Aqueous wood coating composition and wood product made therefrom

Abstract

The present application relates to a waterborne wood coating composition and a wood product made therefrom. The waterborne wood coating composition comprises i) a waterborne base paint comprising an aqueous dispersion of polymeric particles and optionally additional additives including pigments and fillers, co-solvents, thickeners, leveling agents, defoamers or any combination thereof, ii) an oligomeric siloxane having one or more functional groups that can be hydrolytically removed small molecules, wherein the paint film formed by the waterborne wood coating composition has a 60 degree gloss no higher than 40.

Description

TECHNICAL FIELD

[0001] The present invention relates to a waterborne wood coating composition, more particularly to a waterborne wood coating composition capable of forming a paint film with low gloss, even a matte, and a wood product made therefrom. BACKGROUND

[0002] Currently, environment and energy are two major challenges faced by people, in order to cope with this challenge, the coating industry is gradually shifting from traditional varieties with high pollution, high energy consumption and extreme dependence on products of oil industry to environmentally friendly and resource-saving products such as waterborne coatings, radiation-curable coatings, powder coatings and high solid coatings. With the introduction of the Chinese "waterborne wood coatings for indoor use" chemical industry standard, waterborne wood coatings have developed rapidly. At present, the research and development investment in waterborne wood coatings is increasing substantially, and people's requirements for waterborne wood coatings are also increasing.

[0003] In the wood coating market, low gloss or matte paint film is favored by the majority of consumers because of its soft gloss and delicate touch. At present, in the production of low gloss waterborne wood coatings, the known matting scheme is to apply inorganic matting agents such as silicon dioxide or organic matting agents such as synthetic wax or metal stearate in waterborne wood coatings. These matting agents are mainly physical matting, and inorganic matting agents based on silicon dioxide can cause the paint film to form a microscopically rough paint film surface after the paint is dried, thereby producing a gloss reduction effect or even a matte effect; organic matting agents based on synthetic wax can float on the outermost surface to modify the paint film after the paint is dried, thereby affecting the gloss of the paint film. However, these known matting agents have some shortcomings more or less. From the cost point of view, the application of silicon dioxide inorganic matting agent in the preparation of waterborne wood matte paint is the most convenient. However, this matting method has the disadvantages of powder sedimentation, poor paint film touch and poor transparency. The application of organic matting agents such as synthetic wax and metal stearate in the preparation of waterborne wood matte paint is not so widespread, and has the defects of high cost or insufficient performance.

[0004] Therefore, there is an urgent need in the coating industry for improved waterborne wood coatings capable of forming a paint film with low gloss, even a matte. SUMMARY

[0005] The present invention provides a waterborne wood coating composition comprising i) a waterborne base paint comprising an aqueous dispersion of polymeric particles and optionally additional additives including pigments and fillers, co-solvents, thickeners, leveling agents, defoamers or any combination thereof, ii) an oligomeric siloxane having one or more functional groups that can be hydrolytically removed small molecules, wherein the paint film formed by the waterborne wood coating composition has a 60-degree gloss of not higher than 40.

[0006] In some embodiments of the present application, the waterborne base paint included in the waterborne wood coating composition comprises an aqueous dispersion of polymeric particles having one or more active hydrogen functional groups.

[0007] In some embodiments of the present application, the oligomeric siloxane included in the waterborne wood coating composition comprises one or more segments having active hydrogen reactive functional groups in addition to having one or more hydrolytically removable small molecule functional groups. In this embodiment, the oligomeric siloxane can have the following general structure 1:

[0008]

[0009] wherein

[0010] at least one of R1, R2, R3, R4, R5, R6is a hydrolytically removable small molecule functional group selected from one or more of C1-C6alkoxy, C2-C6alkenyloxy, C6-C 10 aryloxy, C1-C6alkanoyloxy, C6-C 10 aroyloxy, C1-C6alkanone oxime, and C6-C 10 alkanone oxime, preferably C1-C6alkoxy; and

[0011] at least one of R1, R2, R3, R4, R5, R6is a segment bearing an active hydrogen reactive functional group selected from one or more of epoxy, hydroxyl, amino, and isocyanate, preferably epoxy; and

[0012] m is not 0, preferably an integer from 1 to 10.

[0013] In other embodiments of the present application, the oligomeric siloxane included in the waterborne wood coating composition comprises two or more segments having active hydrogen reactive functional groups in addition to having one or more hydrolytically removable small molecule functional groups. In this embodiment, the oligomeric siloxane can have the following general structure 2:

[0014]

[0015] R A represents a hydrolytically removable small molecule functional group selected from one or more of C1-C6alkoxy, C2-C6alkenyloxy, C6-C 10 aryloxy, C1-C6alkanoyloxy, C6-C 10 aroyloxy, C1-C6alkanone oxime, and C6-C 10 alkanone oxime, preferably C1-C6alkoxy; and

[0016] R B represents a segment with a reactive functional group of active hydrogen selected from one or more of epoxy, hydroxyl, amino and isocyanate, preferably from epoxy; and

[0017] m is not 0, preferably an integer from 1 to 10.

[0018] In some embodiments of the present application, the oligosiloxane contained in the waterborne wood coating composition is water-insoluble.

[0019] Another aspect of the present application provides a wood product comprising a wood substrate having at least one major surface; and at least one paint film formed from the waterborne wood coating composition of the present application coated directly or indirectly on the major surface.

