Aqueous wood sealer, a sealing coating formed therefrom, and a wood product

Abstract

This invention relates to a water-based wood sealing primer, a sealing coating formed therefrom, and wood products. Specifically, the water-based wood sealing primer comprises: at least one film-forming resin, at least one filler, at least one aqueous medium, and optionally at least one additional additive, wherein the at least one filler has a lamellar structure and a shear modulus of elasticity not exceeding 0.4 GPa, the shear modulus of elasticity being tested according to ISO 1421:2016 based on a sample of the prepared sealing primer, and wherein the at least one film-forming resin has a tensile strength of at least 20 MPa, the tensile strength being tested according to GB / T 1040.3-2006 based on a sample of the prepared sealing primer. After applying the water-based wood sealing primer to a pine substrate, particularly to knots in the pine substrate, and baking it at 65°C for 2 hours, the resulting coating surface does not exhibit oiliness or blistering.

Description

Technical Field

[0001] This application belongs to the field of coatings and relates to a water-based wood sealing primer, and more specifically to a water-based wood sealing primer suitable for pine wood substrates, especially suitable for pine wood substrates with knots, as well as a sealing coating and wood products formed therefrom. Background Technology

[0002] Wooden products, including wooden furniture, are among the most commonly used products in production and daily life, primarily made from wood-based materials. Pine, especially Scots pine, is one of the main base materials for wooden products and is known for its numerous knots and abundant resin in these areas. Current processing methods mainly rely on a first coat of sealing primer to address this issue. The sealing primer is a crucial step in the wood coating process, setting the tone for the overall coating effect and significantly influencing the final paint film performance.

[0003] Traditionally, sealing methods involve using oil-based polyurethane (PU) sealing primers. Currently, the main water-based wood sealing primers on the market fall into three categories: water-based anionic emulsion systems, water-based hydroxyl acrylic resins, and water-based epoxy resin systems. When these sealing primers are used to seal knots in pine wood, they often result in poor adhesion and limited sealing effect. After the overall coating is applied, high-temperature baking at the knots easily leads to problems such as oil seepage, blistering, and discoloration, severely affecting the surface finish. Specifically, water-based anionic emulsion systems have the following problems: poor film density, inability to form a strong interaction with the substrate, poor adhesion at pine knots, and a high tendency for blistering and oil seepage during high-temperature baking. Water-based hydroxyl acrylic systems mainly suffer from slow drying, requiring a long drying and sanding time, and generally poor penetration, failing to effectively penetrate the wood pores and bond firmly. Furthermore, the resulting sealing coating is also prone to oil seepage and blistering after high-temperature baking. Water-based epoxy systems form films with good durability and high toughness, but their impermeability is generally poor, making them prone to oil seepage and blistering.

[0004] Therefore, the coatings industry urgently needs an improved water-based wood sealing primer that has excellent adhesion to pine substrates, especially pine substrates with knots, and does not produce oil or bubble after high-temperature baking. Summary of the Invention

[0005] On one hand, the present invention provides a water-based wood sealing primer comprising: at least one film-forming resin, at least one filler, at least one water-based medium, and optionally at least one additional additive, wherein the at least one filler has a lamellar structure and a shear modulus of elasticity of not less than 0.3 GPa, the shear modulus of elasticity being determined according to ISO 1421:2016 based on a prepared sealing primer sample, and wherein the at least one film-forming resin has a tensile strength of at least 20 MPa, the tensile strength being tested according to GB / T 1040.3-2006 based on a prepared sealing primer sample.

[0006] In some preferred embodiments of the invention, the at least one filler has a shear modulus in the range of 0.3 GPa to 0.35 GPa, preferably 60% or more higher than that of conventional spherical fillers, and more preferably 60% to 130% higher.

[0007] In some preferred embodiments of the invention, the at least one film-forming resin has a tensile strength in the range of 20 MPa to 35 MPa, said tensile strength being determined according to GB / T 1040.3-2006 based on a sample of the prepared sealing primer, preferably comprising polyvinyl alcohol.

[0008] Another aspect of the present invention provides a wood article comprising: a wood substrate having at least one main surface with knots; and a sealing coating formed on at least a portion of the main surface with knots by a water-based wood sealing primer of the first aspect described above. Preferably, the wood substrate comprises a pine substrate, including a pine substrate with knots, a pine substrate without knots, or a combination thereof.

[0009] In this invention, the inventors have innovatively proposed that, in the formulation of a water-based wood sealing primer, by combining a filler with a specific shear modulus of elasticity with a film-forming resin with a specific tensile strength, the resulting water-based wood sealing primer can provide a highly effective seal for greases and their chemical components in pine substrates, especially knotted pine substrates. The sealing coating formed by this water-based wood sealing primer can effectively inhibit the seepage of greases and other chemical components from the substrate. For example, after baking at 65°C for 2 hours, the resulting sealing coating does not produce oil or blister, which was difficult to achieve before this application.

[0010] Details of one or more embodiments of the present invention are set forth in the following description. Other features, objects, and advantages of the invention will become clear from the description and claims. Attached Figure Description

[0011] Figure 1 This is a photograph of the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 1 of the present invention, after baking at 65°C for 2 hours;

[0012] Figure 2 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 2 of the present invention after baking at 65°C for 2 hours.

[0013] Figure 3 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 3 of the present invention after baking at 65°C for 2 hours.

[0014] Figure 4 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 4 of the present invention after baking at 65°C for 2 hours.

[0015] Figure 5 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 1 of the present invention after baking at 65°C for 2 hours.

[0016] Figure 6 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 2 of the present invention after baking at 65°C for 2 hours.

[0017] Figure 7 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 3 of the present invention after baking at 65°C for 2 hours.

[0018] Figure 8 The photograph shows the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Comparative Example 4 of the present invention after baking at 65°C for 2 hours.

[0019] Figure 9 This is a photograph of the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Example 1 of the present invention, after being baked at 65°C for 2 hours;

[0020] Figure 10 This is a photograph of the sealing coating formed on pine knots by the water-based wood sealing system prepared according to Example 2 of the present invention, after baking at 65°C for 2 hours;

[0021] definition

[0022] In this document, quantifiers are not used, and "at least one" and "one or more" are used interchangeably. Therefore, for example, a component containing additives can be interpreted as meaning that the component contains "one or more" additives.

