolic resin within the range of 300 to 8,000 can increase the curing rate of the coating film and increase the surface hardness. A lower weight-average molecular weight (Mw) within the range of 300 to 8,000 can reduce the viscosity of the wood coating composition and the surface hardness after coating, making the coating less likely to crack and improving coating workability. The weight-average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0022] Resole phenolic resins have a phenolic core structure in which a hydroxyl group is attached to a benzene ring, so they leave a large residue after combustion and are difficult to burn, making them suitable for wood coatings compared to, for example, urethane resins and epoxy resins. Furthermore, resol phenolic resins have the advantage of being three-dimensionally crosslinked, resulting in excellent heat resistance.

[0023] [1-1] Method for producing resol-type phenolic resin The resol-type phenolic resin can be synthesized, for example, by reacting a phenol with an aldehyde in the presence of an alkali catalyst. Here, the phenol used in the synthesis of the resol-type phenolic resin can include a novolac-type phenolic resin.

[0024] [1-2] Phenols Phenols are compounds having a structure in which at least one hydroxyl group is bonded to an aromatic ring. Examples include phenols having a hydroxyl group bonded to a phenyl ring, polyaromatic ring phenols, which are condensed aromatic compounds containing a phenyl ring to which a hydroxyl group is bonded as part of their structure, and polyhydric phenols. These phenols may have a substituent such as an alkyl group. Examples of phenols include phenol; alkylphenols such as o-, m-, and p-cresols, o-, m-, and p-ethylphenols, and xylenol and its isomers; polyaromatic ring phenols such as α- and β-naphthols; and polyhydric phenols such as bisphenol A, bisphenol F, bisphenol S, pyrogallol, resorcinol, catechol, and hydroquinone. Furthermore, the phenol may be cardanol or cashew nut shell liquid. These phenols may be used alone or in combination of two or more.

[0025] (Novolac type phenolic resin) The phenols used to obtain the wood coating composition may include, for example, novolac-type phenolic resins (also called novolac resins) obtained by a primary reaction of phenols with aldehydes using an acid catalyst. The resol-type phenolic resins obtained by converting the novolac resin obtained by such a primary reaction into a resol by a secondary reaction using aldehydes and an alkali catalyst are sometimes called secondary reaction resol-type phenolic resins.

[0026] Secondary reaction resol-type phenolic resins are produced by converting novolac-type phenolic resins into resols, so they tend to contain phenolic condensates with higher molecular weights than phenolic condensates and have a lower content of low-molecular-weight components with trinuclear or lower molecular weights.

[0027] Examples of acid catalysts for obtaining a novolak resin in the primary reaction include inorganic acids, organic acids, and organic acid salts, etc. Inorganic acids include hydrochloric acid, sulfuric acid, phosphoric acid, etc. Organic acids include oxalic acid, acetic acid, citric acid, tartaric acid, benzoic acid, and paratoluenesulfonic acid, etc. Organic acid salts include zinc acetate, zinc borate, etc. These acid catalysts may be used alone or in combination of two or more.

[0028] The amount of the acid catalyst used in the primary reaction to obtain the novolak resin is preferably 0.05 to 2.00 parts by weight, more preferably 0.10 to 1.00 parts by weight, based on 100 parts by weight of the phenols.

[0029] Aldehydes used to obtain a novolac phenolic resin in the primary reaction include aldehydes used to obtain a resol phenolic resin, which will be described later. The molar ratio of aldehydes to phenols (hereinafter also referred to as the "F / P molar ratio") in the primary reaction to obtain a novolac phenolic resin is preferably 0.6 to 0.9, more preferably 0.7 to 0.8. If the F / P molar ratio in the novolac phenolic resin is 0.6 or more, the amount of aldehydes during the resol reaction (secondary reaction) can be reduced, and if it is 0.9 or less, gelation during the novolac reaction (primary reaction) can be suppressed.

[0030] The weight average molecular weight (Mw) of the novolac phenolic resin obtained by the primary reaction is preferably 1,000 to 8,000, more preferably 1,500 to 6,000. If the Mw of the novolac phenolic resin is within the above range, the Mw of the secondary reaction resol phenolic resin tends to fall within the preferred range described below.

[0031] [1-3] Aldehydes The aldehyde is at least one compound selected from the group consisting of compounds having a formyl group and polymers thereof, and examples thereof include formaldehyde, paraformaldehyde, acetaldehyde, propylaldehyde, benzaldehyde, salicylaldehyde, and glyoxal. One type of aldehyde may be used alone, or two or more types may be used in combination. Of these, the aldehyde is preferably selected from, for example, formaldehyde and paraformaldehyde.

