Electron beam curable bio-based coating compositions and pre-coated articles made therefrom

Abstract

The present application relates to an electron beam curable bio-based coating composition and a pre-coated article made therefrom. The electron beam curable bio-based coating composition comprises at least one urethane acrylate, at least one bio-based acrylate monomer, at least one nanocellulose, and optionally a first additional additive wherein the nanocellulose has a specific surface area of at least 200 m2 / g and has an aspect ratio of at least 20. The pre-coated article includes a substrate having at least one major surface; the transition layer is arranged on at least part of the main surface of the base material; and at least one electron beam curing topcoat disposed on at least a portion of the surface of the transition layer wherein the electron beam curing topcoat is formed from the electron beam curable bio-based coating composition according to the present invention.

Description

Technical Field

[0001] The present invention belongs to the field of radiation-curable coating compositions, and in particular, relates to an electron beam-curable bio-based coating composition and a pre-coated product made thereof. Background Art

[0002] Electron beam curing (EB curing) is an advanced technology that uses a high-energy electron beam (typically in the energy range of 50–300 keV) to irradiate a material, inducing rapid chemical crosslinking or polymerization reactions, thereby achieving material curing. This process involves the interaction (e.g., ionization and excitation) of the electron beam with the material, including monomers or polymers containing ethylenically unsaturated groups in the coating composition, to generate active free radicals or ions. These radicals trigger crosslinking or polymerization of the monomers or polymers containing ethylenically unsaturated groups, ultimately forming a coating with a three-dimensional network structure. EB curing offers advantages such as fast curing speed (<5ms), no heat generation, no need for initiators, environmental friendliness, and yellowing resistance. Furthermore, compared to traditional curing coatings, this radiation-curable coating is also suitable for coating heat-sensitive substrates and can be polymerized using a highly automated, assembly-line process. Therefore, electron beam-curable coating compositions have broad application prospects.

[0003] The electron beam curing process of an electron beam-curable coating composition is typically performed under a conventional electron beam curing environment, such as a nitrogen atmosphere, where the oxygen content is generally not greater than 500 ppm. However, even when electron beam curing is performed under such an environment, oxygen inhibition is still an unavoidable problem.

[0004] For this reason, the coatings industry continues to need improved electron beam curable coating compositions. Summary of the Invention

[0005] The present application provides an electron beam-curable coating composition and a pre-coated product made therefrom. The obtained pre-coated product has broad application prospects in home decoration fields such as decorative panels, cabinet panels or furniture panels.

[0006] According to a first aspect of the present invention, there is provided an electron beam curable bio-based coating composition comprising: at least one polyurethane acrylate, at least one bio-based acrylate monomer, at least one nanocellulose and an optional first additional additive, wherein the nanocellulose has at least 200 m 2 / g specific surface area and an aspect ratio of at least 20.

[0007] According to a second aspect of the present invention, a pre-coated product is provided, comprising: a substrate having at least one major surface; at least one transition layer, the transition layer being disposed on at least a portion of the major surface of the substrate; and at least one electron beam cured topcoat, the electron beam cured topcoat being disposed on at least a portion of the surface of the transition layer, wherein the electron beam cured topcoat is formed from an electron beam curable bio-based coating composition according to the first aspect of the present invention.

[0008] According to a third aspect of the present invention, there is provided a product having the pre-coated product according to the second aspect of the present invention on its surface. Preferably, the product comprises a decorative board, a cabinet board or a furniture panel.

[0009] The inventors of the present application first disclosed that, in the formulation of an electron beam curable bio-based coating composition, nanocellulose is added and the specific surface area of ​​the nanocellulose is specifically selected to be at least 200 m 2 / g and an aspect ratio of at least 20 can significantly accelerate the curing reaction of electron beam-curable bio-based coating compositions and shorten the oxygen exposure time during the curing process. At the same time, the nanocellulose can also form a physical barrier in the cured coating, effectively reducing oxygen inhibition. The resulting cured coating has significantly improved scratch resistance, even when the coating is relatively thin.

[0010] Without being bound by any theory, the inventors of this application speculate that in the electron beam-curable bio-based coating composition according to the present invention, nanocellulose has a high specific surface area and can provide more reaction sites. Therefore, after it is combined with the radiation-curable components (including polyurethane acrylate and bio-based acrylate monomers), it can promote rapid free radical crosslinking, for example, shortening the curing time to less than 5 milliseconds, thereby greatly reducing the contact time between oxygen and free radicals. In addition, the nanocellulose has a high aspect ratio and a three-dimensional cross-linked structure, which can form a dense barrier in the electron beam-cured coating, thereby significantly reducing the permeation rate of oxygen molecules. As a result, the oxygen inhibition problem of the electron beam-curable coating composition is reduced.

[0011] The inventors of the present application were even more surprised to find that in the electron beam-curable bio-based coating composition, the hydroxyl groups (-OH) rich on the surface of the nanocellulose can react with the free isocyanate groups (-NCO) in the polyurethane acrylate to form a covalent bond, thereby enhancing the interfacial bonding force between the two phases; this chemical bonding not only improves the mechanical properties of the composite material (such as peel strength), but also allows the nanocellulose to be evenly dispersed during the free radical polymerization reaction initiated by the high-energy electron beam. The evenly dispersed nanocellulose can provide more reaction sites, promote the formation of a cross-linked network, greatly improve the cross-linking density of the coating, and improve the hardness and adhesion of the overall coating.

[0012] Furthermore, the inventors of this application have surprisingly discovered that the introduction of the aforementioned nanocellulose into an electron beam-curable bio-based coating composition can significantly enhance the interlayer bonding between the electron beam-cured topcoat formed from the coating composition and the underlying transition layer. Without being bound by any theory, the inventors of this application have discovered that when an electric field is applied during the curing of the electron beam-curable coating composition, the nanocellulose in the coating composition undergoes a specific vertical alignment along the interface, thereby forming a "barb structure" that penetrates into the transition layer, significantly enhancing the interlayer bonding between the electron beam-cured topcoat formed from the coating composition and the underlying transition layer. This was difficult to predict prior to the present application.

[0013] On the other hand, the inventors of the present application also disclosed that, in a pre-coated product comprising an electron beam cured topcoat, by adding a specific transition layer between the substrate and the electron beam cured topcoat, the difference in physical properties between the substrate and the electron beam cured topcoat can be significantly reduced or the interlayer bonding strength between the substrate and the electron beam cured topcoat can be significantly enhanced, thereby making it possible for the resulting pre-coated product to basically not or not at all fail under thermal expansion and contraction or bending stress, such as interlayer separation.

[0014] The details of one or more embodiments of the present application are set forth in the following description. Other features, objects, and advantages of the present application will become apparent from the description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram showing a “barb structure” formed when the electron beam curable coating composition according to the present invention is cured by applying an electric field. definition

[0016] As used herein, unless otherwise indicated, "a," "an," "the," "at least one," and "one or more," as well as when not using a quantifier, are used interchangeably. Thus, for example, a coating composition comprising "an" additive can be interpreted to mean that the coating composition comprises "one or more" additives. Unless otherwise indicated herein, the use of the singular form herein is intended to include the plural form.

[0017] Unless expressly stated otherwise, the use of the terms "comprising," "including," "containing," and "having" should generally be interpreted as open-ended and non-restrictive. For example, where a composition is described as comprising or including specific components, it is contemplated that optional components not contemplated by the present invention are not excluded from the composition, and that the composition may consist of or be composed of the components involved; or where a method is described as comprising or including specific process steps, it is contemplated that optional process steps not contemplated by the present invention are not excluded from the method, and that the method may consist of or be composed of the process steps involved.