[0023] When a composition is described as including or comprising specific components, it is anticipated that optional components not covered by the present invention are not excluded from the composition, and that the composition may be constituted or composed of the components involved. Similarly, when a method is described as including or comprising specific process steps, it is anticipated that optional process steps not covered by the present invention are not excluded from the method, and that the method may be constituted or composed of the process steps involved.

[0024] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0025] When used in the context of wood-based substrates, the term "main surface" refers to the surface formed by the length and width dimensions of the wood-based substrate for providing decoration.

[0026] When used in the context of wood-based materials, the term "knot" refers to a nodule that forms naturally during the growth of a woody plant (such as a pine) that serves as the source of the woody material, including dead and live knots. These knots typically contain a significant amount of oils, such as rosin, which is a mixture of various components including wood rosin, resin rosin, and top-oil rosin.

[0027] When used in this text, the term "sealing coating" is a continuous coating formed by a sealant for sealing wood substrates, particularly knots in wood substrates, with undesirable oily substances such as rosin.

[0028] When referring to the use of "filler", the term "shear modulus" refers to the magnitude of the resistance of the paint film formed by a water-based wood sealing primer containing the filler to shear deformation, reflecting the filler's ability to provide resistance to shear strain for the paint film formed by the water-based wood sealing primer.

[0029] When referring to the use of "packing", the term "specific surface area" refers to the total area per unit mass of packing.

[0030] When referring to the use of “filler”, the term “preform” refers to a pre-prepared material formed by high-temperature sintering and crushing and sieving of a mixture of two or more inorganic materials.

[0031] When referring to the use of "film-forming resin", the term "tensile strength" refers to the magnitude of the resistance of the paint film formed by a waterborne wood sealing primer containing the film-forming resin to tensile deformation, reflecting the ability of the film-forming resin to provide the paint film formed by the waterborne wood sealing primer with resistance to tensile strain.

[0032] In this article, the phrase "no oil seepage on the surface of the sealing coating" is used as an indicator to demonstrate the sealing effect of the sealing coating, which has been baked at high temperature, on the oil in the knots of pine substrate. It can be judged by observing whether the surface of the sealing coating changes color with the naked eye, and is divided into 1-5 levels, where the higher the level, the better the resistance to baking and oil seepage, with level 5 being the best resistance to baking and oil seepage.

[0033] In this article, the phrase "no blistering on the surface of the sealing coating" is a more stringent indicator used to demonstrate the sealing effect of the high-temperature baked sealing coating on the grease and other chemical components in the knots of pine substrate. It can be judged by visually observing whether blistering occurs on the surface of the sealing coating, and is divided into 1-5 levels, with the higher the level, the better the resistance to baking blistering, and level 5 is the best resistance to baking blistering.

[0034] In this paper, the term "adhesion" is used to characterize whether a high-temperature baked sealing coating can form an acceptable coating at knots on a pine substrate. The smaller the value characterizing adhesion, the better the film-forming stability of the high-temperature baked sealing coating at knots on the pine substrate, with grade 0 indicating the best adhesion.

[0035] When used in the context of “applying a coating over a coating,” the term “over” includes applying one coating directly or indirectly over another. In some embodiments of the invention, the primer layer is applied directly over the sealing coating, in direct contact with the sealing coating. In other embodiments of the invention, one or more colorant layers may be present between the primer layer and the sealing coating to obtain the desired color.

[0036] When used in this specification and claims, the terms “comprising” and “including” and their variations are not restrictive.

[0037] The terms "preferred" and "ideally" refer to embodiments of the invention that provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. Detailed Implementation

[0038] In the coating process of wood-based products, such as furniture, pine, especially Scots pine, is one of the main base materials for wood products. It is characterized by many knots and rich oil in the knot areas. The presence of this oily substance makes the sealing effect of the primer on the wood substrate less than ideal. Oiling and blistering often occur on the surface during post-processing, especially during high-temperature baking. This has been a long-standing technical problem that the furniture coating industry has struggled to solve.

[0039] The inventors of this application have conducted extensive and in-depth research on wood-based substrates, particularly pine, and have revealed for the first time that under high-temperature conditions, oils and chemicals in wood-based substrates, especially pine, leak out through the fibrous ducts and undergo volume expansion, resulting in the paint film surface bearing extremely high static pressure. Therefore, in order to achieve effective sealing, the sealing coating not only needs to resist the seepage of oils and chemicals but also needs to effectively resist the static pressure exerted on the paint film by oils and chemicals.

[0040] Therefore, the inventors of this application have creatively proposed that, in the formulation of water-based wood sealing primers, by combining fillers with a specific shear modulus of elasticity with film-forming resins with a specific tensile strength, the resulting water-based wood sealing primer film possesses both good flexibility and static bending strength. This effectively resists the static pressure exerted on the film by greases and their chemicals, effectively sealing greases and chemicals in pine substrates, especially those with knots, within the ducts, thereby preventing oil seepage and blistering. In some embodiments of the present invention, after baking at 65°C for 2 hours, the sealing coating formed by the water-based wood sealing primer prepared in this way does not exhibit oil seepage or blistering, which was difficult to achieve prior to this application.

[0041] Therefore, one aspect of this application provides a water-based wood sealing primer, comprising: at least one film-forming resin, at least one filler, at least one water-based medium, and optionally at least one additional additive, wherein the at least one filler has a lamellar structure and a shear modulus of elasticity of not less than 0.3 GPa, the shear modulus of elasticity being determined according to ISO 1421:2016 based on a prepared sealing primer sample, and wherein the at least one film-forming resin has a tensile strength of at least 20 MPa, the tensile strength being determined according to GB / T1040.3-2006 based on a prepared sealing primer sample.

