Wood coating suitable for complex base material and preparation method thereof

Abstract

The invention relates to a woodware coating suitable for a complex base material and a preparation method of the woodware coating. The wood coating is prepared from the following raw materials: light-cured resin, nano silicon dioxide, a first photoinitiator, a second photoinitiator and a leveling aid, and the wavelength of at least one absorption peak of the second photoinitiator is smaller than that of any one absorption peak of the first photoinitiator. The molecular weight of the first photoinitiator is greater than that of the second photoinitiator. According to the scheme, a coating suitable for high-density hardwood is provided through a dual-photoinitiator system with specific wavelength and molecular weight combination.

Description

Technical Field

[0001] The present invention relates to the field of coatings, in particular to a wood coating suitable for complex substrates and a preparation method thereof. Background Art

[0002] UV-curable wood coatings are increasingly used in solid wood furniture. They primarily use ultraviolet light to trigger rapid resin crosslinking, making them more environmentally friendly and efficient than traditional solvent-based coatings. While current mainstream formulations have demonstrated excellent results in conventional solid wood furniture, they still present challenges when working with high-hardness hardwoods like oak and walnut. The small and complex pores of these woods make it difficult for coatings to fully cure once they penetrate the pores, resulting in poor adhesion between the coating and the wood and easy flaking during use.

[0003] CN114395306A discloses a water-based UV light-curing wood coating, a light-curing method, and its application, belonging to the field of light-curing technology. The water-based UV light-curing wood coating comprises the following raw materials: polyurethane polyurethane acrylic resin, epoxy polyurethane acrylic resin, a difunctional active monomer, a photoinitiator, a matte powder, a leveling agent, a defoamer, a dispersant, and a feel agent. It uses low-band UVC light, combined with the coating, to achieve excellent surface curing effects. Energy consumption during the curing process is reduced by 80% compared to existing processes, while maintaining a temperature around room temperature. This addresses the high energy consumption, high temperature, and unsatisfactory surface curing effects of currently common UV curing technologies on the market. However, it does not address the deep curing of complex substrates, such as those with hardness. CN109337525A discloses a UV wood coating for high-density wood and its manufacturing method. It addresses the technical problem of poor adhesion to the paint surface due to the small gaps in the wood resulting from high density, making it difficult for the paint to penetrate the surface. However, the complex formulation and preparation process make it difficult to commercialize.

[0004] Therefore, it is necessary to propose a wood coating suitable for complex substrates and a preparation method thereof. Summary of the Invention

[0005] Based on this, a wood coating suitable for complex substrates and a preparation method thereof are provided.

[0006] A wood coating suitable for complex substrates, characterized in that the preparation raw materials include a photocurable resin, nano-silica, a first photoinitiator, a second photoinitiator and a leveling agent, the second photoinitiator has at least one absorption peak with a wavelength shorter than the wavelength of any absorption peak of the first photoinitiator, and the molecular weight of the first photoinitiator is greater than the molecular weight of the second photoinitiator.

[0007] This solution provides a coating suitable for high-density hardwoods using a dual-photoinitiator system with a specific wavelength and molecular weight combination. When the coating is applied to the wood surface, the second photoinitiator exhibits at least one absorption peak with a wavelength shorter than any of the first photoinitiator's absorption peaks. When the coating is irradiated with a light source, the short wavelength of the light source triggers the second photoinitiator on the coating surface, causing rapid crosslinking and curing (low-molecular-weight photoinitiators readily migrate to the surface, further enhancing surface curing efficiency), thereby achieving rapid surface drying. The long wavelength of the light source penetrates deeper into the coating, initiating curing of the first photoinitiator. The high-molecular-weight first photoinitiator migrates more slowly, allowing it to maintain a higher concentration deep within the coating. However, the long wavelength has a lower intensity deep within the coating, significantly reducing curing efficiency compared to the surface. Consequently, the coating maintains high fluidity in these deeper layers, allowing the photocurable resin to fully penetrate the wood's micropores, improving adhesion after curing. Nanosilica enhances resin migration into the wood's micropores through capillary action, forming a mechanically interlocking structure that further enhances coating adhesion. Therefore, this coating achieves both a short dry time and strong adhesion. Through an innovative dual-photoinitiator synergistic mechanism and nano-enhancement technology, it effectively addresses the problem of coating delamination caused by insufficient curing in deep pore areas. This technology can be applied to applications requiring stringent surface coating performance, such as solid wood furniture, musical instruments, and high-end decorative materials, in line with the current trend of environmentally friendly coatings characterized by low VOC, high efficiency, and excellent durability.

