A bio-based polyurethane anticorrosive coating material, a preparation method and application thereof

Abstract

The application discloses a kind of bio-based polyurethane anticorrosive paint, including A component, B component and C component, the mass ratio of A component, B component and C component is 1: (0.4-0.6): (1-1.5);The A component includes bio-based hydroxyl resin 70-90 parts, bio-based diluent 5-10 parts, auxiliary 2-5.3 parts, functional filler 6-12 parts by mass fraction;B component includes isocyanate;The C component includes portland cement 35-55 parts, calcium hydroxide 5-10 parts, active powder 3-8, color filler 38-50 parts by mass fraction.In addition, the preparation method and application of the bio-based polyurethane anticorrosive paint are also disclosed.The application uses solvent-free organic-inorganic composite polyurethane system, with very low VOC content, meet environmental requirements, and can adapt to short low tide construction window period and various concrete base, efficiently complete the repair construction of marine facilities, play a long-term anticorrosion effect.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a bio-based polyurethane anticorrosive coating, its preparation method, and its application. Background Technology

[0002] In marine engineering, especially in harbor engineering, applying anti-corrosion coatings to the concrete structures of marine facilities is a common protective measure to improve their structural durability. These facilities operate in harsh environments, and the main challenges in corrosion prevention are concentrated in the areas above sea level. According to the corrosion type classification in JT / T695-2007 "Technical Conditions for Anti-corrosion Coating of Concrete Bridge Structures," this area corresponds to the water level fluctuation zone and splash zone in seawater or saltwater (Im2) environments.

[0003] This area is primarily affected by corrosion and erosion from salt spray, marine atmosphere, and wave splash. The structural surfaces are constantly moist, resulting in corrosion rates several times higher than in atmospheric and submerged areas. Key factors contributing to severe corrosion include intense solar radiation, alternating wet and dry environments rich in chloride ions, and continuous tidal erosion. Therefore, in areas of fluctuating water levels and wave splash zones (such as bridge piers and near-shore sections of cross-sea highways), the anti-corrosion coating is more prone to aging and damage.

[0004] Currently, a large number of offshore engineering facilities in service have significant needs for partial maintenance, and the workload of refurbishment and maintenance will continue to increase in the coming years. However, the maintenance and construction environment in the water level fluctuation zone and splash zone of offshore engineering facilities is harsh, the maintenance is difficult, and the requirements for the physical and chemical properties and construction performance of the coating are stringent. At present, the main difficulties in maintenance in this area are: 1. The substrate is in a damp state for a long time, and it is mostly a simple treated concrete or old coating surface, which makes it difficult for the coating to adhere well; 2. The effective construction window is very short, and the coating is prone to failure due to water immersion before it is fully cured; 3. The construction conditions are complex, and the requirements for construction convenience are high, requiring adaptation to simple construction methods; 4. Multiple construction steps are time-consuming and labor-intensive, making it difficult to meet the requirements for rapid repair; 5. The repaired coating will still be subject to long-term corrosion by seawater, splash, and salt spray, making it difficult to achieve long-term corrosion protection.

[0005] Meanwhile, traditional marine engineering anti-corrosion coatings generally have high VOC content, which makes it difficult to meet current environmental protection requirements. This problem also urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a bio-based polyurethane anti-corrosion coating, its preparation method and application, to adapt to damp substrates and meet the requirements of long-term anti-corrosion and rapid construction.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A bio-based polyurethane anticorrosive coating comprises component A, component B, and component C, wherein the mass ratio of component A, component B, and component C is 1:(0.4-0.6):(1-1.5); by mass parts, component A comprises 70-90 parts of bio-based hydroxyl resin, 5-10 parts of bio-based diluent, 2-5.3 parts of additives, and 6-12 parts of functional filler; component B comprises isocyanate; and by mass parts, component C comprises 35-55 parts of silicate cement, 5-10 parts of calcium hydroxide, 3-8 parts of active powder, and 38-50 parts of pigments and fillers.

[0009] Furthermore, the isocyanate includes aromatic isocyanate and aliphatic isocyanate, wherein the aromatic isocyanate has a mass fraction of 75-95 parts, and the aliphatic isocyanate has a mass fraction of 5-25 parts; the coating has an isocyanate index of 1-1.6, the aromatic isocyanate has a functionality of 2.2-2.7, and the castor oil bio-based polyol has a functionality of 3.0-3.5.

[0010] Furthermore, the aromatic isocyanate is polymeric MDI; the aliphatic isocyanate is IPDI-TMP adduct, HDI trimer, or a mixture thereof; the B component further includes a stabilizer, which is a monofunctional isocyanate, triethyl orthoformate, or a mixture thereof, and the stabilizer is present in a mass fraction of 0.5-1 parts.

[0011] Furthermore, the bio-based hydroxyl resin is castor oil bio-based polyol; the bio-based diluent is fatty acid ester, tributyl citrate, or a mixture thereof; the functional filler is molecular sieve activated powder; the activated powder is microsilica powder; the pigments and fillers include filler, titanium dioxide, and color powder, wherein the filler is barium sulfate, quartz powder, or a mixture thereof, the filler has a mass fraction of 30-40 parts, the titanium dioxide has a mass fraction of 8-15 parts, and the color powder has a mass fraction of 0-5 parts.

