Water-based two-component polyurethane finish for seawater desalination pipelines and preparation method thereof

Abstract

This invention relates to the field of coating technology, and in particular to a water-based two-component polyurethane topcoat for seawater desalination pipelines and its preparation method. This invention, through the compounding of a specific resin system, the introduction of functional fillers, and the modification of the curing agent, enables the topcoat to exhibit excellent adhesion, seawater corrosion resistance, weather resistance, and abrasion resistance on the surface of wound membrane shell pipelines, while also exhibiting extremely low VOC content and excellent environmental performance. It solves the technical problem that existing technologies still have shortcomings in adhesion, long-term seawater corrosion resistance, and weather resistance on wound membrane shell substrates, making it difficult to meet the long-term design service life requirements of seawater desalination pipelines.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a water-based two-component polyurethane topcoat for seawater desalination pipelines and its preparation method. Background Technology

[0002] Seawater desalination is an important way to solve the global shortage of freshwater resources. Seawater desalination pipeline systems are in a marine environment with high salt spray, high humidity, strong ultraviolet radiation and drastic temperature changes for a long time, which puts extremely high requirements on the corrosion resistance, weather resistance, adhesion and wear resistance of the anti-corrosion coating on the outer wall of the pipeline.

[0003] Spiral wound membrane pipes (also known as fiberglass spiral wound pipes) are composite pipes made of glass fiber reinforced resin as the matrix material through a spiral winding process. Due to their advantages such as lightweight, high strength, and corrosion resistance, they are increasingly widely used in seawater desalination projects. However, spiral wound membrane pipes have low surface energy and weak polarity, resulting in poor adhesion of conventional coatings and a tendency for problems such as coating peeling and blistering.

[0004] Currently, solvent-based coatings are still the main type of paint used for seawater desalination pipelines. These coatings have high VOC (volatile organic compound) content, causing serious environmental pollution and failing to meet increasingly stringent environmental regulations. Although there have been some reports of water-based two-component polyurethane topcoats being used in outdoor pipelines, existing products still have shortcomings in terms of adhesion to the membrane substrate, long-term seawater corrosion resistance, and weather resistance, making it difficult to meet the long-term design service life requirements of seawater desalination pipelines. Summary of the Invention

[0005] The purpose of this invention is to provide a water-based two-component polyurethane topcoat for seawater desalination pipelines and its preparation method, which solves the technical problems in the prior art that are still insufficient in terms of adhesion, long-term seawater corrosion resistance and weather resistance on the wound film substrate, making it difficult to meet the requirements of the long-term design service life of seawater desalination pipelines.

[0006] To achieve the above objectives, the present invention provides a water-based two-component polyurethane topcoat for seawater desalination pipelines, comprising component A and component B, wherein component A comprises the following raw materials in parts by weight: The composition includes: 30-50 parts of waterborne hydroxyl acrylic resin, 10-25 parts of waterborne polyurethane dispersion, 10-20 parts of deionized water, 15-25 parts of rutile titanium dioxide, 5-15 parts of modified glass flakes, 1-5 parts of nano silica, 0.5-2 parts of dispersant, 0.2-0.8 parts of defoamer, 0.3-1 part of substrate wetting agent, 2-6 parts of film-forming aid, 0.3-1.5 parts of thickener, 0.1-0.5 parts of pH adjuster, 1-3 parts of silane coupling agent, 0.5-1.5 parts of ultraviolet absorber, and 0.3-1 part of leveling agent. Component B comprises the following raw materials by weight: 60-80 parts of water-based isocyanate curing agent, 10-25 parts of modified polyurethane curing agent, and 5-15 parts of cosolvent; The mass ratio of component A to component B is 3-6:1.

[0007] The waterborne hydroxyl acrylic resin has a hydroxyl content of 2.5%-4.5%, a glass transition temperature of 20-50℃, and a solid content of 40%-50%. The waterborne polyurethane dispersion is an aliphatic polyester-type waterborne polyurethane dispersion with a solid content of 35%-45%. The modified glass flakes are glass flakes surface-treated with silane coupling agent, with a particle size of 5-300 μm and a thickness of 1-5 μm.