[0042] The types of fillers commonly used in the coatings industry are diverse, including but not limited to calcium carbonate, barium sulfate, silica, and silicate fillers. As one of the most common fillers, silicate fillers possess excellent physicochemical properties such as plasticity and fire resistance, and also exhibit strong chemical stability and a certain degree of acid and alkali resistance, making them ideal coating fillers. However, the same powder often exhibits significant morphological differences depending on its crystal structure and different production methods, leading to substantial performance variations in coating applications. Currently, the types of silicate fillers commonly used in the market are diverse, including but not limited to kaolin, talc, wollastonite, mica powder, sericite, and synthetic aluminum silicate, etc. They can be classified in multiple dimensions; even just based on shape, they can be categorized into spherical, near-spherical, blocky, rod-shaped, needle-shaped, and flattened forms, etc.

[0043] The inventors of this application have discovered that lamellar fillers with high shear modulus have a significant impact on the mechanical properties of coatings, and their use in sealing coatings can effectively improve the static bending strength of the coating. As the name suggests, "static bending strength" refers to the compressive strength a material can withstand when bent under stress until it breaks; the greater the static bending strength, the less likely the material is to bend. In this application, the use of lamellar fillers with high shear modulus results in a sealing coating with high static bending strength, which effectively resists static pressure applied vertically by greases and chemicals. Therefore, even when subjected to high-temperature treatment, it is not prone to bending and blistering, thus achieving effective sealing of greases and chemical components in the pine substrate.

[0044] Not bound by any theory, the inventors recognized that, on the one hand, during the dehydration and film-forming process of the paint film, the lamellar filler particles can be better laid flat in the paint film layer, arranged in an alternating and overlapping manner, which increases the density of the paint film, reduces the porosity, and better prevents the seepage of oils and other chemical components from pine wood; on the other hand, because the filler has a high shear modulus, the paint film formed by the water-based sealing primer containing this filler has less deformation and high stiffness when subjected to forces from the thickness direction, which can provide the paint film with sufficiently high resistance to static pressure in the thickness direction. Thus, while effectively preventing the seepage of oils and other chemical components from pine wood, the paint film also effectively reduces the blistering phenomenon of the coating during high-temperature treatment.

[0045] Therefore, incorporating the aforementioned specific fillers is one of the key factors in achieving effective sealing of oils and chemicals in pine substrates, especially scarred pine substrates, by the coating film formed by water-based wood sealing primers.

[0046] In embodiments of the present invention, the filler has a lamellar structure, including but not limited to silicate fillers with a lamellar structure, such as kaolin, talc, mica powder, etc. These lamellar filler particles can be well spread evenly in the paint film layer, arranged in an alternating, overlapping manner, thereby increasing the density of the paint film, reducing its porosity, and better preventing the seepage of oils and other chemical components from pine wood. In addition, the filler also has a shear modulus of elasticity of not less than 0.3 GPa, which is determined according to ISO 1421:2016 based on the prepared sealing primer sample. In this application, the above-mentioned shear modulus of elasticity is determined based on the prepared sealing primer film sample. However, considering that the main component contributing to the shear modulus of elasticity in the sealing primer film sample is the lamellar filler, it can be used as a physicochemical parameter characterizing the filler. As mentioned above, "shear modulus of elasticity" is an index of the resistance of the paint film formed by the water-based wood sealing primer containing the filler to shear deformation perpendicular to the paint film, reflecting the filler's ability to provide the paint film with resistance to shear strain. Fillers with high shear modulus result in smaller deformation and higher rigidity of the coating film formed from them in the thickness direction. This allows the coating film to better prevent the exudation of oils and other chemical components from pine wood while effectively reducing blistering during high-temperature treatment. If the shear modulus of the filler is too low, it cannot effectively provide the coating film with resistance to shear strain; if the shear modulus of the filler is too high, it will lead to a significant decrease in the flexibility of the coating film, which is not conducive to the adhesion of the coating film to the surface of wood substrates with uneven surfaces. Therefore, in some embodiments of the present invention, the shear modulus of the filler is in the range of 0.3 GPa to 0.35 GPa. Preferably, the shear modulus of the filler can be 0.30 GPa, 0.31 GPa, 0.32 GPa, 0.33 GPa, 0.34 GPa, 0.35 GPa, or within a range consisting of any two of the above values.

[0047] In some embodiments of the invention, the at least one filler has a shear modulus that is 60% or more higher than that of conventional spherical particulate fillers. Not based on any theory, the inventors hypothesize that fillers with lamellar structures can better spread within the paint film layer during the dehydration and film-forming process, forming an interlaced stacked arrangement. This results in a paint film formed from this arrangement having a significantly higher shear modulus than one formed from conventional spherical particulate fillers. The larger the lamellar structure of a single filler particle, and the denser the interlaced stacked arrangement formed, the higher the shear modulus exhibited by the filler, thereby effectively reducing blistering of the coating during high-temperature treatment. Therefore, in a preferred embodiment of the invention, the at least one filler has a shear modulus that is 60% to 130% higher than that of conventional particulate fillers, preferably 70% to 130% higher, more preferably 80% to 130% higher, even more preferably 90% to 130% higher, and even more preferably 100% to 130% higher, with the most preferred shear modulus being 120% to 130% higher.

[0048] In one embodiment of the present invention, the specific surface area of ​​the at least one filler is 1-50 m². 2 Within the range of / g. In the context of this application, the specific surface area of ​​a filler refers to the total area possessed by a unit mass of filler. As mentioned above, in this invention, the filler has a lamellar structure, and therefore its specific surface area is significantly lower than that of fillers with a spherical structure. Therefore, preferably, the specific surface area of ​​the at least one filler is in the range of 1-20m². 2 Within the range of / g, more preferably within 2-15m 2 Within the range of / g, it is even more preferable to be within 3-10m 2 Within the range of / g. As an example, the specific surface area of ​​the at least one filler can be 2m². 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g、19m2 / g or within a range consisting of any two of the above values.

[0049] The at least one filler may have a particle size typical of fillers in the coatings industry, ranging from nanoscale to microscale, but not excessively small. In some embodiments, the median particle size of the at least one filler is typically in the range of 0.5-4 micrometers.

