Two-component polyurethane coating composition, coating formed therefrom and coated article

Abstract

The present invention relates to a two-component polyurethane coating composition, a coating formed therefrom, and a coated product. The coating composition of the present invention comprises: a component A, comprising a hydrophilic polyether polyol; and a component B, comprising a polyisocyanate curing agent, wherein the number average molecular weight of the hydrophilic polyether polyol is less than 800 g / mol, and based on the total weight of the component A, the component A comprises 60 wt% or more of the hydrophilic polyether polyol. The present invention also discloses the use of the coating composition in a wood anti-rib primer, wherein the anti-rib primer has the characteristics of high fullness, low VOC, and water washability.

Description

Technical Field

[0001] The present invention relates to the field of wood anti-ribbing, and in particular to a two-component polyurethane coating composition, a coating formed therefrom and a coated product. Background Art

[0002] In recent years, water-based wood coatings have been widely promoted and applied due to their excellent environmental protection characteristics and convenient use, and have gradually replaced traditional organic solvent-based coatings. However, the use of water-based wood coatings in wood products, especially solid wood furniture, is prone to cause rib expansion problems, affecting the appearance and use of wood products. On the one hand, since the surface of wood usually has a capillary porous structure and the wood itself contains moisture, the wood is usually in moisture balance. However, when applying water-based wood coatings, the moisture in the coating penetrates into the wood, destroying the original moisture balance of the wood, causing the ducts and some wood thorns on the surface of the wood to swell, thereby destroying the original flatness of the wood surface. On the other hand, before the wood is painted, in order to achieve a flat surface, the wood is usually polished. However, this process results in a large number of loosely bound wood fibers left on the surface of the wood substrate. These wood fibers tend to protrude from the polished surface when the moisture balance changes, forming a coating with an uneven surface.

[0003] At present, two conventional methods for reducing or eliminating the "bulge" problem include: 1) coating a solvent-based wood sealer (for example, using an alcohol-soluble resin with alcohol and alcohol ether solvents) on a wooden substrate, and then coating a water-based wood paint; and 2) coating a water-based wood paint with ethanol / acetone as a solvent on a wooden substrate. Although method 1) achieves an acceptable anti-bulge effect, it also causes unacceptably high VOC and environmental pollution. The anti-bulge effect of method 2) is insufficient and cannot effectively avoid bulge. Moreover, the fullness of the coating obtained by these two methods is low. In addition, it has also been reported that spraying an aqueous emulsion with a strong wetting ability for wood and a fast drying speed on certain specific woods and combining it with silica sol to improve the anti-bulge effect. However, the anti-bulge effect of this method on different woods varies greatly, especially on softer woods, the effect is not good enough. Moreover, such aqueous emulsions and silica sols are usually expensive and are not suitable for promotion and application in common wood products.

[0004] Therefore, there is still a need in the coatings industry for an anti-beading primer with excellent performance that can reduce or even eliminate the beading problem. Summary of the invention

[0005] The above objectives are achieved by the coating compositions described herein.

[0006] The first aspect of the present application provides a two-component polyurethane coating composition, comprising:

[0007] A component comprising a hydrophilic polyether polyol; and

[0008] Component B, containing polyisocyanate curing agent,

[0009] The number average molecular weight of the hydrophilic polyether polyol is less than 800 g / mol, and the component A comprises 60 wt % or more of the hydrophilic polyether polyol based on the total weight of the component A.

[0010] A second aspect of the present application provides a coating formed from the two-component polyurethane coating composition described herein.

[0011] A third aspect of the present application provides a coated product comprising a wood substrate and the coating composition described herein or a cured coating formed therefrom applied on the substrate.

[0012] The inventors pioneered the use of a relatively large amount of hydrophilic polyether polyols with a small molecular weight in component A of a two-component polyurethane coating composition, replacing the polymer film-forming resin in component A of a conventional two-component polyurethane coating, and successfully applied the composition to wood products. Through a large number of studies and experiments, it was found that the use of the two-component polyurethane coating composition described herein can cause the polyisocyanate curing agent and the hydrophilic polyether polyol contained in the coating composition to react to form a coating film with a cross-linking density. Surprisingly, it was found that this coating film can effectively inhibit or even block the penetration of moisture outside the coating film into the wood, thereby maintaining the original moisture balance on the surface of the wood stable, and effectively reducing or eliminating the problem of wood rib expansion. The two-component polyurethane coating composition of the present application also has the advantages of a wide range of applications and easy washing of coating equipment.

[0013] Moreover, in the coating composition described herein, a polyol with a relatively small molecular weight is used to achieve a better balance between the construction viscosity and VOC, so that the coating composition is not only convenient for construction but also has a relatively low VOC.

[0014] In addition, the coating composition of the present application has a high solid content during construction, and the formed coating film has a significantly higher fullness and better filling performance than traditional water-based products. Therefore, the coating composition of the present application can be applied to applications where solid wood is fully enclosed, as well as applications that require high fullness.

[0015] The inventors also surprisingly found that the coating composition described herein exhibits excellent penetration and wettability after being coated on various wood substrates due to the use of a relatively low molecular weight hydrophilic polyether polyol. Therefore, after crosslinking and curing, a dense and tough crosslinking structure can be formed on the surface of the wood substrate and in the pores on the surface, thereby advantageously fixing the surface of the wood substrate and effectively inhibiting the expansion of tendons. This dense and tough crosslinking structure can also improve the sealing effect on the wood substrate (e.g., oil sealing, water resistance, ethanol resistance, etc.).

[0016] In addition, after curing, the paint film has excellent transparency, thus giving the coating film excellent color development effect. In coating applications that require color (such as furniture color repair), the base color can be reflected very well or the base color can be repaired.

[0017] The details of one or more embodiments of the invention are set forth in the description which follows. Other features, objects, and advantages of the invention will become apparent from the description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] Figure 1 Shown are the film appearances of various coating formulations on rubber wood.

[0020] Figure 2 The figure shows the appearance of the coating film on solid ebony wood using coating formulations with different curing agents. DETAILED DESCRIPTION

[0021] definition

[0022] As used herein, "a", "an", "the", "at least one" and "one or more" and the absence of quantifiers may be used interchangeably unless otherwise indicated. Thus, for example, a coating composition comprising "an" additive may be interpreted to mean that the coating composition comprises "one or more" additives. Unless otherwise indicated herein, the use of the singular form herein is intended to include the plural form.