[0020] The inventors of the present application surprisingly found that in the formulation of the waterborne wood coating composition, the addition of the oligosiloxane having one or more functional groups of hydrolytically removable small molecules into the waterborne base paint, the waterborne wood coating composition thus obtained can achieve a chemically generated matt effect, thereby forming a paint film with reduced gloss or even a matte paint film.

[0021] The inventors of the present application more surprisingly found that in the formulation of the waterborne wood coating composition, the incorporation of the oligosiloxane containing one or more segments with reactive functional groups of active hydrogen, preferably two or more segments with reactive functional groups of active hydrogen, in addition to having one or more functional groups of hydrolytically removable small molecules, combined with the waterborne base paint containing a waterborne dispersion of polymer particles having reactive functional groups of active hydrogen, the oligosiloxane not only can achieve a chemically generated matt effect, promoting the formation of a paint film with reduced gloss or even a matte paint film, but also can participate in the film-forming process of the paint film, thereby improving the paint film performance, such as the chemical resistance of the paint film, especially the alkali resistance of the paint film.

[0022] The details of one or more embodiments of the application are set forth in the description below. Other features, objects, and advantages of the application will be apparent from the description and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The coating surface of the paint film formed by the waterborne wood coating composition according to Example 2 of the present application and the waterborne base paint of Control Sample 1 is shown for electron microscopy analysis, wherein the left picture is the paint film of Control Sample 1 and the right picture is the paint film according to Example 2 of the present application.

[0024] Figure 2The infrared spectra of the coatings formed from the water-borne wood coating composition according to Example 2 of the present application, the oligomeric siloxane incorporated into the water-borne wood coating composition of Example 2 and the water-borne base paint of Comparative Sample 1 are shown using Fourier Transform Attenuated Total Reflection Infrared Spectroscopy, wherein the top curve is the coating of Comparative Sample 1, the middle curve is the coating of the oligomeric siloxane and the bottom curve is the coating according to Example 2 of the present application.

[0025] Definitions

[0026] As used herein, "a", "an", "the", "at least one", and "one or more" are used interchangeably. Thus, for example, a component comprising "a" additive can be interpreted to mean that the component includes "one or more" additives.

[0027] Where compositions are described as including, consisting of, or consisting essentially of, particular components, it is understood that the compositions can also optionally include other components in addition to the ones listed n the specification, and that the compositions can be composed of or consist of the listed components, or, where methods are described as including particular process steps, it is understood that the methods can also include other steps in addition to the ones listed in the specification, and that the methods can be composed of or consist of the listed steps.

[0028] For convenience, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with any other lower limit to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. Further, although ranges are expressly recited, any point or individual value within the range can also be claimed as the lower or upper limit, or as the lower or upper limit of another range not explicitly recited. Further, even though individual values are expressly recited, every point or individual value within the range can be claimed as the lower or upper limit, or as the lower or upper limit of another range not explicitly recited.

[0029] As used herein, "coating" and "paint film" have the same meaning and refer to the film formed after the water-borne wood coating composition is applied and dried.

[0030] As used herein in connection with "water-borne wood coating composition", the phrase "the paint film formed from the water-borne wood coating composition has a 60 degree gloss no higher than 40" means that the paint film formed from the water-borne wood coating composition shows a low gloss effect, and thus the water-borne wood coating composition can also be referred to as a low gloss water-borne wood coating composition.

[0031] In the context of the present application, the term "oligomeric siloxane" refers to a class of oligomers having a backbone of repeating Si-O linkages with organic groups directly attached to the silicon atoms, where the organic groups can include alkyl, aryl, alkoxy, aryloxy, or other organic groups known to those skilled in the art.

[0032] The term "one or more hydrolytically removable small molecule functional groups" when used in reference to "oligomeric siloxane" refers to functional groups that are directly attached to a silicon atom on the oligomeric siloxane backbone and that can undergo hydrolysis in the presence of an aqueous medium to form a small molecule that can be removed from the system, such as a volatile small molecule. By way of illustrative example, the hydrolytically removable small molecules include, but are not limited to, alcohols, carboxylic acids, oximes, water, and the like.

[0033] The term "water insoluble" when used in reference to "oligomeric siloxane" means that the oligomeric siloxane does not uniformly disperse at the molecular scale in an aqueous medium, such as water, to form a homogeneous solution. In some embodiments of the present application, the oligomeric siloxane can disperse in water in the form of nanoparticles, whereby the resulting dispersion is optically clear and clear and transparent, or can disperse in water in the form of microparticles, whereby the resulting dispersion is not optically clear or is semi-optically clear and hazy.

[0034] In the context of the present application, the term "flatting powder" includes silica flatting agents, synthetic wax flatting agents, and stearate flatting agents. The term "substantially free of flatting powder" when used in reference to "an aqueous wood coating composition" means that the individual components of the aqueous wood coating composition and the coating composition as formulated do not contain any additional added flatting powder of the type described above, and preferably do not contain any flatting powder known in the art. When the phrase "substantially free of" is used herein, such phrase is not intended to exclude the presence of trace amounts of the relevant flatting powder that can be present as or due to environmental contamination.

[0035] The terms "oligomer" or "oligomeric" as used herein refer to a structure that generally comprises a relatively small number of repeating units, either actually or conceptually derived from molecules of relatively low molecular weight. Typically, in an oligomer, the addition or removal of even one repeating unit from the oligomer will have an effect on the properties of the resulting oligomer.