[0050] In one embodiment of the invention, the at least one filler is a preform formed by high-temperature calcination and pulverization of one or more, preferably all, inorganic materials, including calcium carbonate, kaolin, talc, and mica powder (i.e., magnesium aluminum silicate). As described above, the preform is a pre-prepared product formed by high-temperature sintering, pulverization, and sieving of a mixture of two or more inorganic materials. This product combines the advantages of the various inorganic fillers mentioned above, enabling these inorganic fillers to work together better and provide optimal resistance to oil seepage and bubbling.

[0051] Preferably, the preform comprises, relative to the total weight of the inorganic materials used to prepare the preform, 20-40 wt% kaolin, 20-40 wt% talc, 5-15 wt% magnesium aluminum silicate, and 20-40 wt% calcium carbonate. This mixture of inorganic materials is sintered at a high temperature, for example, at 600-800°C, and then pulverized and sieved to form the desired preform. In a specific embodiment according to the invention, the filler in this preform form is homemade.

[0052] In some embodiments of the invention, the at least one filler is present in an amount of at least 5% by weight, but not exceeding 40% by weight, relative to the total weight of the water-based wood sealing primer; preferably, the at least one filler is present in an amount of 10% by weight to 30% by weight; more preferably, the at least one filler is present in an amount of 10% by weight to 20% by weight. Too low a dosage will not effectively seal the oils and chemicals in pine substrates, especially knots in pine substrates; too high a dosage will adversely affect the adhesion of the paint film formed by the water-based wood sealing primer to the substrate.

[0053] The inventors of this application have also discovered that incorporating a film-forming resin with specific tensile strength into the formulation of a water-based wood sealing primer can provide the paint film with sufficient resistance to plastic deformation, thereby significantly inhibiting the exudation of oils and chemicals from pine substrates, especially pine substrates with knots, and greatly reducing oil production on the coating surface.

[0054] In an embodiment of the present invention, the waterborne wood sealing primer comprises at least one film-forming resin having a tensile strength of at least 20 MPa, said tensile strength being tested according to GB / T 1040.3-2006 based on a prepared sealing primer sample. In this application, the aforementioned tensile strength is determined based on a prepared sealing primer film sample. However, considering that the main component contributing to the tensile strength in the sealing primer film sample is the film-forming resin component, it can be used as a physicochemical parameter characterizing the film-forming resin. As is well known, "tensile strength," also known as "tensile resistance," is used to characterize the resistance of a material to maximum uniform plastic deformation. Before being subjected to the maximum tensile stress, the deformation of the tensile specimen is uniform, but after exceeding the maximum tensile stress, necking begins to occur, i.e., concentrated deformation occurs. In this application, the "tensile strength" of the film-forming resin refers to the magnitude of the resistance exhibited by the film formed by the waterborne wood sealing primer containing the film-forming resin under tensile deformation along the length direction of the film, reflecting the ability of the film-forming resin to provide resistance to tensile strain for the film formed by the waterborne wood sealing primer. Film-forming resins with high tensile strength result in less deformation of the formed film along its length, making it less prone to breakage and thus better preventing the seepage and blistering of oils and other chemical components from pine wood. If the tensile strength of the film-forming resin is too low, the resulting film will be too soft and unable to prevent the seepage of oils and chemicals from the pine substrate, especially knotted pine substrates, and the coating surface will be prone to blistering. If the tensile strength of the film-forming resin is too high, it will cause the film to be too brittle and unable to withstand the static pressure applied vertically by oils and chemicals for a long time. Therefore, in some embodiments of the present invention, the tensile strength of the film-forming resin is in the range of 20 MPa to 35 MPa. As an example, the tensile strength of the at least one film-forming resin can be 22 MPa, 24 MPa, 26 MPa, 28 MPa, 30 MPa, 32 MPa, 34 MPa, or within any two of the above values.

[0055] Therefore, in embodiments of the present invention, in addition to fillers, the waterborne wood sealing primer according to the present invention also contains at least one film-forming resin having the aforementioned tensile strength. In the context of the present invention, resin component refers to the component constituting the main body of the waterborne wood sealing primer. On the one hand, this resin component acts as a binder to hold the various components (such as fillers) in the waterborne wood sealing primer together and imparts a certain cohesive strength to the waterborne wood sealing primer. On the other hand, as described above, this resin component can provide sufficient resistance to plastic deformation to the paint film, thereby significantly inhibiting the exudation of oils and chemicals from pine substrates, especially pine substrates with knots, and greatly reducing oil seepage from the coating surface.

[0056] As an example, the film-forming resin having the above-mentioned tensile strength can include any resin suitable for common types of water-based wood sealing primers in the art. Preferably, the film-forming resin having the above-mentioned tensile strength is incompatible with the oils of pine substrates, especially knotted pine substrates, because the paint film formed by such a film-forming resin is not easily penetrated by oils, thereby further reducing oiling on the coating surface.

[0057] In a preferred embodiment of the invention, the film-forming resin includes polyvinyl alcohol resin and its derivatives.

[0058] Polyvinyl alcohol (PVA) is a white, stable, non-toxic, water-soluble polymer produced by the polymerization and alcoholysis of vinyl acetate. As a known polymer material, PVA exhibits a wide range of properties. As mentioned above, PVA is a polymer material produced by the polymerization and alcoholysis of vinyl acetate. The degree of alcoholysis of PVA refers to the extent to which hydroxyl groups replace acetate groups during the alcoholysis process of polyvinyl acetate, that is, the percentage of functional groups that have been successfully alcoholyzed out of the total functional groups. The degree of alcoholysis directly affects the physical and chemical properties of PVA, especially its water solubility. Generally, PVA resin with a degree of alcoholysis less than 95% can dissolve in water at room temperature, while PVA resin with a degree of alcoholysis greater than 99.5% can only dissolve in hot water above 95°C.

