A multifunctional composite coating for OSB substrate and its preparation method

Abstract

This invention belongs to the field of materials science and surface engineering, and discloses a multifunctional composite coating for OSB sheets and its preparation method. The coating is constructed by combining an SBS-modified bitumen matrix with a multi-level micro / nano superhydrophobic filler modified with a silane coupling agent and photothermal conversion inorganic particles in a ternary composite, creating an integrated protective system with both passive superhydrophobicity and active photothermal response. The coating thickness is 50-300 μm, and the components include 65%-85% modified bitumen, 10%-25% superhydrophobic filler, 3%-12% photothermal particles, and 0.5%-3% additives. Its surface contact angle reaches 158°±2°, and the roll-off angle is <5°, exhibiting excellent waterproof, mildew-proof, freeze-thaw resistant, self-cleaning, and environmental adaptability control capabilities. During preparation, the filler and particles are sequentially dispersed in molten bitumen, and the coating is cured at low temperature after application. This invention solves the core problems of OSB in harsh environments such as high humidity, high cold, and high ultraviolet radiation, including moisture absorption and expansion, mold growth and decay, and freeze-thaw damage, providing reliable technical support for the large-scale application of green building materials in extreme climate zones.

Description

Technical Field

[0001] This invention belongs to the field of materials science and surface engineering, and relates to a multifunctional composite coating for OSB sheets and its preparation method. Background Technology

[0002] OSB (Oriented Strand Board) engineered wood composites, made by oriented strand board (OSB) of wood shavings and hot-pressing, have become an important alternative to traditional plywood and solid wood due to their high industrial production efficiency and wide availability of raw materials. However, their porous wood fiber structure, rich in hydrophilic hydroxyl groups and numerous micron-sized pores, makes them highly susceptible to moisture absorption and expansion in humid or high-humidity environments. This can lead to a series of problems, including board warping, adhesive failure, and degradation of mechanical properties. In warm and humid conditions, mold and decay fungi can easily grow on the board surface. When OSB is used in cold regions or outdoor winter settings, the expansion stress caused by ice crystals after moisture intrusion and freezing can further exacerbate structural damage, and existing protective measures often fail to meet the multiple requirements of moisture resistance, mold prevention, and freeze-thaw resistance.

[0003] Asphalt-based coatings, due to their excellent hydrophobicity, chemical inertness, and low cost, have been widely explored for waterproofing wood and engineered wood products. Traditional methods typically involve directly applying petroleum asphalt or modified asphalt to the surface of the board, forming a continuous, dense physical barrier that effectively prevents liquid water penetration. This method does significantly slow down the moisture absorption rate under dry or room temperature conditions, and the process is simple and economical.

[0004] Although asphalt coatings are hydrophobic, their surface energy is high and their static contact angle is limited, making it impossible to achieve a truly superhydrophobic state. Tiny water droplets can still slowly wet the coating and penetrate into the substrate along coating defects or interfaces. At the same time, asphalt itself lacks photothermal response capabilities and cannot actively suppress freezing or accelerate surface moisture evaporation in low-temperature environments. Once the ambient humidity remains high or a freeze-thaw cycle occurs, the coating-substrate interface may still peel off or become moldy due to the accumulation of condensate.

[0005] Some studies have attempted to introduce inorganic fillers (such as silica and zinc oxide) with micro / nano composite structures to construct superhydrophobic coatings with a lotus leaf-like effect. However, without interfacial compatibility treatment, these fillers are prone to agglomeration and sedimentation in organic bitumen matrices, resulting in poor coating uniformity and weak adhesion. Even if initial hydrophobicity is achieved, the surface microstructure is easily worn away and fails under the mechanical action of outdoor wind, sand, and rain. Simply improving hydrophobicity may still lead to the transformation from the Cassie state to the Wenzel state under conditions of supercooled water droplet impact or high humidity condensation, resulting in a loss of self-cleaning ability. Summary of the Invention

[0006] To achieve the above-mentioned objectives, this invention provides a multifunctional composite coating for OSB sheets and its preparation method. The multifunctional composite coating is constructed by combining a modified bitumen matrix with a multi-level micro-nano structured superhydrophobic filler modified with a silane coupling agent and photothermal conversion inorganic particles with high solar light absorption rate. This creates an integrated protective system that combines passive superhydrophobic barrier and active photothermal response functions. Thus, while maintaining the original mechanical properties and processing characteristics of OSB sheets, it simultaneously achieves multiple technical effects such as long-lasting waterproofing, mildew prevention, freeze-thaw resistance, self-cleaning, and environmental adaptability regulation.