[0018] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value can serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0019] Unless otherwise indicated, each point or individual value between the endpoints of a range is included in the range. For example, a range of 1 to 5 encompasses the values ​​1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. Moreover, a disclosed numerical range includes all subset ranges within the broader range, for example, a range of 1 to 5 includes the subranges 1 to 4, 1.5 to 4.5, 1 to 2, etc. Thus, each point or individual value can be combined as a lower or upper limit with any other point or individual value, or with other lower or upper limits, and the resulting range is expressly disclosed herein.

[0020] As used herein, the term "or" is inclusive. That is, the phrase "A or (or) B" means "A, B, or both A and B," which may also be abbreviated as "A and / or B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist). In contrast, the exclusive "or" is represented herein, for example, by terms such as "either A or B" and "one of A or B."

[0021] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered as included in the disclosure of the present application. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered as included in the disclosure of the present application.

[0022] Unless otherwise specified, in this application, the terms "first", "second", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0023] In this application, the terms "plurality" and "multiple" refer to two or more.

[0024] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0025] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0026] As used herein, "bio-based modified polyurethane acrylate" or "bio-based acrylate monomer" refers to polyurethane acrylates or acrylate monomers modified with bio-based materials. Bio-based materials are organic materials that contain a certain amount of non-fossil carbon derived from biomass, such as plants, crops, wood waste, animal waste, fats, and vegetable oils.

[0027] For purposes of this disclosure, "biobased carbon content" refers to the mass percentage of carbon derived from renewable resources (also referred to as biochar) in a material, as determined according to ASTM D6866-16, relative to the total organic carbon in the material. Note that when determining the biobased carbon content of a material, the organic carbon does not include any carbon derived from inorganic sources, such as carbonates.

[0028] In the context of "bio-based modified polyurethane acrylate", "bio-based carbon content" is the mass percentage of carbon from renewable resources in the bio-based modified polyurethane acrylate particles relative to the total organic carbon in the bio-based modified polyurethane acrylate.

[0029] In the present invention, the term "bio-based modified polyurethane acrylate" refers to a polymer prepared using a bio-based polyol as one of the raw materials, combined with isocyanate and acrylate. By way of example, the bio-based polyol may include, but is not limited to, one or more of aliphatic polyester polyols, polycaprolactone polyols (PCL), propylene oxide / ethylene oxide derivatives, and specialty polyether polyols.

[0030] As used herein, the term "urethane acrylate" refers to a polymer having a backbone containing several urethane linkages (-NH-CO-O-) and one or more acrylate functional groups in the backbone and / or pendant segments. Typically, the backbone of the polymer may contain ester, ether, urea, allophanate, isocyanurate, or other linkages in addition to the urethane linkages.

[0031] As used herein, the term "acrylate monomer" is a general term for esters of acrylic acid and its homologues, such as methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate, etc. Therefore, unless otherwise indicated, "acrylate" includes both acrylate and methacrylate.

[0032] As used herein, the term "(bio-modified) polyurethane acrylate" means that the polyurethane acrylate may be bio-modified or not bio-modified.

[0033] When used in the context of a substrate, the term "major surface" is the surface formed by a certain length and a certain width dimension of the substrate that is used to provide decoration.

[0034] As used herein, the term "topcoat" refers to a coating that can be applied to a transition layer and dried, crosslinked, or otherwise hardened to form a decorative or protective outermost finish layer. Further, such a topcoat is capable of withstanding extended outdoor exposure without showing visible, unsatisfactory degradation.

[0035] When used in the context of "applying ...on a coating layer," the term "on" includes applying one paint or coating composition directly or indirectly onto another coating layer.

[0036] When used in this description and claims, the terms "comprises" and "includes" and variations thereof do not have a limiting meaning.

[0037] Throughout this application, numerical ranges defined by endpoints include all values ​​within that range, e.g., a range of 1 to 5 encompasses the values ​​1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. Furthermore, a disclosed numerical range includes all subranges within the broader range, e.g., a range of 1 to 5 includes subranges 1 to 4, 1.5 to 4.5, 1 to 2, etc.

[0038] The terms "preferred" and "preferably" refer to embodiments of the invention that may offer certain benefits under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention. DETAILED DESCRIPTION

[0039] According to a first aspect of an embodiment of the present invention, there is provided an electron beam curable bio-based coating composition comprising: at least one polyurethane acrylate, at least one bio-based acrylate monomer, at least one nanocellulose and an optional first additional additive, wherein the nanocellulose has at least 200 m 2 / g specific surface area and an aspect ratio of at least 20.

[0040] Cellulose is the world's most abundant natural polymer compound and the most widely distributed and abundant polysaccharide in nature. Structurally, cellulose is a high-molecular-weight homopolymer composed of β-1,4-anhydro-D-pyranose glucose units, typically exhibiting a chair-shaped conformation and possessing a unique three-dimensional cross-linked porous structure. Due to the presence of a large number of free active hydroxyl groups at the C2, C3, and C6 positions on the surface, strong hydrogen bonds exist between the linear cellulose molecular chains. The linear chain structure and rich functional groups allow for surface modification to produce many cellulose derivatives, such as cellulose acetate, carboxymethyl cellulose, and hydroxypropyl methylcellulose. Furthermore, mechanical treatment or chemical acid or enzyme treatment can yield cellulose nanofibers, bacterial cellulose, and cellulose nanocrystals with smaller structural scales, which can meet the application needs of cellulose in various related fields.

[0041] Nanocellulose is a general term for cellulose with any dimension at the nanometer level (e.g., less than 100 nm). It has both the properties of cellulose and those of nanoparticles. Nanocellulose can be a polymer nanomaterial extracted from wood, cotton, and other natural materials through one or more chemical, physical, or biological methods. Compared with ordinary wear-resistant powders, nanocellulose has advantages such as a wide range of sources, low cost, biodegradability, high modulus, and high specific surface area. Therefore, it is an excellent alternative to traditional petrochemical resources and can effectively alleviate problems such as environmental pollution and the shortage of petrochemical resources.

[0042] The inventors of the present application first disclosed that, in the formulation of an electron beam curable bio-based coating composition, nanocellulose is added and the specific surface area of ​​the nanocellulose is specifically selected to be at least 200 m 2 / g and an aspect ratio of at least 20 can significantly accelerate the curing reaction of electron beam-curable bio-based coating compositions and shorten the oxygen exposure time during the curing process. At the same time, the nanocellulose can also form a physical barrier in the cured coating, effectively reducing the problem of oxygen inhibition. The resulting cured coating has significantly improved scratch resistance, even when the coating is relatively thin.

[0043] Without being bound by any theory, the inventors of this application speculate that in the electron beam-curable bio-based coating composition according to the present invention, nanocellulose has a high specific surface area and can provide more reaction sites. Therefore, after it is combined with the radiation-curable component (including bio-based modified polyurethane acrylate and bio-based acrylate monomer), it can promote rapid free radical crosslinking, for example, shortening the curing time to less than 5 milliseconds, thereby greatly reducing the contact time between oxygen and free radicals. In addition, the nanocellulose has a high aspect ratio and a three-dimensional crosslinked structure, which can form a dense barrier in the electron beam-cured coating, thereby significantly reducing the permeation rate of oxygen molecules. As a result, the oxygen inhibition problem of the electron beam-curable coating composition is reduced.