[0036] The terms "comprising," "including," and "having" and variations thereof herein are inclusive and not exclusive.

[0037] The terms "preferred" and "preferably" refer to embodiments of the application that can provide certain benefits under certain circumstances. However, other embodiments can also be preferred under the same or other circumstances. Additionally, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude those other embodiments from the scope of the application. DETAILED DESCRIPTION

[0038] One aspect of the present application provides an aqueous wood coating composition comprising i) an aqueous base paint comprising an aqueous dispersion of polymeric particles and optionally additional additives including pigments and fillers, co-solvents, thickeners, leveling agents, defoamers, or any combination thereof, ii) an oligomeric siloxane having one or more functional groups that can be hydrolytically removed small molecules, wherein the paint film formed from the aqueous wood coating composition has a 60 degree gloss no higher than 40.

[0039] As described above, the aqueous wood coating composition according to the present application can form a paint film having a 60 degree gloss no higher than 40, and thus the aqueous wood coating composition according to the present application can also be referred to as a low gloss aqueous wood coating composition. Preferably, the paint film formed from the aqueous wood coating composition according to the present application preferably has a 60 degree gloss no higher than 35, more preferably no higher than 30, still more preferably no higher than 25, even still more preferably no higher than 20. Thus, the preferred aqueous wood coating composition according to the present application can also be referred to as a matte aqueous wood coating composition.

[0040] In embodiments according to the present application, the aqueous wood coating composition comprises an oligomeric siloxane, which component is present in the aqueous wood coating composition as a separate component in a distinguishable form. In the context of the present application, "oligomeric siloxane" refers to a class of oligomers having a backbone of repeating Si-O linkages with direct attachment of organic groups to the silicon atoms, where the organic groups can include alkyl, aryl, alkoxy, aryloxy, or other organic groups known to those skilled in the art.

[0041] In embodiments according to the present application, the oligosiloxane can have one or more functional groups that can hydrolytically eliminate small molecules. As mentioned above, these functional groups are directly attached to silicon atoms of the oligosiloxane backbone and can undergo hydrolysis in the presence of an aqueous medium, thereby allowing the elimination of small molecules, such as volatile small molecules. The formation of these small molecules causes the formation of pits on the surface of the paint film formed from the aqueous wood coating composition comprising the oligosiloxane, resulting in a rough surface. As suitable examples of hydrolytically-eliminable small molecule functional groups, one can cite hydroxyl groups, alkoxy groups, alkenyloxy groups, aryloxy groups, alkylacyloxy groups, arylacyloxy groups, alkylketoxime groups, arylketoxime groups. By way of illustrative example, the hydrolytically-eliminable small molecules include, but are not limited to, alcohols, carboxylic acids, oximes, water, and the like.

[0042] In order to more clearly illustrate the hydrolytic elimination of small molecules by the oligosiloxane during the film formation process of the paint, several illustrative schemes are provided below:

[0043] Process 1 : =Si-OR + 3H2O → =Si-OH + 3ROH↑;

[0044] Process 2: =Si-OH + HO-Si= → =Si-O-Si= + H2O;

[0045] Process 3: =Si-OR + HO-Si= → =Si-O-Si= + ROH;

[0046] Process 4: Polymer particle-OH + HO-Si / RO-Si= → =Si-O-Si= + H2O / ROH.

[0047] As shown by the above schemes of hydrolytic elimination of small molecules, during the film formation process of the aqueous wood coating composition, the oligosiloxane comprising one or more functional groups that can hydrolytically eliminate small molecules can hydrolyze to form volatile small molecules (e.g. alcohols), and / or can itself condense to form water molecules or volatile small molecules, and / or can react with the hydroxyl groups present in the polymer particles to form water molecules or volatile small molecules. In some embodiments of the present application, the hydroxyl groups present in the polymer particles are introduced by ring-opening reaction of a polymer particle having carboxylic acid functional groups with an oligosiloxane having epoxy functional groups, thereby introducing hydroxyl groups in the polymer particles. During the formation of the paint film, one or more of the above processes of hydrolytic elimination of small molecules can occur simultaneously or sequentially.

[0048] The inventors of the present application surprisingly found that incorporation of the above oligosiloxane having one or more functional groups capable of hydrolytically removing small molecules into an aqueous base paint makes it possible to obtain an aqueous wood coating composition having low gloss, and even an aqueous wood coating composition having a matte effect. Without being bound by any theory, the inventors of the present application believe that, compared with small molecule silanes, the hydrolysis of the oligosiloxane having one or more hydrolyzable functional groups is a much slower process, and the volatile small molecules formed are continuously released in the form of bubbles, rise to the surface of the paint film, and then break to form pits, resulting in a rough surface of the paint film; moreover, the oligosiloxane also undergoes self-condensation into silicone microparticles during the hydrolysis process, and the silicone microparticles formed have a lower surface tension than the surrounding resin, thus causing pits in the paint film and a rough surface of the paint film. Under the synergistic effect of the above two, the oligosiloxane can effectively reduce the gloss of the paint film, and thus can be used to formulate an aqueous wood coating composition having reduced gloss or a matte effect.

[0049] In an embodiment of the present application, the oligosiloxane further comprises one or more segments having a reactive functional group with active hydrogen. The incorporation of such an oligosiloxane makes it possible not only to bring about a matting effect to the paint film, but also to participate in the formation of the paint film through crosslinking reaction, thus improving the mechanical properties of the paint film.