[0059] The inventors of this application have discovered that polyvinyl alcohol (PVA) is soluble in water, almost unaffected by weak acids, weak alkalis, or organic solvents, and exhibits high oil resistance. Therefore, it can be considered a suitable film-forming resin for formulating water-based wood sealant primers. Furthermore, PVA molecules possess high adhesion, readily forming films. The resulting films are colorless and transparent, possess good mechanical strength, have a smooth and non-sticky surface, and exhibit good light transmittance, high moisture permeability, and are non-charged, making them a viable option for film-forming resins in wood sealing coatings. The inventors of this application have further discovered that the molecular chain of PVA contains a large number of hydroxyl groups, resulting in strong intermolecular forces due to hydrogen bonding. Therefore, some PVA polymers can meet the aforementioned tensile strength requirements. Moreover, PVA aqueous solutions exhibit excellent adhesion to hydrophilic cellulose in wood substrates, with the adhesion strength increasing with the degree of alcoholysis and polymerization, thus enabling better adhesion to the surface of the wood substrate.

[0060] Therefore, in some preferred embodiments of the present invention, polyvinyl alcohol is preferably selected as the film-forming resin of the water-based wood sealing primer.

[0061] In some embodiments of the present invention, the polyvinyl alcohol has a degree of hydrolysis of 85-95%. Polyvinyl alcohol with this degree of hydrolysis is readily soluble in water at room temperature, making it more suitable for the formulation of water-based wood sealing primers.

[0062] In some embodiments of the invention, the polyvinyl alcohol has a weight-average molecular weight in the range of 150,000 to 250,000, preferably in the range of 170,000 to 220,000. Polyvinyl alcohol having the above molecular weight can provide suitable stability and workability for water-based wood sealing primers.

[0063] In some preferred embodiments of the invention, the polyvinyl alcohol has a degree of hydrolysis of 85-95% and a weight-average molecular weight in the range of 150,000 to 250,000, preferably in the range of 170,000 to 220,000.

[0064] If necessary, in addition to the aforementioned polyvinyl alcohol, the waterborne wood sealing primer according to the present invention may also contain at least one acrylic resin, at least one polyurethane acrylate (PUA), at least one polyurethane resin, at least one epoxy resin, or any combination thereof, as a film-forming resin. In the presently preferred embodiment of the present invention, the waterborne wood sealing primer according to the present invention contains only polyvinyl alcohol as the sole film-forming resin.

[0065] Polyvinyl alcohol can be homemade or commercially purchased, such as polyvinyl alcohol 2488 purchased from Chengdu Blue Whale Technology Co., Ltd.

[0066] Preferably, the water-based wood sealing primer contains, relative to its total weight, about 10% to about 60% by weight, preferably about 10% to about 50% by weight, and more preferably about 10% to about 40% by weight of a film-forming resin, preferably polyvinyl alcohol. Specifically, the water-based wood sealing primer contains, relative to its total weight, about 15% by weight, about 20% by weight, about 25% by weight, about 28% by weight, about 30% by weight, about 35% by weight, about 38% by weight, about 40% by weight, or within the range of any two of the above values, of a film-forming resin, preferably polyvinyl alcohol.

[0067] The viscosity of water-based wood sealer primers can be adjusted using any suitable water-based medium as needed. Suitable water-based media include water-soluble organic solvents, water, and mixtures thereof. The water-based medium is selected to adjust the viscosity of the water-based wood sealer primer for further formulation.

[0068] Suitable water-soluble organic solvents include alcohols (e.g., ethanol, n-propanol, isopropanol, n-butanol, isobutanol, etc.); ketones (e.g., acetone, 2-butanone, cyclohexanone, methyl aryl ketone, ethyl aryl ketone, methyl isopentyl ketone, etc.); glycols (e.g., butyl ethylene glycol); glycol ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, methoxypropanol, dipropylene glycol methyl ether, etc.); glycol esters (e.g., butyl ethylene glycol acetate, methoxypropyl acetate, etc.); and mixtures thereof. Preferably, glycol ethers are used as organic solvents.

[0069] The amount of aqueous medium contained in a water-based wood sealer can vary, for example, depending on the application method and the desired viscosity. A preferred embodiment of a water-based wood sealer contains 25-85% by weight of an aqueous medium, more preferably 25-40% by weight of water.

[0070] Waterborne wood sealing primers according to certain embodiments of the present invention may further contain film-forming aids to assist in film formation. Suitable film-forming aids include alcohols, such as ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, etc.; alcohol esters, such as dodecyl alcohol esters; alcohol ethers, such as ethylene glycol butyl ether (BCS), propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol n-propyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether (DPNB), tripropylene glycol n-butyl ether, etc.; alcohol ether esters, such as hexanediol butyl ether acetate; diesters, such as diisobutyl dicarboxylate. As examples of diester film-forming aids, Coasol 290plus from Chemoxy (UK) or Loxanol CA 5308 from BASF can be used.

[0071] In some preferred embodiments of the invention, the waterborne wood sealing primer comprises, relative to the total weight of the waterborne wood sealing primer, about 2 to about 10% by weight, preferably about 2 to about 8% by weight, of a film-forming aid. Specifically, the amount of film-forming aid included in the waterborne wood sealing primer is, relative to the total weight of the waterborne wood sealing primer, from about 2% by weight, about 3% by weight, about 4% by weight, about 5% by weight to about 10% by weight, about 9% by weight, or about 8% by weight, or within the range of any two of the above values.

[0072] In embodiments of the invention, the waterborne wood sealing primer may optionally contain additional additives commonly used in waterborne 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 processability or manufacturing properties of the composition, enhance the aesthetics of the composition, or improve specific functional properties or characteristics (such as adhesion to the substrate) of the coating composition or the cured composition obtained therefrom. Additives that may be included include, for example, emulsifiers, pigments, anti-migration agents, antibacterial agents, chain extenders, lubricants, wetting agents, biocides, plasticizers, defoamers, colorants, waxes, antioxidants, corrosion inhibitors, flow control agents, thixotropic agents, dispersants, adhesion promoters, UV stabilizers, thickeners, defoamers, pH adjusters, or combinations thereof. The amounts of each optional component are sufficient to achieve their intended purpose, but preferably, such amounts do not adversely affect the coating composition or the cured coating obtained therefrom. In a preferred embodiment of the invention, suitable additives include pigments, thickeners, dispersants, leveling agents, defoamers, wetting agents, pH adjusters, preservatives, fungicides, or any combination thereof. The amount of each optional additive is sufficient to achieve its intended purpose, but preferably, such amount will not adversely affect the waterborne wood sealing primer or the resulting sealing coating. According to certain embodiments of the invention, the total amount of additives relative to the total weight of the waterborne wood sealing primer ranges from about 0% by weight to about 10% by weight, preferably from about 0.1% by weight to about 10% by weight.