[0044] In an embodiment of the present invention, the nanocellulose has a high specific surface area. In this article, the specific surface area of ​​nanocellulose refers to the total surface area per unit mass of nanocellulose material, including the sum of the surface area of ​​the external surface and the internal pore structure, and its unit is square meters per gram (m2 / g). 2 The specific surface area of ​​the nanocellulose contained in the electron beam curable coating composition according to the present invention is at least 200 m 2 / g, preferably at least 220m 2 / g, more preferably at least 230m 2 / g, and more preferably at least 250m 2 / g; but it should not be too high, for example, not more than 600m 2 / g, preferably not more than 550m 2 / g, more preferably not more than 500m 2 / g, and more preferably not more than 450m 2 / g. The specific surface area of ​​the nanocellulose can be measured by BET nitrogen adsorption method, electron microscopy, and small-angle X-ray scattering method known to those skilled in the art. If the specific surface area of ​​nanocellulose is too low, it cannot provide enough reaction sites, cannot effectively promote rapid cross-linking of free radicals, and then cannot effectively shorten the contact time between oxygen and curing time; if the specific surface area of ​​nanocellulose is too high, it will adversely affect the processing performance of the coating composition formed by its formulation due to the fine powder particles. Therefore, in some embodiments according to the present invention, the at least one nanocellulose has a specific surface area of ​​200 to 400 m 2 / g range of specific surface area.

[0045] In an embodiment according to the present invention, the nanocellulose has a higher aspect ratio. In this article, aspect ratio refers to the ratio of the length of nanocellulose to the diameter, which is a common parameter for describing the shape of particles. Typically, the aspect ratio of spherical particles is close to that in the range of 0.9 to 1.1, the aspect ratio of quasi-spherical particles is greater than that in the range of 1.1 to 1.3, the aspect ratio of rod-shaped particles is greater than that in the range of 1.3 to 5, and the aspect ratio of elongated particles is greater than that in the range of 5 to 10. Compared with the above-mentioned conventional particulate fillers, the aspect ratio of the nanocellulose included in the electron beam curable coating composition according to the present invention is much higher, for example, at least 20, preferably at least 21, more preferably at least 22, and even more preferably at least 25, but not too high, for example, no more than 150, preferably no more than 140, more preferably no more than 130, and even more preferably no more than 120. The aspect ratio of the nanocellulose can be measured by electron microscopy or small-angle X-ray scattering known to those skilled in the art. If the aspect ratio of the nanocellulose is too low, it will not form a dense barrier in the electron beam cured coating, and thus will not effectively reduce the permeation rate of oxygen molecules. If the aspect ratio of the nanocellulose is too high, the powder particles are too long, which will adversely affect the processing performance of the coating composition formed by the nanocellulose. Therefore, in some embodiments according to the present invention, the at least one nanocellulose has an aspect ratio in the range of 20 to 100.

[0046] In some embodiments according to the present invention, the at least one nanocellulose has a length in the range of 1 to 5 microns. By way of example, the at least one nanocellulose has a length of 1.1 microns, 1.5 microns, 2.0 microns, 2.5 microns, 3 microns, 3.5 microns, 4 microns, 4.5 microns, or a range between any two of the foregoing values.

[0047] In some embodiments according to the present invention, the at least one nanocellulose has a diameter in the range of 30-50 nm. By way of example, the at least one nanocellulose has a diameter of 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, or within a range formed by any two of the foregoing values.

[0048] In some embodiments according to the present invention, the surface of the nanocellulose is rich in hydroxyl groups (-OH). The inventors of the present application were also surprised to find that in the electron beam curable bio-based coating composition, the hydroxyl groups (-OH) rich in the surface of the nanocellulose can react with the free isocyanate groups (-NCO) of the polyurethane acrylate component contained in the coating composition to form a covalent bond, thereby enhancing the interfacial bonding force of the two phases; this chemical bonding not only improves the mechanical properties (such as peel strength) of the composite material, but also makes the nanocellulose uniformly dispersed during the free radical polymerization reaction initiated by the high-energy electron beam. The uniformly dispersed nanocellulose can provide more reaction sites, promote the formation of a cross-linked network, greatly improve the cross-linking density of the coating film, and improve the hardness and adhesion of the overall coating film.

[0049] In addition, the inventors of the present application were even more surprised to find that the introduction of the above-mentioned nanocellulose into an electron beam-curable bio-based coating composition can significantly enhance the interlayer bonding strength between the electron beam-cured topcoat formed by the coating composition and the lower transition layer. Without being bound by any theory, the inventors of the present application found that when an electric field is applied during the curing of the electron beam-curable coating composition, the nanocellulose in the coating composition will be arranged vertically along a specific interface, forming a "barb structure" that penetrates the transition layer, thereby significantly enhancing the interlayer bonding strength between the electron beam-cured topcoat formed by the coating composition and the lower transition layer, which was difficult to predict before the present application. Therefore, the topcoat formed by the electron beam-curable bio-based coating composition according to the present invention has a "barb structure" formed by the nanocellulose on the surface near the transition layer that penetrates at least a portion of the transition layer.

[0050] According to an embodiment of the present invention, the above-mentioned nanocellulose can be prepared by any method known in the art that is suitable for preparing nanocellulose. As an exemplary illustration, the nanocellulose can be prepared by acid hydrolysis, mechanical treatment, and enzymatic hydrolysis. In some embodiments according to the present invention, nanocellulose can be obtained as follows: providing cellulose powder having a whiteness greater than or equal to 80%; mixing and reacting the obtained cellulose powder with a modified solution, washing and removing impurities, and then adjusting the pH to neutral, and grinding and cutting to obtain nanocellulose. The above-mentioned nanocellulose can also be commercially available, such as CNC nanocellulose purchased from Shandong Shengquan Group.

[0051] Preferably, the electron beam curable bio-based coating composition comprises, relative to the total weight of the coating composition, about 1.0 wt % to about 5.0 wt % of the nanocellulose. The inventors of the present application have found that the above-mentioned nanocellulose has an excellent effect of reducing oxygen inhibition. If the amount of nanocellulose is too low, its effect of reducing oxygen inhibition may be insufficient; if the amount of nanocellulose is too high, it may cause a significant increase in the viscosity of the coating composition, which is not conducive to coating. Therefore, in some embodiments according to the present application, the electron beam curable bio-based coating composition comprises, relative to the total weight of the coating composition, about 1.0 wt % to about 4.5 wt % of the nanocellulose, about 1.0 wt % to about 4.0 wt % of the nanocellulose, about 1.0 wt % to about 3.5 wt % of the nanocellulose, about 1.0 wt % to about 3.0 wt % of the nanocellulose, about 1.0 wt % to about 2.5 wt % of the nanocellulose, about 1.0 wt % to about 2.0 wt % of the nanocellulose, about 1.0 wt % to about 1.5 wt % of the nanocellulose. % to about 4.5 wt % of the nanocellulose, about 2.0 wt % to about 4.0 wt % of the nanocellulose, about 2.0 wt % to about 3.5 wt % of the nanocellulose, about 2.0 wt % to about 3.0 wt % of the nanocellulose, about 2.0 wt % to about 2.5 wt % of the nanocellulose, about 3.0 wt % to about 4.5 wt % of the nanocellulose, about 3.0 wt % to about 4.0 wt % of the nanocellulose, about 3.0 wt % to about 3.5 wt % of the nanocellulose, about 4.0 wt % to about 4.5 wt % of the nanocellulose.