[0050] In this embodiment, as an illustrative example, the oligosiloxane has a structure represented by general formula 1:

[0051]

[0052] wherein

[0053] at least one of R1, R2, R3, R4, R5, and R6 is a functional group capable of hydrolytically removing small molecules, and the functional group capable of hydrolytically removing small molecules is selected from one or more of C1-C6 alkoxy, C2-C6 alkenyloxy, C6-C 10 aryloxy, C1-C6 alkanoyloxy, C6-C 10 aroyloxy, C1-C6 alkanone oxime, and C6-C 10 alkanone oxime, preferably C1-C6 alkoxy; and

[0054] at least one of R1, R2, R3, R4, R5, and R6 is a segment having a reactive functional group with active hydrogen, and the reactive functional group with active hydrogen is selected from one or more of epoxy, hydroxyl, amino, and isocyanate, preferably epoxy; and

[0055] m is not 0, and is preferably an integer from 1 to 10.

[0056] In another embodiment of the present application, the oligosiloxane further has two or more segments with a reactive functional group with a reactive hydrogen. The incorporation of such oligosiloxane makes it possible for the oligosiloxane to bring about not only a matting effect to the paint film, but also multiple functional groups that can crosslink with the polymer particles, so that the resulting paint film can have improved chemical resistance, in particular, improved alkali resistance.

[0057] In this embodiment, as an illustrative example, the oligosiloxane has a structure represented by general formula 2:

[0058]

[0059] R A represents a hydrolytically removable small molecule functional group selected from one or more of C1-C6 alkoxy, C2-C6 alkenyloxy, C6-C 10 aryloxy, C1-C6 alkanoyloxy, C6-C 10 aroyloxy, C1-C6 alkylketoximo, and C6-C 10 arylketoximo, preferably C1-C6 alkoxy; and

[0060] R B represents a segment with a reactive functional group with a reactive hydrogen selected from one or more of epoxy, hydroxyl, amino, and isocyanate, preferably epoxy; and

[0061] m is not 0, preferably an integer from 1 to 10.

[0062] In some embodiments according to the present application, the oligosiloxane is water-insoluble or water-difficultly soluble. The inventors of the present application have surprisingly found that such solubility characteristics of the oligosiloxane in an aqueous medium are particularly advantageous for the formation of roughness on the surface of the paint film. Therefore, in a preferred embodiment of the present application, the oligosiloxane can be dispersed in the form of nanoparticles or microparticles in an aqueous medium, preferably in an aqueous base paint.

[0063] The above-mentioned oligosiloxane is either self-made or commercially available. As an illustrative example, COATOSIL MP-200 commercially available from MEGHIT, or JH-OP17 commercially available from Jiangxi Jianghan Fine Chemical Co., Ltd. can be used.

[0064] According to embodiments of the present application, the amount of oligosiloxane can vary within a suitable range as desired. In some embodiments according to the present application, the oligosiloxane can be present in an amount of 1 to 10 wt%, preferably in an amount of 3 to 10 wt%, more preferably in an amount of 4 to 10 wt%, even more preferably in an amount of 4 to 8 wt%, relative to the total weight of the aqueous base paint. The oligosiloxane within the above amount range is suitable for reducing the gloss of the aqueous wood coating composition and improving the chemical resistance of the paint film formed by the aqueous wood coating composition.

[0065] In embodiments according to the present application, the aqueous wood coating composition comprises an aqueous base paint in addition to the oligosiloxane. The aqueous base paint, as the main component of the aqueous wood coating composition, comprises conventional components for formulating the aqueous wood coating composition, including but not limited to, an aqueous dispersion of polymer particles, water, additional additives, and the like.

[0066] In embodiments of the present application, the aqueous base paint comprises an aqueous dispersion of polymer particles. As used herein, the term "aqueous dispersion of polymer particles" refers to a stable dispersion of synthetic resin (i.e., polymer) in the form of microparticles in an aqueous liquid medium, optionally with the aid of suitable dispersing aids such as surfactants. Thus, the terms "aqueous latex" and "aqueous dispersion" can be used interchangeably in the present application when used in relation to a polymer, unless otherwise stated. Methods of preparing aqueous latex are known in the art, for example, can be prepared using emulsion polymerization processes known to those skilled in the art. The emulsion polymerization preparation process generally comprises the steps of dispersing polymerizable monomers in water in the form of an emulsion, optionally under the action of suitable emulsifiers and / or dispersion stabilizers, and initiating the polymerization of the monomers, for example, by adding an initiator, with the aid of stirring.

[0067] It is generally known that the polymer particles in the aqueous latex can be modified to obtain an aqueous latex having desired properties. In one embodiment of the present application, the polymer particles are modified by active hydrogen functional groups. In one aspect, the active hydrogen can be provided by functional groups such as -COOH, -OH, -SH, secondary amino groups, and primary amino groups. In addition, some functional groups, for example, ester groups (especially carboxylate groups), thioether groups, or anhydride groups (especially carboxylic anhydride groups) can be converted, for example, by hydrolysis, into functional groups capable of providing active hydrogen. Thus, in the present application, polymer particles having one or more active hydrogen functional groups refer to any polymer particles that contain functional groups capable of providing active hydrogen as such and / or contain any polymer particles that can be converted into functional groups capable of providing active hydrogen during the preparation and / or application of the system.