[0008] The nano-silica is fumed silica with a particle size of 10-50 nm. The nanofiller can fill the micropores of the coating, improving the coating's density and wear resistance; The dispersant is a polymeric dispersant.

[0009] The defoamer is a polyether-modified silicone defoamer. The substrate wetting agent is a polyether-modified polysiloxane wetting agent; The film-forming aid is dipropylene glycol butyl ether and / or dipropylene glycol methyl ether.

[0010] The thickener is a polyurethane associative thickener. The pH adjuster is an organic amine pH adjuster; The silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560) and / or γ-aminopropyltriethoxysilane (KH-550).

[0011] The ultraviolet absorber is a benzotriazole ultraviolet absorber; The leveling agent is polyether-modified polydimethylsiloxane; The waterborne isocyanate curing agent is a hydrophilic modified aliphatic polyisocyanate with an NCO content of 15%-22%.

[0012] The modified polyurethane curing agent contains -NCO groups and epoxy functional groups; the -NCO groups in the modified polyurethane curing agent react with the hydroxyl resin in component A to form a polyurethane crosslinking network; The co-solvent is propylene glycol methyl ether acetate and / or diethylene glycol butyl ether acetate.

[0013] This invention also provides a preparation method for preparing the water-based two-component polyurethane topcoat for seawater desalination pipelines as described above. include: Add deionized water, dispersant, defoamer and pH adjuster to the dispersion vessel according to the formula, and stir at 300-500 r / min for 5-10 min until the mixture is uniform. Under stirring conditions, slowly add rutile titanium dioxide, modified glass flakes and nano silica. After the addition is complete, increase the rotation speed to 1200-1800 r / min and disperse at high speed for 30-60 min until the fineness is ≤30μm. Reduce the rotation speed to 500-800 r / min, add the water-based hydroxyl acrylic resin and water-based polyurethane dispersion in sequence, and stir for 15-30 min; Add substrate wetting agent, film-forming aid, silane coupling agent, ultraviolet absorber, leveling agent and thickener, continue stirring for 20-40 minutes, adjust pH to 7.5-8.5, filter and discharge to obtain component A; Under nitrogen protection, water-based isocyanate curing agent, modified polyurethane curing agent and co-solvent are added to the reactor and stirred at 400-600 r / min for 20-40 min until uniformly mixed. The mixture is then filtered out to obtain component B. When using, mix component A and component B at a mass ratio of 3-6:1 until homogeneous, and allow to mature for 10-20 minutes before application.

[0014] This invention relates to a water-based two-component polyurethane topcoat for seawater desalination pipelines and its preparation method. This invention has the following beneficial effects: 1. Excellent adhesion: This invention, through the synergistic compounding of waterborne hydroxyl acrylic resin and waterborne polyurethane dispersion, combined with a modified polyurethane curing agent containing epoxy silane functional groups, forms a strong chemical bond and physical anchoring effect on the low surface energy substrate of the wound membrane pipe, with an adhesion of up to 5MPa (cross-cut test rating ≤ 1), completely solving the problem of easy peeling of the coating of the wound membrane pipe.

[0015] 2. Excellent resistance to seawater corrosion: The layered shielding effect of modified glass flakes and the microporous filling effect of nano-silica work synergistically, combined with the Si-O-Si hydrophobic network, to form multiple protective barriers, which can effectively block the penetration of corrosive media such as Cl⁻ and water molecules, and the salt spray resistance can reach more than 3000h.

[0016] 3. Excellent weather resistance: The aliphatic polyurethane system gives the coating excellent resistance to ultraviolet aging. Combined with the synergistic effect of ultraviolet absorbers, the gloss retention rate is ≥85% after 1500h of artificial accelerated aging test.

[0017] 4. Good wear resistance: The introduction of nano-silica significantly improves the hardness and wear resistance of the coating. The wear resistance (1000g / 1000r) is ≤20mg, which meets the wear resistance requirements of seawater desalination pipelines during transportation, installation and service.

