Composite protective coating based on tung oil, and preparation and use methods thereof

Abstract

The invention relates to a composite protective coating based on tung oil, and a preparation and use method thereof, and belongs to the technical field of protective coatings. The paint is mainly prepared by compounding natural tung oil, modified nano titanium dioxide, hexagonal boron nitride, a silane coupling agent KH-550, mica powder, talcum powder, hydrogenated castor oil, a polyurethane prepolymer, a cosolvent and the like, and is prepared by adopting a step-by-step pre-dispersion and ultraviolet auxiliary curing process, the modified nano titanium dioxide is nano titanium dioxide subjected to surface treatment by a silane coupling agent, and the particle size is 20-50nm; the hexagonal boron nitride powder is of a sheet structure, the thickness is smaller than or equal to 100 nm, and the length-diameter ratio is 50-100. The polyurethane prepolymer is an isocyanate group terminated polyether type prepolymer, and the functionality of the polyurethane prepolymer is 2 to 3. Compared with the prior art, the coating disclosed by the invention realizes dustproof, high-temperature-resistant and moisture-proof effects through the synergistic effect of hexagonal boron nitride and modified nano titanium dioxide.

Description

Technical field

[0001] The invention relates to the technical field of protective coatings, and in particular to a tung oil-based composite protective coating, and a preparation and use method thereof. [Background Technology]

[0002] Tung oil, a natural vegetable oil, is currently widely used in anti-corrosion coatings due to its excellent film-forming and hydrophobic properties. For example, patent CN107459930A discloses a tung oil-zinc powder anti-corrosion system. However, existing tung oil-based coatings have the following technical drawbacks:

[0003] Traditional tung oil coatings, with their limited functionality, primarily focus on corrosion protection and waterproofing, but lack the dust-proofing and high-temperature resistance required for high-speed rotating components, such as fan blades. For example, the tung oil / silicon dioxide composite coating used in patent CN119432224A, while offering some performance improvements, fails to effectively address the dust accumulation caused by electrostatic adsorption during high-speed rotation.

[0004] The mechanical properties are insufficient and the tung oil is brittle after curing. For example, the pure tung oil coating mentioned in patent CN112480814A is prone to cracking and falling off under the action of high-speed centrifugal force, and cannot meet the long-term use requirements of high-speed rotating parts such as fan blades.

[0005] Existing tung oil-based coatings have poor environmental adaptability and experience significant loss of adhesion in high-temperature and high-humidity environments. For example, the tung oil-acrylic acid emulsion coating disclosed in patent CN115232536A loses over 40% of its adhesion after wet-heat aging, making it difficult to stably apply in industrial equipment.

[0006] Conventional tung oil paints have low process compatibility and require a long curing time (usually more than 24 hours) using a heat-curing process, which is unable to meet the rapid coating requirements of precision components such as fan blades. For example, the heat-curing process used in patent CN110591465A has a long curing time and low efficiency.

[0007] In view of the above technical problems, the present invention is proposed in this study. [Summary of the invention]

[0008] The technical problem addressed by this invention is to provide a tung oil-based composite protective coating, as well as methods for its preparation and use. Through component optimization and process innovation, the present invention has developed a tung oil-based composite coating that combines dust and moisture resistance with high temperature resistance and mechanical strength. This coating not only addresses the limitations of existing tung oil-based coatings, such as limited functionality, insufficient mechanical properties, poor environmental adaptability, and low process compatibility, but also significantly improves the overall performance of the coating, meeting the requirements of high-end applications such as high-speed rotating devices.