[0068] In embodiments according to the present application, the aqueous dispersion of polymer particles having one or more active hydrogen functional groups is considered as the film- forming resin component in the aqueous base paint. On the one hand, this resin component acts as a binder for providing adhesion of the paint film to the substrate and for holding the components in the aqueous base paint, such as fillers, together and imparting a certain cohesive strength to the paint film. On the other hand, this polymer particle has a good reactivity with the oligomeric siloxane having active hydrogen reactive functional groups, thus enabling crosslinking of the polymer chains, thereby forming a paint film coating having a three-dimensional network structure.

[0069] In some embodiments of the present application, the polymer particles in the aqueous latex can have one or more active hydrogen functional groups selected from the group consisting of -COOH, -OH, -SH, secondary amino groups and primary amino groups, preferably carboxyl functionalized.

[0070] In some preferred embodiments of the present application, the aqueous dispersion of polymer particles comprises an aqueous dispersion of a vinyl acetate-based resin, an aqueous dispersion of an acrylic resin, an aqueous dispersion of a silicone-based resin, an aqueous dispersion of a polyurethane-based resin, an aqueous dispersion of a polyurethane polyacrylic resin, an aqueous dispersion of a fluoropolymer-based resin, or any combination thereof.

[0071] In embodiments according to the present application, the polymer particles in the aqueous dispersion have a certain range of particle size, which can be measured by the Z-average particle size, as known in the art, referring to the size of the particles determined by dynamic light scattering method, for example, using a Malvern Zetasizer 3000HS Microsizer. Preferably, the polymer particles in the aqueous dispersion can have a particle size in the range of 50 nm to 200 nm. The inventors of the present application surprisingly found that the aqueous dispersion of polymer particles having the above-mentioned particle size range is particularly suitable for formulating aqueous wood coating compositions, and the wood coating compositions formulated therefrom have suitable rheology and coatability.

[0072] In embodiments of the present application, the aqueous dispersion of polymer particles has a solid content of 30-50%. From the industrial practical point of view, the aqueous dispersion of polymer particles having the above solid content is the most readily available. The aqueous dispersion of polymer particles described above is either self-made or commercially available. As illustrative examples, Dow 3311 acrylate-based aqueous dispersion available from Dow, Allnex 6716 acrylate-based aqueous dispersion available from Allnex, DSM E129 polyurethane polyacrylate aqueous dispersion available from DSM, DSM R2180 polyurethane aqueous dispersion available from DSM, or Alberdingk U9900 polyurethane aqueous dispersion available from Alberdingk can be used.

[0073] According to embodiments of the present application, the amount of the aqueous dispersion of polymer particles can vary over a wide range, and can range from about 60 wt% to about 85 wt% of the total weight of the aqueous base paint. In some embodiments, the amount of the aqueous dispersion of polymer particles can range from 75 wt% to 85 wt%.

[0074] According to some embodiments of the present application, the aqueous base paint can further comprise an amount of an aqueous carrier, such as water, to achieve a suitable coating viscosity.

[0075] According to some embodiments of the present application, the aqueous base paint can comprise a pigment filler, as desired, to impart a desired color and / or intensity to the resulting paint film or coating. As used herein, the term "pigment filler" refers to any volume extender suitable for use in a coating, which can be organic or inorganic, such as in particulate form. The shape of the particles is not particularly limited, and can have any suitable shape. The average particle size of the particles can vary over a wide range, such as from about 10 nanometers to about 50 micrometers. Some particulate materials impart one or more desired properties to the composition and / or coating formed therefrom, in addition to acting as a volume extender for the coating. For example, some particulate materials can impart a desired color to the composition and coating resulting therefrom. In this case, such particulate materials are also referred to as "pigments." Some particulate materials can improve chemical and / or physical properties, particularly mechanical properties of the coating resulting therefrom. In this case, such particulate materials are also referred to as "fillers."

[0076] In embodiments of the present application, suitable exemplary pigment fillers include, for example, kaolin, titanium oxide, calcium carbonate, diatomite, talc, barium sulfate, magnesium aluminum silicate, silica, and any combination thereof. In preferred embodiments, the filler can comprise titanium oxide, kaolin, calcium carbonate, diatomite, or a combination thereof.

[0077] According to the present application, the total amount of pigment filler can vary over a wide range, such as from about 0 wt% to about 60 wt%, preferably from about 0.1 wt% to about 60 wt%, and more preferably from about 10 wt% to about 50 wt%, based on the total weight of the aqueous base paint.

[0078] According to embodiments of the present application, the aqueous base paint can also optionally further comprise other additional additives commonly used in aqueous wood coating compositions that do not adversely affect the coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those agents that will improve the processing or manufacturing properties of the composition, enhance the aesthetics of the composition, or improve specific functional properties or characteristics of the coating composition or the cured composition obtained therefrom, such as adhesion to the substrate. Additional additives that can be included are, for example, co-solvents, defoamers, leveling agents, thickeners, lubricants, anti-migration aids, mildewcides, preservatives, wetting agents, fungicides, rust inhibitors, antioxidants, dispersants, adhesion promoters, UV stabilizers, pH adjusters, film-forming aids, or combinations thereof. The amount of each optional ingredient is sufficient to achieve its intended purpose, but preferably, such amount does not adversely affect the aqueous wood coating composition or the paint film obtained therefrom. In some embodiments of the present application, the aqueous base paint can further comprise one or more of a co-solvent, a defoamer, a leveling agent, a thickener, a surfactant, and a fungicide. In one embodiment of the present application, the aqueous base paint can further comprise one or more of a co-solvent (including but not limited to dipropylene glycol monomethyl ether (DPM), dipropylene glycol monobutyl ether (DPnB)), a defoamer, a leveling agent, a thickener.