[0012] Furthermore, the additives include 0.3-0.8 parts of dispersant, 0.3-0.7 parts of defoamer, 0.7-1.5 parts of rheology modifier, 0.2-1 parts of antioxidant, 0.2-0.5 parts of ultraviolet absorber, and 0.3-0.8 parts of adhesion promoter.

[0013] Furthermore, the rheology modifier includes a first rheology modifier and a second rheology modifier. The first rheology modifier is organically modified bentonite, hydrophobically modified fumed silica, or a mixture thereof. The second rheology modifier is polyamide wax paste, polyethylene wax paste, or a mixture thereof. The mass fraction of the first rheology modifier is 0.5-1 parts, and the mass fraction of the second rheology modifier is 0.2-0.5 parts.

[0014] Furthermore, the antioxidant includes hindered phenolic antioxidants and phosphite antioxidants, wherein the hindered phenolic antioxidants are present in a mass fraction of 0.1-0.5 parts, the phosphite antioxidants are present in a mass fraction of 0.1-0.5 parts, and the mass ratio of the hindered phenolic antioxidants to the phosphite antioxidants is (1-2):1.

[0015] Furthermore, the dispersant is a carboxylate dispersant, a polyurethane dispersant, or a mixture thereof; the defoamer is an organosilicon defoamer; the ultraviolet absorber is a benzophenone ultraviolet absorber or a benzotriazole ultraviolet absorber; and the adhesion promoter is a silane coupling agent or a titanate adhesion promoter.

[0016] The present invention also provides a method for preparing the above-mentioned bio-based polyurethane anticorrosive coating, comprising the following steps: S1. Prepare components A, B, and C in advance; The preparation steps of component A are as follows: a1. Take a portion of bio-based hydroxyl resin and mix it evenly with a bio-based diluent. During the mixing process, add a dispersant, defoamer, and rheology modifier. After mixing evenly, obtain a first mixture; a2. Slowly add functional fillers, antioxidants, and ultraviolet absorbers to the first mixture and gradually increase the rotation speed for high-speed dispersion. After even dispersion, obtain a second mixture; a3. Slowly add the remaining bio-based hydroxyl resin to the second mixture and gradually decrease the rotation speed for mixing evenly, obtain a third mixture; a4. Gradually decrease the rotation speed and heat the third mixture to 110-120℃, then dehydrate the third mixture under vacuum conditions; a5. Cool the dehydrated third mixture to 60-80℃, add an adhesion promoter, and stir evenly to obtain component A; The preparation steps of component B are as follows: aromatic isocyanate, aliphatic isocyanate and stabilizer are mixed in a nitrogen atmosphere, and the mixture is thoroughly mixed to obtain component B. The preparation steps of component C are as follows: c1. Pre-drying calcium hydroxide, active powder, and pigments and fillers; c2. Mixing silicate cement, calcium hydroxide, active powder, and pigments and fillers evenly to obtain component C; S2. Stir component A thoroughly, then add component B to component A and mix evenly. Then gradually add component C to disperse it evenly, thus obtaining the bio-based polyurethane anti-corrosion coating.

[0017] The present invention also provides the application of the above-mentioned bio-based polyurethane anti-corrosion coating in marine engineering.

[0018] The present invention has the following beneficial effects: 1. The coating system is a solvent-free organic-inorganic composite polyurethane system. It uses bio-based hydroxyl resin as the matrix resin and combines it with bio-based diluent to adjust the viscosity. This can significantly reduce the VOC content of the coating, meet environmental protection requirements, and the curing conditions and time are flexible and adjustable. It can adapt to short low tide construction windows and efficiently complete the repair construction.

[0019] 2. The coating system incorporates inorganic powders such as silicate cement, active powder, and calcium hydroxide, which enhances the coating's adaptability to various concrete substrates, relaxes substrate treatment requirements, and even allows direct application to damp substrates without standing water, forming an anchoring connection with the damp substrate. This significantly improves the operability of application in areas with fluctuating water levels and splash zones. Simultaneously, the hydration products of the inorganic powders can combine with the polyurethane skeleton formed by cross-linking bio-based hydroxyl resins and isocyanates to construct an organic-inorganic interpenetrating network (IPN) structure. This endows the coating with excellent mechanical properties, chemical resistance, durability, and applicability to complex substrate environments, achieving long-term corrosion protection. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments.

[0021] Example 1 This invention provides a bio-based polyurethane anticorrosive coating, comprising three components: component A, component B, and component C. The mass ratio of components A, B, and C is 1:(0.4-0.6):(1-1.5), such as 1:0.45:1.2, 1:0.5:1.3, 1:0.55:1.4, etc. By mass parts, component A comprises 70-90 parts of bio-based hydroxyl resin, 5-10 parts of bio-based diluent, 2-5.3 parts of additives, and 6-12 parts of functional filler; component B comprises isocyanate; and by mass parts, component C comprises 35-55 parts of silicate cement, 5-10 parts of calcium hydroxide, 3-8 parts of active powder, and 38-50 parts of pigments and fillers.

