Solvent-free environment-friendly coating and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a solvent-free environment-friendly coating and a preparation method thereof, the solvent-free environment-friendly coating comprises the following components by mass: 30-60 parts of a reactive oligomer, 10-30 parts of a toughening modified resin, 20-40 parts of a basic epoxy resin, 15-35 parts of a multi-stage synergistic curing agent system, and 0.5-3 parts of an interface enhanced coupling agent, the water-based paint comprises the following components in parts by weight: 5-15 parts of inorganic nano reinforcing filler, 0.5-2 parts of rheology control agent, 0.1-0.5 part of defoaming agent, 0.2-1 part of dispersing agent and 0-30 parts of pigment and / or functional filler. The reactive oligomer with low-viscosity and high-activity functional groups is used as a core reactive diluent, the low-viscosity characteristic of the reactive oligomer can remarkably reduce the overall viscosity of a coating system, a volatile diluent containing harmful substances such as benzene series does not need to be added, meanwhile, dependence on special equipment such as high-temperature and high-pressure spraying is avoided, and the cost is reduced. The construction flowability of the solventless coating is effectively improved, and the application scene is widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a solvent-free environment-friendly coating and a preparation method thereof. BACKGROUND

[0002] With the improvement of global environmental awareness and the tightening of regulations, the coating industry is turning to environmentally friendly technology. Traditional coatings release a large amount of volatile organic compounds (VOCs) throughout the process, polluting the environment and harming health, so the industry has formed two major trends of water-based and solvent-free development. Water-based coatings use water as the main dispersion medium, greatly reducing the use of organic solvents and VOCs emissions, and are more environmentally friendly than traditional solvent-based coatings. They are widely used in specific fields. However, in actual application, a small amount of functional additives need to be added to ensure performance, and chemicals may be left over during production, and fillers and pigments may contain heavy metals, making the whole life cycle still have environmental challenges and potential risks. Solvent-free coatings have a solid content close to 100%, and almost no solvent is volatilized during construction and curing, with very low VOCs content, making them an ideal environmentally friendly solution with great potential in corrosion protection and flooring. However, the high solid content leads to high viscosity, and existing viscosity reduction solutions have problems: adding diluents containing harmful substances such as benzene series will weaken the environmental advantages and harm health; relying on special equipment such as high-temperature and high-pressure spraying increases construction costs and technical barriers, limiting application scenarios, especially not suitable for small construction sites or places with harsh construction conditions. With the deepening of technology application and the industry's increasing demand for coating performance, the inherent characteristics of existing solvent-free coatings (especially solvent-free epoxy coatings) make them have deep limitations when balancing multi-dimensional performance. The high solid content of solvent-free systems achieves low VOCs emissions, but leads to high viscosity, making it difficult to reduce viscosity during construction. This inherent contradiction makes it only suitable for thick coating construction. Thick coatings can provide a higher protective layer, but the cured coating is highly brittle, with insufficient impact resistance, crack resistance, and anti-peeling properties, and is prone to cracking and peeling when subjected to mechanical impact, substrate deformation, or dramatic temperature changes, compromising the integrity of the protective layer. In addition, the adhesion between the coating and the substrate is poor due to the high stiffness of the material and insufficient interface wetting. These shortcomings result in poor corrosion resistance and durability of solvent-free coatings in harsh corrosive environments or long-term service scenarios, failing to fully utilize the high-performance protective properties. Therefore, the existing solvent-free coating technology has an inherent contradiction between pursuing environmental friendliness and the comprehensive mechanical properties of the coating, the ability to durably bond with the substrate, and the adaptability to a wide range of construction. SUMMARY

[0003] (I) Technical problems solved To solve the problems of the prior art, the present application provides a solvent-free environmentally friendly coating and a preparation method thereof, which solves the problem of "poor use effect" in the background art.

[0004] (II) Technical Solution To achieve the above object, the present application is implemented by the following technical solution: A solvent-free environment-friendly coating, comprising the following components in mass fraction: 30-60 parts of a reactive oligomer, 10-30 parts of a toughening modified resin, 20-40 parts of a base epoxy resin, 15-35 parts of a multi-stage synergistic curing agent system, 0.5-3 parts of an interface-enhanced coupling agent, 5-15 parts of inorganic nano-enhanced fillers, 0.5-2 parts of a rheological control agent, 0.1-0.5 parts of a defoaming agent, 0.2-1 parts of a dispersing agent, and 0-30 parts of pigments and / or functional fillers.