[0079] In one specific embodiment according to the present application, the aqueous base paint comprises, relative to the total weight of the aqueous base paint,

[0080] 60-85 wt% of the aqueous dispersion of the polymeric particles;

[0081] 10-30 wt% of water;

[0082] 0-20 wt% of additional additives, one or more of the additional additives being selected from the group consisting of co-solvents, defoamers, leveling agents, and thickeners.

[0083] In some embodiments according to the present application, the aqueous wood coating composition is substantially free of flatting powder, preferably completely free of flatting powder.

[0084] In some embodiments according to the present application, the aqueous wood coating composition formed by mixing the aqueous base paint with the oligomeric siloxane has a gloss reduction of 10% or more, preferably 30% or more, more preferably 50% or more, compared to a control paint film formed in the same manner from the aqueous base paint, when the aqueous wood coating composition is applied to an aged polyurethane panel at a wet film thickness of 150 microns and air dried for 7 days.

[0085] In some embodiments according to the present application, the waterborne wood coating composition formed by mixing the waterborne base paint with the oligomeric siloxane exhibits improved chemical resistance, preferably improved alkali resistance, when the waterborne wood coating composition is applied to an aged polyurethane panel at a wet film thickness of 150 microns and air dried for 7 days, as compared to a conventional paint film having a similar gloss level.

[0086] In some embodiments according to the present application, the paint film formed from the waterborne wood coating composition according to the present application exhibits higher transparency at the same gloss level as compared to a control paint film formed from a control waterborne base paint formed by combining a waterborne base paint with a commercially available flatting agent.

[0087] The waterborne wood coating composition according to the present application can be prepared using any suitable mixing method known to those of ordinary skill in the art. For example, the waterborne wood coating composition can be prepared by adding the waterborne emulsion, water, and additional additives, if present, to a container, and then stirring the resulting mixture until uniform, thereby forming a waterborne base paint; and then mixing the resulting waterborne base paint with an appropriate amount of the oligomeric siloxane, thereby obtaining the final waterborne wood coating composition.

[0088] The waterborne wood coating composition of the present application can be applied by conventional methods known to those of ordinary skill in the art, for example, by drawdown, spraying, rolling, or other conventional coating methods known to those of ordinary skill in the art.

[0089] Wood products

[0090] The present application also provides a wood product comprising: a wood substrate having at least one major surface; and at least one paint film formed from the waterborne wood coating composition according to embodiments of the present application directly or indirectly coated on the major surface.

[0091] In embodiments of the wood product of the present application, the substrate is a wood substrate. The wood substrate can use any suitable wood substrate known in the art. In the present application, the term "wood substrate" refers to any cellulosic / lignin material derived from the hard, fibrous structural tissue in the stems and roots of trees and other woody plants. Wood includes, for example, hardwood and softwood lumber cut directly from trees, as well as engineered wood composites made from wood strips, wood particles, wood fibers, or wood veneers. Examples of wood composites include, but are not limited to, plywood, oriented strand board (OSB), medium density fiberboard (MDF), particle board, and the like. As an example of strand board, melamine board, i.e., strand board treated with melamine, can be used.

[0092] As an exemplary wood substrate, one or more of the following can be used: hard wood, chestnut, oak, red hook chestnut, oil tea, Chinese fir, Douglas fir, Japanese cedar, American white cedar, Japanese red pine, Japanese yellow cedar, water hickory, black walnut, maple, Japanese beech, Japanese Paulownia, birch, balsa, magnolia, ash, teak, oak, rubber wood.

[0093] As described above, the waterborne wood coating composition according to the present application is suitable for coating on the surface of a wood substrate as a topcoat layer, thereby providing a low gloss or matte effect to the surface of the wood substrate.

[0094] The present disclosure is more particularly described in the following examples that are intended to be illustrative only, as numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Described herein are all such modifications and variations. Unless otherwise indicated, all percentages, parts, and ratios reported herein are based on weight. All reagents used in the examples are commercially available and used without further purification unless otherwise stated.

[0095] Test methods

[0096] Electron microscopy test: After the waterborne wood coating composition was coated on a polyvinyl chloride (PVC) black film with a wet film thickness of 150 microns and air dried for 7 days, the morphology of the dry film surface was observed using a LEICA DVM6.

[0097] Infrared test: After the waterborne wood coating composition was coated on a polyvinyl chloride (PVC) black film with a wet film thickness of 150 microns and air dried for 7 days, the sample coating was subjected to attenuated total reflection testing using a Thermo Nicolet Nexus 470-FTIR infrared spectrometer.

[0098] Gloss: After the waterborne wood coating composition was coated on an aged polyurethane panel with a wet film thickness of 150 microns and air dried for 7 days, the 60° gloss of the sample was tested using a BYK 4565 micro-BYK gloss meter.

[0099] Transparency: After the waterborne wood coating composition was coated on a glass panel with a wet film thickness of 150 microns and air dried for 7 days, the transparency of the sample was tested under visible light at 550 nm, blue light at 430 nm, and violet light at 395 nm, respectively, using an LS108 from Linshang Technology Co., Ltd., Shenzhen.