[0073] In one embodiment of the present invention, the water-based wood sealing primer of the present invention comprises, relative to the total weight of the water-based wood sealing primer:

[0074] 10 to 60% by weight of at least one film-forming resin;

[0075] At least one filler, comprising 5 to 25% by weight;

[0076] 25 to 85% by weight of aqueous media; and

[0077] 0 to 10% by weight of additional additives;

[0078] The additional additives include pigments, thickeners, wetting agents, leveling agents, defoamers, dispersants, pH adjusters, mildew inhibitors, preservatives, or any combination thereof.

[0079] According to the present invention, the water-based wood sealing primer is prepared as follows: First, the water-based wood sealing primer is prepared by any suitable mixing method known to those skilled in the art. For example, the water-based wood sealing primer can be prepared by dissolving a film-forming resin in an aqueous medium, then dispersing a preform of filler at high speed, supplemented with film-forming aids, pigments and additional additives (if any), and then stirring the resulting mixture until homogeneous, thereby obtaining the water-based wood sealing primer required by the present invention.

[0080] As described above, the water-based wood sealing system formed above has a particularly excellent sealing effect on pine substrates, especially pine substrates with knots.

[0081] Therefore, in some embodiments of the invention, after applying the water-based wood sealing primer to the knots of a wood substrate and baking it at 65°C for 2 hours, the resulting coating surface does not ooze oil or bubble.

[0082] In some embodiments of the invention, after applying the water-based wood sealing primer to knots on a wood substrate and baking it at 65°C for 2 hours, the resulting coating has an adhesion grade of at least 1, the adhesion being determined by cross-cut adhesion test according to ASTM D3359.

[0083] The water-based wood sealing primer according to the present invention can be applied using conventional coating methods known to those skilled in the art. These coating methods include dip coating, spin coating, spray coating, curtain coating, brush coating, roller coating, and other coating methods known in the art. In one embodiment of the invention, coating is performed using a spraying process. The water-based wood sealing primer can be applied to various sealing coating thicknesses. In some embodiments of the invention, the sealing coating thickness is preferably in the range of about 1 to about 200 μm, more preferably in the range of 5-150 μm. The coated coating can be cured by air drying or by accelerating curing using various drying devices familiar to those skilled in the art (e.g., ovens). In this way, a sealing coating can be formed from the water-based wood sealing primer of the present invention, which also falls within the protection scope of the present invention.

[0084] Another aspect of the present invention provides an article comprising: a wood substrate having at least one main surface with knots; and a sealing coating formed by an aqueous wood sealing primer according to the present invention applied to at least a portion of the main surface with knots.

[0085] As a wood-based material for manufacturing wood products, any suitable wood-based material known in the art can be used. In this application, the term "wood-based material" refers to any cellulose / lignin material derived from the hard, fibrous tissue of the stems and roots of trees or other woody plants. Wood includes, for example, hardwood and softwood timber cut directly from trees, as well as engineered wood composites made from wood strips, wood chips, wood fibers, or wood veneers. Examples of wood composites include, but are not limited to, plywood, oriented strand board (OSB), medium-density fiberboard (MDF), and particleboard.

[0086] Preferably, the wood product of this invention comprises a wood substrate containing rosin-like substances. It is well known that the rosin-like substances include three types: resinous rosin, woody rosin, and surface oil rosin. As described above, the inventors of this application have discovered for the first time that under high-temperature conditions, the oils and chemicals in wood substrates, especially pine substrates, undergo volume expansion and overflow through fibrous ducts, resulting in the paint film surface bearing extremely high static pressure. Therefore, in the formulation of water-based wood sealing primers, by combining fillers with a lamellar structure having a specific shear modulus of elasticity with a film-forming resin having a specific tensile strength, the resulting water-based wood sealing primer can provide a very effective seal for the oils and their chemical components in pine substrates, especially knotted pine substrates.

[0087] According to certain embodiments of the present invention, the wood substrate has at least one, preferably two, main surfaces that are opposite to each other.

[0088] According to certain embodiments of the present invention, the article can be prepared, for example, by the following steps: (1) providing a sanded wood substrate; (2) applying a water-based wood sealing primer according to an embodiment of the present invention once or multiple times onto the wood substrate using a coating and curing process, and forming one or more sealing coatings according to embodiments of the present invention to provide the wood substrate with the desired sealing properties. Further, the preparation process of the article may include additional steps, such as (3) applying a primer onto the sealing coating to obtain a base coat; and (4) applying a topcoat onto the base coat to obtain a top coat.

[0089] According to certain embodiments of the present invention, the wood products thus obtained can be used for 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 and door frames; outdoor and indoor wall panels and wood flooring.

[0090] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available and ready for use without further processing.

[0091] Example

[0092] Test methods

[0093] Shear modulus: A water-based wood sealing primer containing the filler to be tested was applied to a treated pine substrate with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours to obtain a sealing primer film sample. The shear modulus of elasticity of the film sample was then determined according to ISO 1421:2016 to determine the shear modulus of elasticity of the filler to be tested.

[0094] Tensile strength A water-based wood sealing primer containing the film-forming resin to be tested was applied to a treated pine substrate with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours to obtain a sealing primer film sample. Then, the tensile strength of the film sample was determined according to GB / T 1040.3-2006 to determine the tensile strength of the film-forming resin to be tested.