[0052] In an embodiment according to the present invention, in addition to the above-mentioned nanocellulose, the electron beam-curable bio-based coating composition further comprises at least one polyurethane acrylate, at least one bio-based acrylate monomer and an optional first additional additive.

[0053] In some embodiments according to the present invention, the at least one polyurethane acrylate can be conventional non-bio-based polyurethane acrylate in the coating field, or it can be bio-based polyurethane acrylate, preferably bio-based modified polyurethane acrylate, to provide environmental benefits. The inventors of the present application were surprised to find that in the preparation of the bio-based coating composition that can be cured by electron beam, by further introducing (bio-based modification) polyurethane acrylate synthesized as raw materials via polyol (preferably bio-based polyol), isocyanate and acrylate monomer, the hydroxyl group (-OH) in the above-mentioned nano-cellulose can be reacted with the free isocyanate group (-NCO) in (bio-based modification) polyurethane acrylate to form a covalent bond, thereby enhancing the two-phase interface bonding force. This chemical bonding not only improves the mechanical properties (such as peel strength) of the composite material, but also promotes the uniform dispersion of nano-cellulose during the free radical polymerization reaction initiated by high-energy electron beams, and uniformly dispersed nano-cellulose can provide more reaction sites, promote the formation of a cross-linked network, greatly improve the crosslinking density of the film, and improve the hardness and adhesion of the overall film. Thus, in some embodiments according to the present invention, the polyurethane acrylate has reactive isocyanate (NCO) groups.

[0054] As mentioned above, the term "(bio-based modified) polyurethane acrylate" refers to a polymer prepared using non-bio-based polyols or bio-based polyols as one of the core raw materials in combination with isocyanates and acrylates commonly used in the art.

[0055] As an example, the polyol may include, but is not limited to, aliphatic polyester polyols, polycaprolactone polyols (PCL), propylene oxide / ethylene oxide derivatives, specialty polyether polyols, polycarbonate diols, and acrylate polyols. In some preferred embodiments of the present invention, the polyol is a bio-based polyol, including, but not limited to, bio-based aliphatic polyester polyols, bio-based polycaprolactone polyols (PCL), bio-based propylene oxide / ethylene oxide derivatives, and bio-based specialty polyether polyols. As used in this article, bio-based aliphatic polyester polyols are prepared by polycondensation of bio-based dibasic acids (such as adipic acid) and bio-based diols (such as 1,3-propylene glycol); bio-based polycaprolactone polyols (PCL) are prepared by ring-opening polymerization of bio-based caprolactone monomers; bio-based propylene oxide / ethylene oxide derivatives are formed by ring-opening polymerization of propylene oxide (PO) or ethylene oxide (EO) starting from bio-based initiators (such as glycerol, sorbitol); bio-based specialty polyether polyols are formed by copolymerization of oxidized olefins starting from bio-based flame retardant initiators (such as phosphorus and nitrogen compounds); polycarbonate diols are prepared by alcoholysis polymerization using urea and diols under heating and catalysts; acrylate polyols are copolymerized by introducing hydroxyalkyl acrylate monomers.

[0056] In some embodiments according to the present invention, the (bio-based modified) polyurethane acrylate synthesized from (bio-based) polyols, isocyanates, and acrylate monomers, as described above, refers to a polymer having a backbone containing several carbamate linkages (-NH-CO-O-) and one or more, preferably two or more, acrylate functional groups in the backbone and / or pendant segments. Typically, the backbone of the polymer may optionally contain ester, ether, urea, allophanate, isocyanurate, or other linkages in addition to the carbamate linkages.

[0057] In some embodiments according to the present invention, the at least one polyurethane acrylate is difunctional or multifunctional. In one embodiment according to the present invention, the at least one polyurethane acrylate is difunctional. In another embodiment according to the present invention, the at least one polyurethane acrylate is trifunctional.

[0058] In some preferred embodiments of the present invention, the at least one polyurethane acrylate may be further modified with bio-based materials, and may further include a bio-based chain extender such as ricinoleic acid acrylate. The presence of such a bio-based chain extender can enhance intermolecular hydrogen bonding and strengthen the peel strength between the topcoat and the underlying transition layer.

[0059] In some embodiments according to the present invention, the at least one bio-based modified polyurethane acrylate has a weight average molecular weight in the range of 10,000 to 30,000. The weight average molecular weight is determined by GPC.

[0060] In some embodiments according to the present invention, the bio-based carbon content of the at least one bio-based modified polyurethane acrylate is in the range of 20-50%. The bio-based carbon content is determined according to ASTM D6866-16. As described above, the bio-based carbon content is the mass percentage of carbon from renewable resources in the bio-based modified polyurethane acrylate particles to all organic carbon of the bio-based modified polyurethane acrylate. In a specific embodiment according to the present invention, the bio-based carbon content of the at least one bio-based modified polyurethane acrylate is 40-50%. In another specific embodiment according to the present invention, the bio-based carbon content of the at least one bio-based modified polyurethane acrylate is 35-45%.

[0061] According to an embodiment of the present invention, the above-mentioned bio-based modified polyurethane acrylate can be prepared by any method known in the art suitable for preparing bio-based resins, or can be commercially available, such as the product with the brand name S7302NS from Sartomer or the product with the brand name EBECRYL 8807 from Allnex.

[0062] Preferably, the electron beam curable bio-based coating composition comprises, relative to the total weight of the coating composition, about 10 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate. In some embodiments according to the present application, the electron beam curable bio-based coating composition comprises, relative to the total weight of the coating composition, about 12 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 14 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 16 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 18 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 20 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 22 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate. % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 24 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 26 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 28 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 30 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 35 wt % to about 40 wt % of the (bio-based modified) polyurethane acrylate, about 12 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 14 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate polyurethane acrylate, about 16 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 18 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 20 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 22 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 24 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 26 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, about 28 wt % to about 30 wt % of the (bio-based modified) polyurethane acrylate, % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 12 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 14 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 16 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 18 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 20 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 22 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate, about 24 wt % to about 25 wt % of the (bio-based modified) polyurethane acrylate.

[0063] In some embodiments according to the present invention, the bio-based acrylate monomer is an acrylate monomer derived from a vegetable oil, preferably, the vegetable oil is selected from carona oil, castor oil, dehydrated castor oil, coconut oil, corn oil, cottonseed oil, peanut oil, linseed oil, ricinene oil, safflower oil, soybean oil, sunflower oil, tall oil, tung oil, walnut oil, wood oil or a combination thereof.

[0064] In some embodiments according to the present invention, the bio-based acrylate monomer is difunctional or multifunctional.

[0065] According to an embodiment of the present invention, the above-mentioned bio-based acrylate monomer can be prepared by any method known in the art suitable for preparing bio-based monomers, or can be commercially available, such as the product with the brand name S5101NS from Sartomer or the product with the brand name GPTA from Allnex.

[0066] Preferably, the electron beam curable bio-based coating composition comprises from about 10 wt% to about 40 wt% of the bio-based acrylate monomer, relative to the total weight of the coating composition. In some embodiments according to the present application, the electron beam-curable bio-based coating composition comprises, relative to the total weight of the coating composition, about 20 wt % to about 40 wt % of the bio-based acrylate monomer, about 22 wt % to about 40 wt % of the bio-based acrylate monomer, about 24 wt % to about 40 wt % of the bio-based acrylate monomer, about 26 wt % to about 40 wt % of the bio-based acrylate monomer, about 28 wt % to about 40 wt % of the bio-based acrylate monomer, about 30 wt % to about 40 wt % of the bio-based acrylate monomer, about 32 wt % to about 34 wt % of the bio-based acrylate monomer, about 36 wt % to about 40 wt % of the bio-based acrylate monomer, about 38 wt % to about 40 wt % of the bio-based acrylate monomer, about 30 wt % to about 40 wt % of the bio-based acrylate monomer, about 35 wt % to about 40 wt % of the bio-based acrylate monomer.

