Nano-ceramic-coated straw board with super-weather-resistant self-cleaning function and preparation method of nano-ceramic-coated straw board

Abstract

The invention discloses a nano-ceramic-coated straw board with a super-weather-resistant self-cleaning function and a preparation method, and belongs to the technical field of environment-friendly building boards. The straw board sequentially comprises a nano ceramic covering film, an inorganic seal primer and a straw board base material from top to bottom, the nano ceramic coating film is composed of silicon dioxide particles, zinc oxide particles, titanium dioxide particles and an organic toughening agent, the inorganic seal primer is composed of potassium silicate, lithium silicate, silicon dioxide particles, ethyl silicate hydrolysate and an organic toughening agent, and the straw board base material is prepared through a polyurethane cross-linking reaction technology. According to the invention, the problem of compatibility between the hard ceramic coating and the soft straw base material is solved through the inorganic seal primer, and the super weather resistance of the nano ceramic coating and the environmental protection advantage of the polyurethane crosslinking process are combined, so that the product realizes zero carbon emission, the adhesive force is more than or equal to 1.5 MPa, the pencil hardness is more than or equal to 3H, and the color difference delta E is less than or equal to 1.0 after the xenon lamp is aged for 1000 hours, which is obviously superior to the prior art; the method can be widely applied to the fields of building decoration and outdoor landscapes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmentally friendly building decoration materials, and particularly relates to a nano-ceramic coated straw board with super weather-resistant self-cleaning function and a preparation method. BACKGROUND

[0002] With the improvement of people's environmental awareness, board materials taking agricultural waste (such as straw) as raw materials have attracted attention due to the advantage of resource recycling utilization. However, the existing straw board has two core problems: first, the surface coating has poor compatibility. Although the conventional nano-ceramic coating has high hardness and weather resistance, the film brittleness is large, and the hardness difference and the expansion coefficient difference between the straw substrate (soft and high expansion coefficient) are significant, resulting in easy cracking and peeling of the coating, and insufficient adhesion; second, it is difficult to balance environmental protection and strength. Most straw boards rely on a large amount of urea-formaldehyde resin, phenol-formaldehyde resin and other glue bonding, which not only exceeds the standard (such as traditional straw board TVOC is usually > 300 μg / m 3 , formaldehyde > 0.1 mg / m 3 ), but also has low substrate strength (static bending strength < 12 MPa), which cannot meet the construction requirements of hard coating; third, the weather resistance and stain resistance are insufficient. The conventional coating (such as acrylic coating) is prone to color difference (ΔE > 3.0), peeling and dirt accumulation after 1000h outdoor use, and has a short service life (< 3 years).

[0003] In the prior art, some schemes attempt to improve the toughness of the ceramic coating by adding an organic toughening agent, but the interface matching problem of "hard coating-soft substrate" is not solved; some schemes use inorganic primer, but the primer formula is not optimized for the characteristics of the straw substrate, and the adhesion is limitedly improved (< 1.0 MPa); at the same time, the amount of glue used in the traditional straw board is large (> 10 parts by weight), which cannot realize true low-carbon environmental protection. Therefore, it is urgent to develop a nano-ceramic coated straw board which balances "super weather resistance, high adhesion, strong environmental protection and high strength" and a preparation method thereof. SUMMARY

[0004] The purpose of the present application is to provide a nano-ceramic coated straw board with super weather-resistant self-cleaning function and a preparation method, to solve the problem of poor compatibility of the existing nano-ceramic coating and the straw substrate: large hardness difference, and mismatched expansion coefficient, resulting in easy cracking and peeling of the coating.