[0023] Where a composition is described as comprising or including specific components, it is contemplated that optional components not contemplated by the present invention are not excluded from the composition, and that the composition may consist of or be composed of the contemplated components. Alternatively, where a method is described as comprising or including specific process steps, it is contemplated that optional process steps not contemplated by the present invention are not excluded from the method, and that the method may consist of or be composed of the contemplated process steps.

[0024] For simplicity, only some numerical ranges are explicitly disclosed herein. However, it should be understood that any range formed by combining any lower limit with any upper limit belongs to the content explicitly disclosed in the present invention; any range formed by combining any lower limit with other lower limits also belongs to the content explicitly disclosed in the present invention. Similarly, any range formed by combining any upper limit with other upper limits also belongs to the content explicitly disclosed in the present invention.

[0025] Unless otherwise indicated, each point or single value between the endpoints of a range is included in the range. For example, a range of 1 to 5 includes the values ​​1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. Moreover, a disclosed numerical range includes all subset ranges within the broader range, for example, a range of 1 to 5 includes subranges 1 to 4, 1.5 to 4.5, 1 to 2, etc. Thus, each point or single value can be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits, and the resulting range belongs to the content clearly disclosed in the present invention.

[0026] When used in the context of "a coating composition is coated on a substrate" or similar expressions, the term "on..." includes the coating composition being coated directly or indirectly on the substrate. For example, one or more other coatings (such as a coating formed from an aqueous coating composition, a colorant layer) may be directly coated on the anti-bead coating, and these other coatings are in direct or indirect contact with the anti-bead coating. These coatings as well as the anti-bead coating may all be considered to be "coated on a substrate".

[0027] The term "film-forming resin" refers to a polymer compound that can form a continuous paint film or coating under certain conditions. It can be natural or synthetic, and can be physically formed by solvent volatilization or chemically formed by chemical cross-linking reaction. Chemical film-forming film-forming resins are further divided into: resins that form films by reacting with curing agents, and self-cross-linking film-forming resins. Common film-forming resins include: phenolic resins, amino resins, alkyd resins, epoxy resins, polyester resins, acrylic resins, etc. In this article, the "polyisocyanate" used in the present invention is usually used as a curing agent in the field of coatings, so a single polyisocyanate does not belong to a film-forming resin.

[0028] As used herein, the term "application viscosity" refers to the viscosity at which the coating composition can be applied normally without sagging or unapplicable application problems.

[0029] As used herein, the term "construction solid content" or "construction solid content" refers to the content of non-volatile matter contained in the coating composition when it can be normally applied, which is usually measured after baking in an atmospheric oven at 150°C for 1 hour. Usually, during the construction process, if the mixture obtained after mixing the components of the coating composition is too viscous, a diluent or solvent needs to be added to dilute it to meet the construction requirements. Therefore, the construction solid content is usually lower than the solid content of the coating composition itself.

[0030] When used in relation to a "two-component" coating composition, the term "usable time" refers to the time taken for the viscosity of the system to reach twice its initial viscosity after the two components of the two-component coating composition are mixed and then allowed to stand at room temperature of 35±1°C.

[0031] As used herein, the term "volatile organic compound (VOC)" refers to any carbon-containing compound that participates in atmospheric photochemical reactions, except carbon monoxide, carbon dioxide, carbonic acid, metal carbides or carbonates. Typically, volatile organic compounds have a vapor pressure of 0.1 mm Hg or higher. As used herein, "volatile organic compound content (VOC content)" refers to the weight of VOCs per volume of a composition or coating composition, for example reported as g / L.

[0032] When used in the context of a wood substrate, the term "primary surface" is the surface formed by the length and width dimensions of the wood substrate for providing a decoration.

[0033] In the context of polyisocyanates, "water stability time" refers to the time it takes for the remaining NCO group content (i.e., NCO%) to decrease to 80% of the initial content after the water-dispersible polyisocyanate is mixed with water or dispersed in water. Generally, after the polyisocyanate is dispersed and contacted with water, the NCO group will slowly react with water, causing the NCO group to gradually decrease. The "water stability time" herein can measure the stability of the water-dispersible polyisocyanate in water.

[0034] The terms "including," "having," "comprising," "containing," and variations thereof are not intended to be limiting, but rather are intended to be open ended when these terms appear in the description and claims.

[0035] The terms "preferred" and "preferably" refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the recitation of one or more preferred embodiments does not mean that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present invention.

[0036] Composition

[0037] The two-component polyurethane coating composition according to the first aspect of the present invention comprises: a component A comprising a hydrophilic polyether polyol; and a component B comprising a polyisocyanate curing agent, wherein the number average molecular weight of the hydrophilic polyether polyol is less than 800 g / mol, and based on the total weight of the component A, the component A comprises 60 wt% or more of the hydrophilic polyether polyol.

[0038] It can be seen that in the two-component polyurethane coating composition of the present application, component A contains a relatively large amount of hydrophilic polyether polyol with a relatively small molecular weight. This is significantly different from conventional two-component polyurethane coatings. In conventional two-component polyurethane coatings, the polymer film-forming resin usually constitutes the main part of component A and mainly participates in the cross-linking reaction during the curing process to form a coating film. In this article, the hydrophilic polyether polyol has a relatively small molecular weight and should not be understood as a "resin" in the traditional sense.

[0039] In component A, the molecular weight of the hydrophilic polyether polyol is relatively small. In some preferred embodiments, the number average molecular weight of the hydrophilic polyether polyol is less than 700g / mol. In some more preferred embodiments, the number average molecular weight of the hydrophilic polyether polyol is in the range of 200 to 600g / mol. For example, the number average molecular weight of the hydrophilic polyether polyol can be about 250g / mol, 280g / mol, 300g / mol, 350g / mol, 400g / mol, 450g / mol, 500g / mol or 550g / mol. When the number average molecular weight of the hydrophilic polyether polyol is too small, the drying speed of the coating film is slow. The inventors found through experiments that, while maintaining considerable coating properties such as anti-rib expansion, the reaction speed of PEG400 is faster than PEG200, and the reaction speed of PEG600 is faster than PEG400. Therefore, the desired reaction speed can be adjusted to a certain extent by changing the number average molecular weight of the hydrophilic polyether polyol. In addition, a hydrophilic polyether polyol with too small a molecular weight may be counted as a VOC component, resulting in a higher VOC value of the coating composition. When the number average molecular weight of the hydrophilic polyether polyol is too high, the viscosity of the polyol itself increases, and it may even be solid at room temperature and pressure, and a larger amount of co-solvent is required accordingly, which may also lead to an increase in the VOC value of the coating composition.