[0067] In some embodiments according to the present invention, the electron beam curable bio-based coating composition may further comprise a reactive diluent.

[0068] Optionally, the reactive diluent may include a multifunctional ethylenically unsaturated monomer, including but not limited to hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethoxylated hexanediol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, or a combination thereof.

[0069] The reactive diluent is present in an amount of 0 to 20 wt %, preferably 5 to 20 wt %, more preferably 10 to 20 wt %, based on the total weight of the electron beam curable bio-based coating composition.

[0070] The electron beam-curable bio-based coating composition according to an embodiment of the present application may further include a pigment and / or a first additional additive.

[0071] In the embodiments of the present application, “pigments and fillers” is a general term for pigments and fillers.

[0072] According to the present application, "filler" refers to any volume extender suitable for use in radiation-curable coating compositions, which may be inorganic, for example, in the form of particles. There are no particular restrictions on the shape of the particles, which may have any suitable shape. The average particle size of the filler may vary over a wide range, for example, in the range of about 10 nanometers to about 50 microns. In addition to acting as a volume extender, some fillers also impart one or more desired properties to the composition and / or the coating formed from the composition. For example, some fillers can improve chemical and / or physical properties, particularly the mechanical properties of the coating obtained from the composition. In this case, such fillers are also referred to as "reinforcing fillers." Suitable fillers may include, for example, silicates, sulfates, carbonates, and silicon dioxide. Suitable exemplary fillers include, for example, china clay, wollastonite, barite, calcium carbonate, diatomaceous earth, talc, barium sulfate, magnesium aluminum silicate, silicon dioxide, and any combination thereof.

[0073] According to the present application, "pigment" is an agent that provides color or hue to a radiation-curable coating composition. Suitable pigments may include one or more of iron oxide, carbon black, lead oxide, lead carbonate, zinc oxide, titanium oxide, ultramarine blue, chrome green, or chromium oxide, or a combination thereof.

[0074] According to certain embodiments of the present application, the total weight of the pigments and fillers may vary within a wide range, for example, the total weight thereof is in the range of about 0 wt % to about 20 wt %, preferably in the range of about 5 wt % to about 20 wt %, and more preferably in the range of about 8 wt % to 15 wt %, relative to the total weight of the electron beam (EB) curable bio-based coating.

[0075] According to the electron beam curable bio-based coating composition of the present application embodiment, it is also possible to optionally include conventional additives, which do not adversely affect the coating composition or the coating obtained therefrom. Suitable additives include, for example, those reagents that improve the processing performance or manufacturing performance of the composition, enhance the surface effect of the composition, improve the specific functional properties or characteristics (such as adhesion to the substrate) of the coating composition or the cured composition obtained therefrom, or reduce costs. The additives that can be included are, for example, wetting agents, defoamers, leveling agents, antioxidants, thixotropic agents, dispersants, adhesion promoters, thickeners, or combinations thereof. The content of each optional component is sufficient to achieve its intended purpose, but preferably, such content does not adversely affect the coating composition or the cured coating obtained therefrom. In a preferred embodiment, the electron beam curable bio-based coating composition of the present application can include defoamers, leveling agents, dispersants, ultraviolet absorbers, or any combination thereof as conventional additives. According to the application, the total amount of conventional additives is 0 wt % to about 10 wt %, preferably 0.1 wt % to about 10 wt %, relative to the gross weight of the composition.

[0076] Therefore, in one embodiment according to the present application, the electron beam curable bio-based coating composition comprises, relative to the total weight of the electron beam curable bio-based coating composition,

[0077] 10-40 wt. % of the at least one (bio-modified) polyurethane acrylate;

[0078] 10-40 wt. % of the at least one bio-based acrylate monomer;

[0079] 0-20 wt%, preferably 10-20 wt% of the reactive diluent;

[0080] 1-5 wt% of at least one nanocellulose; and

[0081] The additional additives in an amount of 0-40 wt % are selected from one or more of pigments, fillers, defoamers, leveling agents, dispersants, and ultraviolet absorbers.

[0082] The preparation of the electron beam-curable bio-based coating composition according to the embodiments of the present application can be achieved using any suitable mixing method known to those skilled in the art. For example, the bio-based electron beam-curable coating can be prepared by uniformly mixing a pigment, a dispersant, a bio-based acrylate monomer, etc., and grinding the mixture to a particle size of ≤15 μm; then sequentially adding a bio-based modified polyurethane acrylate, nanocellulose, silica, and other additives, and stirring the mixture to obtain the electron beam-curable bio-based coating composition.

[0083] According to the inventors of the present application, the electron beam-curable bio-based coating composition according to the embodiment of the present application is found to be even suitable for thin coating, and basically no oxygen inhibition occurs. It is well known that the thinner the coating, the more likely it is to undergo oxygen inhibition. According to the electron beam-curable bio-based coating composition according to the embodiment of the present application, due to the incorporation of specific nanocellulose, it can react in a short time after being applied with an electron beam of 200KeV and 20KGr under conventional electron beam curing environmental conditions to form a barrier, thereby effectively reducing oxygen permeability, making the EB coating film cross-linking density higher and the surface resistance better, so that the resulting cured coating has significantly higher surface scratch resistance, for example, the highest scratch resistance level 5 (6.0N load) can be obtained, and the surface scratch resistance is tested according to Section 4.42 of GB / T 17657-2022 "Test methods for physical and chemical properties of artificial boards and veneered artificial boards".

[0084] In some embodiments according to the present invention, the electron beam-curable bio-based coating composition, after curing, forms a coating having a hardness increase of 10-20% compared to a corresponding electron beam-curable bio-based coating composition without the nanocellulose. The hardness is determined by pencil hardness as measured in accordance with GB / T 6739-2022.

[0085] Pre-coated products

[0086] Another aspect of the present application provides a pre-coated product comprising: a substrate having at least one major surface; at least one transition layer disposed on at least a portion of the major surface of the substrate; and at least one electron beam cured topcoat disposed on at least a portion of the surface of the transition layer, wherein the electron beam cured topcoat is formed from an electron beam curable bio-based coating composition according to the first aspect of the present invention.

[0087] As a substrate for manufacturing a precoated product according to an embodiment of the present application, any suitable substrate known in the art for manufacturing precoated products can be used. The substrate has at least one major surface. As described above, the term "major surface" refers to a surface formed by a certain length and width of the substrate for providing a decoration. In an embodiment of the present invention, the substrate can be a heat-sensitive group, including but not limited to one or more of PP, PET, PE, PETG, PVC, PS, PMMA, and bleached kraft paper.