[0005] The technical solution of the present application to solve the above technical problems is as follows: The nano-ceramic coated straw board with super weather-resistant self-cleaning function comprises, from top to bottom, a nano-ceramic coating film, an inorganic sealing primer and a straw board substrate. The thickness of the nano-ceramic film is 5-15 μm, and it is composed of the following components by weight: 40-60 parts of silica particles, 15-25 parts of zinc oxide particles, 10-20 parts of titanium dioxide particles, and 1-5 parts of an organic toughening agent; The thickness of the inorganic closed primer is 8-20 μm, and it is composed of the following components by weight: 25-40 parts of potassium silicate, 10-20 parts of lithium silicate, 20-35 parts of silica particles, 8-15 parts of ethyl silicate hydrolysate, and 1-4 parts of an organic toughening agent; The thickness of the straw board substrate is 5-30 mm, and it is composed of the following components by weight: 95-99 parts of straw and 1-5 parts of glue.

[0006] Further scheme: the straw board substrate is prepared by a polyurethane cross-linking reaction process, and the static bending strength of the straw board substrate is ≥15 MPa and the elastic modulus is ≥2500 MPa, reaching the bearing grade strength, so that the straw board substrate reaches the bearing grade strength, avoiding the problems of cracking and deformation during the subsequent hard coating process such as inorganic closed primer coating and nano-ceramic film coating, while providing stable support for the overall board, ensuring that the subsequent coating functions normally.

[0007] Further scheme: the VOC content and the formaldehyde content of the paint used for coating the nano-ceramic film and the inorganic closed primer are not detected, greatly improving the environmental performance of the board, avoiding the release of harmful substances such as VOC and formaldehyde during the use of the paint to pollute the environment or harm human health, meeting the low-carbon environmental protection policy and the use demand of environmentally friendly boards indoors and outdoors.

[0008] Further scheme: the TVOC content of the straw board substrate is 67 μg / m 3 , further strengthening the overall environmental performance of the board, which is much lower than the TVOC limit requirement in the relevant indoor air quality standard, and can be safely applied to indoor decoration scenes, reducing pollution to indoor air and ensuring the health of the living or using environment.

[0009] Further scheme: the inorganic closed primer is used to alleviate the hardness difference and the expansion coefficient difference between the nano-ceramic film and the straw board substrate, so that the adhesion between the nano-ceramic film and the straw board substrate is ≥1.5 MPa, effectively alleviating the hardness difference and the expansion coefficient difference between the nano-ceramic film (high hardness) and the straw board substrate (relatively soft), avoiding the problems of cracking and falling off of the film due to insufficient adhesion during use, and ensuring the long-term stability of the functions such as super weather resistance, self-cleaning, and scratch resistance of the board.

[0010] A preparation method of a nano-ceramic coated straw board with super weather resistance and self-cleaning function, comprising the following steps: Step 1: Prepare the straw board substrate, take 95-99 parts of straw and 1-5 parts of glue by weight, add 0.5-2 parts of polyurethane crosslinking agent, use polyurethane crosslinking reaction process to hot press at 120-150℃, 0.8-1.2MPa for 20-40min, process to get the load level strength straw board substrate with thickness of 5-30mm, static bending strength ≥15MPa, elastic modulus ≥2500MPa; Step 2: Roll coating (coating speed 1-3m / min) inorganic sealing primer on the surface of the straw board substrate prepared in step 1, the inorganic sealing primer is composed of potassium silicate 25-40 parts, lithium silicate 10-20 parts, silica particles 20-35 parts, silicon ethylate hydrolysate 8-15 parts and organic toughening agent 1-4 parts by weight, control the primer thickness to be 8-20μm after coating, and cure at 80-100℃ for 20-40min; Step 3: Spray (spraying pressure 0.3-0.5MPa) nano ceramic film on the surface of the inorganic sealing primer cured in step 2, the nano ceramic film is composed of silica particles 40-60 parts, zinc oxide particles 15-25 parts, titanium dioxide particles 10-20 parts and organic toughening agent 1-5 parts by weight, control the film thickness to be 5-15μm after coating, and cure at 110-130℃ for 30-60min to get the nano ceramic coated straw board with super weather resistance and self-cleaning function.