[0018] 5. Green and environmentally friendly: Water is used as the dispersion medium, and the VOC content is ≤80g / L, which meets the requirements of national environmental protection coating standards. The construction process is non-toxic, harmless, non-flammable and non-explosive.

[0019] 6. Good construction adaptability: The product has a long application period (≥4h) and can be applied by various construction methods such as spraying, brushing, and rolling. It has a wide construction window and is suitable for outdoor on-site construction. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0021] Figure 1 This is a schematic diagram of the performance test results of Embodiments 1-2 of the present invention, compared with those of the comparative examples. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0023] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the performance test results of Embodiments 1-2 and the comparative example of the present invention. The present invention provides a water-based two-component polyurethane topcoat for seawater desalination pipelines, comprising component A and component B. Component A comprises the following raw materials by weight: The composition includes: 30-50 parts of waterborne hydroxyl acrylic resin, 10-25 parts of waterborne polyurethane dispersion, 10-20 parts of deionized water, 15-25 parts of rutile titanium dioxide, 5-15 parts of modified glass flakes, 1-5 parts of nano silica, 0.5-2 parts of dispersant, 0.2-0.8 parts of defoamer, 0.3-1 part of substrate wetting agent, 2-6 parts of film-forming aid, 0.3-1.5 parts of thickener, 0.1-0.5 parts of pH adjuster, 1-3 parts of silane coupling agent, 0.5-1.5 parts of ultraviolet absorber, and 0.3-1 part of leveling agent. Component B comprises the following raw materials by weight: 60-80 parts of water-based isocyanate curing agent, 10-25 parts of modified polyurethane curing agent, and 5-15 parts of cosolvent; The mass ratio of component A to component B is 3-6:1.

[0024] The waterborne hydroxyl acrylic resin has a hydroxyl content of 2.5%-4.5%, a glass transition temperature of 20-50℃, and a solid content of 40%-50%. The waterborne polyurethane dispersion is an aliphatic polyester-type waterborne polyurethane dispersion with a solid content of 35%-45%. The modified glass flakes are glass flakes surface-treated with silane coupling agent, with a particle size of 5-300 μm and a thickness of 1-5 μm.

[0025] The nano-silica is fumed silica with a particle size of 10-50 nm. The nanofiller can fill the micropores of the coating, improving the coating's density and wear resistance; The dispersant is a polymeric dispersant.

[0026] The defoamer is a polyether-modified silicone defoamer. The substrate wetting agent is a polyether-modified polysiloxane wetting agent; The film-forming aid is dipropylene glycol butyl ether and / or dipropylene glycol methyl ether.

[0027] The thickener is a polyurethane associative thickener. The pH adjuster is an organic amine pH adjuster; The silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560) and / or γ-aminopropyltriethoxysilane (KH-550).

[0028] The ultraviolet absorber is a benzotriazole ultraviolet absorber; The leveling agent is polyether-modified polydimethylsiloxane; The waterborne isocyanate curing agent is a hydrophilic modified aliphatic polyisocyanate with an NCO content of 15%-22%.

[0029] The modified polyurethane curing agent contains -NCO groups and epoxy functional groups; the -NCO groups in the modified polyurethane curing agent react with the hydroxyl resin in component A to form a polyurethane crosslinking network; The co-solvent is propylene glycol methyl ether acetate and / or diethylene glycol butyl ether acetate.