[0088] In conventional pre-coated products, the transition layer is usually flexible and elastic. Such a transition layer is prone to interfacial delamination with the rigid electron beam curable layer above it, and is particularly prone to failure under thermal expansion and contraction or bending stress. In view of the existence of the above problems, the inventors of the present application were surprised to find that the nanocellulose contained in the electron beam curable bio-based coating composition according to the present invention can significantly enhance the interlayer bonding force between the electron beam cured topcoat formed by the coating composition and the lower transition layer. Without being bound by any theory, the inventors of the present application found that when an electric field is applied during the curing of the electron beam curable coating composition, the nanocellulose in the coating composition will be arranged vertically along a specific interface; it can form a "barb structure" that penetrates into the transition layer. The schematic diagram of the barb structure is shown in FIG. Figure 1 As shown. Figure 1 In the example, the nanocellulose in the topcoat 1 partially penetrates the transition layer 2, forming a "barb structure." This barb structure significantly enhances the interlayer bonding between the electron beam-cured topcoat formed from the coating composition and the underlying transition layer, thereby substantially preventing interfacial delamination between the transition layer and the rigid electron beam-curable layer above it.

[0089] In addition, the inventors of the present application have also discovered that, in a pre-coated product comprising the above-mentioned electron beam cured topcoat, by adding a specific transition layer between the substrate and the electron beam cured topcoat, the difference in physical properties between the substrate and the electron beam cured topcoat can be further reduced or the interlayer bonding strength between the substrate and the electron beam cured topcoat can be enhanced, thereby making it possible for the resulting pre-coated product to basically not or not at all fail under thermal expansion and contraction or bending stress, such as interlayer separation.

[0090] In some embodiments of the present invention, the transition layer is formed of an aqueous coating composition comprising an aqueous polyurethane emulsion, a filler, deionized water, and an optional second additional additive.

[0091] As used herein, the term "aqueous emulsion" refers to an emulsion or aqueous dispersion of a natural or synthetic resin (i.e., a polymer) in particulate form in an aqueous medium. Therefore, in this application, when used with respect to a polymer, the terms "aqueous emulsion," "emulsion," and "aqueous dispersion" are used interchangeably unless otherwise stated. The "polyurethane aqueous emulsion" can be obtained using an emulsion polymerization process, or it can be prepared by other polymerization methods and then redispersed in an aqueous system. Suitable emulsion polymerization processes are known to those of ordinary skill in the art and generally comprise the following steps: dispersing a polymerizable monomer into an emulsion in water, optionally with the aid of a suitable emulsifier and / or dispersion stabilizer and with the aid of stirring, and initiating polymerization of the monomer, for example, by adding an initiator. In the present invention, the polymer particles can be modified, for example, by modifying organic functional groups (including, but not limited to, carboxyl groups, hydroxyl groups, amino groups, isocyanate groups, sulfonic acid groups, and the like) to obtain an aqueous emulsion having desired properties (e.g., dispersibility). Therefore, in the present invention, the term "aqueous emulsion" includes not only dispersions of unmodified polymer particles in an aqueous medium, but also dispersions of polymer particles modified with organic functional groups in an aqueous medium.

[0092] In one embodiment of the present invention, the aqueous coating composition used to form the transition layer comprises an aqueous polyurethane emulsion.

[0093] The transition layer is prepared using the above-mentioned water-based coating composition. When the upper electron beam-curable coating composition is cured, surface micro-crosslinking can occur to form an interface with a certain hardness gradient. In some embodiments of the present invention, the transition layer has a crosslinking degree that varies gradually from 0% to 10% from the surface in contact with the substrate to the surface in contact with the top coating. In the above-mentioned embodiment according to the present application, by making the transition layer have a crosslinking degree that varies gradually from 0% to 10% from the surface in contact with the substrate to the surface in contact with the top coating, the transition layer has a hardness that increases gradually from the surface in contact with the substrate to the surface in contact with the top coating. As a result, the physical properties of the interface between this transition layer and the electron beam-cured top coating are not much different, and it will not fail and cause interlayer separation under thermal expansion and contraction or bending stress.

[0094] The aqueous coating composition used to form the transition layer includes an aqueous polyurethane emulsion, and the molecular chains of the aqueous polyurethane emulsion include active carbamate groups (-NHCOO-) capable of forming hydrogen bonds and covalent bonds with the (bio-based modified) polyurethane resin and the bio-based acrylate monomer. In the above embodiment of the present invention, by making the molecular chains of the aqueous polyurethane emulsion included in the aqueous coating composition forming the transition layer include active carbamate groups (-NHCOO-) capable of forming hydrogen bonds and covalent bonds with the (bio-based modified) polyurethane resin and the bio-based acrylate monomer, the interlayer bonding strength between the transition layer and the upper electron beam curable coating layer is significantly improved, so that the pre-coated product obtained in this way will not fail or experience interlayer separation under thermal expansion and contraction or bending stress.

[0095] Therefore, pre-coated products according to embodiments of the present invention exhibit excellent interlayer adhesion and do not experience interlayer separation under thermal expansion and contraction or bending stress. In some embodiments according to the present invention, the peel strength between the topcoat and the transition layer is at least 3.0 N / mm, preferably between 3.5 and 4.2 N / mm, as tested in accordance with GBT 2792-2014.

[0096] In some embodiments of the present invention, the aqueous polyurethane emulsion included in the aqueous coating composition for forming the transition layer has a decomposition temperature of 200°C or higher. The inventors of the present application have found that the thermal stability of the polyurethane emulsion (decomposition temperature > 200°C) is better than that of the styrene-butadiene emulsion (decomposition temperature of approximately 160°C), thus avoiding coating defects caused by thermal degradation of the transition layer.

[0097] In some embodiments of the present invention, the aqueous polyurethane emulsion included in the aqueous coating composition used to form the transition layer has a viscosity of 100 mPa·s or less and a surface tension of 30-40 mN / m. The inventors of the present application have also discovered that the low viscosity (less than 100 mPa·s) and high surface tension (35-40 mN / m) of the aqueous polyurethane emulsion can uniformly wet the underlying substrate, particularly paper fibers, thereby significantly reducing bubbles and pinholes in the EB-cured topcoat and improving surface smoothness.

[0098] As described above, the aqueous polyurethane emulsion can be prepared using an appropriate emulsion polymerization method known to those skilled in the art. Alternatively, any suitable commercially available polyurethane emulsion can be used, such as U2101 from Oubaodi, 1301 from Fuqisen, and UH006 from Huaguoshan. The aqueous polyurethane emulsion has a solids content of 50-60%.

[0099] Preferably, the polyurethane aqueous emulsion is present in an amount of 40 to 80 wt %, preferably 50 to 70 wt %, more preferably 55 to 65 wt %, based on the total weight of the aqueous coating composition for forming the transition layer.

[0100] In an embodiment of the present invention, the aqueous coating composition used to form the transition layer may further include pigments, fillers and / or additional additives similar to those of the above-mentioned electron beam-curable bio-based coating composition.

[0101] In one embodiment according to the present invention, the aqueous coating composition comprises, relative to the total weight of the aqueous coating composition,

[0102] 40-80 wt % of the polyurethane aqueous emulsion;

[0103] 0-10 wt% of said filler, such as fumed silica;

[0104] 10-30 wt% of said deionized water; and

[0105] 0-10 wt% of the second additional additive, wherein the second additional additive is selected from a dispersant, a defoamer and a thickener.

[0106] The preparation of the water-based coating composition for forming the transition layer of the present application can be achieved by any appropriate mixing method well known to those skilled in the art. For example, the water-based coating composition can be prepared by adding a polyurethane aqueous emulsion, a filler, water, and a second additional additive (if any) to a container, and then stirring the resulting mixture to form the resulting water-based coating composition.