[0007] The multifunctional composite coating is applied to at least one outer surface of the OSB board, with a thickness of 50-300 μm. The coating consists of the following components by mass percentage: 65%-85% modified bitumen matrix, 10%-25% multi-level micro / nano-structured superhydrophobic filler, 3%-12% photothermal conversion inorganic particles, and 0.5%-3% auxiliary additives. The components form a continuous-dispersed-phase composite structure within the coating. The modified bitumen matrix serves as the continuous phase, providing film-forming properties, adhesion, and a basic waterproof barrier. The superhydrophobic filler and photothermal conversion particles are uniformly dispersed within the bitumen matrix and partially enriched on the coating surface, collectively constructing a micron-nano composite rough structure and a photothermal response interface.

[0008] The modified asphalt matrix is ​​SBS-modified petroleum asphalt with a softening point greater than 90℃, a penetration of 20-40 (0.1mm), and a ductility (5℃) greater than 20cm. This modified asphalt is prepared by heating No. 70 road petroleum asphalt to 180℃, adding 8%-12% (by weight of asphalt) of linear SBS polymer, and then rapidly shearing and stirring at 170-190℃ for 60-90 minutes. Next, 0.3%-0.6% sulfur is added as a crosslinking accelerator, and the mixture is allowed to continue maturation for another 30 minutes. This modification process significantly improves the low-temperature toughness, high-temperature stability, and interfacial compatibility with inorganic fillers of the asphalt.

[0009] The multi-level micro / nano-structured superhydrophobic filler is composed of micron-sized silica particles and nano-sized silica particles in a mass ratio of 3:1-5:1, with an overall particle size distribution of 0.5-15 μm. The micron-sized silica particles are solid spherical or near-spherical structures with an average particle size of 5-10 μm; the nano-sized silica particles are amorphous and have an average particle size of 15-40 nm, adhering to the surface of the micron-sized particles to form a secondary rough structure. This composite filler undergoes surface hydrophobication treatment with octadecyltrichlorosilane or heptadecafluorodecyltrimethoxysilane: the filler is dispersed in anhydrous toluene, and 2%-5% of a silane coupling agent (by mass of the filler) is added. The mixture is refluxed at 80°C for 4-6 hours under nitrogen protection. After filtration, washing, and vacuum drying, a superhydrophobic powder with a contact angle greater than 150° and a roll-off angle less than 10° is obtained. The uniform dispersion of this filler in the asphalt matrix depends on the van der Waals interaction between its low surface energy organic layer and the nonpolar molecular chains of asphalt, which effectively inhibits agglomeration and enhances interfacial bonding.

[0010] The photothermal conversion inorganic particles are titanium nitride particles or aluminum-doped anatase titanium dioxide particles. When titanium nitride is used, it has a cubic crystal structure with an average particle size of 80-200 nm and an average absorption rate of more than 92% across the entire solar radiation band (300-2500 nm). When aluminum-doped anatase titanium dioxide is used, it consists of spherical nanoparticles with an average particle size of 50-120 nm and an aluminum doping concentration of 2%-5% atomic percentage, with an absorption rate of more than 85% in the visible-near-infrared band (400-1100 nm). Both types of particles are surface-modified with KH-550: the particles are dispersed in an ethanol-water mixed solvent (volume ratio 4:1), the pH is adjusted to 4.5, 1.5%-3% KH-550 by mass of the particles is added, and the mixture is stirred at 60°C for 3 hours. After centrifugation and drying, modified particles with amino groups on the surface are obtained. The amino functional group can undergo a weak chemical reaction with the carboxyl groups generated during the asphalt oxidation process, thereby improving dispersion stability and interfacial anchoring strength.

[0011] The auxiliary agents include dispersants, anti-aging agents, and leveling agents. The dispersant is polyvinylpyrrolidone or oleic acid, added at 0.2%-0.8% of the total formulation mass; the anti-aging agent is a compound of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a 1:1 mass ratio, added at 0.1%-0.4%; the leveling agent is polydimethylsiloxane, added at 0.05%-0.15%. All additives are pre-dissolved or dispersed in the hot-melt asphalt during coating preparation to ensure a homogeneous and stable system.

[0012] The preparation method of the multifunctional composite coating of the present invention includes the following steps:

[0013] Step 1: Heat the modified asphalt matrix to 160-170℃ to completely melt it while maintaining its fluidity;

[0014] Step 2: After the multi-level micro-nano structured superhydrophobic filler modified with silane coupling agent is vacuum dried at 80°C for 2 hours, it is slowly added to molten asphalt and sheared and dispersed at 165°C and 1500 rpm for 30 minutes to form the first dispersion system.