[0022] The entire coating system is a high-solids-content solvent-free organic-inorganic composite polyurethane system. It uses bio-based hydroxyl resin produced from natural renewable materials as the matrix resin and combines it with bio-based diluents to adjust the viscosity. This can significantly reduce the VOC content of the coating and achieve the effect of almost zero VOC emissions during the coating process. It has the advantages of being green, environmentally friendly, low-carbon and sustainable, and has great development potential.

[0023] This coating boasts high adaptability in its application. The introduction of inorganic powders such as silicate cement, active powder, and calcium hydroxide enhances its compatibility with various concrete substrates, relaxing surface preparation requirements. It can even be applied directly to damp surfaces without standing water, forming an anchoring connection with the damp surface. This significantly improves the operability of application in areas with fluctuating water levels and splash zones. Furthermore, the flexible curing conditions and time of the polyurethane system allow for efficient repair work on marine facilities during brief low tide periods, enabling them to be put into use 5-6 hours after application.

[0024] Meanwhile, the hydration products of inorganic powders can combine with the polyurethane skeleton formed by cross-linking of bio-based hydroxyl resins and isocyanates to construct an organic-inorganic interpenetrating network (IPN) structure, which endows the coating with excellent mechanical properties, chemical resistance, durability and applicability to complex substrate environments, achieving long-term corrosion protection after construction.

[0025] The organic network in the organic-inorganic interpenetrating network (IPN) structure is a polyurethane backbone formed by the gelation and crosslinking reaction of isocyanate and bio-based hydroxyl resin. The urethane bonds (-NH-COO-) generated in the reaction construct a three-dimensional crosslinked polyurethane backbone, which, through crosslinking and entanglement, constitutes the continuous organic phase within the interpenetrating network. The main polyurethane reaction involved is shown below: 2NCO-R+HO-R′-OH→R-NH-COO-R′-OOC-NH-R (Main reaction of polyurethane) When the environment and substrate contain moisture, a polyurethane side reaction (foaming reaction) occurs. The carbon dioxide generated from the reaction of isocyanate with trace amounts of moisture creates micro-expansion pressure, accelerating the penetration of the liquid coating into the tiny gaps in the substrate. After the coating is fully cured, it forms an anchoring bond with the damp substrate, significantly improving coating adhesion. The polyurethane side reaction involved is shown below: 2R-NCO + H₂O → R-NH-CO-NH-R + CO₂↑ (side reaction) Simultaneously, the generated carbon dioxide gas can react promptly with the active substances in the inorganic powder, preventing quality problems such as coating blistering and foaming. Taking calcium hydroxide in the inorganic powder as an example, it can act as a carbon dioxide absorbent, eliminating the influence of polyurethane side reactions on the coating, and providing an alkaline environment to promote the main polyurethane reaction. The calcium carbonate generated by the reaction can also fill the pores in the coating, further enhancing the coating's density. Moreover, the hydroxyl groups (-OH) on the surface of calcium hydroxide can react with isocyanate groups (-NCO) to form chemical bonds, enhancing the bonding at the organic-inorganic interface. The main reaction formula involving calcium hydroxide is shown below: Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O (Main reaction of calcium hydroxide) In the organic-inorganic interpenetrating network (IPN) structure, the inorganic network is an inorganic hydration product network formed by the hydration reaction of inorganic powders such as silicate cement and active powder.

[0026] The hydration reaction of silicate cement components occurs simultaneously with the polyurethane reaction. Taking tricalcium silicate (C3S), dicalcium silicate (C2S), and tricalcium aluminate (C3A) as examples, as shown below, after hydration, tricalcium silicate and dicalcium silicate generate hydrated calcium silicate (CSH) gel and calcium hydroxide (CH) crystals, while tricalcium aluminate generates ettringite crystals after hydration.

[0027] 2C3S + 6H2O → C3S2H3 + 3Ca(OH)2 (Hydration reaction of tricalcium silicate (C3S)) 2C2S + 4H2O → C3S2H3 + Ca(OH)2 (Hydration reaction of dicalcium silicate (C2S)) The calcium silicate hydrate (CSH) gel, calcium hydroxide (CH) crystals, and ettringite crystals generated by the hydration reaction can be used to construct the inorganic strength framework of the coating, achieve adhesion between different components of the substrate, fill pores and bridge cracks, and provide a highly alkaline environment to catalyze the polyurethane reaction, accelerating the initial performance establishment of the coating. At the same time, it can also combine with polyurethane through hydrogen bonding, ion pairing and covalent bonding to form an organic-inorganic interpenetrating network.

[0028] Based on this, activated silica fume (microsilica powder) is used as the active powder, enabling a secondary hydration reaction. This process consumes the weak phase of cement hydration products, generating a high-strength gel. This further enhances the overall strength of the organic-inorganic composite coating and fills the internal voids, resulting in a denser coating. This strengthens the coating's physical and mechanical properties, improves its impermeability and chemical resistance. The secondary hydration reaction formula is shown below: SiO2 (active) + Ca(OH)2 → CSH gel (secondary hydration reaction) In addition, the calcium hydroxide in the above-mentioned inorganic powder can provide the core surface and active calcium ions, and can also promote the formation of CSH gel and calcium hydroxide crystals.