[0107] The present invention also provides a method for preparing the above-mentioned pre-coated product, the method comprising: providing a substrate; coating the surface of the substrate with a water-based coating composition (solid content 35-40%), with a coating amount of 10-20 g / m 2 , then infrared baking at 120-160 ° C for 2-3 minutes to obtain a dry transition layer; then, the transition layer is coated with an electron beam curable bio-based coating composition by slit coating, with a coating amount of 20-40 g / m 2 , using an electron beam with an energy of 100-300KeV and a radiation dose of 15-40KGr to cure at a speed of 100-150m / min in a conventional electron beam curing environment; optionally, various embossings are performed as needed during electron beam curing to obtain the pre-coated product.

[0108] The precoated product obtained as above has a wide range of application prospects and can be applied to the surface of decorative boards, cabinet boards or furniture panels to provide decorative or protective effects.

[0109] Products

[0110] Another aspect of the present application provides an article having a pre-coated article according to the second aspect of the present invention on its surface. As an example, the article includes a decorative board, a cabinet board, or a furniture panel.

[0111] According to certain embodiments of the present invention, the articles thus obtained can be used in the following applications, including, but not limited to: household furniture, such as tables, chairs, cabinets, etc.; bedroom furniture; office furniture; custom furniture, such as school and children's furniture, hospital furniture, restaurant and hotel furniture, kitchen cabinets and furniture; panels for interior design; indoor and outdoor windows and doors; indoor and outdoor window frames and door frames; outdoor and indoor wainscoting and wood flooring.

[0112] The following examples more particularly describe the present disclosure, which are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available and can be used directly without further treatment.

[0113] Example

[0114] Test Method

[0115] Unless otherwise stated, the following test methods were used in the following examples.

[0116] Surface scratch resistance:

[0117] The scratch resistance of the resulting coating was tested using a scratch tester, according to Section 4.42, Scratch Resistance Test Method, in accordance with GB / T 17657-2022, Test Methods for Physical and Chemical Properties of Wood-Based and Veneered Panels. Specifically, the test piece was mounted on the scratch tester's turntable and the measuring height was adjusted so that the upper edge of the crossbar was horizontal when the tip of the diamond needle contacted the specimen surface. The weight was moved to a certain load position, and the turntable was started to rotate until the diamond needle inscribed a double scratch on the specimen surface. The test piece passed the test. A force of ≥ Level 4 (4.0N) was required for the test piece to be acceptable.

[0118] hardness:

[0119] The hardness of the coating under test was measured using a Chinese pencil according to GB / T 6739. Specifically, under a 750g load, press downward at a 45° angle onto the topcoat of the composite coating, slowly moving the pencil forward while gradually increasing the pencil hardness until a scratch appears on the topcoat. The pencil hardness at this point is recorded as the coating hardness, with a higher H number indicating a higher hardness.

[0120] Peel strength

[0121] The peel strength of the resulting composite coating was tested according to the test method for peel strength of adhesive tapes specified in GBT 2792-2014. Specifically, a section of double-sided adhesive tape was adhered to a steel plate. One end of the steel plate was clamped in one fixture of a tensile testing machine, while the other fixture held the free end of the composite coating. The composite coating was then peeled away from the tape at a 180° angle. The peel force was measured by the force required to continuously peel the composite material from the tape and converted into peel strength. The peel line was perpendicular to the direction of the applied force. Each group of specimens consisted of at least three samples, and the test results were expressed as the arithmetic mean of the peel strengths in N / mm.

[0122] Adhesion

[0123] The adhesion of the resulting composite coating was tested according to the national standard GB / T 9286 cross-cut test for paints and clear coats. Specifically, a blade or cross-cut tool was used to make cuts perpendicular to the paint film, with 2mm intervals between each cut. Six cuts were made in each direction, and all cuts should be made directly onto the substrate. After the cuts were made, 3M tape was applied to the cuts and pulled upward at a 45° angle to grade the paint film. If the paint film peeled off at the intersection of the cuts by ≤5%, it was rated as Grade 1 or below, indicating acceptable adhesion. If the paint film peeled off at the intersection by >5%, it was rated as Grade 2 or above, indicating unacceptable adhesion.

[0124] raw materials

[0125] Nanocellulose 1: Nanocellulose with the brand name CNC-523 purchased from Shandong Shengquan, with a specific surface area of ​​200 m 2 / g, aspect ratio 80, length 4 μm, diameter 50 nm;

[0126] Nanocellulose 2: Nanocellulose with the brand name CNC-525 purchased from Shandong Shengquan, with a specific surface area of ​​300 m 2 / g, aspect ratio 50, length 2 μm, diameter 40 nm;

[0127] Nanocellulose 3: Nanocellulose with the brand name CNC-530 purchased from Shandong Shengquan, with a specific surface area of ​​400 m 2 / g, aspect ratio 100, length 3 μm, diameter 30 nm;

[0128] Comparative nanocellulose: Nanocellulose with the brand name CNF-C purchased from Guangxi Qihong, with a specific surface area of ​​100m 2 / g, aspect ratio is 10, length is 1 μm, diameter is 100 nm;

[0129] Comparative filler, commercially available from Grace SYLOID-161 silica, with a specific surface area of ​​200 m 2 / g, aspect ratio 5, length 5 μm, diameter 1 μm;

[0130] Bio-modified polyurethane acrylate: trifunctional bio-based resin commercially available from Sartomer, brand S7302NS, with an average molecular weight of 10,000-30,000 and a bio-based carbon content of 40-50%;

[0131] Non-biobased modified polyurethane acrylate: EBECRYL 8807 purchased from Allnex, with an average molecular weight of 20,000-35,000;

[0132] Bio-based acrylate monomer: GPTA (trifunctional glycerolated bio-based acrylate monomer) purchased from allnex;

[0133] Other monomers: 1,6-hexanediol diacrylate (HDDA) and ethoxylated trimethylolpropane triacrylate (EO-TMPTA), general industrial products;

[0134] Water-based polyurethane emulsion: U2101 water-based polyurethane emulsion purchased from Oubaodi, with a film-forming temperature of 0-5°C, a decomposition temperature greater than 200°C, a viscosity less than 100 mPa·s, and a surface tension between 35-40 mN / m.

[0135] Control water-based styrene-butadiene emulsion: a water-based styrene-butadiene emulsion with the brand SB3316 purchased from British emulsion, with a film-forming temperature of 16-22°C, a decomposition temperature of 160°C, and a viscosity of 120 mPa.s;

[0136] Pigments and fillers: general industrial products;

[0137] Other additives: general industrial products.

[0138] transition layer

[0139] The aqueous emulsions, pigments, fillers, water, and other additives in the amounts shown in Table 1 below were added to a mixing container and mixed. The mixture was then stirred at 600-800 rpm until uniform, thereby producing aqueous coating compositions. Aqueous coating composition 1 comprised an aqueous polyurethane emulsion, while aqueous coating composition 2 comprised an aqueous styrene-butadiene emulsion. The resulting aqueous coating compositions 1 and 2 were applied to test substrates, respectively, and infrared-baked at 120-160°C for 2-3 minutes to produce dried transition layers 1 and 2.

[0140] EB topcoat

[0141] The amounts of polyurethane acrylate (including bio-based modified polyurethane acrylate or non-bio-based modified polyurethane acrylate), bio-based acrylate monomer, reactive diluent, nanocellulose according to the present invention or control nanocellulose and silica, and optional additional additives shown in Table 2 below are mixed to obtain an electron beam-curable bio-based coating composition to be tested.