[0032] (F / P molar ratio of resol-type phenolic resin) The F / P molar ratio of phenols (P) to aldehydes (F) to obtain a resol-type phenolic resin is preferably 1.0 or more, more preferably 1.5 or more. The F / P molar ratio is preferably 4.0 or less, more preferably 2.5 or less, and the smaller the F / P molar ratio, the more the amount of unreacted formaldehyde (free formaldehyde) can be reduced, and the more the amount of formaldehyde emitted from the wood coating composition can be reduced.

[0033] When the resol-type phenolic resin is a secondary reaction resol-type phenolic resin, the F / P molar ratio in the secondary reaction resol-type phenolic resin is preferably 2.0 to 2.6, more preferably 2.1 to 2.5. The F / P molar ratio in the secondary reaction resol-type phenolic resin is the F / P molar ratio (final F / P molar ratio) calculated from the sum of the amount of aldehydes used to obtain the novolac-type phenolic resin in the primary reaction and the amount of aldehydes used to resole the novolac-type phenolic resin. That is, when obtaining a secondary reaction resol-type phenolic resin as a resol-type phenolic resin, the F / P molar ratio used in the primary reaction can be subtracted from the F / P molar ratio range of 2.0 to 2.6 required to obtain the resol-type phenolic resin.

[0034] In addition, the secondary reaction resol type phenolic resin may be produced by referring to the method described in, for example, JP 2018-53131 A.

[0035] [1-4] Alkali catalyst Various alkaline substances can be used as alkaline catalysts for producing resol-type phenolic resins. Specific examples include inorganic alkaline substances and organic alkaline substances. Inorganic alkaline substances include, for example, alkali metal compounds, alkaline earth metal compounds, and ammonia. Alkali metal compounds include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal salts such as sodium carbonate. Alkaline earth metal compounds include hydroxides and oxides of calcium, magnesium, barium, and the like. Organic alkaline substances include, for example, tertiary amines such as triethylamine and trimethylamine, and cyclic amines such as DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.3.0]non-5-ene). These alkaline catalysts may be used alone or in combination.

[0036] The preferred amount of alkali catalyst used to obtain a resol-type phenolic resin may be determined by the molar ratio of alkali catalyst to phenols (hereinafter also referred to as the "alkali / P molar ratio"). The alkali / P molar ratio is preferably 0.1 to 1.0, more preferably 0.2 to 0.9, and even more preferably 0.3 to 0.8. If the alkali / P molar ratio is equal to or greater than the lower limit, the resol-type phenolic resin can be obtained quickly, and if it is equal to or less than the upper limit, the reaction of the resol-type phenolic resin can be easily controlled.

[0037] From another perspective, the preferred amount of alkali catalyst used to obtain a resol-type phenolic resin may be adjusted by assuming an amount that will give a pH of the resol-type phenolic resin of 10.0 to 14.0 at room temperature (25° C.).

[0038] The reaction temperature for obtaining a resol type phenolic resin is preferably 60 to 100° C., more preferably 65 to 90° C. A reaction temperature of 60° C. or higher provides a sufficient reaction rate, while a reaction temperature of 100° C. or lower has the advantage of being easy to control. The reaction time may be, for example, 2 to 8 hours.

[0039] [2] Organic acid ester compounds The wood coating composition contains an organic acid ester compound, which can function as a curing accelerator for the resol phenolic resin. The organic acid produced by hydrolysis of the organic acid ester compound lowers the pH of the wood coating composition, which is thought to accelerate the curing reaction of the resol phenolic resin. For this reason, it is preferable to mix the organic acid ester compound with the resol phenolic resin immediately before applying the wood coating composition.

[0040] Examples of organic acid ester compounds include carbonates such as ethylene carbonate, propylene carbonate, and dimethyl carbonate; lactones such as γ-butyrolactone, α-acetolactone, and β-propiolactone; polyhydric alcohol esters such as triacetin, ethylene glycol diacetate, and triethylene glycol diacetate; monocarboxylic acid esters such as ethyl acetate, methyl butyrate, ethyl butyrate, ethyl formate, methyl salicylate, and ethyl acetoacetate; and polycarboxylic acid esters such as dicarboxylic acid monoesters or dicarboxylic acid diesters such as dimethyl succinate, diethyl succinate, dimethyl adipate, diethyl adipate, dimethyl glutarate, diethyl glutarate, and diethyl malonate. These organic acid esters may be used alone or in combination of two or more.

[0041] Among the above, the organic acid ester compound is preferably at least one selected from the group consisting of dibasic acid esters, triacetin, ethylene glycol diacetate, γ-butyrolactone, ethylene carbonate, and propylene carbonate, and the dibasic acid ester is a mixture of organic acid ester compounds known as DBE, which is a mixture of dimethyl glutarate, dimethyl succinate, and dimethyl adipate. Two or more organic acid ester compounds may be used in combination as necessary, and organic acid esters other than these may also be used in combination.