[0005] Preferably, the reactive oligomer is a polyol polyether type epoxy oligomer with at least three epoxy groups, with an epoxy equivalent weight of 90-150 g / eq and a viscosity at 25℃ of .

[0006] Preferably, the toughening modified resin is a polyurethane modified epoxy resin or a core-shell structure elastomer modified epoxy resin, the glass transition temperature of the polyurethane modified epoxy resin is -30-0℃, and the epoxy equivalent weight is 400-700 g / eq, the average particle size of the elastomer particles in the core-shell structure elastomer modified epoxy resin is 50-200 nm, and the glass transition temperature is lower than -40℃.

[0007] Preferably, the base epoxy resin is a bisphenol A type epoxy resin or a bisphenol F type epoxy resin, with an epoxy equivalent weight of 170-250 g / eq and a viscosity at 25℃ of .

[0008] Preferably, the multi-stage synergistic curing agent system comprises 10-25 parts of a primary curing agent and 5-10 parts of a secondary curing agent, the primary curing agent is an aliphatic amine modified epoxy resin curing agent, with an amine value of 200-400 mgKOH / g, a hydrogen active equivalent weight of 50-120 g / eq, and a viscosity at 25℃ of less than , and the secondary curing agent is a latent curing agent selected from imidazole derivatives or hindered amine compounds.

[0009] Preferably, the interface-enhanced coupling agent is an organosilane coupling agent containing epoxy groups or amine groups, the inorganic nano-enhanced fillers are nano-silica or nano-alumina with surface organic modification, and the average particle size is 10-50 nm.

[0010] Preferably, the rheology control agent is a thixotropic agent based on polyamide wax or hydrogenated castor oil derivative, the specific surface area is 100 m² / g to 300 m² / g, the defoaming agent is a silicone or polyether nonionic defoaming agent, and the surface tension is less than 25 mN / m.

[0011] Preferably, the dispersant is a high molecular polymer dispersant, the pigment is an inorganic pigment or an organic pigment, the average particle size is 0.1 μm to 5 μm, and the functional filler is selected from precipitated barium sulfate, talc powder, mica powder or glass microbeads, and the average particle size is 1 μm to 20 μm.

[0012] Preferably, a preparation method of a solvent-free environmentally friendly coating comprises the following steps: S1: Pre-dispersion preparation, adding base epoxy resin, reactive oligomer, toughening modified resin, interfacial enhancement type coupling agent, dispersant, defoaming agent and pigment and / or functional filler in a batching kettle, dispersing at 1500 rpm to 3000 rpm for 30 minutes to 60 minutes, controlling the temperature at 30℃ to 45℃, and making the fineness reach below 20 μm; S2: Nano filler compounding, adding inorganic nano reinforcing filler to the mixture of step one, dispersing at 1000 rpm to 2000 rpm for 15 minutes to 30 minutes; S3: Rheology control agent activation, adding rheology control agent, stirring at 500 rpm to 1000 rpm for 10 minutes to 20 minutes, and heating to 50℃ to 60℃, and then stirring at 100 rpm to 300 rpm for 10 minutes; S4: Defoaming, defoaming at a vacuum degree of -0.08 MPa to -0.09 MPa for 15 minutes to 30 minutes; S5: Mixing of curing agent components, uniformly premixing the primary curing agent and the secondary curing agent according to the proportion; S6: Metering, dispensing and packaging, metering and dispensing the coating base and the curing agent system respectively and sealing.

[0013] Preferably, a high-speed disperser is used in S1, and a rotating speed control system and a temperature monitoring function are configured, and the dispersing equipment in S2 is a high-shear planetary stirrer or a high-speed disperser with a special structure dispersing disc.

[0014] (Three) beneficial effects The application provides a solvent-free environmentally friendly coating and a preparation method thereof. (1) The present application uses a reactive oligomer with low viscosity and high active functional groups as a core reactive diluent, which can significantly reduce the overall viscosity of the coating system, without adding volatile diluents containing harmful substances such as benzene series, and avoiding the dependence on special equipment such as high temperature and high pressure spraying, effectively improving the flowability of solvent-free coatings, widening the application scenarios, especially suitable for small construction sites or harsh construction conditions.