[0142] The above-mentioned electron beam curable bio-based coating composition to be tested is coated on the above-mentioned transition layers 1 and 2 respectively by slit coating method, and the coating amount is 20-40g / m 2 , using an electron beam with an energy of 100-300KeV and a radiation dose of 15-40KGr to cure at a speed of 100-150m / min in a conventional electron beam curing environment (for example, nitrogen-containing, oxygen content not higher than 500ppm); thereby obtaining a pre-coated product.

[0143] The surface scratch resistance, hardness, peel strength and adhesion of the obtained pre-coated product were measured as shown in the test section.

[0144] Table 1: Composition of the aqueous coating composition used to form the transition layer

[0145] Components Transition layer 1 Transition layer 2 Waterborne polyurethane emulsion U2101 60 0 Water-based styrene-butadiene emulsion SB3316 0 60 Silica TS100 6 6 Deionized water 30 30 Additional additives 4 4

[0146]

[0147]

[0148] From the results in Table 2 above, it can be seen that in the formulation of the electron beam curable bio-based coating composition, by adding nanocellulose and specifically selecting the specific surface area of ​​the nanocellulose to be at least 200 m 2 / g and an aspect ratio of at least 20 can significantly accelerate the curing reaction of electron beam-curable bio-based coating compositions and shorten the oxygen exposure time during the curing process. At the same time, the nanocellulose can also form a physical barrier in the cured coating, effectively reducing the problem of oxygen inhibition. The resulting cured coating has significantly improved surface scratch resistance, even when the coating is relatively thin.

[0149] The results in Table 2 also show that in the formulation of the electron beam-curable bio-based coating composition, by further introducing polyurethane acrylate synthesized from bio-based polyols, isocyanate and acrylate monomers as bio-based modified polyurethane acrylate, the strong base on the surface of the nanocellulose can react with the isocyanate group (-NCO) in the bio-based polyurethane acrylate to form a covalent bond, thereby enhancing the interfacial bonding force between the two phases and obtaining excellent adhesion and peel strength of the cured coating.

[0150] As can be seen from the results in Table 3 above, the pre-coated product according to the embodiment of the present invention has excellent interlayer adhesion and substantially does not experience interlayer separation under thermal expansion and contraction or bending stress.

[0151] Although the present application is described with reference to a number of implementation methods and examples, a person skilled in the art will recognize that other implementation methods can be designed based on the content disclosed in the present application, which does not deviate from the scope and spirit of the present application.

Claims

1. An electron beam curable bio-based coating composition comprising: at least one polyurethane acrylate, at least one bio-based acrylate monomer, at least one nanocellulose, and optionally a first additional additive, in, The nanocellulose has at least 200 m 2 / g specific surface area and an aspect ratio of at least 20.

2. The electron beam curable bio-based coating composition of claim 1, wherein: The at least one nanocellulose has a density of 200 to 400 m 2 / g range of specific surface area.

3. The electron beam curable bio-based coating composition of claim 1, wherein: The at least one nanocellulose has an aspect ratio of 20 to 100.

4. The electron beam curable bio-based coating composition according to any one of claims 1 to 3, wherein The at least one nanocellulose has a length in the range of 1 to 5 micrometers; and / or The at least one nanocellulose has a diameter in the range of 30-50 nm.

5. The electron beam curable bio-based coating composition according to any one of claims 1 to 3, wherein The at least one polyurethane acrylate is at least one bio-based modified polyurethane acrylate, and the at least one bio-based modified polyurethane acrylate is synthesized using bio-based polyol, isocyanate and acrylate monomers as raw materials.

6. The electron beam curable bio-based coating composition of claim 5, wherein: The bio-based polyol comprises one or more of bio-based aliphatic polyester polyol, bio-based polycaprolactone polyol (PCL), bio-based propylene oxide / ethylene oxide derivatives and bio-based specialty polyether polyol.

7. The electron beam curable bio-based coating composition of claim 5, wherein: The at least one bio-based modified polyurethane acrylate is difunctional or multifunctional; and / or The at least one bio-based modified polyurethane acrylate has a weight average molecular weight in the range of 10,000 to 30,000; and / or The at least one bio-based modified polyurethane acrylate has a bio-based carbon content in the range of 20-50%.

8. The electron beam curable bio-based coating composition according to any one of claims 1 to 3, wherein The bio-based acrylate monomer is an acrylate monomer derived from a vegetable oil selected from carona oil, castor oil, dehydrated castor oil, coconut oil, corn oil, cottonseed oil, peanut oil, linseed oil, ricinene oil, safflower oil, soybean oil, sunflower oil, tall oil, tung oil, walnut oil, wood oil, or a combination thereof.

9. The electron beam curable bio-based coating composition according to any one of claims 1 to 3, wherein The bio-based acrylate monomer is difunctional or multifunctional.

10. The electron beam curable bio-based coating composition according to any one of claims 1 to 3, further comprising a reactive diluent selected from multifunctional ethylenically unsaturated monomers, preferably selected from hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethoxylated hexanediol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate or a combination thereof.

11. The electron beam curable bio-based coating composition according to any one of claims 1 to 10, wherein The electron beam curable bio-based coating composition, after curing, forms a coating having a hardness increase of 10-20% compared to a corresponding electron beam curable bio-based coating composition without the nanocellulose.

12. A pre-coated product comprising: a substrate having at least one major surface; at least one transition layer disposed on at least a portion of a major surface of the substrate; and at least one electron beam cured topcoat layer disposed on at least a portion of the surface of the transition layer; in, The electron beam cured topcoat is formed from the electron beam curable bio-based coating composition of any one of claims 1 to 11.

13. The precoated product according to claim 12, wherein: The transition layer has a cross-linking degree that varies gradually from a surface contacting the substrate to a surface contacting the top coating layer.

14. The precoated product according to claim 12 or 13, wherein: The surface of the electronically curable topcoat layer adjacent to the transition layer has a barb structure formed by the nanocellulose and penetrating at least a portion of the transition layer.

15. The precoated product according to claim 12, wherein The transition layer is formed from an aqueous coating composition comprising an aqueous polyurethane emulsion, a filler, deionized water, and an optional second additional additive.

16. The precoated product according to claim 15, wherein The molecular chain of the polyurethane aqueous emulsion contains active carbamate groups (-NHCOO-) that can form hydrogen bonds and covalent bonds with the bio-based modified polyurethane resin and the bio-based acrylate monomer.

17. The precoated product according to claim 12, wherein: The peel strength between the top coating and the transition layer is at least 3.0 N / mm. Preferably, the peel strength between the top coating and the transition layer is 3.5-4.2 N / mm. The peel strength is tested according to the test method for peel strength of adhesive tapes in GBT 2792-2014.

18. The precoated product according to claim 15, wherein The polyurethane aqueous emulsion has a decomposition temperature of 200° C. or higher.

19. The precoated product according to claim 15, wherein The polyurethane aqueous emulsion has a viscosity of 100 mPa·s or less and a surface tension of 30-40 mN / m.

20. The precoated product according to claim 15, wherein The aqueous coating composition comprises, relative to the total weight of the aqueous coating composition, 40-80 wt % of the polyurethane aqueous emulsion; 0-10% by weight of the filler; 10-30 wt% of the deionized water and 0-10 wt% of the second additional additive.

21. The precoated product according to any one of claims 12 to 20, wherein: The substrate is selected from one or more of PP, PET, PE, PETG, PVC, PS, PMMA, and bleached kraft paper.

22. An article having the precoated article according to any one of claims 13 to 22 on its surface.

23. The article of claim 22, wherein The product includes a decorative board, a cabinet board or a furniture panel.

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