[0042] In the wood coating composition, the content of the organic acid ester compound is preferably 1.0 to 50.0 parts by weight, more preferably 5.0 to 40.0 parts by weight, and even more preferably 10.0 to 30.0 parts by weight, per 100 parts by weight of the resol phenolic resin. The content of the organic acid ester compound may be adjusted depending on the amount of the wood coating composition used and the temperature at the time of application.

[0043] [3] Other ingredients The wood coating composition may contain other components in addition to the resol phenolic resin and the organic acid ester compound. The other components that may be contained in the wood coating composition are not particularly limited, and examples thereof include various additives, carbohydrates, etc.

[0044] As the additives, known components as constituents of wood coating compositions can be appropriately used, including curing accelerators other than organic acid ester compounds, extenders, thickeners, viscosity modifiers, flame retardants, etc.

[0045] The wood coating composition may contain other curing accelerators such as alkali metal carbonates, such as sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. The wood coating composition may also contain other curing accelerators, such as organic curing accelerators, such as resorcinol.

[0046] Bulking agents include, for example, alkaline earth metal carbonates such as calcium carbonate. Other bulking agents include, for example, wood flour, walnut flour, lignin, tannin, and organic fillers such as blood meal.

[0047] When a wood coating composition contains a carbohydrate, particularly a reducing sugar, the amount of formaldehyde emitted during curing of the wood coating composition or from the cured product can be reduced, and the color tone of the cured product can be lightened.

[0048] The reducing sugar is not particularly limited and may be, for example, a monosaccharide, an oligosaccharide, a dextrin, etc. Here, "oligosaccharide" refers to a compound consisting of 2 to 10 monosaccharides bound together, and "dextrin" includes the general concept of maltodextrin and refers to a sugar composition with a DE of 20 or less. Examples of monosaccharides include glucose, fructose, mannose, galactose, ribose, and xylose.

[0049] Examples of oligosaccharides include disaccharides such as maltose, lactose, isomaltose, etc.; trisaccharides such as maltotriose; and tetrasaccharides or higher oligosaccharides (e.g., maltooligosaccharides, isomaltooligosaccharides, fructooligosaccharides, mannooligosaccharides, galactooligosaccharides, etc.). These reducing sugars may be used alone or in combination of two or more.

[0050] Examples of thickeners include polysaccharides such as wheat flour.

[0051] Examples of viscosity modifiers include high-boiling water-soluble organic solvents such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexylene glycol, and phenoxyethanol.

[0052] Examples of the flame retardant include known flame retardants, such as halogen-based flame retardants such as brominated aromatic compounds, phosphorus-based flame retardants such as phosphate ester compounds, inorganic flame retardants such as aluminum hydroxide, nitrogen-containing compound-based flame retardants such as guanidine compounds, and silicon-based flame retardants. Halogen-based flame retardants may be used in combination with flame retardants such as antimony oxide.

[0053] In addition, the wood coating composition may contain pigments and dyes such as known coloring pigments for imparting design properties to wood.

[0054] <Manufacturing method> The wood coating composition can be prepared by mixing the above-mentioned components, for example, a resol-type phenolic resin, an alkali catalyst, water, an organic acid ester compound, and other components.

[0055] A method for preparing the wood coating composition includes mixing the first and second parts of the wood coating kit described below.

[0056] [Pot life] The pot life of a wood coating composition can be determined by the time (gelation time) from the start of mixing an organic acid ester compound with 50 g of a resol-type phenolic resin adjusted to 20°C until the resol-type phenolic resin gels. Using the gelation time as a guide, the pot life can be adjusted to, for example, about 1 to 60 minutes depending on the type and content of the organic acid ester compound. The pot life may vary depending on factors such as the amount of wood coating composition used, the area to be coated during use, and the temperature during application. Therefore, it is recommended to adjust the type and amount of organic acid ester compound used depending on the amount of wood coating composition used and the temperature during application.

[0057] 〔kit〕 A wood paint kit according to one embodiment of the present invention is a so-called two-component wood paint kit in which the first and second components are packaged separately, and the first and second components may each be housed separately in a container such as a can or a plastic container.

[0058] The first agent preferably contains at least a resol-type phenolic resin, an alkali catalyst, and water. The first agent may also contain other components such as the above-mentioned carbohydrates, reducing sugars, thickeners, viscosity modifiers, flame retardants, and alkali metal carbonates as curing accelerators.

[0059] The resol type phenolic resin, the organic acid ester compound, and other components are as described above, and the preferred embodiments are also the same.

[0060] The pH of the first agent at room temperature (25° C.) is preferably 10.0 to 14.0, more preferably 10.5 to 13.5, and even more preferably 11.0 to 13.0.