[0029] In component A above, the matrix resin, namely the bio-based hydroxyl resin, uses castor oil bio-based polyol, which combines the water resistance of polyether polyols and the strength of polyester polyols. Its preferred mass fraction is 80-85 parts, with a renewable material content between 65-80%, a hydroxyl content of 4%-10%, and a functionality of 3.0-3.5. For example, BASF's Sovermol® 805AP and Sovermol® 750 can be blended as matrix resins. BASF's Sovermol® 805AP has a hydroxyl content of 5.2% and a functionality of 3.5, while BASF's Sovermol® 750 has a hydroxyl content of 9.5% and a functionality of 3.0. The blending ratio of the two is set between 1:(1-3). Based on its high renewable material content, this bio-based hydroxyl resin can reduce the carbon footprint and fossil resource dependence of coating products, making it consistent with the green product route of low carbon emissions, low toxicity, and high sustainability.

[0030] The preferred mass fraction of the bio-based diluent is 6-8 parts, which is a fatty acid ester (e.g., BASF's Sovermol® 1058), tributyl citrate (especially acetylated tributyl citrate), or a mixture of fatty acid ester and tributyl citrate, with a renewable material content of 95-100%, which can adjust the viscosity of the system and achieve a coating effect with almost no VOC emissions when combined with bio-based hydroxyl resin.

[0031] The additives include 0.3-0.8 parts of dispersant, 0.3-0.7 parts of defoamer, 0.7-1.5 parts of rheology modifier, 0.2-1 parts of antioxidant, 0.2-0.5 parts of ultraviolet absorber, and 0.3-0.8 parts of adhesion promoter.

[0032] Dispersants can uniformly disperse inorganic powders and fillers in a system, reduce system viscosity, prevent particle agglomeration, and ensure the workability of the coating and the uniformity and density of the cured coating. Carboxylate dispersants, polyurethane dispersants, or mixtures thereof are preferred. Carboxylate dispersants are modified polymeric carboxylate dispersants, such as BASF's EFKA-5065, while polyurethane dispersants are modified polymeric polyurethane dispersants, such as BASF's EFKA®4010.

[0033] Defoamers can suppress the bubbles generated by the reaction of isocyanates and water, prevent defects such as pinholes and pores in the coating, and ensure the density and anti-corrosion effect of the coating. Organosilicon defoamers are preferred, especially polysiloxane defoamers containing hydrophobic particles, such as Deqian Hemings' Defom 6800.

[0034] The rheology modifier includes a first rheology modifier and a second rheology modifier. The first rheology modifier is present in a mass fraction of 0.5-1 parts, and the second rheology modifier is present in a mass fraction of 0.2-0.5 parts. The combination of these two inorganic powders enables the coating to possess excellent low-shear thixotropy, allowing for the application of thick films without sagging in a single coat. A single thick coat can even exceed 1000 μm, resulting in a good coating appearance. This helps reduce the number of coats and the construction period, meeting the objective requirements of short construction windows for the maintenance of marine engineering facilities.

[0035] In this embodiment, the first rheology modifier is a powdered rheology modifier, such as organically modified bentonite, hydrophobically modified fumed silica, or a mixture thereof, preferably hydrophobically modified fumed silica, such as Evonik Degussa AEROSIL R812S. The second rheology modifier is a polyamide wax paste, a polyethylene wax paste, or a mixture thereof, preferably a polyethylene wax paste, such as DeuRheo201P organic anti-settling agent from Deqian Hemings.

[0036] Antioxidants include hindered phenolic antioxidants and phosphite antioxidants. The mass fraction of hindered phenolic antioxidants is 0.1-0.5 parts, and the mass fraction of phosphite antioxidants is 0.1-0.5 parts. When used in combination, they can effectively inhibit the oxidative degradation of organic components in marine environments and improve the weather resistance and long-term stability of the coating.

[0037] In this formulation, hindered phenolic antioxidants are the primary antioxidants, with antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) being preferred, and phosphite antioxidants are the secondary antioxidants, with antioxidant 168 (tris(2,4-di-tert-butylphenyl)phosphite) being preferred. The mass ratio of hindered phenolic antioxidants to phosphite antioxidants is set between (1-2):1.

[0038] Ultraviolet absorbers can effectively absorb ultraviolet light, inhibit the aging and degradation of coatings caused by ultraviolet radiation, and improve the weather resistance and service life of coatings. Benzophenone-based ultraviolet absorbers or benzotriazole-based ultraviolet absorbers, such as ultraviolet absorber UV-326, are preferred.

[0039] Adhesion promoters can effectively improve the bonding strength between the coating and the concrete substrate, and at the same time enhance the interfacial bonding force between the organic and inorganic phases, making the coating less prone to peeling and falling off. They are made of silane coupling agents or titanate ester adhesion promoters, preferably vinyl silane coupling agents such as A-172, or epoxy silane coupling agents such as KH-560 and Z-6040.