[0009] To solve the above technical problems, the present invention proposes a tung oil-based composite protective coating, which comprises the following components in parts by weight:

[0010] 20-35 parts of natural tung oil;

[0011] 5-10 parts of modified nano titanium dioxide;

[0012] 3-8 parts of hexagonal boron nitride powder;

[0013] Silane coupling agent KH-5501—3 parts;

[0014] 4-8 parts of mica powder;

[0015] 2-5 parts of talcum powder;

[0016] 0.5-1.5 parts hydrogenated castor oil;

[0017] 10-15 parts of polyurethane prepolymer;

[0018] 5-10 parts of cosolvent;

[0019] The modified nano-titanium dioxide is nano-titanium dioxide surface-treated with a silane coupling agent, with a particle size of 20-50 nm; the hexagonal boron nitride powder is a flaky structure with a thickness of ≤100 nm and an aspect ratio of 50-100; and the polyurethane prepolymer is an isocyanate-terminated polyether prepolymer with a functionality of 2-3.

[0020] As described above, the protective coating modified based on tung oil, the natural tung oil is unpolymerized raw tung oil, the acid value is ≤5mg KOH / g, and the iodine value is ≥160g I2 / 100g; the turpentine oil and the co-solvent are a mixed solvent of propylene glycol methyl ether acetate in a weight ratio of 1:3.

[0021] As described above, a protective coating based on tung oil modification is prepared by a method of preparing the modified nano-titanium dioxide: dispersing nano-titanium dioxide in anhydrous ethanol, adding a silane coupling agent KH-550, wherein the weight proportion of the silane coupling agent KH-550 is 5%-8% of the titanium dioxide, ultrasonically treating the mixture at 60°C for 2 hours, and centrifugally drying the mixture to obtain surface-modified nano-titanium dioxide.

[0022] In the protective coating modified with tung oil as described above, the mass ratio of the mica powder to the hexagonal boron nitride powder is 1:1.5 to 1:2.5, and the two are mixed and ball-milled to an average particle size of ≤5 μm.

[0023] The polyurethane prepolymer of the tung oil-modified protective coating is prepared by reacting polytetramethylene glycol with a molecular weight of 2000 with isophorone diisocyanate at a -OH / -NCO molar ratio of 1:2.2, and the free isocyanate group content in the prepolymer is 6% to 8%.

[0024] A method for preparing a composite protective coating of the present application comprises using the components of the composite protective coating, and comprises the following steps:

[0025] S1. Mix modified nano-titanium dioxide, hexagonal boron nitride powder and silane coupling agent KH-550, and stir and react at 80° C. for 1 hour to obtain a pre-dispersed composite powder;

[0026] S2. Heat natural tung oil to 70-80° C., add the pre-dispersed composite powder obtained in step S1, and disperse at a high shear speed of 800-1200 rpm for 30 minutes;

[0027] S3, add mica powder, talc powder, and hydrogenated castor oil in sequence, and continue stirring until a uniform slurry is obtained;

[0028] S4. Cooling to below 50°C, adding polyurethane prepolymer and cosolvent, and vacuum degassing to obtain the finished coating.

[0029] In the above-mentioned method for preparing a composite protective coating, the vacuum degassing condition in step S4 is to maintain a vacuum degree of -0.08-0.1 MPa for 20-30 minutes.

[0030] The present application also provides a method for using the composite protective coating, including using the composite protective coating, and the method includes the following steps:

[0031] (a) The substrate surface was sandblasted to a roughness of Ra = 3-5 μm and then cleaned and degreased with acetone;

[0032] (b) The coating is evenly applied to the substrate surface using a high-pressure airless spray process, with a single-layer wet film thickness of 80-120 μm;

[0033] (c) Pre-curing at 40-60°C for 1 hour, followed by UV curing for 10 minutes, with a total dry film thickness of 50-80 μm.

[0034] In the method for using the composite protective coating as described above, the wavelength of the ultraviolet light is 365 nm and the intensity is 80 mW / cm.

[0035] In the method for using the composite protective coating as described above, the substrate is a metal fan blade or a wooden fan blade or wooden furniture or a concrete wall or a plastic product.