[0100] Chemical resistance: The waterborne wood coating composition is applied to the aged polyurethane panel at a wet film thickness of 150 microns and air dried for 7 days before testing the waterborne wood coating composition for chemical resistance according to test standards GB / T 3324-2008 and GB / T 23999-2009 and scoring, wherein grade 5 indicates the best chemical resistance and 0 indicates the worst chemical resistance.

[0101] Examples

[0102] The raw materials used in this example are listed in Table 1 below.

[0103] Table 1.

[0104]

[0105]

[0106] Waterborne wood coating composition

[0107] According to the amounts shown in Table 2, the waterborne latex, co-solvent, defoamer, leveling agent, thickener and water are sequentially added into a production kettle and stirred until uniform; then, the oligomeric siloxane in the amounts shown in Table 2 is continuously added into the production kettle, stirred until uniform, followed by discharging, filtering and packaging to obtain the waterborne wood coating composition according to the embodiment of the present application.

[0108] As a control, the waterborne latex, co-solvent, defoamer, leveling agent, thickener and water are sequentially added into a production kettle and stirred until uniform; then, the different types of commercial matting agent BCR 1693, SYLOID 7000 or TS-100 in the amounts shown in Table 2 is continuously added into the production kettle, stirred until uniform, followed by discharging, filtering and packaging to obtain the waterborne wood coating composition for control.

[0109]

[0110] Optical properties of the waterborne wood coating composition

[0111] According to the test methods shown in the test section, the waterborne base paint without oligomeric siloxane is used as control sample 1, which is compared with the above-mentioned waterborne wood coating compositions 1-4 according to the present application and comparative waterborne wood coating compositions examples A-F, which are applied to the aged polyurethane panel at a wet film thickness of 150 microns and air dried for 7 days before testing the 60° gloss of the samples using a gloss meter BYK 4565.

[0112] In addition, the coating composition formed by incorporating the small molecule epoxy silane A 187 into the waterborne base paint is used as control sample 2, and the 60° gloss of the obtained paint film is also determined as described above.

[0113] The test results are summarized in Table 3 below.

[0114] Table 3. Gloss of paint film formed by waterborne wood coating composition

[0115] 60° gloss Control 1 69.1 Control 2 68.3 Comparative Example A 47.6 Comparative Example B 46.9 Comparative Example C 48.1 Comparative Example D 28.2 Comparative Example E 28.9 Comparative Example F 27.3 Example 1 40.3 Example 2 27.8 Example 3 22.1 Example 4 12.5

[0116] As can be seen from the results shown in Table 3 above, incorporation of oligomeric siloxane into the waterborne base paint can significantly reduce the gloss of the coating composition, and even result in a matte coating composition, i.e. a coating composition having a 60° gloss less than 25, which is superior to conventional commercial matting agents in terms of matting performance. In contrast, incorporation of small molecule epoxy silane, such as A-187 (γ-glycidoxypropyltrimethoxysilane, which has a hydrolysable functional group that can be removed as a small molecule), into the waterborne base paint does not significantly reduce the gloss of the coating composition. Thus, it is necessary to incorporate a polysiloxane having a hydrolysable functional group in the form of an oligomer into the waterborne base paint in order to reduce the surface gloss of the paint film.

[0117] To further investigate the surface characteristics of the paint film, the inventors performed electron microscopy and infrared analysis on the surface of the paint film formed by the coating composition of Example 2, and the results are shown in Figure 1 and Figure 2 As can be seen from the results shown in Figure 1 , incorporation of oligomeric siloxane into the waterborne base paint greatly increases the surface roughness of the paint film formed therefrom, and there are a large number of pits on the surface of the paint film, some of which are presumably caused by the oligomeric siloxane itself condensing into silicone microparticles and the surface tension of the silicone microparticles being lower than that of the surrounding resin. In contrast, the surface of the control sample 1, which does not contain oligomeric siloxane, is relatively smooth. In addition, as can be seen from the infrared spectrum shown in Figure 2 , the oligomeric epoxy siloxane undergoes crosslinking reaction with the carboxyl-functionalized waterborne latex during film formation, which is manifested by a decrease in the absorption intensity of the characteristic peak of carboxyl group at 1728 cm -1 .

[0118] Next, the waterborne wood coating compositions of Comparative Examples D-F, which have similar gloss, and the waterborne wood coating composition of Example 2 were compared, and the transparency of each paint film was measured. The test results are summarized in Table 4 below.

[0119] Table 4. Transparency of paint film formed by waterborne wood coating composition

[0120]

[0121] As can be seen from the results shown in Table 4 above, the waterborne wood coating composition obtained by incorporating oligomeric siloxane into the waterborne base paint has comparable or even superior transparency compared to the control waterborne wood coating composition having similar gloss.

[0122] Coating film properties of waterborne wood coating compositions

[0123] The waterborne wood coating composition 2 according to the present application and comparative waterborne wood coating compositions examples D-F having similar gloss were compared, and the chemicals shown in Table 5 below were overlaid on the coating films formed by these coating compositions for a certain period of time, and the resistance to chemicals was tested according to the test methods shown in the test section. The test results are summarized in Table 5 below.