[0040] The hydrophilic polyether polyol can be a difunctional hydrophilic polyether polyol, a trifunctional hydrophilic polyether polyol or a combination thereof. Preferably, the hydroxyl value of the hydrophilic polyether polyol is about 150 mg KOH / g, 180 mg KOH / g, 200 mg KOH / g, 220 mg KOH / g, 240 mg KOH / g, 600 mg KOH / g, 500 mg KOH / g, 480 mg KOH / g, 450 mg KOH / g, 400 mg KOH / g, 350 mg KOH / g or 300 mg KOH / g, or a range consisting of the above values ​​as upper and lower limits. For example, the hydroxyl value of the hydrophilic polyether polyol can be in the range of 150 to 600 mg KOH / g.

[0041] Hydrophilic polyether polyols can be obtained in a conventional manner. For example, hydrophilic polyether polyols can be obtained by alkoxylating a suitable initiator with an alkylene oxide. The alkylene oxide can be, for example, ethylene oxide, propylene oxide, butylene oxide or any mixture thereof. Examples of initiators include water, ammonia, aniline or polyols such as diols with a molecular weight of 62-200 g / mol, particularly alkane polyols such as ethylene glycol, propylene glycol, hexamethylene glycol, glycerol, trimethylolpropane or trimethylolethane or low molecular weight alcohols such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol or butanediol comprising an ether group. Preferably, the initiator comprises two reactive functional groups, i.e. diols.

[0042] In some embodiments, the hydrophilic polyether polyol is one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), polyethylene oxide-propylene oxide glycol. More preferably, the hydrophilic polyether polyol comprises one or both of polyethylene glycol and polypropylene glycol. For example, the hydrophilic polyether polyol comprises polyethylene glycol. These polyols are conventional materials prepared by conventional methods. The catalysis of this polymerization can be anionic or cationic, using catalysts such as KOH, CsOH, boron trifluoride or dicyano complex catalysts (DMC) such as hexacyanocobaltate zinc or quaternary phosphazenium compounds. In the case of alkaline catalysts, these alkaline catalysts are preferably removed from the polyols by appropriate treatment steps (such as condensation, magnesium silicate separation or acid neutralization) at the end of production.

[0043] Based on the total weight of component A, component A contains 60% by weight or more of the hydrophilic polyether polyol. Preferably, based on the total weight of component A, the amount of the hydrophilic polyether polyol is 65% by weight or more, more preferably 70% by weight or more, even more preferably 75% by weight or more. Preferably, based on the total weight of component A, the amount of the hydrophilic polyether polyol is 98% by weight or less, more preferably 95% by weight or less, even more preferably 90% by weight or less. For example, based on the total weight of component A, the amount of the hydrophilic polyether polyol is about 80% by weight or about 85% by weight.

[0044] In some embodiments, component A may further include a cosolvent. Suitable cosolvents are cosolvents for conventional coating compositions that can promote the dissolution of polyether polyols, such as esters, ethers, ketones, and the like. Examples of suitable cosolvents include, but are not limited to, ethyl acetate, butyl acetate, ethylene glycol monomethyl or monoethyl ether acetate, 1-methoxy-2-propyl acetate, 3-methoxy-n-butyl acetate, diethylene glycol butyl ether, propylene glycol methyl ether, acetone, 2-butanone, 4-methyl-2-pentanone, cyclohexanone, toluene, xylene, chlorobenzene, petroleum solvents (e.g., naphtha, (Deutsche EXXON CHEMICAL GmbH, Cologne, DE) and (Deutsche Shell Chemie GmbH, Eschborn, DE)), carbonates (such as dimethyl carbonate, diethyl carbonate, 1,2-ethylene carbonate and 1,2-propylene carbonate), lactones (such as β-propiolactone, γ-butyrolactone, ε-caprolactone and ε-methylcaprolactone), as well as propylene glycol diacetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, 1,3-dioxolane, N-methylpyrrolidone and N-methylcaprolactam, or any mixture thereof.

[0045] Preferably, the cosolvent is selected from one or more of ethyl acetate, butyl acetate, xylene, toluene, propylene glycol methyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, N-methyl pyrrolidone, ethylene glycol monobutyl ether, acetone and butanone. More preferably, the cosolvent is selected from one or more of xylene and propylene glycol methyl ether acetate. In some embodiments, the cosolvent is propylene glycol methyl ether acetate.

[0046] Suitable co-solvents include ethers, esters, alkanes, substituted hydrocarbons or any combination thereof. As examples of suitable co-solvents, diethylene glycol butyl ether, propylene glycol methyl ether or a combination thereof can be used.

[0047] In some embodiments, the coating composition or component A of the present invention further comprises one or more of acrylic resin, polyester polyol, polyolefin polyol, and castor oil.

[0048] In some embodiments, the coating composition or A component of the present invention may optionally further include other additional additives commonly used in coating compositions, which do not adversely affect the coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those agents that improve the processing properties or manufacturing properties of the composition, enhance the aesthetics of the composition, or improve the specific functional properties or characteristics (such as adhesion to the substrate) of the coating composition or the cured composition obtained therefrom. The additives that may be included are, for example, selected from one or more of chain extenders, adhesion promoters, curing promoters, open time regulators, pigments, fillers, surfactants, lubricants, defoamers, dispersants, UV absorbers, colorants, coalescing agents, thixotropic agents, antioxidants, stabilizers, preservatives and bactericides, thereby providing the desired film properties as required. The content of each optional component is preferably sufficient to achieve its intended purpose, but will not adversely affect the coating composition or the cured coating obtained therefrom.

[0049] In some preferred embodiments, the two-component polyurethane coating composition comprises one or more of a chain extender, a wetting agent, and a defoaming agent.

[0050] Suitable wetting agents can include ionic wetting agents, nonionic wetting agents or multifunctional wetting agents. As examples of commercially available wetting agents, BYK349 ​​purchased from BYK Company, Germany, Dispers 715W, Dispers 740W, Dispers 760W, Disperbyk194 purchased from Tego Company, Germany, or SURFYNOL 104-BC of Air Chemistry can be used.

[0051] Suitable defoamers include organosiloxane defoamers, polyether defoamers, polyether-modified organosilicon defoamers or any combination thereof. As examples of commercially available defoamers, BYK 024, BYK 025, BYK-1660, BYK 037 from BYK, Germany, and TEGO foamex 810 from EVONIK can be used.