[0011] Further scheme: The glue in step 1 is an environmentally friendly water-based glue, which reduces the introduction of harmful substances from the source of substrate preparation, avoids the release of pollutants such as formaldehyde and TVOC from traditional non-environmentally friendly glue, and further protects the environmental performance of the straw board substrate. Collaborate with polyurethane crosslinking reaction process to achieve ultra-low carbon emission or even 0 carbon emission; The organic toughening agent in step 2 is an epoxy modified polysiloxane, which improves the toughness of the inorganic sealing primer, prevents the primer from cracking due to brittleness during subsequent processing or use, and enhances the compatibility of the primer with the straw board substrate and the nano ceramic film, which helps to improve the adhesion and stability of the overall coating system. The organic toughening agent in step 3 is an acrylate toughening agent, which improves the brittleness of the film, reduces the risk of cracking under stress or environmental temperature changes, and prolongs the service life of the film while ensuring the core functions of high hardness and super weather resistance of the nano ceramic film.

[0012] Further scheme: Sandpaper polishing (400 mesh sandpaper) is performed on the surface of the straw board substrate before roll coating in step 2 to remove surface burrs, ensure the surface roughness Ra≤2μm, remove impurities and make the surface smooth and flat, increase the contact area between the substrate and the inorganic sealing primer, and improve the uniformity of the primer coating, avoiding local over-thickness or under-thickness of the primer due to uneven substrate surface, and thus ensuring the quality and adhesion of the subsequent film coating.

[0013] Further scheme: after spraying in step 3, infrared heating curing is adopted, the temperature rising rate is controlled to be 5-10℃ / min in the curing process, the film cracking is avoided, the nano ceramic film is uniformly and fully cured, the performance such as film hardness and weather resistance reaches the standard, meanwhile, the stress concentration in the film caused by the too fast temperature rising rate is avoided, the film cracking problem is effectively prevented, and the film integrity and functional stability are ensured.

[0014] The present application has the following beneficial effects: The present application has the following beneficial effects: 3 The present application has the following beneficial effects: BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Structure diagram of the straw board coated with the nano ceramic and having the super weather-resistant self-cleaning function.

[0016] Figure 2 Step diagram of the preparation method of the straw board coated with the nano ceramic and having the super weather-resistant self-cleaning function.

[0017] In the figure: nano ceramic film 100, inorganic closed primer 200, straw board substrate 300. DETAILED DESCRIPTION

[0018] The principles and characteristics of the present application are described below in combination with the drawings, and the examples are only used to explain the present application and not to limit the scope of the present application.