[0015] (2) The present application uses the synergistic effect of toughening modified resin and inorganic nano-enhanced filler, and the high crosslinking density network structure formed by the multi-level synergistic curing agent system, to significantly improve the toughness, impact resistance, crack resistance and bending toughness of the coating film, overcome the defects of high brittleness and easy cracking of existing solvent-free coatings after thick coating and curing, and enhance the protection integrity.

[0016] (3) The present application introduces an interfacial enhancement type coupling agent, which improves the adhesion of the coating film to the substrate by reacting the organic functional groups with the resin matrix and the inorganic functional groups with the substrate surface, and at the same time, the deep crosslinking and curing effect brought by the multi-level synergistic curing agent system improves the chemical resistance, salt spray resistance and long-term durability of the coating, solves the problem of poor adhesion and insufficient protection performance in harsh environments caused by the high material rigidity and insufficient interface wetting of existing solvent-free coatings, and realizes the balance between environmental protection and comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of the components of the solvent-free environmental protection type coating of the present application; Figure 2 is a schematic diagram of the preparation method flow of the solvent-free environmental protection type coating of the present application. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0019] Please refer to Figure 1 - Figure 2The present application provides a solvent-free environmentally friendly coating, which comprises the following components in mass fraction: 30-60 parts of a reactive oligomer with low viscosity and high active functional groups; 10-30 parts of a toughening modified resin with a flexible skeleton; 20-40 parts of a base epoxy resin; 15-35 parts of a multi-stage synergistic curing agent system; 0.5-3 parts of an interfacial enhancement type coupling agent; 5-15 parts of inorganic nano-enhanced fillers; 0.5-2 parts of a rheological control agent; 0.1-0.5 parts of a defoaming agent; 0.2-1 parts of a dispersing agent; and 0-30 parts of pigments and / or functional fillers. The reactive oligomer is a polyol polyether type epoxy oligomer with at least three epoxy groups, and the epoxy equivalent weight (EEW) of the reactive oligomer ranges from 90 g / eq to 150 g / eq, and the viscosity at 25℃ is controlled between 100 mPa·s and 800 mPa·s. The polyol polyether type epoxy oligomer can be prepared by etherification reaction of one or more polyols, such as pentaerythritol, glycerol or trimethylolpropane, with epichlorohydrin, followed by epoxidation reaction. This oligomer has a multi-functionality characteristic, which helps to form a network structure with high cross-linking density during curing. At the same time, its polyether skeleton structure endows the curing system with a certain flexibility. In the coating formulation, the reactive oligomer plays the role of a core reactive diluent. Its inherent low viscosity characteristic allows the overall viscosity of the coating system to be significantly reduced, thus avoiding the need for volatile organic solvents in traditional coatings. During the curing process of the coating, the reactive oligomer can fully participate in the cross-linking reaction and become a structural component of the coating film, so there is no VOCs emission during the entire process, which reflects its environmental characteristics.

[0020] The toughening modifier resin can be a polyurethane-modified epoxy resin or a core-shell structured elastomer-modified epoxy resin. When a polyurethane-modified epoxy resin is used, the preparation process involves the reaction of isocyanate with polyether polyol or polyester polyol to form a prepolymer, which is then introduced into the epoxy system by reacting with the hydroxyl or epoxy groups of the epoxy resin. The glass transition temperature (Tg) of the polyurethane-modified epoxy resin ranges from -30°C to 0°C, and the epoxy equivalent weight (EEW) ranges from 400 g / eq to 700 g / eq. The presence of polyurethane segments imparts excellent toughness and impact resistance to the cured coating film, helping to overcome the brittleness problem commonly encountered in traditional solvent-free epoxy coatings after curing. When a core-shell structured elastomer-modified epoxy resin is used, the average particle size of the elastomer particles is typically between 50 nm and 200 nm, and the glass transition temperature is less than -40°C. The elastomer particles are uniformly distributed in the epoxy resin matrix through in-situ polymerization or pre-dispersion. Specifically, the core-shell structured elastomer is typically composed of a cross-linked elastomer core (such as acrylate rubber) and a polymer shell (such as polymethyl methacrylate) that is compatible with and reactive with the epoxy resin. The core-shell structured elastomer can effectively absorb and disperse the energy generated by crack propagation during coating curing, thereby improving the anti-cracking performance and impact toughness of the coating film.