[0015] Step 3: After the photothermal conversion inorganic particles modified with KH-550 surface are vacuum dried at 60℃ for 1.5 hours, they are added to the first dispersion system and sheared and dispersed at 165℃ and 2000rpm for 45 minutes to form the second dispersion system.

[0016] Step 4: Add the auxiliary agents to the second dispersion system in sequence, and stir at low speed (300 rpm) for 15 minutes at 160°C to obtain a uniform and stable coating slurry;

[0017] Step 5: Apply the coating slurry to the surface of the OSB board by roller coating, spraying, or scraping, with the coating amount controlled at 120-300 g / m². 2 ;

[0018] Step 6: Place the coated board in an oven at 80-100℃ for 10-20 minutes to cure, allowing the coating to fully level and complete physical cross-linking, ultimately forming a dense, continuous, multifunctional composite coating with a micro-nano composite rough structure on the surface.

[0019] In a preferred embodiment of the present invention, the OSB substrate undergoes surface pretreatment before coating: first, the surface is sanded with 80-grit sandpaper to remove dust and increase roughness; then, it is wiped clean with isopropyl alcohol; and finally, it is dried at 60°C for 30 minutes to completely remove adsorbed moisture. This pretreatment ensures that a dual bonding mechanism of mechanical interlocking and physical adsorption is formed between the coating and the substrate, with an interfacial peel strength greater than 1.2 N / mm.

[0020] In another preferred embodiment of the present invention, the photothermal conversion inorganic particles are a mixture of titanium nitride and aluminum-doped anatase titanium dioxide in a mass ratio of 1:1. This combination utilizes the strong absorption characteristics of titanium nitride in the near-infrared band and the broad-spectrum response capability of aluminum-doped anatase titanium dioxide in the ultraviolet-visible band to achieve efficient capture of sunlight across the entire wavelength range, enabling the coating surface to withstand standard AM1.5G illumination (1000W / m²). 2 The temperature rise rate is greater than 8℃ / min, and the steady-state temperature is more than 25℃ higher than that of the uncoated area.

[0021] The multifunctional composite coating is applied simultaneously to both sides of the OSB board, with the coating components on both sides being the same or different. When used for outdoor walls in cold regions, the sun-facing side uses a high proportion of titanium nitride (photothermal conversion particles accounting for 10%-12%), while the shaded side uses a high proportion of superhydrophobic filler (accounting for 20%-25%) to achieve a spatial functional gradient distribution.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. Through the synergistic effect of constructing a micron-nano composite rough structure and low surface energy modification, the coating achieves a static water contact angle of 158°±2° and a roll-off angle of less than 5°, exhibiting excellent superhydrophobicity and self-cleaning ability. Liquid water cannot wet the surface, and rainwater can wash away dust and microbial spores, effectively inhibiting mold adhesion and biofilm formation;

[0024] 2. The photothermal conversion inorganic particles heat up rapidly under sunlight, making the surface temperature of the coating significantly higher than the ambient dew point temperature, which fundamentally inhibits the formation of condensate. Under icing conditions, local heating can reduce the bonding strength of the ice-solid interface, allowing the ice to fall off automatically under gravity or a light breeze, thus reducing de-icing energy consumption.

[0025] 3. The silane surface modification of superhydrophobic fillers and photothermal particles ensures their long-term stable dispersion in the asphalt matrix without sedimentation or phase separation.

[0026] 4. This coating retains the flexibility and ease of construction of asphalt materials and can be directly integrated into the end of existing OSB production lines without the need for additional complex equipment;

[0027] 5. Breaking through the traditional passive barrier and single-function technical solution of OSB protective coatings, this technology is the first to integrate a biomimetic superhydrophobic structure, a highly efficient photothermal conversion mechanism, and a modified bitumen film-forming system across scales and multiple physical fields, constructing an intelligent protective interface with environmental perception and active response capabilities. This technical solution systematically solves the core challenges of OSB in harsh environments such as high humidity, high cold, and high ultraviolet radiation, including moisture absorption and expansion, mold growth and decay, and freeze-thaw damage. Detailed Implementation

[0028] This invention provides a multifunctional composite coating for OSB (Oxygen Absorber) sheets and its preparation method, aiming to solve the technical problems of OSB sheets being prone to water absorption, swelling, and mold growth in humid environments, and lacking comprehensive protective capabilities in low-temperature or outdoor environments. This invention constructs a ternary composite functional system consisting of a modified bitumen matrix, a multi-level micro / nano-structured superhydrophobic filler modified with a silane coupling agent, highly efficient photothermal conversion inorganic particles, and auxiliary additives. This system forms an integrated intelligent coating on the surface of OSB sheets, possessing both passive superhydrophobic barrier and active photothermal response capabilities, thereby achieving multiple technical effects such as long-lasting waterproofing, mold prevention, freeze-thaw resistance, self-cleaning, and environmental adaptability regulation.