[0019] The present application is further described in detail below in combination with specific examples, and the raw materials used in the examples are all commercially available conventional raw materials (for example, the silica microparticles are 20nm fumed silica, the polyurethane crosslinking agent is isocyanate, and the organic toughening agents are epoxy modified polysiloxane and acrylate respectively), and the quality inspection methods all refer to the national standards, and are as follows: Adhesion: tested according to GB / T5210-2006 “Color paint and varnish adhesion test by pull-off method”; Pencil hardness: tested according to GB / T6739-2022 “Color paint and varnish film hardness test by pencil method”; Weather resistance: test color difference ΔE according to GB / T 1865-2009 "Artificial weathering and artificial radiation exposure of paints and varnishes" (xenon lamp aging, irradiation intensity 0.71 W / m 2 @340 nm, 1000 h); Water resistance: test water absorption rate after soaking for 24 h according to GB / T 4897-2015 "Flakeboard"; Environmental protection: test TVOC according to GB / T 18883-2022, and test formaldehyde / VOC according to GB 18582-2020 "Limit of harmful substances in architectural wall coatings"; Strength: test static bending strength and elastic modulus according to GB / T 4897-2015; Example 1 (basic formula) 1. Preparation steps Step 1: Prepare straw board substrate 300: mix 97 parts by weight of straw, 3 parts by weight of environmentally friendly water-based glue, and 1 part by weight of polyurethane crosslinking agent uniformly, and hot-press at 130°C and 1.0 MPa for 30 min to obtain a substrate with a thickness of 15 mm; Step 2: Apply inorganic closed primer 200: the primer formula is potassium silicate 30 parts by weight, lithium silicate 15 parts by weight, silica microparticles 25 parts by weight, ethyl silicate hydrolysate 12 parts by weight, and epoxy modified polysiloxane toughening agent 2 parts by weight. Roll coating (speed 2 m / min) on the surface of the substrate, control the thickness to be 12 μm, and cure at 90°C for 30 min; Step 3: Apply nano ceramic film 100: the film formula is silica microparticles 50 parts by weight, zinc oxide microparticles 20 parts by weight, titanium dioxide microparticles 15 parts by weight, and acrylic ester toughening agent 3 parts by weight. Spray (pressure 0.4 MPa) on the surface of the primer, control the thickness to be 10 μm, and cure at 120°C for 45 min with a heating rate of 8°C / min; Test item Test result National standard / requirement Adhesion 1.8 MPa ≥1.5 MPa Pencil hardness 3H ≥3H Xenon lamp aging 1000 h ΔE 0.8 ≤1.0 Soaking 24 h water absorption 1.2% ≤1.5% TVOC (substrate) 67 μg / m 3 ]] ≤ 600 μg / m 3 ]] Formaldehyde (coating) Not detected ≤0.1 mg / m 3 ]] VOC (coating) Not detected ≤100 g / L Static bending strength 18 MPa ≥15 MPa Elastic modulus 2800 MPa ≥2500 MPa Example 2 (adjust the amount of organic toughening agent) 1. Preparation steps Compared with Example 1, only the following adjustments are made: The amount of epoxy modified polysiloxane toughening agent in the inorganic closed primer is 4 parts by weight; The amount of acrylic ester toughening agent in the nano ceramic film is 5 parts by weight; 2. Quality inspection parameters: Test item Test result National standard / requirement Adhesion 2.0 MPa ≥1.5 MPa Pencil hardness 3H ≥3H Xenon lamp aging 1000 h ΔE 0.7 ≤1.0 Soaking 24 h water absorption 1.1% ≤1.5% TVOC (substrate) 67 μg / m 3 ]] ≤ 600 μg / m 3 ]] Formaldehyde (coating) Not detected ≤0.1 mg / m 3 ]] VOC (coating) Not detected ≤100 g / L Static bending strength 17.5 MPa ≥15 MPa Elastic modulus 2750 MPa ≥2500 MPa Example 3 (adjust the curing temperature) 1. Preparation steps Compared with Example 1, only the following adjustments are made: The curing temperature of the inorganic closed primer is 100°C, and the curing time is 25 min; The curing temperature of the nano ceramic coating film is 130 DEG C, the curing time is 35 min, and the heating rate is 10 DEG C / min.

[0020] 2. Quality inspection parameters Test item Test result National standard / requirement Adhesion 1.7 MPa ≥1.5 MPa Pencil hardness 4H ≥3H Xenon lamp aging 1000 h ΔE 0.9 ≤1.0 Soaking 24 h water absorption 1.0% ≤1.5% TVOC (substrate) 67 μg / m 3 ]] ≤ 600 μg / m 3 ]] Formaldehyde (coating) Not detected ≤0.1 mg / m 3 ]] VOC (coating) Not detected ≤100 g / L Static bending strength 18.5 MPa ≥15 MPa Elastic modulus 2900 MPa ≥2500 MPa Comparative Example 1 (without inorganic sealing primer, simulating prior art) 1. Preparation steps Compared with Example 1, step 2 (inorganic sealing primer is not coated) is deleted, and the nano ceramic coating film (with the same formula as Example 1) is directly coated on the surface of the straw board substrate.