[0040] The functional filler is preferably present in a mass fraction of 8-9 parts. It is made of molecular sieve activated powder, which can adsorb trace amounts of moisture in the system and inhibit polyurethane foaming side reactions, ensuring a dense and stable coating. It can also improve the storage stability and application adaptability of the coating. Preferably, the molecular sieve activated powder is type 5A, with a particle size of 2-4 μm and a pH value of 9-11.

[0041] In component B, the isocyanate includes aromatic isocyanate and aliphatic isocyanate. The aromatic isocyanate is the main curing agent, comprising 75-95 parts by weight, preferably 80-85 parts, with a functionality of 2.2-2.7; the aliphatic isocyanate is the auxiliary curing agent, comprising 5-25 parts by weight, preferably 15-20 parts. Correspondingly, the functionality of the castor oil bio-based polyol is set to 3.0-3.5, and the isocyanate index of the coating is adjusted to 1-1.6, i.e., the R value is set between 1-1.6, preferably 1.15-1.25.

[0042] By combining aromatic and aliphatic isocyanates and adjusting the functionality and isocyanate index of the coating, the reaction rate can be flexibly controlled. This allows for maximizing the overall reaction rate of the paint without affecting application, thereby improving the initial performance of the coating. The curing times of the resulting bio-based polyurethane anticorrosive coatings under different temperature conditions are shown in Table 1 below.

[0043] Table 1

[0044] Note: The times in Table 1 are for reference only. In actual application, they will be affected by changes in environmental and substrate conditions (especially temperature and relative humidity).

[0045] In this embodiment, the aromatic isocyanate is preferably a modified polymeric MDI, such as Huntsman's SUPRASEC® 2496, with an NCO% content between 30% and 33%, preferably 31.3%. The aliphatic isocyanate is an IPDI-TMP adduct, an HDI trimer, or a mixture thereof, preferably an HDI trimer, such as Wanhua Chemical's HT-600 or BASF's HI100, which can introduce isocyanurate rings to improve the coating's heat resistance and dimensional stability. The NCO% content of the HDI trimer is set at 22.5%-23.5%.

[0046] In addition, component B also includes a stabilizer to further improve the storage stability of the coating and the density of the cured coating. The stabilizer is 0.5-1 parts by weight and is a monofunctional isocyanate, triethyl orthoformate or a mixture thereof, preferably a highly reactive, low-viscosity monofunctional isocyanate, especially p-toluenesulfonate isocyanate (e.g., Bayer's Additive TI).

[0047] In component C, white silicate cement is preferred, as it is white in color and stable in tone, which can prevent the coating from yellowing. It also possesses hydration activity and mechanical strength, balancing decorative and performance properties. Its preferred mass fraction is 40-42 parts. In this embodiment, the silicate cement used is 42.5 grade white silicate cement, 52.5 grade white silicate cement, or a mixture thereof.

[0048] The calcium hydroxide is 400-mesh food-grade calcium hydroxide, 800-mesh food-grade calcium hydroxide, or a mixture thereof, preferably 800-mesh food-grade calcium hydroxide, with a calcium hydroxide content of ≥98%. The preferred mass fraction of calcium hydroxide is 6-8 parts.

[0049] The active powder, also known as the microsilica powder mentioned above, is a microsilica powder with high pozzolanic reactivity, wherein the content of amorphous silica (SiO2) is ≥85%. The preferred mass fraction of the active powder is 5-6 parts.

[0050] Pigments and fillers include fillers, titanium dioxide, and colorants. Fillers, such as barium sulfate, quartz powder, or mixtures thereof, improve the workability and hardness of the coating, reduce shrinkage cracking, and enhance density, abrasion resistance, and resistance to chemical corrosion. The filler comprises 30-40 parts by weight, preferably 35-38 parts, and is preferably 400-mesh quartz powder with a crystalline silica (SiO2) content ≥95%. Titanium dioxide improves the whiteness and hiding power of the coating, and comprises 8-15 parts by weight, preferably rutile titanium dioxide coated with aluminum or zirconium. Colorants comprise 0-5 parts by weight, preferably inorganic, easily dispersible colorants, such as Bayer Iron Oxide Red 4110.

[0051] In summary, through special formulation design and reasonable component matching, this bio-based polyurethane anticorrosion coating can form an organic-inorganic interpenetrating network coating structure. It possesses the excellent chemical resistance, abrasion resistance, impermeability, and strong impact resistance of polyurethane coatings, while also exhibiting the excellent physical properties (high strength), wide interfacial applicability, and excellent durability of inorganic materials. Furthermore, it is easy to apply, adaptable to various substrates, and can quickly cure after application to establish the initial coating properties. It overcomes the difficulties in environmental factors, performance requirements, and construction conditions in the maintenance of anticorrosion systems for marine engineering facilities, and has been applied in the field of anticorrosion and repair of marine engineering facilities.