[0021] The base epoxy resin can be a bisphenol A-type epoxy resin or a bisphenol F-type epoxy resin. Its epoxy equivalent weight (EEW) ranges from 170 g / eq to 250 g / eq, and the viscosity at 25°C ranges from 5000 mPa·s to 15000 mPa·s. The base epoxy resin is the main film-forming material in the coating system, providing core support for the hardness, chemical resistance, and mechanical strength of the cured coating film. Through synergistic action with the reactive oligomer and toughening modifier resin, a composite resin matrix with both low viscosity characteristics and excellent performance is constructed.

[0022] The multi-stage synergistic curing agent system contains at least two curing agents with different reactivity to achieve precise control of the curing process of the coating. Specifically, the multi-stage synergistic curing agent system contains 10 to 25 parts of a primary curing agent and 5 to 10 parts of a secondary curing agent. The primary curing agent is an aliphatic amine modified epoxy resin curing agent with an amine value ranging from 200 mgKOH / g to 400 mgKOH / g, a hydrogen active equivalent weight (AHEW) ranging from 50 g / eq to 120 g / eq, and a viscosity lower than 1000 mPa·s at 25℃. The primary curing agent has high reactivity with epoxy groups, which can quickly initiate the preliminary curing reaction of the coating system at room temperature, making the coating film achieve surface dryness and form preliminary hardness rapidly, thus meeting the demand for fast leveling and preliminary consolidation of the coating in conventional construction. The secondary curing agent is a latent curing agent, which has low reactivity or does not react with epoxy resin at room temperature, but its reactivity can be activated under specific activation conditions, such as a temperature of 80℃ to 120℃, or in a specific humidity environment. The latent curing agent can be selected from imidazole derivatives, such as 2-methyl imidazole or 2-phenyl imidazole, or hindered amine compounds, such as ketimine or aldimine. When imidazole derivatives are selected, their addition amount is controlled to be 0.5% to 3% of the total mass of the epoxy component. When hindered amine compounds are selected, their amine value ranges from 150 mgKOH / g to 300 mgKOH / g. The introduction of the secondary curing agent enables the coating to further undergo deep crosslinking and curing through subsequent environmental conditions (such as temperature rising treatment or absorption of moisture in the air) after preliminary curing, thereby improving the final crosslinking density, hardness, chemical resistance, and corrosion resistance of the coating film. Especially in thick coating applications, this multi-stage curing mechanism can effectively avoid the problem of uneven internal and external curing, and help reduce the stress inside the coating. The design of the multi-stage synergistic curing agent system not only ensures that the coating has a suitable pot life and preliminary curing ability at room temperature during construction, but also guarantees excellent performance of the coating through the introduction of the latent secondary curing mechanism.

[0023] The interfacial enhancement type coupling agent is an organosilane coupling agent containing epoxy groups or amine groups, such as γ-glycidoxypropyltrimethoxysilane or N-β-aminoethyl-γ-aminopropyltrimethoxysilane. The addition amount of the coupling agent is 0.5% to 3% of the total mass of the coating. The coupling agent chemically reacts with the resin matrix through its organic functional groups, and forms covalent bonds or hydrogen bonds with the surface of the substrate (such as the hydroxyl groups on the surface of metal or concrete) through its inorganic functional groups (such as alkoxysilane groups), thereby significantly enhancing the adhesion between the coating film and the substrate, and improving the peel strength and water resistance of the coating film.

[0024] The inorganic nano-reinforcing filler is nano-silica or nano-alumina with surface organic modification, and the average particle size is between 10 nm and 50 nm. The addition amount of the filler is 5% to 15% of the total mass of the coating. The nano-filler can effectively improve the hardness, wear resistance, scratch resistance and impact toughness of the coating film through nano-scale complexation with the polymer matrix, without causing significant increase in the viscosity of the coating. In addition, the nano-filler also helps to inhibit the generation and expansion of micro-cracks in the coating film. The surface modification of the nano-filler aims to enhance its dispersion performance in the organic phase and improve the interfacial compatibility between the nano-filler and the resin matrix, for example, by chemical treatment of the surface of the nano-filler with a silane coupling agent.