[0021] 2. Quality inspection parameters Test item Test result National standard / requirement Defect analysis Adhesion 0.6 MPa ≥1.5 MPa No interface layer, adhesion drops sharply due to hardness difference Pencil hardness 2H ≥3H Coating and substrate are poorly combined, and hardness cannot be guaranteed Xenon lamp aging 1000 h ΔE 3.5 ≤1.0 Coating is prone to cracking, and weather resistance fails Soaking 24 h water absorption 3.8% ≤1.5% Coating peels off, and substrate directly absorbs water TVOC (substrate) 67 μg / m 3 ]] ≤ 600 μg / m 3 ]] Substrate is environmentally friendly, but the coating fails Formaldehyde (coating) Not detected ≤0.1 mg / m 3 ]] - VOC (coating) Not detected ≤100 g / L - Static bending strength 18 MPa ≥15 MPa Substrate strength is qualified, but the coating drags performance Elastic modulus 2800 MPa ≥2500 MPa - Comparative Example 2 (traditional glue + no polyurethane crosslinking, simulating existing straw board) 1. Preparation steps Compared with Example 1, the following adjustments are made: In step 1, urea-formaldehyde resin glue (10 parts by weight) is used instead of environmentally friendly water-based glue, and no polyurethane crosslinking agent is added, and the hot pressing conditions remain unchanged; Steps 2 and 3 are the same as Example 1.

[0022] 2. Quality inspection parameters Test item Test result National standard / requirement Defect analysis Adhesion 1.6 MPa ≥1.5 MPa Adhesion is qualified under the action of primer, but the substrate is poor in environmental friendliness Pencil hardness 3H ≥3H Coating performance is qualified, but the substrate drags overall environmental friendliness Xenon lamp aging 1000 h ΔE 1.1 ≤1.0 Close to the upper limit, the substrate is prone to release small molecules, affecting the weather resistance of the coating Soaking 24 h water absorption 1.3% ≤1.5% Qualified TVOC (substrate) 380 μg / m 3 ]] ≤ 600 μg / m 3 ]] far beyond the application (67 μg / m 3 ), poor environmental performance Formaldehyde (substrate) 0.15 mg / m 3 ]] ≤0.1 mg / m 3 ]] Exceeds the standard, traditional glue releases formaldehyde VOC (coating) Not detected ≤100 g / L - Static bending strength 11 MPa ≥15 MPa Not cross-linked, insufficient strength, cannot bear construction Elastic modulus 2000 MPa ≥2500 MPa Insufficient, substrate is prone to deformation Example and comparative example parameter comparison and analysis Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Advantages of the present application Adhesion (MPa) 1.8 2.0 1.7 0.6 1.6 Inorganic closed primer improves adhesion by 183%-233% (vs. Comparative Example 1) Pencil hardness 3H 3H 4H 2H 3H Interface matching guarantees coating hardness, and Comparative Example 1 has a hardness drop of 1 level due to poor combination Xenon lamp aging ΔE 0.8 0.7 0.9 3.5 1.1 Weather resistance is much better than Comparative Example 1 (ΔE reduction of 77%), and better than Comparative Example 2 Water absorption rate (%) 1.2 1.1 1.0 3.8 1.3 Coating integrity is good, and the water absorption rate is only 32% of Comparative Example 1 TVOC (μg / m 3 )]> 67 67 67 67 380 Polyurethane cross-linking process reduces TVOC by 82% (vs. Comparative Example 2) Formaldehyde (mg / m 3 )]]> Not detected Not detected Not detected Not detected 0.15 Eco-friendly glue + formaldehyde-free paint, Example 2 exceeded 50% Modulus of rupture (MPa) 18 17.5 18.5 18 11 Polyurethane crosslinking increased strength by 64% (vs. Comparative Example 2) Summary: From the above comparison, it can be seen that the combination design of "inorganic sealing primer + polyurethane crosslinking substrate + optimized coating formula" in the present application is significantly superior to the prior art (Comparative Examples 1 and 2) in terms of adhesion, weather resistance, environmental protection, strength and other core indicators, especially solving the compatibility of "hard coating-soft substrate" and the environmental protection-strength contradiction of traditional boards.