[0036] Compared with the prior art, the tung oil-based composite protective coating, preparation method and use method of the present invention have the following advantages:

[0037] 1. Highly effective dust prevention: The photocatalytic decomposition properties of modified nano-titanium dioxide and the surface energy reduction effect of hexagonal boron nitride synergistically achieve a water contact angle on the coating surface of 150° or greater. When the fan blades rotate at high speeds, dust accumulation can be reduced by 60% to 80%, a significant improvement over the 30% to 50% reduction achieved with existing technologies.

[0038] 2. Resistant to heat and humidity aging, the polyurethane prepolymer and tung oil form an interpenetrating network structure. In a hot and humid environment of 85℃ / 95% relative humidity, the coating adhesion retention rate can reach more than 90%, which is significantly better than the 70% and below of traditional tung oil coatings.

[0039] 3. Rapid curing: UV-assisted curing process is used, and the total curing time is shortened to 1.5 hours. Compared with the conventional thermal curing process of 24 hours or more, it greatly improves production efficiency and is particularly suitable for industrial assembly line operations.

[0040] 4. Applicable to multiple scenarios. By adjusting the filler ratio, such as the ratio of mica powder to talcum powder, it can be adapted to various substrates such as metal, wood, concrete, etc., and is widely used in furniture, construction and other fields.

Brief Description of the Drawings

[0041] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0042] Figure 1 This is a comparison chart of experimental data between the embodiment and the comparative example in the invention

[0043] Figure 2 It is a comparison chart of the core differences between the invention and the prior art. [Specific implementation method]

[0044] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0045] Example 1:

[0046] A composite protective coating based on tung oil, comprising the following components in parts by weight:

[0047] 25 parts of natural tung oil, 6 parts of modified nano-TiO2, 4 parts of hexagonal boron nitride, 1.5 parts of KH-550, 5 parts of mica powder, 3 parts of talc, 1 part of hydrogenated castor oil, 12 parts of polyurethane prepolymer, and 7 parts of cosolvent. The ratio of turpentine to PMA is 1:3.

[0048] The preparation method of the composite protective coating is as follows:

[0049] 1. Preparation of modified nano-titanium dioxide: Nano-titanium dioxide was dispersed in anhydrous ethanol, and a silane coupling agent KH-550 was added, wherein the weight proportion of the silane coupling agent KH-550 was 6% of the titanium dioxide. The mixture was ultrasonically treated at 60° C. for 2 hours, and centrifuged and dried to obtain surface-modified nano-titanium dioxide.

[0050] 2. Premix the modified nano-sized dioxide, titanium hexagonal boron nitride and KH-550 at 80°C for 1 hour to obtain a pre-dispersed composite powder;

[0051] 3. Heat natural tung oil to 75°C, add pre-dispersed composite powder, and disperse at high shear speed of 1200 rpm for 30 minutes;

[0052] 4. Add mica powder, talc powder, and hydrogenated castor oil in sequence and continue stirring until a uniform slurry is formed;

[0053] 5. Cool down to 40°C, add polyurethane prepolymer and cosolvent, and vacuum degas for 25 minutes at a vacuum degree of -0.09 MPa to obtain the finished coating.

[0054] How to use composite protective coating:

[0055] 1. Sandblast the surface of the metal fan blade to a roughness of Ra = 4μm, and clean and degrease it with acetone;

[0056] 2. Use high-pressure airless spraying technology to evenly apply the paint on the surface of the substrate with a spraying thickness of 100μm;

[0057] 3. Pre-cure at 50°C for 1 hour, then cure under ultraviolet light with a wavelength of 365nm and an intensity of 80mW / cm for 10 minutes.

[0058] Comparative Example 1:

[0059] Hexagonal boron nitride was not used, and the rest was the same as in Example 1.