[0029] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0030] Example 1: Modified asphalt 75%; superhydrophobic filler 18% (micron-sized silicon: nano-sized silicon = 4:1); photothermal particles 6% (titanium nitride: aluminum-doped titanium dioxide = 1:1); additives 1% (dispersant (polyvinylpyrrolidone): 0.6%; anti-aging agent (antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:1): 0.3%; leveling agent (polydimethylsiloxane): 0.1%); coating thickness 180 μm; coating weight 200 g / m² 2 Curing temperature: 90℃;

[0031] Preparation process: Modified asphalt melting → superhydrophobic filler dispersion → photothermal particle dispersion → additive addition → slurry preparation → coating → curing → finished product.

[0032] Example 2: 10% superhydrophobic filler, the rest of the formulation and process are the same as in Example 1;

[0033] Preparation process: Same as in Example 1.

[0034] Example 3: 25% superhydrophobic filler, the rest of the formulation and process are the same as in Example 1;

[0035] Preparation process: Same as in Example 1.

[0036] Example 4: 3% photothermal particles, the rest of the formulation and process are the same as in Example 1;

[0037] Preparation process: Same as in Example 1.

[0038] Example 5: 12% photothermal particles, the rest of the formulation and process are the same as in Example 1;

[0039] Preparation process: Same as in Example 1.

[0040] Example 6: Sunlit side: 11% photothermal particles, 14% superhydrophobic filler; Shaded side: 3% photothermal particles, 22% superhydrophobic filler; Other formulations and processes are the same as in Example 1;

[0041] Preparation process: Same as in Example 1 (different slurries are applied to different surfaces).

[0042] Example 7: The photothermal particles were dispersed at a speed of 2200 rpm, and the rest of the formulation and process were the same as in Example 1;

[0043] Preparation process: Same as in Example 1 (adjusting the dispersion speed).

[0044] Example 8: Coating thickness 300μm, coating amount 300g / m 2 The remaining formulas and processes are the same as in Example 1;

[0045] Preparation process: Same as in Example 1 (adjust coating amount).

[0046] Comparative Example 1: No superhydrophobic filler or photothermal particles; only 99% modified asphalt + 1% additives; the rest of the formulation and process are the same as in Example 1;

[0047] Preparation process: Asphalt melting → Additives addition → Coating → Curing → Finished product.

[0048] Comparative Example 2: No heat-sensitive particles; 70% modified asphalt + 29% superhydrophobic filler + 1% additives; the rest of the formulation and process are the same as in Example 1;

[0049] Preparation process: Same as in Example 1 (without the thermo-optical particle dispersion step).

[0050] Test method:

[0051] Superhydrophobicity and photothermal testing: Static contact angle and roll-off angle were measured using a contact angle meter; temperature rise rate and steady-state temperature difference were measured under standard AM1.5G illumination.

[0052] Durability protection test: 20 freeze-thaw cycles at -20℃ / 25℃, observe coating integrity; peel test to determine interfacial bonding strength; mold culture test to evaluate inhibition rate.

[0053] Stability test: QUV accelerated aging for 500 hours, contact angle retention rate and color difference were tested; the coating was observed for cracking and blistering.

[0054] The test data comparisons are shown in Table 1 and Table 2.

[0055] Table 1 Comparison of Static Contact Angle, Roll-Off Angle, Temperature Rise Rate, and Steady-State Temperature Difference

[0056]

[0057] Table 2 Comparison of state, interfacial peel strength, and mold inhibition rate after 20 freeze-thaw cycles

[0058]

[0059] Examples 1-8 showed a contact angle ≥152° and no cracking during freeze-thaw cycles, which was far superior to the comparative examples. Comparative example 1 showed that traditional asphalt lacked superhydrophobic and photothermal properties and had extremely poor protective properties. Comparative example 2 showed that it lacked heat- and light-emitting particles and had insufficient freeze-thaw resistance, thus proving that the core system is the key to multifunctional synergy.

[0060] The proportion of superhydrophobic fillers is increased (Examples 2→1→3), resulting in increased contact angle and improved mold inhibition rate; the proportion of photothermal particles is increased (Examples 4→1→5), significantly optimizing the temperature rise rate and steady-state temperature difference; the functional gradient design (Example 6) balances heat absorption in sunlight and hydrophobicity in shade, adapting to extreme environments.