[0052] In some embodiments, the total amount of additional additives is in the range of about 5 wt % to about 25 wt % relative to the total weight of the coating composition. In some embodiments, the amount of additional additives is in the range of 7-20 wt % relative to the total weight of the coating composition.

[0053] In some preferred embodiments, based on the total weight of component A, component A comprises:

[0054] 60 to 90 wt%, more preferably 70 to 85 wt% of a hydrophilic polyether polyol;

[0055] 5 to 20 wt%, more preferably 7 to 15 wt% of a chain extender;

[0056] 0.1 to 5 wt %, more preferably 1 to 3 wt % of a silicone surfactant;

[0057] 0.1 to 3 wt%, more preferably 0.5 to 2 wt% of a defoaming agent;

[0058] 0.5 to 10 wt %, more preferably 4 to 8 wt % of other additives.

[0059] The A component of the present invention can be prepared by any suitable method known to those skilled in the art. For example, the A component can be prepared by the following steps: adding the ingredients (including, for example, polyols, wetting agents, defoamers, cosolvents and the like) into a container, and then stirring the resulting mixture.

[0060] In the coating composition described herein, component B comprises a polyisocyanate as a curing agent. The term "polyisocyanate" as used herein refers to a polyisocyanate compound, a polyisocyanate oligomer or a combination thereof, which contains two or more isocyanate functional groups (NCO) that can undergo chain extension and crosslinking reactions with active hydrogen to form a three-dimensional network structure.

[0061] Suitable polyisocyanates include aliphatic or alicyclic polyisocyanates, aromatic polyisocyanates or any combination thereof. The term "aliphatic or alicyclic polyisocyanates" refers to a compound having two or more NCO functional groups in its molecular skeleton, and the NCO functional group is connected to an aliphatic or alicyclic group, wherein the NCO functional group is directly connected to the methyl group of the benzyl group and is considered to be connected to the aliphatic group. The term "aromatic polyisocyanate" refers to a compound having two or more NCO functional groups in its molecular skeleton, and the NCO group is directly connected to an aromatic ring. In some preferred embodiments of the present invention, polyisocyanates are aliphatic or alicyclic polyisocyanates.

[0062] As examples of suitable polyisocyanate compounds, polyisocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), bis[isocyanatocyclohexyl]methane (HMDI), xylylene diisocyanate (XDI), tetramethylene-m-xylene diisocyanate (TMXDI), hexahydrotoluene diisocyanate (HTDI), cyclohexane-1,4-diisocyanate, 4,4'- Dicyclohexylmethane diisocyanate, cyclopentane-1,3-diisocyanate, p-phenylene diisocyanate, toluene diisocyanate (TDI), naphthalene-1,4-diisocyanate, biphenyl-4,4'-diisocyanate, benzene-1,2,4-triisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, diphenylmethane diisocyanate, butane-1,2,3-triisocyanate or polymethylene polyphenyl polyisocyanate, dimers or trimers thereof, derivatives thereof or any combination thereof.

[0063] As an example of a suitable isocyanate oligomer, a polyurethane prepolymer of any polyisocyanate compound listed above, a polyester prepolymer of any polyisocyanate compound listed above, or a polyether prepolymer of any polyisocyanate compound listed above and any combination thereof can be used. Polyurethane prepolymers (e.g., hexamethylene diisocyanate (HDI) trimer), polyester prepolymers, or polyether prepolymers can be made by any suitable method known to those of ordinary skill in the art. For example, a polyurethane prepolymer can be made by reacting a polyol monomer with one or more of a polyisocyanate compound under suitable conditions; a polyester prepolymer or a polyether prepolymer can be made by reacting a polyester polyol or a polyether polyol with one or more of a polyisocyanate compound under suitable conditions. Alternatively, any suitable commercial product can be used as a polyurethane prepolymer, a polyester prepolymer, or a polyether prepolymer. In some preferred embodiments of the present invention, the polyisocyanate includes a hexamethylene diisocyanate (HDI) trimer.

[0064] In some preferred embodiments, the polyisocyanate is water-dispersible. Preferably, the water-dispersible polyisocyanate is a hydrophilic group-modified and / or at least partially hydrophilic group-modified polyisocyanate, more preferably a hydrophilic group-modified polyisocyanate.

[0065] In some embodiments, the water-dispersible polyisocyanate is derived from the group consisting of 1,4-butane diisocyanate, 1,5-pentane diisocyanate, hexamethylene diisocyanate (HDI), 1,10-decane diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (HMDI), cyclopentane-1,3-diisocyanate, isophorone diisocyanate (IPDI), dimers or trimers thereof, derivatives thereof, and any combination thereof, preferably derived from one or more of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dimers or trimers thereof.

[0066] In some embodiments, the hydrophilically modified polyisocyanate is nonionic hydrophilically modified or ionic hydrophilically modified, preferably ionic hydrophilically modified. Nonionic modification generally uses polyether polyols, and hydrophilic groups are introduced into the polyisocyanate through the reaction of carbamate to achieve a certain hydrophilicity. Ionic modification generally uses cationic substances (such as quaternary ammonium salts, pyridinium salts, imidazole salts) or anionic substances (such as carboxylates, sulfonates, phosphates) for carrying out. Mixed modification uses the above two methods.

[0067] Preferably, the water-dispersible polyisocyanate has one or more hydrophilic groups. In some embodiments of the present invention, the hydrophilic group may be in the form of an acid, such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, a phosphite group, etc. Additionally, in view of the stability of the system, a portion of the hydrophilic group may be in the form of an acid salt, such as a neutralized acid or anhydride. Examples of suitable hydrophilic groups in the form of an acid salt include carboxylate (-CO2 - ), sulfate, phosphate, sulfonate, phosphite, phosphonate and combinations thereof. In a preferred embodiment of the present invention, the hydrophilic group comprises not only anionic hydrophilic groups in acid form, but also anionic hydrophilic groups in acid salt form. Preferably, the water-dispersible polyisocyanate contains a sulfonate group or is sulfonic acid-modified. In some preferred embodiments, the polyisocyanate comprises sulfonic acid-modified HDI.

[0068] In some embodiments, the content of NCO functional groups in the polyisocyanate curing agent (also referred to as "NCO%" or "NCO content") is in the range of 10% to 25% by weight. Preferably, the NCO content in the polyisocyanate curing agent is 23% or less, more preferably 22% or less. Preferably, the NCO content in the polyisocyanate curing agent is 12% or more, more preferably 13% or more.