[0060] The differences between Example 1 and Comparative Example 1 are:

[0061] In Example 1, the surface energy is reduced due to the flaky structure of hexagonal boron nitride, and the water contact angle reaches 152°, which is 10.1% higher than the water contact angle of 152° in Comparative Example 1. The salt spray resistance time of Comparative Example 1 is 600 hours, while the salt spray resistance test of Example 1 is 1050 hours.

[0062] Example 2:

[0063] The hexagonal boron nitride in the composite protective coating was increased to 8 parts, and the talc powder was reduced to 2 parts. The rest was the same as in Example 1.

[0064] Comparative Example 2: Hexagonal boron nitride was replaced with an equal amount of graphene, and the rest was the same as in Example 2.

[0065] The difference between Example 2 and Comparative Example:

[0066] Because hexagonal boron nitride has a high thermal conductivity of 30 W / m·K, the coating's heat dissipation efficiency increased by 40%. Compared with Comparative Example 2, the temperature rise of the fan blade during continuous operation was reduced by 15°C.

[0067] Example 3:

[0068] The polyurethane prepolymer in the composite protective coating was increased to 15 parts, the functionality was 3, the cosolvent was reduced to 5 parts, and the rest was the same as in Example 1.

[0069] Comparative Example 3:

[0070] The polyurethane was replaced by an equal amount of epoxy resin E-51, and the rest was the same as in Example 3.

[0071] The differences between Example 3 and Comparative Example 3 are:

[0072] In Example 3, the UV curing time was shortened to 8 minutes, while the thermal curing time was 2 hours in Comparative Example 3. The coating hardness reached 2H, while that of Comparative Example 3 was H.

[0073] Example 4:

[0074] The ratio of mica powder to talc powder in the composite protective coating was adjusted to 8:2, KH-550 was increased to 2.5 parts, and the rest was the same as in Example 1.

[0075] Comparative Example 4:

[0076] The mica powder was replaced with an equal amount of calcium carbonate. The rest was the same as in Example 4.

[0077] The differences between Example 4 and Comparative Example 4 are:

[0078] The adhesion of the coating on the concrete substrate reaches 8.5 MPa, while that of Comparative Example 4 is only 4.2 MPa. After wet heat aging, the adhesion retention rate is 95%.

[0079] Example 5:

[0080] The modified nano-TiO2 in the composite protective coating was increased to 10 parts, and 1 part of polydimethylsiloxane was added. The rest was the same as in Example 1.

[0081] Comparative Example 5:

[0082] No polydimethylsiloxane was used and unmodified nano-TiO2 was used. The rest was the same as in Example 5.

[0083] The differences between Example 5 and Comparative Example 5 are:

[0084] The photocatalytic self-cleaning performance reduced the dust accumulation by 85%, while the comparative example 5 only reduced it by 50%.

[0085] Example 6:

[0086] The functionality of the polyurethane prepolymer in the composite protective coating was adjusted to 2, and the amount of hydrogenated castor oil was increased to 1.5 parts. The rest was the same as in Example 1.

[0087] Comparative Example 6:

[0088] The functionality of the polyurethane prepolymer was adjusted to 3, and 0.5 parts of hydrogenated castor oil was added. The rest was the same as in Example 6.

[0089] The differences between Example 6 and Comparative Example 6 are as follows:

[0090] The elongation at break of the coating is increased to 120%, while it is only 60% in Comparative Example 6. This performance improvement makes it particularly suitable for bending conditions of plastic substrates.

[0091] Example 7:

[0092] The tung oil in the composite protective coating was increased to 30 parts, and the polyurethane prepolymer was reduced to 10 parts. The rest was the same as in Example 1.

[0093] Comparative Example 7: The amount of tung oil was reduced to 15 parts, and the amount of polyurethane was increased to 20 parts. The rest was the same as in Example 7.

[0094] The differences between Example 7 and Comparative Example 7 are as follows:

[0095] In Example 7, the cost was reduced by 18%, while the salt spray resistance time was still up to 900 hours. In contrast, in Comparative Example 7, due to the insufficient tung oil content, the salt spray resistance time was only 700 hours.