[0030] This invention also provides a preparation method for preparing the water-based two-component polyurethane topcoat for seawater desalination pipelines as described above. include: Add deionized water, dispersant, defoamer and pH adjuster to the dispersion vessel according to the formula, and stir at 300-500 r / min for 5-10 min until the mixture is uniform. Under stirring conditions, slowly add rutile titanium dioxide, modified glass flakes and nano silica. After the addition is complete, increase the rotation speed to 1200-1800 r / min and disperse at high speed for 30-60 min until the fineness is ≤30μm. Reduce the rotation speed to 500-800 r / min, add the water-based hydroxyl acrylic resin and water-based polyurethane dispersion in sequence, and stir for 15-30 min; Add substrate wetting agent, film-forming aid, silane coupling agent, ultraviolet absorber, leveling agent and thickener, continue stirring for 20-40 minutes, adjust pH to 7.5-8.5, filter and discharge to obtain component A; Under nitrogen protection, water-based isocyanate curing agent, modified polyurethane curing agent and co-solvent are added to the reactor and stirred at 400-600 r / min for 20-40 min until uniformly mixed. The mixture is then filtered out to obtain component B. When using, mix component A and component B at a mass ratio of 3-6:1 until homogeneous, and allow to mature for 10-20 minutes before application.

[0031] Example 1; In this embodiment, the mass ratio of component A to component B is 5:1.

[0032] Component A comprises: 40 parts of waterborne hydroxyl acrylic resin (hydroxyl content 3.5%, Tg 35℃, solid content 45%); 15 parts of waterborne polyurethane dispersion (aliphatic polyester type, solid content 40%); 15 parts of deionized water; 20 parts of rutile titanium dioxide; 10 parts of modified glass flakes (KH-560 treated, particle size 100-200μm); 3 parts of nano silica (gas phase method, particle size 20nm); 1 part of dispersant; 0.4 parts of defoamer; 0.5 parts of substrate wetting agent; 4 parts of film-forming aid (dipropylene glycol butyl ether); 0.8 parts of thickener; 0.3 parts of pH adjuster; 2 parts of silane coupling agent (KH-560); 1 part of ultraviolet absorber; and 0.5 parts of leveling agent.

[0033] Component B comprises: 70 parts of waterborne isocyanate curing agent (18% NCO content); 15 parts of modified polyurethane curing agent (containing -NCO and alkoxysilane functional groups); and 15 parts of cosolvent (propylene glycol methyl ether acetate).

[0034] The preparation method is the same as the steps described above. The properties of the obtained topcoat are as follows: adhesion (cross-cut test) grade 0; salt spray resistance (5% NaCl, 35℃) for 3000h without bubbling or peeling; gloss retention rate of 88% after 1500h of artificial accelerated aging; abrasion resistance (1000g / 1000r) 18mg; VOC content 72g / L.

[0035] Example 2; In this embodiment, the mass ratio of component A to component B is 5:1.

[0036] Component A comprises: 45 parts of waterborne hydroxyl acrylic resin (hydroxyl content 4.0%, Tg 30℃, solid content 45%); 12 parts of waterborne polyurethane dispersion (aliphatic polyester type, solid content 40%); 12 parts of deionized water; 18 parts of rutile titanium dioxide; 12 parts of modified glass flakes (KH-550 treated, particle size 50-150μm); 4 parts of nano silica (gas phase method, particle size 15nm); 1.2 parts of dispersant; 0.5 parts of defoamer; 0.6 parts of substrate wetting agent; 5 parts of film-forming aid (dipropylene glycol methyl ether); 1 part of thickener; 0.3 parts of pH adjuster; 2.5 parts of silane coupling agent (KH-550); 1.2 parts of ultraviolet absorber; and 0.6 parts of leveling agent.

[0037] Component B comprises: 75 parts of waterborne isocyanate curing agent (NCO content 20%); 12 parts of modified polyurethane curing agent; and 13 parts of cosolvent (diethylene glycol butyl ether acetate).

[0038] Comparative Example: A commercially available two-component water-based topcoat for outdoor pipes was used as a control. Coating tests were conducted on the same spiral wound pipe substrate. The results showed that the comparative example coating had an adhesion level of 2 and blistering occurred after only 1000 hours of salt spray resistance. In contrast, Examples 1-2 of this invention achieved adhesion levels of 0-1 and salt spray resistance exceeding 2500 hours, demonstrating significantly superior overall performance compared to existing products.