[0124] Table 5. Chemical resistance of coating films formed by waterborne wood coating compositions

[0125] Chemicals Comparative Example D Comparative Example E Comparative Example F Example 2 50% ethanol (1 hour) 4 3.5 3.5 4 4% coffee in water (1 hour) 5 5 5 5 Tea in water (1 hour) 5 5 5 5 Vinegar (1 hour) 5 5 5 5 Sodium bicarbonate in water / 50 g / L (1 hour) 5 5 5 5 10% sodium carbonate in water (24 hours) 3 3 3 5 10% acetic acid in water (24 hours) 3 3 3 3.5 Water (24 hours) 3.5 3 3 3.5 Hot water at 100°C (20 minutes) 4 3 3 4

[0126] As can be seen from the results in Table 5, the waterborne wood coating composition according to the embodiments of the present application incorporating oligomeric siloxane in the waterborne base paint has improved chemical resistance, especially significantly improved alkali resistance, compared to the comparative waterborne wood coating compositions D-F having similar gloss.

[0127] Other waterborne wood coating compositions

[0128] To verify the mattifying effect of the oligomeric siloxane of the present application in other waterborne base paints, the same amount of Allnex 6716, DSM E-129 and DSM R2180 were respectively used to replace DOW 3311 in Example 2, and the waterborne wood coating compositions according to the present application were prepared as described above.

[0129] Then, the coating compositions were coated on the aged polyurethane panels at a wet film thickness of 150 microns and air dried for 7 days, and the 60° gloss of the samples was tested using a gloss meter BYK4565. The test results are shown in Table 6 below.

[0130] Table 6. Gloss of coating films formed by other waterborne wood coating compositions

[0131] 60° gloss Allnex 6716 29.4 DSM E-129 28.7 DSM R2180 33.5

[0132] As can be seen from the results in Table 6 above, the oligomeric siloxane according to the present application is suitable for waterborne base paints formed by various waterborne latex formulations, has a very wide range of applications, and is worth promoting.

[0133] Although the present application has been described with reference to a number of embodiments and examples, those skilled in the art will recognize that other embodiments can be devised without departing from the scope and spirit of the present application.

Claims

1. An aqueous wood coating composition comprising i) an aqueous base paint comprising an aqueous dispersion of polymer particles and optionally additional additives including pigments and fillers, co-solvents, thickeners, leveling agents, defoamers, or any combination thereof, ii) an oligomeric siloxane having one or more functional groups hydrolytically removable small molecules, wherein the paint film formed from the aqueous wood coating composition has a 60 degree gloss no higher than 40; wherein the aqueous wood coating composition is substantially free of matting powder; and wherein the oligomeric siloxane is present in an amount of 3 to 10 wt% relative to the total weight of the aqueous wood coating composition, wherein the hydrolytically removable small molecules include alcohols, carboxylic acids, oximes, or combinations thereof, wherein the oligomeric siloxane further comprises one or more segments having a reactive functional group with active hydrogen including epoxy, and wherein the polymer particles are carboxyl-functionalized.

2. The aqueous wood coating composition of claim 1, wherein, the hydrolytically removable small molecules further include water.

3. The aqueous wood coating composition of claim 1, wherein, the aqueous dispersion of polymer particles includes an aqueous dispersion of a vinyl acetate-based resin, an aqueous dispersion of an acrylic resin, an aqueous dispersion of a silicone-based resin, an aqueous dispersion of a polyurethane-based resin, an aqueous dispersion of a polyurethane polyacrylic resin, an aqueous dispersion of a fluoropolymer-based resin, or any combination thereof.

4. The aqueous wood coating composition of claim 1, wherein, the oligomeric siloxane has a structure represented by Formula 1: wherein at least one of R1, R2, R3, R4, R5, R6is a hydrolytically removably small molecule functional group selected from the group consisting of C1-C6alkoxy, C2-C6alkenyloxy, C6-C 10 aryloxy, C1-C6alkanoyloxy, C6-C 10 aryloxy, C1-C6alkanoyloxy, C6-C 10 aryloxy, C1-C6alkanoyloxy, C6-C at least one of R1, R2, R3, R4, R5, R6 is a segment with a reactive functional group with active hydrogen selected from an epoxy group; and m is an integer other than 0.

5. The aqueous wood coating composition of claim 4, wherein, the functional group of the hydrolytically removable small molecule is selected from a C1-C6 alkoxy group.

6. The aqueous wood coating composition of claim 4, wherein, m is an integer from 1 to 10.

7. An aqueous wood coating composition according to any one of claims 1 to 3, wherein the oligomeric siloxane comprises two or more segments with a reactive functional group with active hydrogen.

8. The aqueous wood coating composition of claim 7, wherein, the oligomeric siloxane has a structure represented by Formula 2: R A represents a function group hydrolytically removable small molecule selected from one or more of C1-C6alkoxy, C2-C6alkenyloxy, C6-C 10 aryloxy, C1-C6alkanoyloxy, C6-C 10 aroyloxy, C1-C6alkanone oximato, and C6-C 10 arone oximato; and R B represents a fragment bearing a reactive functional group with a reactive hydrogen selected from the group consisting of an epoxy group; and m is an integer other than 0.

9. The aqueous wood coating composition of claim 8, wherein, the functional group of the hydrolytically removable small molecule is selected from a C1-C6 alkoxy group.

10. The aqueous wood coating composition of claim 8, wherein, m is an integer from 1 to 10.

11. An aqueous wood coating composition according to any one of claims 1 to 3, wherein the oligomeric siloxane is water-insoluble.

12. A wood product comprising a wood substrate having at least one major surface; and at least one paint film formed from the aqueous wood coating composition of any one of claims 1 to 11 coated directly or indirectly on the major surface.

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