[0025] The rheology control agent is a thixotropic agent based on polyamide wax or hydrogenated castor oil derivative, and the specific surface area is in the range of 100 m² / g to 300 m² / g. The addition amount of the rheology control agent is 0.5% to 2% of the total mass of the coating. Under the action of shear force, the rheology control agent can reduce the viscosity of the coating system, thereby facilitating the construction coating; when the shear force is removed, it can quickly restore the system viscosity, providing excellent anti-sagging performance and anti-settling performance, ensuring the uniformity of the coating thickness, and making it suitable for various construction methods.

[0026] The defoamer is an organic silicon or polyether non-ionic defoamer with a surface tension of less than 25 mN / m. The addition amount of the defoamer is 0.1% to 0.5% of the total mass of the coating. The defoamer can effectively eliminate the bubbles that may be generated during the production, storage and construction of the coating, thereby ensuring that the final coating film surface is flat and defect-free.

[0027] Further, the dispersant is a high molecular polymer dispersant that exhibits excellent wetting and dispersion performance in the organic system, and can effectively prevent the flocculation and settling of pigments and fillers. The addition amount of the dispersant is 0.2% to 1% of the total mass of the pigments and fillers. The dispersant stabilizes the pigment and filler particles through steric hindrance effect and charge repulsion effect, thereby ensuring the storage stability of the coating and the uniformity of the coating color after curing.

[0028] The pigments can be inorganic pigments such as titanium dioxide, red iron oxide or carbon black, or organic pigments. The average particle size of the pigments is between 0.1 μm and 5 μm, and does not contain harmful substances such as heavy metals. The functional fillers can be selected from precipitated barium sulfate, talc powder, mica powder or glass beads, and the average particle size is between 1 μm and 20 μm. The addition amount of the pigments and / or functional fillers is 0 to 30 parts of the total mass of the coating, which provides the required color, hiding power, enhances the mechanical properties of the coating film or reduces the production cost in specific applications.

[0029] Based on the above, the present application also provides a preparation method of a solvent-free environmentally friendly coating, which specifically comprises the following steps: Step one: Pre-dispersion preparation, in a batch kettle, the base epoxy resin, low viscosity functionalized reactive prepolymer, toughening modifier resin, interfacial reinforcing coupling agent, dispersant, defoamer, and the required pigments and / or functional fillers are added in sequence according to the preset formulation amount. Subsequently, a high-speed disperser is used to disperse at a speed of 1500 rpm to 3000 rpm, and the dispersion time is controlled at 30 minutes to 60 minutes. The dispersion process continues until the pigments and fillers are uniformly dispersed in the base material, and the fineness is ensured to be below 20 μm by a doctor blade fineness meter. During the entire dispersion process, the material temperature is accurately controlled by the jacket or internal coil outside the batch kettle, and the material temperature is maintained in the range of 30°C to 45°C, so as to effectively avoid local overheating caused by high-speed shearing. The high-speed disperser is equipped with an accurate speed control system and real-time temperature monitoring function to ensure accurate execution of process parameters.

[0030] Step two: Nano-filler compounding, the inorganic nano-reinforcing filler is added to the mixture obtained in step one at a slow and controlled speed. Subsequently, the dispersion device is continued to be used to disperse at a speed of 1000 rpm to 2000 rpm, and the dispersion time is 15 minutes to 30 minutes. The key of this step is to ensure that the nano-filler can be uniformly dispersed in the resin matrix to form a stable and non-agglomerated nano-composite system. This dispersion process aims to achieve the full disaggregation of the nanoparticles and maximize their reinforcing effect in the polymer matrix. In order to achieve this purpose, the dispersion device can be selected as a high-shear planetary mixer or a high-speed disperser equipped with a special structure dispersion disc.

[0031] Step three: Rheological control agent activation, the rheological control agent is added to the nano-composite mixture obtained in step two. Then, the mixture is stirred at a low speed (for example, 500 rpm to 1000 rpm) for 10 minutes to 20 minutes. In this stage, the material temperature can be optionally increased to 50°C to 60°C according to the characteristics of the rheological control agent, in order to promote the full activation of the rheological control agent and form the ideal thixotropic network structure in the system. Subsequently, the stirring speed is reduced to a low speed (for example, 100 rpm to 300 rpm) at the same temperature, and the stirring is continued for 10 minutes to ensure the full construction and stabilization of the rheological control network, while helping to eliminate the possible existence of small bubbles in the system.