[0052] Example 2 Based on the formulation of the first embodiment above, the present invention also provides a method for preparing the above-mentioned bio-based polyurethane anticorrosive coating. This method mainly includes the following steps: S1. Prepare components A, B, and C in advance. S2. Mix components A, B, and C using a low-speed electric stirrer (impeller type or paddle type) or other stirring tools. During mixing, the stirring blade should be completely immersed in the material to prevent air bubbles from being entrapped during the stirring process. Before mixing, first stir component A thoroughly, then add all of component B to component A, and mix components A and B evenly at a stirring speed of 300 - 400 revolutions per minute for about 30 - 60 seconds. After that, gradually add component C and stir thoroughly for at least 2 minutes to make component C evenly dispersed, and the above-mentioned bio-based polyurethane anticorrosive coating can be obtained.

[0053] The specific preparation steps of the above-mentioned component A are as follows: a1. Take a part of the bio-based hydroxyl resin and all of the bio-based diluent and add them to a reaction kettle, and carry out stirring and mixing. During the mixing process, first add the dispersant and defoamer to the reaction kettle and stir and disperse them at a speed of 300 - 400 revolutions per minute, then slowly add the rheology aid to the reaction kettle and carry out high-speed dispersion at a speed of 800 - 1000 revolutions per minute. After uniform dispersion, a viscous liquid-like first mixture can be obtained. The first mixture is tested by film formation and has no obvious particulate matter.

[0054] a2. Slowly add the functional filler, antioxidant, and ultraviolet absorber to the first mixture and carry out stirring and mixing, and gradually increase the speed to 1000 - 1200 revolutions per minute for high-speed dispersion as the consistency of the slurry increases. The dispersion time is about 20 minutes. After uniform dispersion, a second mixture is obtained. The fineness of the second mixture is detected to be ≤50μm to be qualified.

[0055] a3. Slowly add the remaining bio-based hydroxyl resin to the second mixture, and gradually decrease the speed to 500 - 700 revolutions per minute as the consistency of the slurry decreases. After stirring for about 3 minutes, a third mixture that is thoroughly mixed is obtained.

[0056] a4. Gradually decrease the speed to 400 - 500 revolutions per minute, and gradually heat the third mixture to 110 - 120°C. Then start the vacuum system and carry out dehydration treatment on the third mixture under vacuum conditions, maintaining a vacuum degree of -0.095 MPa. The dehydration treatment time is about 120 minutes. After dehydration, the moisture content is measured using the Karl Fischer method to ensure that the moisture content < 0.05%.

[0057] a5. Cool the dehydrated third mixture to 60 - 80°C, and then add the adhesion promoter and stir evenly to obtain component A.

[0058] The specific steps for preparing component B are as follows: Nitrogen gas is introduced into a sealed mixing vessel. After gradually replacing the air in the vessel, aromatic isocyanate, aliphatic isocyanate and stabilizer are slowly added to the vessel in a nitrogen environment. The three are then thoroughly mixed at a speed of 400-600 rpm. After mixing, component B is obtained.

[0059] The specific steps for preparing component C are as follows: c1. Turn on the drying equipment to pre-dry the calcium hydroxide, active powder, and pigments and fillers required for production, and set them aside for later use. The drying temperature is approximately 100℃, and the moisture content after drying is below 0.5%.

[0060] c2. Turn on the dry powder mixing equipment and slowly add silicate cement, calcium hydroxide, active powder, and pigments and fillers to the equipment in sequence. Stir and mix for at least 40 minutes until uniformly mixed to obtain a dry powder material with uniform color and fine texture, i.e., component C. The obtained component C can be packaged in a sealed polyethylene (PE) plastic bag for moisture protection.

[0061] The pot life of the prepared bio-based polyurethane anticorrosive coating at different temperatures is shown in Table 2 below.

[0062] Table 2

[0063] The prepared bio-based polyurethane anticorrosive coating can be mixed with graded quartz sand or other aggregates to further prepare repair mortar. The pot life of this repair mortar is the same as in Table 2 above, used to repair defects on the substrate surface, such as depressions and holes. The mass ratio of the bio-based polyurethane anticorrosive coating to the subsequently added aggregate is 1:(1-1.5), and the preferred configuration is shown in Table 3 below.

[0064] Table 3

[0065] Example 3 Based on the above embodiments one and two, the present invention also provides the application of the above-mentioned bio-based polyurethane anticorrosive coating in marine engineering, especially for the repair of marine engineering facilities.

[0066] Taking the repair of marine engineering facilities as an example, the construction operation of the above-mentioned bio-based polyurethane anti-corrosion coatings and repair coatings will be further explained.

[0067] Before applying repair mortar, all contaminants on the substrate must be thoroughly removed, including dust, existing paint layers, weathering products, oil stains, impurities, marine organism residues, or other substances that may affect adhesion. Furthermore, the substrate should be sanded or blasted using appropriate mechanical methods and thoroughly cleaned to ensure cleanliness.

[0068] Before application, there should be no standing water on the substrate. Therefore, in areas such as splash zones and tidal zones of marine engineering facilities, construction should be carried out during low tide. After cleaning the substrate, physical methods such as wiping or absorbing standing water with a dry cloth, sponge, or absorbent material should be used. It is best to use a blower or heat gun to accelerate the evaporation of moisture from the substrate until there is no standing water. However, if the substrate is damp but without standing water, construction can proceed directly.