[0061] The viscosity of the first part at room temperature (25°C) is preferably 1 to 3,000 mPa·s, more preferably 5 to 2,000 mPa·s, even more preferably 10 to 1,000 mPa·s, particularly preferably 10 to 800 mPa·s, and most preferably 10 to 500 mPa·s.

[0062] The solid content concentration of the resol type phenolic resin contained in the first agent is preferably 20.0 to 60.0% by weight, more preferably 30.0 to 55.0% by weight, and particularly preferably 30.0 to 50.0% by weight.

[0063] The second agent contains at least an organic acid ester compound and may contain other components, such as organic curing accelerators such as resorcinol. When the second agent contains resorcinol, the amount of resorcinol in the second agent is preferably 0.5 to 10.0 parts by weight, more preferably 0.5 to 8.0 parts by weight, even more preferably 0.5 to 7.0 parts by weight, even more preferably 0.5 to 5.5 parts by weight, particularly preferably 1.0 to 5.0 parts by weight, and most preferably 1.5 to 4.5 parts by weight, per 100 parts by weight of the resol phenolic resin in the first agent.

[0064] The preferred content (parts by weight) of the organic acid ester compound in the second part relative to 100 parts by weight of the resol-type phenolic resin in the first part is the same as the preferred content of the organic acid ester compound relative to 100 parts by weight of the resol-type phenolic resin in the wood coating composition. For example, in a wood coating kit, the amount of organic acid ester compound added per 100 parts by weight of the solid content of the resol-type phenolic resin may be adjusted within the range of 1.0 to 50.0 parts by weight to adjust the pot life taking into account the amount of wood coating composition used and the outdoor temperature where the painting work is performed. That is, if a large amount of the first part is used at one time, the amount of the second part may be designed to be less than the amount of the first part. Furthermore, since the pot life becomes shorter the higher the temperature during painting work, the amount of the second part may be reduced, and since the pot life becomes longer the lower the temperature, the amount of the second part may be increased.

[0065] The first and second parts may be mixed appropriately using a stirrer or a stirring rod, etc. The wood coating composition obtained by mixing the first and second parts may be applied by a known coating method, such as painting with a brush or roller, or by spraying or dipping.

[0066] 〔wood〕 Wood coating compositions can be used as coatings, decorative agents, and impregnating agents for wood, and decorative agents and impregnating agents are also embodiments of wood coating compositions. Examples of wood to which the wood coating composition is applied include solid wood and wood materials. Examples of solid wood include birch, paulownia, cedar, cypress, pine, Japanese cypress, sawara, and pine. The solid wood may be in the form of sawn lumber or boards. Examples of wood materials include plywood, glued laminated lumber, cross-laminated lumber, laminated veneer lumber, blockboard, veneer, and wood boards. Examples of wood boards include insulation board (IB), medium-density fiberboard (MDF), hardboard (HB), particleboard, and oriented strand board (OSB).

[0067] 〔summary〕 The wood coating composition according to the first aspect of the present invention contains a resol-type phenolic resin and an organic acid ester compound.

[0068] Furthermore, in the wood coating composition according to Aspect 2 of the present invention, in Aspect 1 above, the aqueous solution of the resol phenolic resin preferably has a pH at 25° C. in the range of 10.0 to 14.0.

[0069] Furthermore, in the wood coating composition according to Aspect 3 of the present invention, in Aspect 1 or 2 above, the aqueous solution of the resol phenolic resin preferably has a viscosity at 25°C within the range of 1 to 3,000 mPa·s.

[0070] Furthermore, in the wood coating composition according to Aspect 4 of the present invention, in any one of Aspects 1 to 3 above, the weight average molecular weight of the resol type phenolic resin is preferably 300 to 8,000.

[0071] Furthermore, in the wood coating composition according to aspect 5 of the present invention, in any of aspects 1 to 4 above, it is preferable that the organic acid ester compound is at least one organic acid ester compound selected from the group consisting of carboxylic acid esters and carbonate esters, and the carboxylic acid ester is at least one carboxylic acid ester selected from the group consisting of monocarboxylic acid esters, polycarboxylic acid esters, polyhydric alcohol esters, and lactones.

[0072] Furthermore, in the wood coating composition according to Aspect 6 of the present invention, in any of Aspects 1 to 5 above, the carbonate ester is preferably at least one carbonate ester selected from the group consisting of ethylene carbonate, propylene carbonate, and dimethyl carbonate; the monocarboxylic acid ester is preferably at least one monocarboxylic acid ester selected from ethyl acetate, methyl butyrate, ethyl butyrate, ethyl formate, methyl salicylate, and ethyl acetoacetate; the polycarboxylic acid ester is preferably at least one polycarboxylic acid ester selected from the group consisting of dimethyl succinate, diethyl succinate, dimethyl adipate, diethyl adipate, dimethyl glutarate, diethyl glutarate, and diethyl malonate; the polyhydric alcohol ester is preferably at least one polyhydric alcohol ester selected from the group consisting of triacetin, ethylene glycol diacetate, and triethylene glycol diacetate; and the lactone is preferably at least one lactone selected from the group consisting of γ-butyrolactone, α-acetolactone, and β-propiolactone.