[0032] Step four: Defoaming, the mixed coating material obtained above is transferred to a vacuum defoaming kettle for vacuum defoaming treatment. The vacuum degree is controlled in the range of -0.08 MPa to -0.09 MPa, and the defoaming time is 15 minutes to 30 minutes. The process continues until no visible bubbles exist in the system, thereby ensuring that the quality and appearance of the final coating film meet the requirements.

[0033] Step five: mixing of the curing agent components, the primary curing agent and the secondary curing agent are precisely measured according to the preset mass ratio, and are thoroughly premixed in a separate mixing container to form a uniform multi-stage synergistic curing agent system. This premixing step is designed to ensure the high uniformity of the curing agent components and prevent any unwanted premature reaction before mixing with the coating base.

[0034] Step six: metering, dispensing and packaging, the coating base obtained after step four (usually labeled as component A) and the curing agent system obtained after step five (usually labeled as component B) are precisely measured and dispensed into clean, dry and sealed containers. After dispensing is completed, the product is sealed and packaged for storage and transportation. At the construction site, components A and B will be mixed according to the specified ratio before use. The dispensing process is carried out in a dry and clean environment to strictly prevent the product from absorbing moisture or being contaminated externally.

[0035] Based on the above, the present application is experimentally demonstrated, first experiment group, the solvent-free environmental protection type coating of experiment group is prepared according to the following mass fraction ratio: Reactive oligomer: 45 parts (polyol polyether type epoxy oligomer, EEW 120 g / eq, viscosity 400 mPa·s at 25℃) Toughening modified resin: 20 parts (polyurethane modified epoxy resin, Tg-15℃, EEW 550 g / eq) Base epoxy resin: 35 parts (bisphenol A type epoxy resin, EEW 190 g / eq, viscosity 8000 mPa·s at 25℃) Multi-stage synergistic curing agent system: 25 parts Primary curing agent: 18 parts (aliphatic amine modified epoxy resin curing agent, amine value 320 mgKOH / g, AHEW 85 g / eq, viscosity 600 mPa·s at 25℃) Secondary curing agent: 7 parts (2-methylimidazole, 1.5% of the total mass of the epoxy component) Interface enhanced coupling agent: 1.5 parts (γ-glycidyl ether oxypropyl trimethoxysilane) Inorganic nano-enhanced filler: 10 parts (surface modified nano-silica, average particle size 30 nm) Rheology control agent: 1 part (polyamide wax based thixotropic agent, specific surface area 200 m² / g) Defoaming agent: 0.3 parts (silicone-based non-ionic defoaming agent, surface tension 22 mN / m) Dispersant: 0.5 parts (high molecular polymer dispersant, 0.8% of the total mass of pigments and fillers) Pigment: 15 parts (titanium dioxide, average particle size 0.3 μm) Functional fillers: 10 parts (precipitated barium sulfate, average particle size 5 μm) The preparation method flow is as follows: 1. Pre-dispersion preparation: In a jacketed mixing kettle, add base epoxy resin, reactive oligomer, toughening modifier resin, coupling agent, dispersant, defoamer, titanium white and precipitated barium sulfate. Turn on the high-speed disperser, set the speed to 2000 rpm, and disperse for 45 minutes. Control the material temperature at 38°C by circulating cooling water through the jacket. The fineness is 15 μm as detected by a doctor blade fineness gauge.

[0036] 2. Nano-filler compounding: Slowly add surface-modified nano-silica to the above mixture, and continue to disperse at 1500 rpm for 20 minutes.

[0037] 3. Rheology control agent activation: Add polyamide wax-based thixotropic agent, stir at 800 rpm for 15 minutes, and then stir at 200 rpm for 10 minutes.

[0038] 4. Defoaming: Transfer the coating base to a vacuum defoaming kettle, and defoam at a vacuum degree of -0.085 MPa for 20 minutes.

[0039] 5. Mixing of curing agent components: Premix the primary curing agent and 2-methylimidazole in proportion as component B.

[0040] 6. Metering, dispensing and packaging: Meter and dispense components A (coating base) and B (curing agent system) separately, and store in a sealed manner.