[0008] Furthermore, the first photoinitiator exhibits at least one absorption peak with a wavelength ≥ 365 nm. This allows activation using light with longer wavelengths, which penetrate deeper and activate coatings deep into pores. Furthermore, the absorption peak wavelengths may be 368, 375, 380, 385, 390, 395, 400, 405, or 410 nm, with one, two, or three absorption peaks being acceptable.

[0009] Furthermore, the ratio of the molecular weight of the first photoinitiator to the molecular weight of the second photoinitiator is (1.5-5):1. Specific ratios may include 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1. Using a second photoinitiator with a lower molecular weight allows for rapid crosslinking and curing to form a support network on the surface, preventing sagging.

[0010] Furthermore, the mass ratio of the first photoinitiator to the second photoinitiator is (1-2): 1. This ratio can take into account both penetration and curing efficiency.

[0011] Furthermore, the first photoinitiator is TPO. TPO (dibenzoylphosphine oxide) has an absorption peak at 380-420 nm and a molecular weight of 410 Da. Its cleavage-type initiation mechanism can generate highly active free radicals, improving deep-layer curing efficiency.

[0012] Furthermore, the second photoinitiator is 1173. The absorption peak of 1173 (2-hydroxy-2-methylpropiophenone) is located at 240-280nm, and the molecular weight is 164Da. It can quickly decompose on the coating surface to generate free radicals, thereby achieving rapid curing of the surface.

[0013] Furthermore, the light-curable resin is polyurethane acrylic resin, which has low viscosity (facilitating penetration) and high reactivity, and its carbon-carbon double bonds are rapidly cross-linked under the initiation of free radicals to form a dense network structure.

[0014] Furthermore, based on weight fraction, it comprises 40-70 parts of the photocurable resin, 1-5 parts of the first photoinitiator, 0.5-3 parts of the second photoinitiator, 2-5 parts of the nano-silica, and 0.1-0.5 parts of the leveling agent. Specifically, it comprises 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 68 parts or 70 parts of the photocurable resin; 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts or 5 parts of the first photoinitiator; 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.2 parts, 2.5 parts, 2.8 parts or 3 parts of the second photoinitiator; 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.3 parts, 4.7 parts or 5 parts of the nano-silica; 0.1 part, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts or 0.5 parts of the leveling agent.

[0015] Furthermore, the complex substrate comprises a density ≥ 0.75 g / cm 3 The pores of these woods (such as oak and walnut) are very small (1-10 μm) and tortuous, making it difficult for ordinary UV coatings to penetrate.

[0016] Furthermore, after the coating is applied to the wood surface to form a coating, the coating is irradiated using a medium-pressure mercury lamp, which has several strong peaks between 250-400 nm.

[0017] The second aspect of the present application provides a method for preparing the above-mentioned wood coating, comprising the following steps: mixing the photocurable resin with the first photoinitiator and the second photoinitiator under light-proof conditions, then adding the nano-silica and dispersing it, adding the leveling agent and adjusting the viscosity to 500-1500 mPa·s.

[0018] The wood coating prepared by the above preparation method can be applied to complex substrates. DETAILED DESCRIPTION

[0019] For ease of understanding of the present application, the present application will be described more fully below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0020] The present embodiment provides a wood coating suitable for complex substrates. The raw materials for preparation include a light-curable resin, nano-silica, a first photoinitiator, a second photoinitiator, and a leveling agent. The second photoinitiator has at least one absorption peak with a wavelength shorter than any absorption peak of the first photoinitiator, and the molecular weight of the first photoinitiator is greater than that of the second photoinitiator. For example, the first initiator, TPO, has an absorption peak at 380-420 nm and a molecular weight of 410 Da, while the second initiator, 1173, has an absorption peak at 240-280 nm and a molecular weight of 164 Da. The following materials are all commercially available.

[0021] Example 1: This example provides a method for preparing a wood coating suitable for complex substrates.

[0022] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 55 parts of polyurethane acrylic resin, 2 parts of first photoinitiator TPO, 1.5 parts of second photoinitiator 1173, 3 parts of nano-silica (average particle size 10 nm), and 0.3 parts of leveling aid polyether modified siloxane (BYK-333).

[0023] Preparation method: In a light-proof reactor, 55 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate are added, followed by 2 parts of TPO and 1.5 parts of 1173, and stirring at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed. Then, 3 parts of nano-silica are added and stirred at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed. 0.3 parts of a leveling agent is added and stirred evenly. Then, a diluent acrylic monomer is added to adjust the viscosity of the coating to 900 mPa·s. After filtering through a 200-mesh filter, the coating is placed in a light-proof container to obtain a wood coating.

[0024] Example 2: This example provides a method for preparing a wood coating suitable for complex substrates.