[0069] In addition, the inventors also note that the content of NCO functional groups in polyisocyanates, i.e., weight percentage, has an impact on the reaction rate with hydroxyl groups. Considering the demand for reaction rate in practical applications, it is preferred to use polyisocyanates with lower weight percentage of NCO functional groups. In some embodiments of the present invention, the curing agent includes polyisocyanates with NCO functional group content lower than 18% by weight, preferably polyisocyanates with NCO functional group content lower than 17% by weight. However, under the same dosage and other conditions, some polyisocyanates with too low NCO functional group content may show relatively high viscosity, even cause particle problems, and increase construction difficulty. Therefore, in some preferred embodiments, the preferred range described above is adopted. The content of the NCO functional group is determined by titration experiments.

[0070] Preferably, the curing agent has a solid content of 70-100 wt %, more preferably 75-100 wt %. In some embodiments, the curing agent has a solid content of about 78-90 wt %. In other embodiments, the curing agent has a solid content of 95 wt % or more, or up to 100 wt %.

[0071] The inventors have found that the stability or compatibility of polyisocyanates in water or commonly used coating solvents is generally very important for the properties of the coating composition and the performance of the paint film. In some embodiments, preferably, the polyisocyanate can be miscible with polyether polyols (especially PEG, PPG) within a larger usage ratio range. More preferably, the polyisocyanate can be miscible with alcohol solvents such as alcohol, or stably present in alcohol solvents such as alcohol. The above-mentioned preferred polyisocyanates can promote the stability of the coating system during construction and avoid particle problems.

[0072] Without being bound by any theory, generally, after the water-dispersible polyisocyanate is dispersed in water, the NCO group will still react slowly with water, and the number of NCO groups will gradually decrease. In the present application, the time taken for the remaining NCO group content (i.e., NCO%) to be reduced to 80% of the initial content after the water-dispersible polyisocyanate is mixed with water is used to measure the stability of the water-dispersible polyisocyanate in water, which is called the water stability time. The "water stability time" can more appropriately measure the stability of the water-dispersible polyisocyanate in water and the effective reactivity of the isocyanate group and the hydroxyl group. In some embodiments of the present invention, the water stability time of the water-dispersible polyisocyanate is more than 6 hours, preferably more than 7 hours, more preferably more than 8 hours, and particularly preferably more than 10 hours. It is not expected to be limited by theory, and the polyisocyanate with the water stability time in the above range can enable the polyisocyanate to retain more NCO groups while maintaining a stable structure for a longer time in water or other solvents. On the one hand, this is beneficial to controlling the reaction process of the NCO group and the hydroxyl group, avoiding excessive reaction, and is beneficial to forming a dense paint film in the pores; on the other hand, it is beneficial to forming a stable coating system and avoiding coagulation, sedimentation or particle formation during construction.

[0073] Optionally, the coating composition according to the invention may also contain a suitable solvent which is inert towards isocyanate groups. Examples of suitable solvents are solvents for conventional coating compositions known per se, such as ethyl acetate, butyl acetate, ethylene glycol monomethyl or monoethyl ether acetate, 1-methoxy-2-propyl acetate, 3-methoxy-n-butyl acetate, acetone, 2-butanone, 4-methyl-2-pentanone, cyclohexanone, toluene, xylene, chlorobenzene, white spirits (for example in the form of solvent naphtha, (Deutsche EXXON CHEMICAL GmbH, Cologne, DE) and (Deutsche Shell Chemie GmbH, Eschborn, DE)), carbonates (such as dimethyl carbonate, diethyl carbonate, 1,2-ethylene carbonate and 1,2-propylene carbonate), lactones (such as β-propiolactone, γ-butyrolactone, ε-caprolactone and ε-methylcaprolactone), as well as propylene glycol diacetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, 1,3-dioxolane, N-methylpyrrolidone and N-methylcaprolactam, or any mixture of such solvents.

[0074] Preferably, the solvent is selected from one or more of ethyl acetate, butyl acetate, xylene, toluene, propylene glycol methyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, N-methyl pyrrolidone, ethylene glycol monobutyl ether, acetone and butanone. More preferably, the solvent is selected from one or more of xylene and propylene glycol methyl ether acetate. In some embodiments, the solvent is propylene glycol methyl ether acetate.

[0075] In some embodiments, the weight ratio of component A to component B is in the range of 1:1.5 to 1:5. Preferably, the weight ratio of component A to component B is 1:1.5 or lower, more preferably 1:2 or lower, and even more preferably 1:2.5 or lower. Preferably, the weight ratio of component A to component B is 1:4.5 or higher, more preferably 1:4 or higher, and even more preferably 1:3.5 or higher. Particularly preferably, the weight ratio of component A to component B may be about 1:3. The inventors have found that in the coating composition, an appropriate excess of polyisocyanate curing agent can cause the hydroxyl groups on the surface of the wood to react with the curing agent, thereby improving the adhesion of the coating to the wood and the water resistance of the upper water-based product, thereby further improving the anti-bulking effect of the overall coating.

[0076] In some embodiments, the NCO / OH equivalent ratio of the two-component polyurethane coating composition is in the range of 1:0.1 to 1:0.7. Preferably, the weight ratio of component A to component B is 1:0.2 or less, more preferably 1:0.3 or less, even more preferably 1:0.35 or less. Preferably, the weight ratio of component A to component B is 1:0.6 or more, more preferably 1:0.5 or more, even more preferably 1:0.45 or more. Particularly preferably, the NCO / OH equivalent ratio is about 1:0.4.

[0077] In order to further improve the anti-beading effect, the two-component polyurethane coating composition described herein may contain a very small amount of water, preferably substantially free of water, or even completely free of water. Based on the total weight of the two-component polyurethane coating, the two-component polyurethane coating composition contains 0 to 3 wt % of water. Preferably, the amount of water added does not exceed 2 wt %, more preferably does not exceed 1 wt %. Nevertheless, it is not excluded that each raw material may contain trace amounts of water. It is particularly preferred that water is not added separately.

[0078] The compositions described herein have very low VOC. Preferably, the VOC of the two-component polyurethane coating composition is no higher than 300 g / L.

[0079] During construction, component A and component B can be mixed, and the resulting mixture can be used for construction. In some preferred embodiments, after component A and component B are mixed, the resulting coating composition is clear and transparent.

[0080] In some preferred embodiments, after mixing the A component and the B component, the resulting mixture has a usable time of 2.5 hours or more. Preferably, the coating composition described herein has a usable time of 3 hours or more.