[0073] Furthermore, in the wood coating composition according to Aspect 7 of the present invention, in any one of Aspects 1 to 6 above, it is preferable that the organic acid ester compound is selected from at least one organic acid ester compound selected from the group consisting of dibasic acid esters, triacetin, ethylene glycol diacetate, γ-butyrolactone, ethylene carbonate, and propylene carbonate, and the dibasic acid ester is a mixture of dimethyl glutarate, dimethyl succinate, and dimethyl adipate.

[0074] Furthermore, in the wood coating composition according to aspect 8 of the present invention, in any of the above aspects 1 to 7, it is preferable that the content of the organic acid ester compound is in the range of 1.0 to 50.0 parts by weight per 100 parts by weight of the resol-type phenolic resin.

[0075] Furthermore, a wood paint kit according to a ninth aspect of the present invention comprises a first agent containing a resol-type phenolic resin and a second agent containing an organic acid ester compound for mixing with the resol-type phenolic resin.

[0076] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0077] An embodiment of the present invention will now be described.

[0078] [1] Measurement method (viscosity measurement) The viscosity of the resol type phenolic resin was measured at 25°C using an E-type viscometer.

[0079] (pH measurement) The pH of the resol type phenolic resin was measured at 25°C using an aqueous solution in which the concentration of the resol type phenolic resin was adjusted with ion-exchanged water to 20.0 to 60.0% by weight.

[0080] (weight average molecular weight measured by GPC) 2 g of sample (phenolic resin) was diluted with 2 g of pure water and 10 g of THF (tetrahydrofuran), and while checking the pH, 1N aqueous hydrochloric acid solution was added to adjust the pH to 4.0. The THF layer and the aqueous layer were separated, and the separated THF layer was diluted 5 times to prepare a sample for GPC measurement. The obtained sample for GPC measurement was subjected to GPC measurement under the following measurement conditions, and the weight average molecular weight in terms of polystyrene was confirmed from the results. Columns: TSKgel G3000HXL 7.8 x 300 mm x 1 (manufactured by Tosoh Corporation), TSKgel G2000HXL 7.8 x 300 mm x 2 (manufactured by Tosoh Corporation). Column temperature: 40°C. Detector: RI (Differential Refractive Index Detector). Solvent: THF (tetrahydrofuran). Flow rate: 0.8mL / min.

[0081] (Solid concentration measurement) An aluminum foil dish (inner diameter 50 mm, height 15 mm) was weighed to a weight C1 (g), and a sample was weighed to a weight of 1.5±0.1 g. The specific weight of the sample was designated as the sample weight S (g) before drying. The aluminum foil dish was placed in an incubator maintained at 135±1°C and dried for 60±2 minutes. After cooling in a desiccator, the sample was weighed to a weight C2 (g). From this result, the sample weight D (g) after drying (the weight of the sample remaining on the aluminum foil dish after drying) was calculated using the following formula (1), and the solids concentration was calculated using the following formula (2). D = C2 - C1 (1) Solid content concentration (wt%)=D / S×100...(2)

[0082] [2] Manufacturing of wood coating compositions (Synthesis of resol-type phenolic resin) A reaction solution was prepared by charging 350 parts of phenol, 506 parts of a 44% aqueous formaldehyde solution, 71 parts of water, and 175 parts of a 25% by weight aqueous sodium hydroxide solution into a reactor equipped with a condenser, thermometer, and stirrer. The reaction was carried out by heating the reaction solution at 85°C for 120 minutes, followed by 45 minutes at 67°C. After heating, the reaction solution was cooled to below 45°C, and 117 parts of a 25% by weight aqueous sodium hydroxide solution, 130 parts of a 48% by weight aqueous potassium hydroxide solution, and 35 parts of water were added. This yielded a resol-type phenolic resin. The formaldehyde / phenol [F / P] molar ratio of the resulting resol-type phenolic resin was 2.0.

[0083] The viscosity of the aqueous solution of the resol-type phenolic resin evaluated under the above measurement conditions was 35 mPa·s at room temperature (approximately 25°C), and the pH of the resol-type phenolic resin was 12. The weight average molecular weight (Mw) of the aqueous solution of the resol type phenolic resin was 1440, and the solid content was 42.7% by weight.