[0025] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 70 parts of polyurethane acrylic resin, 3 parts of first photoinitiator TPO, 1.5 parts of second photoinitiator 1173, 3 parts of nano-silica (average particle size 10 nm), and 0.3 parts of leveling aid polyether modified siloxane (BYK-333).

[0026] Preparation method: In a light-proof reactor, add 70 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate, then add 3 parts of TPO and 1.5 parts of 1173 in sequence, and stir at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed. Then, add 3 parts of nano-silica, stir and disperse at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed, add 0.3 parts of leveling agent and stir evenly, then add diluent acrylic monomer to adjust the viscosity of the coating to 900 mPa·s, filter through a 200-mesh filter, and place in a light-proof container to obtain the wood coating.

[0027] Example 3: This example provides a method for preparing a wood coating suitable for complex substrates.

[0028] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 40 parts of polyurethane acrylic resin, 1.5 parts of first photoinitiator TPO, 1.5 parts of second photoinitiator 1173, 2 parts of nano-silica (average particle size 10 nm), and 0.1 parts of leveling aid polyether modified siloxane (BYK-333).

[0029] Preparation method: In a light-proof reactor, add 40 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate, then add 1.5 parts of TPO and 1.5 parts of 1173 in sequence, and stir at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed. Then, add 2 parts of nano-silica, stir and disperse at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed, add 0.1 parts of leveling agent and stir evenly, then add diluent acrylic monomer to adjust the viscosity of the coating to 900 mPa·s, filter through a 200-mesh filter, and place in a light-proof container to obtain the wood coating.

[0030] Example 4: This example provides a method for preparing a wood coating suitable for complex substrates.

[0031] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 55 parts of polyurethane acrylic resin, 2 parts of first photoinitiator TPO, 0.75 parts of second photoinitiator 1173, 3 parts of nano-silica (average particle size 10 nm), and 0.3 parts of leveling aid polyether modified siloxane (BYK-333).

[0032] Preparation method: In a light-proof reactor, 55 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate are added, followed by 2 parts of TPO and 0.75 parts of 1173, and stirring at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed. Then, 3 parts of nano-silica are added and stirred at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed. 0.3 parts of a leveling agent is added and stirred evenly. Then, a diluent acrylic monomer is added to adjust the viscosity of the coating to 1500 mPa·s. The coating is filtered through a 200-mesh filter and placed in a light-proof container to obtain a wood coating.

[0033] Example 5: This example provides a method for preparing a wood coating suitable for complex substrates.

[0034] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 55 parts of polyurethane acrylic resin, 2 parts of first photoinitiator TPO, 1.5 parts of second photoinitiator 1173, 3 parts of nano-silica (average particle size 10 nm), and 0.3 parts of leveling aid polyether modified siloxane (BYK-333).

[0035] Preparation method: In a light-proof reactor, 55 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate are added, followed by 2 parts of TPO and 1.5 parts of 1173, and stirring at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed. Then, 3 parts of nano-silica are added and stirred at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed. 0.3 parts of a leveling agent is added and stirred evenly. Then, a diluent acrylic monomer is added to adjust the viscosity of the coating to 500 mPa·s. After filtering through a 200-mesh filter, the coating is placed in a light-proof container to obtain a wood coating.

[0036] Comparative Example 1: This embodiment provides a method for preparing a coating.

[0037] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 55 parts of polyurethane acrylic resin, 3.5 parts of first photoinitiator TPO, 3 parts of nano-silica (average particle size 10 nm), and 0.3 parts of leveling aid polyether modified siloxane (BYK-333).

[0038] Preparation method: In a light-proof reactor, add 55 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate, add 3.5 parts of TPO, and stir at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed, then add 3 parts of nano-silica, stir and disperse at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed, add 0.3 parts of leveling agent and stir evenly, then add diluent acrylic monomer to adjust the viscosity of the coating to 900 mPa·s, filter through a 200-mesh filter, and place in a light-proof container to obtain the wood coating.

[0039] Comparative Example 2: This comparative example provides a method for preparing a coating.

[0040] Preparation raw materials: 40 parts of diluent trimethylolpropane triacrylate, 55 parts of polyurethane acrylic resin, 3.5 parts of second photoinitiator 1173, 3 parts of nano-silica (average particle size 10 nm), and 0.3 parts of leveling aid polyether modified siloxane (BYK-333).