[0023] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A straw board coated with nano-ceramic material and possessing ultra-weather-resistant and self-cleaning properties, characterized in that, From top to bottom, it includes nano-ceramic coating, inorganic sealing primer, and straw board substrate; The thickness of the nano-ceramic coating is 5-15 μm, and it is composed of the following components in parts by weight: 40-60 parts of silica microparticles, 15-25 parts of zinc oxide microparticles, 10-20 parts of titanium dioxide microparticles, and 1-5 parts of organic toughening agent. The inorganic sealing primer has a thickness of 8-20 μm and is composed of the following components in parts by weight: 25-40 parts potassium silicate, 10-20 parts lithium silicate, 20-35 parts silica microparticles, 8-15 parts ethyl silicate hydrolysate and 1-4 parts organic toughening agent. The thickness of the straw board substrate is 5-30mm, and it is composed of the following components in parts by weight: 95-99 parts straw and 1-5 parts glue.

2. The straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 1, characterized in that, The straw board substrate is prepared using a polyurethane cross-linking reaction process, and the static bending strength of the straw board substrate is ≥15MPa and the elastic modulus is ≥2500MPa, reaching the load-bearing strength level.

3. The straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 1, characterized in that, The VOC content and formaldehyde content of the coatings used to coat the nano-ceramic film and the inorganic sealing primer were not detected.

4. The straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 1, characterized in that, The TVOC content of the straw board substrate is 67 μg / m³.

5. The straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 4, characterized in that, The inorganic sealing primer is used to alleviate the differences in hardness and expansion coefficient between the nano-ceramic coating and the strawboard substrate, so that the adhesion between the nano-ceramic coating and the strawboard substrate is ≥1.5MPa.

6. A method for preparing a straw board coated with nano-ceramic material and possessing ultra-weather-resistant and self-cleaning properties, comprising the following steps: Step 1: Prepare straw board substrate. Take 95-99 parts by weight of straw and mix with 1-5 parts of glue. Add 0.5-2 parts of polyurethane crosslinking agent. Use polyurethane crosslinking reaction process to hot press and form at 120-150℃ and 0.8-1.2MPa for 20-40 minutes to obtain a load-bearing strength straw board substrate with a thickness of 5-30mm, static bending strength ≥15MPa, and elastic modulus ≥2500MPa. Step 2: Apply an inorganic sealing primer to the surface of the straw board substrate prepared in Step 1 using a roller coating method at a coating speed of 1-3 m / min. The inorganic sealing primer is composed of 25-40 parts potassium silicate, 10-20 parts lithium silicate, 20-35 parts silica microparticles, 8-15 parts ethyl silicate hydrolysate, and 1-4 parts organic toughening agent by weight. After coating, control the primer thickness to be 8-20 μm and cure at 80-100℃ for 20-40 min. Step 3: Apply a nano-ceramic coating to the surface of the inorganic sealing primer cured in Step 2 by spraying at a pressure of 0.3-0.5 MPa. The nano-ceramic coating consists of 40-60 parts by weight of silica microparticles, 15-25 parts by weight of zinc oxide microparticles, 10-20 parts by weight of titanium dioxide microparticles, and 1-5 parts by weight of organic toughening agent. After coating, control the coating thickness to be 5-15 μm and cure at 110-130℃ for 30-60 min to obtain a straw board with nano-ceramic coating and ultra-weather-resistant self-cleaning function.

7. The method for preparing the straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 6, characterized in that, The adhesive used in step 1 is an environmentally friendly water-based adhesive; The organic toughening agent mentioned in step 2 is an epoxy-modified polysiloxane; The organic toughening agent mentioned in step 3 is an acrylate toughening agent.

8. The method for preparing the straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 6, characterized in that, In step 2, the surface of the straw board substrate is sanded with 400-grit sandpaper before roller coating to remove surface burrs and ensure that the surface roughness Ra of the substrate is ≤2μm.

9. The method for preparing the straw board with ultra-weather-resistant and self-cleaning function coated with nano-ceramic according to claim 6, characterized in that, In step 3, infrared heating is used for curing after spraying. During the curing process, the heating rate is controlled at 5-10℃ / min to avoid cracking of the coating.

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