[0041] Test results: After mixing components A and B in a mass ratio of 100:25, apply them to a sandblasted carbon steel plate, and the coating thickness is 200 μm. After curing for 7 days at 25°C and a relative humidity of 60%, perform performance testing, and the results are as follows: ① VOC content: <1 g / L (determined by gas chromatography-mass spectrometry); ② Viscosity at 25°C: 800 mPa·s (Brookfield viscometer, speed 50 rpm); ③ Dry to touch time: 4 hours; ④ Dry to hard time: 24 hours (complete drying, determined by a hardness tester); ⑤ Pencil hardness: 2H (Mitsubishi pencil hardness tester); ⑥ Adhesion (crosshatch method): 0 grade; ⑦ Impact strength: 50 kg·cm; ⑧ Bending test (axle rod diameter): Φ5 mm; ⑨ Salt spray resistance: 500 hours.

[0042] Comparative group: The paint of the comparative group was prepared according to the following mass ratio: ① Epoxy resin: 80 parts (bisphenol A type epoxy resin, EEW 190 g / eq, viscosity 12000 mPa·s at 25℃); ② Solvent: 10 parts (xylene); ③ Curing agent: 20 parts (aliphatic amine curing agent, amine value 300 mgKOH / g, AHEW 90 g / eq, viscosity 800 mPa·s at 25℃); ④ Filler: 20 parts (calcium carbonate, average particle size 10 μm); ⑤ Pigment: 10 parts (titanium dioxide, average particle size 0.3 μm); ⑥ Dispersant: 0.5 parts (traditional wet dispersant); ⑦ Defoaming agent: 0.3 parts (silicone defoaming agent); ⑧ Rheological agent: 0.5 parts (traditional rheological agent).

[0043] The preparation method is as follows: 1. In a batching kettle, add epoxy resin, xylene, dispersant, defoaming agent, pigment and filler. Disperse with a high-speed disperser at 2500 rpm for 45 minutes, and the fineness is 25 μm.

[0044] 2. Add rheological agent and stir at low speed for 10 minutes.

[0045] 3. Defoaming: defoam under a vacuum degree of -0.07 MPa for 15 minutes.

[0046] 4. The curing agent is separately packaged.

[0047] Test results: After mixing the A and B components uniformly in a mass ratio of 100:20, they were coated on a carbon steel plate with a coating thickness of 200 μm. After curing for 7 days at 25℃ and a relative humidity of 60%, the performance tests were carried out, and the results are as follows: ① VOCs content: about 150 g / L (detection); ② Viscosity at 25℃: 1500 mPa·s; ③ Tack-free time: 6 hours; ④ Dry time: 48 hours; ⑤ Pencil hardness: H; ⑥ Adhesion (crosshatch method): level 1; ⑦ Impact strength: 20 kg·cm; ⑧ Bending test (axle rod diameter): Φ10 mm; ⑨ Salt spray resistance: 200 hours (with a small amount of rust).

[0048] For more intuitive comparison, see the following table:

[0049] Experimental results: 1. The solvent-free environmentally friendly coating provided by the present application presents an extremely low level of VOCs emissions, which is superior to traditional solvent-containing coatings. At the same time, although the present application is a solvent-free system, its application viscosity is lower than that of traditional solvent-containing coatings, indicating that it has more excellent flowability and application adaptability.

[0050] 2. In terms of curing speed, the tack-free time and dry time of the present application are shortened, improving the construction efficiency. In addition, in terms of the comprehensive mechanical properties of the coating film, the pencil hardness, adhesion, impact strength and bending toughness of the coating of the present application are superior to those of the comparative group, which confirms the synergistic effect of the multi-stage synergistic curing agent system, the toughening modified resin and the inorganic nano-enhancing filler.

[0051] 3. The coating of the present application exhibits longer protection time and lower corrosion signs in salt spray resistance performance test, indicating that it has advantages in durability, proving the comprehensive improvement of the present application in environmental protection, construction, mechanical properties and durability, overcoming the inherent defects of the existing solvent-free coating.