[0095] Oil bubbling test A water-based wood sealing primer was applied to a treated pine substrate with a wet film thickness of 150 micrometers and dried at 35°C for 2 hours. Then, a water-based single-component white primer was applied with a wet film thickness of 150 micrometers and dried at 35°C for 2 hours, followed by a water-based single-component white topcoat with a wet film thickness of 150 micrometers and dried at 40°C for 2 hours, thus obtaining a coating system. The resulting coating system was then baked at 65°C for 2 hours. The presence of oil seepage and blistering on the coating surface was assessed visually, rated on a scale of 0-5, where 5 indicates no oil seepage or blistering; 4.5 indicates slight oil seepage and blistering area less than 1%; 4 indicates slight oil seepage and blistering area of ​​1-5%; 3 indicates moderate oil seepage and blistering area of ​​5-20%; 2 indicates heavy oil seepage and blistering area of ​​20-50%; and 1 indicates severe oil seepage and blistering area exceeding 50%.

[0096] AdhesionA water-based wood sealing primer was applied to a treated pine substrate with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours. Then, a water-based one-component white primer was applied with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours, followed by a water-based one-component white topcoat with a wet film thickness of 100-120 micrometers and dried at 40°C for 4 hours, thus obtaining the coating system. The resulting coating system was then baked at 65°C for 2 hours and evaluated using a cross-cut test according to ASTM D3359, rated on a scale of 0-5, with 0 being the best and 5 the worst.

[0097] Raw materials:

[0098] The materials used in the embodiments of this application are shown below:

[0099] Polyvinyl alcohol The polyvinyl alcohol 2488 purchased from Chengdu Blue Whale Technology has a tensile strength of 25 MPa, a degree of alcoholysis of 85-95%, and a weight-average molecular weight between 170,000 and 220,000.

[0100] Preparation of fillers :

[0101] 30 parts by weight of kaolin, 30 parts by weight of talc, 10 parts by weight of magnesium aluminum silicate, and 30 parts by weight of calcium carbonate are mixed. The resulting mixture is then placed in a muffle furnace and sintered at 600-800℃ for 12-24 hours. The sintered material is then cooled, pulverized, and sieved to form the desired filler. The obtained filler has a layered structure with a specific surface area of ​​1-20 m². 2 / g, with a particle size of 0.5-4μm and a shear modulus of 0.30-0.35GPa.

[0102] Reference polyvinyl alcohol The polyvinyl alcohol 1788 purchased from Chengdu Blue Whale Technology has a tensile strength of less than 20 MPa.

[0103] Control packing 1 Kaolin has a layered structure and its shear modulus is less than 0.30 GPa.

[0104] Control packing 2 Calcium carbonate has a spherical structure and its shear modulus is less than 0.1 GPa.

[0105] Aqueous anionic emulsion HX8016 was purchased from Guangdong Huaguoshan Environmental Protection Technology Co., Ltd.

[0106] Aqueous hydroxy acrylic emulsion HX2006 was purchased from Guangdong Huaguoshan Environmental Protection Technology Co., Ltd.

[0107] HDI type waterborne curing agent XP2655 was purchased from Covestro Polymers (China) Co., Ltd.

[0108] IPDI type water-based curing agent : Purchased from Covestro Polymers (China) Co., Ltd. 401-70;

[0109] Waterborne epoxy resin HDE8619 was purchased from Shanghai Handai Chemical Co., Ltd.

[0110] Epoxy curing agent HDH6813B was purchased from Shanghai Handai Chemical Co., Ltd.

[0111] Film-forming aids General industrial products;

[0112] Additives General industrial products;

[0113] pigment General industrial products;

[0114] High-boiling-point slow-drying solvents General industrial products

[0115] Water-based single-component white primer : Self-produced ED1635-9043; and

[0116] Water-based single-component white topcoat : Self-produced EX1630-9323.

[0117] Treatment of wood substrates

[0118] Pine planks purchased from a timber market were kiln-dried. Samples measuring 15 cm x 15 cm x 1.5 cm were cut from the dried planks and conditioned to constant weight under conditions of 25°C, 60% relative humidity (RH), and an air velocity of 1.8 m / s. The equilibrium moisture content of the sample was 11%. A strip sander, purchased from 3M, was used. T The sample was sanded with Utility Cloth Sheet 240 grit sandpaper and cleaned with an air gun.

[0119] Water-based wood sealing primers and their coating systems :

[0120] As shown in Table 1 below, polyvinyl alcohol, waterborne anionic emulsion, waterborne hydroxyl acrylic emulsion, and waterborne epoxy resin were used as resin components and mixed with fillers, film-forming aids, additives, pigments, and water, respectively, to obtain waterborne wood sealing primers. Then, the obtained waterborne wood sealing primers were combined with corresponding silane coupling agents or curing agents to obtain the waterborne wood sealing primers to be tested.

[0121] Next, the obtained sealing primer to be tested was coated onto the treated pine substrate with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours; then, a water-based one-component white primer was coated with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours, and a water-based one-component white topcoat was coated with a wet film thickness of 100-120 micrometers and dried at 40°C for 4 hours, thereby obtaining the coating system.

[0122] Then, according to the test section above, the adhesion, oiling, and bubbling properties of the above-mentioned coating system were measured, and the results are summarized in Table 1.

[0123]

[0124] As can be seen from the results in Table 1, the water-based wood sealing system formed by combining a preform with a lamellar structure having a shear tensile modulus greater than 0.3 GPa with polyvinyl alcohol having a tensile strength greater than 20 MPa exhibits particularly excellent sealing effects on pine substrates, especially pine substrates with knots. For example, after baking at 65°C for 2 hours, the sealing coating formed by the above-mentioned water-based wood sealing primer does not produce oil or blister. Figure 9-10 As shown.

[0125] In comparison, water-based wood sealing systems formed by polyvinyl alcohol (PVA) with a tensile modulus greater than 20 MPa, combinations of PVA with a tensile modulus greater than 20 MPa and kaolin with a lower shear modulus, combinations of PVA with a tensile modulus greater than 20 MPa and spherical particulate fillers with a significantly lower shear modulus, and combinations of preforms with a lamellar structure and PVA with a tensile modulus less than 20 MPa, all exhibit a certain sealing effect on pine substrates, especially knotted pine substrates. However, after baking at 65°C for 2 hours, the sealing coatings formed by the above-mentioned water-based wood sealing primers either exhibit oil seepage or blistering problems, failing to meet current market demands. Figure 5-8 As shown.