[0096] Example 8:

[0097] The ratio of mica powder to talc powder in the composite protective coating was adjusted to 1:1, the cosolvent was replaced with a mixture of xylene and ethyl acetate in a ratio of 2:1, and the rest was the same as in Example 1.

[0098] Comparative Example 8: The filler ratio was not adjusted, and the cosolvent was pure PMA.

[0099] The differences between Example 8 and Comparative Example 8 are:

[0100] In Example 8, the penetration of the coating on the wood substrate was improved by 30%, and the drying time was shortened to 40 minutes, while the comparative example 8 required 60 minutes.

[0101] Experimental data comparison table Figure 1 shown.

[0102] Based on the above implementation data and Figure 1 It can be seen that

[0103] In Examples 1-8, hexagonal boron nitride, modified nano-TiO2 and polyurethane prepolymer were introduced to significantly improve the dustproof, salt spray resistance and adhesion properties.

[0104] The specific comparison is as follows:

[0105] Hexagonal Boron Nitride:

[0106] After adding hexagonal boron nitride to Examples 1 and 2, the performance is significantly improved, while the performance of Comparative Examples 1 and 2 is poor due to the lack of this component.

[0107] Modified nano-TiO2: The use of modified nano-TiO2 in Example 5 significantly enhanced the self-cleaning performance, while the performance of Comparative Example 5 was significantly deteriorated due to the lack of modified TiO2.

[0108] Polyurethane prepolymer: In Example 3, polyurethane prepolymer was used, and the curing time was greatly shortened, and the adhesion and salt spray resistance were also improved. However, in Comparative Example 3, the performance was greatly reduced due to the replacement of epoxy resin.

[0109] UV curing process: Example 3 adopts UV curing process, which shortens the curing time to 65 minutes, which is much lower than the thermal curing process (120 minutes) of Comparative Example 3, significantly improving production efficiency.

[0110] Step-by-step pre-dispersion process:

[0111] Examples 1 and 5 use a step-by-step pre-dispersion process to uniformly disperse the filler and control the porosity to ≤5%. However, since Comparative Example 5 does not use this process, the porosity is as high as ≥15%, resulting in unstable coating performance.

[0112] Cost and performance balance:

[0113] By increasing the proportion of tung oil, Example 7 successfully reduced costs by 18% while maintaining 900 hours of salt spray resistance. In contrast, the performance of Comparative Example 7 was significantly degraded due to insufficient tung oil content. This demonstrates that reasonable component adjustment can effectively balance performance and cost while optimizing costs.

[0114] Improvements to the core difference summary function:

[0115] Dust prevention efficiency: The dust prevention efficiency of all embodiments is significantly improved, and the dust accumulation reduction rate reaches or exceeds 68%, while the dust accumulation reduction rates of the comparative example and the prior art do not exceed 60% and 50%, respectively.

[0116] Salt spray resistance: The salt spray resistance time of Examples 1-8 all reached or exceeded 850 hours, far exceeding the salt spray resistance time of the prior art (no more than 500 hours).

[0117] Process innovation:

[0118] UV curing process: Example 3 and Example 8 use UV curing process, which greatly shortens the curing time to 40 to 65 minutes, significantly improving production efficiency compared to the traditional thermal curing process (120 minutes or more). Cost-effectiveness:

[0119] By optimizing the proportion of tung oil and the co-solvent formula, Examples 7 and 8 achieved a cost reduction of 10% to 18% while maintaining high performance, thus achieving a balance between cost and performance.

[0120] In the present invention, the substrate can be a metal fan blade, a wooden fan blade, wooden furniture, a concrete wall, or a plastic product.

[0121] The main differences between this application and the prior art are as follows Figure 2 shown.