[0069] Next, apply the repair mortar to the defective area of ​​the substrate using a scraper, and scrape back and forth to make the defective area flush with the substrate. A single application can achieve a thickness of 5mm. After repair, a smooth, dense substrate with excellent adhesion will be formed, allowing for the application of bio-based polyurethane anti-corrosion coatings.

[0070] When applying bio-based polyurethane anti-corrosion coating, use tools such as short-bristled rollers and brushes to apply the coating to the surface that needs to be renovated and is free of standing water. Apply the coating evenly and ensure that the coating is completely wetted and covers the surface to be repaired. The thickness of a single application can reach 500-1000μm.

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific preparation examples.

[0072] Preparation Example 1 Based on the above Examples 1 and 2, a bio-based polyurethane anticorrosive coating was prepared. The coating has an isocyanate index of 1.2, and the mass ratio of component A, component B and component C in the coating is 1:0.6:1.1.

[0073] The hydroxyl content of component A is 0.352 mol / OH- (100 g), and the specific composition of component A is shown in Table 4 below.

[0074] Table 4

[0075] The NCO% content of component B is 30%, and its specific formulation is shown in Table 5 below.

[0076] Table 5

[0077] The specific formulation of component C is shown in Table 6 below.

[0078] Table 6

[0079] Preparation Example 2 Based on the preparation example 1 above, graded quartz sand was added to prepare the fine sand repair mortar shown in Table 3 above. In this fine sand repair mortar, the mass ratio of bio-based polyurethane anti-corrosion coating, 20-30 mesh quartz sand, and 40-80 mesh quartz sand is 1:0.35:0.65.

[0080] Based on the technical requirements and test methods for Im2 in JTJ 275-2000 "Technical Specification for Corrosion Protection of Concrete Structures in Harbor Engineering" and JT / T 695-2007 "Technical Conditions for Corrosion Protection Coating of Concrete Bridge Structures", the relevant anti-corrosion performance of Preparation Example 1 and Preparation Example 2 was tested. The test results are shown in Table 7 below: Table 7

[0081] As can be seen from Table 7 above, the bio-based polyurethane anticorrosive coating provided by this invention has excellent corrosion resistance properties, and its chemical resistance, water resistance, alkali resistance and salt water resistance are all higher than the standard requirements.

[0082] The chloride ion penetration resistance test showed that the coating film was basically undetectable after 30 days of testing, while the repair mortar made with added quartz sand showed trace amounts of chloride ion penetration. This indicates that in the organic-inorganic composite system, when the organic network content is higher, the overall system has higher density and better impermeability.

[0083] The adhesion test results show that the above-mentioned bio-based polyurethane anti-corrosion coatings and repair mortars have very good dry and wet adhesion on both dry and wet concrete surfaces. The test results are far higher than the strength of the concrete mortar specimens, thus causing the mortar specimens to fail.

[0084] In addition, due to the need for rapid drying and curing, the isocyanates in the system are mainly aromatic isocyanates, which will yellow to some extent under ultraviolet light. However, a certain amount of aliphatic isocyanate (HDI trimer) is added to the formula to improve yellowing resistance. At the same time, antioxidants and ultraviolet absorbers are added to further improve weather resistance. Therefore, after 1000h of weather resistance testing, the color difference ΔE of the coating film is 1.0-1.6, which is far better than the standard level 2 (ΔE=3.1-6.0) technical requirements.

[0085] The performance of Preparation Example 1 and Preparation Example 2 was tested according to the test methods in JC / T 2381-2016 "Repair Mortar" (for fast-setting types) and JC / T 2327-2015 "Waterborne Polyurethane Flooring". The specific test results are shown in Table 8 below: Table 8

[0086] As can be seen from Table 8 above, the bio-based polyurethane anticorrosive coating provided by this invention exhibits excellent physical properties, with outstanding initial strength and adhesion. Its compressive strength after 6 hours already meets the usage requirements, and its tensile adhesion strength after 24 hours far exceeds the technical requirements. Thanks to its rapid curing performance, especially the initial performance of the coating film, this coating can overcome the problem of short construction windows in the splash zone of marine engineering facilities, meeting the requirements for rapid curing and initial performance in the repair of marine engineering facilities.

[0087] The flexural strength test of the old and new mortar substrates shows that the bio-based polyurethane anti-corrosion coating and its repair mortar provided by this invention have excellent adhesion to the old concrete substrate and high physical properties, which caused the old mortar test block to be destroyed. It can provide a suitable product for the repair and renovation of the anti-corrosion system of marine engineering facilities.

[0088] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail to the invention without departing from the spirit and scope of the invention as defined in the appended claims are within the scope of protection of the invention.

Claims

1. A bio-based polyurethane anticorrosive coating, characterized in that: It includes component A, component B and component C, wherein the mass ratio of component A, component B and component C is 1:(0.4-0.6):(1-1.5); By weight, component A comprises 70-90 parts of bio-based hydroxyl resin, 5-10 parts of bio-based diluent, 2-5.3 parts of additives, and 6-12 parts of functional filler; component B comprises isocyanate; and by weight, component C comprises 35-55 parts of silicate cement, 5-10 parts of calcium hydroxide, 3-8 parts of active powder, and 38-50 parts of pigments and fillers.