[0081] In some embodiments, the two-component polyurethane coating composition may have a construction solid content greater than 50% by weight. In some preferred embodiments, the two-component polyurethane coating composition according to the present invention may have a construction solid content of 70-90% by weight, especially 75-85% by weight. Thus, the coating film formed by the coating composition described herein has a much higher fullness than traditional water-based products. This is very unexpected.

[0082] For the convenience of construction, the two-component polyurethane coating composition may have a suitable viscosity. Preferably, the construction viscosity of the two-component polyurethane coating composition is in the range of 30 to 70 seconds (DIN 4#, 23°C). In some embodiments, the viscosity is in the range of 35 to 60 seconds (DIN 4#, 23°C). The means and instruments for measuring the viscosity may be known in the art or commercially available. For example, the viscosity may be tested according to ISO 2431 (also known as the DIN viscosity cup method).

[0083] The inventors have found through extensive research and experiments that a combination of a low molecular weight hydrophilic polyether polyol and a polyisocyanate curing agent can form a cross-linked three-dimensional structure on the wood surface, thereby effectively inhibiting or even blocking the penetration of moisture outside the coating into the wood. The coating composition described herein can effectively maintain the original moisture balance on the wood surface, greatly reducing or eliminating the problem of wood ribs. In particular, this two-component polyurethane coating composition is particularly suitable for use as a closed primer for woodware, and is used to form an anti-rib coating for a wood substrate.

[0084] Moreover, in the coating composition described herein, component A containing hydrophilic polyether polyol and water-dispersible isocyanate are used as component B. Both have very good compatibility and construction tolerance, and the transparency of the dry film is excellent. After the two are mixed, they have excellent water solubility, and equipment and tools can be directly cleaned with water, so they have good environmental protection.

[0085] In addition, as mentioned above, the coating composition according to the present invention can have a construction solid content greater than 50 wt %, or even greater than 75 wt %, which has obvious advantages over traditional water-based sealing primers (20 wt % to 40 wt %), and the dry film has better filling properties.

[0086] When using the coating composition described herein, various methods can be used to mix the components. In some embodiments, the method of using the coating composition includes: before application, simply mixing the curing agent and the resin composition in a mixing device at a predetermined weight percentage. Optionally, a suitable colorant is added to the two-component coating composition obtained above to obtain a desired color.

[0087] The resulting mixture of coating compositions can be applied using a variety of methods familiar to those skilled in the art, including spraying (e.g., air-assisted, airless or electrostatic spraying), brushing, flooding and dipping. In some embodiments, the mixed coating composition is applied by spraying.

[0088] The coating composition of the present invention can be applied to various wet film thicknesses. In some embodiments, the coating amount of the two-component polyurethane coating composition is 30-100 g / m 2 In the range of 50-90g / m 2 In the range of 60-80 g / m 2 The applied coating may be cured by air drying or by accelerating the curing by using various drying devices familiar to those skilled in the art (e.g., oven). The applied coating may be cured by air drying or by accelerating the curing by using various drying devices familiar to those skilled in the art (e.g., oven).

[0089] Therefore, the second aspect of the present application relates to a coating (or cured coating) formed from the coating composition described herein. In the present invention, the two-component polyurethane coating composition can be used as it is, applied to a substrate to form a coating, preferably as a primer layer in direct contact with the substrate.

[0090] A third aspect of the present invention provides a coated article comprising: a wooden substrate; and a coating described herein or a cured coating formed by the coating composition described herein applied to the wooden substrate. The coating composition described herein can be applied to one or more surfaces or one or more regions of the substrate. In some embodiments, the coated article comprises (a) a wooden substrate having at least one major surface; (b) a coating formed by the coating composition described herein directly applied to the major surface of the wooden substrate.

[0091] The coating or cured coating described herein may be applied one or more times as desired. In some preferred embodiments, the coating or cured coating described herein is applied once or twice on the wood substrate.

[0092] In some embodiments, on the surface of the cured coating (especially closed primer layer) formed by the coating composition described herein, one or more coatings formed by the aqueous coating composition can be applied.Therefore, in some embodiments, the coating on the substrate can include a primer layer, an intermediate coating, a topcoat or a combination thereof.In some embodiments, one or more colorant layers can also be present between the coating formed by the aqueous coating composition and the cured coating formed by the coating composition described herein, thereby obtaining the color desired.

[0093] According to the present invention, two or more coating layers formed from an aqueous coating composition can be applied on a coating layer formed from the coating composition described herein, preferably three or more coating layers formed from an aqueous coating composition can be applied, and more preferably 4 or more coating layers formed from an aqueous coating composition can be applied without affecting the swelling effect of the article.

[0094] As wooden substrate for producing the coated article, any suitable wooden substrate known in the art may be used. According to the present invention, the wooden substrate has at least one, preferably two, main surfaces opposite to each other.

[0095] Preferably, the main surface of the wooden substrate may have polar groups such as hydroxyl, amino, and thiol, so that when the coating composition described herein is applied thereto, the polyisocyanate in the coating composition can easily wet the surface and react with the groups (especially hydroxyl), thereby forming a coating with excellent adhesion on the substrate surface and improving the barrier effect and anti-bulge effect of the coating. Methods for obtaining a main surface with hydroxyl groups on the wooden substrate are known in the art. Specifically, hydroxyl groups can be introduced on the surface of the wooden substrate by surface treatment of the main surface of the wooden substrate, such as oxidation by corona treatment.

[0096] According to the present invention, the wooden substrate comprises softwood or hardwood or its combination.As the example of softwood, rubber wood, pine (such as white pine and southern yellow pine), fir or cypress can be used.As the example of hardwood, ebony, ash, ash, basswood, elm, maple, birch, alder, beech, oak (such as white oak and red oak), cherry, walnut, teak or redwood can be used.In some embodiments of the present invention, solid ebony wood board is used as wooden substrate.

[0097] In some embodiments, the article of the present invention can be prepared, for example, by the following steps: (1) providing a sanded wood substrate; (2) applying the two-component polyurethane coating composition of the present invention to the wood substrate by a spraying process to form a sealer primer layer; (3) applying one or more desired coating layers formed of an aqueous coating composition on the sealer primer layer in sequence by a wet-to-dry coating process. Optionally, a colorant can be applied to the sealer primer layer before step (3) to provide the wood substrate with a desired color.