[0084] (Preparation of room temperature curing wood paint samples) Example 1: 20 parts of DBE as an organic acid ester compound was added to 100 parts of the aqueous solution of the resol-type phenolic resin obtained by the synthesis of the resol-type phenolic resin described above, and then the mixture was stirred for 1 minute to obtain room-temperature curing wood coating material sample 1. DBE: A mixture of dimethyl glutarate, dimethyl succinate, and dimethyl adipate in a 60 / 20 / 20 weight ratio, manufactured by Changle Yili Chemicals Co., Ltd. (China) Example 2: 20 parts of triacetin (TACN) as an organic acid ester compound was added to 100 parts of the aqueous solution of the resol-type phenolic resin obtained by the synthesis of the resol-type phenolic resin described above, and then stirred for 1 minute to obtain room-temperature curing wood coating sample 2. Example 3: 20 parts of ethylene glycol diacetate (EGDA) as an organic acid ester compound was added to 100 parts of the aqueous solution of the resol-type phenolic resin obtained by the synthesis of the resol-type phenolic resin described above, and the mixture was stirred for 1 minute to obtain room-temperature curing wood coating sample 3. Example 4: 20 parts of γ-butyrolactone (GBL) as an organic acid ester compound was added to 100 parts of the aqueous solution of the resol-type phenolic resin obtained by the synthesis of the resol-type phenolic resin described above, and the mixture was stirred for 1 minute to obtain room-temperature curing wood coating material sample 4. Example 5: 20 parts of propylene carbonate (PC) as an organic acid ester compound was added to 100 parts of the aqueous solution of the resol-type phenolic resin obtained by the synthesis of the resol-type phenolic resin described above, and the mixture was stirred for 1 minute to obtain room-temperature curing wood coating material sample 5.

[0085] [3] Evaluation [3-1] Evaluation of color difference after application A solid cedar board measuring approximately 15 cm in length, 15 cm in width, and 3 cm in thickness was prepared as the wood for color difference evaluation. A wood paint sample was applied to the wood for color difference evaluation, and a test piece was used to evaluate the color difference after application.

[0086] Examples 1 to 5 Room temperature curing wood paint sample 1 was applied once to one surface of the wood for color difference evaluation using a silicone spatula and allowed to dry, producing wood that had been painted once with wood paint sample 1. The painted wood of Examples 2 to 5 was produced following the same procedure as Example 1, except that paint sample 1 was replaced with one of paint samples 2 to 5.

[0087] (Evaluation of gelation time) An organic acid ester compound was added to a resol-type phenolic resin in the same compounding ratio as in Examples 1 to 5, and the gel time of each paint sample was evaluated when each organic acid ester compound was added. To evaluate the gel time (GT), 50 g of resin adjusted to 20°C was weighed into a cup, a predetermined amount of organic acid ester compound was added to the weighed resin, and the mixture was stirred. The time from immediately after adding the organic acid ester compound until the paint sample in the cup thickened and no longer formed strings was measured.

[0088] (Comparative Example 1) A piece of solid cedar wood measuring approximately 15 cm in length, 15 cm in width, and 3 cm in thickness was used as the wood of Comparative Example 1 for color evaluation.

[0089] (Evaluation of hue) Hue is evaluated using CIE (L * a * b * ) color system was used and evaluation was performed using a color difference meter (Konica Minolta). L indicates lightness, with positive values ​​of the lightness difference indicating increased brightness and negative values ​​indicating increased darkness. Positive values ​​of hue a indicate a reddish hue and negative values ​​indicate a greenish hue, with the larger the absolute value, the stronger the hue. Positive values ​​of hue b indicate a yellowish hue and negative values ​​indicate a blueish hue, with the larger the absolute value, the stronger the hue.

[0090] Table 1 shows the evaluation results of the color of the wood coated with the wood paint samples of Examples 1 to 5 and the wood of Comparative Example 1, as well as the evaluation results of the gel time of the wood paint samples of Examples 1 to 5. [Table 1]

[0091] From the evaluation results of hue shown in Table 1, it can be confirmed that there is no significant change in hue due to differences in the type of organic acid ester compound for each of Examples 1 to 5. The decrease in lightness L of the painted wood of Examples 1 to 5, evaluated using Comparative Example 1 as a control, is considered to be due to a reduction in light scattering by fibers on the wood surface caused by the application of the wood paint sample.

[0092] Furthermore, the gel time evaluation results shown in Table 1 show that gel time decreases in the following order: DBE, TACN, EGDA, GBL, and PC. The wood paint sample using DBE had the longest gel time, confirming that the usable life of the wood paint composition can be extended.

[0093] [3-2] Outdoor exposure test evaluation A piece of solid cedar wood measuring approximately 12cm in length, 12cm in width, and 3cm in thickness was prepared as the lumber for the outdoor exposure test. A wood paint sample was applied to the lumber for the outdoor exposure test to create a test piece for the outdoor exposure test.