[0126] Furthermore, the overall performance of sealing coatings formed by commercially available water-based wood sealing primers, which are composed of water-based anionic emulsions, water-based hydroxyl acrylic emulsions, or epoxy resins, is significantly worse. In particular, after baking at high temperatures for a period of time, the adhesion and oiliness of the knotted areas decrease significantly. Figure 1-4 As shown.

[0127] The effect of filler shear tensile modulus on the sealing effect of sealing primer

[0128] To verify the sealing effect of fillers with different shear tensile moduli, the inventors formulated an aqueous sealing primer containing different fillers. Specifically, the aqueous sealing primer contains 40% by weight of polyvinyl alcohol, 5.0% by weight of film-forming resin, 3.0% by weight of auxiliary additives, 10% by weight of different fillers, and 42% by weight of water.

[0129] The obtained sealing primer was applied to the treated pine substrate with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours. Then, a water-based one-component white primer was applied with a wet film thickness of 100-120 micrometers and dried at 40°C for 2 hours, and a water-based one-component white topcoat was applied with a wet film thickness of 100-120 micrometers and dried at 40°C for 4 hours to obtain the coating system.

[0130] Then, according to the test section above, the adhesion, oiling, and bubbling properties of the above-mentioned coating system were measured, and the results are summarized in Table 2.

[0131] Table 2: Effect of filler properties on sealing performance

[0132]

[0133] As can be seen from the results in Table 2, the properties of the filler, especially the shear tensile modulus of the filler, have a significant impact on the sealing effect of the sealing coating. When the shear tensile modulus of the filler is greater than 0.3 GPa, the oil exudation and bubbling performance of the water-based wood sealing primer prepared with it is significantly improved and the probability is greatly reduced.

[0134] Although the present invention has been described with reference to numerous embodiments and examples, those skilled in the art will recognize that other embodiments can be designed based on the disclosure of the present invention without departing from the scope and spirit of the invention.

Claims

1. A water-based wood sealing primer, comprising: At least one film-forming resin, at least one filler, at least one aqueous medium, and optionally at least one additional additive. in, The at least one filler has a lamellar structure and a shear modulus of elasticity of not less than 0.3 GPa, which is determined according to ISO 1421:2016 based on the prepared sealing primer sample. The at least one film-forming resin has a tensile strength of at least 20 MPa, which is determined according to GB / T 1040.3-2006 based on the prepared sealing primer sample.

2. The water-based wood sealing primer as described in claim 1, wherein, The at least one filler has a shear modulus in the range of 0.3 GPa to 0.35 GPa, preferably 60% or more, more preferably 60% to 130% higher than that of conventional spherical fillers.

3. The water-based wood sealing primer as described in claim 1, wherein, The specific surface area of the at least one filler is in the range of 1 to 50 m 2 / g, preferably in the range of 1 to 20 m 2 / g.

4. The water-based wood sealing primer as described in claim 1, wherein, The median particle size of the at least one filler is in the range of 0.5-4 micrometers.

5. The water-based wood sealing primer as described in claim 1, wherein, The at least one filler is a preform formed by high-temperature calcination and pulverization of one or more inorganic materials, preferably all of kaolin, calcium carbonate, talc, and magnesium aluminum silicate.

6. The water-based wood sealing primer as described in claim 1, wherein, The at least one filler is present in an amount of at least 5% by weight but not more than 40% by weight relative to the total weight of the water-based wood sealing primer, preferably in an amount of 10% to 30% by weight, and more preferably in an amount of 10% to 20% by weight.

7. The water-based wood sealing primer as described in any one of claims 1 to 6, wherein, The at least one film-forming resin has a tensile strength in the range of 20 MPa to 35 MPa, which is tested according to GB / T 1040.3-2006 based on the prepared sealing primer sample.

8. The water-based wood sealing primer as described in any one of claims 1 to 7, wherein, The at least one film-forming resin is incompatible with the oils in the wood-based substrate.

9. The water-based wood sealing primer as described in any one of claims 1 to 8, wherein, The at least one film-forming resin includes polyvinyl alcohol.

10. The water-based wood sealing primer as described in claim 9, wherein, The polyvinyl alcohol has at least one, preferably two, of the following properties: 85-95% degree of alcoholysis; and Weight-average molecular weight in the range of 150,000 to 250,000.

11. The water-based wood sealing primer as described in claim 9, wherein, The polyvinyl alcohol is in the form of powder, flakes, or flocculent solid.

12. The water-based wood sealing primer according to any one of claims 1 to 11, wherein, The film-forming resin is present in an amount of at least 10% by weight, preferably at least 25% by weight, but not exceeding 60% by weight, relative to the total weight of the waterborne wood sealing primer.

13. The water-based wood sealing primer according to any one of claims 1 to 12, wherein, Based on the total weight of the water-based wood sealing primer, the water-based wood sealing primer comprises: 10 to 60% by weight of the at least one film-forming resin; 5 to 25% by weight of the at least one filler; 25 to 85% by weight of at least one aqueous medium; and At least one additional additive, ranging from 0 to 10% by weight, wherein the at least one additional additive comprises pigments, thickeners, wetting agents, leveling agents, defoamers, dispersants, pH adjusters, mildew inhibitors, preservatives, or any combination thereof.

14. The water-based wood sealing primer as described in claim 1, wherein, After applying the water-based wood sealing primer to a pine substrate, preferably to the knots of the pine substrate, and baking it at 65°C for 2 hours, the resulting coating surface does not ooze oil or bubble.

15. A wooden product comprising: A wood-based substrate having at least one main surface with knots; and A sealing coating formed on at least a portion of the main surface with knots by a water-based wood sealing primer as described in any one of claims 1-14.

16. The wood product as claimed in claim 15, wherein, The wood-based substrate includes pine substrate, including knotted pine substrate, knotless pine substrate, or a combination thereof.

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