[0052] Although embodiments of the present application have been shown and described, it will be understood by those having ordinary skill in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A solvent-free environmentally friendly paint, characterized by, The components include the following mass fractions: 30-60 parts of reactive oligomer, 10-30 parts of toughening modified resin, 20-40 parts of base epoxy resin, 15-35 parts of multi-stage synergistic curing agent system, 0.5-3 parts of interfacial reinforcing coupling agent, 5-15 parts of inorganic nano-reinforcing filler, 0.5-2 parts of rheological control agent, 0.1-0.5 parts of defoaming agent, 0.2-1 parts of dispersant, and 0-30 parts of pigment and / or functional filler.

2. The solvent-free environment-friendly coating according to claim 1, characterized in that: The reactive oligomer is a polyol polyether type epoxy oligomer having at least three epoxy groups, an epoxy equivalent weight of 90 g / eq to 150 g / eq, a viscosity at 25°C of .

3. The solvent-free environment-friendly coating according to claim 1, characterized in that: The toughening modified resin is a polyurethane modified epoxy resin or a core-shell structure elastomer modified epoxy resin, the glass transition temperature of the polyurethane modified epoxy resin is -30-0℃, and the epoxy equivalent weight is 400-700 g / eq; the average particle size of the elastomer particles in the core-shell structure elastomer modified epoxy resin is 50-200 nm, and the glass transition temperature is lower than -40℃.

4. The solvent-free environment-friendly coating according to claim 1, characterized in that: The base epoxy resin is a bisphenol A epoxy resin or a bisphenol F epoxy resin having an epoxy equivalent weight of 170 g / eq to 250 g / eq and a viscosity at 25 °C of .

5. The solvent-free environmentally friendly coating of claim 1, wherein: The multi-stage synergistic curing agent system comprises 10 to 25 parts of a primary curing agent and 5 to 10 parts of a secondary curing agent, the primary curing agent is a fatty amine modified epoxy resin curing agent, the amine value is 200 mgKOH / g to 400 mgKOH / g, the hydrogen active equivalent is 50 g / eq to 120 g / eq, the viscosity at 25°C is less than , and the secondary curing agent is a latent curing agent selected from an imidazole derivative or a hindered amine compound.

6. The solvent-free environmentally friendly coating of claim 1, wherein: The interfacial reinforcing coupling agent is an organosilane coupling agent containing epoxy groups or amine groups, the inorganic nano-reinforcing filler is nano-silica or nano-alumina with surface organic modification, and the average particle size is 10-50 nm.

7. The solvent-free environmentally friendly coating of claim 1, wherein: The rheological control agent is a thixotropic agent based on polyamide wax or hydrogenated castor oil derivative, the specific surface area is 100-300 m² / g, and the defoaming agent is an organosilicon or polyether nonionic defoaming agent with a surface tension of less than 25 mN / m. 8.The solvent-free environment-friendly coating of claim 1, characterized in that: The dispersant is a high molecular polymer dispersant, the pigment is an inorganic pigment or an organic pigment with an average particle size of 0.1-5 μm, and the functional filler is selected from precipitated barium sulfate, talc powder, mica powder or glass beads with an average particle size of 1-20 μm.

9. A process for preparing a solvent-free environmentally friendly coating according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1: Pre-dispersion preparation, adding base epoxy resin, reactive oligomer, toughening modified resin, interfacial reinforcing coupling agent, dispersant, defoaming agent, and pigment and / or functional filler in a batching kettle, dispersing at 1500-3000 rpm for 30-60 minutes, controlling the temperature at 30-45℃, and making the fineness reach below 20 μm; S2: Nano-filler compounding, adding inorganic nano-reinforcing filler to the mixture of step one, dispersing at 1000-2000 rpm for 15-30 minutes; S3: Rheological control agent activation, adding rheological control agent, stirring at 500-1000 rpm for 10-20 minutes, and heating to 50-60℃, then stirring at 100-300 rpm for 10 minutes; S4: Defoaming, defoaming at a vacuum degree of -0.08 to -0.09 MPa for 15-30 minutes; S5: Mixing of curing agent components, uniformly premixing the primary and secondary curing agents in proportion; S6: Metering, dispensing and packaging, metering and dispensing the coating binder and curing agent system respectively and sealing. 10.The method for preparing a solvent-free environmentally friendly coating according to claim 9, characterized in that: The high-speed disperser is used in S1, a rotational speed control system and temperature monitoring function are configured, and the dispersing equipment in S2 is a high-shear planetary mixer or a high-speed disperser with a special structure dispersing disc.

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