[0061] The embodiment features multiple functions including superhydrophobicity, photothermal anti-icing, mildew prevention, and freeze-thaw resistance, making it suitable for outdoor and high-altitude, cold, and high-humidity environments; the process is compatible with existing OSB production lines, and the cost increase is controllable; the interface bonding is robust, resulting in a long service life.

[0062] Compared to traditional asphalt coatings (Comparative Example 1), the contact angle of the example is increased by 66%, and the mold inhibition rate is increased by 217%; compared to superhydrophobic systems only (Comparative Example 2), the freeze-thaw resistance is increased by 100%, solving the industry problem of traditional coatings having single function and poor tolerance to extreme environments.

[0063] The composite coating described in this invention achieves multifunctional protection through ternary synergy and structural optimization, with different parameter combinations, and is suitable for harsh scenarios such as outdoor and building structures of OSB panels.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multifunctional composite coating for OSB boards, characterized in that, The multifunctional composite coating is applied to at least one outer surface of the OSB substrate, with a thickness of 50-300 μm, and is composed of the following components by mass percentage: Modified asphalt matrix 65%-85%; Multi-level micro / nano structured superhydrophobic fillers: 10%-25%; Photothermal conversion inorganic particles 3%-12%; And auxiliary agents 0.5%-3%; The multi-level micro-nano structured superhydrophobic filler is composed of micron-sized silica particles and nano-sized silica particles in a mass ratio of 3:1 to 5:1, and is surface-modified with octadecyltrichlorosilane or heptadecafluorodecyltrimethoxysilane.

2. The multifunctional composite coating for OSB substrates according to claim 1, characterized in that, The modified asphalt matrix is ​​SBS modified petroleum asphalt with a softening point greater than 90℃, a penetration of 20-40, and a ductility greater than 20cm.

3. The multifunctional composite coating for OSB substrates according to claim 1, characterized in that, The photothermal conversion inorganic particles are a mixture of titanium nitride particles and aluminum-doped anatase titanium dioxide particles, and are surface-modified with KH-550.

4. The multifunctional composite coating for OSB substrates according to claim 1, characterized in that, The components form a continuous-dispersed phase composite structure in the coating. The modified asphalt matrix serves as the continuous phase, while the superhydrophobic filler and photothermal conversion inorganic particles are uniformly dispersed and partially enriched on the coating surface, jointly constructing a micro-nano composite rough structure and a photothermal response interface.

5. The multifunctional composite coating for OSB substrates according to claim 1, characterized in that, The micron-sized silica particles are solid spherical or near-spherical structures; the nano-sized silica particles are amorphous and form a secondary rough structure on the surface of the micron-sized silica particles.

6. The multifunctional composite coating for OSB substrates according to claim 1, characterized in that, The multi-level micro-nano structured superhydrophobic filler undergoes surface hydrophobication treatment, and the organic layer grafted onto its surface is compatible with the modified asphalt matrix through van der Waals forces, inhibiting agglomeration and enhancing interfacial bonding.

7. The multifunctional composite coating for OSB substrates according to claim 3, characterized in that, The titanium nitride particles have a cubic crystal structure and an average absorption rate of more than 92% across the entire solar spectrum; or the aluminum-doped anatase titanium dioxide particles are spherical nanoparticles with an aluminum doping concentration of 2%-5% atomically and an absorption rate of more than 85% in the visible-near-infrared band.

8. The multifunctional composite coating for OSB substrates according to claim 1, characterized in that, The auxiliary agents include: 0.2%-0.8% dispersant, 0.1%-0.4% anti-aging agent, and 0.05%-0.15% leveling agent; wherein the dispersant is polyvinylpyrrolidone or oleic acid, the anti-aging agent is antioxidant 1010 and antioxidant 168 compounded in a mass ratio of 1:1, and the leveling agent is polydimethylsiloxane.

9. A method for preparing a multifunctional composite coating as described in any one of claims 1-8, characterized in that, Includes the following steps: S10: Melt the modified asphalt matrix by heating it to 160-170℃; S20: The dried multi-level micro-nano structured superhydrophobic filler is added to the molten asphalt and sheared and dispersed to obtain the first dispersion system; S30: Add the dried photothermal conversion inorganic particles to the first dispersion system and shear them to obtain the second dispersion system; S40: Add the auxiliary additives to the second dispersion system and stir evenly to obtain the coating slurry; S50: Apply the slurry to the surface of OSB boards by roller coating, spraying, or scraping, with a coating amount of 120-300 g / m². 2 ; S60: Curing forms the final coating.

Images