[0098] According to the present invention, the articles thus obtained can be used in the following applications, including, but not limited to: household furniture, such as tables, chairs, cabinets, etc.; bedroom and bathroom furniture; office furniture; custom furniture, such as school and children's furniture, hospital furniture, restaurant and hotel furniture, kitchen cabinets and furniture; panels for interior design; indoor and outdoor windows and doors; indoor and outdoor window frames and door frames; outdoor and indoor wainscoting and wood flooring.

[0099] Example

[0100] The disclosed content of the present invention is described in more detail by the following examples. These examples are only for exemplary description. Embodiments of the present invention are not limited to these specific examples. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on weight. Moreover, unless otherwise stated, the reagents used in the examples are all commercially available and can be directly used without further processing. Those skilled in the art can easily purchase or prepare the raw materials used in the examples.

[0101] Test Method

[0102] Viscosity: The viscosity of the composition was measured using the DIN viscosity cup method according to ISO 2431. The viscosity was measured using a fully filled BYK-Gardner Din viscosity cup #4 at 25°C and was measured in seconds (s).

[0103] Sandable time: the time when the paint film does not stick to the sandpaper after sanding. At 40℃ or 20℃, with a dry layer thickness of 25-50mm, sand with 180# sandpaper and record the time when the paint film does not stick to the sandpaper.

[0104] Transparency: Use a 100μm applicator to evenly scrape the test sample onto the glass plate. After drying at room temperature for 15 minutes, place the glass plate coated with the sample in a 40℃ oven to dry for 1 hour. Then take it out to cool, and visually judge the transparency, which is divided into three levels: "good", "average", and "poor". In the rating level, "good" means transparent, "average" means visually observable decrease in transparency or slight whitening of the coating, and "poor" means severe whitening of the coating or hazy texture of the substrate.

[0105] Stretching test:

[0106] (1) Material preparation: Take solid pine or ebony wood and use #240 sandpaper to remove the surface burrs;

[0107] (2) Sample preparation: Use a spray gun to evenly spray the test sample on the material, with a wet film coating amount of 75-100 g / m2. After drying naturally for 15 minutes, place the material coated with the test sample in a 40°C oven for 1 hour. Then take it out to cool, visually and touch the surface of the coating to judge the surface bulging and penetration performance. The anti-bulging performance is divided into three levels: "no bulging", "slight bulging", and "obvious bulging" (no bulging - the coating surface is smooth, and the material tube has no bulging; slight bulging - the coating surface has a slight granular feeling, and the material tube is slightly bulged; obvious bulging - the coating surface is rough, and the material tube is severely bulged). The penetration performance is divided into three levels: "good", "average", and "poor".

[0108] Solid content: The solid content is determined by the percentage of the weight of the remaining components measured after the sample is baked in a normal pressure oven at 150°C for 1 hour to the initial weight.

[0109] Construction solid content: The construction sample is obtained by diluting the sample with a certain amount of water or solvent, and then the construction sample is measured according to the test method for testing solid content.

[0110] VOC content: measured according to standard HJ2537-2014.

[0111] Material

[0112] Primer WK1000B of Guangdong China Resources Paint Co., Ltd.: a commercially available alcohol-soluble product.

[0113] Primer WK8000B of Guangdong China Resources Paint Co., Ltd.: a commercially available water-based coating composition containing nano-silica sol.

[0114] Sherwin-Williams Primer EL8510B: A commercially available water-based primer.

[0115] Cosolvent: dipropylene glycol methyl ether (DPM).

[0116] Hydrophilic polyether polyols: PEG200, PEG400 and PEG600 purchased from DOW.

[0117] Curing agent #1: DIC 5500, a sulfonate-modified HDI-based water-dispersible aliphatic polyisocyanate with an NCO content of 13-14%, dissolved in dipropylene glycol methyl ether at 80% by weight;

[0118] Curing agent 2#: Covestro 2655, a water-dispersible aliphatic polyisocyanate based on HDI, with an NCO content of 20.7-21.7%;

[0119] Curing agent 3#: Covestro 2487, HDI-based water-dispersible aliphatic polyisocyanate, NCO content 20±1%;

[0120] Curing agent 4#: Covestro 401-60, a hydrophilic modified aliphatic polyisocyanate based on IPDI, with an NCO content of about 8.5%.

[0121] Treating wood substrates

[0122] Rubberwood or ebony wood boards purchased from the timber market were kiln dried. Samples with a size of 15 cm*15 cm*1.5 cm were cut from the dried boards and placed under conditions of 25°C, 60% relative humidity (RH) and 1.8 m / s air flow to a constant weight, wherein the equilibrium moisture content of the sample was 11%. A strip sander was used to grind the sample through a 3M T The samples were sanded with Utility Cloth Sheet 180 grit sandpaper and cleaned with an air pressure gun.

[0123] Example 1: Preparation of two-component polyurethane coating composition and screening of curing agent

[0124] According to the amounts shown in Table 1 below, mix the ingredients to prepare component A, which is used as the main agent.

[0125] Table 1

[0126]

[0127] The A component prepared above was used, and the curing agent shown in Table 2 below was used as the B component, and the two were mixed in the weight ratio of A:B shown in Table 2. The properties of the mixture were tested, and the test results are shown in Table 2.

[0128] Table 2

[0129]

[0130] From the experimental results in Table 2, it can be seen that the use of DIC 5500 curing agent and 1:2 A:B weight ratio in sample 2 has achieved very excellent construction performance. Therefore, by selecting the appropriate curing agent and A:B weight ratio, the viscosity, sandable time, and usable time of the coating system can be adjusted to obtain a formula suitable for construction.

[0131] Example 2: Coating performance test

[0132] Solid rubber wood was used as the wood substrate and processed as described above.

[0133] As shown in Table 3 below, component A and component B were mixed and diluted with DPM to obtain sample 7 suitable for construction. The construction viscosity of sample 7 was about 40 seconds and the usable time was 3 hours.

[0134] Then, the sample 7 was sprayed on the treated rubber wood solid wood and dried in air for 15 minutes, in an oven at 40° C. for 1 hour, and then cooled in air for 30 minutes, and then the anti-rib expansion effect was determined by visual inspection.

[0135] Table 3-2 below summarizes the coating formulations and their anti-rib expansion effects on solid rubber wood.

[0136] Table 3: Formulation of Sample 7

[0137]

[0138]

[0139] Table 4 Coating properties and construction performance

[0140] WK1000B WK8000B EL8510B Sample 7 transparency good generally generally good Anti-bulge ability No swelling Slight muscle swelling Obvious muscle swelling No swelling Hole entry performance good generally good good VOC(g / L) >300 <80 <300 <300 Construction solid content (weight %) 25％ 36％ 32％ 76％ Water washing coating equipment easy Very easy Very easy Very easy

[0141] As shown in Table 4, the coating composition of the present invention can simultaneously achieve excellent anti-beading effect and low VOC, achieving performance comparable to that of solvent-based high-VOC coating compositions. It is worth noting that the samples of the present invention also achieved construction solids of up to 76% by weight and even up to 81% by weight.