[0039] Working principle: The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A water-based two-component polyurethane topcoat for seawater desalination pipelines, characterized in that, It includes component A and component B, wherein component A comprises the following raw materials in parts by weight: The composition includes: 30-50 parts of waterborne hydroxyl acrylic resin, 10-25 parts of waterborne polyurethane dispersion, 10-20 parts of deionized water, 15-25 parts of rutile titanium dioxide, 5-15 parts of modified glass flakes, 1-5 parts of nano silica, 0.5-2 parts of dispersant, 0.2-0.8 parts of defoamer, 0.3-1 part of substrate wetting agent, 2-6 parts of film-forming aid, 0.3-1.5 parts of thickener, 0.1-0.5 parts of pH adjuster, 1-3 parts of silane coupling agent, 0.5-1.5 parts of ultraviolet absorber, and 0.3-1 part of leveling agent. Component B comprises the following raw materials by weight: 60-80 parts of waterborne isocyanate curing agent, 10-25 parts of modified polyurethane curing agent, and 5-15 parts of cosolvent; The mass ratio of component A to component B is 3-6:

1.

2. The water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 1, characterized in that, The waterborne hydroxyl acrylic resin has a hydroxyl content of 2.5%-4.5%, a glass transition temperature of 20-50℃, and a solid content of 40%-50%. The waterborne polyurethane dispersion is an aliphatic polyester-type waterborne polyurethane dispersion with a solid content of 35%-45%. The modified glass flakes are glass flakes surface-treated with silane coupling agent, with a particle size of 5-300 μm and a thickness of 1-5 μm.

3. The water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 2, characterized in that, The nano-silica is fumed nano-silica with a particle size of 10-50 nm. The nanofiller can fill the micropores of the coating, improving the density and wear resistance of the coating; The dispersant is a polymeric dispersant.

4. The water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 3, characterized in that, The defoamer is a polyether-modified silicone defoamer; The substrate wetting agent is a polyether-modified polysiloxane wetting agent; The film-forming aid is dipropylene glycol butyl ether and / or dipropylene glycol methyl ether.

5. The water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 4, characterized in that, The thickener is a polyurethane associative thickener; The pH adjuster is an organic amine pH adjuster; The silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560) and / or γ-aminopropyltriethoxysilane (KH-550).

6. The water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 5, characterized in that, The ultraviolet absorber is a benzotriazole ultraviolet absorber; The leveling agent is polyether-modified polydimethylsiloxane; The waterborne isocyanate curing agent is a hydrophilic modified aliphatic polyisocyanate with an NCO content of 15%-22%.

7. The water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 6 and its preparation method, characterized in that, The modified polyurethane curing agent contains -NCO groups and epoxy functional groups; the -NCO groups in the modified polyurethane curing agent react with the hydroxyl resin in component A to form a polyurethane crosslinking network; The co-solvent is propylene glycol methyl ether acetate and / or diethylene glycol butyl ether acetate.

8. A preparation method for preparing the water-based two-component polyurethane topcoat for seawater desalination pipelines as described in claim 7, characterized in that, include: Add deionized water, dispersant, defoamer and pH adjuster to the dispersion vessel according to the formula, and stir at 300-500 r / min for 5-10 min until the mixture is uniform. Under stirring conditions, slowly add rutile titanium dioxide, modified glass flakes and nano silica. After the addition is complete, increase the rotation speed to 1200-1800 r / min and disperse at high speed for 30-60 min until the fineness is ≤30μm. Reduce the rotation speed to 500-800 r / min, add the water-based hydroxyl acrylic resin and water-based polyurethane dispersion in sequence, and stir for 15-30 min; Add substrate wetting agent, film-forming aid, silane coupling agent, ultraviolet absorber, leveling agent and thickener, continue stirring for 20-40 minutes, adjust pH to 7.5-8.5, filter and discharge to obtain component A; Under nitrogen protection, water-based isocyanate curing agent, modified polyurethane curing agent and co-solvent are added to the reactor and stirred at 400-600 r / min for 20-40 min until uniformly mixed. The mixture is then filtered out to obtain component B. When using, mix component A and component B at a mass ratio of 3-6:1 until homogeneous, and allow to mature for 10-20 minutes before application.

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