[0041] Preparation method: In a light-proof reactor, add 55 parts of polyurethane acrylic resin and 40 parts of diluent trimethylolpropane triacrylate, add 3.5 parts of 1173, stir at 500 rpm for 20 minutes to ensure that the photoinitiator is completely dissolved and dispersed, then add 3 parts of nano-silica, stir and disperse at 2000 rpm for 30 minutes to ensure that the nano-silica is evenly dispersed, add 0.3 parts of leveling agent and stir evenly, then add diluent acrylic monomer to adjust the viscosity of the coating to 900 mPa·s, filter through a 200-mesh filter, and place in a light-proof container to obtain the wood coating.

[0042] The adhesion of the above coatings was tested according to the method of GB / T9286-98, in which the test board was made of oak with a thickness of 10 mm (density of 0.80 g / cm 3 The surface drying time of the above-mentioned coatings was tested according to the test method of GB / T 1728-2020. The test results are as follows. The coatings were irradiated using a medium-pressure mercury lamp with a power density of 100mW / cm2.

[0043] Table 1 Adhesion and surface drying time test results of Examples and Comparative Examples.

[0044] project Adhesion (level) Surface drying time (seconds) Example 1 0 8 Example 2 0 9 Example 3 0 7 Example 4 1 8 Example 5 0 7.5 Comparative Example 1 2 14 Comparative Example 2 3 6 According to the data in Table 1, the data of Examples 1-5 are all better than those of Comparative Examples 1-2. This is because the present solution provides a coating suitable for high-density hardwood by using a dual photoinitiator system with a specific wavelength and molecular weight combination. When the coating is applied to a wood surface, the second photoinitiator exhibits at least one absorption peak with a wavelength shorter than any of the first photoinitiator's absorption peaks. When the coating is irradiated with a light source, the short wavelength of the light source triggers the second photoinitiator on the coating surface, causing rapid crosslinking and curing (low-molecular-weight photoinitiators readily migrate to the surface, further enhancing surface curing efficiency), thereby achieving rapid surface drying. The long wavelength of the light source penetrates deeper into the coating, triggering the curing of the first photoinitiator. The high-molecular-weight first photoinitiator migrates more slowly, allowing it to maintain a higher concentration in the deeper layers of the coating. However, the intensity of the long wavelength in these layers is lower, significantly reducing the curing efficiency in these layers compared to the surface. Consequently, the coating in these layers maintains high fluidity for a longer period of time, allowing the photocurable resin to fully penetrate the wood's micropores, improving the adhesion of the cured coating. Nanosilica enhances the migration of the resin into the wood's micropores through capillary action, forming a mechanically interlocking structure that further enhances the coating's adhesion. Therefore, the coating of this solution combines a short surface drying time with strong adhesion. Comparative Example 1 only contains TPO photoinitiator, which has a slow reaction rate and cannot achieve rapid surface drying. The coating is not fully cured due to the influence of oxygen inhibition, resulting in reduced material adhesion; Comparative Example 2 only contains 1173 photoinitiator. After the surface layer is quickly cured, it is difficult for short-wave light to enter the deep layer of the coating to activate the 1173 photoinitiator to complete the curing of the deep layer of the coating, so its adhesion is poor.

[0045] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A wood coating suitable for complex substrates, characterized in that: The preparation raw materials include photocurable resin, nano-silica, a first photoinitiator, a second photoinitiator and a leveling agent, the second photoinitiator has at least one absorption peak with a wavelength smaller than the wavelength of any absorption peak of the first photoinitiator, and the molecular weight of the first photoinitiator is greater than the molecular weight of the second photoinitiator.

2. The wood coating according to claim 1, characterized in that The first photoinitiator has at least one absorption peak with a wavelength of ≥365 nm.

3. The wood coating according to claim 1, wherein The ratio of the molecular weight of the first photoinitiator to the molecular weight of the second photoinitiator is (1.5-5):

1.

4. The wood coating according to claim 1, characterized in that The mass ratio of the first photoinitiator to the second photoinitiator is (1-2):

1.

5. The wood coating according to claim 1, wherein The first photoinitiator is TPO.

6. The wood coating according to claim 1, characterized in that The second photoinitiator is 1173.

7. The wood coating according to claim 1, characterized in that The light-curable resin is polyurethane acrylic resin.

8. The wood coating according to claim 1, wherein Calculated by weight, the composition comprises 40-70 parts of the photocurable resin, 1-5 parts of the first photoinitiator, 0.5-3 parts of the second photoinitiator, 2-5 parts of the nano-silica, and 0.1-0.5 parts of the leveling agent.

9. The wood coating according to claim 1, wherein The complex substrate comprises a density ≥ 0.75 g / cm 3 of hardwood.

10. The method for preparing a wood coating according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: mixing the photocurable resin, the first photoinitiator and the second photoinitiator under light-proof conditions, then adding the nano-silica and performing dispersion treatment, adding the leveling agent and adjusting the viscosity to 500-1500 mPa·s.