Claims

1. A composite protective coating based on tung oil, characterized by Includes the following components: 20-35 parts of natural tung oil; 5-10 parts of modified nano titanium dioxide; 3-8 parts of hexagonal boron nitride powder; Silane coupling agent KH-5501—3 parts; 4-8 parts of mica powder; 2-5 parts of talcum powder; 0.5-1.5 parts hydrogenated castor oil; 10-15 parts of polyurethane prepolymer; 5-10 parts of cosolvent; The modified nano-titanium dioxide is nano-titanium dioxide surface-treated with a silane coupling agent, with a particle size of 20-50 nm; the hexagonal boron nitride powder is a flaky structure with a thickness of ≤100 nm and an aspect ratio of 50-100; and the polyurethane prepolymer is an isocyanate-terminated polyether prepolymer with a functionality of 2-3.

2. The tung oil-based composite protective coating according to claim 1, characterized in that The natural tung oil is unpolymerized raw tung oil with an acid value of ≤5mg KOH / g and an iodine value of ≥160g I2 / 100g; the turpentine oil and the co-solvent are a mixed solvent of propylene glycol methyl ether acetate in a weight ratio of 1:

3.

3. The tung oil-based composite protective coating according to claim 1, characterized in that The preparation method of the modified nano titanium dioxide is as follows: nano titanium dioxide is dispersed in anhydrous ethanol, a silane coupling agent KH-550 is added, wherein the mass proportion of the silane coupling agent KH-550 is 5%-8% of the titanium dioxide, ultrasonic treatment is performed at 60°C for 2 hours, and centrifugal drying is performed to obtain surface-modified nano titanium dioxide.

4. The protective coating modified with tung oil according to claim 1, characterized in that The mass ratio of the mica powder to the hexagonal boron nitride powder is 1:1.5 to 1:2.

5. After the two are mixed, they are ball-milled to an average particle size of ≤5 μm.

5. The tung oil-based composite protective coating according to claim 1, characterized in that The polyurethane prepolymer is prepared by reacting polytetramethylene glycol with a molecular weight of 2000 with isophorone diisocyanate at a -OH / -NCO molar ratio of 1:2.

2. The free isocyanate group content in the prepolymer is 6% to 8%.

6. A method for preparing a composite protective coating, comprising using the tung oil-based composite protective coating according to any one of claims 1 to 5, characterized in that The following steps are involved: S1. Mix modified nano-titanium dioxide, hexagonal boron nitride powder and silane coupling agent KH-550, and stir and react at 80° C. for 1 hour to obtain a pre-dispersed composite powder; S2. Heat natural tung oil to 70-80° C., add the pre-dispersed composite powder obtained in step S1, and disperse at a high shear speed of 800-1200 rpm for 30 minutes; S3, add mica powder, talc powder, and hydrogenated castor oil in sequence, and continue stirring until a uniform slurry is obtained; S4. Cooling to below 50°C, adding polyurethane prepolymer and cosolvent, and vacuum degassing to obtain the finished coating.

7. The method for preparing a composite protective coating according to claim 6, characterized in that The vacuum degassing condition in step S4 is to maintain a vacuum degree of -0.08-0.1 MPa for 20 to 30 minutes.

8. A method for using a tung oil-based composite protective coating, comprising the steps of: (a) The substrate surface was sandblasted to a roughness of Ra = 3-5 μm and then cleaned and degreased with acetone; (b) The coating is evenly applied to the substrate surface using a high-pressure airless spray process, with a single-layer wet film thickness of 80-120 μm; (c) Pre-curing at 40-60°C for 1 hour, followed by UV curing for 10 minutes, with a total dry film thickness of 50-80 μm.

9. The method for using the composite protective coating according to claim 8, characterized in that The wavelength of the ultraviolet light is 365 nm, and the intensity is 80 mW / cm.

10. The method for using the composite protective coating according to claim 8, characterized in that The substrate is a metal fan blade or a wooden fan blade or wooden furniture or a concrete wall or a plastic product.

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