[0094] Examples 6 to 9 Example 6: Wood paint sample-1, prepared using the same procedure as in Example 1, was applied once to the entire surface of wood for outdoor exposure testing and allowed to dry to produce the painted wood (painted wood) of Example 6. Example 7: In addition to the painted wood of Example 6, Wood Paint Sample-1 was applied twice to the entire surface of wood for outdoor exposure testing to produce the painted wood of Example 7, which was painted twice with Wood Paint Sample-1. Example 8: Wood paint sample 2 prepared in the same manner as in Example 2 was applied once to the entire surface of wood for outdoor exposure test, followed by drying, to produce the coated wood of Example 8. Example 9: In addition to the painted wood of Example 8, wood paint sample-2 was applied twice to the entire surface of wood for outdoor exposure testing to produce the painted wood of Example 9, which was painted twice with wood paint sample-2.

[0095] (Comparative Example 2) A piece of solid cedar wood measuring approximately 12 cm in length, 12 cm in width, and 3 cm in thickness was used as the unpainted wood of Comparative Example 2 for the outdoor exposure test.

[0096] The painted wood pieces of Examples 6 to 9 and the unpainted wood piece of Comparative Example 2 were exposed to a sunny outdoor location for an outdoor exposure test. In the outdoor exposure test, each piece of wood was fixed so that the approximately 12 cm wide x 12 cm wide side of the piece faced south, and the bottom half of the piece (approximately 6 cm) was buried underground. The outdoor exposure test lasted 13 months. After 3, 9, and 13 months, each piece of wood was removed, the soil was removed, and the difference in brightness, color, and dimensional change between the exposed portion above ground and the buried portion underground were evaluated.

[0097] The evaluation of the hue in the outdoor exposure test was carried out using a color difference meter (manufactured by Konica Minolta) in the same manner as in the evaluation of the hue in Examples 1 to 5 and Comparative Example 1.

[0098] Tables 2 to 4 show the evaluation results of the outdoor exposure test on the painted wood of Examples 6 to 9 and the unpainted wood of Comparative Example 2.

[0099] Table 1 shows the evaluation results of the change in brightness difference between the exposed area (above ground) and the buried area (underground) for the painted wood of Examples 6 to 9 and the unpainted wood of Comparative Example 2, evaluated after 3 months, 9 months, and 13 months of outdoor exposure testing.

[0100] [Table 2]

[0101] The lightness difference evaluation results shown in Table 2 confirm that the painted wood of Examples 6 to 9 showed smaller changes in lightness difference over time than the unpainted wood of Comparative Example 1. Furthermore, the painted wood of Examples 7 and 9, which were painted twice with the wood paint sample, exhibited positive lightness differences compared to the wood of Examples 6 and 8, which were painted once with the wood paint sample, demonstrating that the lightness did not change in a darker direction. Furthermore, the unpainted wood of Comparative Example 2 showed a lightness difference of -10 or less after the evaluation result after 9 months, indicating that it had darkened. This is believed to be due to the fact that the lignin contained in the unpainted wood of Comparative Example 2 was decomposed by ultraviolet rays contained in sunlight, and dirt was adsorbed onto the wood with decomposed lignin, causing it to turn black.

[0102] Table 3 shows the evaluation results of the change in hue a between the exposed area (above ground) and the buried area (underground) for the painted wood of Examples 6 to 9 and the unpainted wood of Comparative Example 2, evaluated 3 months, 9 months, and 13 months after the outdoor exposure test.

[0103] [Table 3]

[0104] From the evaluation results of the change in hue a shown in Table 3, it can be seen that the painted wood of Examples 6 to 9 had a smaller change in hue a, which indicates a red to green color tone, when comparing the exposed part (above ground) and the buried part (underground) than the unpainted wood of Comparative Example 2.

[0105] Table 4 shows the evaluation results of the change in hue b between the exposed area (above ground) and the buried area (underground) for the painted wood of Examples 6 to 9 and the unpainted wood of Comparative Example 2, evaluated after 3 months, 9 months, and 13 months of outdoor exposure testing.

[0106] [Table 4]

[0107] In the evaluation results for changes in hue b shown in Table 4, the painted wood of Examples 6 to 9 showed a change in hue b to a positive value. It is believed that the evaluation results for hue b in Examples 6 to 9 are influenced by the color change due to application of the wood paint samples, as well as by a color change similar to sunburn of the wood caused by the oxidation of lignin that remains in the wood without being decomposed due to protection from UV rays by the wood paint. The color change due to application of the wood paint samples of Examples 6 to 9 can be confirmed by the larger change in hue b of the wood painted twice in Examples 7 and 9 compared to the wood painted once in Examples 6 and 8. Furthermore, in the evaluation results shown in Table 4, the change in hue b of the wood of Comparative Example 2 showed a negative value, which is believed to be due to a decrease in the yellow color caused by the decomposition of lignin when exposed to UV rays.