[0142] Figure 1Photos of cured coatings of various different coating compositions on real rubber wood are shown. Although the anti-rib expansion results of WK8000B and EL8510B may not be very clear in the photos, the inventors confirm that the rib expansion effect observed by human eyes and touched by hand on the actual test board is relatively clear. Touching the coating of EL8510B with your hand, you can feel that the surface is a bit rough, and you can see that the wood ducts are slightly bulging visually. The surface texture of the wood substrate is severely damaged, and the texture is blurred in the photo. WK8000B is second. Samples 7 and WK1000B have smooth surfaces, and the wood ducts are not bulging visually. In addition, the surface texture of the wood substrate is very well preserved, and the texture is clear and complete in the photo.

[0143] In order to test the performance of different curing agents, curing agents 1# and 2# were used on ebony wood, and the coating effects of spraying once and spraying twice were tested. Except for the curing agent, the other components and amounts of the coating composition were consistent with those of sample 7. Figure 2 shown.

[0144] from Figure 2 It can be seen that the use of curing agent 1# and 2# both achieved good anti-bulking effect and transparency. In addition, the inventor also found during the experiment that the drying speed when using curing agent 1# is faster than when using curing agent 2#.

[0145] Example 3: Polyether polyols with different molecular weights

[0146] To test the effect of different molecular weight polyether polyols, the experiment of sample 7 was repeated except that different molecular weight polyether polyols were used. The formulation, coating properties and application performance are shown in Table 5 below.

[0147] Table 5

[0148]

[0149] It can be seen from Table 5 that under the same experimental conditions, the use of polyether polyols with a molecular weight within the preferred range of this article can achieve excellent results, including good transparency, no swelling, good penetration performance, low VOC, higher construction solid content, and the coating equipment is very easy to wash, etc.

[0150] Moreover, the inventors have also found that the reaction speed of PEG400 is faster than that of PEG200, and the reaction speed of PEG600 is faster than that of PEG 400. Therefore, by changing the number average molecular weight of the hydrophilic polyether polyol, the reaction speed can be appropriately adjusted to meet the requirements of specific applications.

[0151] Although the present invention is described with reference to a large number of embodiments and examples, it is easy for those skilled in the art to see that the present invention can be changed without departing from the principles disclosed in the foregoing description. For example, without departing from the principles disclosed in the foregoing description, a plurality of features or preferred modes described herein are combined, and the resulting technical solutions should be understood to belong to the contents recorded herein. Such changes are deemed to be included in the following claims, unless the claims explicitly indicate otherwise. Accordingly, the embodiments described in detail herein are merely exemplary and are not intended to limit the scope of the present invention, which is the full scope of the attached claims and any and all equivalents thereof.

Claims

1. A coated article comprising: Wood substrates; and The anti-rib expansion coating is applied on the wooden substrate, wherein the anti-rib expansion coating is formed by a two-component polyurethane coating composition, and the two-component polyurethane coating composition comprises: A component comprising a hydrophilic polyether polyol; and Component B, containing polyisocyanate curing agent, The number average molecular weight of the hydrophilic polyether polyol is less than 800 g / mol, the hydrophilic polyether polyol is one or more of polyethylene glycol, polypropylene glycol, and polyethylene oxide-propylene oxide glycol, and based on the total weight of the A component, the A component contains 70 weight % or more and 95 weight % or less of the hydrophilic polyether polyol, the construction solid content of the two-component polyurethane coating composition is 75-85 weight %, and the two-component polyurethane coating composition does not contain water. 2 . The coated article according to claim 1 , wherein the number average molecular weight of the hydrophilic polyether polyol is in the range of 200 to 600 g / mol. 3 . The coated article according to claim 1 , wherein the hydrophilic polyether polyol has a hydroxyl value in the range of 150 to 600 mgKOH / g. 4 . The coated article according to claim 1 , wherein the hydrophilic polyether polyol comprises one or both of polyethylene glycol and polypropylene glycol.

5. The coated article according to claim 1, wherein the polyisocyanate curing agent comprises a water-dispersible aliphatic or alicyclic polyisocyanate. 6 . The coated article according to claim 1 , wherein the polyisocyanate curing agent has a water stability time of 6 hours or more.

7. The coated article according to claim 1, wherein the polyisocyanate curing agent has a water stability time of 7 hours or more.

8. The coated article according to claim 1, wherein the polyisocyanate curing agent has a water stability time of 8 hours or more.

9. The coated article according to any one of claims 1 to 5, wherein a weight ratio of the A component to the B component is in the range of 1:1.5 to 1:

5.

10. The coated product according to any one of claims 1 to 5, wherein the component A further comprises one or more of acrylic resin, polyester polyol, polyolefin polyol, and castor oil.

11. The coated article according to any one of claims 1 to 5, wherein the application viscosity of the two-component polyurethane coating composition measured at 23°C using DIN#4 is in the range of 30 to 70 seconds.

12. The coated article according to any one of claims 1 to 5, wherein based on the total weight of the A component, the A component comprises 70 to 90 wt % of the hydrophilic polyether polyol; 5 to 20 wt % of a chain extender; 0.1 wt % to 5 wt % of a silicone surfactant; 0.1 to 3 wt % of a defoaming agent; 0.5 to 10 wt% of other additives.

13. The coated product according to any one of claims 1 to 5, wherein The VOC of the two-component polyurethane coating composition is not higher than 300 g / L.

14. Use of a two-component polyurethane coating composition for improving the anti-ribbing performance and fullness of a coating and the water washability of a coating equipment, the two-component polyurethane coating composition comprising: A component comprising a hydrophilic polyether polyol; and Component B, containing polyisocyanate curing agent, The number average molecular weight of the hydrophilic polyether polyol is less than 800 g / mol, the hydrophilic polyether polyol is one or more of polyethylene glycol, polypropylene glycol, and polyethylene oxide-propylene oxide glycol, and based on the total weight of the A component, the A component contains 70 weight % or more and 95 weight % or less of the hydrophilic polyether polyol, the construction solid content of the two-component polyurethane coating composition is 75-85 weight %, and the two-component polyurethane coating composition does not contain water.

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