2. The bio-based polyurethane anticorrosive coating as described in claim 1, characterized in that: The isocyanate includes aromatic isocyanate and aliphatic isocyanate, wherein the aromatic isocyanate has a mass fraction of 75-95 and the aliphatic isocyanate has a mass fraction of 5-25; the coating has an isocyanate index of 1-1.6, the aromatic isocyanate has a functionality of 2.2-2.7, and the castor oil bio-based polyol has a functionality of 3.0-3.

5.

3. The bio-based polyurethane anticorrosive coating as described in claim 2, characterized in that: The aromatic isocyanate is polymeric MDI; the aliphatic isocyanate is IPDI-TMP adduct, HDI trimer or a mixture thereof; the B component also includes a stabilizer, which is a monofunctional isocyanate, triethyl orthoformate or a mixture thereof, and the stabilizer is 0.5-1 parts by mass.

4. The bio-based polyurethane anticorrosive coating as described in claim 1, characterized in that: The bio-based hydroxyl resin is castor oil bio-based polyol; the bio-based diluent is fatty acid ester, tributyl citrate, or a mixture thereof; the functional filler is molecular sieve activated powder; the activated powder is microsilica powder; the pigments and fillers include filler, titanium dioxide, and color powder, wherein the filler is barium sulfate, quartz powder, or a mixture thereof, the filler has a mass fraction of 30-40 parts, the titanium dioxide has a mass fraction of 8-15 parts, and the color powder has a mass fraction of 0-5 parts.

5. The bio-based polyurethane anticorrosive coating as described in claim 1, characterized in that: The additives include 0.3-0.8 parts of dispersant, 0.3-0.7 parts of defoamer, 0.7-1.5 parts of rheology modifier, 0.2-1 parts of antioxidant, 0.2-0.5 parts of ultraviolet absorber, and 0.3-0.8 parts of adhesion promoter.

6. The bio-based polyurethane anticorrosive coating as described in claim 5, characterized in that: The rheology modifier includes a first rheology modifier and a second rheology modifier. The first rheology modifier is organically modified bentonite, hydrophobically modified fumed silica, or a mixture thereof. The second rheology modifier is polyamide wax paste, polyethylene wax paste, or a mixture thereof. The mass fraction of the first rheology modifier is 0.5-1 parts, and the mass fraction of the second rheology modifier is 0.2-0.5 parts.

7. The bio-based polyurethane anticorrosive coating as described in claim 5, characterized in that: The antioxidants include hindered phenolic antioxidants and phosphite antioxidants, wherein the hindered phenolic antioxidants are present in a mass fraction of 0.1-0.5 parts, the phosphite antioxidants are present in a mass fraction of 0.1-0.5 parts, and the mass ratio of the hindered phenolic antioxidants to the phosphite antioxidants is (1-2):

1.

8. The bio-based polyurethane anticorrosive coating as described in claim 5, characterized in that: The dispersant is a carboxylate dispersant, a polyurethane dispersant, or a mixture thereof; the defoamer is an organosilicon defoamer; the ultraviolet absorber is a benzophenone ultraviolet absorber or a benzotriazole ultraviolet absorber; and the adhesion promoter is a silane coupling agent or a titanate adhesion promoter.

9. The method for preparing the bio-based polyurethane anticorrosive coating according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Prepare components A, B, and C in advance; The preparation steps of component A are as follows: a1. Take a portion of bio-based hydroxyl resin and mix it evenly with a bio-based diluent. During the mixing process, add a dispersant, defoamer, and rheology modifier. After mixing evenly, obtain a first mixture; a2. Slowly add functional fillers, antioxidants, and ultraviolet absorbers to the first mixture and gradually increase the rotation speed for high-speed dispersion. After even dispersion, obtain a second mixture; a3. Slowly add the remaining bio-based hydroxyl resin to the second mixture and gradually decrease the rotation speed for mixing evenly, obtain a third mixture; a4. Gradually decrease the rotation speed and heat the third mixture to 110-120℃, then dehydrate the third mixture under vacuum conditions; a5. Cool the dehydrated third mixture to 60-80℃, add an adhesion promoter, and stir evenly to obtain component A; The preparation steps of component B are as follows: aromatic isocyanate, aliphatic isocyanate and stabilizer are mixed in a nitrogen atmosphere, and the mixture is thoroughly mixed to obtain component B. The preparation steps of component C are as follows: c1. Pre-drying calcium hydroxide, active powder, and pigments and fillers; c2. Mix silicate cement, calcium hydroxide, active powder, and pigments and fillers evenly to obtain component C; S2. Stir component A thoroughly, then add component B to component A and mix evenly. Then gradually add component C to disperse it evenly, thus obtaining the bio-based polyurethane anti-corrosion coating.

10. The application of the bio-based polyurethane anticorrosive coating as described in any one of claims 1-8 in marine engineering.

Images