[0108] (Evaluation of volume change rate) Table 5 shows the volume change rate of wood after 9 months and 13 months of outdoor exposure testing, based on the volume of wood after 3 months of outdoor exposure testing. The volume change rate was calculated from the change in volume calculated by measuring the length, width, and thickness of each piece of wood.

[0109] [Table 5]

[0110] From the evaluation results shown in Table 5, it can be seen that the painted wood materials of Examples 6 to 9 all had a smaller volume change rate than the unpainted wood material of Comparative Example 2.

[0111] FIG. 1 shows the evaluation results of outdoor exposure tests after 13 months for wood coated twice with wood coating sample 2 of Example 7 and wood from Comparative Example 2. The top of FIG. 1 shows a photograph of wood coated twice with wood coating sample 2 of Example 7 (top right) next to a comparison piece of solid wood that was not exposed to the elements (top left) for comparison. The bottom of FIG. 1 shows a photograph of wood from Comparative Example 2 (bottom right) next to a comparison piece of solid wood that was not exposed to the elements (bottom left) for comparison. Compared to the solid wood that was not exposed to the elements, the wood coated twice with wood coating sample 2 of Example 7 (top) has a stronger yellowish tinge due to the coating and discoloration caused by lignin oxidation. In contrast, the wood from Comparative Example 2 (bottom) of FIG. 1 does not show discoloration due to lignin oxidation, but does show dullness due to lignin decomposition and darkening due to stain adsorption. Furthermore, Figure 1 shows that the wood that was painted twice with wood paint sample 2 of Example 7 had no cracks, while cracks occurred in the wood of Comparative Example 2, confirming that applying wood paint sample 2 can prevent cracks that occur in wood over time. [Industrial Applicability]

[0112] The present invention can be used, for example, in paints for coating wood materials such as wood and wood boards used in furniture, woodworking, housing, equipment, and interior and exterior building materials.

Claims

1. A wood coating composition comprising a resol-type phenolic resin and an organic acid ester compound.

2. 2. The wood coating composition according to claim 1, wherein the aqueous solution of the resol-type phenolic resin before mixing with the organic acid ester compound has a pH at 25°C in the range of 10.0 to 14.

0.

3. 2. The wood coating composition according to claim 1, wherein the aqueous solution of the resol phenolic resin has a viscosity at 25°C in the range of 1 to 3,000 mPa·s.

4. 2. The wood coating composition according to claim 1, wherein the resol-type phenolic resin has a weight average molecular weight of 300 to 8,000.

5. the organic acid ester compound is at least one organic acid ester compound selected from the group consisting of carboxylic acid esters and carbonate esters, 2. The wood coating composition according to claim 1, wherein the carboxylic acid ester is at least one carboxylic acid ester selected from the group consisting of monocarboxylic acid esters, polycarboxylic acid esters, polyhydric alcohol esters, and lactones.

6. the carbonate ester is at least one carbonate ester selected from the group consisting of ethylene carbonate, propylene carbonate, and dimethyl carbonate; the monocarboxylic acid ester is at least one monocarboxylic acid ester selected from ethyl acetate, methyl butyrate, ethyl butyrate, ethyl formate, methyl salicylate, and ethyl acetoacetate; the polycarboxylic acid ester is at least one polycarboxylic acid ester selected from the group consisting of dimethyl succinate, diethyl succinate, dimethyl adipate, diethyl adipate, dimethyl glutarate, diethyl glutarate, and diethyl malonate; the polyhydric alcohol ester is at least one polyhydric alcohol ester selected from the group consisting of triacetin, ethylene glycol diacetate, and triethylene glycol diacetate; 6. The wood coating composition according to claim 5, wherein the lactone is at least one lactone selected from the group consisting of γ-butyrolactone, α-acetolactone, and β-propiolactone.

7. the organic acid ester compound is at least one organic acid ester compound selected from the group consisting of dibasic acid esters, triacetin, ethylene glycol diacetate, γ-butyrolactone, ethylene carbonate, and propylene carbonate; 6. The wood coating composition according to claim 5, wherein the dibasic acid ester is a mixture of dimethyl glutarate, dimethyl succinate, and dimethyl adipate.

8. 7. The wood coating composition according to claim 1, wherein the content of the organic acid ester compound is in the range of 1.0 to 50.0 parts by weight per 100 parts by weight of the resol type phenolic resin.

9. a first agent containing a resol-type phenolic resin; and a second agent containing an organic acid ester compound for mixing with the resol-type phenolic resin.

Images